Efficiency of Picture Projection Systems

The very small fraction of the total lamp output which finally reaches the screen from a projector might lead one to question the design of optical systems of the type now in general use. Nevertheless there does not seem, with present light sources, much chance of radical improvement. For practical purposes efficiency, in the sense of the ratio of screen lumens to total lamp lumens, is of much less consequence than screen brightness and picture quality. The benefit from improved efficiency is not necessarily a brighter picture, but more often the ability to work with a lamp of lower wattage. A designer may be justified in increasing the light wasted within his projector, for the sake of obtaining a proportionately smaller improvement in screen brightness. — Other writers have discussed design from the standpoint of producing the best picture. The present paper is largely confined to the subject of calculating efficiencies for such interest as it may have in showing where the light losses occur. The conclusion is reached that an optical system, designed for maximum screen lumens, is doing well from the efficiency standpoint if it projects to the screen more than 2 or 3 per cent of the total lamp output.

Print ISSN

0097-5834

Published

1945-09

Content type

Original Research

DOI

10.5594/J12837