In a zero-persistence television display, such as one employing a deflected laser beam or injection luminescent diodes, the “on” time per picture element is determined solely by the system’s finite resolution and is about 120 nsec under current standards, as compared to 60-μsec persistence to 10% of initial luminance for a conventional cathode-ray-tube television display. Therefore, at a given luminance level, much higher peak luminances are encountered in the zero-persistence display. An experiment was performed to see if reasonable approximations to these two types of displays had equal averaged photometric luminances when adjusted for equal subjective brightnesses—i.e., does the Bunson–Roscoe luminance–time reciprocity law hold under these conditions?
One half of a television picture was displayed on a cathode-ray tube with 120-nsec decay to 37% of initial luminance; the other half was displayed on a television phosphor whose decay under these conditions was 40 times as long, or about 5 μsec. The viewer was asked to match the two halves for brightness and this match was checked with a photometer. The display covered a 12×14 degree rectangular field of view under simulated home-viewing conditions. Tests were run at approximately 110 and 340 candelas per m2 (33 and 100 ft-L) highlight luminances, with both a standard blank television raster and an Indian-head test pattern. No significant departure from reciprocity was noted under these conditions. A 95% confidence interval of 6% on the raster tests and 13% on the Indian-head-pattern tests was attained.
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