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 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: 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: 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: 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: The present invention provides a method of replacing secondary batteries. In the method, batteries can be replaced at a low cost and performance of an overall battery assembly can be maximized after the battery replacement. The battery assembly is composed by electrically connecting a plurality of secondary batteries in series or in parallel. When a portion of the secondary batteries is judged as defective, the defective batteries are replaced by replacement batteries. In an aspect of the method, voltage is detected for every predetermined voltage detection block unit concerning secondary batteries composing the battery assembly in order to judge defects of the secondary batteries in the voltage detection block unit. Batteries in a voltage detection block unit will be replaced with replacement batteries if they are judged as defective.

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 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 has a phase change layer for changing the phase of light passing therethrough; a plurality of aberration correcting electrodes, arranged on one side of said phase change layer, for correcting optical aberrations, each of said aberration correcting electrodes being split into a plurality of regions; an insulating film interposed between said aberration correcting electrodes; and a specific electrode arranged on the other side of said phase change layer, and wherein: said aberration correcting electrodes, at least other than the outermost aberration correcting electrode as viewed from said phase change layer, have openings formed in prescribed positions, and each of said aberration correcting electrodes, other than the innermost aberration correcting electrode, faces said phase change layer through said openings formed in other aberration correcting electrodes.

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: The invention presents an optical element that has a good correcting effect with regard to aberrations and is easy to manufacture, as well as an optical head and an optical recording and reproducing apparatus using the same. The optical element includes a first substrate, a second substrate arranged substantially in parallel to the first substrate, a voltage applying electrode arranged between the first substrate and a liquid crystal, an opposing electrode arranged substantially in parallel to the voltage applying electrode and opposing the voltage applying electrode, and a liquid crystal arranged between the first substrate and the second substrate. By changing the voltage between the voltage applying electrode and the opposing electrode, the phase of the light incident on the liquid crystal can be changed.

Abstract: A transmission diffraction grating body including a base material being substantially transparent with respect to wavelength &lgr;1 and having a refractive index n0; another base material being substantially transparent with respect to wavelength &lgr;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 &lgr;1 and does not diffract the light with wavelength &lgr;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 &lgr;1.

Abstract: The present invention provides a method of replacing secondary batteries. In the method, batteries can be replaced at a low cost and performance of an overall battery assembly can be maximized after the battery replacement. The battery assembly is composed by electrically connecting a plurality of secondary batteries in series or in parallel. When a portion of the secondary batteries is judged as defective, the defective batteries are replaced by replacement batteries. In an aspect of the method, voltage is detected for every predetermined voltage detection block unit concerning secondary batteries composing the battery assembly in order to judge defects of the secondary batteries in the voltage detection block unit. Batteries in a voltage detection block unit will be replaced with replacement batteries if they are judged as defective.

Abstract: An optical head device includes a light source for emitting a light beam having a predetermined wavelength, an optical system for converging the light beam emitted from the light source on an information medium, and a light detector for receiving the light beam reflected from the information medium and detecting a focus error signal based on the received light beam. The light detector includes a plurality of pairs of photodetectors. The light detector generates the focus error signal based on a differential signal generated by each pair of the plurality of pairs of photodetectors. The plurality of pairs of photodetectors are arranged so that a fluctuation in the differential signal generated by at least one of the pairs of the plurality of pairs of photodetectors is cancelled by a fluctuation in the differential signal generated by at least another of the pairs of the plurality of pairs of photodetectors.

Abstract: The objective lens of the present invention includes a center portion and a periphery portion surrounding the center portion. An aberration of the periphery portion is corrected such that a light spot is formed by the convergence of a luminous flux which has been transmitted through the periphery portion and then transmitted through a first light transmissive flat plate, and an aberration of the center portion is corrected such that a light spot is formed by the convergence of a luminous flux which has been transmitted through the center portion and then transmitted through a second light transmissive flat plate which is thicker than the first light transmissive flat plate.

Abstract: An optical head has a first light source; a second light source; a transmitting and reflecting element having a first surface and a second surface, and used to reflect diverging light from the first light source at the first surface, and to allow diverging light from the second light source to enter the second surface and to go out from the first surface, thereby to synthesize optical paths; an objective lens for converging light from the transmitting and reflecting element on an information recording surface of an optical disk and for condensing light reflected from the disk; and a photo-detector for receiving the reflected light, wherein the first surface and the second surface of the transmitting and reflecting element are not parallel to each other in order to decrease aberration when the diverging light from the second light source passes through the transmitting and reflecting element.

Abstract: The objective lens of the present invention includes a center portion and a periphery portion surrounding the center portion. An aberration of the periphery portion is corrected such that a light spot is formed by the convergence of a luminous flux which has been transmitted through the periphery portion and then transmitted through a first light transmissive flat plate, and an aberration of the center portion is corrected such that a light spot is formed by the convergence of a luminous flux which has been transmitted through the center portion and then transmitted through a second light transmissive flat plate which is thicker than the first light transmissive flat plate.

Abstract: A grinding method includes a grit sticking step and a grinding step. In the grit sticking step, grit particles are stuck in a first tool by contacting the first tool with a second tool which is harder than the first tool, rotating the first tool and the second tool, and feeding the grit to the contacting surface between the first tool and the second tool. In the grinding step, the workpiece is ground by contacting the first tool with the workpiece and rotating the first tool or the workpiece.

Abstract: Coma of an objective lens occurs depending on the lens-forming condition when plural disks of different substrate thickness are recorded and reproduced. An objective lens according to this invention is not influenced by the coma even if the thickness of the substrates is changed. For this purpose, a diffraction grating whose aberration is corrected is formed on the first side of an aspheric objective lens. Due to this correction, light beams having different diffraction orders, e.g. 0th order diffracted light and +1st order diffracted light, are focused respectively on two kinds of substrates of different thickness. The whole objective lens is tilted to correct its axial coma, and the tilt angle is predetermined to be substantially identical with respect to plural substrates which are different in thickness.

Abstract: An optical head has a light source; luminous flux splitting means for splitting radiation luminous flux of linearly polarized light radiated from the light source into plural luminous fluxes without changing the luminous flux diameter substantially; a wavelength plate for polarizing at least one of the luminous fluxes split by the luminous flux splitting means into a nearly circularly polarized light as illumination luminous flux; an objective lens for converging the illumination luminous flux through the wavelength plate on an optical information medium and collecting the reflected light; and a photodetector for receiving the reflected luminous flux collected by the objective lens after passing through the wavelength plate and the luminous flux splitting means. The quantity of received light for maintaining the S/N ratio is sufficient for reproducing a high density optical disk and a conventional optical disk with a large birefringence.