Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Patent
1994-12-13
1996-07-16
Westin, Edward P.
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
372 89, 327514, H01J 4014
Patent
active
055369340
ABSTRACT:
A light intensity deterioration detecting circuit which includes a photodiode which receives light from a laser diode and having a cathode connected to a power supply and an anode connected to a first end of a resistor. A reference current source is connected between the power supply and a first input of a comparator which has the first input connected to a first end of a resistor and a second input connected to the first end of the resistor, and which compares a comparison voltage provided at the first end of the resistor and a comparison voltage provided at the second end of the resistor to output an output voltage on the basis of the comparison result. Errors of a resistance ratio are reduced to a negligible level if relatively large errors are produced in individual resistances, thus correctly detecting deterioration of a current to light output characteristic of the laser diode without an offset control.
REFERENCES:
patent: 4096382 (1978-06-01), Numata et al.
patent: 4819241 (1989-04-01), Nagano
patent: 4995105 (1991-02-01), Wechsler
patent: 5163063 (1992-11-01), Yoshikawa et al.
patent: 5285464 (1994-02-01), Ogino
patent: 5309269 (1994-05-01), Shibao
Mitsubishi Denki & Kabushiki Kaisha
Nichols Steven L.
Westin Edward P.
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