Abstract: A first light source 1a emits a first light flux with a first wavelength. A second light source 1b emits a second light flux with a second wavelength that is different from the first wavelength and a third light flux with a third wavelength that is different from the first wavelength and the second wavelength. A collimator lens 6, a first objective lens 9, and a second objective lens 10 collect the first to third light fluxes as converged light on an optical disc. A first composite photodetector 13 detects the reflected light fluxes from the optical disc. The first composite photodetector 13 includes a first quartered light-receiving unit 13a that receives a light flux obtained by reflection of at least one light flux from among the first to third light fluxes from the optical disc and a second quartered light-receiving unit 13b that receives a light flux obtained by reflection of the remaining light fluxes from the optical disc.

Abstract: The present invention provides an optical information medium capable of suppressing the influence of reflection light from an unnecessary information recording face and effectively eliminating spherical aberration at the time of recording/reproducing information to/from a recording medium having a plurality of information recording faces. When reflectance of an information recording face is ?h and transmittance between information recording faces is th, ?h and th of the optical information medium are set so as to satisfy ((?(h?1)2×?(h?2))/(th2×?h))<0.01.

Abstract: An offset-free tracking signal enables stable tracking control even if an optical disc is a multi-layer disc having three or more layers. Light receiving portions of a main region light receiving portion group are arranged between a projection line of a third dividing line on a photodetector and a projection line of a fourth dividing line on the photodetector by stray lights from information layers adjacent to the one, on which a light beam is focused, out of a plurality of information layers. Further, light receiving portions of a subregion light receiving portion group is arranged between a projection line of a first dividing line on a photodetector and a projection line of a second dividing line on the photodetector by the stray lights from the information layers adjacent to the one, on which a light beam is focused, out of the plurality of information layers.

Abstract: Fifth order spherical aberration in addition to third order spherical aberration for an optical information recording medium of which thickness of a light transmission layer changes greatly is corrected. An objective lens collects a laser beam emitted from a semiconductor laser on an optical information recording medium. A spherical aberration correcting portion corrects spherical aberration generated according to a thickness of the light transmission layer of the optical information recording medium, in which the spherical aberration correcting portion includes a collimator lens, a lens holder and a stepping motor for correcting the third order spherical aberration and a liquid crystal element and an applied voltage control portion for correcting the fifth order spherical aberration.

Abstract: An object of the invention is to provide an optical recording medium and an optical information device that enable to improve the quality of a servo signal and a reproduction signal.

Abstract: An object of the invention is to provide an optical recording medium and a method for producing an optical recording medium that enable to improve the quality of a servo signal and a reproduction signal. The optical recording medium satisfies: t3?t4?1 ?m, t4?t2?1 ?m, t2?10 ?m, and t1?(t2+t3+t4)?1 ?m, where t1 is a thickness between a surface of the optical recording medium, and the first information recording surface, t2 is a thickness between the first optical recording surface and the second information recording surface, t3 is a thickness between the second optical recording surface and the third information recording surface, and t4 is a thickness between the third optical recording surface and the fourth information recording surface.

Abstract: A thermosensitive recording printer is provided with semiconductor lasers 1a to 1c, a polygon mirror 7 for condensing laser light emitted from the semiconductor laser 1a to 1c as condensed spots on a recording medium 10 to perform scanning in a main scanning direction, and a control unit 9 for controlling the output of the laser light. If a ratio of a spot diameter D1 of the condensed spots in the main scanning direction and a spot diameter D2 in a sub scanning direction satisfy a relationship of D1/D2?½ at the time of forming an image composed of a plurality of pixels on the recording medium 10 using laser light, high-speed thermosensitive recording and a recording method with an uncomplicated power control are realized without reducing the power density of the condensed spots.

Abstract: An optical recording medium is capable of preventing a back focus at the face thereof and reducing the interference between beams reflected by each recording surface, thereby improving the quality of a servo signal and a reproductive signal. In a disk having (N-1) layers if N is a natural number (more than three), if a cover-layer thickness and intermediate-layer thicknesses are d1, d2, . . . dN, then a difference of 1 ?m or above is set between the sum of di to dj and the sum of dk to dm for arbitrary natural numbers i, j, k, m (i?j?k?m?N). If the refractive indexes are different from a standard value or different for each layer, the thickness of each layer is converted on the basis of the spread width of light according to the thickness.

Abstract: The recording/reproducing quality of a multilayer optical information recording medium deteriorate not only due to interference from other layers caused by light converging on other information layers but also due to stray light converging on the surface of a protective layer and stray light that does not converge on other information layers but rather returns to an optical head through the same optical path as the reproducing signal. The thickness composition of intermediate layers (106, 107, and 108) and the protective layer (109) in a four-layer optical information recording medium are set so as to eliminate the influence of interference caused by stray light from other layers reflected up to three times.

Abstract: An optical head that is restrained from becoming larger, even if it is used for an optical-information recording medium that includes a plurality of information recording layers. In this optical head, a collimating lens is formed by a concave lens disposed on the side of a light source and a convex lens disposed on the side of an objective lens. A collimating-lens actuator moves the convex lens in a direction where a spherical aberration is cancelled which is generated according to the thickness of a light transmission layer up to an information recording layer of the optical-information recording medium. An aperture stop is provided on the side of the collimating lens with respect to the objective lens, and the aperture stop is located near the focal position of the convex lens on the side of the objective lens.

Abstract: An optical head that is restrained from becoming larger, even if it is used for an optical-information recording medium that includes a plurality of information recording layers. In this optical head, a collimating lens is formed by a concave lens disposed on the side of a light source and a convex lens disposed on the side of an objective lens. A collimating-lens actuator moves the convex lens in a direction where a spherical aberration is cancelled which is generated according to the thickness of a light transmission layer up to an information recording layer of the optical-information recording medium. An aperture stop is provided on the side of the collimating lens with respect to the objective lens, and the aperture stop is located near the focal position of the convex lens on the side of the objective lens.

Abstract: An optical recording medium is provided with a plurality of recording layers, wherein the recording layers are formed such that all the spacings between two recording layers in all the combinations selected from the plurality of recording layers do not coincide with each other. Accordingly, the return of lights reflected by other layers to an optical head along the same optical path as reflected light from a readout layer during the reproduction can be avoided. Therefore, an optical recording medium, from which a good reproduction signal can be obtained, can be provided by suppressing the deterioration of a servo signal and a reproduction signal of a reproducing device due to a variation of interference fringes on a light receiving element.

Abstract: An object of the invention is to provide an optical element for use in an optical information recording and reproducing device or a like device for recording or reproducing information with respect to an information recording medium using laser light, wherein the optical element is a resin optical element capable of suppressing lowering in transmittance due to deterioration by irradiation of light having a high energy density, and maintaining a high transmittance for a long time. To realize the above object, used is an optical element made of a silicon resin cured material obtained by subjecting a silicon resin composition containing a silsesquioxane compound to a curing treatment.

Abstract: An optical controller includes a light source for emitting light, an object lens for condensing light emitted from the light source, a light detection unit for receiving light reflected on an optical information recording medium and outputting a signal corresponding to the amount of the light, and a laser control unit for controlling the amount of the light emitted from the light source to the information recording surface on which information is to be recorded or reproduced, based on the recording state of an information recording surface disposed closer to the object lens than an information recording surface on which the information is to be recorded or reproduced.

Abstract: To provide an optical head to produce good servo and read signals by reducing the influence of interference by light reflected from a non-read layer of a multilayer optical disc. The head includes: a first optical system for converging light from a light source on a first or second storage layer; a second optical system for receiving and transmitting light reflected from the first layer and stray light reflected from the second layer when the light is converged on the first layer; a photodetector; and a calculator. The photosensitive areas of the photodetector output signals representing intensities of the light incident there through the second system. The reflected and stray light incident on the second system interfere with each other, and the first and second groups of areas are arranged so as to be equally affected by a variation in intensity caused by the interference.

Abstract: An optical head includes a hologram which extracts, from a luminous flux of reflected light from an optical disk, at least a first luminous flux branch which does not include the optical axis of the luminous flux; and a photodetector which receives the reflected light from the optical disk and produces signal output, wherein the photodetector has light-receiving areas which receive the first luminous flux branch of reflected light from an optical information recording medium layer targeted for recording or playback out of the plurality of optical information recording medium layers of the optical disk, the light-receiving areas are placed in such a way that the signal output resulting from a light spot formed by the first luminous flux branch of the reflected light from the optical information recording medium layer targeted for recording or playback is practically the same between the first and second photodetection areas, and a boundary line of the light-receiving areas is located in such a position as not

Abstract: An optical disk apparatus according to the present invention includes: a light emission section for emitting laser light; an optical system for irradiating the optical disk medium with the laser light; and an aberration control section for controlling aberration of the laser light. In one embodiment, the aberration control section repeatedly switches between a plurality of aberration setting states in a focus lock-in operation. In another embodiment, the aberration control section simultaneously sets a plurality of aberration setting states in a focus lock-in operation. As a result, a plurality of aberration setting states can be allowed to substantially coexist within a single optical system.

Abstract: An optical head device is provided with a light source 1 for emitting a plurality of lights having different wavelengths, an objective lens 31 for focusing a light spot on an optical disc 21, an objective lens 32 for focusing light spots on optical discs 22 to 24, and a prism 53 for splitting a laser light having a wavelength of 405 nm from the light source 1 into a transmitting light and a reflected light, introducing the reflected light to the objective lens 31 and the transmitting light to the objective lens 32, and introducing laser lights having wavelengths of 660 nm, 780 nm from the light source 1 to the objective lens 32.

Abstract: The present invention provides an optical information medium capable of suppressing the influence of reflection light from an unnecessary information recording face and effectively eliminating spherical aberration at the time of recording/reproducing information to/from a recording medium having a plurality of information recording faces. When reflectance of an information recording face is ?h and transmittance between information recording faces is th, ah and th of the optical information medium are set so as to satisfy ((?(h?1)2×?(h?2))/(th2×?h))<0.01.

Abstract: In a optical head, a beam is emitted from a light emitting element in which a plurality of light sources are integrally formed, the light sources being able to emit beams having different wave lengths from one another. An optical system converges the beam coming from any one of the light sources onto an optical information storage medium. An optical separator separates a reflected beam coming from the optical information storage medium from the beam coming from the light source. A light receiving element detects light quantities of the reflected beam separated by the optical separator.