Abstract: An optical pickup device is so configured as to change the propagating directions of light fluxes in four light flux areas defined in the periphery of an optical axis of laser light, out of the laser light reflected on a disc, to separate the four light fluxes one from the other. A signal light area where only signal light exists is defined on a detecting surface of a photodetector. Sensors for signal light is disposed at a position in the signal light area to be irradiated by the signal light, and a tracking error signal is generated based on a signal from the sensors. A direct-current component of the tracking error signal resulting from positional displacements of the sensors is cancelled by adjusting a gain of the signal from the sensor.

Abstract: A purification unit for purifying air by a photocatalytic reaction includes a first light source which emits light; a first reflection plate which reflects the light emitted from the first light source; and a plurality of purification plates which cause the photocatalytic reaction by irradiation of the light emitted from the first light source. In this arrangement, at least one of the purification plates is disposed between the first reflection plate and the first light source, and the light emitted from the first light source is transmitted through the purification plate disposed between the first reflection plate and the first light source, and then is reflected on the first reflection plate for irradiation onto the purification plates.

Abstract: An optical pickup device includes an astigmatism element which sets focal line positions to be defined by convergence of laser light away from each other, a diffraction element which diffracts four light fluxes obtained by a light flux of the laser light to disperse the four light fluxes from each other, and a photodetector having a first sensing section and a second sensing section which respectively receive m-th order diffraction light and n-th order diffraction light of the four light fluxes. In this arrangement, the first sensing section receives eight light fluxes obtained by dividing the four light fluxes of the m-th order diffraction light by two straight lines to output detection signals of the number less than eight.

Abstract: An optical pickup device radiates laser light to a disc having a plurality of recording layers in a direction of lamination. The optical pickup device includes an astigmatic element and a spectral element. The astigmatic element allows reflected light from the disc to converge in a first direction and form a first focal line at a first position, and allows reflected light to converge in a second direction and form a second focal line at a second position closer to the disc than the first position. The spectral element splits a reflected light flux in two along a straight line parallel to the first direction and turns traveling directions of the split two light fluxes into directions separated from each other. Here, the spectral element is interposed between the second focal line of the reflected light from a target recording layer and the second focal line of the reflected light from a deeper recording layer than the target recording layer.

Abstract: An optical pickup apparatus is provided with an angle adjusting element. The angle adjusting element changes a propagation direction of luminous fluxes of four luminous flux regions set about an optical axis of the laser light, out of laser light reflected by a disc, and mutually disperses the luminous fluxes. A signal light region in which signal light only is present appears on a detecting surface of a photodetector. A sensor pattern for signal light is placed at a position irradiated with the signal light within this region. A sensor pattern for a coma aberration detection is placed on an inner side of this region.

Abstract: An optical pickup apparatus is provided with an angle adjusting element. The angle adjusting element changes a propagation direction of luminous fluxes of four luminous flux regions set about an optical axis of the laser light, out of laser light reflected by a disc, and mutually disperses the luminous fluxes. A signal light region in which signal light only is present appears on a detecting surface of a photodetector. A sensor pattern for signal light is placed at a position irradiated with the signal light within this region. A sensor pattern for a spherical aberration detection is placed on an inner side of this region.

Abstract: An optical pickup apparatus includes an astigmatic element, an angle adjusting element for contradicting propagation directions of luminous fluxes within four different luminous flux regions out of a reflected light, a polarization adjusting element. Two of the luminous flux regions are placed in a direction in which aligned are a set of opposite angles made by the two mutually crossing straight lines respectively parallel to a first convergence direction and a second convergence direction vertical to the first convergence direction by the astigmatic element, and the remaining two luminous flux regions are placed in a direction in which an alternate set of opposite angles are aligned. The polarization adjusting element differentiates polarization directions of luminous fluxes which are selected out of the luminous fluxes within the four luminous flux regions and which are adjacent in a peripheral direction in which the optical axis of reflected light serves as an axis.

Abstract: An optical pickup device includes an astigmatism element which sets focal line positions to be defined by convergence of laser light away from each other, a diffraction element which diffracts four light fluxes obtained by a light flux of the laser light to disperse the four light fluxes from each other, and a photodetector having a first sensing section and a second sensing section which respectively receive m-th order diffraction light and n-th order diffraction light of the four light fluxes. In this arrangement, the first sensing section receives eight light fluxes obtained by dividing the four light fluxes of the m-th order diffraction light by two straight lines to output detection signals of the number less than eight.

Abstract: An optical element is disposed on an optical path between a beam branching element and a photodetector. The optical element is disposed at a focal position of a stray light beam reflected by a recording layer except a target recording layer, and shields or attenuates the light beam in a region where the stray light beam converges.

Abstract: A diffraction element is disposed between a beam branching element (such as a beam splitter) and a photodetector. The diffraction element further segment an interference fringe introduced into stray light by a diffraction grating which divides a laser beam emitted from a laser beam source into a main beam and two sub-beams.

Abstract: An optical pickup device radiates laser light to a disc having a plurality of recording layers in a direction of lamination. The optical pickup device includes an astigmatic element and a spectral element. The astigmatic element allows reflected light from the disc to converge in a first direction and form a first focal line at a first position, and allows reflected light to converge in a second direction and form a second focal line at a second position closer to the disc than the first position. The spectral element splits a reflected light flux in two along a straight line parallel to the first direction and turns traveling directions of the split two light fluxes into directions separated from each other. Here, the spectral element is interposed between the second focal line of the reflected light from a target recording layer and the second focal line of the reflected light from a deeper recording layer than the target recording layer.

Abstract: An optical pickup device is so configured as to change the propagating directions of light fluxes in four light flux areas defined in the periphery of an optical axis of laser light, out of the laser light reflected on a disc, to separate the four light fluxes one from the other. A signal light area where only signal light exists is defined on a detecting surface of a photodetector. Sensors for signal light is disposed at a position in the signal light area to be irradiated by the signal light, and a tracking error signal is generated based on a signal from the sensors. A direct-current component of the tracking error signal resulting from positional displacements of the sensors is cancelled by adjusting a gain of the signal from the sensor.

Abstract: An optical pickup apparatus is provided with an angle adjusting element. The angle adjusting element changes a propagation direction of luminous fluxes of four luminous flux regions set about an optical axis of the laser light, out of laser light reflected by a disc, and mutually disperses the luminous fluxes. A signal light region in which signal light only is present appears on a detecting surface of a photodetector. A sensor pattern for signal light is placed at a position irradiated with the signal light within this region. A sensor pattern for a spherical aberration detection is placed on an inner side of this region.

Abstract: An optical pickup apparatus is provided with an angle adjusting element. The angle adjusting element changes a propagation direction of luminous fluxes of four luminous flux regions set about an optical axis of the laser light, out of laser light reflected by a disc, and mutually disperses the luminous fluxes. A signal light region in which signal light only is present appears on a detecting surface of a photodetector. A sensor pattern for signal light is placed at a position irradiated with the signal light within this region. A sensor pattern for a coma aberration detection is placed on an inner side of this region.

Abstract: An optical pickup apparatus includes an astigmatic element, an angle adjusting element for contradicting propagation directions of luminous fluxes within four different luminous flux regions out of a reflected light, a polarization adjusting element. Two of the luminous flux regions are placed in a direction in which aligned are a set of opposite angles made by the two mutually crossing straight lines respectively parallel to a first convergence direction and a second convergence direction vertical to the first convergence direction by the astigmatic element, and the remaining two luminous flux regions are placed in a direction in which an alternate set of opposite angles are aligned. The polarization adjusting element differentiates polarization directions of luminous fluxes which are selected out of the luminous fluxes within the four luminous flux regions and which are adjacent in a peripheral direction in which the optical axis of reflected light serves as an axis.

Abstract: A diffraction element is disposed between a beam branching element (such as a beam splitter) and a photodetector. The diffraction element further segment an interference fringe introduced into stray light by a diffraction grating which divides a laser beam emitted from a laser beam source into a main beam and two sub-beams.

Abstract: An optical element is disposed on an optical path between a beam branching element and a photodetector. The optical element is disposed at a focal position of a stray light beam reflected by a recording layer except a target recording layer, and shields or attenuates the light beam in a region where the stray light beam converges.

Abstract: A polarizing diffraction element is disposed between a photodetector and a liquid crystal lens to impart diffraction action to light reflected from a disk. The polarizing diffraction element is configured such that a focal distance of diffracted light having a predetermined order of the reflected light when the liquid crystal lens is in a first driving state is equalized to a focal distance of 0-order diffracted light of the reflected light when the liquid crystal lens is in a second driving state.

Abstract: A laser beam emitted from a light source is divided into a main beam and two sub-beams by a diffraction grating. A filter is arranged between a collimator lens and an objective lens. A filter unit is arranged in a predetermined pattern in the filter. The filter unit gives a maximum transmittance or a maximum reflectance at an incident angle at which the laser beam is incident in a parallel light state. The filter unit is formed in a pattern in which at least the laser beam reflected from a layer except a recording layer of an irradiation target is prevented from entering a sub-beam sensor pattern.

Abstract: An illuminating device (1) is formed of a light source (12) in which LED chips (11) are arranged in an array shape and lens cells (14) are arranged on a light-emission side of each of the LED chips (11), and a pair of fly's eye lenses (13) that integrates and guides to a liquid crystal panel (3) the light emitted from each of the LED chips (11) and collimated by the lens cells (14). The LED chip (11) and the lens cell (14) are formed in a square shape, and an aspect ratio thereof corresponds to that of the liquid crystal display panel (3). In addition, the lens cells (14) are arranged separately from one another in such a manner to have wall surfaces (air gaps), and the wall surfaces serve as reflective surfaces.