Abstract: An optical head device is provided with an objective lens (5) for collecting light emitted from a light source on an optical recording medium (6); a diffraction optical element (8a) for diffracting the reflection light of the emitted light reflected by the recording medium (6) and enters through the objective lens (5); and a photodetector (10a) for receiving a light flux of the reflection light diffracted by the diffraction optical element (8a). The light flux has a first light flux group passed through an area in the diffraction optical element (8a), and a second light flux group passed through a part of the area. The photodetector (10a) detects the first light flux group and the second light flux group by separate photodetector sections (14a to 14h).

Abstract: An optical head unit is configured as an optical head unit corresponding to an optical recording medium of BD standard, and an optical recording medium of HD DVD standard. A magnification-variable lens includes convex lens, concave lens, and convex lens. The magnification-variable lens allows each lens to be movable along the optical axis direction, and has the function of changing the ratio of diameter of light incident from the convex lens to the diameter of light that exits from the convex lens within a specific ratio. The magnification-variable lens emits light having a diameter corresponding to the numerical aperture, 0.85, of the objective lens towards the objective lens upon recording/reproducing on a disk of BD standard, and emits light having a diameter corresponding to the numerical aperture, 0.65, of the objective lens upon recording/reproducing on a disk of HD DVD standard.

Abstract: There is disclosed an optical head apparatus and an optical information recording or reproducing apparatus capable of obtaining a high light output at a recording time, and a high S/N at a reproducing time with respect to any of disks of next-generation, DVD, and CD standards. Light having a wavelength of 400 nm emitted from a semiconductor laser is almost all reflected by a beam splitter, and condensed on a disk of the next-generation standard. Light having a wavelength of 660 nm emitted from a semiconductor laser is almost all reflected by a beam splitter, almost all transmitted through the beam splitter, and condensed on the disk of the DVD standard. Light having a wavelength of 780 nm emitted from a semiconductor laser is almost all reflected by a beam splitter, almost all transmitted through the beam splitters and condensed on the disk of the CD standard. Reflected light from the disk is almost all transmitted through the beam splitters and received by a photodetector.

Abstract: An optical information recording/reproducing device includes a liquid optical element containing a liquid crystal polymer layer in an optical head. A liquid crystal optical element drive unit drives a liquid crystal optical element having a first pattern electrode divided into a plurality of region at one side of the liquid crystal polymer layer in the optical axis direction. The first pattern electrode includes a first region arranged to surround the optical axis and second to ninth regions arranged outside the first regions in such a manner that the circumference is divided eight portions. The liquid crystal optical element drive unit applies a first effective voltage to the first region, a second effective voltage to the second and the sixth region, a third effective voltage to the third and the seventh region, a fourth effective voltage to the fourth and the eighth region, and a fifth effective voltage to the fifth and the ninth region.

Abstract: In an optical head device, a birefringence correcting element 5a containing a material showing mono-axial refractive index anisotropy is located before an objective lens. The birefringence correcting element 5a is circumferentially divided into four regions by two straight lines passing through an optical axis and intersecting each other at right angle. Each of the four regions is radially divided into four sub-regions by three circles centered at the optical axis. The direction of optic axes of the sub-regions 11a to 14a and 11c to 14c is a direction of x-axis, while the direction of optic axes of the sub-regions 11b to 14b and 11d to 14d is a direction of y-axis. A phase difference of sub-regions between a polarized light component polarized in a direction parallel to the optic axis and another polarized light component polarized in a direction vertical to the optic axis increases in order of the sub-regions 11a to 11d, sub-regions 12a to 12d, sub-regions 13a to 13d and the sub-regions 14a to 14d.

Abstract: The light emitted from a semiconductor laser is divided by a diffractive optical element into three light beams which are 0th-order light as the main beam and ±1st-order diffracted lights as the sub-beams, and the track error signals by the main beam and the sub-beams are detected, respectively, by a differential phase detection method. By the effect of the diffractive optical element, the light intensity distributions of the main beam and the sub-beams become different when making incidence on an objective lens. Therefore, when there is radial tilt in a disk, the phases of the track error signals by the main beam and the sub-beams are shifted with each other. Based on the shift in the phases of the track error signals, radial tilt of the disk is detected.

Abstract: A diffractive optical element for dividing a light emitted from a light source into a main beam and at least one sub-beam, an objective lens for focusing the beams on a disk-shaped optical recording medium with spiral tracks, and a photodetector for receiving the beams reflected from the optical recording medium are provided. At least a part of the diffractive optical element includes a diffraction grating divided into four or more plural areas by three or more plural lines in parallel with a direction corresponding to a tangential direction of the optical recording medium, and in two adjacent areas among the plural areas, phases of the lattices are shifted by n to each other.

Abstract: To provide an optical head capable of detecting tilt with high sensitivity for two kinds of optical recording media having different groove pitches, and to provide an optical information recording/reproducing device, diffraction optical elements split emitted light from a light source into a main beam, a first sub-beam (diffracted light from a region of the diffraction optical element, and a second sub-beam (diffracted light from a region of the diffraction optical element). The region of the diffraction optical element has a diameter larger than that of the region of the diffraction optical element. A push-pull signal by the first sub-beam under track-servo is employed as a radial tilt error signal for an optical recording medium having a narrow groove pitch, and a push-pull signal by the second sub-beam under track-servo is employed as a radial tilt error signal for an optical recording medium having a wide groove pitch.

Abstract: Four types of optical systems, a polarization optical system including an objective lens having a high numerical aperture, a polarization optical system including an objective lens having a low numerical aperture, a non-polarization optical system including an objective lens having a high numerical aperture and a non-polarization optical system including an objective lens having a low numerical aperture, are selectively used at the time of irradiating light from a semiconductor laser on a target disk for measurement, and the in-plane birefringence characteristic and perpendicular birefringence characteristic of the target disk are separately acquired based on the amounts of received light obtained by measuring reflected light from the target disk by a photosensor.

Abstract: An optical head device is provided with an objective lens (5) for collecting light emitted from a light source on an optical recording medium (6); a diffraction optical element (8a) for diffracting the reflection light of the emitted light reflected by the recording medium (6) and enters through the objective lens (5); and a photodetector (10a) for receiving a light flux of the reflection light diffracted by the diffraction optical element (8a). The light flux has a first light flux group passed through an area in the diffraction optical element (8a), and a second light flux group passed through a part of the area. The photodetector (10a) detects the first light flux group and the second light flux group by separate photodetector sections (14a to 14h).

Abstract: In an optical system, reflected light from the disk is diffracted by a hologram optical element, and received by an optical detector. A focusing error signal is detected from ?1st-order diffracted light of the hologram optical element. A tracking error signal by the differential phase method, a tracking error signal by a push-pull method and the data signal recorded on the disk are detected from +1st-order diffracted light of the hologram optical element. A diffraction efficiency of the +1st-order diffracted light is higher than a diffraction efficiency of the ?1st-order diffracted light.

Abstract: An optical head apparatus of an optical information recording/reproducing apparatus is provided with a light source. An objective lens focuses an output light emitted by said light source on a disc optical recording medium for which a groove or a pit for tracking is provided. T photo-detector receives a reflected light reflected by said optical recording medium. A polarizing splitter unit splits said output light and said reflected light. A quarter-wave plate disposed between said polarizing splitter section and said objective lens. A birefringence compensating unit reduces a change in an amplitude of a track error signal caused by birefringence in a protective layer of said optical recording medium.

Abstract: [Problems] To provide an optical head device capable of obtaining a desirable track error signal and a lens position signal for both two types of optical media having different groove pitches. [Means for Solving the Problems] Light emitted from a light source is divided by a diffraction optical element (3a) into a main beam that is transmitted light, first sub beams that are positive and negative first order diffracted light beams, and second sub beams that are positive and negative second order diffracted light beams. The phase of the positive and negative first order diffracted light beams from regions (13a, 13c) and that of the positive and negative first order diffracted light beams from regions (13b, 13d) are shifted from each other by 180 degrees, and the phase of positive and negative second order diffracted light beams from regions (13a, 13d) and that of the positive and negative second order diffracted light beams from regions (13b, 13c) are shifted from each other by 180 degrees.

Abstract: An optical head device and an optical recording and reproducing apparatus using this optical head device, which can record information and reproduce the recorded information at any of optical recording media, such as a next generation optical recording medium, in which the wavelength of the light source is made to be shorter, the numerical aperture of the objective lens is made to be higher, and the thickness of the recording medium is made to be thinner, and conventional recording media of DVD and CD standards, are provided. A light having wavelength of 405 nm, emitted from one of optics, is inputted to an objective lens as a collimated light, and is focused on a disk having thickness of 0.1 mm. A light having wavelength of 650 nm, emitted from the other of optics, is inputted to the objective lens as a diverged light, and is focused on a disk having thickness of 0.6 mm.

Abstract: An optical head device and an optical recording and reproducing apparatus using this optical head device, which can record information and reproduce the recorded information at any of optical recording media, such as a next generation optical recording medium, in which the wavelength of the light source is made to be shorter, the numerical aperture of the objective lens is made to be higher, and the thickness of the recording medium is made to be thinner, and conventional recording media of DVD and CD standards, are provided. A light having wavelength of 405 nm, emitted from one of optics, is inputted to an objective lens as a collimated light, and is focused on a disk having thickness of 0.1 mm. A light having wavelength of 650 nm, emitted from the other of optics, is inputted to the objective lens as a diverged light, and is focused on a disk having thickness of 0.6 mm.

Abstract: Light emitted from a light source and having a wavelength of 400 nm is reflected by a beam splitter (BS), and converged on a disk according to a next-generation standard. Reflection light therefrom passes through the BS and is received by a photodetector. Light emitted from a light source and having a wavelength of 660 nm is reflected by the BS and passes through the BS, and converged on a disk according to a DVD standard. Reflection light therefrom passes through the BS and is received by the photodetector. About 50% of light emitted from a light source and having a wavelength of 780 nm is reflected by the BS. The light passes through the BS and is then converged on a disk according to a CD standard. Reflection light therefrom passes through the BS. About 50% of the light passes through the BS and is received by the photodetector. Thus, recording and reproduction can be performed on any of disks according to a next-generation standard, DVD standard, and CD standard.

Abstract: An object of the present invention is to provide an optical head apparatus having a high signal to noise ratio in an RF signal in a simple circuit configuration, and an optical information recording or reproducing apparatus that uses it. The optical head apparatus includes a light source, an objective lens configured to focus an output light beam from the light source onto a disc-shaped optical recording medium, and a light detecting unit configured to receive a reflection light beam from the optical recording medium, and further includes an optical diffraction element configured to separate said reflection light beam into a first light beam group and a second light beam group, wherein the optical diffraction element generates the first light beam group from an entire section region of the reflection light beam and said second light beam group from at least a part of the section region of the reflection light beam.

Abstract: An optical head device and an optical recording and reproducing apparatus using this optical head device, which can record information and reproduce the recorded information at any of optical recording media, such as a next generation optical recording medium, in which the wavelength of the light source is made to be shorter, the numerical aperture of the objective lens is made to be higher, and the thickness of the recording medium is made to be thinner, and conventional recording media of DVD and CD standards, are provided. A light having wavelength of 405 nm, emitted from one of optics, is inputted to an objective lens as a collimated light, and is focused on a disk having thickness of 0.1 mm. A light having wavelength of 650 nm, emitted from the other of optics, is inputted to the objective lens as a diverged light, and is focused on a disk having thickness of 0.6 nm.

Abstract: In an optical head device and an optical information recording/reproducing device using the optical head device, by driving a liquid crystal panel 4a, the liquid crystal panel 4a produces wave aberration for light on a going path and light on a returning path likewise. Accordingly, when the substrate-thickness deviation or tilt of the disc 7 is corrected, the wave aberration due to the substrate-thickness deviation or tilt of the disc 7 and the wave aberration produced by the liquid crystal panel 4a are canceled by each other for both of the light on the going path and the light on the returning path, so that no wave aberration remains for the light on the returning path and the phase distribution is not varied.

Abstract: The invention detects the thickness error of the transparent substrate using a general focus error signal detection system employing the fact that the reflecting light from the optical disk causes distortions in diffraction image at the detection plane or unsymmetrical expansions before and after the detection plane due to spherical aberration as a result of thickness errors of the transparent substrate. The absolute amount of the thickness error of the transparent substrate and its symbol are detected by detecting the difference between the absolute value of the positive side peak and the absolute value of the negative side peak of the focus sum signal, or the difference in focus positions between the peak point of the focus sum signals and the zero point of the focus error signals using the focus error signal detection system according to the knife-edge method. This enables it to detect the thickness error of the transparent substrate without using a special optical system.