| 摘要 |
An optical head (30) comprises a blue-violet laser light source (1) for emitting a blue-violet laser beam, a mirror with a diffraction grating (5) for transmitting and reflecting the blue-violet laser beam at a predetermined ratio, and a front monitor sensor (24) for receiving transmitted light or reflected light from the mirror with a diffraction grating (5) and creating an APC signal for controlling an output of the blue-violet laser light source (1). The minor with a diffraction grating (5) includes a first surface (5a) which the blue-violet laser beam enters, and a second surface (5b) facing the first surface (5a). The first surface (5a) and the second surface (5b) are mutually parallel. A reflecting coat for transmitting and reflecting the blue-violet laser beam at a predetermined ratio is formed on the first surface (5a), and a diffraction grating is formed on the second surface (5b). According to the foregoing configuration, the laser power of the laser beam that is emitted from the light source can be accurately controlled.
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