| 摘要 |
PURPOSE:To facilitate assembly and adjustment by detecting the light emitted from plural plates, driving a focusing means by the detection signal thereof and controlling the focal point of the light converging on a recording medium. CONSTITUTION:A signal is detected by using the light emitted from the plural plates 18, 19 focusing the light emitted from a light source 11 on a recording medium 1 by using a focusing means, being provided in the light path of the light emitted from this recording medium 1, being arranged by having a different angle for the plane vertical to an optical axis mutually and branching the optical beam in plural nearly parallel optical beams. The focusing means is then driven based on the detected signal and the light focal point converged on the recording medium 1 is controlled. The effect of the displacement of an optical part is thus prevented and the optical diameter for controlling a focal point with easy positional adjusting is easily composed. |
