| 摘要 |
PURPOSE: To eliminate the effects of pattern noise on focusing error signals also in a split-optical system by generating focusing error signals by taking the difference between the signals generated by two detectors. CONSTITUTION: A beam 34 reflected by the surface of a medium is split by a beam splitter 32 into a first- and a second-output beam 36, 38 and then converged respectively by two lenses 40, 44 different in focal length. And respective detectors 42, 46 are arranged in the region where the beams 36, 38 are being converged so that the K values or the heights of the peripheral rays of the beams 36, 38 at the detectors 42, 46 are identical. And the outputs generated by the detectors 42, 46 are impressed on a differential amplifier 48 to output focusing error signals from the amplifier 48. |
