Haptics Technologies Bringing Touch to Multimedia
The term “haptics” refers to the science of sensing and manipulation through touch. Multiple disciplines such as biomechanics, psychophysics, robotics, neuroscience, and software engineering converge to support haptics, and generally, haptic research is d
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Machine Haptics
4.1 Introduction The development of HAVE applications encompasses the development of both audiovisual devices and haptic devices to deliver a higher sense of immersion in a 3D space. 2D and 3D audio technologies have been introduced to create the illusion of sound sources placed anywhere in a three-dimensional space. By processing relative left and right speaker signals, apparent sound locations can be perceived at an arbitrary point in space. Visual information in HAVE applications can be characterized by the field of view (FOV), which represents the total visible angular deviation. The FOV needs to cover between 60 and 100ı along the horizontal axis in order for the user to be immersed in the virtual environment. This is less than the capability of the human eye, which has an FOV range between 180 and 270ı , depending on whether the eye is moving or not. The update rate for visual feedback is around 75 Hz, and the suggested resolution is on the magnitude of 1;960 1;280 pixels, even though it is possible to reach 8;000 8;000 pixels. Most stereo vision systems are based on human binocular cues in order to render depth information. In the human binocular visual system, each eye captures its own image of the environment; the two images are then sent to the brain for processing. The brain combines them into a single picture by matching the similarities and compensates for the differences, which are usually small. The difference between the two captured images is the reason human beings can see a stereo image. In HAVE applications, there are several ways to view stereoscopic images. In the first technique, a head-mounted display provides each eye with a separate image. The provided images can originate from a single video source or two different video sources. The FOV is made flexible through the use of head tracking. The same principle can be applied with a less bulky device known as shutter glasses or active glasses. In this case, users are asked to wear glasses and look at an appropriately configured system such as an LCD monitor. The shutters in the glasses, with the help of an infrared emitter, are than synchronized with the display system. Images are alternately displayed to each eye to provide different perspectives so that each eye A. El Saddik et al., Haptics Technologies, Springer Series on Touch and Haptic Systems, DOI 10.1007/978-3-642-22658-8 4, © Springer-Verlag Berlin Heidelberg 2011
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4 Machine Haptics
sees only the image intended for it (the glasses achieve this by alternately darkening over one eye at a time). Passive glasses, on the other hand, are color encoded or polarized glasses used to view a projected image. A stereoscopic system projects stereo video on the screen where the two images are tinted to different colors. Due to the color encoded glasses, each lens blocks the light color it is tinted to, so the image tinted to the opposite color makes it through to the eye. Finally, auto-stereoscopic displays are the new era in stereo vision. Users do not need to wear a
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