Abstract: An optical pickup apparatus includes an objective lens having a numeric aperture and an incident face. An antireflection coating is formed on the incident face. A collimating lens converts laser light from a laser diode into parallel light, and causes the parallel light to be made incident on the incident face through the antireflection coating. The thickness of the antireflection coating causes a transmittance of laser light that enters the objective lens to be: set at a first predetermined transmittance value, when the numeric aperture is between zero and a first predetermined numeric aperture value; set to correlate linearly with the numeric aperture when the numeric aperture is between the first predetermined numeric aperture value and a second predetermined numeric aperture value; and set at a second predetermined transmittance value, when the numeric aperture is between the second predetermined numeric aperture value and a third predetermined numeric aperture value.

Abstract: An optical pickup apparatus includes an objective lens having a numeric aperture and an incident face. An antireflection coating is formed on the incident face. A collimating lens converts laser light from a laser diode into parallel light, and causes the parallel light to be made incident on the incident face through the antireflection coating. The thickness of the antireflection coating causes a transmittance of laser light that enters the objective lens to be: set at a first predetermined transmittance value, when the numeric aperture is between zero and a first predetermined numeric aperture value; set to correlate linearly with the numeric aperture when the numeric aperture is between the first predetermined numeric aperture value and a second predetermined numeric aperture value; and set at a second predetermined transmittance value, when the numeric aperture is between the second predetermined numeric aperture value and a third predetermined numeric aperture value.

Abstract: An optical pickup apparatus comprising: an objective lens configured to focus laser light having the Gaussian distribution properties emitted from a laser diode to a signal recording layer of an optical disc; and an adjustment coating formed on a surface of an incident face of the objective lens on which the laser light is to be made incident, the adjustment coating being configured to adjust transmittance of the laser light passing through the objective lens, the adjustment coating being formed on the surface of the incident face such that the transmittance is lowered as a numerical aperture of the objective lens is reduced.

Abstract: An optical pickup unit is disclosed that comprises a first light-emitting element capable of emitting first-wavelength light; a second light-emitting element capable of emitting second-wavelength light whose wavelength is different from that of the first-wavelength light; a polarizing mirror transmitting or reflecting the first-wavelength light and reflecting the second-wavelength light; a first objective lens converging the first-wavelength light on a first medium; and a second objective lens converging the first-wavelength light or the second-wavelength light on a second medium.

Abstract: An optical pickup apparatus comprising: an objective lens configured to focus laser light having the Gaussian distribution properties emitted from a laser diode to a signal recording layer of an optical disc; and an adjustment coating formed on a surface of an incident face of the objective lens on which the laser light is to be made incident, the adjustment coating being configured to adjust transmittance of the laser light passing through the objective lens, the adjustment coating being formed on the surface of the incident face such that the transmittance is lowered as a numerical aperture of the objective lens is reduced.

Abstract: An optical pickup unit is disklosed that comprises a first light-emitting element capable of emitting first-wavelength light; a second light-emitting element capable of emitting second-wavelength light whose wavelength is different from that of the first-wavelength light; a polarizing mirror transmitting or reflecting the first-wavelength light and reflecting the second-wavelength light; a first objective lens converging the first-wavelength light on a first medium; and a second objective lens converging the first-wavelength light or the second-wavelength light on a second medium.

Abstract: A semiconductor laser element and a protective wall surrounding the element are provided on the surface of a metal frame of a semiconductor laser device. Circumferential portions are provided on an outer periphery of the metal frame for rotating the optical axis of light originating from a light-emitting point of the semiconductor laser element to a direction along the surface of the metal frame. By way of a guide of an optical pickup base corresponding to the circumferential portions, the semiconductor laser device is mounted on the optical pickup base.

Abstract: A spherical aberration corrector plate has two wedge-shaped plates having inclined planes opposed to each other. The two wedge-shaped plates have a constant refractive index and are enabled to relatively shift in at least a direction perpendicular to an optical axis. The two wedge-shaped plates are shifted with the inclined planes in contact with each other. Alternatively, the two wedge-shaped plates may be put into a state where the inclined planes are in contact with each other when the two wedge-shaped plate extremely come close to each other. Otherwise, the two wedge-shaped plates may be put into a state where the inclined plates are apart from each other.

Abstract: A semiconductor laser element and a protective wall surrounding the element are provided on the surface of a metal frame of a semiconductor laser device. Circumferential portions are provided on an outer periphery of the metal frame for rotating the optical axis of light originating from a light-emitting point of the semiconductor laser element to a direction along the surface of the metal frame. By way of a guide of an optical pickup base corresponding to the circumferential portions, the semiconductor laser device is mounted on the optical pickup base.

Abstract: In a structure for connecting a lens (17) to a lens holder (25) having a mounting surface (31), the lens has a flange (26) placed on the mounting surface. The flange has a particular surface faced to the mounting surface and at least three protrusions (27) on the particular surface. The mounting surface has a plurality of recesses (32) formed at positions corresponding to the protrusions. Each of the recesses has a depth smaller than a height of a corresponding one of the protrusions and a volume greater than that of the corresponding one. The protrusions are placed in the recesses, respectively, and ultrasonic welded to the lens holder.

Abstract: A rising mirror (MIR′) reflects a laser beam produced by a semiconductor laser (LD′) by a reflecting surface thereof to make the laser beam converge on a signal recording surface of an optical disc (Disc) through an objective lens (OL′) and reflects a return beam from the signal recording surface to make a photodetector (PD) detect the return beam. A rising angle (&thgr;′) between the reflecting surface of the rising mirror (MIR′) and the pickup's lower surface is smaller than 45 degrees. With this structure, optical parts including the semiconductor laser and the photodetector may be arranged in an optical base (OB) with the optical parts inclined to the optical base so that the optical parts are not jutted out the pickup's lower surface downwards.

Abstract: A laser beam emitting device has a laser beam source for emitting a laser beam having a prescribed effective optical path region; and a light-receiving element positioned outside the effective optical path region of the laser beam emitted by the laser beam source and having a plurality of light-receiving regions for detecting intensity of the emitted laser beam. In this device, the output of the laser beam source is adjusted in response to the intensity of the emitted laser beam detected by at least one of the plurality of the light-receiving regions of the light-receiving element. The light-receiving element includes a first light-receiving region located at a position near the optical axis and a second light-receiving region located at a position farther from the optical axis than the position of the first light-receiving region.