| 摘要 |
PURPOSE:To simplify the control of a photodetector and other optical systems and at the same time to reduce the selection standard of a semiconductor laser, by using a tracking error signal to correct a focus error signal. CONSTITUTION:The outputs A and C, B and D, A and D and B and D are supplied to adding amplifiers 11, 12, 22 and 23 respectively among those outputs A-D of photodetecting elements 10A-10D of a 4-split photodetector 10. Then the sum outputs of amplifiers 11 and 12 and 22 and 23 are supplied to differential amplifiers 13 and 24, respectively. A focus error signal epsilon=(A+C)-(B+D) and a tracking error signal epsilont=(A+D)-(B+C) are delivered from amplifiers 13 and 14, respectively. The signal epsilon and signal muepsilont given from an amplifier 25 of a gain mu are sent to an adding amplifier 26. Thus a corrected focus error signal epsilon0 and signal epsilont are delivered to terminals 14 and 27, respectively. As a result, the control is simplified for the detector 10 and other optical systems. At the same time, the selection standard is reduced from a semiconductor laser which serves as a light source. |
