Abstract: A light beam emitted from a light source is diffracted into a first light beam and a pair of second light beams, which in turn are furnished with spherical aberration components based on an externally applied control input signal. The first light beam and the pair of second light beams furnished with spherical aberration components are focused by an objective lens on the recording layer of an optical disk. Each of the first light beam and the pair of second light beams reflected from the recording layer of the optical disk and transmitted through the objective lens is received by a corresponding photodetector.

Abstract: There is disclosed an optical disk constituted by covering an information recording layer formed on a substrate with a cover layer having a light transmission property, in which ranges of a thickness t and a refractive index n of the cover layer are defined. That is, a function f(n) which is not a constant regarding the refractive index n of the cover layer, and constants t1, t2 determined based on an allowable value of an aberration in the cover layer are used to set the ranges of the thickness t of the cover layer to a range of f(n)−t1≦t≦f(n)+t2.

Abstract: A light beam is applied to an optical disk through a first hologram and an objective lens. The first hologram has a first region that can diffract light and a second region that can diffract light. The light beam reflected from the optical disk is applied through the objective lens to a second hologram. The second hologram splits the light beam into a first light beam and a second light beam that have passed through the first region and the second region, respectively.

Abstract: There are comprised a laser light source for outputting a light beam, an optical disk having a recording/reproducing surface and a transparent substrate on the surface, an objective lens for gathering the light beam on the optical disk, a relay lens system comprising one or more lenses inserted between the laser light source and the objective lens, means for moving one or more lenses in the relay lens system toward its optical axis so as to correct sphere aberration in accordance with a thickness of the transparent substrate of the optical disk, and means for sustaining a diameter of an incident light on the objective lens when one or more lenses among the relay lenses move.

Abstract: The present invention relates to an optical head device and an optical disk unit using the same. The optical head device includes a relay lens control unit to control at least one of lenses of a relay lens unit based on an output signal outputted from a first optical detector and a power control circuit to control an intensity of a light beam emits from a light source.

Abstract: The present invention relates to an optical head unit and an optical disk unit using the optical head unit. The head unit includes a wavefront transforming optical element control unit to controls a wavefront transforming optical element so as not to transform wavefront of a light beam focused on a recording layer by a focusing unit due to the thickness error of a light transmission layer positioned between the recording layer and the focusing unit based on an electrical signal outputted from a first light detector, and an output control unit that controls light amount of a light beam radiated by a light emitting unit based on the magnitude of the electrical signal outputted from the light detector.

Abstract: An optical disk apparatus comprises an optical pick-up unit for reproducing information on an optical disk, a first reproducer for processing an information signal obtained by the pick-up unit by one of a waveform slice method and a PRML method, and producing a first reproduction signal, a second reproducer for detecting a minimum value of a level of the information signal and producing a second reproduction signal, and a switch for selecting, as a reproduction information signal, one of the first and second reproduction signals, in accordance with a recording density of the optical disk to be reproduced.

Abstract: An optical head apparatus includes an objective lens which receives a light beam from a light source and condenses the light beam onto the optical recording medium. A photo-detector has plurality of photo-detecting planes disposed orthogonal to an optical axis of the reflected light beam and symmetrical with respect to the optical axis, and detects the light beam reflected by the optical recording medium. Each of the photo-detecting plane is divided into a plurality of divided areas by a plurality of dividing lines which are symmetrically divide the photo-detecting planes with respect to the optical axis.

Abstract: A regenerator for use in an ammonia absorption refrigerator comprises a heater for heating an ammonia aqueous solution and a rectifying column for enriching ammonia in an ammonia solution-vapor mixture obtained in and introduced from the heater, wherein the heater comprises a heater body having a heating chamber, a burner of lean pre-mixture combustion type disposed in a lower portion of the heating chamber, and a heat transfer tube bundle provided in a meandering arrangement above the burner within the heating chamber, the heat transfer tube bundle having an inlet and an outlet which are respectively connected to lower portions of the rectifying column via transfer pipes.

Abstract: An optical disk apparatus comprises an optical pick-up unit for reproducing information on an optical disk, a first reproducer for processing an information signal obtained by the pick-up unit by one of a waveform slice method and a PRML method, and producing a first reproduction signal, a second reproducer for detecting a minimum value of a level of the information signal and producing a second reproduction signal, and a switch for selecting, as a reproduction information signal, one of the first and second reproduction signals, in accordance with a recording density of the optical disk to be reproduced.

Abstract: An optical disk apparatus comprises an optical pick-up unit for reproducing information on an optical disk, a first reproducer for processing an information signal obtained by the pick-up unit by one of a waveform slice method and a PRML method, and producing a first reproduction signal, a second reproducer for detecting a minimum value of a level of the information signal and producing a second reproduction signal, and a switch for selecting, as a reproduction information signal, one of the first and second reproduction signals, in accordance with a recording density of the optical disk to be reproduced.