An optical unit for the measurement of reflection density is described. In conjunction with a sensitive densitometer, optical densities up to 4.0 can be measured with highly selective spectral filtration. The unit utilizes 45° incident radiation with measurement of normally reflected radiation as specified for use with photographic materials. The stray light level amounts to less than 1 part in 100 000, and the unwanted specular radiation to less than 1 part in 10 000. Problems in the design and evaluation of this unit are reviewed.
© 1959 Optical Society of AmericaFull Article | PDF Article
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