Luminance Measurement Techniques for Color Television Picture Tubes

There are a number of photoelectric instruments available for luminance measurements on color picture tubes. These fall into two broad categories: (1) Barrier-layer cell type instruments with wide viewing angle and low sensitivity, and (2) Photomultiplier instruments with narrow viewing angle and high sensitivity. Either of these two instrument categories are suitable for simple luminance evaluation of primary fields and white fields. For measurements of small area luminances, contrast and tracking, the photomultiplier instruments are usually more useful. In any event, for any luminance measurement, care must be taken to maintain: (1) Proper operating voltages and currents on the tube, (2) Constant raster size for comparison measurements, (3) Purity of fields for primary measurements and proper white color for white fields, and (4) Appropriate picture content and ambient light levels for contrast measurements. If all these conditions are fulfilled, accurate, reproducible luminance measurements may be expected from any of the instruments discussed.