Method and apparatus for optical pickup capable of performing an effective polarization split

A semiconductor laser unit, comprising:

• a semiconductor laser source configured to emit laser light, said semiconductor laser source being mounted on a board;
• polarization split device comprising:
• an optically isotropic substrate;
• an optically anisotropic film formed on said optically isotropic substrate;
• and
• a diffraction grating comprising:
• a first cyclically structural portion formed on a first surface of said optically anisotropic film such that a depression is cyclically arranged with a predetermined pitch along a direction of the first surface of said optically anisotropic film;
• and
• a second cyclically structural portion comprising an optically transparent material having a refractive index approximately equivalent to a refractive index of said optically anisotropic film in a direction of ordinary light rays and extraordinary light rays and configured to cover said first cyclically structural portion such that an edge surface of said second cyclically structural portion forms a plane approximately equal to a plane formed by the front surface of said optically anisotropic film,
• wherein diffraction light having a diffraction angle greater than a predetermined angle among diffraction light diffracted by said diffraction grating is inhibited from being discharged outside of said optical isotropic substrate,
• said polarization split device receiving said laser light emitted by said semiconductor laser source;
• and
• a photoreceptor mounted on said board at a position irradiated by said laser light diffracted by said polarization split device.

A semiconductor laser unit, comprising:

• a semiconductor laser source configured to emit laser light, said semiconductor laser source being mounted on a board;
• a polarization split device comprising:
• an optically isotropic substrate;
• an optically anisotropic film formed on said optically isotropic substrate;
• and
• a diffraction grating comprising:
• a first cyclically structural portion formed on a first surface of said optically anisotropic film such that a depression is cyclically arranged with a predetermined pitch along a direction of the first surface of said optically anisotropic film;
• and
• a second cyclically structural portion comprising an optically transparent material having a refractive index approximately equivalent to a refractive index of said optically anisotropic film in a direction of ordinary light rays and extraordinary light rays and configured to cover said first cyclically structural portion such that an edge surface of said second cyclically structural portion forms a plane approximately equal to a plane formed by the front surface of said optically anisotropic film,
• wherein diffraction light having a diffraction angle greater than a predetermined angle among diffraction light diffracted by said diffraction grating is inhibited from being discharged outside of said optical isotropic substrate,
• said polarization split device receiving said laser light emitted by said semiconductor laser source;
• a photoreceptor mounted on said board at a position irradiated by said laser light diffracted by said polarization split device;
• and
• a monitoring photoreceptor mounted on said board at a position irradiated by a monitored light ray generated by a monitored light ray generation mechanism of said polarization split device.

An optical pickup apparatus, comprising:

• a semiconductor laser unit comprising:
• a semiconductor laser source configured to emit laser light, said semiconductor laser source being mounted on a board;
• a polarization split device comprising:
• an optically isotropic substrate;
• an optically anisotropic film formed on said optically isotropic substrate;
• and
• a diffraction grating comprising:
• a first cyclically structural portion formed on a first surface of said optically anisotropic film such that a depression is cyclically arranged with a predetermined pitch along a direction of the first surface of said optically anisotropic film;
• and
• a second cyclically structural portion comprising an optically transparent material having a refractive index approximately equivalent to a refractive index of said optically anisotropic film in a direction of ordinary light rays and extraordinary light rays and configured to cover said first cyclically structural portion such that an edge surface of said second cyclically structural portion forms a plane approximately equal to a plane formed by the front surface of said optically anisotropic film,
• wherein diffraction light having a diffraction angle greater than a predetermined angle among diffraction light diffracted by said diffraction grating is inhibited from being discharged outside of said optical isotropic substrate,
• said polarization split device receiving said laser light emitted by said semiconductor laser source;
• a photoreceptor mounted on said board at a position irradiated by said laser light diffracted by said polarization split device;
• and
• a monitoring photoreceptor mounted on said board at a position irradiated by a monitored light ray generated by a monitored light ray generation mechanism of said polarization split device,
• an object lens configured to irradiate an optical recording medium with said laser light emitted from said semiconductor laser unit;
• and
• a quarter-λ plate configured to convert a polarization plane of said laser light in a light path between said polarization split device of said semiconductor laser unit and said optical recording medium.

A polarized split device, comprising:

• an optically isotropic substrate;
• an optically anisotropic film formed on said optically isotropic substrate;
• and
• means for diffracting incident light formed in said optically anisotropic film, said means for diffracting incident light comprising:
• means for passing ordinary light rays received in a first incident light direction without diffracting the ordinary light rays;
• means for diffracting extraordinary light rays received in a second incident light direction, opposite to the first incident light direction;
• and
• means for internally reflecting a predetermined order of the extraordinary light rays in said optically isotropic substrate to inhibit the predetermined order of the extraordinary light rays from being discharged outside of said optical isotropic substrate.

A semiconductor laser unit, comprising:

• laser means for emitting laser light, mounted on a board;
• a polarization split device comprising:
• means for diffracting incident light formed in said optically anisotropic film, said means for diffracting incident light comprising:
• means for passing ordinary light rays received in a first incident light direction without diffracting the ordinary light rays;
• means for diffracting extraordinary light rays received in a second incident light direction, opposite to the first incident light direction;
• and
• means for internally reflecting a predetermined order of the extraordinary light rays in said optically isotropic substrate to inhibit the predetermined order of the extraordinary light rays from being discharged outside of said optical isotropic substrate;
• light reception means mounted on said board at a position irradiated by said laser light diffracted by said polarization split device.

A semiconductor laser unit, comprising:

• laser means for emitting laser light, mounted on a board;
• a polarization split device comprising:
• an optically isotropic substrate;
• an optically anisotropic film formed on said optically isotropic substrate;
• and
• means for diffracting incident light formed in said optically anisotropic film, said means for diffracting incident light comprising:
• means for passing ordinary light rays received in a first incident light direction without diffracting the ordinary light rays;
• means for diffracting extraordinary light rays received in a second incident light direction, opposite to the first incident light direction;
• and
• means for internally reflecting a predetermined order of the extraordinary light rays in said optically isotropic substrate to inhibit the extraordinary light rays from being discharged outside of said optical isotropic substrate;
• light reception means mounted on said board at a position irradiated by said laser light diffracted by said polarization split device;
• and
• monitoring means mounted on said board for receiving a monitored light ray generated by a monitored light ray means.

An optical pickup apparatus, comprising:

• a semiconductor laser unit comprising:
• laser means for emitting laser light, mounted on a board;
• a polarization split device comprising:
• an optically isotropic substrate;
• an optically anisotropic film formed on said optically isotropic substrate;
• and
• means for diffracting incident light formed in said optically anisotropic film, said means for diffracting incident light comprising:
• means for passing ordinary light rays in a first incident light direction without diffracting the ordinary light rays;
• means for diffracting extraordinary light rays received in a second incident light direction, opposite to the first incident light direction;
• and
• means for internally reflecting the extraordinary light rays in said optically isotropic substrate to inhibit the extraordinary light rays from being discharged outside of said optical isotropic substrate;
• said polarization split device receiving said laser light emitted by said semiconductor laser source;
• light reception means mounted on said board at a position irradiated by said laser light diffracted by said polarization split device;
• and
• monitoring means mounted on said board for receiving a monitored light ray at a position irradiated by a monitored light ray generated by a monitoring light ray generated means of said polarization split device,
• focusing means for irradiating an optical recording medium with said laser light emitted from said semiconductor laser means;
• and
• means for converting a polarization plane of said laser light in a light path between said polarization split device of said semiconductor laser unit and said optical recording medium.