| 摘要 |
PURPOSE:To separate a collimation servo signal and an optical data signal without being effected by a light receiving position by connecting an inductance circuit with a 4-quadrant photodetector receiving an automatic collimation servo light so as to extract an optical data signal having a modulation frequency higher than that of a servo light. CONSTITUTION:The inductance circuit 44 showing a high impedance is connected with the light receiving signal of a transmission data light having a high modulation frequency is connected with a current supply terminal of the collimation servo 4-quadrant photodetector 15 and a data signal is extracted from the circuit. Thus, even when the image forming point on the light receiving face is biased to either of the 4-quadrant output, the data signal is obtained without hindrance based on the combined current of the 4-quadrant flowing to the circuit 44. Since the circuit 44 shows a low impedance with respect to the modulation frequency of the collimation servo light, the supply current to the photodetector 15 is not disturbed and the light receiving sensitivity to the servo light is not deteriorated. Thus, a simple device where one objective lens and one photodetector are shared for the collimation servo optical system and the optical data optical system is formed. |
