Optical recording and reproducing equipment

Details Optical recording and reproducing equipment Optical recording and reproducing equipment

1985-09-13

1987-03-17

Psitos, Aristotelis M.

Dynamic information storage or retrieval

Control of storage or retrieval operation by a control...

Mechanism control by the control signal

250201, G11B 700

Patent

active

046513140

ABSTRACT:
The light beam from a semiconductor laser that generates laser light for recording or reproducing is irradiated onto a disk through an objective lens and the light reflected from the disk is received by a four quadrant light detector with four light receiving areas. Based on the light received by the light receiving areas, first and second feedback signals are generated and fed to servo actuators to control the objective lens in tracking and focusing. These signals are supplied to the actuators for tracking and focusing through switches to apply the tracking servo and focusing servo functions. When there is any change in the total quantity of light received by the light detector, the loop gain of the servo system is kept constant by controlling the duty ratio of opening and closing of the switches by means of control signals which have a frequency sufficiently higher than the response frequency of the feed back signals, thereby intermittently turning on and off the servos in a variable duty cycle that compensates for the change in light quantity.

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