What is Augmented Reality?
Augmented reality is a computer system which has the ability to combine the real world and computer generated data. With this system, virtual objects are blended into real footage in real time. Thus, we can imagine the high potential that this technology might have if applied in the field of education.
In augmented reality, the computer works as a mirror. With a camera and a black and white printed marker, we transmit to the computer the angle and coordinates about an object. Thus real elements are mixed with virtual elements in real time, and in the same way as in a mirror, the image appears inverted on the screen, which makes orientation a very complicated task.
Virtual models can be animated and multiplied. With this technology we are able to create and combine animated sequences in order to control a virtual object and share the interaction with others.
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In the field of education, we can use this technology to create interactive 3-D books that respond to changes in the angle of observation.
From the beginning, the advertising companies were the first to use this system using interactive web based augmented reality applications. Because of its potential, augmented reality will be widely applied in fields such as architecture, surgery, simulations, geology and ecology among others.
How it Works?
The basic process of creation in augmented reality is to create virtual models that will be stored in a database. After this, the model will be retrieved from the mentioned database, rendered and registered into the scene. Sometimes, this process implies serious difficulties in many area applications. The virtual content must be stored on the database and also published as printed material, containing an index to our database. This communication to the database increases the complexity of the virtual model as final work.
To avoid these difficulties, is necessary to fully encode our virtual content in a bar code, which is not understandable to a human without using a specific augmented reality system. When captured by an AR system, the virtual models are then extracted from the incoming image.
Embedding ---> Acquisition ---> Extraction ---> Registration ---> Rendering
The virtual model is created and printed. This printed representation is then acquired by the augmented reality device. After, the virtual models are extracted from the acquired image. Finally, the virtual models are registered onto the scene and after rendered.
Besides adding virtual objects into the real world, AR must be able to remove them. Desirable systems would be those that incorporate sound to broaden the augmented experience. These systems should integrate headsets equipped with microphones to capture incoming sound from the environment, thus having the ability to hide real environmental sounds by generating a masking signal.
Characteristics of Augmented Reality
The main goal of AR is the interactivity between the user and virtual objects.
HT it is the system that allows the user to have tactile experiences within immersive environments. With this system the user interacts with the virtual environment through an augmented system. To bring realism to these interactions, the system must allow the user to feel the touch of surfaces, textures and the weight and size of virtual objects.
With haptic devices, mass can be assigned to virtual elements so that the weight and other qualities of the object can be felt in the fingers. This system requires complex computing devices endowed with great power. Furthermore, the system must recognize the three-dimensional location of fiducial points in the real scene.
Position-Based Augmented Reality
For correct compensation between the virtual and real image, the system must represent both images in the same frame of reference by using sensitive calibration and measurement systems to determine the different coordinate frames in the AR system. This system measures the position and orientation of the camera with respect to the coordinate system of the real world. These two parameters determine the world-to-camera transform, C. We can quantify the parameters of camera-to-image, P, by calibrating the video camera. Finally, the third parameter, O, is computed by measuring the position and orientation of the virtual object in the real world, being rendered and combined with the live video.
Computer Vision for Augmented Reality
Always on Time
Marked to Standard
Augmented Reality uses computer vision methods to improve performance. Thus, the system eliminates calibration errors by processing of the live video data. Other systems invert the camera projection to obtain an approximation of the viewer pose.
Recently, a mixed method uses the fiducial tracking, which is combined with a magnetic position tracking system that determines the parameters of the cameras in the scene.
Currently, the problems of camera calibration are solved by registering the virtual objects over the live video.
If we want an AR system to be credible, it must have the ability to animate the virtual elements within the scene. Thus, we can distinguish between objects moving by themselves and those whose movements are produced by the user. These interactions are represented in the object-to-world transform by a multiplication with a translation matrix.
Since the user can walk through large spaces, Augmented Reality should pay special attention to the portability of it systems, far from controlled environments, allowing users to walk outdoor with comfort. This is accomplished by making the scene generator, the head-mounted display and the tracking system capable of being autonomous.
What are the Differences between Augmented Reality and Virtual Reality?
While AR enriches the user´s view of the world by creating interactive virtual objects and introducing them in our real world, VR systems immerse us in a virtual world that completely replaces the real world outside. Natural environments contain important information that can not be simulated by computer.
To augment the information from the real world, it is better to integrate the virtual elements within the natural environment, so that the users feels fully immersed. To achieve this goal we need a system that incorporates these elements in the most efficient way. This system will need to continually send stimuli to the user to perceive that sense of immersion. In addition, changes made by the user shall be correctly interpreted by the system, in this way the virtual elements will be incorporated with their changes in the real environment. Any inconsistency between the real an virtual parts will result in a disconnection between virtual elements and their position in the real world.
Virtual environments require real-time response to display a high level of realism, which implies the need for high power AR systems to introduce the user in a perfect immersive experience.
This system must correctly analyze the user´s movements to determine how they will affect the scene.
Comparison Against Virtual Environments
Augmented Reality requires three basic subsystems compared to Virtual Reality:
- Scene generator: Since the virtual environment completely replaces real world, it will need higher technical requirements than those of Augmented Reality. On the other hand, AR doesn´t need to realistically reproduce the virtual items to be perceived integrated into the scene.
- Display device: While VE uses colour systems in all its applications, with AR is sufficient to use monochrome screens, thus consuming fewer resources and energy.
- Tracking and sensing: In this field, Augmented Reality is more stringent in its requirements that those for virtual environment systems.
Mixed Systems: Augmented Simulation
AUGSIM is the combination of Augmented Reality and Seamless Simulation. This combination augments the real world with computer entities and actions, thus be used in virtual training and gaming. Thus, through AR we can experience virtual sounds and images in our real world.
What graphical systems does Augmented Reality use?
The standard HMD provides the user total immersion in the virtual environment. To achieve this isolation, the system must use video cameras to obtain an accurate view of the physical world Some AR researchers work with two types of Head-mounted displays to increase the sense of immersion inside the scene. These two systems are the following.
Optical See-Trough HMD
In Augmented Reality, Head-Mounted Displays show an improved world in front of the user´s eyes.
These portable computers with an integrated video camera, detect real world situations, allowing the user to perceive the real world together with specific information generated by the computer.
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OST eliminates the channel that captures images of the real scene. Thus, the merging of virtual and real world is carried out optically in front of the viewer, with a similar system to Head-Up display.
Video See-Through Augmented Reality Display
This system has the same configuration as the monitor-based display and requires a system to merge the real and virtual video channels into a single image.
The video camera provide the user´s view of the real world. After, graphic images are combined with the video by the scene generator, merging the real world with the virtual objects. Finally, the result is sent to the monitor. This convergence is achieved through a system known as video keying. While the first channel is called the key, the other is the background.
The video composition can be done through:
- Chroma-keying. The background of the images is set to a special colour, which none virtual objects use. After this, the combining set replaces colour areas, inserting the corresponding parts from video of the real world. At last, virtual objects are superimposed over the real world.
- Depth Information. This method combine the real and virtual images by pixel-by-pixel depth analysis.
Advantages and Dissadvantages of Optical and Video Approaches
Both systems have advantages and disadvantages. Since both work with video cameras to capture images of the real world, there may be errors of timing during the merging operation. With the optical see-through system, is not possible to compensate for delay errors. These errors must be compensated by correctly timing of the other parts of the system.
In both monitor-based and video-see through systems, the video camera is capturing images from real world. Access to these images can be and advantage if the system analyzes the video data. After this, the system will extract tracking information through position sensors on the HMD.
- Simplicity: In addition to optical blending is cheaper and easier than video blending, it must not deal with video streams where images from the virtual and real world are separated. Both images must be perfectly synchronized to avoid errors of temporal distortion.
- Resolution: Video blending has a very limited resolution of both real and virtual images. Optical see-through has a higher resolution in its screen, making the viewer´s image of the real scene not reduced.
- Safety: While a lack of energy makes the video see-through head-mounted displays stop issuing images, optical see-through continues showing a perfect view of the real world.
- No eye offset: Video see-through puts the camera view where the user´s eyes are. Differences between these locations introduces distortions between the virtual and real view. VST can avoid this problem by using mirrors to create another optical paths so that the user has the feeling of getting real image without displacement. Through this system, the cameras can see what the user´s eyes see without the use of a head-mounted display.
Moreover, video blending offers some advantages over optical blending:
- Flexibility in composition strategies: Video see-through has advantage over optical see-through because it mixes better virtual and real objects, obscuring in a better way both elements in the real scene. VST can also simulate transparencies between these elements on a pixel-by-pixel basis.
- Wide field-of-view: VST optimally solves the distortion errors caused by optical systems, by using processing techniques that don´t distort the captured image.
- Real and virtual view delays can be matched: VST reduces problems caused by mismatches of time between virtual and real images. The view through a head-mounted display, provides an instantaneous view of the real scene, while the view of the virtual objects is displayed with a delay. With VST systems, is possible to delay the real world view to match the virtual image view.
- Additional registration strategies: Video blending provides additional information through the digitization of real world scene. This system uses additional resources for a better registration of optical approaches.
- Easier to match the brightness of real and virtual objects: Optical approaches are used in assembly and repair of many systems because of the cost and security they provide. Moreover, these system save time and labour, which represents a great saving by companies.
Focus and Contrast
In a video-based system, the images from the real and virtual world must be projected at the same distance by the monitor or head-mounted display optics.
To overcome the mismatches on the video camera´s depth-of-field, the graphics must be rendered simulating a limited depth-of-field. Moreover, would be advisable for the video camera had an autofocus lens.
To achieve good contrast, the brightness of the real and virtual elements must be correctly matched, because if the real scene is too bright, can wash out the virtual view. On the other hand, if the real environment is too dark the virtual image could wash out the real world scene.
What are the Applications of Augmented Reality?
Using this technology, the computer can visually track the user´s finger, witch functions as a digital pen, a mouse or other devices.
Annotation and visualization
Augmented reality could be used to annotate objects, public spaces and environments with any kind of information. This information could be public or private.
AR is useful to aid visualization tasks. For example, we could be able to look out a window and see how an imaginary new building would change or view of the real world.
In museums, the Head-Mounted Display detects the ID of the picture, generating a description of it. Moreover, the HMD identifies which picture the user is looking at, displaying specific information on the screen.
Manufacturing, Maintenance and Repair
This system can also be used in assembling and repair of mechanical, electronic and electrical parts. Thus, a user can point at parts of an engine model and the augmented reality system displays the name of the part and shows how to repair it. These instructions help us to understand an equipment, superimposing 3D drawing upon it.
AR could be used for assembly, maintenance and repair of equipment in aircrafts, printers, engines and automobiles among others.
Future AR systems will include complex animations that will show the mechanic how to repair in the most efficient way.
In surgical operations, AR provides an internal view of the patient. This visualization could aid in training for surgery, through ultrasound images, Computed Tomography scans or MRI scans that provide an useful view of the patient in real time. With this system, the information is captured by sensors and displayed on the patient, thus showing exactly where to perform the operation.
These virtual drawings show in an easy and graphical way the tasks that need to be done and how to do them efficiently. With ultrasound imaging, for example, the doctor can view a three-dimensional virtual image of the fetus overlaid on the abdomen of the pregnant woman. Moreover, AR could guide doctors to find the site of a tumour during needle biopsies.
AR devices can also be used to help in problems related to Parkinson´s Disease.
Future applications of Augmented Reality in the medical field will be craniofacial surgery visualization and guide in reconstructive surgery.
Ultrasound-Guided Breast Biopsy
In the field of surgery, ultrasound-guided breast biopsy has been used for diagnosis, and to guide for needle localization in lesions prior to biopsy. AR systems helps the doctor in cyst aspiration providing a three-dimensional image to guide the needle to the right place.
Nowadays, Augmented Reality is used in weather reports by changing computer-generated maps. Thus, the real image is augmented using the technique of chroma-keying. Furthermore, special techniques have been developed to insert advertisements into certain areas of a specific place during the broadcast. We often see 3D advertising in football games promoting products or services. These images are perfectly integrated using reference points in the stadium. Using this system, production costs are reduced by creating virtual sets than can be stored in a database.
The arms industry has long used displays in cockpits to the pilot in their flight helmet. Through the use of HMDs, the activities of other units participating in the exercise can be seen by the pilot.
Augmented reality can be used in aerial reconnaissance by markings in certain geographical areas.
These markings add information that will be analyzed by the control command, providing a way to aim the aircraft´s weapon.
Using AR systems, we can display virtual prototypes to our clients, thus the client can walk around the display analyzing its different elements and discussing the necessary changes on it. This allows a real interaction between the designer and client.
Augmented Reality displays can assist the user to guide remote robots. In these systems, the user uses a three-dimensional visualization which augments the information from the real world, providing guidance in geographical spaces.
Augmented Reality can be used in many areas of daily life. There are a wide variety of computer programs that assist the homeowner in remodelling projects to see how the changes will affect the different parts of a house.
AR may also benefit the fashion and beauty industry. For example cloth stores could have stored in a database different clothing that we could wear virtually. In beauty shops, we could see how a new hair style would look in us.
What Devices are Used in Augmented Reality?
Augmented Reality complements mobile computing systems for optimal integration of virtual elements within real world. Nowadays wearable AR devices are too expensive, complex, fragile and hard to carry for most people. However AR systems have proven advantages in a wide variety of fields such as engineering design, manufacturing, maintenance and repair, virtual navigation, entertainment, mobile construction and others.
The creators of AR systems combined the integration of a small computer with mobile devices so that users could carry them on their backs, while graphical augmentations were shown to them through Head-Mounted Displays. Despite the initial success of this system, its price remains extremely expensive and is very difficult to maintain.
Because of this set of problems, developers began to think in the use of lightweight wearable devices equipped with cameras such as PDAs or mobile phones.
AR Wearable Computers
Cellular phones are very useful because of their portability, adequate processing power and local network connectivity, but their small display size and low memory make them a very limited device for AR applications.
Although Tablet PCs don´t have the limitations of mobile phones, are too expensive and extremely heavy for single handed.
Is the optimal platform for the Hanheld AR framework. Its interface is very intuitive and its size and weight are optimal. Moreover, its processor and RAM memory are increasingly sophisticated.
What are the Major Challenges for Augmented Reality Systems?
The biggest problem facing the AR today, is how to combine the virtual elements with the real world in an augmented environment, keeping the user in the illusion that the virtual elements are part of the real world. To get a good combination of these elements, we must beware of the following relationships:
- Object to world O: Transforms the orientation and position of virtual elements with respect to to coordinate system of the real world.
- World-to camera C: Defines the position of the video camera that captures the real scene.
- Camera to image plane P: Creates a 2D image with the information obtained from the 3D scene. This requires that relationships between physical and virtual elements must be optimal.
The errors between these relationships, make the user perceive differences in appearance between real world objects and virtual elements, due to synchronization errors. These virtual elements, must interact with the user in the real world as natural as possible.
The solution to these problems would be to create a system that would eliminate the differences in perception between the real world and its augmentation.
What does Augmented Reality for Education?
The use of Augmented Reality in school promotes teamwork and allows viewing of three-dimensional models to students, which facilitates the task of learning through a fun and interactive process. Likewise, this system can be applied to a wide variety of learning areas outside the educational field.
Among the reasons that make AR attractive to be applied in educational centers, we find, among others, the interaction between virtual and real environments, the easy manipulation of objects within the virtual environment and the ease of movement from one space to another in real time.
Through the use of HMDs, AR promotes team communication, showing the possible gestures and other communication signals from the students of the group. All this information is viewed by students on their screen, which facilitates interpersonal communication. This allows this form of collaboration to be seen more as a face-to-face communication than an isolated communication through displays on the HMD screen. In these collaborative environments, the information taken from the real world is socially shared in the virtual space.
The advantage of using AR systems instead of other technologies, is that results highly intuitive for people who have no experience with other computer systems. Thus, even the youngest students can enjoy a fun interactive experience.
Little children often fantasize about being actors in a fairy tale. With AR, we can make this fantasy a reality, by using a book with markers that acts as primary interface. Thus, we can turn the pages, read the text, and we can see also three-dimensional animations that tell us the story better. These 3D models are embedded in the page of the book so the child can see the animations from any point of view, moving it from different angles. These animations can be adapted to any size of book, so that reading becomes a very fun and immersive experience.
These systems can be used at any educational level, making the learning process a very engaging task. To apply this system successfully, educators should collaborate with the developers of these applications to find the best way to apply it in school environments.
Future monitoring systems will be more robust, and will incorporate mixed media to remedy the mistakes of registration. These systems will fully reproduce the scenes in real time within the HMD.
Moreover, future AR systems will offer users the ability to walk great outdoor spaces. To achieve this, these systems will have to evolve towards better portability. To a greater sense of immersion, these systems should also incorporate 3D sound systems.
As for the political and social dimensions, through the gradual introduction of Augmented Reality in the daily tasks of our live, it will be more accepted by people. Gradually, we will see that this system allow the users to make their work easier and faster instead of been seen as a system that replaces human workers.
Augmented Reality is less technologically-advanced than Virtual Reality Systems, but by contrast, AR is much more commercial. Nowadays, AR can be found in research laboratories and academic centers.
The next development of AR will be initially on the aircraft manufacturing. In the other hand, its introduction to the medical field, will take longer than in other areas. AR will probably be used in medical training before than surgery.
Another area where AR will develop strongly in the coming years will be in tours through outdoor environments by wearing a Head-mounted display, facilitating the development of advanced navigation systems and visualizations of past and future environments. These systems will make the orientation a much easier task. AR systems will also include 3D maps displaying information about the elements we´re looking at, and their dimensions, and will show the easiest way to reach that destination.
Regarding the application of AR in education, the lesson will be better understood by visualizations of history, geography, anatomy and sciences in general that will make the learning process much more easier.
After solving the basic problems of Augmented Reality, advanced virtual elements will be developed that will be perceived as realistic as the real world.
To achieve this purpose, the conditions of lighting, texturing, shading and registration will be almost perfect, so we will wear a pair of glasses outdoors that will show us realistic virtual elements with which we will interact normally.