Tuesday, January 10, 2012

I Was Wrong...ish

In my previous post I described a method of using metameric color separation to produce 3D images using passive glasses. Further research reveals that

a) the technology I was describing is less common than I thought

b) it doesn't work quite as I described it.

The system I described is the one used by Dolby 3D cinema projection system, a technology which is not used for 3D televisions, as far as I can discover. Dolby 3D uses the glasses I described that block specific wavelengths of red, green and blue light but the projector doesn't use special phosphors to generate the six colors of light needed but, instead, uses a six-segment spinning color wheel to color the light. Dolby 3D's chief competitor -- RealD Cinema -- uses left-handed and right-handed circularly polarized light for its glasses. Some 3D televisions (the ones that use inexpensive glasses that don't need batteries) use the same technology as the RealD to present stereo images.

Dolby 3D had an initial advantage in the marketplace because its metameric color separation process works with ordinary projection screens while RealD circular polarized projectors require special screens that don't mess with the polarization of the light they reflect. But as more and more multiplexes are built, or refurbished, with all new stuff, including new screens, that advantage is fading and the cheaper, more durable glasses you can use with RealD have given that technology a boost and Dolby 3D seems to be fading.

This image (from the Wikipedia page on Dolby 3D) makes the technology fairly easy to understand.

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