Abstract :
This paper describes an experimental amplifier for light which uses a photoconductive layer electrically in series with an electroluminescent phosphor layer. With the series combination excited by an alternating voltage of audio frequency; e.g., 400 cps, a low light level impinging on the photoconductor decreases its resistance sufficiently to cause a much larger light output from the phosphor. Large-area light-amplifying panels, 12 inches square, using a newly developed photoconductive CdS powder have been built. These panels are capable of producing intensified half-tone images with high resolution. The response time of these panels, determined basically by the photoconductive material, varies from 0.1 second to several seconds. New photoconductive materials offer promise of greatly increased speed. Since the photoconductors can be made sensitive to X-rays and infrared, the principles of the device may be useful for image conversion and intensification with these radiation sources.
