| 摘要 |
PURPOSE:To reduce the polarization dependency of a diffraction efficiency, to miniaturize the subject device and to make it thin as a whole by providing a 1/4 wavelength board between a luminous flux division means and a recording medium and providing a light deflection/shaping means immediately before an objective lens. CONSTITUTION:The luminous flux division means 4 is provided between a collimator means 4 and the recording medium 10, and the 1/4 wavelength board 5 is provided between the luminous flux division means 4 and the recording medium 10. The parallel luminous flux is deflected in the direction of the optical axis of the objective lens 3 and a beam form is shaped in circular, for example, in the light deflection/shaping means 9. Consequently, an optical system in a level before the beam is shaped, namely, a series of fixed optical system such as a light division means 6 for reflecting light, an autotracking control detection system 7, an autofocusing control detection system 8 is made flat. Thus, the optical head device can be miniaturized and it can be made thin as a whole. |
