Optical pickup device

Abstract

In order to (i) reduce astigmatism due to a diffraction grating capable of compensating light intensity distribution of a light beam emitted by a light source and (ii) simplify fabrication processes, an optical pickup device of the present invention includes: a semiconductor laser 1 ; a collimator lens 4 ; a diffraction grating 3 capable of changing light intensity distribution of a light beam emitted by the semiconductor laser 1 ; a polarizing beam splitter 5 for causing a laser beam reflected by an optical disc 8 to be directed in a direction different from a direction of the light beam emitted by the semiconductor laser 1; and a parallel plate 2 for compensating astigmatism due to the diffraction grating 3, the parallel plate 2 being provided between the semiconductor laser 1 and the collimator lens 4 so as to be inclined to an optical axis of the semiconductor laser 1.

Description

Technical field [0001] The present invention relates to an optical pickup device used when information is recorded or reproduced on an optical recording medium such as an optical disc, and more particularly to an astigmatism phenomenon that can be improved by a diffraction grating that can change the intensity distribution of a light beam emitted by a semiconductor laser的optical pickup device. Background technique [0002] In recent years, in order to increase the density and capacity of the information recording capacity of optical recording media such as optical discs for recording high-quality moving images, an optical pickup device capable of forming minute spots on the optical recording media with a light beam is required. [0003] For example, Patent Document 1: Japanese Patent Laid-Open No. 2001-134972 (Publication Date: May 18, 2001: p. 7, Fig. 1) discloses a method as described below, that is, in order to make a light beam on an optical recording medium A tiny spot is fo...

AI Technical Summary

Problems solved by technology

[0006] However, in the optical pickup device described in Patent Document 1, the influence of astigmatism due to the shape of the hologram diffraction grating 102 for correcting the light intensity distribution of the light beam emitted from the semiconductor laser light source 101 is not considered.

In other words, on the existing holographic diffraction grating 102, it is known that the astigmatism phenomenon occurs due to the shape of the grating groove. Due to the astigmatism, the emitted light passing through the objective lens cannot form a tiny light spot on the optical disc, so there is a problem Yes, playback signal quality deteriorates, tracking error signal amplitude decreases

[0012] First of all, in the optical pickup device described in Patent Document 2, since the diffraction grating for correcting the light intensity distribution is not considered, there is a problem that the light beam cannot form tiny light spots on the optical disc 208.

That is to say, in order to use the astigmatism correcting element 202 to make it produce predetermined astigmatism, it is necessary to do two-axis adjustment, and there is a problem that the assembly process of the optical pickup device becomes complicated.

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