Light absorption detector with light emitting and light receivin

Details Light absorption detector with light emitting and light receivin Light absorption detector with light emitting and light receivin

1990-01-16

1991-09-03

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

250214C, G01J 132

Patent

active

050456830

ABSTRACT:
A light absorption detector has one or two light emitting members and a light receiving element spaced a predetermined distance apart from each other on a film substrate (1). Light is transmitted from one side to the other side of a subject. a change in the absorption magnitude of this transmitted light by the subject is then detected to provide respective information. A photodiode (PD) is located near the light emitting member or near two light emitting diodes (LED1, LED2). The photodiode detects a change in the quantity of light emitted. A CPU (16) corrects a change in the quantity of light with a change in the temperature of the light emitting element for controlling the current flowing to the light emitting member or light emitting diodes. Futher, a thermistor (37) and a heater (39) are located in the vicinity of at least one of a light emitting diode (34) and a photodiode (31). A CPU (43) controls a current flowing through the heater in response to a detection of an output of the thermistor so that the temperature of at least of the light emitting member or of the light receiving element is maintained constant.

REFERENCES:
patent: 4182977 (1980-01-01), Stricklin, Jr.
patent: 4431947 (1984-02-01), Ferriss et al.
patent: 4695714 (1987-09-01), Kimizuka et al.
patent: 4701607 (1987-10-01), El-Hanany et al.
patent: 4724314 (1988-02-01), Caimi
patent: 4837428 (1989-06-01), Takagi et al.
patent: 4917031 (1990-04-01), Itoh
Article Entitled "Design Notes" 74, Control and Instrumentation, Jun. 1981, vol. 13, No. 6, London England; p. 17.

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