| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical pickup device which can emit laser beam with a small beam diameter without greatly deteriorating the use efficiency of a laser beam. SOLUTION: A phase correcting element 5 has regions 51 to 55 on the incident plane of the laser beam. The regions 52 and 54 have projections, the height d of the projection is about 730 nm, and the thickness of quartz 50 is 0.5 mm. The width of the region 52 is wider than the width of the region 54. The width of the region 53 is wider than the width (diameter) of the region 55, and the width in the direction of the side of the region 51 is wider than the width of the region 53. The optical pickup device has a phase correcting element 5 between a semiconductor laser and an objective lens. |
