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. 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."
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Advantages and disadvantages
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.
- Images are free of raster lines, as opposed to LCD projectors.
- CRT projectors do not show a "rainbow" effect. Some people see such an effect when using DLP projectors.
Disadvantages
- Tends to be bulky and somewhat heavy (and non-portable) due to the CRTs.
- Suffers from being undervalued in today's home theater market when compared to smaller and simpler LCD and DLP units.
- Focusing is not even on older systems without good setup, again due to the way the image is projected and requires sophisticated circuitry to compensate--- now found on newer generation CRT projectors for quicker setup.
- Requires more time to set up and adjust for a good overall image for older CRT projectors from the 1970s and 1980s.
- Costlier than other types of CRT tubes for replacement (even though the tube life, rated in tens of thousands of hours, is extremely long).
See also
External links
- CRT Projector Primer/FAQ Find out why CRT Projectors are still used in home theaters where image quality is paramount.
- CRT Projector Manuals & Setup tips Hundreds of manuals and pictures showing board level controls and adjustments for the most popular projector models including Barco, NEC, Electrohome, Sony, Ampro, Zenith, etc.
- CRT Projector Discussion Forum A forum to ask CRT projector questions from other enthusiasts and technicians.
