| 摘要 |
PURPOSE:To facilitate easy optimum adjustment by facilitating adjusting the position of an adjusting carrier which is equal to an information carrier in value, detecting the light reflected from the carrier by plural detectors and making adjustment based upon their sum signal and difference signal and the derivation of the difference signal. CONSTITUTION:A part of an information carrier or an information carrier piece 22 which is equal to the information carrier in value is so arranged as to make adjustment in the direction of depth of focus and also in the direction orthogonal to that direction near a light spot. The output of a transmitter 23 is applied to a biaxial actuator 21 so that the speed at which a recording film 22a of the carrier piece 22 passes through a light spot 18 formed by an objective lens 7 may be kept constant. The outputs of bisecting detectors 13a and 13b are processed into a sum signal and a difference signal by an adder 24 and a subtractor 20, and further, the difference signal is differentiated by a differentiator 31. In this configuration, when the sum signal becomes maximum in focus, the derivation also becomes maximum. So, by monitoring the output of the circuit 31, the position of a convex lens 9 is so adjusted that the output may become maximum. Consequently, optimum adjustment is performed. |
