System and method of astigmatism correction in an optical head apparatus
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorsShinsuke Shikama, Eiichi Toide
Life of this patent
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Abstract
An optical head apparatus comprises a laser light source device emitting linearly polarized light, a converging lens for converging the light pencil emitted from the laser light source onto information recording tracks on a recording medium, and an optical system including a beam splitter for separating the light pencil reflected from the recording medium from the light pencil emitted from the laser light source. The converging lens is one formed by molding. The rotary position of the converging lens about the optical axis of the converging lens is so adjusted that the astigmatism of the optical system from the laser light source to the recording medium is minimum.
Claims17
A method of producing an optical head apparatus of the type having a laser light source device emitting a linearly polarized light beam, and a converging lens for converging the light beam from the laser light source onto information recording tracks on a recording medium, said method comprising the steps of:
- molding a plastic material, to form said converging lens whereby the astigmatism of the converging lens against the linearly polarized light beam varies with the rotation of the converging lens about the optical axis;
- and
- adjusting the rotary position of the converging lens about the optical axis of the converging lens to minimize the astigmatism of the light beam as converged onto said recording medium.
An optical head apparatus comprising:
- a laser light source device emitting linearly polarized light beam, and
- a converging lens of the type formed by injecting a plastic material into a mold die through an injection gate, wherein the direction of a line connecting the injection gate and the center of the lens is substantially parallel with the direction of the polarization of the light beam entering the converging lens, for converging the light beam emitted from the laser light source onto information recording tracks on a recording medium for recording information.
A method of producing an optical head apparatus of the type having a laser light source device emitting a linearly polarized light beam, and a converging lens for converging the light beam from the laser light source onto a recording medium, said method comprising the steps of:
- molding said converging lens by injecting a plastic material into a mold die through an injection gate whereby, the converging lens has an astigmatism against the linearly polarized light beam which varies with the rotation of the converging lens about the optical axis;
- and
- setting the direction of the gate at the time of molding the converging lens so that the astigmatism due to the converging lens cancels the astigmatism of the optical system from the laser light source device at the point just before the plastic lens and the astigmatism due to the image height of the light beam which is converged by the converging lens.
Dependencies are inferred from the claim text.