| 摘要 |
PURPOSE:To reduce primary diffraction light and to suppress the occurrence of crosstalk by degrading the distribution of light transmittance of an object lens of an optical head from the center of the lense in the direction to perpendicularly cross with an information track formed on a recording medium. CONSTITUTION:On the surface of the objective lens 5 of the optical head, a Cr vapor deposited film 10 is formed on both end parts in the direction perpendicularly crossing with a lens axis A in the same direction of the pit string of a disk 6, and its light transmittance is set in a value within the range 30-50%. Thus, the peak values of the primary and haigher diffraction light beams can be suppressed without weakening the zero-order diffraction light. In case of using such an objective lens as the above for an optical head device consisting of a semiconductor laser 1, a halfprism 3, a photosensor 8 and other, the device is disposed in the vicinity of the disk 6, therefore, an error to positional relation is not expanded. Accordingly, along with the effect of the above- mentioned filtering, said effect provides the suppression of the occurrence of crosstalk. |
