The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 17, 1988
Filed:
May. 13, 1986
Shozi Yoshikawa, Tokyo, JP;
Olympus Optical Co., Ltd., Tokyo, JP;
Abstract
A plurality of supply voltages are supplied form a power supply to a semiconductor laser drive device. One of these supply voltages is applied to a discrimination circuit. The discrimination circuit includes a first zener diode, to which one of the supply voltages is applied, and which has a zener breakdown voltage corresponding to the lower limit of a threshold voltage range, and a second zener diode, to which the same supply voltage is applied, and which has a zener breakdown voltage corresponding to the upper limit of the threshold voltage range. First and second light-emitting diodes are connected in series with the respective first and second zener diodes. Light emitted from the first and second light-emitting diodes is received by respective first and second phototransistors connected in series between a voltage supply terminal and a ground terminal. A resistor is connected in parallel with the second phototransistor connected to the ground terminal. Voltage at the connection point between the first and second phototransistors is applied to the gate of a junction field-effect transistor, which has its drain grounded and its source connected to a control terminal of a switch in parallel with and for shunting the semiconductor laser.