| 摘要 |
Members such as a laser diode ( 10 ) that is a light source, a diffraction grating ( 11 ), a polarizing beam splitter ( 12 ) and a collimator lens are arranged in a casing ( 20 ). An optical head device having such a casing ( 20 ) is improved, so that a film wavelength plate ( 14 ) is directly attached to the casing ( 20 ) in a form free from a support substrate. The film wavelength plate ( 14 ) consists of only one film and has a thickness of 0.2 to 1.0 mm. Particularly, the film wavelength plate is preferably constituted by fusing polycarbonate films in a three-layer structure.
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