Abstract: A zone phase correcting lens wherein a change in the third-order spherical aberration or the like is small in the case of a change in temperature and an optical head device having the zone phase correcting lens used as an objective lens. A minus sign is appended to the height measurement of a step formed so as to make the lens thickness in the optical axis thinner toward the outer region and a plus sign is appended to a step formed so as to make the lens thickness thicker toward the outer region. Supposing that D is an absolute value of the sum of the height measurements of the steps having the minus sign on the first surface and the second surface and E is an absolute value of the sum of the height measurements of the steps having the plus sign on the first surface and the second surface, a wavelength ?1 and a refractive index N1 of the lens for a first laser beam satisfy the following conditions: 10×?1<{D×(N1?1)}<30×?1 2×E<D.

Abstract: A common objective lens typically used in reading data from different optical data storage media that are responsive to laser beams of different wavelengths, such as CD and DVD is provided. The lens has a refracting surface with inner and outer refracting surface regions. Diffraction gratings are provided in both the inner and outer refracting surface regions with each having a differential optical path function. The inner diffraction grating and at least a part of the outer diffraction grating emit an order of diffracted beams which have different polarities to cancel out any spherical aberrations caused by a change in temperature.

Abstract: A ring zonal phase correction lens made of resin is provided with a refraction face structurally formed on at least one of a first lens face and a second lens face. The refraction face includes three or more ring zonal shaped refraction curved surfaces which are formed to be adjacent to each other through step portions formed in an optical axis direction for correcting a phase of a laser beam emitted from a laser by respective ring zonal shaped refraction curved surfaces. The step portion is formed such that a lens thickness of an outer ring zonal shaped refraction curved surface becomes thicker than that of an inner ring zonal shaped refraction curved surface and the step portion is formed at a half or more outer area of an effective radius of the refraction face.

Abstract: A lighting optical unit having an optical system for irradiating light from a light-source lamp on a predetermined object in a uniform and/or convergent manner includes a reflector for reflecting light from the light-source lamp to provide converged light and an optical assembly for collimating this converged light to provide a bundle of approximately parallel rays, wherein the bundle of approximately parallel rays is made to enter the optical systeml. Thus, in a liquid-crystal projector using a transmission type liquid-crystal panel with micro-lens, while a demand for increasing a quantity of light incident on an effective area of pixel of a liquid-crystal panel is being satisfied, the lighting optical unit can be made compact in size.

Abstract: An optical element includes a diffraction grating by which both a first laser beam and a second laser beam are diffracted. A diffraction performance of the diffraction grating is expressed by an optical path difference function, a third spherical aberration SA31 of the first laser beam and a third spherical aberration SA32 of the second laser beam in a wave front aberration calculated by the optical path difference function satisfy the following conditional expressions: 0.005<|SA31?SA32|<0.015[?rms] SA31×SA32<0.

Abstract: A ring zonal phase correction lens made of resin is provided with a refraction face structurally formed on at least one of a first lens face and a second lens face. The refraction face includes three or more ring zonal shaped refraction curved surfaces which are formed to be adjacent to each other through step portions formed in an optical axis direction for correcting a phase of a laser beam emitted from a laser by respective ring zonal shaped refraction curved surfaces. The step portion is formed such that a lens thickness of an outer ring zonal shaped refraction curved surface becomes thicker than that of an inner ring zonal shaped refraction curved surface and the step portion is formed at a half or more outer area of an effective radius of the refraction face.

Abstract: An optical head device that converges first and second laser beams having different wavelengths on recording surfaces of first and second optical recording media through a single light converging optical system including an objective lens for recording or reproducing data on the recording surfaces. A refracting surface of the objective lens is divided into two regions, i.e., a central refracting surface region with an optical axis thereof being as a center and an outer circumferential refracting surface region that surrounds an outer circumference of the central refracting surface region. A diffraction grating is formed generally entirely over the central refracting surface region. When recording or reproducing data on the first optical recording medium using the first laser beam, a beam spot is formed with a diffracted beam obtained by the central refracting surface region.

Abstract: Provided are a polarization converting device capable of downsizing parts and improving light-use efficiency, and an illumination optical system capable of obtaining illuminating light with high efficiency and superior illumination characteristics by using the polarization converting device, and a projector. A polarization splitting film is inclined at approximately 45° upward and downward with respect to an optical axis, thereby the polarization splitting film is formed in the shape of the letter V of which the apex is pointed to a direction where incident light enters. A reflective surface has such a shape that the polarization splitting film is horizontally flipped, thereby it is formed in the shape of the letter V of which the apex is pointed to a direction where a polarized component is emitted.

Abstract: An objective lens by which an effective value of spherical aberration with respect to an optical recording medium is reduced and in which a beam spot having a small diameter can be formed on a recording surface of the optical recording medium. An objective lens for an optical head device comprises a refraction surface provided with a middle region and a peripheral region, where, assuming that a distance from an optical axis to an outer peripheral portion of the middle region in a direction crossing the optical axis at right angles is R, there exist in a range of R/3 to 2R/3 from the optical axis, zero regions where the spherical aberration with respect to an optical recording medium turns to zero and/or an increase/decrease region where the spherical aberration with respect to the optical recording medium increases or decreases toward zero.

Abstract: A zone phase correcting lens wherein a change in the third-order spherical aberration or the like is small in the case of a change in temperature and an optical head device having the zone phase correcting lens used as an objective lens. A minus sign is appended to the height measurement of a step formed so as to make the lens thickness in the optical axis thinner toward the outer region and a plus sign is appended to a step formed so as to make the lens thickness thicker toward the outer region. Supposing that D is an absolute value of the sum of the height measurements of the steps having the minus sign on the first surface and the second surface and E is an absolute value of the sum of the height measurements of the steps having the plus sign on the first surface and the second surface, a wavelength ?1 and a refractive index N1 of the lens for a first laser beam satisfy the following conditions: 10×?1<{D×(N1?1)}<30×?1 2×E<D.

Abstract: An optical element includes a diffraction grating by which both a first laser beam and a second laser beam are diffracted. A diffraction performance of the diffraction grating is expressed by an optical path difference function, a third spherical aberration SA31 of the first laser beam and a third spherical aberration SA32 of the second laser beam in a wave front aberration calculated by the optical path difference function satisfy the following conditional expressions: 0.005<|SA31?SA32|<0.015 [?rms] SA31×SA32<0.

Abstract: A common objective lens typically used in reading data from different optical data storage media that are responsive to laser beams of different wavelengths, such as CD and DVD is provided. The lens has a refracting surface with inner and outer refracting surface regions. Diffraction gratings are provided in both the inner and outer refracting surface regions with each having a differential optical path function. The inner diffraction grating and at least a part of the outer diffraction grating emit an order of diffracted beams which have different polarities to cancel out any spherical aberrations caused by a change in temperature.

Abstract: Provided are a polarization converting device capable of downsizing parts and improving light-use efficiency, and an illumination optical system capable of obtaining illuminating light with high efficiency and superior illumination characteristics by using the polarization converting device, and a projector. A polarization splitting film is inclined at approximately 45° upward and downward with respect to an optical axis, thereby the polarization splitting film is formed in the shape of the letter V of which the apex is pointed to a direction where incident light enters. A reflective surface has such a shape that the polarization splitting film is horizontally flipped, thereby it is formed in the shape of the letter V of which the apex is pointed to a direction where a polarized component is emitted.

Abstract: An optical head device includes a first laser light source that emits a first laser beam with a first wavelength, a second laser light source that emits a second laser beam with a second wavelength which is different from that of the first laser beam, a common objective lens that converges the first laser beam on a recording surface of a first optical recording medium and the second laser beam on a recording surface of a second optical recording medium, a refraction surface that is formed on the common objective lens so as to be divided into a center side refraction surface region around an optical axis of the common objective lens and an outer peripheral side refraction surface region surrounding the center side refraction surface region and a center side diffraction grating that is formed all over the center side refraction surface region and is provided with a number of minute steps in a concentrically circular shape.

Abstract: A lighting optical unit having an optical system 13 to 16 for irradiating light from a light-source lamp 11 on a predetermined object 22 in a uniform and/or convergent manner includes a reflector 1 for reflecting light from the light-source lamp 11 to provide converged light and an optical assembly 2 for collimating this converged light to provide a bundle of approximately parallel rays, wherein the bundle of approximately parallel rays is made to enter the optical system 13 to 16. Thus, in a liquid-crystal projector using a transmission type liquid-crystal panel with micro-lens, while a demand for increasing a quantity of light incident on an effective area of pixel of a liquid-crystal panel is being satisfied, the lighting optical unit can be made compact in size.

Abstract: An optical head device that converges first and second laser beams having different wavelengths on recording surfaces of first and second optical recording media through a single light converging optical system including an objective lens for recording or reproducing data on the recording surfaces. A refracting surface of the objective lens is divided into two regions, i.e., a central refracting surface region with an optical axis thereof being as a center and an outer circumferential refracting surface region that surrounds an outer circumference of the central refracting surface region. A diffraction grating is formed generally entirely over the central refracting surface region. When recording or reproducing data on the first optical recording medium using the first laser beam, a beam spot is formed with a diffracted beam obtained by the central refracting surface region.

Abstract: Single convex lens element has a positive power in both the main and sub-scanning directions on the surface which is the closer to the surface to be scanned and which is anamorphic such that any section taken through a plane that is parallel to the central optical axis and which is normal to the main scanning direction provides a generally constant surface geometry along the length of that surface. This lens ensures not only the production of a good image plane and satisfactory f.theta. characteristics in the main scanning direction but also the effective correction of the curvature of the field in the sub-scanning direction.