Projection Television

Projection television, which is simply the projection onto a viewing screen of the picture originating on a cathode-ray tube seems, at present, to be the most practical means of producing large television pictures. — The 2 basic problems of projection television are: (1) the problem of providing a cathode-ray tube capable of producing very bright pictures with the necessary resolution and (2) the problem of providing the most efficient optical system so as to utilize the largest possible percentage of the light generated. These problems were very vigorously attacked over a period of years and the progress made toward their solution has been very satisfactory. — Problem (1) has been solved largely by the development of cathode-ray tubes capable of operating at high voltages. Problem (2) has been solved by the development of a reflective optical system about 6 to 7 times more efficient than a good f/2 refractive lens. The reflective optical system consists of a spherical front face mirror and an aspherical correcting lens. — A handicap of this optical system, for use in a home projection receiver, was the high cost of the aspherical lens. This has been overcome by the development of machines for making aspherical molds and by the development of a process for molding aspherical lenses from plastics. RCA reflective optical systems are designed for projection at a fixed throw and require cathode-ray tubes with face curvatures fixed in relation to the curvature of the mirrors in the system. A number of such systems, suitable for projecting television pictures with diagonals ranging from 25 in. to 25 ft, have been developed.

Print ISSN

0097-5834

Published

1945-06

Content type

Original Research

DOI

10.5594/J14240