Abstract

The photoelectric photodensitometer described was developed for determining fine structure from “match-point” spectrum photographs. It consists of a push-pull photo-cell circuit, transformer coupled to an amplifier and cathode-ray oscillograph, and two optical systems with a.c. operated light sources for projecting the spectra onto the photo-cell slit and for forming an image of the wave-length scale which indicates the region of the spectrum being matched. As the projected spectra are moved horizontally across the slit, a change in phase occurs in the a.c. output of the photo-cell circuit on passing through a match point. The corresponding change in oscillograph pattern indicates whether the absorption is increasing or decreasing, and permits true match points to be distinguished from decreases in intensity due to dense spectrum lines in matching line spectra.

© 1939 Optical Society of America

Wide Range Intensity Measurements in Photoelectric Spectrophotometry

Walter C. Bosch and Barremore B. Brown
J. Opt. Soc. Am. 29(11) 466-469 (1939)

An Automatic Spectral-Sensitivity Curve Tracer

T. B. Perkins
J. Opt. Soc. Am. 29(6) 226-234 (1939)

The Response of Several Fluorescent Materials to Short Wave-Length Ultraviolet Radiations

N. C. Beese
J. Opt. Soc. Am. 29(7) 278-282 (1939)

Methods and Instruments for the Determination of Photographic Speeds by Measurement of Relative Characteristic Gradients*

Clifton Tuttle
J. Opt. Soc. Am. 29(7) 267-277 (1939)

A Thallous Sulphide Photo-e.m.f. Cell

Foster C. Nix and Arnold W. Treptow
J. Opt. Soc. Am. 29(11) 457-462 (1939)