| 摘要 |
PURPOSE: To attain high light availability with less loss by setting a size of a diffraction grating area of a circular ring shape smaller than a beam width of an incident beam. CONSTITUTION: The incident beam from a light source l goes straight on in a transparent area 11 of a filter 10, and is diffracted/separated from a straight beam in the diffraction grating area 12, and is light shielded in a light shield area 13 to be converged on an optical disk 7 finally. Since the straight beam is light shielded by both areas of the areas 12, 13 in the filter 10, its light spot is fined by a super resolution effect to be converged. Further, diffracted light beams of (+1st-order light) and (-1st-order light) occurring diffracted by the area 12 are used as the light spots of a three beams system for detecting a track error signal. The light spots are fined in the diffracted light beams also by the super resolution effect. Thus, the detection sensitivity of the track error signal is improved. |
