AUGMENTED REALITY
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shibin.sree
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16-12-2009, 04:58 PM


[/size][/font][font=Times New Roman][size=medium] Technology has advanced to the point where realism in virtual reality is very achievable. However, in our obsession to reproduce the world and human experience in virtual space, we overlook the most important aspects of what makes us who we are”our reality. One must capture the imagination in order to create truly compelling experiences.Augmented reality will truly change the way we view the world. Picture yourself walking or driving down the street. With augmented-reality displays, which will eventually look much like a normal pair of glasses, informative graphics will appear in your field of view and audio will coincide with whatever you see.


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AUGMENTED REALITY
A B S T R A C T
Augmented reality adds information and meaning to a real object or place. Unlike virtual reality, augmented reality does not create a simulated reality. Instead, it takes a real object or space and uses technologies to add contextual data to deepen understanding of it. This paper surveys the field of Augmented Reality, in which 3-D virtual objects are integrated into a real environment in real time. It describes the medical, manufacturing, visualization, entertainment and military applications that have been explored. This paper describes the characteristics of Augmented Reality systems, including a brief discussion of the tradeoffs between optical and video blending approaches. Registration and sensing errors are two of the biggest problems in building effective Augmented Reality systems, so this paper summarizes current efforts to overcome these problems. Future directions and areas requiring further research are discussed. On the spectrum between virtual reality, which creates immersible, computer-generated environments, and the real world, augmented reality is closer to the real world. Augmented reality adds graphics, sounds, haptics and smell to the natural world as it exists. You can expect video games to drive the development of augmented reality, but this technology will have countless applications. Everyone from tourists to military troops will benefit from the ability to place computer-generated graphics in their field of vision.
Name : Suryendu sangam Samal
Regd. : 0601289094
A Seminar Report for the Final Review On AUGMENTED REALITY
No: 0601289086
7th Semester
I N T R O D U C T I O N
This paper describes the current state-of-the-art in Augmented Reality. It describes work performed at many different sites and explains the issues and problems encountered when building Augmented Reality systems. It summarizes the tradeoffs and approaches taken so far to overcome these problems and speculates on future directions that deserve exploration.Section 1 describes what Augmented Reality is and the motivations for developing this technology. Section 2 discusses the issues involved in building an Augmented Reality system. Currently, two of the biggest problems are in registration and sensing: the subjects of Sections 3 and 4. Section 5 describes the advantage of augmented reality over virtual environment systems . Five classes of potential applications that have been explored are described in Section 6. Finally, Section 7 describes some areas that require further work and research. Augmented reality will truly change the way we view the world. Picture yourself walking or driving down the street. With augmented-reality displays, which will eventually look much like a normal pair of glasses, informative graphics will appear in your field of view, and audio will coincide with whatever you see. These enhancements will be refreshed continually to reflect the movements of your head. In this article, we will take a look at this future technology, its components and how it will be used. Tourists that visit historical sites, such as a Civil War battlefield do not see these locations as they were in the past, due to changes over time. It is often difficult for a modern visitor to imagine what these sites really looked like in the past. A tourist equipped with an outdoors AR system could see a computer-generated version of Living History. Tourists and students walking around the grounds with such AR displays would gain a much better understanding of these historical sites and the important events that took place there. After the basic problems with AR are solved, the ultimate goal will be photorealism has been demonstrated in feature films, but accomplishing this in an interactive application will be much harder.
Augmented Reality :
Augmented Reality (AR) is a variation of Virtual Environments (VE), or Virtual Reality as it is more commonly called. VE technologies completely immerse a user inside a synthetic environment. While immersed, the user cannot see the real world around him. In contrast, AR allows the user to see the real world, with virtual objects superimposed upon or composited with the real world. Therefore, AR supplements reality, rather than completely replacing it. Ideally, it would appear to the user that the virtual and real objects coexisted in the same space, Figure shows an example of what this might look like. All these things are optional also ,i.e. they can be ignored if the user want some specific details rather than details for everything that comes in itâ„¢s way . AR can be thought of as the "middle ground" between VE (completely synthetic) and telepresence (completely real).This survey defines AR as systems that have the following three characteristics:
1) Combines real and virtual
2) Interactive in real time
3) Registered in 3-D

REALITY AUGMENTED REALITY VIRTUAL REALITY
2 DESIGN :
A see-through HMD is one device used to combine real and virtual. Standard closed-view HMDs do not allow any direct view of the real world. In contrast, a seethrough HMD lets the user see the real world, with virtual objects superimposed by optical or video technologies.
2.1 Optical see-through HMD :
Optical see-through HMDs work by placing optical combiners in front of the user's eyes. These combiners are partially transmissive, so that the user can look directly through them to see the real world. The combiners are also partially reflective, so that the user sees virtual images bounced off the combiners from head mounted monitors. This approach is similar in nature to Head-Up Displays (HUDs) commonly used in military aircraft, except that the combiners are attached to the head. The optical combiners usually reduce the amount of light that the user sees
from the real world. Since the combiners act like half-silvered mirrors, they only let in some of the light from the real world, so that they can reflect some of the light from the monitors into the user's eyes. Choosing the level of blending is a design problem. More sophisticated combiners might vary the level of contributions based upon the wavelength of light. For example, such a combiner might be set to reflect all light of a certain wavelength and none at any other wavelengths. This would be ideal with a monochrome monitor. Virtually all the light from the monitor would be reflected into the user's eyes, while almost all the light from the real world (except at the particular wavelength) would reach the user's eyes. However, most existing optical see-through HMDs do reduce the amount of light from the real world, so they act like a pair of sunglasses when the power is cut off.

2.2 Video see-through HMD :
Video see-through HMDs work by combining a closed-view HMD with one or two head-mounted video cameras. The video cameras provide the user's view of the real world. Video from these cameras is combined with the graphic images created by the scene generator, blending the real and virtual. The result is sent to the monitors in front of the user's eyes in the closed-view HMD. Figure shows a conceptual diagram of a video see-through HMD. Video composition can be done in more than one way. A simple way is to use chroma-keying, a technique used in many video special effects. The background of the computer graphic images is set to a specific color, say green, which none of the virtual objects use. Then the combining step replaces all green areas with the corresponding parts from the video of the real world. This has the effect of superimposing the virtual objects over the real world. A more sophisticated composition would use depth information. If the system had depth information at each pixel for the real world images, it could combine the real and virtual images by a 12 pixel-by-pixel depth comparison. This would allow real objects to cover virtual objects and vice-versa.

VIDEO SEE-THROUGH HMD CONCEPTUAL DIAGRAM
2.3 Monitor based AR :
AR systems can also be built using monitor-based configurations, instead of see-through HMDs. Figure shows how a monitor-based system might be built. In this case, one or two video cameras view the environment. The cameras may be static or mobile. In the mobile case, the cameras might move around by being attached to a robot, with their locations tracked. The video of the real world and the graphic images generated by a scene generator are combined, just as in the video see-through HMD case, and displayed in a monitor in front of the user. The user does not wear the display device.

MONITOR BASED AR CONCEPTUAL DIAGRAM
2.4 Trade offs between the two approaches :
The rest of this section compares the relative advantages and disadvantages of optical and video approaches, starting with optical. An optical approach has the following advantages over a video approach:
1) Simplicity:
Optical blending is simpler and cheaper than video blending. Optical approaches have only one "stream" of video to worry about: the graphic images. The real world is seen directly through the combiners, and that time delay is generally a few nanoseconds. Video blending, on the other hand, must deal with separate video streams for the real and virtual images. Both streams have inherent delays in the tens of milliseconds. Digitizing video images usually adds at least one frame time of delay to the video stream, where a frame time is how long it takes to completely update an image. A monitor that completely refreshes the screen at 60 Hz has a frame time of 16.67 ms. The two streams of real and virtual images must be properly synchronized or temporal distortion results. Also, optical see-through HMDs with narrow field-of-view combiners offer views of the real world that have little distortion. Video cameras almost always have some amount of distortion that must be compensated for, along with any distortion from the optics in front of the display devices. Since video requires cameras and combiners that optical approaches do not need, video will probably be more expensive and complicated to build than optical-based systems.
2) Resolution:
Video blending limits the resolution of what the user sees, both real and virtual, to the resolution of the display devices. With current displays, this resolution is far less than the resolving power of the fovea. Optical see-through also shows the graphic images at the resolution of the display device, but the user's view of the real world is not degraded. Thus, video reduces the resolution of the real world, while optical see-through does not.
3) Safety:
Video see-through HMDs are essentially modified closed-view HMDs. If the power is cut off, the user is effectively blind. This is a safety concern in some applications. In contrast, when power is removed from an optical seethrough HMD, the user still has a direct view of the real world. The HMD then becomes a pair of heavy sunglasses, but the user can still see.
4) No eye offset:
With video see-through, the user's view of the real world is provided by the video cameras. In essence, this puts his "eyes" where the video cameras are. In most configurations, the cameras are not located exactly where the user's eyes are, creating an offset between the cameras and the real eyes. The distance separating the cameras may also not be exactly the same as the user's interpupillary distance (IPD). This difference between camera locations and eye locations introduces displacements from what the user sees compared to what he expects to see. For example, if the cameras are above the user's eyes, he will see the world from a vantage point slightly taller than he is used to. Video see-through can avoid the eye offset problem through the use of mirrors to create another set of optical paths that mimic the paths directly into the user's eyes. Using those paths, the cameras will see what the user's eyes would normally see without the HMD. However, this adds complexity to the HMD design. Offset is generally not a difficult design problem for optical see-through displays. While the user's eye can rotate with respect to the position of the HMD, the resulting errors are tiny. Using the eye's center of rotation as the viewpoint in the computer graphics model should eliminate any need for eye tracking in an optical see-through HMD.

Video blending offers the following advantages over optical blending:
1) Flexibility in composition strategies:
A basic problem with optical seethrough is that the virtual objects do not completely obscure the real world objects, because the optical combiners allow light from both virtual and real sources. Building an optical see-through HMD that can selectively shut out the light from the real world is difficult. In a normal optical system, the objects are designed to be in focus at only one point in the optical path: the user's eye. Any filter that would selectively block out light must be placed in the optical path at a point where the image is in focus, which obviously cannot be the user's eye. Therefore, the optical system must have two places where the image is in focus: at the user's eye and the point of the hypothetical filter. This makes the optical design much more difficult and complex. No existing optical see-through HMD blocks incoming light in thisfashion. Thus, the virtual objects appear ghost-like and semi-transparent. This damages the illusion of reality because occlusion is one of the strongest depth cues. In contrast, video see-through is far more flexible about how it merges the real and virtual images. Since both the real and virtual are available in digital form, video seethrough compositors can, on a pixel-by-pixel basis, take the real, or the virtual, or some blend between the two to simulate transparency. Because of this flexibility, video see-through may ultimately produce more compelling environments than optical see-through approaches.
2) Wide field-of-view:
Distortions in optical systems are a function of the radial distance away from the optical axis. The further one looks away from the center of the view, the larger the distortions get. A digitized image taken through a distorted optical system can be undistorted by applying image processing techniques to unwrap the image, provided that the optical distortion is well characterized. This requires significant amounts of computation, but this constraint will be less important in the future as computers become faster. It is harder to build wide field-of-view displays with optical see-through techniques. Any distortions of the user's view of the real world must be corrected optically, rather than digitally, because the system has no digitized image of the real world to manipulate. Complex optics are expensive and add weight to the HMD. Wide field-of-view systems are an exception to the general trend of optical approaches being simpler and cheaper than video approaches.
3) Real and virtual view delays can be matched:
Video offers an approach for reducing or avoiding problems caused by temporal mismatches between the real and virtual images. Optical see-through HMDs offer an almost instantaneous view of the real world but a delayed view of the virtual. This temporal mismatch can cause problems. With video approaches, it is possible to delay the video of the real world to match the delay from the virtual image stream.
4) Additional registration strategies:
In optical see-through, the only information the system has about the user's head location comes from the head tracker. Video blending provides another source of information: the digitized image of the real scene. This digitized image means that video approaches can employ additional registration strategies unavailable to optical approaches.
Both optical and video technologies have their roles, and the choice of technology depends on the application requirements. Many of the mechanical assembly and repair prototypes use optical approaches, possibly because of the cost and safety issues. If successful, the equipment would have to be replicated in large numbers to equip workers on a factory floor. In contrast, most of the prototypes for medical applications use video approaches, probably for the flexibility in blending real and virtual and for the additional registration strategies offered.
3 Registration :
3.1 The registration problem
One of the most basic problems currently limiting Augmented Reality applications is the registration problem. The objects in the real and virtual worlds must be properly aligned with respect to each other, or the illusion that the two worlds coexist will be compromised. More seriously, many applications demand accurate registration. For example, recall the needle biopsy application. If the virtual object is not where the real tumor is, the surgeon will miss the tumor and the biopsy will fail. Without accurate registration, Augmented Reality will not be accepted in many applications. For example, a user wearing a closed-view HMD might hold up her real hand and see a virtual hand. This virtual hand should be displayed exactly where she would see her real hand, if she were not wearing an HMD. But if the virtual hand is wrong by five millimeters, she may not detect that unless actively looking for such errors. The same error is much more obvious in a see-through HMD, where the conflict is visual-visual. Furthermore, a phenomenon known as visual capture makes it even more difficult to detect such registration errors. Visual capture is the tendency of the brain to believe what it sees rather than what it feels, hears, etc. That is, visual information tends to override all other senses. When watching a television program, a viewer believes the sounds come from the mouths of the actors on the screen, even though they actually come from a speaker in the TV. Ventriloquism works because of visual capture. Similarly, a user might believe that her hand is where the virtual hand is drawn, rather than where her real hand actually is, because of visual capture. This effect increases the amount of registration error users can tolerate in Virtual Environment systems. If the errors are systematic, users might even be able to adapt to the new environment, given a long exposure time of several hours or days. Augmented Reality demands much more accurate registration than Virtual Environments. Imagine the same scenario of a user holding up her hand, but this time wearing a see-through HMD. Registration errors now result in visual-visual conflicts between the images of the virtual and real hands. Such conflicts are easy to detect because of the resolution of the human eye and the sensitivity of the human visual system to differences. Registration of real and virtual objects is not limited to AR. Special-effects artists seamlessly integrate computer-generated 3-D objects with live actors in film and video. The difference lies in the amount of control available. With film, a director can carefully plan each shot, and artists can spend hours per frame, adjusting each by hand if necessary, to achieve perfect registration. As an interactive medium, AR is far more difficult to work with. The AR system cannot control the motions of the HMD wearer. The user looks where she wants, and the system must respond within tens of milliseconds. Registration errors are difficult to adequately control because of the high accuracy requirements and the numerous sources of error. These sources of error can be divided into two types: static and dynamic. Static errors are the ones that cause registration errors even when the user's viewpoint and the objects in the environment remain completely still. Dynamic errors are the ones that have no effect until either the viewpoint or the objects begin moving. For current HMD-based systems, dynamic errors are by far the largest contributors to registration errors, but static errors cannot be ignored either. The next two sections discuss static and dynamic errors and what has been done to reduce them.
3.1.1 Static errors
The three main sources of static errors are:
3.1.1.1 Distortion in the optics:
Optical distortions exist in most camera and lens systems, both in the cameras that record the real environment and in the optics used for the display. Because distortions are usually a function of the radial distance away from the optical axis, wide field-of-view displays can be especially vulnerable to this error. Near the center of the field-of-view, images are relatively undistorted, but far away from the center, image distortion can be large. For example, straight lines may appear curved. In a see-through HMD with narrow field-of-view displays, the optical combiners add virtually no distortion, so the user's view of the real world is not warped. However, the optics used to focus and magnify the graphic images from the display monitors can introduce distortion. This mapping of distorted virtual images on top of an undistorted view of the real world causes static registration errors. The cameras and displays may also have nonlinear distortions that cause errors. Optical distortions are usually systematic errors, so they can be mapped and compensated. This mapping may not be trivial, but it is often possible. For example,
describes the distortion of one commonly-used set of HMD optics. The distortions might be compensated by additional optics. An alternate approach is to do the compensation digitally. This can be done by image warping techniques, both on the digitized video and the graphic images. Typically, this involves predistorting the images so that they will appear undistorted after being displayed. Digital compensation methods can be computationally expensive, often requiring special hardware to accomplish in real time.
3.1.1.2 Errors in the tracking system:
Errors in the reported outputs from the tracking and sensing systems are often the most serious type of static registration errors. These distortions are not easy to measure and eliminate, because that requires another "3-D ruler" that is more accurate than the tracker being tested. These errors are often non-systematic and difficult to fully characterize. Almost all commercially available tracking systems are not accurate enough to satisfy the requirements of AR systems.
3.1.1.3 Mechanical misalignments:
Mechanical misalignments are discrepancies between the model or specification of the hardware and the actual physical properties of the real system. For example, the combiners, optics, and monitors in an optical see-through HMD may not be at the expected distances or orientations with respect to each other. If the frame is not sufficiently rigid, the various component parts may
change their relative positions as the user moves around, causing errors. Mechanical misalignments can cause subtle changes in the position and orientation of the project and implimentationed virtual images that are difficult to compensate. While some alignment errors can be calibrated, for many others it may be more effective to "build it right" initially.
3.1.2 Dynamic errors :
Dynamic errors occur because of system delays, or lags. The end-to-end system delay is defined as the time difference between the moment that the tracking system measures the position and orientation of the viewpoint to the moment when the generated images corresponding to that position and orientation appear in the displays. These delays exist because each component in an Augmented Reality system requires some time to do its job. The delays in the tracking subsystem, the communication delays, the time it takes the scene generator to draw the appropriate images in the frame buffers, and the scanout time from the frame buffer to the
displays all contribute to end-to-end lag. End-to-end delays of 100 ms are fairly typical on existing systems. Simpler systems can have less delay, but other systems have more. Delays of 250 ms or more can exist on slow, heavily loaded, or networked systems. End-to-end system delays cause registration errors only when motion occurs. Assume that the viewpoint and all objects remain still. Then the lag does not cause registration errors. No matter how long the delay is, the images generated are appropriate, since nothing has moved since the time the tracker measurement was taken. Compare this to the case with motion. For example, assume a user wears a see-through HMD and moves her head. The tracker measures the head at an initial time t. The images corresponding to time t will not appear until some future time t2, because of the end-to-end system delays. During this delay, the user's head remains in motion, so when the images computed at time t finally appear, the user sees them at a different location than the one they were computed for. Thus, the images are incorrect for the time they are actually viewed. To the user, the virtual objects appear to "swim around" and "lag behind" the real objects. This was graphically System delays seriously hurt the illusion that the real and virtual worlds coexist because they cause large registration errors. With a typical end-to-end lag of 100 ms and a moderate head rotation rate of 50 degrees per second, the angular dynamic error is 5 degrees. At a 68 cm arm length, this results in registration errors of almost 60 mm. System delay is the largest single source of registration error in existing AR systems, outweighing all others combined .
3.1.2.1 Reduce system lag:
The most direct approach is simply to reduce, or ideally eliminate, the system delays. If there are no delays, there are no dynamic errors. Unfortunately, modern scene generators are usually built for throughput, not minimal latency. It is sometimes possible to reconfigure the software to sacrifice throughput to minimize latency. For example, the SLATS system completes rendering a pair of interlaced NTSC images in one field time (16.67 ms) on Pixel-Planes. Being careful about synchronizing pipeline tasks can also reduce the end-to-end lag. System delays are not likely to completely disappear anytime soon. Some believe that the current course of technological development will automatically solve this problem. Unfortunately, it is difficult to reduce system delays to the point where they are no longer an issue. Recall that registration errors must be kept to a small fraction of a degree. At the moderate head rotation rate of 50 degrees per second, system lag must be 10 ms or less to keep angular errors below 0.5 degrees. Just scanning out a frame buffer to a display at 60 Hz requires 16.67 ms. It might be possible to build an HMD system with less than 10 ms of lag, but the drastic cut in throughput and the expense required to construct the system would make alternate solutions attractive. Minimizing system delay is important, but reducing delay to the point where it is no longer a source of registration error is not currently practical.
3.1.2.2 Match temporal streams:
In video-based AR systems, the video camera and digitization hardware impose inherent delays on the user's view of the real world. This is potentially a blessing when reducing dynamic errors, because it allows the temporal streams of the real and virtual images to be matched. Additional delay is added to the video from the real world to match the scene generator delays in generating the virtual images. This additional delay to the video stream will probably not remain constant, since the scene generator delay will vary with the complexity of the rendered scene. Therefore, the system must dynamically synchronize the two streams. Note that while this reduces conflicts between the real and virtual, now both the real and virtual objects are delayed in time.
3.1.2.3 Predict:
The last method is to predict the future viewpoint and object locations. If the future locations are known, the scene can be rendered with these future locations, rather than the measured locations. Then when the scene finally appears, the viewpoints and objects have moved to the predicted locations, and the graphic images are correct at the time they are viewed. For short system delays
(under ~80 ms), prediction has been shown to reduce dynamic errors by up to an order of magnitude. Accurate predictions require a system built for realtime measurements and computation. Using inertial sensors makes predictions more accurate by a factor of 2-3. Predictors have been developed for a few AR systems, but the majority were implemented and evaluated with VE systems. More work needs to be done on ways of comparing the theoretical performance of various predictors and in developing prediction models that better match actual head motion .
3.2 Current status :
The registration problem is far from solved. Many systems assume a static viewpoint, static objects, or even both. Even if the viewpoint or objects are allowed to move, they are often restricted in how far they can travel. Registration is shown under controlled circumstances, often with only a small number of real-world objects, or where the objects are already well-known to the system. For example, registration may only work on one object marked with fiducials, and not on any other objects in the scene. Much more work needs to be done to increase the domains in which registration is robust. Duplicating registration methods remains a nontrivial task, due to both the complexity of the methods and the additional hardware required. If simple yet effective solutions could be developed, that would speed the acceptance of AR systems.
4 Sensing :
Accurate registration and positioning of virtual objects in the real environment requires accurate tracking of the user's head and sensing the locations of other objects in the environment. The biggest single obstacle to building effective Augmented Reality systems is the requirement of accurate, long-range sensors and trackers that report the locations of the user and the surrounding objects in the environment. Commercial trackers are aimed at the needs of Virtual Environments and motion capture applications. Compared to those two applications, Augmented Reality has much stricter accuracy requirements and demands larger working volumes. No tracker currently provides high accuracy at long ranges in real time. More work needs to be done to develop sensors and trackers that can meet these stringent requirements. Specifically, AR demands more from trackers and sensors in three areas :
¢ Greater input variety and bandwidth
¢ Higher accuracy
¢ Longer range
4.1 Input variety and bandwidth :
VE systems are primarily built to handle output bandwidth: the images displayed, sounds generated, etc. The input bandwidth is tiny: the locations of the user's head and hands, the outputs from the buttons and other control devices, etc. AR systems, however, will need a greater variety of input sensors and much more input bandwidth. There are a greater variety of possible input sensors than output displays. Outputs are limited to the five human senses. Inputs can come
from anything a sensor can detect. It is speculated that Augmented Reality may be useful in any application that requires displaying information not directly available or detectable by human senses by making that information visible (or audible, touchable, etc.). Other future applications
might use sensors to extend the user's visual range into infrared or ultraviolet frequencies, and remote sensors would let users view objects hidden by walls or hills. Conceptually, anything not detectable by human senses but detectable by machines might be transduced into something that a user can sense in an AR system. Range data is a particular input that is vital for many AR applications. The AR system knows the distance to the virtual objects, because that model is built into the system. But the AR system may not know where all the real objects are in the
environment. The system might assume that the entire environment is measured at the beginning and remains static thereafter. However, some useful applications will require a dynamic environment, in which real objects move, so the objects must be tracked in real time. Thus, a significant modeling effort may be required and should be taken into consideration when building an AR application.
4.2 High accuracy :
The accuracy requirements for the trackers and sensors are driven by the accuracies needed for visual registration, as described in Section 3. For many approaches, the registration is only as accurate as the tracker. Therefore, the AR system needs trackers that are accurate to around a millimeter and a tiny fraction of a degree, across the entire working range of the tracker. Few trackers can meet this specification, and every technology has weaknesses. Some mechanical trackers are accurate enough, although they tether the user to a limited working volume. Magnetic trackers are vulnerable to distortion by metal in the environment, which exists in many desired AR application environments. Ultrasonic trackers suffer from noise and are difficult to make accurate at long ranges because of variations in the ambient temperature. Optical technologies have distortion and calibration problems. Inertial trackers drift with time. Of the
individual technologies, optical technologies show the most promise due to trends toward high-resolution digital cameras, real-time photogrammetric techniques, and structured light sources that result in more signal strength at long distances. Future tracking systems that can meet the stringent requirements of AR will probably be hybrid systems, such as a combination of inertial and optical technologies. Using multiple technologies opens the possibility of covering for each technology's weaknesses by combining their strengths. Attempts have been made to calibrate the distortions in commonly-used magnetic tracking systems. These have succeeded at removing much of the gross error from the tracker at long ranges, but not to the level required by AR systems. For example, mean errors at long ranges can be reduced from several inches to around one inch. The requirements for registering other sensor modes are not nearly as stringent. For example, the human auditory system is not very good at localizing deep bass sounds, which is why subwoofer placement is not critical in a home theater system.
4.3 Long range :
Few trackers are built for accuracy at long ranges, since most VE applications do not require long ranges. Motion capture applications track an actor's body parts to control a computer-animated character or for the analysis of an actor's movements. This is fine for position recovery, but not for orientation. Orientation recovery is based upon the computed positions. Even tiny errors in those positions can cause orientation errors of a few degrees, which is too large for AR systems. A scalable system is one that can be expanded to cover any desired range, simply by adding more modular components to the system. This is done by building a cellular tracking system, where only nearby sources and sensors are used to track a user. As the user walks around, the set of sources and sensors changes, thus achieving large working volumes while avoiding long distances between the current working set of sources and sensors. While scalable trackers can be effective, they are complex and by their very nature have many components,
making them relatively expensive to construct. The Global Positioning System (GPS) is used to track the locations of vehicles almost anywhere on the planet. It might be useful as one part of a long range tracker for AR systems. However, by itself it will not be sufficient. The best reported
accuracy is approximately one centimeter, assuming that many measurements are integrated (so that accuracy is not generated in real time), when GPS is run in differential mode. That is not sufficiently accurate to recover orientation from a set of positions on a user. Tracking an AR system outdoors in real time with the required accuracy has not been demonstrated and remains an open problem.
5 Comparison against virtual environments :
The overall requirements of AR can be summarized by comparing them against the requirements for Virtual Environments, for the three basic subsystems that they require.
5.1 Scene generator:
Rendering is not currently one of the major problems in AR. VE systems have much higher requirements for realistic images because they completely replace the real world with the virtual environment. In AR, the virtual images only supplement the real world. Therefore, fewer virtual objects need to be drawn, and they do not necessarily have to be realistically rendered in order to serve the purposes of the application. For example, in the annotation applications, text and 3-D wireframe drawings might suffice. Ideally, photorealistic graphic objects would be seamlessly merged with the real environment, but more basic problems have to be solved first.
5.2 Display device:
The display devices used in AR may have less stringent requirements than VE systems demand, again because AR does not replace the real world. For example, monochrome displays may be adequate for some AR applications, while virtually all VE systems today use full color. Optical see-through HMDs with a small field-of-view may be satisfactory because the user can still see the real world with his peripheral vision; the see-through HMD does not shut off the
user's normal field-of-view. Furthermore, the resolution of the monitor in an optical see-through HMD might be lower than what a user would tolerate in a VE application, since the optical see-through HMD does not reduce the resolution of the real environment.
5.3 Tracking and sensing:
While in the previous two cases AR had lower requirements than VE, that is not the case for tracking and sensing. In this area, the requirements for AR are much stricter than those for VE systems since it is done in real time.
6 MOTIVATION AND APPLICATIONS :
Why is combining real andvirtual objects in 3-D useful? Augmented Reality enhances a user's perception of and interaction with the real world. The virtual objects display information that the user cannot directly detect with his own senses. It can be otherwise termed as Intelligence Amplification. At least five classes of potential AR applications have been explored: medical visualization, maintenance and repair, annotation, entertainment and military aircraft navigation and targeting. The next section describes work that has been done in each area. While these do not cover every potential application area of this technology, they do cover the areas explored so far.
6.1 Medical
Doctors could use Augmented Reality as a visualization and training aid for surgery. It may be possible to collect 3-D datasets of a patient in real time, using noninvasive sensors like Magnetic Resonance Imaging (MRI), Computed Tomography scans (CT), or ultrasound imaging. These datasets could then be rendered and combined in real time with a view of the real patient. AR technology could provide an internal view without the need for larger incisions. AR might also be helpful for general medical visualization tasks in the surgical room. The information from the non-invasive sensors would be directly displayed on the patient, showing exactly where to perform the operation. AR might also be useful for training purposes. Virtual instructions could remind a novice surgeon of the required steps, without the need to look away from a patient to consult a manual.
6.2 Manufacturing and repair
Another category of Augmented Reality applications is the assembly, maintenance, and repair of complex machinery. Instructions might be easier to understand if they were available, not as manuals with text and pictures, but rather as 3-D drawings superimposed upon the actual equipment, showing step-by-step the tasks that need to be done and how to do them. These superimposed 3-D drawings can be animated, making the directions even more explicit.
6.3 Annotation and visualization
AR could be used to annotate objects and environments with public or private information. Applications using public information assume the availability of public databases to draw upon. For example, a hand-held display could provide information about the contents of library shelves as the user walks around the library A user can point at parts of an engine model and the AR system displays the name of the part that is being pointed at .AR might give architects "X-ray vision" inside a building, showing where the pipes, electric lines, and structural supports are inside the walls. Similarly, virtual lines and objects could aid navigation and scene understanding during poor visibility conditions, such as underwater or in fog.
6.4 Entertainment
In the entertainment field AR has still bigger achievements . The actors stand in front of a large blue screen, while a computer-controlled motion camera records the scene. Since the camera's location is tracked, and the actor's motions are scripted, it is possible to digitally composite the actor into a 3-D virtual background. The entertainment industry sees this as a way to reduce production costs: creating and storing sets virtually is potentially cheaper than constantly building new physical sets from scratch. It can be further enhanced by populating the environment with intelligent virtual creatures that respond to user actions .
6.5 Military aircraft
For many years, military aircraft and helicopters have used Head-Up Displays (HUDs) and Helmet-Mounted Sights (HMS) to superimpose vector graphics upon the pilot's view of the real world. Besides providing basic navigation and flight information, these graphics are sometimes registered with targets in the environment, providing a way to aim the aircraft's weapons. Future generations of combat aircraft will be developed with an HMD built into the pilot's helmet.
7. Future directions
This section identifies areas and approaches that require further research to produce improved AR systems.
7.1 Hybrid approaches:
Future tracking systems may be hybrids, because combining approaches can cover weaknesses. The same may be true for other problems in AR. For example, current registration strategies generally focus on a single strategy. Future systems may be more robust if several techniques are combined. An example is combining vision-based techniques with prediction. If the fiducials are not available, the system switches to open-loop prediction to reduce the registration errors, rather than breaking down completely. The predicted viewpoints in turn produce a more accurate initial location estimate for the vision-based techniques.
7.2 Real-time systems and time-critical computing:
Many VE systems are not truly run in real time. Instead, it is common to build the system, often on UNIX, and then see how fast it runs. This may be sufficient for some VE applications. Since everything is virtual, all the objects are automatically synchronized with each other. AR is a different story. Now the virtual and real must be synchronized, and the real world "runs" in real time. Therefore, effective AR systems must be built with real time performance in mind. Accurate timestamps must be available. Operating systems must not arbitrarily swap out the AR software process at any time, for arbitrary durations. Systems must be built to guarantee completion within specified time budgets, rather than just "running as quickly as possible." These are characteristics of flight simulators and a few VE systems. Constructing and debugging real-time systems is often painful and difficult, but the requirements for AR demand real-time performance.
7.3 Perceptual and psychophysical studies:
Augmented Reality is an area ripe for psychophysical studies. How much lag can a user detect? How much registration error is detectable when the head is moving? Besides questions on perception, psychological experiments that explore performance issues are also needed. How much does head-motion prediction improve user performance on a specific task? How much registration error is tolerable for a specific application before performance on that task degrades substantially? Is the allowable error larger while the user moves her head versus when she stands still? Furthermore, not much is known about potential optical illusions caused by errors or conflicts in the simultaneous display of real and virtual objects. Few experiments in this area have been performed. Jannick Rolland, Frank Biocca and their students conducted a study of the effect caused by eye displacements in video see-through HMDs. They found that users partially adapted to the eye displacement, but they also had negative aftereffects after removing the HMD.
7.4 Portability:
AR requires making the equipment self-contained and portable. Existing tracking technology is not capable of tracking a user outdoors at the required accuracy.
7.5 Multimodal displays:
Almost all work in AR has focused on the visual sense: virtual graphic objects and overlays. But augmentation might apply to all other senses as well. In particular, adding and removing 3-D sound is a capability that could be useful in some AR applications.
7.6 Social and political issues:
Technological issues are not the only ones that need to be considered when building a real application. There are also social and political dimensions when getting new technologies into the hands of real users. Sometimes, perception is what counts, even if the technological reality is different. For example, if workers perceive lasers to be a health risk, they may refuse to use a system with lasers in the display or in the trackers, even if those lasers are eye safe.
Ergonomics and ease of use are paramount considerations. Whether AR is truly a cost-effective solution in its proposed applications has yet to be determined. Another important factor is whether or not the technology is perceived as a threat to jobs, as a replacement for workers, especially with many corporations undergoing recent layoffs. AR may do well in this regard, because it is intended as a tool to make the user's job easier, rather than something that completely replaces the human worker. Although technology transfer is not normally a subject of academic papers, it is a real problem. Social and political concerns should not be ignored during attempts to move AR out of the research lab and into the hands of real users.
Conclusion
Augmented Reality is far behind Virtual Environments in maturity. No commercial vendor currently sells an HMD-based Augmented Reality system. Today AR systems are primarily found in academic and industrial research laboratories. The first deployed HMD-based AR systems will probably be in the application of aircraft manufacturing. Both Boeing and McDonnell Douglas are exploring this technology. The former uses optical approaches, while the latter is pursuing video approaches. Annotation and visualization applications in restricted, limited-range environments are deployable today. Applications in medical visualization will take longer. Prototype visualization aids have been used on an experimental basis, but the stringent registration requirements and ramifications of mistakes will postpone common usage for many years. AR will probably be used for medical training before it is commonly used in surgery. The next generation of combat aircraft will have Helmet-Mounted Sights with graphics registered to targets in the environment. Augmented Reality is a relatively new field, where most of the research efforts have occurred in the past ten years. One area where a breakthrough is required is tracking an HMD outdoors at the accuracy required by AR. If this is accomplished, several interesting applications will become possible. Two examples are: navigation maps and visualization of past and future environments. The first application is a navigation aid to people walking outdoors. An AR system makes navigation easier by performing the association step automatically. If the user's position and orientation are known, and the AR system has access to a digital map of the area, then the AR system can draw the map in 3-D directly upon the user's view. The second application is visualization of locations and events as they were in the past or as they will be after future changes are performed.
References
[1] Teleoperators and Virtual Environments , 355-385 A Survey of Augmented Reality Ronald T. Azuma Hughes Research Laboratories 3011 Malibu Canyon Road, MS RL96 Malibu, CA 90265 azuma@isl.hrl.hac.com
[2] Ronald Azuma HRL Laboratories, Yohan Baillot NRL Virtual Reality Lab/ITT Advanced Engineering, Reinhold Behringer Rockwell Scienti.c Steven Feiner Columbia University
[3] Simon Julier NRL Virtual Reality Lab/ITT Advanced Engineering, Blair MacIntyre Georgia Institute of Technology, Recent Advances in Augmented Reality
[4] James R Vallino Interactive Augmented Reality Submitted in partial Fulfillment of the Requirements for the Degree Doctor of philosophy. se.rit.edu/~jrv/research/ar/introduction.html


CONTENTS
1. Introduction¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦...1
2. Design¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦...2
¢ Optical see-through HMD
¢ Video see-through HMD
¢ Monitor based AR
3. Registration problem¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦.8
¢ Static problem
¢ Dynamic problem
4. Sensing problem¦..¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦14
¢ Greater input variety and bandwidth
¢ Higher accuracy
¢ Long range
5. Advantage of Augmented Reality over Virtual Environment...¦¦.17
6. Applications¦.¦¦¦¦¦¦¦...¦¦¦¦¦¦¦¦¦¦¦¦...18
¢ Medical
¢ Maintenance and repair
¢ Visualization
¢ Entertainment
¢ Military
7. Future areas of work and research¦¦¦¦¦¦¦¦¦¦¦¦¦.19
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ABSTRACT
Video games have been entertaining us for nearly 30 years, ever since Pong was introduced to arcades in the early II 970's.Computer graphics have become much more sophisticated since then, and soon, game graphics will seem all too real. In the next decade, researchers plan to pull graphics out of your television screen or computer display and integrate them into real- world environments. This new technology called augmented reality, will further blur the line between what is real and what is computer-generated by enhancing what we see, hear, feel and smell.
Augmented reality will truly change the way we view the world. Picture yourself walking or driving down the street. With augmented-reality displays, which will eventually look much like a normal pair of glasses, informative graphics will appear in your field of view, and audio will coincide with what ever you see. These enhancements will be refreshed continually to reflect the moments of your head.
Augmented reality is still in the early stage of research and development at various universities and high-tech companies. Eventually, possibly by the end of this decade we will see the first mass-marketed augmented-reality system, which can be described as "the Walkman of the 21st Century".
ACKNOWLEDGEMENT
Firstly I would like to express my sincere gratitude to the Almighty for His solemn presence throughout the seminar and presentation study .1 would also like to express my special thanks to the Principal Prof. K. Rajendran for providing an opportunity to undertake this seminar and presentation .1 am deeply indebted to our seminar and presentation coordinator Mr. Saini Jacob, Assistant Professor in the Department of Computer Science and Engineering for providing me with valuable advice and guidance during the course of the study.
I would like to extend my heartfelt gratitude to the Faculty of the Department of Computer Science and Engineering for their constructive support and cooperation at each and every juncture of the seminar and presentation study.
Finally I would like to express my gratitude to Sree Narayana Gurukulam College of Engineering for providing me with all the required facilities without which the seminar and presentation study would not have been possible.

CONTENTS
1. INTRODUCTION
Augmented reality (AR) refers to computer displays that add virtual information to a user's sensory perception. Most AR research focuses on see-through devices, usually worn on the head that overlay graphics and text on the user's view of his or her surroundings. In general it superimposes graphics over a real world environment in real time.
Getting the right information at the right time and the right place is key in all these applications. Personal digital assistants such as the Palm and the Pocket PC can provide timely information using wireless networking and Global Positioning System (GPS) receivers that constantly track the handheld devices. But what make Augmented Reality different is how the information is presented: not on a separate display but integrated with the user's perceptions. This kind of interface minimizes the extra mental effort that a user has to expend when switching his or her attention back and forth between real-world tasks and a computer screen. In augmented reality, the user's view of the world and the computer interface literally become one.
Real Augmented Augmented Virtual
Environment Reality virtuality Environment
Between the extremes of real life and Virtual Reality lies the spectrum of Mixed Reality, in which views of the real world are combined in some proportion with views of a virtual environment. Combining direct view, stereoscopic videos, and stereoscopic graphics, Augmented Reality describes that class of displays that consists primarily of a real world environment, with graphic enhancement or augmentations.
In Augmented Virtuality, real objects are added to a virtual environment. In Augmented Reality, virtual objects are added to real world. An AR system supplements the real world with virtual (computer generated) objects that appear to co-exist in the same space as the real world. Virtual Reality is a synthetic environment.
1.1 Comparison between AR and virtual environments
The overall requirements of AR can be summarized by comparing them against the requirements for Virtual Environments, for the three basic subsystems that they require.
1. Scene generator : Rendering is not currently one of the major problems in AR. VE systems have much higher requirements for realistic images because they completely replace the real world with the virtual environment . In AR, the virtual images only supplement the real world. Therefore, fewer virtual objects need to be drawn, and they do not necessarily have to be realistically rendered in order to serve the purposes of the application.
2. Display devices: The display devices used in AR may have less stringent requirements than VE systems demand, again because AR does not replace the real world. For example, monochrome displays may be adequate for some AR applications, while virtually all VE systems today use full color. Optical see-through HMD's with a small field-of-view may be satisfactory because the user can still see the real world with his peripheral vision; the see-through HMD does not shut off the user's normal field-of-view. Furthermore, the resolution of the monitor in an optical see-through HMD might be lower than what a user would tolerate in a VE application, since the optical see-through HMD does not reduce the resolution of the real environment.
3. Tracking and sending: While in the previous two cases AR had lower requirements than VE that is not the case for tracking and sensing. In this area, the requirements for AR are much stricter than those for VE systems. A major reason for this is the registration problem.
2. EVOLUTION
¢ Although augmented reality may seem like the stuff of science fiction, researchers have been building prototype system for more than three decades. The first was developed in the 1960s by computer graphics pioneer Ivan Surtherland and his students at Harvard University.
¢ In the 1970s and 1980s a small number of researchers studied augmented reality at institution such as the U.S. Air Force's Armstrong Laboratory, the NASA Ames Research Center and the university of North Carolina at Chapel Hill.
¢ It wasn't until the early 1990s that the term "Augmented Reality "was coined by scientists at Boeing who were developing an experimental AR system to help workers assemble wiring harnesses.
¢ In 1996 developers at Columbia University develop 'The Touring Machine'
¢ In 2001 MIT came up with a very compact AR system known as "MIThrill".
¢ Presently research is being done in developing BARS (Battlefield Augmented Reality Systems) by engineers at Naval Research Laboratory, Washington D.C.
3. WORKING
AR system tracks the position and orientation of the user's head so that the overlaid material can be aligned with the user's view of the world. Through this process, known as registration, graphics software can place a three dimensional image of a tea cup, for example on top of a real saucer and keep the virtual cup fixed in that position as the user moves about the room. AR systems employ some of the same hardware technologies used in virtual reality research, but there's a crucial differences: whereas virtual reality brashly aims to replace the real world, augmented reality respectfully supplement it.
Augmented Reality is still in an early stage of research and development at various universities and high-tech companies. Eventually, possible by the end of this decade, we will see first mass-marketed augmented reality system, which one researcher calls "The Walkman of the 21st century". What augmented reality attempts to do is not only super impose graphics over a real environment in real¬time, but also change those graphics to accommodate a user's head- and eye-movements, so that the graphics always fit and perspective.
Here are the three components needed to make an augmented-reality system work:
Head-mounted display Tracking system Mobile computing power

3.1 Head-Mounted Display
Just as monitor allow us to see text and graphics generated by computers, head-mounted displays (HMD's) will enable us to view graphics and text created by augmented-reality systems. There are two basic types of HMD's
- Optical see-through
- Video see-through

Optical Display Video Display
Fig 1: Optical and Video Display
3.1.1 Optical see-through display
Monitors
Real World

Head Head Tracker
Optical
V v y Combiners
Fig 2: Optical see-through HMD conceptual diagram.
A simple approach to optical see-through display employs a mirror beam splitter- a half silvered mirror that both reflects and transmits light. If properly oriented in front of the user's eye, the beam splitter can reflect the image of a computer display into the user's line of sight yet still allow light from the surrounding world to pass through. Such beam splitters, which are called combiners, have long been used in head up displays for fighter-jet- pilots (and, more recently, for drivers of luxury cars). Lenses can be placed between the beam splitter and the computer display to focus the image so that it appears at a comfortable viewing distance. If a display and optics are provided for each eye, the view can be in stereo. Sony makes a see-through display that some researchers use, called the "Glasstron".
3.1.2 Video see-through displays


Real World

Combined Video Fig 3: Video see-through HMD conceptual diagram
In contrast, a video see through display uses video mixing technology, originally developed for television special effects, to combine the image from a head worn camera with synthesized graphics. The merged image is typically presented on an opaque head worn display. With careful design the camera can be positioned so that its optical path is closed to that of the user's eye; the video image thus approximates what the user would normally see. As with optical see through displays, a separate system can be provided for each eye to support stereo vision. Video composition can be done in more than one way. A simple way is to use chroma-keying: a technique used in many video special effects. The background of the computer graphics images is set to a specific color, say green, which none of the virtual objects use. Then the combining step replaces all green areas with the corresponding parts from the video of the real world. This has the effect of superimposing the virtual objects over the real world. A more sophisticated composition would use depth information at each pixel for the real world images; it could combine the real and virtual images by a pixel-by-pixel depth comparison. This would allow real objects to cover virtual objects and vice-versa.
A different approach is the virtual retinal display, which forms images directly on the retina. These displays, which Micro Vision is developing commercially, literally draw on the retina with low power lasers modulated beams are scanned by microelectro-mechanical mirror assemblies that sweep the beam horizontally and vertically. Potential advantages include high brightness and contrast, low power consumption, and large depth of field.

it*

Fig 5: Two optical see-through HMD's, made by Hughes Electronics
3.1.3 Comparison of optical see through and video see through displays
Each of approaches to see through display design has its pluses and minuses. Optical see through systems allows the user to see the real world with resolution and field of view. But the overlaid graphics in current optical see through systems are not opaque and therefore cannot completely obscure the physical objects behind them. As result, the superimposed text may be hard to read against some backgrounds, and three-dimensional graphics may not produce a convincing illusion. Furthermore, although a focuses physical objects depending on their distance, virtual objects are all focused in the plane of the display. This means that a virtual object that is intended to be at the same position as a physical object may have a geometrically correct project and implimentationion, yet the user may not be able to view both objects in focus at the same time.
In video see-through systems, virtual objects can fully obscure physical ones and can be combined with them using a rich variety of graphical effects. There is also discrepancy between how the eye focuses virtual and physical objects, because both are viewed on same plane. The limitations of current video technology, however, mean that the quality of the visual experience of the real world is significantly decreased, essentially to the level of the synthesized graphics, with everything focusing at the same apparent distance. At present, a video camera and display is no match for the human eye.
An optical approach has the following advantages over a video approach
1. Simplicity: Optical blending is simpler and cheaper than video blending. Optical approaches have only one "stream" of video to worry about: the graphic images. The real world is seen directly through the combiners, and that time delay is generally a few nanoseconds. Video blending, on the other hand, must deal with separate video streams for the real and virtual images. The two streams of real and virtual images must be properly synchronized or temporal distortion results. Also, optical see through HMD's with narrow field of view combiners offer views of the real world that have little distortion. Video cameras almost always have some amount of distortion that must be compensated for, along with any distortion from the optics in front of the display devices. Since video requires cameras and combiners that optical approaches do not need, video will probably be more expensive and complicated to build than optical based systems.
2. Resolution: Video blending limits the resolution of what the user sees, both real and virtual, to the resolution of the display devices. With current displays, this resolution is far less than the resolving power of the fovea. Optical see-through also shows the graphic images at the resolution of the display devices, but the user's view of the real world is not degraded. Thus, video reduces the resolution of the real world, while optical see-through does not.
3. Safety: Video see-through HMD's are essentially modified closed-view HMD's. If the power is cut off, the user is effectively blind. This is a safety concern in some applications. In contrast, when power is removed from an optical see-through HMD, the user still has a direct view of the real world. The HMD then becomes a pair of heavy sunglasses, but the user can still see.
4. No eye offset: With video see-through, the user's view of the real world is provided by the video cameras. In essence, this puts his "eyes" where the video cameras are not located exactly where the user's eyes are, creating an offset between the cameras and the real eyes. The distance separating the cameras may also not be exactly the same as the user's interpupillary distance (IPD). This difference between camera locations and eye locations introduces displacements from what the user sees compared to what he expects to see. For example, if the cameras are above the user's eyes, he will see the world from a vantage point slightly taller than he is used to.
Video blending offers the following advantages over optical blending
1. Flexibility in composition strategies: A basic problem with optical see-through is that the virtual objects do not completely obscure the real world objects, because the optical combiners allow light from both virtual and real sources. Building an optical see-through HMD that can selectively shut out the light from the real world is difficult. Any filter that would selectively block out light must be placed in the optical path at a point where the image is in focus, which obviously cannot be the user's eye. Therefore, the optical system must have two places where the image is in focus: at the user's eye and the point of the hypothetical filter. This makes the optical design much more difficult and complex. No existing optical see-through HMD blocks incoming light in this fashion. Thus, the virtual objects appear Ghost-like and semi-transparent. This damages the illusion of reality because occlusion is one of the strongest depth cues. In contrast, video see-through is far more flexible about how it merges the real and virtual images. Since both the real and virtual are available in digital form, video see-through compositors can, on a pixel-by-pixel basis, take the real, or the virtual, or some blend between the two to simulate transparency.
2. Wide field-of-view: Distortions in optical systems are a function of the radial distance away from the optical axis. The further one looks away from the center of the view, the larger the distortions get. A digitized image taken through a distorted optical system can be undistorted by applying image processing techniques to unwrap the image, provided that the optical distortion is well characterized. This requires significant amount of computation, but this constraint will be less important in the future as computers become faster. It is harder to build wide field-of-view displays with optical see-through techniques. Any distortions of the user's view of the real world must be corrected optically, rather than digitally, because the system has no digitized image of the real world to manipulate. Complex optics is expensive and add weight to the HMD. Wide field-of-view systems are an exception to the general trend of optical approaches being simpler and cheaper than video approaches.
3. Real and virtual view delays can be matched: Video offers an approach for reducing or avoiding problems caused by temporal mismatches between the real and virtual images. Optical see-through HMD's offer an almost instantaneous view of the real world but a delayed view of the virtual. This temporal mismatch can cause problems. With video approaches, it is possible to delay the video of the real world to match the delay from the virtual image stream.
4. Additional registration strategies: In optical see-through, the only information the system has about the user's head location comes from the head tracker. Video blending provides another source of information: the digitized image of the real scene. This digitized image means that video approaches can employ additional registration strategies unavailable to optical approaches.
5. Easier to match the brightness of the real and virtual objects: Both optical and video technologies have their roles, and the choice of technology depends upon the application requirements. Many of the mismatch assembly and repair prototypes use optical approaches, possibly because of the cost and safety issues. If successful, the equipment would have to be replicated in large numbers to equip workers on a factory floor. In contrast, most of the prototypes for medical applications use video approaches, probably for the flexibility in blending real and virtual and for the additional registration strategies offered.
3.2 Tracking and Orientation
The biggest challenge facing developers of augmented reality the need to know where the user is located in reference to his or her surroundings. There's also the additional problem of tracking the movement of users eyes and heads. A tracking system has to recognize these movements and project and implimentation the graphics related to the real-world environment the user is seeing at any given movement. Currently both video see-through and optical see-through displays optically have lag in the overlaid material due to the tracking technologies currently available.
3.2.1 Indoor Tracking
Tracking is easier in small spaces than in large spaces. Trackers typically have two parts: one worn by the tracked person or object and other built into the surrounding environment, usually within the same room. In optical trackers, the targets - LED's or reflectors, for instance - can be attached to the tracked person or to the object, and an array of optical sensors can be embedded in the room's ceiling. Alternatively the tracked users can wear the sensors, and targets can be fixed to the ceiling. By calculating the distance to reach visible target, the sensors can determine the user's position and orientation.
Researchers at the University of North Carolina-Chapel Hill have developed a very precise system that works within 500 sq feet. The HiBall Tracking System is an optoelectronic tracking system made of two parts: Six user-mounted, optical sensors.
Infrared-light-emitting diodes (LED's) embedded in special ceiling panels.
The system uses the known location of LED's the known geometry of the user-mounted optical sensors and a special algorithm to compute and report the user's position and orientation. The system resolves linear motion of less than 0.2 millimeters, and angular motions less than 0.03 degrees. It has an update rate of more than 1500Hz, and latency is kept at about one millisecond. In everyday life, people rely on several senses-including what they see, cues from their inner ears and gravity's pull on their bodies- to maintain their bearings. In a similar fashion, "Hybrid Trackers" draw on several sources of sensory information. For example, the wearer of an AR display can be equipped with inertial sensors (gyroscope and accelerometers) to record changes in head orientation. Combining this information with data from optical, video or ultrasonic devices greatly improve the accuracy of tracking.
3.2.20ut door Tracking
Head orientation is determined with a commercially available hybrid tracker that combines gyroscopes and accelerometers with magnetometers that measure the earth's magnetic field. For position tracking we take advantage OF a high-precision version of the increasingly popular Global Positioning system receiver.
A GPS receiver can determine its position by monitoring radio signals from navigation satellites. GPS receivers have an accuracy of about 10 to 30 meters. An augmented reality, system would be worthless if the graphics project and implimentationed were of something 10 to 30 meters away from what you were actually looking at.
User can get better result with a technique known as differential GPS. In this method, the mobile GPS receiver also monitors signals from another GPS receiver and a radio transmitter at a fixed location on the earth. This transmitter broadcasts the correction based on the difference between the stationary GPS antenna's known and computed positions. By using these signals to correct the satellite signals, the differential GPS can reduce the margin of error to less than one meter.
The system is able to achieve the centimeter-level accuracy by employing the real-time kinematics GPS, a more sophisticated form of differential GPS that also compares the phases of the signals at the fixed and mobile receivers. Trimble Navigation reports that they have increased the precision of their global
positioning system (GPS) by replacing local reference stations with what they term a Virtual Reference Station (VRS). This new VRS will enable users to obtain a centimeter-level positioning without local reference stations; it can achieve long-range, real-time kinematics (RTK) precision over greater distances via wireless communications wherever they are located. Real-time kinematics technique is a way to use GPS measurements to generate positioning within one to two centimeters (0.39 to 0.79 inches). RTK is often used as the key component in navigational system or automatic machine guidance.
Unfortunately, GPS is not the ultimate answer to position tracking. The satellite signals are relatively weak and easily blocked by buildings or even foliage. This rule out useful tracking indoors or in places likes midtown Manhattan, where rows of tall building block most of the sky. GPS tracking works well in wade open spaces and relatively low buildings.
GPS provide far too few updates per second and is too inaccurate to support the precise overlaying of graphics on nearby objects. Augmented Reality system places extra ordinary high demands on the accuracy, resolution, repeatability and speed of tracking technologies. Hardware and software delays introduce a lag between the user's movement and the update of the display. As a result, virtual objects will not remain in their proper position as the user moves about or turns his or her head. One technique for combating such errors is to equip AR system with software that makes short-term predictions about the user's future motion by extrapolating from previous movements. And in the long run, hybrid trackers that include computer vision technologies may be able trigger appropriate graphics overlays when the devices recognize certain objects in the user's view.

4. MOBILE COMPUTING POWER
For a wearable augmented realty system, there is still not enough computing power to create stereo 3-D graphics. So researchers are using whatever they can get out of laptops and personal computers, for now. Laptops are just now starting to be equipped with graphics processing unit (GPU's). Toshiba just now added a NVIDIA to their notebooks that is able to process more than 17-million triangles per second and 286-million pixels per second, which can enable CPU-intensive programs, such as 3D games. But still notebooks lag far behind-NVIDIA has developed a custom 300-MHz 3-D graphics processor for Microsoft's Xbox game console that can produce 150 million polygon per second”and polygons are more complicated than triangles. So you can see how far mobiles graphics chips have to go before they can create smooth graphics like the ones you see on your home video-game system.
5.APPLICATIONS
Only recently have the capabilities of real-time video image processing, computer graphics systems and new display technologies converged to make possible the display of a virtual graphical image correctly registered with a view of the 3D environment surrounding the user. Researchers working with the AR system have proposed them as solutions in many domains. The areas have been discussed range from entertainment to military training. Many of the domains, such as medical are also proposed for traditional virtual reality systems. This section will highlight some of the proposed application for augmented reality.
5.1 Medical
Because imaging technology is so pervasive throughout the medical field, it is not surprising that this domain is viewed as one of the more important for augmented reality systems. Most of the medical application deal with image guided surgery. Pre-operative imaging studies such as CT or MRI scans, of the patient provide the surgeon with the necessary view of the internal anatomy. From these images the surgery is planned. Visualization of the path through the anatomy to the affected area where, for example, a tumor must be removed is done by first creating the 3D model from the multiple views and slices in the preoperative study. This is most often done mentally though some systems will create 3D volume visualization from the image study. AR can be applied so that the surgical team can see the CT or MRI data correctly registered on the patient in the operating theater while the procedure is progressing. Being able to accurately register the images at this point will enhance the performance of the surgical team.
Another application for AR in the medical domain is in ultra sound imaging. Using an optical see-through display the ultrasound technician
can view a volumetric rendered image of the fetus overlaid on the abdomen of the pregnant woman. The image appears as if it were inside of the abdomen and is correctly rendered as the user moves.

5.2 Entertainment
A simple form of the augmented reality has been in use in the entertainment and news business for quite some time. Whenever you are watching the evening weather report the weather reporter is shown standing in the front of changing weather maps. In the studio the reporter is standing in front of a blue or a green screen. This real image is augmented with the computer generated maps using a technique called chroma-keying. It is also possible to create a virtual studio environment so that the actors can appear to be positioned in a studio with computer generated decorating.
Movie special effects make use of digital computing to create illusions. Strictly speaking with current technology this may not be considered augmented reality because it is not generated in the real-time. Most special effects are created off-line, frame by frame with a substantial amount of user interaction and computer graphics system rendering. But some work is progressing in computer analysis of the live action images to determine the camera parameters and use this to drive the generation of the virtual graphics objects to be merged.
Princeton Electronics Billboard has developed an augmented reality system that allows broadcasters to insert advertisement into specific areas of the broadcast image. For example, while broadcasting a baseball game this system would be able to place an advertisement in the image so that it appears on the outfield wall of the stadium. By using pre-specified reference points in the stadium, the system automatically determines the camera angles being used and referring to the pre-defined stadium map inserts the advertisement into the current place. AR QUAKE, 76 designed using the same platform, blends users in the real world with those in a purely virtual environment. A mobile AR user plays as a combatant in the computer game Quake, where the game runs with a virtual model of the real environment.

Fig 8: AR in sports broadcasting. The annotations on the race cars and the yellow first down line are inserted into the broad cast in real time.
5.3 Military Training
The military has been using display in cockpits that present information to the pilot on the windshield of the cockpit or the visor of their flight helmet. This is a form of Augmented Reality display. SIMNET, a distributed war games simulating system, is also embracing augmented reality technology. By equipping military personnel with helmet mounted visor displays or a special purpose rangefinder the activities of other units participating in the exercise can be imaged. While looking at the horizon, for example, the display equipped soldier could see a helicopter rising above the tree line. This helicopter could be being flown in simulation by another participant. In war time, the display of the real battlefield scene could be augmented with annotation information or highlighting to emphasize hidden enemy units.
5.4 Engineering Design
Imagine that a group of designers are working on the model of a complex device for their clients. The designers and clients want to do a joint design reviews even though they are physically separated. If each of them had a conference room that was equipped with an augmented re4ality display this could be accomplished. The physical prototype that the designers have mocked up is imaged and displayed in the client's conference room in 3D. The clients can walk around display looking at different aspects of it. To hold the discussion the client can point at the prototype to highlight sections and this will be reflected on the real model in the augmented display that the designers are using. Or perhaps in an earlier stage of the design, before a prototype is built, the view in each conference room is augmented with a computer generated image of the current design built from the CAD file describing it. This would allow real time interactions with elements of the design so that either side can make adjustments and change that are reflected in the view seen by both groups.
5.5 Robotics and Telerobotics
In the domain of robotics and Telerobotics an augmented display can assist the user of the system. A Telerobotics operator uses a visual image of the remote workspace to guide the robot. Annotation of the view would still be useful just as it is when the scene is in front of the operator. There is an added potential benefit. Since often the view of the remote scene is monoscopic, augmentation with wire frame drawings of structures in the view can facilitate visualization of the remote 3D geometry. If the operator is attempting a motion it could be practiced on a virtual robot that is visualized as an augmentation to the real scene. The operator can decide to proceed with the motion after seeing the results. The robot motion could then be executed directly which in a telerobotics application would eliminate any oscillations caused by long delays to the remote site.

Fig 9: Virtual lines show a planned motion of a robot arm
I
5.6 Manufacturing, maintenance and repair
When the maintenance technician approaches a new or unfamiliar piece of equipment instead of opening several repair manuals they could put on an
1 augmented reality display. In this display the image of the equipment would be
i
I augmented with annotations and information pertinent to the repair. For example,
the location of fasteners and attachment hardware that must be removed would be
! highlighted. Then the inside view of the machine would highlight the boards that
need to be replaced. The military has developed a wireless vest worn by personnel that is attached to an optical see-through display. The wireless connection allows the soldier to access repair manuals and images of the equipment. Future versions might register those images on the live scene and provide animation to show the procedures that must be performed.Boeing researchers are developing an augmented reality display to replace the large work frames used for making wiring harnesses for their aircraft. Using this experimental system, the technicians are guided by the augmented display that shows the routing of the cables on a generic frame used for all harnesses. The augmented display allows a single fixture to be used for making the multiple harnesses.
5.7 Consumer design
Virtual reality systems are already used for consumer design. Using perhaps more of a graphics system than virtual reality, when you go to the typical home store wanting to add a new deck to your house, they will show you a graphical picture of what the deck will look like. It is conceivable that a future system would allow you to bring a video tape of your house shot from various viewpoints in your backyard and in real time it would augment that view to show the new deck in its finished form attached to your house. Or bring in a tape of your current kitchen and the augmented reality processor would replace your current kitchen cabinetry with virtual images of the new kitchen that you are designing.
Applications in the fashion and beauty industry that would benefit from an augmented reality system can also be imaged. If the dress store does not have a particular style dress in your size an appropriate sized dress could be used to augment the image of you. As you looked in the three sided mirror you would see the image of the new dress on your body. Changes in hem length, shoulder styles or other particulars of the design could be viewed on you before you place the order. When you head into some high-tech beauty shops today you can see what a new hair style would look like on a digitized image of yourself. But with an advanced augmented reality system you would be able to see the view as you moved. If the dynamics of hair are included in the description of the virtual object you would also see the motion of hair as your head moved.
5.8 Instant information
Tourists and students could use these systems to learn more about a certain historical event. Imagine walking onto a Civil War battlefield and seeing a re-creation of historical events on a head-mounted, augmented reality display. It would immerse you in the event, and the view would be panoramic. The recently started Archeoguide project and implimentation is developing a wearable AR system for providing tourists with information about a historical site in Olympia, Greece.
6. CONCLUSION
Augmented reality is far behind Virtual Environments in maturity. Several commercial vendors sell complete, turnkey Virtual Environment systems. However, no commercial vendor currently sells an HMD-based Augmented Reality system. A few monitor-based "virtual set" systems are available, but today AR systems are primarily found in academic and industrial research laboratories.
The first deployed HMD-based AR systems will probably be in the application of aircraft manufacturing. Both Boeing and McDonnell Douglas are exploring this technology. The former uses optical approaches, while the letter is pursuing video approaches. Boeing has performed trial runs with workers using a prototype system but has not yet made any deployment decisions. Annotation and visualization applications in restricted, limited range environments are deployable today, although much more work needs to be done to make them cost effective and flexible.
Applications in medical visualization will take longer. Prototype visualization aids have been used on an experimental basis, but the stringent registration requirements and ramifications of mistakes will postpone common usage for many years. AR will probably be used for medical training before it is commonly used in surgery.
The next generation of combat aircraft will have Helmet Mounted Sights with graphics registered to targets in the environment. These displays, combined with short-range steer able missiles that can shoot at targets off-bore sight, give a tremendous combat advantage to pilots in dogfights. Instead of having to be directly behind his target in order to shoot at it, a pilot can now shoot at anything within a 60-90 degree cone of his aircraft's forward centerline. Russia and Israel currently have systems with this capability, and the U.S is expected to field the AIM-9X missile with its associated Helmet-mounted sight in 2002.
Augmented Reality is a relatively new field, where most of the research efforts have occurred in the past four years. Because of the numerous challenges and unexplored avenues in this area, AR will remain a vibrant area of research for at least the next several years.
After the basic problems with AR are solved, the ultimate goal will be to generate virtual objects that are so realistic that they are virtually indistinguishable from the real environment. Photorealism has been demonstrated in feature films, but accomplishing this in an interactive application will be much harder. Lighting conditions, surface reflections, and other properties must be measured automatically, in real time. More sophisticated lighting, texturing, and shading capabilities must run at interactive rates in future scene generators. Registration must be nearly perfect, without manual intervention or adjustments.
While these are difficult problems, they are probably not insurmountable. It took about 25 years to progress from drawing stick figures on a screen to the photorealistic dinosaurs in "Jurassic Park." Within another 25 years, we should be able to wear a pair of AR glasses outdoors to see and interact with photorealistic dinosaurs eating a tree in our backyard.
n. FUTURE DIRECTIONS
This section identifiers areas and approaches that require further researches to produce improved AR systems.
Hybrid approach
Further tracking systems may be hybrids, because combining approaches can cover weaknesses. The same may be true for other problems in AR. For example, current registration strategies generally focus on a single strategy. Further systems may be more robust if several techniques are combined. An example is combining vision-based techniques with prediction. If the fiducially are not available, the system switches to open-loop prediction to reduce the registration errors, rather than breaking down completely. The predicted viewpoints in turn produce a more accurate initial location estimate for the vision-based techniques.
Real time systems and time-critical computing
Many VE systems are not truly run in real time. Instead, it is common to build the system, often on UNIX, and then see how fast it runs. This may be sufficient for some VE applications. Since everything is virtual, all the objects are automatically synchronized with each other. AR is different story. Now the virtual and real must be synchronized, and the real world "runs" in real time. Therefore, effective AR systems must be built with real time performance in mind. Accurate timestamps must be available. Operating systems must not arbitrarily swap out the AR software process at any time, for arbitrary durations. Systems must be built ton guarantee completion within specified time budgets, rather than just "running as quickly as possible". These are characteristics of flight simulators and a few VE systems. Constructing and debugging real-time systems is often painful and difficult, but the requirements for AR demand real-time performance.
Perceptual and psychophysical studies
Augmented reality is an area ripe for psychophysical studies. How much lag can a user detect? How much registration error is detectable when the head is
moving? Besides questions on perception, psychological experiments that explore performance issues are also needed. How much does head-motion prediction improve user performance on a specific task? How much registration error is tolerable for a specific application before performance on that task degrades substantially? Is the allowable error larger while the user moves her head versus when she stands still? Furthermore, no much is known about potential optical illusion caused by errors or conflicts in the simultaneous display of real and virtual objects.
Portability
It is essential that potential AR applications give the user the ability to walk around large environments, even outdoors. This requires making the requirement self-continued and portable. Existing tracking technology is not capable of tracking a user outdoors at the required accuracy.
Multimodal displays
Almost all work in AR has focused on the visual sense: virtual graphic objects and overlays. But augmentation might apply to all other senses as well. In particular, adding and removing 3-D sound is a capability that could be useful in some AR applications.
8. BIBLIOGRAPHY
> A survey of Augmented Reality by Ronald T. Azuma
> Recent Advances in Augmented Reality by Ronald TAzuma, Yohan Baillot, Reinhold Beringer, Simon Julier and Blair Maclntyre
> Augmented Reality: A new way of seeing. Steven K Feiner
> Augmented Reality and computer Augmented Environment, available at csl.sony.co.jp/project and implimentation/ar/ref.html
1. INTRODUCTION 1
2. EVOLUTION 4
3. WORKING 5
3.1 HEAD MOUNTED DIPLAY 6
3.1.1 OPTICAL SEE-THROUGH DP LAYS 6
3.1.2 VIDEO SEE-THROUGH DISPLAYS 7
3.1.3 COMPARISON OF OPTICAL AND VIDEO SEE THROUGH DISPLAY 9
3.2 TRACKING AND ORIENTATION 13
3.2.1 INDOOR TRACKING 13
3.2.2 OUTDOOR TRACKING 14
4. MOBILE COMPUTING POWER 16
5. APPLICATION 17
5.1 MEDICAL 17
5.2 ENTERTAINMENT 18
5.3 MILITARY TRAIN8ING 19
5.4 ENGINEERING DESIGN 20
5.5 ROBOTICS AND TELEROBOTICS 20
5.6 MANUFACTURING, MAINTENANCE AND REPAIR 21
5.7 CONSUMER DESIGN 22
5.8 INSTANT INFORMATION 22
6. CONCLUSION 23
7. FUTURE DIRECTIONS 25
! 8. BIBLIOGRAPHY 27
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15-10-2010, 07:12 AM


Augmented Reality

Goals

Taxonomy

Technology

What is Augmented Reality?

A combination of a real scene viewed by a user and a virtual scene generated by a computer that augments the scene with additional information.

What is the Goal of AR?

To enhance a person’s performance and perception of the world

But, what is the ultimate goal????

The Ultimate Goal of AR

Create a system such that no user CANNOT tell the difference between the real world and the virtual augmentation of it.
Augmented Reality vs.
Virtual Reality

Augmented Reality

System augments the real world scene
User maintains a sense of presence in real world
Needs a mechanism to combine virtual and real worlds


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30-10-2010, 12:47 PM

Hi,
visit this thread for a related report:
topicideashow-to-augmented-reality-learning
Use Search at http://topicideas.net/search.php wisely To Get Information About Project Topic and Seminar ideas with report/source code along pdf and ppt presenaion
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14-03-2011, 09:28 PM

Augmented Reality (AR)
Renjith.R & Bijin.V.S
(Department of computer application(MCA) ,Mohandas college of Engineering and technology
Anad, Trivandrum)


.pdf   Augmented Reality.pdf (Size: 164.04 KB / Downloads: 211)

Abstract
Technology has advanced to the point here realism in virtual reality is very achievable. However, in
our obsession to reproduce the world and human experience in virtual space, we overlook the most
important aspects of what makes us who we are—our reality. On the spectrum between virtual reality,
which creates immersible, computer-generated environments, and the real world, augmented reality
is closer to the real world. Augmented reality adds graphics, sounds, haptics and smell to the natural
world as it exists .Augmented reality will truly change the way we view the world. Picture yourself
walking or driving down the street. With augmented-reality displays, which will eventually look much
like a normal pair of glasses, informative graphics will appear in your field of view and audio will
coincide with whatever you see. These enhancements will be refreshed continually to reflect the
movements of your head. In this article, we will take a look at this future technology, its components
and how it will be used. Augmented reality (AR) refers to computer displays that add virtual
information to a user's sensory perceptions. Most AR research focuses on see-through devices,
usually worn on the head that overlay graphics and text on the user's view of his or her surroundings.
In general it superimposes graphics over a real world environment in real time.Augmented reality is
far more advanced than any technology you've seen in television broadcasts, although early versions
of augmented reality are starting to appear in televised races and football games. These systems
display graphics for only one point of view. Next-generation augmented-reality systems will display
graphics for each viewer's perspective.

1. INTRODUCTION
1.1. DEFINITION
Augmented reality (AR) is a field of
computer research which deals with the
combination of real world and computer
generated data. Augmented reality (AR) refers to
computer displays that add virtual information to
a user's sensory perceptions. It is a method for
visual improvement or enrichment of the
surrounding environment by overlaying spatially
aligned computer-generated information onto a
human's view (eyes)
Augmented Reality (AR) was introduced as
the opposite of virtual reality: instead of
immersing the user into a synthesized, purely
informational environment, the goal of AR is to
augment the real world with information
handling capabilities.
AR research focuses on see-through
devices, usually worn on the head that overlay
graphics and text on the user's view of his or her
surroundings. In general it superimposes
graphics over a real world environment in real
time.
An AR system adds virtual computer-
generated objects, audio and other sense
enhancements to a real-world environment in
real-time. These enhancements are added in a
way that the viewer cannot tell the difference
between the real and augmented world.
1.2 PROPERTIES
AR system to have the following properties:
1. Combines real and virtual objects in a real
environment;
2. Runs interactively, and in real time; and
3. Registers (aligns) real and virtual objects with
each other.
Definition of AR to particular display
technologies, such as a head mounted display
(HMD). Nor do we limit it to our sense of sight.
AR can potentially apply to all senses, including
hearing, touch, and smell.

2. AUGMENTED REALITY Vs VIRTUAL
REALITY

The term Virtual Reality was defined as "a
computer generated, interactive, three-dimensional
environment in which a person is immersed." There
are three key points in this definition. First, this
virtual environment is a computer generated three-
dimensional scene which requires high
performance computer graphics to provide an
adequate level of realism. The second point is that
the virtual world is interactive. A user requires real-
time response from the system to be able to interact
with it in an effective manner. The last point is that
the user is immersed in this virtual environment
One of the identifying marks of a virtual reality
system is the head mounted display worn by users.
These displays block out all the external world and
present to the wearer a view that is under the
complete control of the computer. The user is
completely immersed in an artificial world and
becomes divorced from the real environment.
A very visible difference between these two
types of systems is the immersiveness of the
system. Virtual reality strives for a totally
immersive environment. The visual, and in some
systems aural and proprioceptive, senses are under
control of the system.
In contrast, an augmented reality system
is augmenting the real world scene necessitating
that the user maintains a sense of presence in that
world. The virtual images are merged with the real
view to create the augmented display. There must
be a mechanism to combine the real and virtual that
is not present in other virtual reality work.
Developing the technology for merging the real and
virtual image streams is an active research topic .
3. Different AR Techniques
There are two basic techniques for
combining real and virtual objects; optical and
video techniques. While optical technique uses
an optical combiner, video technique uses a
computer for combining the video of the real
world (from video cameras) with virtual
images (computer generated). AR systems use
either Head Mounted Display (HMD), which
can be closed-view or see-through HMDs, or
use monitor-based configuration. While
closed-view HMDs do not allow real world
direct view, see-through HMDs allow it, with
virtual objects added via optical or video
techniques

4. What Makes AR Work?
The main components that make an AR system
works are,
1. Display
This corresponds to head mounted
devices where images are formed. Many objects
that do not exist in the real world can be put into
this environment and users can view and exam on
physical properties etc. are just parameters in
simulation.
2. Tracking
Getting the right information at the
right time and the right place is the key in all these
applications. Personal digital assistants such as the
Palm and the Pocket PC can provide timely
information using wireless networking and Global
Positioning System (GPS) receivers that constantly
track the handheld devices

3. Environment Sensing
It is the process of viewing or sensing
the real world scenes or even physical environment
which can be done either by using an optical
combiner, a video combiner or simply retinal view.

4. Visualization and Rendering
Some emerging trends in the recent
development of human-computer interaction (HCI)
can be observed. The trends are augmented reality,
computer supported cooperative work, ubiquitous
computing, and heterogeneous user interface. AR is
a method for visual improvement or enrichment of
the surrounding environment by overlaying
spatially aligned computer-generated information
onto a human's view (eyes).

This is how AR works.
 Pick A Real World Scene
Real world. User's view through
the see-through head-worn display of the real
world, showing two struts and a node without
any overlaid graphics.
 Add your Virtual Objects in it
User's view of the virtual world
intended to overlay the view of the real
world.
 Delete Real World Objects
 Not Virtual Reality since Environment
Real
these objects. The properties such as complexity,

5.Augmented Reality Application
Domains

Only recently have the capabilities of
real-time video image processing, computer
graphic systems and new display technologies
converged to make possible the display of a virtual
graphical image correctly registered with registered
with a view of the 3D environment surrounding the
user. Researchers working with augmented reality
systems have proposed them as solutions in many
domains. The areas that have been discussed range
from entertainment to military training. Many of
the domains, such as medical are also proposed for
traditional virtual reality system

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19-04-2011, 11:12 AM


.ppt   final.ppt (Size: 335 KB / Downloads: 205)
Augmented Reality
Man makes robot intelligent
What is Augmented Reality?

A combination of a real scene viewed by a user and a virtual scene generated by a computer that augments the scene with additional information.
What is the Goal of AR?
To enhance a person’s performance and perception of the world
But, what is the ultimate goal????
The Ultimate Goal of AR
Create a system such that no user CANNOT tell the difference between the real world and the virtual augmentation of it.
Augmented Reality vs. Virtual Reality
Augmented Reality
System augments the real world scene
User maintains a sense of presence in real world
Needs a mechanism to combine virtual and real worlds
Virtual Reality:
Totally immersive environment
Visual senses are under control of system (sometimes aural and proprioceptive senses too)
Miligram’s Reality-Virtuality Continuum
Miligram’s Taxonomy for Mixed Reality Displays
Reproduction Fidelity – quality of computer generated imagery
Extent of Presence Metaphor – level of immersion of the user within the displayed scene
Extent of World Knowledge – knowledge of relationship between frames of reference for the real world, the camera viewing it, and the user
Combining the Real and Virtual Worlds
We need:
Precise models
Locations and optical properties of the viewer (or camera) and the display
Calibration of all devices
To combine all local coordinate systems centered on the devices and the objects in the scene in a global coordinate system
Combining the Real and Virtual Worlds (cont)
Register models of all 3D objects of interest with their counterparts in the scene
Track the objects over time when the user moves and interacts with the scene
Realistic Merging
Requires:
Objects to behave in physically plausible manners when manipulated
Occlusion
Collision detection
Shadows
**All of this requires a very detailed description of the physical scene
Components of an Augmented Reality System
Research Activities
Develop methods to register the two distinct sets of images and keep them registered in real-time
New work in this area has started to use computer vision techniques
Develop new display technologies for merging the two images
Performance Issues
Augmented Reality systems are expected:
To run in real-time so that the user can move around freely in the environment
Show a properly rendered augmented image
Therefore, two performance criteria are placed on the system:
Update rate for generating the augmenting image
Accuracy of the registration of the real and virtual image
Limitations for Updating the Generated Images
Must be at 10 times/second
More photorealistic graphics rendering
Current technology does not support fully lit, shaded and ray-traced images of complex scenes
Failures in Registration
Failures in registration due to:
Noise
Position and pose of camera with respect to the real scene
Fluctuations of values while the system is running
Time delays
In calculating the camera position
In calculating the correct alignment of the graphics camera
Display Technologies
Monitor Based
Head Mounted Displays:
Video see-through
Optical see-through
Monitor Based Augmented Reality
Simplest available
Little feeling of being immersed in environment
Optical see-through HMD
Video see-through HMD
Video Composition for Video see-through HMD
Chroma-keying
Used for special effects
Background of computer graphics images is set to a specific color
Combining step replaces all colored areas with corresponding parts from video
Depth Information
Combine real and virtual images by a pixel-by-pixel depth comparison
Advantages of Video see-through HMD
Flexibility in composition strategies
Wide field of view
Real and virtual view delays can be matched
Advantages of Optical see-through HMD
Simplicity
Resolution
No eye offset
Applications
Medical
Entertainment
Military Training
Engineering Design
Robotics and Telerobotics
Manufacturing, Maintenance, and Repair
Consumer Design
Hazard Detection
Audio

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27-04-2011, 10:04 AM

PRESENTED BY:
Sandeep Kumar


.ppt   Augmented Reality.ppt (Size: 8.6 MB / Downloads: 138)
What is AR?
ä Augmented Reality (AR) is a variation of VE/VR.
 VR technologies completely immerse a user inside a synthetic environment. While immersed, the user cannot see the real world around him.
 In contrast, AR allows the user to see the real world, with virtual objects superimposed upon or composited with the real world.
ä AR supplements reality, rather than completely replacing it. It creates the illusion that the virtual and real objects coexisted in the same space.
ä AR can be thought of as the "middle ground“ between VE (completely synthetic) and telepresence (completely real)
ä AR systems have the following three characteristics:
 Combines real and virtual
 Interactive in real time
 Registered in 3-D
ä This definition allows other technologies besides Head Mounted Displays (HMDs) while retaining the essential components of AR.
ä Does not include film or 2-D overlays like "Jurassic Park" featuring photorealistic virtual objects seamlessly blended with a real environment in 3-D, as they are not interactive.
ä 2-D virtual overlays on top of live video can be done at interactive rates, but the overlays are not combined with the real world in 3-D. Hence, they are not AR.
Motivation
ä AR enhances a user’s perception of interaction with the real world.
ä The virtual objects display information that the user cannot directly detect with his own senses.
ä The information conveyed by the virtual objects helps a user perform real-world tasks.
ä AR is a specific example of what is known as Intelligence Amplification (IA): using the computer as a tool to make a task easier for a human to perform.
Applications
ä Main classes of applications:
1. Medical
2. Manufacturing and repair
3. Annotation and visualization
4. Robot path planning
5. Entertainment
6. Military aircraft
There are several miscellaneous applications
Characteristics
ä Discussion on the characteristics of AR systems and design issues encountered when building an AR system.
ä Two ways to accomplish this augmentation: optical or video technologies.
ä Blending the real and virtual poses problems with focus and contrast and some applications require portable AR systems to be truly effective.
Characteristics: Augmentation
ä Besides adding objects to a real environment, AR also has the potential to remove them.
ä Graphic overlays might be used to remove or hide parts of the real environment from a user. e.g., to remove a desk in the real environment, draw a representation of the real walls and floors behind the desk and "paint" that over the real desk, effectively removing it from the user's sight.
ä Has been done in movies. Doing this interactively in an AR system will be much harder, but this removal may not need to be photorealistic to be effective.
ä Blending the real and virtual poses problems with focus and contrast and some applications require portable AR systems to be truly effective.
ä AR might apply to all senses, not just sight.
ä AR could be extended to include sound.
ä The user would wear headphones equipped with microphones on the outside. The headphones would add synthetic, directional 3D sound, while the external microphones would detect incoming sounds from the environment. Thus, one can cancel selected real incoming sounds and add others to the system. This is not easy, but possible.
ä Another example is haptics.
ä Gloves with devices that provide tactile feedback might augment real forces in the environment. For example, a user might run his hand over the surface of a real desk which can augment the feel of the desk, perhaps making it feel rough in certain spots.
Characteristics: Focus & Contrast
ä Focus can be a problem for both optical and video components. Ideally the virtual should match the real.
 Depending on video camera’s depth-of-field (DOF) and focus settings, parts of the real world may not be in focus.
 In computer graphics, everything is rendered with a pinhole model, so regardless of distance, everything is in focus.
 To overcome this, graphics can be rendered to simulate a limited DOF, and the video camera can have autofocus lens.
ä Contrast is a big issue owing to its large dynamic range in real environments.
 The eye is a logarithmic detector simultaneously handling contrasts varying by 6 orders! Most display devices do not even come close.
 Thus optical devices are usually made dark-tinted to reduce this range. For video, everything must be clipped or compressed into the monitor’s dynamic range.

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09-05-2011, 03:47 PM


.ppt   Seminar_Augmented Reality1.ppt (Size: 1.45 MB / Downloads: 135)
Augmented Reality
1. Introduction
Augmented Reality :

An Augmented Reality system generates a composite view for the user. It’s a combination of the real scene viewed by the user and a virtual scene generated by the computer that augments the scene with additional information.
AR systems have the following three properties:
Blends real and virtual, in real environment
Interactive in real time
Registered in 3D
1.1 AR View
2. Virtual Reality (VR)

“A computer generated, interactive, three-dimensional environment in which a person is immersed.”
Requires high performance computer graphics to provide an adequate level of realism
Blocks out all the external world and present to the wearer a view that is under the complete control of the computer
3. VR v/s AR
Virtual Reality

Totally immersive environment.
Completely immersed in an artificial world and becomes divorced from the real environment
Visual senses are under control of system
Augmented Reality
System augments the real world scene
User maintains a sense of presence in real world
Needs a mechanism to combine virtual and real worlds
3.1 Reality-Virtuality Continuum
4. Need for AR

For some applications, it may be desirable to use as much as possible real world in the scene rather creating a new scene using computer imagery. Eg. Medicine and telerobotics
Can maintain the high-level of detail and realism that one finds in the real world.
AR enhances real world, while VR replaces or simulates the real world
5. Design
The four components of any AR system are
5.1 The Display System (usually an HMD)
5.2 The Tracking System
5.3 Mobile Computing Power
5.4 Input device (usually a wrist mounted keyboard)
5.1 The Display System
Allows the user to see the image and text created by the Augmented Reality Systems
There are basically two types of display systems: 5.1.1 Optical see-through
5.1.2 Video see-through
5.1.1 Optical see-through displays
Direct viewing of real world through naked eye
Uses optical combiners- partially reflective, partially transmissive
Similar to HUDs used in military aircrafts
5.1.1 Optical see-through display
5.1.2 Video see-through display
Combination of closed-view HMD and one or more head-mounted video cameras
Video from camera combined with graphic images created by the scene generator
Advantages of Optical see-through display
Simplicity- cheap and simple (one video stream).
Resolution- user’s real world view is not retarded
Safety
No eye offset
5.2 The Tracking System
Used to find the position and orientation of the viewer
Where the user is located with respect to his surroundings
Movement of user’s head
The two main functions of tracking system:
Find the person’s position in space
Using the three Cartesian coordinates- x, y and z
Find the direction in which the person is looking
Using three angles- pitch(or elevation), roll and yaw(azimuth)
Tracking System (contd)
The six degrees of freedom
5.3 Mobile Computing Power
Ideal computing device – wearable computers
Freedom in movement
Ergonomics
Ruggedness (depends on the application)
Features:
Portable while operational
Hands-free use
Attention getting
Always ON
Mobile Computing Power (contd)
6. Challenges/Design Issues
6.1 Display Issues

Focus and contrast
Eye offset
Field of view
6.2 Registration Issues
6.3 Tracking Issues
Sample rate
Update rate
Latency
6.4 Portability Issue
6.2 Registration Issues
6.2.1 Static Errors
Optical Distortions
Mechanical misalignments
Incorrect viewing parameters(FOV, interpupillary dist.)
6.2.2 Dynamic Errors
System lag (latency)
6.3 Tracking Issues
Sample rate- rate at which sensors are checked for data
Update rate- The rate at which the system reports new position coordinates to the host computer
Latency(or lag)- delay between the movement of the remotely sensed object and the report of the new position
7. Applications
7.1 Medical

Training aid – Virtual instructions for a novice surgeon
Surgery – ultrasound imaging
7.2 Manufacturing and repair
Machine assembly – Instructions as 3-D drawings superimposed upon the actual equipment
7.3 Military
BARS- Battle Field Augmented Reality System
Military Aircrafts-HUDs and HMSs
7.4 Annotation and Visualization
Used in sports – to name or point out cars in a race
7.5 Entertainment
Games – the most recent one being an AR version of the popular game Quake- ARQuake
7.1 Applications: Medicine
7.2 Applications: Manufacture/Repair
7.4 Applications: Annotation
8. Future Prospects
AR has a wide vista of applications in store for future:
Medical: In minimal invasive surgeries, endoscopy, laparoscopy
Collaborative Applications: Military- BARS
Commercial Applications: Ads, games and sports-Race F/X
Tourism: ARCHEOGUIDE- helps tourists with info. Implemented in Greece on a test basis.
Multimodal displays (haptics and auditory interactions)
9. Conclusion
AR systems are far behind VR systems in terms of maturity. Augmented Reality is a relatively new field, where most of the research efforts have occurred in the past few years. Because of the numerous challenges and unexplored avenues in this area, AR will remain a vibrant area of research for at least the next several years.
After the basic problems with AR are solved, the ultimate goal will be to generate virtual objects that are so realistic that they are virtually indistinguishable from the real environment.
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resmiraveendran
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#10
02-07-2011, 10:23 PM

pls send me the seminar and presentation report of augmented reality
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smart paper boy
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#11
14-07-2011, 02:56 PM

AUGMENTED REALITY
Augmented reality (AR) refers to computer displays that add virtual information to a user's sensory perceptions. Most AR research focuses on "see-through" devices, usually worn on the head, that overlay graphics and text on the user's view of his or her surroundings. AR systems track the position and orientation of the user's head so that the overlaid material can be aligned with the user's view of the world.
Consider what AR could make routinely possible. A repairperson viewing a broken piece of equipment could see instructions highlighting the parts that need to be inspected. A surgeon could get the equivalent of x-ray vision by observing live ultrasound scans of internal organs that are overlaid on the patient's body. Soldiers could see the positions of enemy snipers who had been spotted by unmanned reconnaissance planes. Getting the right information at the right time and the right place is key in all these applications. Personal digital assistants such as the Palm and the Pocket PC can provide timely information using wireless networking and Global Positioning System (GPS) receivers that constantly track the handheld devices. But what makes augmented reality different is how the information is presented: not on a separate display but integrated with the user's perceptions. In augmented reality, the user's view of the world and the computer interface literally become one.
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smart paper boy
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#12
15-07-2011, 12:37 PM


.doc   AUGMENTED REALITYlkm.doc (Size: 327.5 KB / Downloads: 83)
1. Introduction and Motivation
1.1. Interactive Augmented Reality Interface

Since its inception computer graphics has been interactive in nature. One of the novel aspects of the seminal computer graphics work in Ivan Sutherland’s Sketchpad system (Sutherland 1963) was the ability of a user to interact with the system. A classic text in computer graphics, Newman and Sproull’s Principles of Interactive Computer Graphics, (Newman and Sproull 1973) highlights this interactive nature directly in the title. The creation of interactive virtual environments originated in the computer graphics domain. The ultimate interactive environment is the real world. The goal of augmented reality systems is to combine the interactive real world with an interactive computer-generated world in such a way that they appear as one environment. Figure 1 shows a virtual clock tower placed in a real three-dimensional scene. As the user moves about the real scene and views it from different viewpoints, the image of the clock tower is continually updated so that it is perceived as a real object in the scene. This verisimilitude carries through to human interactions with the virtual object such as moving or lifting it, and the object’s interaction with real objects, such as collisions.
1.2 The Major Challenges for Augmented Reality Systems
The major challenge for augmented reality systems is how to combine the real world and virtual world into a single augmented environment. To maintain the user’sillusion that the virtual objects are indeed part of the real world requires a consistent registration of the virtual world with the real world.
These relationships are the object-to-world, O, world-to-camera, C, and camera-to image plane, P, transforms (Figure 2). The object-to-world transform specifies the position and orientation of a virtual object with respect to the world coordinate system that defines the real scene. The world-to-camera transform defines the pose of the video camera that views the real scene. Finally, the camera-to-image plane transform specifies the project and implimentationion the camera performs to create a 2D image of the 3D real scene.
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seminar paper
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#13
13-02-2012, 12:20 PM

to get information about the topic augmented reality full report ,ppt and related topic refer the link bellow


topicideashow-to-augmented-reality--5207

topicideashow-to-mobile-augmented-reality-realization

topicideashow-to-augmented-reality--5207?page=2

topicideashow-to-augmented-reality--1379

topicideashow-to-augmented-reality-learning

topicideashow-to-bionics-augmented-reality-in-a-contact-lens-full-report

topicideashow-to-augmented-reality--5207?pid=50266

topicideashow-to-augmented-reality--5207?pid=44978

topicideashow-to-augmented-reality

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seminar paper
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#14
14-02-2012, 09:57 AM

to get information about the topic augmented reality full report ,ppt and related topic refer the link bellow


topicideashow-to-augmented-reality--5207

topicideashow-to-mobile-augmented-reality-realization

topicideashow-to-augmented-reality--5207?page=2

topicideashow-to-augmented-reality--1379

topicideashow-to-augmented-reality-learning

topicideashow-to-bionics-augmented-reality-in-a-contact-lens-full-report

topicideashow-to-augmented-reality--5207?pid=50266

topicideashow-to-augmented-reality--5207?pid=44978

topicideashow-to-augmented-reality
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shubham_tonk
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#15
14-04-2012, 08:27 PM

Thanks a lot uploader!exactly what i needed!!! Big GrinBig GrinBig GrinWinkWinkWink
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