Abstract: An optical head for recording or reproducing a signal on or from an optical recording medium comprising a light source, an objective lens for condensing light emitted from the light source to the optical recording medium, and a light-separating means arranged between the light source and the objective lens in order to separate the light reflected from the optical recording medium from the light emitted from the light source is characterized in that the light-separating means consists of a first glass, a multilayer film formed on the first glass, and an adhesive layer arranged on the multilayer film in order to bond a second glass onto the multilayer film, and the majority of the light emitted from the light source enters into the light-separating means through the first glass and is reflected by the multilayer film.

Abstract: An objective lens for converging a light beam emitted from a first light source on a recording surface (17a) of a first optical information recording medium covered with a transparent substrate (7a) and converging a light beam emitted from a second light source on a recording surface (17b) of a second optical information recording medium covered with a transparent substrate (7b) having a thickness greater than the transparent substrate (7a). On an incident plane for the light beam, there are formed a center region (A1), an intermediate region (A2) surrounding the center region (A1), and a peripheral region (A3) surrounding the intermediate region (A2). A diffraction grating (11) is provided on the lens surface of the intermediate region (A2).

Abstract: An optical head is provided with: an objective-lens-use opening that determines an aperture of the objective lens; a light-source light-quantity controlling opening that aperture-controls light that has been separated by the light separation device; a light detector that receives light that has been aperture-controlled by the light-source light-quantity controlling opening; and a light detector that receives light that has been reflected by the optical recording medium, and has an arrangement in which: the length of the optical light path from the spherical aberration correcting device to the objective-lens-use opening is made virtually the same as a length of the optical light path from the spherical aberration correcting device to the light-source light-quantity controlling opening, and the aperture of the light-source light-quantity controlling opening has virtually the same size as the aperture of the objective-lens-use opening.

Abstract: An optical lens includes a hologram, a refractive lens, and a phase level difference. The hologram has a sawtooth shape grating having a sawtooth shape in cross-section, and generates +2nd-order diffracted light most strongly with respect to blue light and +1st-order diffracted light most strongly with respect to red light, by setting a height of the sawtooth shape grating. The +2nd-order diffracted light of blue light is condensed through a substrate with a thickness t1, and the +1st-diffracted light of red light is condensed through a substrate with a thickness t2 (t1<t2). The difference in optical path length occurring when the blue light passes through the phase level difference is five times the wavelength of the blue light.

Abstract: A transmission diffraction grating body including a base material being substantially transparent with respect to wavelength ?1 and having a refractive index n0; another base material being substantially transparent with respect to wavelength ?1 and having a refractive index n1, which is formed on the base material having a refractive index n0; and a relief diffraction grating formed on the base material having a refractive index n1; wherein the refractive indexes n1 and n0 satisfy the relationship: n1>n0. Thus, the base material having a refractive index n1 can be formed of a high refractive index material, and when the depth of grating of the diffraction grating is set so that the diffraction grating diffracts the light with wavelength ?1 and does not diffract the light with wavelength ?2, the depth of grating of the diffraction grating can be made to be shallow, thus preventing the loss of the amount of the light with wavelength ?1.

Abstract: An optical head device includes a focusing optical system for focusing a laser beam emitted from a semiconductor laser light source on an optical information medium with an objective lens. A chromatic aberration correction element for correcting chromatic aberration occurring in the objective lens is provided between the semiconductor laser light source and the optical information medium. A light distribution correction element in which the transmittance increases with the distance from the center of the aperture surface of the objective lens is provided so as to correct a reduction of the intensity of the light incident on the aperture surface of the objective lens with the distance from the center of the aperture surface.

Abstract: An optical head device includes a focusing optical system for focusing a laser beam emitted from a semiconductor laser light source on an optical information medium with an objective lens. A chromatic aberration correction element for correcting chromatic aberration occurring in the objective lens is provided between the semiconductor laser light source and the optical information medium. A light distribution correction element in which the transmittance increases with the distance from the center of the aperture surface of the objective lens is provided so as to correct a reduction of the intensity of the light incident on the aperture surface of the objective lens with the distance from the center of the aperture surface.

Abstract: An optical head device includes a focusing optical system for focusing a laser beam emitted from a semiconductor laser light source on an optical information medium with an objective lens. A chromatic aberration correction element for correcting chromatic aberration occurring in the objective lens is provided between the semiconductor laser light source and the optical information medium. A light distribution correction element in which the transmittance increases with the distance from the center of the aperture surface of the objective lens is provided so as to correct a reduction of the intensity of the light incident on the aperture surface of the objective lens with the distance from the center of the aperture surface.

Abstract: An optical element having a high capture efficiency and rim intensity is provided. The optical element includes a central axis, a first curved surface extending in the transverse direction with respect to the central axis, a second curved surface extending in the transverse direction with respect to the central axis, and a peripheral surface extending between the first curved surface and the second curved surface. Light is refracted from the time light is incident on the first curved surface to the time the light is emitted from the second curved surface. Thereby, a light intensity distribution of the light emitted from the second curved surface and a light intensity distribution of the light incident on the first curved surface are different from each other, and a rim intensity improvement rate R, which is a rate of the rim intensity of the emitted light with respect to the rim intensity of the incident light is 1.07 or more and 1.

Abstract: Conventional lenses for DVD/CD compatible writing/reading are liable to CD jitter deterioration due to phase shifts in a central area. Setting a corresponding base material thickness of an intermediate area of the circumference A2 to greater than 1.2 mm which is the base material thickness of the CD, that is, converging luminous flux that has passed through the intermediate area of the circumference A2 onto a farther place than the information recording surface of the base material thickness of the CD makes it possible to reduce jitter deterioration due to phase shifts. Further, it makes possible to provide a system with higher precision and higher reliability.

Abstract: An optical head is provided which is capable of realizing a stable tracking control, even if the rotational center of an information recording medium is not located on the extension line of the transfer directions of a light-concentrating element. This optical head includes: a semiconductor laser which emits a beam of light; an objective lens which concentrates the beam of light on an optical disk; a transfer mechanism which transfers the objective lens between the outermost circumference and the innermost circumference of the recording area of the optical disk along the optical disk; and a photo-detector which detects a beam of light that returns from the optical disk. The photo-detector includes a plurality of areas which are divided by a division line.

Abstract: A light beam reflected by an information medium is split by a diffraction optical system into first diffraction light and second diffraction light, which is not a complex conjugate wave of the first diffraction light, in a predetermined energy distribution ratio. The first diffraction light enters a first photodetector (195) of a photodetector and is used for reading out data information recorded on the information medium, while the second diffraction light enters second and third photodetectors (194, 195) and is used for obtaining a servo error signal. With this optical head device, the area of the first photodetector can be reduced, thus allowing a high-speed reproduction of a data signal. Further, the first photodetector becomes less susceptible to stray light. Moreover, the number of head amplifiers, which are needed for detecting the data signal, decreases, and the S/N ratio improves.

Abstract: An optical head reproduces optical disks of different disk plate thickness t1 (0.6 mm) or t2 (1.2 mm) by using light beams of two wavelengths and one object lens. An converging element comprises a central portion and outer portion, wherein the central portion has optimum design plate thickness of 0.6*t1 to t1 and the outer portion has optimum design plate thickness of 0.6 mm. By providing a step difference in the converging element, information can be recorded or reproduced for an information medium of disk plate thickness t1 and for an information medium of disk plate thickness t2, in a state having small side lobes. Alternatively, a step difference is provided in the object lens, and optical distance L2 from a second light source to a condensing optical system is set to 80 to 95% of optical distance L1 from a first light source to the condensing optical system. Alternatively, only light of first wavelength is shielded or diffracted in a ring-like shape.

Abstract: Providing an objective lens with a large numerical aperture (NA), the present invention records or plays conventional optical disks such as CDs and DVDs using an optical head capable of recording or reproducing high-density optical disks. An optical element (8) is provided between a first and second laser light source and an objective lens (18) for the purpose of converting a wave front of a second optical beam 32. Furthermore, the optical element (8) and the objective lens (18) are fixed to move as a single piece.

Abstract: An optical head reproduces optical disks of different disk plate thickness thicknesses t1 (0.6 mm) or t2 (1.2 mm) by using light beams of two wavelengths and one object lens. An converging element comprises a central portion and outer portion, wherein the central portion has optimum design plate thickness of 0.6*t1 to t1 and the outer portion has optimum design plate thickness of 0.6 mm. By providing a step difference in the converging element, information can be recorded or reproduced for an information medium of disk plate thickness t1 and for an information medium of disk plate thickness t2, in a state having small side lobes. Alternatively, a step difference is provided in the object lens, and optical distance L2 from a second light source to a condensing optical system is set to 80 to 95% of optical distance L1 from a first light source to the condensing optical system. Alternatively, only light of first wavelength is shielded or diffracted in a ring-like shape.

Abstract: An optical head is provided with: an objective-lens-use opening that determines an aperture of the objective lens; a light-source light-quantity controlling opening that aperture-controls light that has been separated by the light separation device; a light detector that receives light that has been aperture-controlled by the light-source light-quantity controlling opening; and a light detector that receives light that has been reflected by the optical recording medium, and has an arrangement in which: the length of the optical light path from the spherical aberration correcting device to the objective-lens-use opening is made virtually the same as a length of the optical light path from the spherical aberration correcting device to the light-source light-quantity controlling opening, and the aperture of the light-source light-quantity controlling opening has virtually the same size as the aperture of the objective-lens-use opening.

Abstract: An optical head reproduces optical disks of different disk plate thickness t1 (0.6 mm) or t2 (1.2 mm) by using light beams of two wavelengths and one object lens. An converging element comprises a central portion and outer portion, wherein the central portion has optimum design plate thickness of 0.6*t1 to t1 and the outer portion has optimum design plate thickness of 0.6 mm. By providing a step difference in the converging element, information can be recorded or reproduced for an information medium of disk plate thickness t1 and for an information medium of disk plate thickness t2, in a state having small side lobes. Alternatively, a step difference is provided in the object lens, and optical distance L2 from a second light source to a condensing optical system is set to 80 to 95% of optical distance L1 from a first light source to the condensing optical system. Alternatively, only light of first wavelength is shielded or diffracted in a ring-like shape.

Abstract: Conventional lenses for DVD/CD compatible writing/reading are liable to CD jitter deterioration due to phase shifts in a central area. Setting a corresponding base material thickness of an intermediate area to greater than 1.2 mm which is the base material thickness of the CD makes it possible to reduce jitter deterioration due to phase shifts and eliminate level differences between the central area and peripheral area, facilitate manufacturing of processing metal molds, allow extension of a life, which in turn makes it possible to use glass as a lens material, realize cost reduction or provide a system with higher precision and higher reliability.

Abstract: An optical pickup head is provided with a light source, a diffracting means for creating a plurality of diffracted beams, a converging means for focusing the diffracted beams onto an optical storage medium, a beam branching means for branching the plurality of beams reflected by the optical storage medium, and an optical detecting means for outputting a signal corresponding to the amount of light of the received beams. The optical detecting means has main beam light receiving portions and sub-beam light receiving portions. The amount of light of the first or higher order diffracted beams when they are substantially focused on and reflected by a focus plane of the plurality of information recording planes is equal to or greater than the amount of light of the zero order diffracted beam when it is reflected without focusing by a non-focus plane other then the focus plane of the plurality of information recording planes.

Abstract: A compound objective lens is composed of a hologram lens or transmitting a part of incident light without any diffraction to form a beam of transmitted light and diffracting a remaining part of the incident light to form a beam of first-order diffracted light, and an objective lens for converging the transmitted light to form a first converging spot on a front surface of a thin type of first information medium and converging the diffracted light to form a second converging spot on a front surface of a thick type of second information medium. Because the hologram selectively functions as a concave lens for the diffracted light, a curvature of the transmitted light differs from that of the diffracted light.