| 摘要 |
The optical head device disclosed has a light source, a super-resolution filter, an objective lens system a data recording medium, a reconverging lens system, and a photo-detecting system including a photodetector. The super-resolution filter provides a predetermined light intensity distribution with respect to the laser light emitted from the light source. When the data recording medium is a light reflection type, the objective lens system is both for converging the light on the data recording medium and for collecting the light reflected therefrom and, when the same is a light transmission type, the objective lens system comprises a light converging lens for converging the light on the data recording medium and a light collecting lens for collecting the light transmitted through the data recording medium. The objective lens system has a numerical aperture larger for the light collecting than that for the light converging. The re-converging lens system is for converging the light from the data recording medium, and the photodetector is for detecting a center portion of a flux of the light reconverged by the reconverging lens system. Even when the data recording density becomes high, the deterioration of the reproduced signal can be greatly reduced.
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