Optical pickup, and method and appts. for correcting aberration of optical beam

Abstract

A spherical aberration correcting unit corrects an aberration caused in an optical beam radiated toward an information recording medium and focused on the medium. The correcting unit comprises an aberration corrector, driver, light receiver, and controller. The aberration corrector, which is composed of a plurality of optical members, forms the optical beam into a parallel pencil and corrects the aberration caused in the optical beam. The driver drives any one of the optical members in an optical axis direction of the optical beam. The light receiver receives light reflected from the medium to produce a light-reception signal from the received light, and the controller controls the driver based on the produced light-reception signal.

Description

technical field The present invention relates to a method and a device for correcting aberrations caused in a light beam focused on an object to be detected, and to an optical pickup for use with the correction device. Background technique Generally, an optical pickup is employed by an information recording medium. In this optical pickup field, as the spot diameter of the light beam emitted from the optical pickup and focused onto the information recording medium decreases, the density of recording or reproducing pieces of information becomes larger. The diameter of the spot becomes smaller as the wavelength of light becomes shorter and the numerical aperture (NA) of the objective lens becomes larger. Therefore, in order to increase the storage capacity of the optical recording medium, it is necessary to install a semiconductor laser (LD) emitting a beam of shorter wavelength as a light source in the optical pickup, and to use an objective lens with a larger numerical ape...

AI Technical Summary

Problems solved by technology

In addition, in the pickup structure shown in Fig. 2, the entire collimator lens must be moved, so that the amount of lens driving required to correct spherical aberration becomes large

Consequently, the space required for this drive of the collimating lens is forced to be relatively large

In addition, the collimating lens needs to be moved over a longer distance, resulting in a longer correction time and increased energy consumption

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