Cathode Ray Tube Design

Cathode ray tubes were the primary electronic information display device for over half a century. Even today they remain dominant as the picture tube in television receivers. Moreover, much of the world continues to use them as computer monitors. The secret to their success is their amazing flexibility and their low cost. They can be made in almost any size, with screens ranging from .5 inches to 50 inches. They can display an immense amount of information per second. Some CRTs can display 12 million pixels, with each pixel carrying 64 levels of gray at a refresh rate of 70 times per second.

Cathode ray tubes come in two basic types - monochrome and color. Color tubes generally have three electron beams that are deflected magnetically and impinge on three different colored-light-producing arrays of phosphor dots. These types of CRTs are designed to produce video images. Their main use is in televisions and computer monitors. The monochrome, or single color, tubes were used in measurement devices such as oscilloscopes. They generally used electrostatic deflection because of its ability to scan the electron beam very quickly across the phosphor screen. They were also used in high resolution medical monitors.

Oscilloscope makers now use low speed flat displays, and acquisition of data is no longer at the CRT but to high-speed memory. It is then displayed at normal video rates to the display device.

Most cathode ray tubes that we build now are for specialized research applications where high-speed events must be displayed in real time. Also, we have seen interest in CRTs with diode arrays or laser arrays replacing the normal phosphor screen.

These applications fit well into our interests and capabilities because we are basically research and development specialists.

Also, we offer rebuilding and repair of cathode ray tubes in cases where customers have expensive or irreplaceable systems and their display or monitor is not working.

Many of the techniques for building CRTs can be adapted to other devices. For example, the CRT technique of using molten glass rods to align, fasten and insulate a multiplicity of electrodes is a very inexpensive way to build prototypes. The alternative is metalized ceramic rings and metal parts brazed together. This is far more expensive.

As an example, we have built klystrons and traveling wave tube prototypes using this procedure at a fraction of the normal cost. Two CRTs are shown on the Capabilities & Terminology page.

If you have an application that involves cathode ray tubes, we hope to hear from you.

Copyright 2005, ebeam, Inc.