Mixed Reality is a combination of Augmented Reality (AR) which is the physical Reality and Virtual Reality (VR) where physical and real objects co-exist and interact. Mixed Reality (MR) is otherwise known as “Hybrid Reality.” In recent years Mixed Reality has gained increased media popularity. Due to the advancement of display technologies and computer vision, it is possible to encompass the physical world and the virtual world. Fields such as Architecture, engaging signal processing, Simulation-Based Learning (SBL), Interactive Product Content Management (IPCM), computer vision, computer graphics, user interfaces, medical, education, military training, and gaming would be more comfortable and exciting with mixed reality technology. MR concepts are used in broad range areas which include automotive industries and office environments.
In early 1990s Mixed Reality came into existence. First Mixed reality system was developed in the United States Air Force Armstrong Laboratories by Louis Rosenberg to enable human users to control robots in a physical environment.
Figure 1: Reality – Virtuality Continuum by Milgram and Kishino. [1]
Milgram and Kishino defined the Reality-Virtuality Continuum, as shown in Fig 1.
- On the left (Real Environment): Here, the user will remain in the physical (real) environment.
- In the Middle (Mixed Reality): Here, the users will experience the part in which the real-world blends with the virtual world.
- On the right (Virtual Reality): Here, the users will experience the complete digital environment, and they are not aware of what happens in Reality (real environment) around them.
An example of Augmented Reality is Microsoft HoloLens. Augmented Virtuality (AV) captures the real objects and superimposes them into a virtual scene. A video of a real person showed in a virtual environment is an example for AV.
The applications of MR are similar to Augmented Reality (AR). It is used in Military training to produce a computer model of combat battlegrounds. MR is used in the field of engineering for 3D modeling apps and software. When it comes to medical or health care, there are many potential applications in which mixed Reality is helpful in visualizing medical imaging such as CAT scan, MRI scan, or ultrasonic scan. The domain of Remote Engineering and Virtual Instrumentation can be benefited by Mixed Reality.
The overview of displays that are commonly used in MR Environments is Head-Mounted Displays, hand-held displays, ambient projections, and hand-held projectors.
Head-Mounted Displays (HMD) are the most common displays used in MR, which is developed for Virtual Reality Systems. For MR, a virtual image should be mixed with real environment imagery. This can be achieved by attaching a video camera to HMD. HMDs [2] allow a field-of-view of 45 degrees diagonally, 36 degrees horizontally and about 27 degrees vertically, a resolution of 1280 by 1024 pixels and weight are of 750 grams.
Hand-held Displays are used for MR by using a metaphor of magic lens. Using cameras attached to displays the mixture of real and virtual images is achieved. Similar to HMDs, the orientation and position of hand-held displays must be known in order to generate virtual images correctly.
Ambient projections: It is an alternative to project the computer-generated images directly onto the environment using video projectors. The projection can be confined to a specific area, such as a desk.[3][4] or it can be covered by an actuated mirror to direct the video beam. Unlike HMDs and hand-held displays, the positions of the projectors are fixed or controlled by the system.
Hand-held Projectors: To directly point at the object of interest, users can use these projectors.
The tracking systems which are most commonly used in Mixed Reality system or environment are Global Positioning System (GPS), visual markers reffered as fiducial, Acoustic tracking Systems, magnetic and inertial sensors, and Hybrid Systems.
Global Positioning Systems (GPS): GPS uses radio signals to locate the current location of users. Each satellite continuously transmits the message regarding the position of other satellites with the time mentioned. By calculating the time of arrival of message and position of 4 satellites we get the position of user’s current location. GPS is developed by US ministry of defense. Today, it is still used for military purposes, but also for the navigation and guidance of civilian vehicles like airplanes, ships, and cars, as well as in outdoor mobile MR systems, in combination with another system to provide orientation.
REFERENCES:
- P. Milgram and F. Kishino. A Taxonomy of Mixed Reality Visual Displays. IEICE Transactions on Information Systems.
- Bungert, HMD headset VR-helmet comparison chart. www.stereo3d.com.
- Wellner, In the book: Communications of the ACM, volume 36, page 87–96. ACM Press, New York.
- Fitzmaurice, G., Ishii, H, Buxton, In the book: Proceedings of the SIGCHI conference on Human factors in computing systems, page 442–449.Addison-Wesley Publishing Co, New York.
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