Abstract: According to one embodiment, a diffraction pattern of a diffraction element, or a hologram polarization element, to guide a reflected laser beam divided into a predetermined number to a photodetector is combined preferably as one unit, in order to provide an optical head unit and an optical disc apparatus, which provides a stable reproducing signal, irrespectively of the standards of recording media, when reproducing information from a recording medium of optional standard. By using this diffraction pattern, it is possible to obtain outputs usable to detect first, second and third signals used to detect a tracking error when reproducing information recorded on an optical disc from a reflected laser beam from an optical disc, a fourth signal used to detect a focus error, and a fifth signal used to detect a disc tilt error and a spherical aberration compensating component.

Abstract: According to one embodiment, a diffraction pattern of a diffraction element or hologram polarization element to guide a reflected laser beam divided into a predetermined number is suitably combined as one body in a photodetector, and an optical head unit is easily designed to obtain a focus error signal, a track error signal, a correction track error signal (in a system with a lens shift), and a reproducing signal (RF) from a laser beam reflected on an optical disc. Therefore, when reproducing information from a recording medium of optional standard, it is possible to provide an optical head unit and optical disc apparatus which provides a stable reproducing signal regardless of the standards of recording media.

Abstract: The refractive index of a light transmission layer of an optical disk is set within the range of 1.45 to 1.75, the numerical aperture of a lens emitting laser light which is incident onto the light transmission layer is set to 0.65, and the wavelength range of the laser light is set within the range of 395 to 415 nm. Further, in order that aberrations fall within the range of certain acceptable values, the thickness t of the light transmission layer is set within the range of f(n)?t1?t?f(n)+t2, employing constants t1, t2 determined based on an acceptable value of aberration and function f(n) of the refractive index n.

Abstract: To provide an optical head unit and an information recording/reproducing apparatus which are configured to provide a stable reproducing signal when reproducing information from a recording medium of a corresponding standard by selectively using laser beams with different wavelengths, a stable reproduce signal is obtained by one object lens when reproducing information from a recording medium of a standard defined according to each of three laser beams with different wavelengths, by arranging first to third light sources capable of outputting lights with different wavelengths, first and second wavelength selection films related to the arrangement of the light sources, and a polarization beam splitter in a predetermined order, and separating an output for power monitor by a polarization beam splitter.

Abstract: To provide an optical head unit which is configured to provide a reproducing signal difficult to be influenced by vibrations when reproducing information from a recording medium of a corresponding standard by selectively using laser beams with different wavelengths, the distance between a beam split phase of a beam splitter and a photodetector is reduced by providing a ball lens on a beam split plane defined not parallel and not vertical to an axial line connecting an optical coupling prism and a beam splitter, and reducing the distance between a photodetector and a beam split plane of a beam splitter, as an embodiment of a disc apparatus.

Abstract: To have laser light sources with different wavelengths as one body, to guide the optical axes of the laser light sources through a common optics as far as possible, and to realize compactness, manufacturing easiness, low cost and high performance and reliability, when the wavelengths of laser beams from first, second and third light sources 21, 22, and 23 are different, a laser beam with a shortest wavelength is output from the first light source, a laser beam with a intermediate wavelength is output from the second light source, and a laser beam with a longest wavelength is output from the third light source. In this arrangement, a laser beam from the light source with a shortest wavelength is reflected by the least number of times.

Abstract: To provide an optical head unit which is configured to provide a reproduce signal when reproducing information from a recording medium of a corresponding standard by selectively using laser beams with different wavelengths, an optical diffraction element is provided, in which the grooves of a binary diffraction grating mainly for a laser beam with a wavelength of 655 nm and a blazed diffraction grating mainly for a laser beam with a wavelength of 405 nm are defined substantially parallel, and the reflected laser beams of the laser beams with respective wavelengths reflected by a corresponding optical disc are guided to a substantially the same detection area or detection areas positioned very close to one another in a photodetector.

Abstract: An embodiment of an optical head unit which is difficult to be influenced by an inter-layer crosstalk of recording layers and decreases a load of a signal reproduce system when reproducing and recording information from an optical disc having two or more recording layers, provide a diffraction optical element for focusing a pattern on the light-receiving surface of a photodetector which receives a reflected laser beam reflected on first and second recording layers of an optical disc and outputs a corresponding signal, in a state that a component close to the center of a reflected laser beam reflected by an optical disc is polarized. The diffraction optical element diffracts the central portion of a reflected laser beam at a fixed rate, receives a reflected laser beam reflected on the recording layer of an optical disc which passes a peripheral edge portion as a non-diffracted light.

Abstract: To provide an optical pickup and an optical disc apparatus which obtains stable reproduce signal when reproducing information from a recording medium of a standard handled by selectively using laser beams with different wavelengths, use a diffraction grating having a diffraction pattern defined according to a laser beam with a first wavelength, and when a laser beam with a second wavelength different from a first wavelength passes, obtain an RF signal by adding a non-diffracted light and diffracted light to an output signal.

Abstract: In a gas humidifier used for humidifying fuel in a molten carbonate fuel cell (MCFC), a small-size gas humidifier is achieved by carrying out a steam-generating process and a gas humidifying process by the use of the steam by using a single unit. In order to achieve this structure, a plurality of longitudinal tube plates are laminated in a thickness direction with predetermined intervals so that a heat-exchanger core (100) of a plate-fin type is prepared. Heating-use high-temperature fluid (A) is allowed to flow alternately through a plurality of spaces that are formed inside the heat-exchanger core (100) and placed side by side in the horizontal direction so as to direct a gas to be humidified (B) to another space from above to below. An injection tube (210), which is used for spraying liquid (C) that serves as a steam source, is inserted virtually horizontally along tube plates on two sides in an upper portion of each space through which the gas to be humidified (B) flows.

Abstract: An optical disc apparatus of the invention in its broader aspects, by locating, at a position displaced a predetermined distance from the focal point of a condenser lens, a light-receiving surface of a photodetector for receiving a laser beam reflected from first and second recording layers of an optical disc, is configured, when playing back a signal from a certain recording layer, to decrease the difference in a crosstalk caused by a light reflected from other recording layers.

Abstract: An optical disc apparatus of the present invention in its broader aspects is configured to have a predetermined range of A/M2, which is determined by an area A of a light-receiving surface of a photodetector to receive a reflected laser beam reflected on first and second recording layers of an optical disc, and a lateral magnification M (ratio of a condenser lens focal length fc to an objective lens focal length fo) of a light-receiving system to pass a reflected laser beam.

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: 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: 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: 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: An optical head and optical disc apparatus according to the present invention can guide each of optional light rays of different wavelength from a plurality of light sources to a recording medium through a single optical system, and can play back the signal from the reflected light from the recording medium through a single light receiving system.

Abstract: The refractive index of a light transmission layer of an optical disk is set within the range of 1.45 to 1.75, the numerical aperture of a lens emitting laser light which is incident onto the light transmission layer is set to 0.65, and the wavelength range of the laser light is set within the range of 395 to 415 nm. Further, in order that aberrations fall within the range of certain acceptable values, the thickness t of the light transmission layer is set within the range of f(n)−t1≦t≦f(n)+t2, employing constants t1, t2 determined based on an acceptable value of aberration and function f(n) of the refractive index n.