A New Dichroic Reflector and its Application to Protocell Monitoring Systems

Certain crystals have long been known to transmit light of one color and reflect light of another color. Some thin metallic films also exhibit the same phenomena. By evaporating alternate layers of high and low-index insulators on glass, it is possible to produce a surface having predetermined transmission and reflection characteristics, and having no appreciable absorption. A method of determining the properties of multilayer films is described. — Design details and curves are given for a three-layer film having its peak transmission at 4400 A and its peak reflection at 7920 A. This film is successfully employed in high-level photocell monitoring systems for sound recorders. Nearly all the actinic value of the modulated light is transmitted to the photographic film while a large part of the red and infrared is reflected to a cesium photocell for monitoring.

Print ISSN

0097-5834

Published

1942-01

Content type

Original Research

DOI

10.5594/J09935