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CRT Projectors
A CRT projector is a video projector that uses a small, high-brightness CRT (or picture tube) as the image generating element. The image is then focused and enlarged onto a screen using a lens kept in front of the CRT face. more...
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Most modern CRT projectors are color and have three separate CRTs (instead of a single, colour CRT), and their own lenses to achieve colour images. The red, green and blue portions of the incoming video signal are processed and sent to the respective CRTs whose images are focused by their lenses to achieve the overall picture on the screen. Various designs have made it to production, including the "direct" CRT-lens design, and the Schmidt-CRT, which employed a phosphor screen that illuminates a perforated spherical mirror, all within an evacuated "tube."
Advantages:
Long CRT life, typically that of a normal television picture tube.;
Can achieve good to very good colour resolution, brightness and picture size.;
Once set-up, minimal maintenance is required, unlike projectors that use lamps.;
Superior black level - black is actually black and not dark grey.;
As with CRT monitors, the image resolution and the refresh rate are not fixed but variable within some limits. Interlaced material can be played directly, without need for imperfect deinterlacing mechanisms.;
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Disadvantages:
Tends to be bulky and heavy (and non-portable) due to the CRTs.;
Low maximum brightness levels - the room has to be completely dark and eyes of viewers coming from a daylight environment have to adapt to the darkness for a minute or two before image details can be seen.;
Suffers from uneven colour mixing, since it is done by projecting the individual lines (made on the CRTs) onto the screen. The result is that the picture optimised for the central area of the screen tends to split into the individual colours towards the edges. Sophisticated circuitry is required to compensate for this.;
Focusing is not even, again due to the way the image is projected and requires sophisticated circuitry to compensate.;
Requires more time to set up and adjust for a good overall image.;
Costlier than other types of projectors due to the complex circuitry required to control and synchronise the three CRTs to achieve optimum picture quality. (Although it is easier to get good deals on used equipment than with other types of projectors);
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Read more at Wikipedia.org
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