CONTROL OF OPTICAL INFORMATION REPRODUCER

摘要

PURPOSE:To perform quick and effective control for changes in reflectance and transmissivity due to injuries of a recording carrier, by modulating the light quantity of a light source with a prescribed modulation frequency and controlling the DC bias of a position control means so as to minimize the modulation frequency component of a light source modulating means among the error signals. CONSTITUTION:A changeover switch 23 is switched to select a secondary error signal. Then an offset control means 9 sets the sum of the 1st offset component which varies by the change of light quantity and the 2nd offset component which has no variation with the change of light quantity at zero. The relative position error is set at the minimum level. Under such conditions, the light quantity of a light source 3 is modulated by a light source modulation means 21 with a prescribed frequency. Then the modulation component contained in the error signal is detected by a modulation component detecting means 22 and set at zero with control of a balance control means 7. When the relative position error is minimized with said control, the error signal contains no 1st offset component. Then the switch 23 is switched again to detect the modulation component contained in the error signal through the means 22. Then the means 9 is controlled to set the modulation component at zero. Thus the 2nd offset component is also set at zero.