CRT (cathode ray tube)

A CRT (picture tube ") is a specialized vacuum tube in which images are created when an electron beam travels up and down along the rear of a phosphor coated screen. Each time the beam passes through the screen lights up a horizontal line of  points of phosphorus inside the glass tube. To quickly draw hundreds of these lines from top to the bottom of the screen, you create the images.

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.

In general, rear-projection displays and LCDs require less power per display area, but plasma displays consume as much as or more than CRTs Televisions regular "direct visualization" that most people have used a large picture tube, while the CRT rear-projection TVs and use three CRT front: the red, blue and green each.

Because CRT (cathode ray tube) projectors does not have a fixed number of pixels, it is more versatile in terms of creating a
clear image at any resolution. One downside to the CRT projector is that it will require occasional calibration. This is a difficult and technical task, which must usually be done by a serviceperson.