| 摘要 |
A deformable mirror device compensates the spherical aberration caused by the difference of thickness of the cover layers covering recording layers of an optical disc. Circular projections are concentrically arranged on a flexible member (2) where a mirror surface (3) is formed to produce a strength distribution pattern (2a). Attractive force is generated as electrostatic force between an upper electrode (8) and a lower electrode (9) according to the voltage applied from a drive circuit (10) so as to contract the second space (7) and accordingly expand the first space (5) in order to deform the mirror surface. At this time, the profile of the mirror surface is deformed to show a desired profile that can compensate the spherical aberration by the pattern formed on the flexible member (2) as strength distribution pattern (2a). With this arrangement, only a single drive actuator (10) is needed to deform the mirror surface to simplify the configuration and the control operation. The mirror surface can be deformed stepwise to show predetermined deformed profiles depending on the pattern formed as strength distribution pattern (2a). Then, it is possible to compensate the spherical aberration for each of the three or more than three recording layers of the optical disc. |
