There have been numerous designs over the past five decades, from the first commercial B&W TVs to the current offering of high-definition televisions (HDTV). As much as they change, the fundamentals dating back to 1878 are still there. An electron cloud is formed, metered out through a control grid, accelerated, shaped, and accelerated again before being turned loose in the direction of the phosphor screen. This process uses electrons that prefer to be separated from each other and surrounds them with strong positive fields without pulling them farther apart.
Depending on the task at hand, a set of problems can be approached with different design solutions. A projection system is a very high drive application with moderate sized pixels on a 7- or 9-inch diagonal CRT. A similar 7-inch photographic system has a very low drive and very small pixels. A 5-megapixel 21-inch medical display requires a fraction of the projection brightness, albeit still bright, but over a much larger area, with pixels approaching photographic requirements. The respective electron optics for these systems are not interchangeable.
Color optics parallels the mask configuration in that the shadow mask utilizes the deltoid (triangular) positioning of the cathodes (three beams) while the aperture grill (and slot mask) utilizes in-line (horizontal plane) positioning. Monochrome optics has a single cathode (one beam) that is centered in the gun mount (a term for the total optical package). Two basic types of monochrome gun mount are used and will be treated separately.
For ease of discussion, only the monochrome mount will be used for explanation. The forces working within a gun mount are complex enough with one beam, and compounding the lines of force in a color mount would require an extensive discussion.
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