Accession Number : AD0492701

Title :   THE PURKINJE AFTER-IMAGE ON SCREENS OF CATHODE-RAY TUBES,

Corporate Author : JOHNS HOPKINS UNIV BALTIMORE MD

Personal Author(s) : Mowbray, G. H. ; Gebhard, J. W.

Report Date : 26 FEB 1951

Pagination or Media Count : 14

Abstract : The Purkinje after-image evoked by the sweep moving across cathode-ray tube screens was investigated. Threshold values for the disappearance of the image at low intensities of retinal illumination were found to vary from 0.61 to 15.5 photons for P-7 and P-11 phosphors. These values are in agreement with those found by Judd (1927) for a stationary light stimulus and Karwoski and Crook (1937) for a moving stimulus of about the same dominant wave length as is characteristic of the phosphors. Threshold values for the high intensities at which the image completely disappears were found to be at about 200-250 photons, when the image loses its complimentary hue and becomes a faint achromatic trace. The threshold at which the remaining image disappears was about 1000 photons. A previous study by Sweet and Bartlett (1948) pointed out an interaction among three variables peculiar to radar operation that control the visual stimulus: bias voltage, pulse-repetition rate and sweep-rotation speed. The investigation of these was undertaken and it was shown that the only critical factor determining the presence of the after-image was the retinal illumination. Bias voltage, pulse-frequency and sweep-speed were interchangeable for the values studied and are important only insofar as they control the intensity of the stimulus. The Talbot-Plateau law was shown to hold for the resultant brightnesses produced by pulses of light of the order of 50 to 100 microsec duration. (Author)

Descriptors :   *AFTERIMAGES), (*CATHODE RAY TUBE SCREENS, CATHODE RAY TUBES, RADAR, PHOTONS, PHOSPHORESCENT MATERIALS, RETINA, ILLUMINATION, LIGHT PULSES, INTENSITY, VISION.

Distribution Statement : APPROVED FOR PUBLIC RELEASE