and i would like to add in the technical details for the technically curious, partial copy and paste from my recent reply:
an lcd works by polarizing the light into horizontal and vertical wavelengths. there is a simple science experiment that can be where you can take one horizontal polarizer and shine a light through it and see horizontal lines shine through, as you would expect. then do this again but with a vertical polarizer, you see vertical lines shine through. now add these two together and what do you get? the two filtering out both the vertical and horizontal wavelengths, leaving no light. now, here is where the liquid crystal comes in, it sits between these two polarizers. the liquid crystal is bifrengent when current is passed through it (it twist) and in turn rotates the light and allows it to pass through the second polarizer. however, as it gets untwisted less and less it rotates the light less and allows the second polarizer to block the light more and more. fully untwisted it allows the light to be blocked by the second, vertical, polarizer.
now, for single lcd panel designs there are simply subpixels with different color filters. for 3 panel lcd designs there are three black and white/colorless panels where white light is shined through equally. but before the light reaches the lcd panels it passes through a different color filter for each panel, one filtering all colors out except for blue, another green and another red. after colored light passes through each panel it is then reconverged back into a single, aligned, beam and is then projected through a lense and onto the projection surface.
so, when a polarizer goes bad for a particular lcd color panel that light is not blocked when it should be. there for disrupting the process of either blocking certain colors to reproduce another color, or producing blacks. whites are least affected since white is produced by all light passing through.
there are different types of polarizers, some organic and some metallic based. previously it was felt that the metallic ones were not practical so the organic, photofilter ones were used. even so some manufacturers still did use non-organic polarizers in the past in some models, but this was a rarity.
so if you see splotches it may be an organic polarizer going bad.
some examples of the problem (taken from various bigscreenforumers when posting their problems):
Picture 1Picture 2[Edited by jarrod1937 on Apr 3, 2007 at 1:21:21 PM]
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- Now I'm the one that get's to say "I mean no disrespect", but this post seems rather Anti-DLP and very Pro-LCD. I'm just saying ya know.
