| 摘要 |
PURPOSE: To detect the small change of the propagating angle of a light beam by providing a focus sensitive optical component and a photodetector which generates the signal corresponding to the angle of the light beam. CONSTITUTION: The laser light emitted from a right source 12 is made incident to a beam splitter 16 through a collimate lens 14, circularly polarized by means of a 1/4 wave plate 20 through a beam split interface 18, and focused on the surface of an optical disk 22 through an objective lens 24. The beam reflected by the disk 22 is made incident to a focus sensitive optical component 26 through the lens 24, plate 20, and interface 18, interacts with the element 26, and made incident to a detector 28. The detector 28 detects the intensity difference between two segments 32 and 34 and a differential amplifier 30 generates a focus error signal indicating the amount of the focus error of the system. |
