| 摘要 |
PURPOSE: To provide a device capable of generating a rough focal error signal and an accurate focal error signal related to an optical beam in addition to a position error signal for the focal position of an optical beam on a disk in a magneto-optical information storing system. CONSTITUTION: Reflected light from an optical medium 10 has several reflection degrees 32, 34, 36 and forms a shear interferogram. A light receiving member 26 receives reflected light from a medium 10 turns the reflected light to a detector member 44 and detects the brightness difference of light in an overlapped area generated between the reflection degrees. First photosensitive members 44C, 44D detect the brightness of light on a part of an overlapped area between zero-order reflection and primary reflection and 2nd photosensitive members 44B, 44E detects the brightness of light on the remaining part of the overlapped area between the zero-order reflection and the primary reflection. A comparator compares the detected brightness of a part of the overlapped area with that of the remaining part. |
