Title: Densitometer for measuring the density of an optical element such as a film badge

Abstract: A densitometer for providing an output which is a function of the density of a film badge in a photodosimeter system. The light passing through the film badge is received by a photodiode which generates a current signal which is directly proportional to the intensity of the received light. The current signal is converted to a voltage signal, the converting means being biased so that the voltage signal is zero when no light is received by the photodiode. The voltage signal is applied, together with a reference voltage, to a log-ratio circuit which generates an output signal proportional to the log of the ratio of the reference voltage to the voltage signal, the output of the log-ratio circuit being displayed. A circuit is operative, when the film badge is removed from the light path, to adjust the reference voltage until the output of the log-ratio circuit is zero.

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Inventors: Anderson, Robert J. (Villa Park, CA, US)

Application Number: 491876
Filing Date: 1974-07-25
Publication_date: 1976-03-09
Assignee: Beckman Instruments, Inc. (Fullerton, CA)
Primary Class(es): 356/443 250/559.02, 250/559.39
Other Classes:
US Patent Ref:

3765778	Oct, 1973	Bey et al.	356/202.
3807875	Apr, 1974	Fisher et al.	356/201.

Other Refs:
Primary Examiner: McGraw, Vincent P.
Assistant Examiner:
Attorney: Steinmeyer; R. J., Meads; R. R.