| 摘要 |
PURPOSE:To ensure the uniform distribution of the reflected laser luminous fluxes and to improve the automatic focusing accuracy, by setting a cylindrical lens so that the column axis of said cylindrical lens is set orthogonal to the column axis of another existing cylindrical lens. CONSTITUTION:The laser luminous flux sent from a seniconductor laser 1 passes through such optical elements having the astigmatic characters as a cylindrical lens 71 and an element 72 obtained by turning an element 71 and an optical element by 90 deg. within an (xy) plane and is led onto the surface of a detector 8. Here theastigmatic characteristics show a fact that the light of an axis (x) or (y) is converged or magnified and the image forming positions of both axes (x) and (y) are shifted when the optical axis of a lens is defined as an axis (z). Then the focusing signal detected by the detector 8 is led to a driving circuit 9 to drive a lens vibrating element, e.g., a voice coil 10. Both cylindrical lenses 71 and 72 have the same form of spots at points 13 and 14 and therefore have the same focal distance. |
