[opendtv] Re: HDMI from STBs

  • From: Jeroen Stessen <jeroen.stessen@xxxxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Wed, 4 Jan 2006 17:18:34 +0100


Donald Koeleman: 
> Bert, what is that magical black projection screen article about, 
> that's listed in the tvp contents on their website?

I don't know which one you are referring to, but I know of a front 
projection screen that Sony is marketing, which is spectrum 
selective to reflect mostly the wavelengths that are emitted by 
the projector lamp. Thus it has high reflectivity for the image, 
and lower reflectivity for the ambient light. One colleague of mine 
thinks that it works only marginally. Another option is to use a 
polarized screen, making use of the fact that the light from an LCD 
projector is already polarized but ambient light is not. 

Rear projection screens are more easy to make black: they use a 
lenticular screen to spread the light horizontally, and thus the 
light comes out of narrow slits. Then the space between the slits 
can be painted black (from the front) with a black matrix. Thus 
the transmittivity from the rear is high, and the reflectivity 
from the front is low. I think that you can always do tricks like 
this if the desired (image) light comes from one point (the lens) 
and the undesired (ambient) light comes from all directions. 

-- Jeroen

| From:     Jeroen H. Stessen   | E-mail:  Jeroen.Stessen@xxxxxxxxxxx |
| Building: SFJ-5.22 Eindhoven  | Deptmt.: Philips Applied Technologies |
| Phone:    ++31.40.2732739     | Visiting & mail address: Glaslaan 2 |
| Mobile:   ++31.6.44680021     | NL 5616 LW Eindhoven, the Netherlands |
| Skype:  callto:jeroen.stessen | Website: http://www.apptech.philips.com/ 

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