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Sony Projector Gets Bright Images From Black Screen
da_foz writes "Sony has developed a new projector that can give a bright, unfaded picture without the need to eliminate ambient light. The secret is that they project onto a black screen instead of a white one. Their screen uses species filters so that white ambient light is absorbed, but the red, green, and blue light from the projector is reflected. Sony sees a possible use in home entertainment systems because of the ability to have a much bigger picture than conventional TVs as well as businesses adopting the projectors for presentations."
It probably appears black (or close to it) from the viewing angle when the projector is powered off.
It would seem that the ultimate version of this would use RGB lasers as the light source and notch filters on the screen. The narrowness of the notches would determine the depths of the black. The biggest trick would be in tuning the notch filters to reflect the off-axis, angled laser light.
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When your screen doesn't reflect so much of the ambient light anymore, you can use a projector that outputs less power. For one, this can lead to less hot projector lamps, thus a longer life for them.
It might also enable the use of lower-power technologies (LED-lasers anyone?), that might in turn make the projectors much cheaper.
Nice work by Sony
Now, is there a physicist in da house who knows how wide the reflection-band (in wavelength-terms) for R, G and B is?
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Actually, if it only reflect three specific wavelengths
then it's probably the _blackest_ thing you've ever seen.
I bought some high-end binoculars a while back. When you're looking through all the Nikons and Swarovskis and Leicas side by side, you start to realize when your eyes feel the little zing. It isn't pure resolution that does it, and your eyes compensate rapidly enough to changes in brightness (due to objective size or quality) that you don't often perceive differences except at dusk and dawn. (The only exceptions for me were old-style tank commander Zeiss binocs. Very bright.)
But when you hit a binoc that felt right for contrast, ahhh -- those were my handful of last choices. It's like seeing the world with the slanting light at around 6:30 on a summer night -- everything just pops out, so clear, and the slight 3-D exaggeration of the binocular view brings it out just that little bit more. The optics store people said that was a pretty common reaction -- a slight edge in contrast was a huge advantage.
Sounds like this screen has that going for it. Big selling point, next to potential competitors, if they can get it around the right price point.
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Sony engineers worked from the basic principle that projectors, like all TVs and monitors, form colors by blending three primary hues: red, green and blue. They came up with a filter that allows the screen to reflect only red, green and blue light. The other light in a room, such as white incandescent or fluorescent bulbs, isn't reflected.
Man I hate it when the newspapers print stupid things. Whaddaya wanna bet they are using something like polaroid or narrow bandpass quarter wave plate filters with a similarly filtered projector? What would be cool is a fluorescent screen and a projector that uses light (UV?) outside the visible spectrum. Then the screen really could be visibly black but it would still glow when stimulated by the projector.
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If it reflects _anything_, it isn't black.
Of course it is. Every black object in the world reflects some light.
You are confusing black bodies, an abstract notion defined by physiscists which does not exist in the real, physical world, and the color black, which our eyes percieve just fine whether or not it is a shiny surface with a lot of reflection, or a matted surface with minimal (but still greater than zero) reflection. The black BMW I had the misfortune of following the other day positively glinted in the midday sun.
With light, black is defined as the abscence of color. With pigment, black is the presenece of all color (analogous to white light).
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'but Sony knows how risky it is to play "exclusive" in the market and make things incomatible from rest of the world'
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It seems like a feasible variation, at least to me -- keep the mostly-black coating to absorb nuisance ambient light, but allow transmission at narrow RGB wavelengths. Then backlight it with an LED screen, with the diodes tuned to the three transmission frequency ranges.
Don't know whether it's technically possible, but if it is, I bet it's in the works already.
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