NOTE: Although the CRT video projector option is no longer available for general consumer use, it is still used in some commercial and industrial settings, and many older units are still in operation, which is why it is being covered in this section.
The CRT Projector (Cathode Ray Tube)
When video projectors first arrived on the scene, television technology was based on the Cathode Ray Tube (CRT), on which the viewer sees the television image. Three small CRTs (one for each primary color), coupled with a light magnifying lens, can project a color image onto a large screen in a darkened room. With the proper video processing circuitry, CRT size, and lens combination, a CRT projector can produce excellent high resolution images.
Advantages Of The CRT Video Projector
1. The image in a CRT projector is scanned with an electron beam (just as in regular tube TV) and is not limited to a fixed pixel field, as are other video projector types (to be discussed, in more detail, later in this article). This makes the CRT projector the best option where the flexibility of displaying variable resolutions is the main consideration.
2. A CRT projector can produce the blackest blacks of all projector types as well as the full range of color, giving a CRT projector the ability to project the most film-like images of projectors for home use.
3. In addition, another advantage of the CRT projector is its long projection life (as long as 20,000 hours), compared to other types. With LCD and DLP video projectors (described on the following pages) the light source must be replaced every 1,000 to 2,000 hours to maintain optimum brightness and contrast. This amounts to an added regular expense of several hundred dollars every two years or so, depending on usage.
Limitations Of The CRT projector
1. A CRT projector is, typically, very large. In order to house the optimum CRT and lens size combination to project onto a large screen, with enough brightness, a CRT projector can take up as much space as a 20-inch TV (tube facing down). This makes it less portable if you need to travel with it or place it in another room.
2. A CRT projector, typically, is not as bright as other types of projectors. The ability to have a completely dark room is necessary.
3. A CRT projector has to be converged properly for best image reproduction. Since the modern CRT projector houses three projection tubes (red, green, and blue), the tubes need to be aligned so that the projected image does not exhibit color halos and the colors are mixed correctly. Also, if one projection tube fails, all three have to be replaced in order to provide the correct color and brightness balance.
4. A CRT projector is, typically, very expensive. All things being equal, A CRT projector will command a much higher price that other types of video projectors, basically $10,000 on up for a suitable home theater CRT projector unit.
Continue on to Page 3: The LCD Video Projector - by clicking on the link below right.
