The 3 types of front projectors....

Discussion in 'Displays' started by todd s, Jun 3, 2004.

  1. todd s

    todd s Lead Actor

    Jul 8, 1999
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    Can someone give me a quick rundown of the 3 different types of front projectors (CRT,DLP,etc)??

  2. Allan Jayne

    Allan Jayne Cinematographer

    Nov 1, 1998
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    CRT Projector -- Has three small picture tubes down inside, one for red content, one for green content, one for blue content. Usually needs to be reconverged at least twice a year. Better contrast than either of the below.

    Tri-panel, typically for LCD -- Has three postage stamp (or film frame sized) fixed pixel panels (display elements), one for red content, etc. and one projection lamp and a series of mirrors and prisms. For LCD the projection beam goes through the panel. About the only disadvantage of LCD these days is a low contrast ratio and blacks are not really black. LCOS (the beam reflects off the panel) offers better contrast since the light goes through each liquid crystal twice, hitting a mirror behind. No convergence problems except once in awhile a set has an incorrigible convergence error; the panels need microscopic alignment and are permanently glued in place.

    Single mono-color panel, typically for DLP -- Has one projection lamp, one postage stamp sized panel and a color wheel whose red frame is in the light beam when the element displays red content, etc. For LCOS or DLP the light beam reflects off the panel. Many people see rainbow fringes because the red, green, and blue sub-images occur consecutively although at minute time intervals such as 1/120'th second eachg.

    Single tri-color panel, I only know of LCD examples -- Has one projection lamp, one panel with side by side red, green, and blue transparent spots over respective pixels in the panel. Tends to give a grainy picture since the pixels are not all that small and I have not seen really high resolution examples.

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  3. ChrisWiggles

    ChrisWiggles Producer

    Aug 19, 2002
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