| 摘要 |
PURPOSE:To eliminate the losses of the light power radiated to a recording medium by holding the control signal up to the synchronizing section of the next time so that the reproduced signal in the horizontal synchronizing section becomes of the specified value and controlling the reproduction light power. CONSTITUTION:A feedback loop is so formed that the reproduction light power of a light modulator 2 is maintained at the specified intensity by the increase or decrease of the reproduction light power from the reference voltage B corresponding to the horizontal synchronizing frequency detected with a differential amplifier 19 and the amplitude of the horizontal synchronizing section H of the image signal read from a disc 9. In the sections other than the horizontal synchronizing section, the output of the amplifier 19 at the final of the horizontal synchronizing section is held in a voltage holding circuit 21 to define the reproduction light power of the output of the modulator 2. Since the spacing of the horizontal synchronizing section is extremely short, the drift of the reproduction power is eliminated. If the tracking servo becomes likely to deviate during signal reproducting, the amplitude of the reproduced signald becomes small and therefore the reproduction power becomes larger than the light power at the normal time, causing the gain of the tracking servo loop to increase automatically and the tracking servo to return to the original stable state. Thereby, the losses of the light power may be eliminated. |
