Light power control circuit for a semiconductor light-emitting e

Details Light power control circuit for a semiconductor light-emitting e Light power control circuit for a semiconductor light-emitting e

1990-06-19

1991-10-22

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

369116, G01J 132

Patent

active

050597809

ABSTRACT:
A light power control circuit by which a stable writing without any influence of a high-frequency current on writing data is enabled by performing superposition of the high-frequency signal on a drive current of a laser diode only during a reading mode, and by inhibiting the superposition of the high-frequency current during a writing mode. In a further embodiment having a construction in which a writing drive current is superposed on a reading drive signal in the form of pulses and a voltage proportional to a writing power is subtracted from an error signal in a servo system, an influences of a writing data component on the operation of the servo system is eliminated by effecting a level shift to the voltage by a predetermined level and subtracting the voltage after the level shift from the error signal.

REFERENCES:
patent: 4692606 (1987-09-01), Sakai et al.
patent: 4787078 (1988-11-01), Yokogawa
patent: 4894525 (1990-01-01), Kakuta

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