| 摘要 |
PURPOSE:To increase intervals between light pots on a photodetection surface, to suppress crosstalk between reflected laser light spots, and to increase the diameter of each light spot, by providing a cylindrical concave lens between a recording medium and the photodetection surface. CONSTITUTION:A cylindrical concave lens 29 is provided between a record carrier 14 and a photodetection surface 19d to converge spots 21a, 21b, and 21c of reflected laser light to the photodetection surface 19 so that astigmatism is obtained on the photodetection surface 19d of a photodetector 19 and reflected laser light spot intervals on the photodetection surface are wider than laser light spot intervals on the record carrier 14. Thus, light spots are converged to prescribed positions of the photodetection surface easily to facilitate adjusting operation. |
