| 摘要 |
The optical head device disclosed has a light source (1), a super-resolution filter (3), an objective lens system (12;4a,4b;18a,18b;31;34), a data recording medium (7;77), a reconverging lens system (13), and a photo-detecting system including a photodetector (10). The super-resolution filter (3) provides a predetermined light intensity distribution with respect to the laser light emitted from the light source (1). When the data recording medium is a light reflection type (7), 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 (77), the objective lens system comprises a light converging lens (4a) for converging the light on the data recording medium and a light collecting lens (4b) 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 reconverging lens system (13) is for converging the light from the data recording medium, and the photodetector (10) is for detecting a center portion of a flux of the light reconverged by the reconverging lens system (13). Even when the data recording density becomes high, the deterioration of the reproduced signal can be greatly reduced. <IMAGE> |
