| 摘要 |
PURPOSE:To perform accurate detecting operation without receiving the effect of noise, by detecting the defect on the recording surface of a data recording disk on the basis of the output of an adder for adding the outputs of the first and second photoelectric converting elements. CONSTITUTION:The reflected beams from a disk due to beam spots S1-S3 are incident to the photoelectric converting elements 1-3 mounted in a pickup. The outputs of the elements 2, 3 are supplied to an adder 5 consisting of resistors R5-R7 and an operational amplifier OP2 through condensers C1, C2 to be added. This addition output passes through a parallel connection circuit of a diode D, a resistor R8 to become the comparing input of a comparator 7, for example, a switch 6 becoming a closed state at a play time. The comparator 7 generates output when the comparing input level exceeds a reference level V. This comparing output is supplied to a tracking servo apparatus as a detection signal showing that there is a defect due to injury on the recording surface of a disk and used for example, as a control signal for opening each servo loop. |
