3D TV Glasses - What You Need To Know
3D TV glasses use our inherent ability to perceive three dimensions through clever manipulation of optical signals. The two human eyes receive a slightly different projection of objects in real life. When both projections of an image are sent to the brain, it processes them to form a unified image with three dimensions. This is called stereopsis and it gives humans the ability to perceive depth and distance in the real world.
3D TV glasses work on the same principle and provide each eye with a slightly different projection of the same image. The brain processes these projections in the same manner as it does even without the eyewear and the result is 3D perception. The eyewear is capable of providing these image inputs to each eye by using some innovative optical techniques.
There are two categories of 3D eyewear technology: passive and active. Passive 3D eyewear does not have to be powered on while active 3D eyewear requires a power source and an electronic signal for viewing 3D content. There are two major types of passive eyewear for 3D viewing - anaglyph and polarized.
Passive 3D Eyewear - Anaglyph
Anaglyph 3D glasses have two dissimilar coloured lenses, which are paired as red and blue or red and green. Typically, there will be two sets of the same image on the screen, offset from each other at a small angle. One image will have a red tint to it, while the other will have a blue tint.
The red lens on an anaglyph glass absorbs red light streaming from the television as a result of which the lens will cancel images with red tints to them and only show blue tinted images. The blue lens on the glasses works in the opposite way and shows only red tinted images. This way, the eye behind a red lens will receive blue image input while that behind a blue lens will receive red image input.
Each eye sends only one image to the brain, which interprets that both eyes are focusing on the same object. When the brain processes the two sets of images, it creates one 3 dimensional image with depth similar to that of images seen in normal stereoscopic vision.
Passive 3D Eyewear - Polarized
Polarized eyewear is another type of passive 3D technology, most frequently used in 3D cinema movies.
The ideal way to achieve polarization of images with 3D technology for home use is through a projector with 3D capability. The projector should also support polarizing technology such that images formed on screen will have two sets of the same image offset with each other.
The lenses of these 3D TV glasses have the ability to filter light waves from the screen that are polarized in a particular direction. So, each lens lets through only those light waves that are polarized to be compatible with it, and as a result of this, each eye receives image inputs of only one set of on-screen images.
The benefit of using polarized lenses in glasses as opposed to anaglyph ones is that the former does not distort colours or affect colour fidelity the way the latter does.
Active 3D Eyewear
Active 3D eye-wear with infrared sensors has been developed only in the recent past.
The sensors enable the glasses to connect with a display or television unit wirelessly. This, however, is possible only with 3D television units that support active 3D technology. Generally, two sets of the same image (offset slightly) are shown on the television screen with a small lag between them.
As on-screen images alternate, the lenses in the eyewear simultaneously alternate between turning opaque and transparent. So when the left eye’s image appears on screen, the right lens turns opaque and when the right eye’s image appears on screen, the left lens turns opaque. However, as the images alternate at an extremely high speed and they are timed perfectly with the eyewear; active 3D glasses users do not notice the flicker.
One important aspect of active 3D technology is that it reduces the effective refresh rate of the display. This is because when, for example, the original refresh rate of the display is 120 Hz, the sync signal is also locked at 120 Hz, but the right eye shutter blinks 60 times, as does the left eye shutter.
The number of 3D images perceived by the brain per second is halved, as two images on the display combine to make one 3D image. This was a significant hurdle in older television sets that had a low refresh rate, but in the latest LCD TV sets, refresh rates are high enough to give a seamless 3D viewing experience.
3D Eyewear Compatibility
Many consumers have found, much to their annoyance, that glasses from one brand do not usually work with TV sets from a different brand. This may happen sometimes when eyewear and television sets are not compatible with each other, either because of different technology being used or because of a difference in the signal format.
3D TV glasses compatibility is a bigger issue for active 3D technology. This is because even if the technology used is the same, the electronics used in the synchronizing system could be different, making it impossible, or at least very difficult, for glasses from one brand to work with a TV set from a different brand. But if this electronic aspect is resolved through standardization, then it would not be difficult to ensure that active 3D TV glasses are compatible with different television sets.
As of now, this compatibility will not work in your living room. For example, a pair of Samsung glasses will not turn on in the absence of a sync signal broadcast by a Samsung television. Also, Samsung and Panasonic 3D eyewear have slightly dissimilar colour filters in their lenses.
So even if users could synchronize their 3D glasses from one brand with the television set of another, the colours will be inaccurate as the colour filters in the lenses will not work well with the signal from the display.