Patent ID: 8295143
Filing Date: 2012-10-23
Classification: G11B

Abstract:
1. An aberration correcting device, comprising: an aberration correcting element which modulates a phase of incident light; and a position adjusting section which moves the aberration correcting element in a direction perpendicular to an optical axis of the incident light, wherein the aberration correcting element includes first and second aberration correction plates, each of which is disposed such that the phase of transmitted light beam differs with transmission position of the incident light beam with the same phase, and the aberration correcting element includes a reference arrangement which is an arrangement of the first and second aberration correction plates in which the light beams transmitted through the aberration correcting element have the same phase, and a point on the first aberration correction plate crossing the optical axis is a point O wherein the position adjusting section includes a mechanism which moves the first and second aberration correction plates in a direction perpendicular to the optical axis and the points O wherein the aberration correcting element is an astigmatism correcting element which generates an astigmatism for the incident light, and the first aberration correction plate is a first astigmatism correction plate and the second aberration correction plate is a second astigmatism correction plate, when the effective diameter of light incident on the first astigmatism correction plate is D where A is a coefficient and U(x) is a step function which is 1 when x>0 and 0 when x<0, and the second astigmatism correction plate has a shape in which the point O the position adjusting section includes a mechanism which moves the first astigmatism correction plate by a distance x