| 摘要 |
PURPOSE:To decrease a shift of an optical axis due to environmental variations such as a temperature variation, etc., and to detect stably out-of-focus by providing a photodetecting area for detecting light, and a frame made of a metal for supporting this area, on photodetector, and performing an insulation coating to its frame. CONSTITUTION:An information storage medium 21 is placed on a turntable 30, a chuck device 32 is installed to a center spindle 31 of this table 30, and the table 30 is rotated at a prescribed speed by a driving motor 33. In the radial direction of this medium 21, an optical head 34 having a light source 36, an objective lens 40, and the second photodetector 49 is placed so as to be rotatable. A detector 49 of this head 34 is supported by a holder 54, and the detector 49 is formed by a photodetecting area 49 and a frame 56 for supporting it. This frame 56 is formed by a metal, and also by performing an insulation coating, an insulation of the frame 56 of the detector 49, and the holder 54 is performed. In such a way, an optical axis shift of the detector 49 environmental variations such as temperature and humidity, etc. is decreased, and out-of-focus is detected stably.
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