| 摘要 |
<p>An optical head device (100) has an optical means which is disposed on a side of a light source rather than that of an objective lens (106) to change the height of an image incident on the objective lens (106), and the optical means includes a concave lens (111) and a convex lens (112). The objective lens (106) is designed to cause a coma aberration with a predetermined polarity when the optical axis of the incident light is inclined to a predetermined direction. When a disc (107) is inclined, the convex lens (112) is moved in a plane perpendicular to the optical axis to change the height of the image incident on the objective lens (106) and the optical axis of light projecting from the convex lens (112) is inclined with respect to the optical axis of the light incident on the concave lens (111). Since the objective lens (106) causes the coma aberration with the polarity reverse to that of the coma aberration caused by the inclination of the disc (107), the former coma aberration cancels the coma aberration caused by the inclination.</p> |
