As most of us who've finished a projector know, when the LCD is powered up, but has no signal, and the big light is on behind it, we get a "white" screen image projected.

When the LCD panel was in a monitor, and powered, but with no input signal, the screen looks black. It's black, of course because the circuitry turns the backlight off.

What I'm wondering about is if there's a tint film involved. I know that for car windows, a 35% tint film (Allowing only 35% of the light to pass through it) doesn't even seem like a dark film. If the LCD panel uses such a film, it would allow the monitor to appear black when the LCD elements are actually clear, as long as the backlight is off. Otherwise, what you'd get is more like a calculator LCD display. Remember, the backing layer right next to the LCD between the panel and the backlight is white, but obviously not enough light passes back and forth to allow that to be seen.

Obviously there's a light reduction tint film at work, and it's stronger than it needs to be to get the LCD effect. This is not merely the light removed by polarisation, but additional light as well. (Perhaps this is also a part of how commercial projectors get more light onto the screen from a smaller light/panel)

So, the question is: Are there separate polar and tint films, or is the polar film tinted? If the polar film is tinted, might it be possible to replace it with untinted film? (My suspicion is that if the polar film is tinted that it's only the one on the "front" surface of the LCD.) If the tint film is separate, it may be possible to remove just the tinted film, allowing more light to travel through the panel, resulting in a brighter image, possibly even with a reduced wattage light.

Please note: I am not advocating that anyone peel the film from their LCD unless they can afford to wreck it with an experiment which may or may not work!

It may be worth an experiment, though.

Hi, I'm new in the lumenlab arena, but been arround 4 a wile.
About 3 years ago I read in diyaudio that someone striped that film from the lcd, I think with the large posts over there would be imposible to find it again, doesn't come to me a relative kword.

I'm finally starting my projector, it's shipped the 17lcd dell 1000:1 contrast, standar lens from ll, 15.5inch fress from 3dlenss, reflector from ireplica, going to the lighthouse to choose for a bulb today.

I would like to add something, you(the ones that reads this) might think it's very strange or usseless, but...

I need to know what happens if you put a mirror instead of the reflector behind the lamp, almost touching the lamp, then, do you have ANY kind of gain in light output?
Becouse if you do, you allways can use some of the light is loose from the Y axis not beeing directed to the fressnels, puting some tinny mirrors 45degree facing toward the fress(almos touching the lamp)
This might work better whit a lamp smaller in diameter, so you don't go way of axis.

Please if someonce can replace the reflector from behind just to see if there is any gain it would prove something, someone with an Ushio or small format bulb would be better.

Thank you all.

I hope you'll be seeing a lot of me arround here.

The front has an antireflective coating but doesn't effect it much. The biggest losses are in the color filters and a little bit from the indium tin oxide layers. So replacing the films wouldn't make a major improvement. Even with all the films removed the panel still appears dark because of the color filters.

Gustavoya, you wouldn't want to use a planar mirror. Use an aspheric with the standard collimator fresnel design or a large parabolic the size of your LCD without a collimating fresnel. A planar mirror would only create off axis light.

I understand what you say, and my idea is to use a reflector, but what I'm saying is that if someone can try putting a mirror instead of the reflector(the light will be out of axis) and gains ANY lumens, then maybe we can put mirrors in the path of the light that is not used, up and down the y axis of the lamp, and this will sum the already installed reflector.

Polarization films are tinted (they would produce them 100% efficient if they could, but of course passing through the film produces some losses) to the general vicinity of 10-40%.

http://www.3dlens.com/Polarizer.html

This is in addition to the inherent 50% loss from the polarized light.

I just found something out recently proving myself wrong in some cases. A couple months back I won seven Compaq TFT5000's off eBay. All had simple leaky capacitors in the switchmode power supply which caused the power LED to rapidly blink. Anyway I fixed all but two which have a single line unfortunately caused by failing driver IC's on the Flexible Printed Circuit on the LCD.

They are two different LCD's one uses two CCFL's and the other uses four. I decided to strip the polarizer from the front of quad CCFL LCD and found a drastic improvement as they must've gone overboard on the antireflective coating. It may be worth changing polarizers on some LCD's, although I am also not recommending it.

The biggest loss is still through the color filters. You can remove all the films and it still won't appear transparent because of em'. Most LCD projectors use three grayscale microdisplays with a color filter for each. Remove the color filters and have three monochromatic light sources and it'll be closer to that of an lcd calculator.

If I recall correctly, it's been tried before and found to not work. The fresnels need a point source of light; use a spherical reflector. You will buy nothing from a mirror close to the lamp source.