Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1990-08-01
1991-11-26
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
250214AG, 356 4, G01N 2186
Patent
active
050685406
ABSTRACT:
A distance measuring apparatus comprises a light emitting device for emitting infrared light blinking at a constant frequency toward an object, and a light receiving device for receiving infrared light reflected from the object. The light receiving device can generate two output signals which correspond respectively to positive and negative amounts of deviation of a position of light received therein with respect to a center thereof. The output signals are amplified by amplifiers, respectively. A signal component having a frequency corresponding to the blink frequency of the infrared light is picked up by a picking-up circuit from each of the output signals of the amplifiers. A distance determining device is provided to determine a distance to the object on the basis of the signal components. A gain control circuit for controlling gains of the amplifiers includes a pair of resistor circuits each having a changeable resistance for determining the gain of the corresponding amplifier. A comparator compares in magnitude one of the signal components with a reference voltage and generates a control signal having modes which change with the difference in magnitude between the signal component and the reference voltage. A resistance changing circuit is operative to change the resistance of each of the resistor circuits in accordance with the modes of the control signals.
REFERENCES:
patent: 4522492 (1985-06-01), Masunaga
patent: 4537510 (1985-08-01), Takahasi
patent: 4601574 (1986-07-01), Yamane et al.
patent: 4768876 (1988-09-01), Okino
patent: 5008532 (1991-04-01), Ono et al.
patent: 5008695 (1991-04-01), Nagaoka et al.
Allen Stephone B.
Nelms David C.
Ricoh & Company, Ltd.
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