Astigmatism generating device to remove comma aberration and spherical aberration
AssigneePioneer Corporation
InventorsSatoshi Sugiura, Akihiro Tachibana, Yoshihisa Kubota
Life of this patent
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Abstract
An optical pickup device includes a photodetector divided into four light-receiving elements by two dividing lines, an incident optical system for irradiating a light beam onto an optical recording medium, and a receiving optical system for guiding a return light from the optical recording medium to the photodetector, wherein the receiving optical system includes astigmatism generating means for generating astigmatism having an astigmatism axis at an angle of 45 degree with respect to the two dividing lines.
Claims17
An optical pickup device comprising:
- a photodetector divided into four light-receiving elements by two substantially perpendicular dividing lines;
- an incident optical system for irradiating a light beam onto an optical recording medium, the incident optical system including a light source for irradiating an incident light beam and an object lens for concentrating the incident light beam onto the optical recording medium and a hologram optical element, the light source, the object lens and the hologram optical element arranged on a first optical straight axis;
- and
- a receiving optical system for guiding a return light from the optical recording medium to the photodetector, the receiving optical system including the hologram optical element for deflecting the return light toward the photodetector and for generating astigmatism having an astigmatism axis fixed at an angle of 45 degrees with respect to the two dividing lines, the hologram optical element and the photodetector arranged on a second optical straight axis defining a different direction than the first optical straight axis.
An optical pickup device, comprising:
- a light source for irradiating an incident light beam;
- an object lens for concentrating the incident light beam onto an optical recording medium;
- a photodetector having four light-receiving elements for receiving a return light beam from the optical recording medium, the four light-receiving elements defining two substantially perpendicular dividing lines;
- and
- a hologram optical element positioned in a forward light path between the light source and the object lens and in a light path between the object lens and the photodetector, the hologram optical element passing the incident light beam and deflecting the return light beam toward the photodetector and generating astigmatism having an astigmatism axis fixed at an angle of 45 degrees with respect to the two dividing lines onto the return light beam,
- wherein the optical pickup device defines two optical axes at different directions with respect to each other, one axis defined through the light source, the hologram, and the object lens but the photodetector, and the other axis defined through the hologram and the photodetector.
The optical pickup device according to claim, 11, wherein the polarization hologram optical element has a first transparent flat portion formed of a uniaxial crystal.
An optical pickup device, comprising:
- a light source for irradiating an incident light beam;
- an object lens for concentrating the incident light beam onto an optical recording medium;
- a photodetector having four light-receiving elements for receiving a return light beam from the optical recording medium, the four light-receiving elements defining two substantially perpendicular dividing lines;
- and
- a hologram optical element positioned in a forward light path between the light source and the object lens and in a light path between the object lens and the photodetector, the hologram optical element passing the incident light beam and deflecting the return light beam toward the photodetector and generating astigmatism having an astigmatism axis fixed at an angle of 45 degrees with respect to the two dividing lines onto the return light beam, the hologram optical element reducing spherical aberrations and coma aberrations, the hologram optical element being formed as one optical piece,
- wherein the optical pickup device defines two optical axes at different directions with respect to each other, one axis defined through the light source, the hologram and the object lens but the photodetector, and the other axis defined through the hologram and the photodetector.
Dependencies are inferred from the claim text.