Abstract: An optical head device according to the present invention includes a splitting section for splitting a light beam having been reflected from an optical storage medium. The splitting section includes: a first main region transmitting a first interfering portion; a second main region transmitting a second interfering portion; and first and second sub-regions through which the first interfering portion is transmitted with a lower rate than in the first main region and through which the second interfering portion is transmitted with a lower rate than in the second main region. The splitting section splits the reflected light beam into: a first main light beam transmitted through the first main region; a second main light beam transmitted through the second main region; a first sub-light beam transmitted through the first sub-region; and a second sub-light beam transmitted through the second sub-region.

Abstract: An objective lens includes a diffraction structure for distributing much of a quantity of an incident light beam into two diffracted lights having different diffraction orders from each other, wherein recording or reproduction of information on an optical disk is performed by converging the diffracted light having a longer focal length of the two diffracted lights onto an information recording surface through a protective layer of the optical disk, and a distance from the objective lens to a surface of the protective layer along an optical axis is longer than a distance between focuses of the two diffracted lights along the optical axis when the diffracted light having the longer focal length is converged onto the information recording surface of the optical disk.

Abstract: An optical pickup device, an optical disk drive and method of controlling light performed by the optical pickup device are provided. The optical pickup device includes: a light transmitting system including an object lens for facing a medium having a multi recording layer for storing information, a light source system for providing a plurality of beams used to record information on or reproduce information from the multi recording layer via the light transmitting system, a light-receiving system disposed on a path of a beam reflected from the medium, and a light controller including a light control device for controlling stray light generated in the medium such that the stray light does not reach the light-receiving device.

Abstract: An optical pickup includes a first laser beam light source 1 for emitting a light flux of a first wavelength, a diffraction grating 5 and an optical device 6 having a second laser beam light source 7 for emitting a light flux of a second wavelength and a hologram element 8. In operation, the diffraction grating 5 diffracts the backward light of the first wavelength at a predetermined angle. The hologram element 8 diffracts the backward light of the second wavelength by a first area 8a and also diffracts the backward light of the first wavelength at a reversed-polarity angle to the first area 8a by a second area 8b.

Abstract: An optical pickup device includes a semiconductor laser for emitting laser light, an objective lens for irradiating luminous flux emitted from the semiconductor laser to an optical disc, a branching element having a plurality of regions for branching luminous flux reflected from the optical disc to a plurality of fluxes, and a photodetector having a plurality of light receiving parts which receive luminous flux branched by said branching element. Luminous flux which enters at least two regions arrayed along a direction which is made substantially coincident with a tangential direction of the optical disc in regard to substantially a center of the branching element is arranged along a direction which is made substantially coincident with a radial direction of the optical disc on the photodetector.

Abstract: A hologram optical device, and a compatible optical pickup having the hologram optical device and an information storage medium system employing the hologram optical device. The hologram optical device includes a hologram having a pattern having a period in a 4-step stairway shape. At least one of first, second, third, and fourth steps of the 4-step stairway shape is formed in a different width from at least one other step.

Abstract: An optical-pickup apparatus comprising: a laser-light source including first-and-second-light-emitting points for laser lights with first-and-second wavelengths which points are disposed at positions deviating in a direction optically corresponding to an optical-disc-tracking direction; a diffraction grating including a plurality of periodic structures which are joined to be different in phase from each other in the direction and each of which includes a recess and projection repeated in a direction optically corresponding to an optical-disc-tangential direction, the diffraction grating being configured to generate main-and-sub-luminous fluxes from the laser light; a holder to hold the diffraction grating to be movable in the direction corresponding to the tracking direction; a collimating lens; an objective lens to focus the main-and-sub-luminous fluxes from the collimating lens on the same track of an optical disc; and a photodetector to be applied with reflected lights of the main-and-sub-luminous fluxes f

Abstract: An optical disk compliant with both a conventional optical disk such as a BD, HD DVD, and the like and a next-generation high-density optical disk according to a near-field light recording system and the like is provided. An information recording medium includes a first information recording layer and a second information recording layer, to/from which information is recorded or reproduced using laser beam. The first information recording layer is formed at a laser beam entrance surface, and is configured so that information can be recorded thereupon and/or reproduced therefrom using a first objective lens having a first numerical aperture NA1 and laser beam of a first wavelength ?1. The second information recording layer is formed so as to have a distance to the laser beam entrance surface is 0.05 mm to 1.

Abstract: The recording accuracy of information on an optical disc is increased. An information optical system (150) of an optical disc apparatus (110) enables a semiconductor laser (3) to sequentially output specific peak light (LEP) and specific slope light (LES) as an information light beam (LM) and enables the correction lens (162) to change the divergence angle of the specific peak light (LEP) so that an absorption change area (RA) by the specific peak light (LEP) can be positioned at a far position in the recording layer (101). Thus, it is possible to form an energy concentration area (RE) by the specific slope light (LES) in the vicinity of a target position (QG), and the recording accuracy of information on the optical disc (100) can be increased.

Abstract: In a small-sized optical pickup device for enabling to obtain a stable servo-signal, as well as, a focus error signal and a tracking error signal, without receiving ill influences of stray lights from other layers, when recording/reproducing a multi-layer optical disc, a reflection light from the multi-layer optical disc is divided into plural numbers of regions by a diffraction grating. And, it is divided into at least four (4) regions, by a division line in the tangential direction of the optical disc and a division line in the radial direction thereof. Light receiving parts, for detecting either one of grating diffraction lights, i.e.

Abstract: An optical-pickup hologram element has six regions on an x-y plane, divided as follows: the first region with a first line (an x-axis) and a second line that connects points (?xa, 0) and (?xb, yb); the second region with the first and second lines and a third line connecting points (xa, 0) and (xb, yb); the third region with the first and third lines; the fourth region with the first line and a fourth line connecting the point (xa, 0) and a point (xb, ?yb); the fifth region with the first and fourth lines and a fifth line connecting the point (?xa, 0) and a point (?xb, ?yb); and the sixth region with the first and fifth lines (xa<xb and ?xb<?xa). The second and fifth, and the other regions are given astigmatism at different angles to the second line.

Abstract: An optical pickup for irradiating an information recording medium, such as a DVD, with a laser beam when an information signal is recorded or reproduced, and information equipment provided with the optical pickup. The optical pickup is capable of recording or reproducing an information signal with higher accuracy, while reducing an influence of stray light in an information recording medium, such as a multilayer type optical disc.

Abstract: A tracking signal and a focusing signal are stabilized by eliminating multi-layer crosstalk. The diffraction position, with respect to a semiconductor detector, from a center region of a multi-region diffraction grating disposed along the return path of reflection light from the layer of interest is placed further away from the optical axis than the diffraction position from a peripheral part of the diffraction grating. Stray light from other layers is thus prevented from being incident on a sensing region for a peripheral region of the diffraction grating. Further, the area of the semiconductor detector is reduced by dividing the center region.

Abstract: An optical pickup according to the present invention includes: a light source 1d for irradiating an optical disk 4 with light; a lens 3 for converging the light onto the optical disk 4; a photodetector 1c having a plurality of detection regions 1cf, 1ct for detecting light which is reflected from a signal surface of the optical disk 4 and converting the light into an electrical signal; a hologram element 1a having a hologram region 1b for guiding the reflected light to the photodetector 1c; and a light-shielding plate 2 for blocking at least a portion of light transmitted through a region of the hologram element 1a other than the hologram region 1b. The light-shielding plate 2 includes a light shielding portion 2b for blocking light, and an aperture 2a for allowing the light to be transmitted therethrough.

Abstract: An optical pickup apparatus is provided with: an astigmatic element for introducing astigmatism to a reflected light from a recording medium; and an optical element for varying advancing directions of luminous fluxes within four different luminous flux regions with one another, out of the reflected light, so as to scatter the luminous fluxes within the four luminous flux regions with one another. When an intersecting point of two mutually crossing straight lines respectively parallel to a first direction by the astigmatic element and a second direction vertical to the first convergence direction is aligned to an optical axis of the reflected light, the two luminous flux regions are placed in a direction where a set of vertical angles created by the two straight lines forms a line, and the remaining two luminous flux regions are placed in a direction where the other set of vertical angles forms a line.

Abstract: A compact and inexpensive optical head that enables stable compatible playback and compatible recording with optical discs of different kinds with the use of a single objective lens is achieved. The order of diffracted light at which the diffraction efficiency by a diffraction element forming the objective lens becomes the maximum is set to the third order for blue light, the second order for red light, and the second order for infrared light in the inner peripheral portion of the diffraction element, and to the sixth order for blue light, the fourth order for red light, and the third order for infrared light to limit the aperture for infrared light in the intermediate peripheral portion. In the outer peripheral portion, the aperture for red light is limited by setting the order to an integer other than multiples of 3 for blue light.

Abstract: An optical pickup includes: a first emission unit emitting an optical beam with a first wavelength corresponding to a first optical disc; a second emission unit emitting an optical beam with a second wavelength, which is longer than the first wavelength, corresponding to a second optical disc different from the first optical disc; a third emission unit emitting an optical beam with a third wavelength, which is longer than the second wavelength, corresponding to a third optical disc different from the first and second optical discs; a condensing optical device condensing, on a signal recording surface of a corresponding optical disc, the optical beams emitted from the first to third emission units; and a diffraction unit provided in the condensing optical device, which is disposed on the optical path of the optical beams with the first to third wavelengths.

Abstract: An optical pickup device has an astigmatism element, a polarization setting element, and a polarizer. The astigmatism element converges laser light reflected on a disc in a first direction and a second direction to form a first focal line and a second focal line. The polarization setting element makes polarization directions of light fluxes different from each other, the light fluxes being obtained by dividing a light flux of the laser light transmitted through the astigmatism element into two by a straight line parallel to the first direction. The polarizer transmits light having polarization directions obtained by inverting the polarization directions set by the polarization setting element with respect to the straight line parallel to the first direction, respectively.

Abstract: Light emitted from a radiation light source 1 passes through a diffraction grating 3a and is separated into transmitted light a and +1st/?1st order diffracted lights b, c. These lights are collected through an objective lens 7 on tracks of an optical disc 8 in a partially overlapped state. Light reflected by the tracks passes through the objective lens 7 and is incident upon light diverging means 13a. Subsequently, light corresponding to the transmitted light “a” diverges into two light beams that are respectively incident upon light detection regions A1, A2, light corresponding to the diffracted lights “b” and “c” respectively diverges into two light beams that are respectively incident upon light detection regions B1, B2, and C1, C2. A tracking error signal associated with the tracks of the optical disc 8 is generated by combining signals detected in the light detection regions A1, A2, B1, B2, C1, and C2.

Abstract: An optical pickup includes a light source configured to emit light, a beam splitter configured to transmit or reflect light, an object lens configured to condense the light transmitted by the beam splitter onto an optical storage, and a diffraction grating having a first grating pattern and a second grating pattern. The first grating pattern is configured to diffract and divide the light reflected by the optical storage into a main beam and two sub beams. The second grating pattern is configured to diffract the light along a different diffracting direction than the first grating pattern. A condensing lens is configured to generate astigmatism to the light diffracted by the first grating pattern, and a light sensor is configured to receive the light via the condensing lens and detect a tracking error signal.

Abstract: An optical pickup apparatus comprising: a laser-light source that selectively emits first and second laser lights parallel with each other; a diffraction grating that includes a plurality of periodic structures joined to be different in phase from each other in a direction optically corresponding to an optical-disc-tracking direction, and generates 0th-order and ±1st-order-diffracted lights by diffracting the first or second laser light; an objective lens that focuses the 0th-order and ±1st-order-diffracted lights generated from the diffraction grating on the same track of the disc; and a photodetector to which reflected light of the 0th-order and ±1st-order-diffracted lights focused on an optical disc is applied through the objective lens, and which generates a differential-push-pull signal, a direction of a straight line connecting light-emitting points of the first and second laser lights in the laser-light source being inclined relative to the direction optically corresponding to the optical-disc-tracking

Abstract: A grating portion has a plurality of convex portions provided on at least one principal plane of a transparent substrate having a first layer containing a first transparent material and a second layer containing a second transparent material, and extended in parallel to each other in a first direction as well as periodically arranged in a second direction orthogonal to the first direction. A filling portion fills a third layer containing a third transparent material at least between the plurality of convex portions. Assuming that the change rate of the refractive index with the change of temperature of the first transparent material is ?A, the change rate of the refractive index with the change of temperature of the second transparent material is ?B, and the change rate of the refractive index with the change of temperature of the third transparent material is ?C, the relationship ?A<?C<0 and |?C|>|?B| is satisfied.

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: Provided is an optical pickup device capable of stabilizing a tracking signal and a focusing signal and of preventing quality deterioration of a data signal by eliminating a multi-layer crosstalk. Of reflected lights from a multi-layer disc, a reflected light from a target layer is split into two by a light flux splitting optical system so that the reflected light is spread out toward two directions with respect to a central line, and then the split lights are condensed. In this case, a reflected light from another layer does not reach a condensing position of the reflected light from the target layer, and only the reflected light from the target layer can be detected by a detector. Accordingly, a crosstalk from the another layer is eliminated.

Abstract: An optical pick-up which permits the relative position of a diffracting optical element and a photodetector to be adjusted by feedback control with signals which are generated when more than one kind of diffracted light differing in order is received, the diffracted light occurring as the reflected light from the optical disc is divided and diffracted by the diffracting optical element having multiple regions. The photodetector which detects the light beam passing through the central region of the diffracting optical element and generates RF signals is juxtaposed with sub-photodetectors, so that they receive reflected stray light from out-of-focus layers and perform computation to calculate the reflected stray light component which the RF signal detector receives, thereby detecting only the component of signals of the reflected light from a target layer.

Abstract: A near-field detection optical component operating in transmission. It includes at least one portion (11b) forming at least one grating (11) of diffraction microstructures (11a) succeeding one another over several periods (p), this grating (11) being capable of converting evanescent waves (16), which are established between the component and an object (12) located in the near field, when it reflects or emits radiation having a wavelength, into propagating waves (16?) by a diffraction effect during transmission through the portion (11b) forming the grating (11) of diffraction microstructures (11a). The period (p) of the grating (11) being of the order of magnitude of the wavelength of the radiation.

Abstract: An embodiment generally relates to an optical device suitable for use with an optical medium for the storage and retrieval of data. The optical device includes an illumination means for providing a beam of optical radiation of wavelength ? and an optical path that the beam of optical radiation follows. The optical device also includes a diffractive optical element defined by a plurality of annular sections. The plurality of annular sections having a first material alternately disposed with a plurality of annular sections comprising a second material. The diffractive optical element generates a plurality of focal points and densely accumulated ray points with phase contrast phenomena and the optical medium is positioned at a selected focal point or ray point of the diffractive optical element.

Abstract: An optical pickup for irradiating an information recording medium, such as a DVD, with a laser beam when an information signal is recorded or reproduced, and information equipment provided with the optical pickup.

Abstract: An optical pickup device including: a laser diode for emitting laser light; an objective lens which irradiates an optical beam emitted from the laser diode; an actuator which displaces the objective lens in a radius direction of the optical disc; a grating for branches an optical beam reflected by an information recording layer into plural regions; and one photodetector having plural light receiving parts for receiving the branched optical beams, wherein the photodetector has a first light receiving part which detects zero-th order grating diffracted light and plural second light receiving parts which detecting grating diffracted light having an order not less than that of ±first order grating diffracted light; a detected signal of the zero-th order grating diffracted light is defined as a reproduction signal; and a detected signal of the grating diffracted light is defined as a signal for servo controlling.

Abstract: To provide a liquid crystal optical modulation element which is excellent in durability against blue laser and which can maintain the characteristics for a long period of time. A liquid crystal optical modulation element to modulate a laser beam having a wavelength of at most 500 nm, which comprises a layer of a polymer liquid crystal composition sandwiched between a pair of transparent substrates facing each other, characterized in that each of the pair of transparent substrates has an alignment film on the surface which faces the other transparent substrate, and the polymer liquid crystal composition is a polymer liquid crystal containing a hindered amine compound and a hindered phenol compound.

Abstract: A diffraction grating is constituted such that directions of diffraction are disposed asymmetrically with respect to the optical axis, by causing light subjected to aperture restriction to have a difference of one half wavelength in the optical path length by making use of the fact that the difference in the optical path length experienced by the light passing through a diffraction element varies depending on the wavelength. With this constitution of the diffraction grating, aperture restriction is applied to both the light focused on an optical disk and the light reflected from the optical disk, thereby achieving an optical pickup that is capable of recording/reproducing information on/from optical disks of different types by using a single objective lens. The optical pickup prevents unnecessary light from entering a photodetector and enables the production of diffraction elements at a low cost.

Abstract: There are provided an optical pickup apparatus which can record/reproduce information properly at a time of temperature change or of using a multilayer disc, and an objective lens for use in the same. When temperature changes, spherical aberration resulting from a change in refractive index of objective lens OBJ increases. Therefore, collimation lens CL is moved by uniaxial actuator AC1 in the direction of the optical axis, to make a finite light flux enter objective lens OBJ, which controls the spherical aberration. When a BD is a multilayer disc, spherical aberration also increases at a time of carrying out an interlayer jump from one layer to another in a plurality of information recording surfaces. Therefore, collimation lens CL is moved in the direction of the optical axis corresponding to the increase. The tilt sensitivity of objective lens OBJ is increased to handle that. Thereby, the occurrence of the third-order coma is effectively controlled even when a finite light flux enters objective lens OBJ.

Abstract: An optical pickup apparatus comprising at least: a diffraction grating configured to split first wavelength light into at least a first main beam and first sub-beam, and to split second wavelength light into at least a second main beam and second sub-beam, the diffraction grating including a diffraction surface portion corresponding to the second wavelength light; and a photodetector including a first main light-receiving unit configured to be applied with the first main beam, a first sub-light-receiving unit configured to be applied with the first sub-beam, a second main light-receiving unit configured to be applied with the second main beam, and a second sub-light-receiving unit configured to be applied with the second sub-beam, a distance between the first main light-receiving unit and first sub-light-receiving unit being changed relative to a standardized distance between the first main light-receiving unit and first sub-light-receiving unit.

Abstract: When first-order diffracted beams leak into a region, which is for receiving only a zeroth-order diffracted beam from an optical disc, due to positional displacement between an objective lens and a hologram element, an offset compensation signal includes an AC component, the offset compensation signal preferably including a DC component only. Accordingly, there may be caused deterioration in a modulation degree of the tracking error (TE) signal. A partial light shielding element 110 is formed on a hologram surface 112a along boundaries between a light receiving region (121a), which receives a zeroth-order diffracted beam, and light receiving regions (121b, 121c), which receive the zeroth-order diffracted beam and first-order diffracted beams, so as to cover the light receiving region (121a). Further, the partial light shielding element 110 shifts phases of transmitted light beams by ?, whereby the TE signal is offset-compensated, and the modulation degree can be improved.

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 device, which reduces the size of an optical spot formed on an optical disk, and prevents the degradation of a tracking error signal due to coherent light from a layer adjacent a target recording/reproducing layer of the optical disk. The optical pickup device includes a light source emitting light at a designated wavelength; an object lens concentrating the light incident from the light source thereupon and forming an optical spot on an optical disk having multiple recording layers; and an optical detector receiving the light reflected by the optical disk and detecting a data signal and an error signal, wherein at least one diffraction pattern region partially diffracting or intercepting the light, emitted from the light source and being incident upon the object lens, and the light, reflected by optical disk and being incident upon the object lens, is formed on the object lens.

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 includes a light source emitting a light beam, an objective lens condensing the light beam emitted from the light source onto an optical disc, at least one divergent angle conversion lens (collimator lens) disposed between the light source and the objective lens and changing a divergent angle of the incident light beam, a driving unit (collimator lens driving mechanism) configured to drive the divergent angle conversion lens in a direction of an optical axis, an optical detection device (optical detector) detecting a return light beam reflected at the optical disc, and an environmental change detecting unit (temperature sensor) configured to detect change in environmental temperature, wherein the objective lens is made of a refractive element having, on one surface thereof, a diffraction structure in a stepped shape or a blazed sectional shape, which generates diffraction light providing a spot adapted to perform satisfactory recording and/or reproducing, the objective lens satisfying certai

Abstract: An optical pickup for performing recording and/or playback of information by selectively irradiating the corresponding wavelength optical beam to first through third optical discs having a protection layer with different thickness, includes emission units for emitting first-wavelength through third-wavelength optical beams corresponding to the respective optical discs respectively, a condensing optical device for condensing each wavelength optical beam on an optical disc signal recording face, a divergence angle transformation device, which can be moved in the optical axis direction, for transforming the divergence angle of each wavelength optical beam according to the moved position in the optical axis direction so as to obtain a predetermined divergence angle, and a detector having a common light receiving unit for receiving each wavelength optical beam separated by an optical path separating unit and returned, with the condensing optical device condensing each wavelength optical beam on the corresponding o

Abstract: An optical pickup device includes a diffraction grating 12 for separating a light beam emitted from a semiconductor laser element into at least three light beams. The diffraction grating 12 is divided into three regions by a straight line extending in a direction parallel to a tangent line of a track of an optical information recording medium. A second region 12B is divided into a first sub-block 13 and a second sub-block 14 by a straight line extending in a direction parallel to a radius direction of the optical information recording medium. The first sub-block 13 has a phase difference of approximately 180 degrees from the second sub-block 14. The first region 12A has a phase difference of approximately 90 degrees from the first sub-block 13 and has a phase difference of approximately 180 degrees from the third region 12C.

Abstract: An optical-pickup apparatus comprising: a laser-light source; a diffraction grating including first-and-second regions of periodic structures different in phase from each other and a third region whose periodic structure is different in phase from the first-and-second regions; an objective lens focusing main-and-sub-luminous fluxes generated by the diffraction grating on the same optical-disc track; and a photodetector to receive reflected light of the main-and-sub-luminous fluxes from an optical disc and output a detection signal for generating main-and-sub-push-pull signals, a relationship between an incident light width in the objective lens corresponding to the third region and pupil diameters of the objective lens corresponding to first-and-second wavelengths of laser lights being adjusted so that a ratio of minimum value to maximum value of a differential-push-pull-signal is at substantially 50% or more and a ratio of sub-push-pull-signal level to main-push-pull-signal level is at substantially 15% or m

Abstract: The optical element comprises a first diffraction structure for generating three beams by diffracting light from a light source and a second diffraction structure that exhibits structural birefringence for a prescribed polarized light returning to the light source. The first diffraction structure is formed on a first face of a translucent optical base material and the second diffraction structure is formed on a second face of the optical base material. The optical base material, the first diffraction structure and the second diffraction structure are formed of a single material.

Abstract: In an optical pickup capable of removing inter-layer crosstalk, a dark line that may appear in a central portion of a beam is removed. Thereby, an error in a data signal is reduced. Reflected light from a multi-layer disc is split into two parallel bundles with a splitting optical system in a way that the light is split at a central line. Thereby, when reflected light from a target layer is focused, the reflected light is not influenced from an attenuation element provided on an optical axis.

Abstract: The present invention provides an optical pickup device and optical recording medium information reproduction device that are capable of reproducing information that is recorded on a plurality of kinds of optical discs having different track pitches. With the present invention, an optical pickup device generates a main beam and sub beams that are made up from pairs of semi sub beams, such that the distance in the radial direction between center positions of a pair of semi sub spots on an optical disc where a pair of semi sub beams are formed is an odd multiple of half the track pitch of the optical disc, and the distance in the radial direction between center positions of semi sub spots that correspond to another pair of sub semi sub beams is an odd multiple of half the track pitch of another optical disc.

Abstract: There is provided a diffraction grating including a convex portion and a concave portion which are used for lights having different wavelengths ?1, ?2 and ?3 and are alternately disposed on at least one surface of a substrate with a predetermined pitch. An average refractive index of the convex portion is smaller than an average refractive index of the concave portion. A phase difference in the lights having the wavelength ?1 which transmit the convex portion and the concave portion and a phase difference in the lights having the wavelength ?2 which transmit the convex portion and the concave portion are both substantially the integral multiple of 2?, and a phase difference in the lights having the wavelength ?3 which transmit the convex portion and the concave portion is substantially the non-integral multiple of 2?.

Abstract: An optical head device and an optical disc apparatus of a simple structure capable of canceling an offset in a tracking error signal caused when an objective lens shifts; in the optical head device, a polarizing hologram 104 has first diffraction areas 112 and 113 including a whole of an area irradiated with overlap of a zeroth-order beam of reflection light from an optical disc 1 and positive/negative first-order beams of the reflection light, and a second diffraction area 111 including an area irradiated with the zeroth-order beam of the reflection light and not irradiated with the positive/negative first-order beams of the reflection light without including the first diffraction area; and a photodetector 109 has a first light receiving section 131 for receiving a first light beam which is a zeroth-order beam of diffraction light generated by the polarizing hologram 104, a second light receiving section for receiving a second light beam which is a positive first-order beam of the diffraction light generated

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: Disclosed is a deflection optical element, which makes it possible to deflect an incident light so as to couple the incident light to an optical element disposed in the later stage without deteriorating the optical efficiency. The deflection optical element, which deflects an incident light coming along a first optical axis at a deflection surface and emits an emission light propagating along a second optical axis so as to couple the emission light to either a diffraction grating or a refracting optical system, comprises at least one diffracting surface and at least one reflecting surface, wherein the angle ?n, an angle ?t derived as a total diffraction angle caused by the at least one diffracting surface, and an angle ?a, which is formed at a second intersection of the first optical axis and the second optical axis, fulfill a conditional relationship of: 0??n<?a<?t.

Abstract: An optical head apparatus of an optical information recording/reproducing apparatus is provided with a light source. An objective lens focuses an output light emitted by said light source on a disc optical recording medium for which a groove or a pit for tracking is provided. T photo-detector receives a reflected light reflected by said optical recording medium. A polarizing splitter unit splits said output light and said reflected light. A quarter-wave plate disposed between said polarizing splitter section and said objective lens. A birefringence compensating unit reduces a change in an amplitude of a track error signal caused by birefringence in a protective layer of said optical recording medium.

Abstract: A multiple wavelength-adaptive optical pickup according to the present invention enables to obtain stable signals by suppressing displacement of optical intensity distribution at a light receiving section. When an incident angle of a central beam of a zero-dimensional beam of a beam reflected at an optical disc into a half mirror is taken as ?, if variation in transmittance of the mirror become a maximum with respect to change in the incident angle from ? to a plus side in any one of the wavelengths corresponding to the respective optical discs, a ?1 dimensional beam generated on the minus side with respect to the zero-dimensional beam is received by the light receiving section, and if the variation in the transmittance of the mirror become the maximum with respect to change in the incident angle from ? to the minus side, a +1 dimensional beam generated on the plus side with respect to the zero-dimensional beam is received by the light receiving section.