| 摘要 |
PROBLEM TO BE SOLVED: To realize highly precise focusing control by improving a correcting lens that generates astigmatism in a return laser beam and thereby reducing the offset quantity of a focusing error signal. SOLUTION: The correcting lens 10 of an optical pickup device is equipped with a first anisotropically curved surface 11 which removes, from a return laser beam L2, an aberration generated from transmission through a half mirror (optical element for optical separation), and with a second anisotropically curved surface 12 which generates, on the return laser beam L2, astigmatism for forming a focusing error signal. The optical axes L11, L12 of respective curved surfaces 11, 12 are inclined relative to the main light beam direction L10 of the return laser beam L2 and made to be slightly eccentric mutually so that the return laser beam L2 is set to pass through the tops 11a, 12a of respective curved surfaces 11, 12. As a result, the generation of the aberration which may increase the offset quantity of a tracking error signal on the return laser beam is suppressed or prevented. |
