Abstract

The 1940 Applied Research Laboratories’ projection comparator-densitometer, using spectrum plates either 2″×10″ or 4″×10″, provides dual projection of a sample spectrogram and a master onto a translucent screen mounted directly before the operator. Using a slit system that moves into contact with the plate; a vacuum photo-cell, a two-stage compensated amplifier, and sturdy ammeter, the comparator-densitometer provides transmission readings on any spectral line, accurate to a few tenths of a percent. The unit is fast in operation allowing the operator to read easily as many as six lines per minute. Operating from 115-v, 60-cycle power supply, it achieves this accuracy with the minimum amount of care and upkeep.

© 1941 Optical Society of America

A New Nonrecording Densitometer*

W. S. Baird
J. Opt. Soc. Am. 31(2) 179-180 (1941)

A New Projection-Comparator Microphotometer

J. T. Rozsa and C. G. Moon
J. Opt. Soc. Am. 44(7) 562-565 (1954)

Precision Densitometers for Photographic Photometry

George R. Harrison
J. Opt. Soc. Am. 10(2) 157-167 (1925)

An Automatic Recording Photographic Densitometer*

George Barnes
J. Opt. Soc. Am. 43(12) 1176-1180 (1953)

Final Measurements of the Velocity of Light

Wilmer C. Anderson
J. Opt. Soc. Am. 31(3) 187-197 (1941)