| 摘要 |
PURPOSE:To prevent crosstalk between tracks adjacent to each other on a disk recording surface without using an apotized filter by specifying the number of apertures of a collimator lens for collimating a laser beam from a semiconductor laser. CONSTITUTION:The number of apertures NA of the collimator lens 3 is settled in a range of 0.14<NA<0.2. By this method, the distribution of light quantity of the collimated beam passed through the collimator lens 3 can nearly be equivalent to Gaussian distribution. By making this distribution incident upon an objective lens 5, a light quantity level of a spot due to primary diffraction can be lowered approximately similarly to the case of using the apotized filter. Consequently, the crosstalk of the adjacent tracks due to a primary diffraction spot can be eliminated without using the apotized filter. |
