| 摘要 |
PURPOSE:To prevent entirely adverse influences to be exerted on a servo signal even when input impedance is made very low to obtain a high S/N for an amplifier for main signal by operating a photodetecting element as a constant current source, separating a servo system and a main signal system by the light detecting element and outputting. CONSTITUTION:Signal current that flows in the direction of the arrow of solid line of main signal detected by photodetecting elements 8a, 8b, 8c, 8d is added by an amplifier 13 for adding and sent to a regenerative circuit due to characteristic that the amplifier 13 for adding is low input impedance type of current feedback. At this time, even when the capacity of a capacitor 12, separation is made perfectly by photodetecting elements 8a, 8b, 8c, 8d. Servo signals detected by light detecting elements 8a, 8b, 8c, 8d are sent to a focus and tracking correction controlling circuit through respective amplifier 15a, 15b, 15c, 15d. The servo signals at this time give no influence to the main signal side. |
