If you run the light through two identical LCD panels instead of one, I think the contrast ratio would improve drastically.
Here is my reasoning:
Say half the lcd screen is white and the other half black, and lets say our LCD screen has a contrast ratio of 100:1
With one LCD, 100% of the light coming through the white portion will be transmitted to the wall, and 1% of the light coming through the black portion is transmitted to the wall (depending on the contrast ratio of course)
Now lets say that the light goes through a second LCD.
After the light has gone through the second LCD, and is now on the wall, the 100% of the light from the white portion of the LCD will be on the wall, and 0.01% (1 percent of 1) of the light coming from the black portion of the screen will be on the wall.
With those hypothetical numbers, if I'm thinking about this right, we would now have a gross contrast ratio of 10,000:1 🙂
But I assume you would need a very powerful bulb to do this.
Maybe somebody who has 2 panels can try this little experiment?
Here is my reasoning:
Say half the lcd screen is white and the other half black, and lets say our LCD screen has a contrast ratio of 100:1
With one LCD, 100% of the light coming through the white portion will be transmitted to the wall, and 1% of the light coming through the black portion is transmitted to the wall (depending on the contrast ratio of course)
Now lets say that the light goes through a second LCD.
After the light has gone through the second LCD, and is now on the wall, the 100% of the light from the white portion of the LCD will be on the wall, and 0.01% (1 percent of 1) of the light coming from the black portion of the screen will be on the wall.
With those hypothetical numbers, if I'm thinking about this right, we would now have a gross contrast ratio of 10,000:1 🙂
But I assume you would need a very powerful bulb to do this.
Maybe somebody who has 2 panels can try this little experiment?
The losses would be very great, and you should rephrase the question to "..who has 2 identical panels + a pj that has par. light going through the panel... 🙂
But Light loss is a problem that can be dealt with...
Just geta beefyer bulb
This guy improved his contrast ratio with filters:
http://www.myhometheater.homestead.com/filters.html
Just geta beefyer bulb
This guy improved his contrast ratio with filters:
http://www.myhometheater.homestead.com/filters.html
hmm I have 2 identical panels..trouble is I'm short one cable at the moment. 12.1 inch 800x600 350:1 contrast. When I get a few extra bucks scraped together I'll order another cable and give this a try.
zardoz
zardoz
silveradoking02 said:
Sorry...you need an LCD controller card for my panels. The LCD is the "cheap" part of the equation...about 60.00 bucks US...cable about 15 bucks...LCD controller?...135 bucks (if you are an OEM)
zardoz
well Guys I just tried the 2 panel thing using 2 telex m2x's and the problem is One panel works fine on a 4000 lumen projector but as soon as I put the second one on top the brightness was reduced to ZERO, I put my hand 6 inches away from the projection head and could bairly see any light in a pitch black room, So if you think your gonna do this and be able to have anything above 300 ansi its preaty much a bust, Unless you have yourself a rewired outlet to accept 2 1,000 watt MH, and that just sounds to freaky to Imagine. so who knows mabe this will be some use to u all.
isn't polarized light got twisted after passing the first panel? it might be totally blocked by the polarizer film on the second panel. That may be the reason why two panels produce zero light.
two video projo
did anyone try with two videoprojo?
yes i know, it takes place, it's hot and hard to tune the image but..
i'm new on this forum and i'm asking all this questions to myself so don't shout on me please
bye and thanks to all of you to make this forum
did anyone try with two videoprojo?
yes i know, it takes place, it's hot and hard to tune the image but..
i'm new on this forum and i'm asking all this questions to myself so don't shout on me please
bye and thanks to all of you to make this forum
If the light is being polarized before it hits the second LCD, then put a piece of scotch tape somewhere in between the 2 LCDs
Plastic will rotate the light waves 90 degrees and therefore the light will pass through the second polarizing filter
Plastic will rotate the light waves 90 degrees and therefore the light will pass through the second polarizing filter
"Plastic will rotate the light waves 90 degrees and therefore the light will pass through the second polarizing filter"
I think some light will pass that way, but scotch tape is not a precision retarder.
Would it not be possible to just flip the second lcd over?
The polarization of the light after the first panel would match the polarizer of the second panel.
I think some light will pass that way, but scotch tape is not a precision retarder.
Would it not be possible to just flip the second lcd over?
The polarization of the light after the first panel would match the polarizer of the second panel.
LCD panels contain a polarizing filter, so right off the bat about half of the light is filtered out when it passes through. So going through the first panel, no more than 50% or so will go through, then there are losses due to transmission through the panel.
On the other side, black pixels block pretty much all the light, due to the polarization of the pixel being almost perpindicular to the filter.
So by putting another panel in front of your first, you may minimally be darkening the black, but DRASTICALLY reducing the white. So in the end you'd be not only decreasing the contrast, but making everything so dark it'd be impossible to see from a fair range.
Good idea, but you forgot to factor in the inherent inefficiences of LCD panels.
On the other side, black pixels block pretty much all the light, due to the polarization of the pixel being almost perpindicular to the filter.
So by putting another panel in front of your first, you may minimally be darkening the black, but DRASTICALLY reducing the white. So in the end you'd be not only decreasing the contrast, but making everything so dark it'd be impossible to see from a fair range.
Good idea, but you forgot to factor in the inherent inefficiences of LCD panels.
exactly! if you've ever been to a store where they have polarized glasses you can test it out there! You put two polarized lenses next to each other and you can't see throught them, but then you twist one of them about 90 degrees and light passes through, you might want to try twisting the lcd around while it's on top of the other lcd, maybe light will pass through!
Guys, the test for this is with a solid white image or maybe a checkerboard pattern with large blocks. any information in the image is likely to be greatly reduced due to misalignment of individual pixels. A large-featured pattern would let you know generally if it might work, but small features could be misaligned by maybe a half-pixel and you'd never see much of anything with 350:1 x2 panels going against each other!
if you take a look at this link you will get an explanation why this can't work...
http://www.iap.uni-bonn.de/P2K/laptops/laptop_screen.html
it is in german though but i think it is self explaining...
this thing shows a dot with its subpixels in a lcd display
the first polarisation filter only lets perpendicularly polarized light pass through...
if the liquid crystal is switched on, the light is not turned with 90° so the second polarisation filter blocks it, becaue it is mounted 90° turned to the first filter... and so no light will pass through
if the liquid crystal is switched off, it has the effect to turn the light by 90° so the light can pass through the second filter and the pixel and by the combination of the three subpixels u'll get every color
that's how lcd displays work...
conclusion is... it is not possible to use 2 lcd s for better contrast, because the light in this example is polarized horizontal after the second polarization filter... in every lcd display the pl light will come out 90° turned to light that went in... all polarization filters are mounted 90° turned to each other, otherwise an lcd would not work...
and if you put another display over this, no light will pass through, because only perpendicularly polarized light will pass the first polarisation filter but all you have is horizontal pl light...
now you know, why it doesn't work...
http://www.iap.uni-bonn.de/P2K/laptops/laptop_screen.html
it is in german though but i think it is self explaining...
this thing shows a dot with its subpixels in a lcd display
the first polarisation filter only lets perpendicularly polarized light pass through...
if the liquid crystal is switched on, the light is not turned with 90° so the second polarisation filter blocks it, becaue it is mounted 90° turned to the first filter... and so no light will pass through
if the liquid crystal is switched off, it has the effect to turn the light by 90° so the light can pass through the second filter and the pixel and by the combination of the three subpixels u'll get every color
that's how lcd displays work...
conclusion is... it is not possible to use 2 lcd s for better contrast, because the light in this example is polarized horizontal after the second polarization filter... in every lcd display the pl light will come out 90° turned to light that went in... all polarization filters are mounted 90° turned to each other, otherwise an lcd would not work...
and if you put another display over this, no light will pass through, because only perpendicularly polarized light will pass the first polarisation filter but all you have is horizontal pl light...
now you know, why it doesn't work...
here is a way it might work though...
put zelophan foil between the two lcd s because this will cause the horizontal light from the first lcd turn again by 90° and so it will pass through the second lcd again...
this is theorie, i don't know how much light is left behind the first lcd but it will be more light than right now without the zelophan foil...
may be you give it a try and let us know...
put zelophan foil between the two lcd s because this will cause the horizontal light from the first lcd turn again by 90° and so it will pass through the second lcd again...
this is theorie, i don't know how much light is left behind the first lcd but it will be more light than right now without the zelophan foil...
may be you give it a try and let us know...
Has anyone heard of a circular polalizer? I know they exist but I don't know where to find them or how much they cost but it might work with what we're talking about here. There are classic demos of polarization: 2 straight polarizers spinning against each other the light gets dark when they're 90 degrees from each other and bright when they are 0 degrees or alligned. The second is to take two polarizers and lay them 90 degrees to each other so the image is dark then stick a 3rd one in between them and you can see through it again if you rotate it with respect to the first one up to 45 degrees for brightest image, (like the scotch tape). Now let's say you have two 90 degree polarizers. You can stick a circular polarizer between them and it doesn't matter what angle you put it at you get light coming out of the filters always. This is not a diffuser it's sort of an "unpolarizer" though technically it's not. The effect is you get much more light output with this arrangement then with a straight polarizer tilted at 45 degrees.
Uh, do you have to worry about phase?
If so, you might need to go -90 degrees or +270, if you even know which way you went twisted in the first place.
If so, you might need to go -90 degrees or +270, if you even know which way you went twisted in the first place.
No I don't believe phase is an issue. Turn one +90 or -90 with respect to the first and you get the same effect.
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