| 摘要 |
PURPOSE:To suppress the apparent tracking error amount to be small by providing a wedge-shaped prism at the front stage of an object lens so that a incident plain and light emitting plain are inclined to a luminous flux, and constantly making the center of the luminous flux go through the rear focus of the object lens. CONSTITUTION:An oblique incident system which makes a luminous flux 105 made incident to an object lens 13 by inclining it to the optical axis of the object 13 is adopted, the incline angle direction is changed by turning a wedge- shaped prism 15 provided at the front stage of the object lens 13, and the focus position to the luminous flux on the optical disk 71 is changed to a tracking direction Tr. In such a case, the sedge-shaped prism 15 is arranged so that a incident plain 15a and a light-emitting plain 15b are inclined to the luminous flux center 150a of an incident parallel luminous flux 105. Thus, the generation of the apparent tracking error amount can be controlled. |
