EIA TEP105-7-A-1987

The purpose of this test is to measure the profile of a line on
the face of monochrome cathode ray tube (CRT) in order to estimate
the resolution capacity of the CRT. Since the display on a CRT
often consists of a series of lines or line segments forming
alphanumeric characters or graphics patterns the line width is an
important parameter in the determination of the resolution. For
this reason, the test method discussed below measures the
horizontal and vertical (and possibly diagonal) profiles of the
lines produced by the electron beam or beams. From these profiles,
the line widths can be determined. Such a test for determining the
size of the CRT spot is the first step in any resolution
calculation. Note that line profiles can also be determined from
measurements of the intensity contours of the CRT spot. This method
of determining the line profile is not discussed in this
document.

The line profile of the CRT spot is dependent on a number of
factors in addition to the focused electron beam distribution at
the screen. Some of these factors are:

1. Electron scattering in the screen and support structure

2. Light scattering due to the granular nature of the phosphor
and the aluminum backing of the screen

3. Saturation of the phosphor

4. Internal reflections and absorption of light in the faceplate
and panels mounted onto the faceplate

5. Optical coatings, etches, etc., on the faceplate or panel

External influences on the resolution of the CRT, including
ambient light, are not discussed in this method. These include the
transfer characteristics of the viewing system, in particular, the
non-linear response of a human observer.

Determination of the resolution of a CRT is a complex problem
which is not completely solved at the present time. The reader is
urged to consult the current literature before making any
conclusions about the resolution of the display.