Abstract: An optical recording device includes a light source, a spatial light modulator, a correcting optical system and a light guiding section. The spatial light modulator includes plural pixels, a signal light region that displays a signal light pattern, and a reference light region that displays a reference light pattern. The spatial light modulator modulates and outputs incident light for each pixel in accordance with a display pattern. The correcting optical system includes a pair of axicon lenses that correct the emitted light from the light source so as to flatten the light intensity distribution thereof on an irradiated surface of the spatial light modulator. The light guiding section guides the corrected light to the spatial light modulator. The signal light and the reference light are irradiated onto an optical recording medium simultaneously and a hologram is recorded into the optical recording medium.

Abstract: The invention described is an apparatus for reproducing information from an information carrier (11) comprising: a waveform equalizer (6) for obtaining a corrected signal (S?) by performing a waveform equalization to a read signal (S), the waveform equalizer (6) having an amplifying element with a gain (K); and gain setting means (1) for reading a numerical gain setting stored on the information carrier (11) and setting the gain (K) of the amplifying element to a value related to the numerical gain setting. By reading the numerical gain setting from the information carrier, the apparatus is able to set the gain (K) of the waveform equalizer to the optimal value for suppressing noise and inter symbol interference. The equalizer can be followed by a limit equalizer, the gain of which can also be wave form read from the information carrier.

Abstract: An optical head has a beam input/output coupler on a planar waveguide and other parts including: a light transmitting element emitting a beam; a planar waveguide formed on a substrate and receiving the beam oscillated from the light transmitting element; a beam input/output coupler integrated as a thin film on a portion of the planar waveguide and receiving the beam through the planar waveguide to transmit the beam vertically toward a disc positioned above the planar waveguide or transmitting the beam reflected from the disc through the planar waveguide; and light receiving elements receiving the beam propagated to the planar waveguide through the beam input/output coupler.

Abstract: There is provided an optical element for an objective optical system of an optical information recording/reproducing device. The objective optical system is configured to satisfy conditions: ?<500; NA?0.7; and f?1.0, and at least one of surfaces of the optical element includes a diffraction structure defined by an optical path difference function ?(h): ?(h)=(P2h2+P4h4+P6h6+P8h8+P10h10+P12h12)m? where P2, P4, P6 . . . denote coefficients of 2nd order, 4th order, 6th order . . . , respectively, h denotes a height from an optical axis of the optical element, and m denotes a diffraction order at which diffraction efficiency for the laser beam is maximized. The diffraction structure satisfies conditions: P2<0??(4); P2×P4<?100??(5); and ?60<P2/P4<0??(6).

Abstract: An optical pickup has a semiconductor laser device that can emit laser beams with different wavelengths. A beam splitter and objective lens direct the emitted beam onto a rotating optical disc. Reflected light returns through the objective lens and beam splitter to a photodetector. A pair of liquid crystal elements on the optical path from the optical disc to the photodetector have controllable lens functions acting in different directions to produce an adjustable astigmatic effect that enables the photodetector to generate a focus error signal with a linear range appropriate for the type of optical disc, the number of signal layers in the optical disc, and the spacing between the layers.

Abstract: According to one embodiment, the invention provides a master recording apparatus and method which can form a pit having a symmetrical pit shape with excellent reproducibility. An embodiment of the invention is a master recording apparatus where a resist film on a master for an optical disk is irradiated with irradiation light from a semiconductor laser to record information on the resist film, where the resist film is formed as an inorganic resist film, and means for outputting the irradiation light from the semiconductor laser as a short pulse laser with a pulse width between 200 ps and 1 ns is provided.

Abstract: An optical pickup apparatus for information recording and/or reproduction on different optical information recording media with compatibility among these media, the optical surface of a first objective lens and the optical surface of a second objective lens are formed only of a refractive surface. The second objective lens is used in common for the first light flux with a wavelength of ?1 and the second light flux with a wavelength of ?2, but in the case where the protective substrate t2 of the second optical information recording medium and the protective substrate t3 of the third optical information recording medium are the same, it is not necessary to take the difference in thickness of the protective substrate into consideration. Chromatic aberration based on the difference in wavelength between the first light flux and the second light flux can be corrected by displacing the second coupling lens.

Abstract: In order that thickness reduction, weight reduction, and mass productivity improvement should be achieved in an objective lens even in the case where NA is high, an objective lens according to the present invention is a bi-convex single lens having at least one aspheric surface, and satisfies conditions: (1) 3.5<DH-S/DH-H?<4.2; (2) 3.5<DH?-T2/DT1-H<50; (3) 0.9<d/f<1.1 (NA?0.85).

Abstract: The present invention relates to a method and a device for determining spherical aberration occurring during reading from and/or writing to optical recording media. According to the invention, a method for determining spherical aberration includes the steps of: splitting the light beam into at least two partial light beams with a volume hologram having stored wavefront patterns with various degrees of spherical aberration; focusing the partial light beams onto respective detectors whereby at least one signal generated by the detectors depends on the positions of the respective partial light beam; and determining the spherical aberration using the signals generated by the detectors.

Abstract: An optical pickup actuator and a method of assembling the same is provided. The method of assembling the optical pickup actuator comprises the steps of providing a blade having at least one objective lens mounting area and an aberration correcting mechanism mounting area, arranging an objective lens in the objective lens mounting area, positioning an aberration correcting mechanism in the aberration correcting mechanism mounting area such that the central point of the aberration correcting mechanism coincides with the central point of the objective lens, tuning the aberration correction mechanism, and adhering the aberration correcting mechanism using an adhesive.

Abstract: The amount of focus offset and the amount of spherical aberration correction are adjusted with respect to a disk on which no data is recorded with high precision. The amount of focus offset and the amount of spherical aberration correction are adjusted on the basis of (1) a focus error signal amplitude, (2) a tracking error signal amplitude in a wide track pitch region, and (3) a rectangular waveform wobble signal envelop level.

Abstract: To provide an optical head and an optical disc device, in which a cover member for radiating and protecting the optical head and a laser light source are of a simple construction, manufacturing efficiency can be increased, and accuracy variation due to assembly of the laser light source such as an optical axis or the like of a laser beam can be suppressed. Therefore, a boss formed on a light source installation portion of a base is engaged with a boss hole formed on a laser light source supporting portion of the cover member, thereby positioning the cover member on the base. In doing so, an internal thread hole formed on the bottom surface of the base is overlapped with a thread hole formed on a cover portion of the cover member. In this state, a bolt is passed through the thread hole to screw in the internal thread hole.

Abstract: An optical pickup compatible with recording media having different formats, the optical pickup includes a light device module having a first light beam source and a second light beam source to emit corresponding first and second light beams having different wavelengths, a hologram light coupler to separately guide the first and second light beams along the same optical path such that the first and second light beams go toward a corresponding one of the recording media, an optical path changing element to selectively alter the optical path of an incident light beam, and an objective lens disposed on an optical path between said optical path changing element the corresponding one of the recording media to focus the first and second light beam on the corresponding one of the recording media, and a photodetector to receive the first and second light beam incident from said optical path changing element.

Abstract: An optical information apparatus of the present invention includes: an optical pick-up head including: a light source; a diffraction unit; a condensing unit; a beam splitter; a photodetector; and a tracking error signal generator. An optical recording medium has tracks arranged substantially at a constant pitch. An average of a pitch is tp. When a main beam is placed on the track, a first sub-beam and a second sub-beam are placed between the tracks.

Abstract: An optical system is described for scanning optical record carriers of different types. The optical system includes a compensator having a number of optical elements (NPS1, NPS2). The optical elements (NPS1, NPS2) are non-periodic phase structures (NPS) having annular areas separated by steps, forming a non-periodic pattern of optical paths of different lengths. By including these multiple optical elements (NPS1, NPS2) having NPS surfaces in the lens system of an optical system, it is possible to compensate for the effect of variation of a parameters such as temperature, angle of incidence, polarisation of radiation incident on the system and wavelength of radiation, without causing sensitivity to variation of another such parameter.

Abstract: An optical information recording apparatus includes a light source that emits an irradiation beam; a spatial light modulator that converts the irradiation beam to an information beam, the information beam having a two-dimensional modulation pattern that carries information and is formed with a plurality of first regions in which each of boundaries is formed with OFF pixels; a phase modulator that includes a plurality of second regions, and that imparts the phases to the irradiation beam or the information beam to modulate phases of the irradiation beam or the information beam; and a light collector that collects the information beam and a reference beam on an optical information recording medium that can record the information as hologram, by using interference fringes produced due to interference between the information beam and the reference beam.

Abstract: An image pickup device which can obtain an image of wide range picked up by a plurality of cameras is provided by preventing occurrence of parallax.

Abstract: An optical pickup 1 includes a collimator lens 13 for changing the shape of a laser light by moving on the optical axis AX from a base point. An objective lens 15 is set so as to form a spot of which size, when the collimator lens 13 is located at the base point, is minimum at a point apart from the light source side surface of an information recording medium 20 by a distance of Lc defined by an expression (1): Lc=(L0+Ln)/2??(1), wherein Lc is named as a thickness to the designed center; L0 is a distance between the light source side surface of the information recoding medium and an information recording face located nearest to the light source side surface; and Ln is a distance between the light source side surface of the information recording medium and an information recording face located farthest from the light source side surface.

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 system has an optical functional surface including a common region used for conducting information recording and/or reproducing for both of a first optical information recording medium and a second optical information recording medium. The common region comprises a refractive surface of an imaginary basic aspherical surface and a optical path difference providing structure in which plural ring-shapes zones are separated around the center of an optical axis and neighboring ring-shaped zones are displaced to each other in a direction of an optical axis so as to cause an optical path difference obtained by multiplying a predetermined wavelength ?s (?1<?s<?2) with almost an integer. The refractive surface of the imaginary basic aspherical surface is structured such that a spherical aberration becomes under on the first information recording medium and a spherical aberration becomes over on the second information recording medium.

Abstract: The present invention relates to an optical element for an optical pickup device, wherein the optical element is produced by molding a resin material, in which inorganic particles having a diameter of not more than 30 nm are dispersed in a plastic resin, an optical pickup device using the optical element, and a producing method of the optical element.

Abstract: An adhesive positions a beam shaping element in such a manner as to satisfy the following relational expressions (1) and (2): 0<L??WA/(?·?·SAS)??(1) SAS=1000(0.5 m2+1.5 m?2)[m?/mm]??(2), if it is assumed that m is the beam shaping magnification of a beam shaping element, L[mm] is the distance from a light source side surface of the beam shaping elements to a center position of the adhesive, ?[1/K] is the linear expansion coefficient of a light source retaining holder, ?WA[m?] is amount of astigmatic aberration caused by the beam shaping element, and ?T[K] is an environmental temperature variation amount.

Abstract: An optical information apparatus of the present invention includes: an optical pick-up head including: a light source; a diffraction unit; a condensing unit; a beam splitter; a photodetector; and a tracking error signal generator. An optical recording medium has tracks arranged substantially at a constant pitch. An average of a pitch is tp. When a main beam is placed on the track, a first sub-beam and a second sub-beam are placed between the tracks.

Abstract: This invention relates to an optical disc assembly capable of receiving an insert upon which an analyte of interest may be disposed. The optical disc assembly can be read by an optical disc reader, such as by a standard CD or DVD reader, and the analyte disposed on the insert can be detected by the optical disc reader. The optical disc assembly may have one or more data layer in which operational information or assay information is encoded. Hologram may be used to encode operational information or assay information.

Abstract: An aberration correction apparatus includes an optical pickup having a liquid crystal panel for correcting an aberration of a light beam emitted from a light source and irradiated on a recording medium and a control unit which applies, to the liquid crystal panel, a bias voltage in order to correct the aberration. The bias voltage is a voltage at which a diffraction generated in the light beam passing through an electrode gap portion between electrode portions of the liquid crystal panel is minimum. For instance, the bias voltage is the voltage at which a phase difference between the light beam passing through the electrode portions of the liquid crystal panel and the light beam passing through the electrode gap portion is an integral multiple of a wavelength of the light beam. It is thereby possible to prevent unnecessary diffracted light from being generated by the liquid crystal panel for correcting the aberrations.

Abstract: To achieve stable, high capacity, high speed recording. Of two light beams emitted from a light irradiation means, one or two beams are made pass through an optical path changeable member whereof at least one of the thickness and refractive index changes continuously or in two or more steps immediately after emission from the light irradiation means, so that a difference is introduced into the optical path length of the two beams, and the focusing point of one beam is made to vary to coincide with a position in the recording layer used for playback or recording. Another light beam is used for servo. Converging of light during recording or read of a multilayer recording medium is performed with higher precision than in the prior art, so higher density, higher capacity recording/playback can be performed.

Abstract: An optical pickup includes: a laser light source which outputs an divergent beam having an elliptical far-field pattern; a beam shaping element having at least one cylindrical plane and which shapes the divergent beam outputted from the laser light source into an divergent beam having a prescribed shape in which at least the length in the major axis direction of the elliptical shape is shortened; a light collecting portion having a beam splitter which perpendicularly collects the divergent beam that is outputted from the beam shaping element and which has a prescribed shape on the recording surface of an optical disk, and a mirror or the like; and a light detecting portion The optical axis of the divergent beam is rotated so that the direction in which the major axis of the divergent beam having a prescribed shape is shortened conforms to the radial direction of an optical information recording medium.

Abstract: A plurality of light-emitting elements 9a, 9b, 10a each emitting laser beam of a wavelength of approximately 405 nm, approximately 660 nm or approximately 780 nm corresponded to each of a plurality of types of disc-formed medium 100, and an objective lens 18 condensing each laser beam emitted from the plurality of light-emitting elements so as to form an elliptic beam spot on a recording surface of the disc-formed recording medium are provided, wherein a long axis of a beam spot of the laser beam having a wavelength of approximately 660 nm is aligned in a direction 45° to 65° away from the tangential direction of the disc-formed recording medium, and a long axis of a beam spot of the laser beam having a wavelength of approximately 405 nm is aligned in a direction 25° to 45° away from the tangential direction of the disc-formed recording medium.

Abstract: An apparatus for effecting at least one of recording and reproducing information includes first and second light sources having light intensity and for emitting a light beam having an emission wavelength different from each other, first and second photodetectors capable of generating an output, an optical system configured to guide a light beam emitted from the first light source to a recording medium and to guide a light beam reflected from the recording medium to the first photodetector, a separating optical element configured to guide a light beam emitted from the first light source to the second photodetector, the second photodetector receiving the light beam and generating an output based on the received light beam, and a control circuit for receiving the output generated by the second photodetector, and being configured to control the light intensity of the first light source based on the output of the second photodetector.

Abstract: To improve reliability in controlling an output of a semiconductor laser. There are provided a prism adhered to the semiconductor substrate, and having a light reflection surface formed with a light reflection film for reflecting a laser beam emitted from the semiconductor laser and a light transmission surface for transmitting a laser beam emitted from the semiconductor laser outside an aperture range of the objective lens; a monitor photoreceptor disposed in an area of the semiconductor substrate where the prism is disposed, and receiving the laser beam transmitted through the light transmission surface of the prism; and a signal detection photoreceptor disposed outside the area of the semiconductor substrate where the prism is disposed, for receiving, as return light, a laser beam reflected at the light reflection surface of the prism and converged upon the record surface of the disk-shaped recording medium via the objective lens.

Abstract: An optical head comprises first and second light sources which are arranged next to each other and emit lights of different wavelengths and an optical device which is arranged between the first and second light sources and a conversing lens for reducing the spherical aberration caused by combination of the conversing lens and at least one of first and second optical recording media which correspond to at least one of the lights of first and second wavelengths. The optical axis of the optical device is shifted with respect to the optical axis of the conversing lens in order to reduce the coma aberration that is caused since at least one of optical axes of the lights of first and second wavelengths does not coincide with the optical axis of the conversing lens.

Abstract: Provided is an optical pickup device in which the deterioration of optical characteristics of a laser light beam due to a deviation of an optical axis can be smoothly suppressed with a simple structure. An objective lens becomes a finite system for only a laser light beam for CD (780 nm in wavelength). A three-wavelength laser is disposed such that an optical axis of the laser light beam for CD is aligned with an optical axis of an optical system including a polarization BS to an optical axis correcting element. In this case, the large deterioration of the optical properties of the laser light beam for CD, which cannot be sufficiently compensated even if the objective lens is tilted, does not occur. A stable recording and reproducing operation using the laser light beam for CD can be performed.

Abstract: Provided are an optical disk drive and a disk format necessary for the optical disk, which are capable of eliminating or reducing a problem of reduction in an effective transfer rate attributable to track jumps caused at a certain interval when performing recording and reproduction of multiple tracks in parallel by using multiple beams, and thereby achieving a high transfer rate. A block constituting a recording unit is divided into sub-blocks, and the sub-blocks are arranged in a radial direction of a disk. Meanwhile, an optical disk drive includes a means for irradiating a disk with multiple light spots, a means for pulse modulating the spots by using the same frequency and different phases, and a means for receiving light from the spots reflected by the disk by using a single photodetector, and separating the reflected light into independent lines of signals in terms of a time domain.

Abstract: In order to provide an optical pickup device, an objective optical element and an optical information recording and reproducing device that can properly record and/or reproduce information with three different recording densities and that can be realized with a simplified structure and at low cost, the optical pickup device is comprised of an optical element, the construction of which is stacked with first, second and third basic structures to make different optical lengths.

Abstract: An optical information processor reads information from a storage medium or writes information on a storage medium by irradiating it with light radiated from a light source. The processor includes: the light source for radiating the light; a condensing element for converging the light, radiated from the light source, toward the storage medium; and a detector for detecting a portion of the light radiated from the light source. Supposing that in a far-field pattern of the light radiated from the light source, an aperture area A is defined by a portion of the light entering the condensing element and a photosensitive area B is defined by another part of the light entering the detector and that the light has the narrower angle of radiation in an x direction and the wider angle of radiation in a y direction, respectively, the center of the photosensitive area B in the x direction is offset with respect to that of the far-field pattern in the x direction.

Abstract: An optical scanning device for scanning a multi-layer optical record carrier when positioned in a scanning location in the device, the device being adapted for scanning a first information layer at a first information layer depth within the record carrier and a second information layer at a second information layer depth within the record carrier. The device comprises: a radiation source for generating a radiation beam; an objective lens, located in an optical path between the radiation source and the scanning location, for converging a radiation beam to a spot on an information layer; and-an optical switching arrangement switchable between a first state, in which the device is arranged to scan a said first information layer, and a second state, in which the device is arranged to scan a said second information layer.

Abstract: A recording and reproducing apparatus includes a light source to emit a laser beam, an information light beam irradiation unit to irradiate a medium with an information light beam, a reference light beam irradiation unit to irradiate the medium with a reference light beam so as to form a specific speckle pattern on the medium. The reference light beam irradiation unit comprises a diffusion board provided in the way of a light path through which the laser beam is passed and generating the reference light beam, a rotation controller to rotate the diffusion board, and an identification information detector to detect identification information previously formed on a surface of the diffusion board. The diffusion board comprises a plurality of encode storage regions in which different identification information is formed and a plurality of diffusion pattern generation regions specified by the identification information.

Abstract: The present invention provides an objective lens for optical pick-up devices in which the amount of change in the astigmatic aberration is small when there is a temperature distribution that is not circularly symmetric with respect to the optical axis within an objective lens constructed with at least two optical elements and which permits stable and high-speed information recording and reproduction with high-density optical disks, and to provide further an optical pick-up device provided with such an objective lens, and an optical information recording and/or reproducing apparatus employing such an optical pick-up device.

Abstract: An objective optical element for use in an optical pickup apparatus having: a first light source for emitting a first light flux; a second light source for emitting a second light flux; an objective optical element, the objective optical element includes: an optical surface including a common area and an exclusive area; and a wavelength selective film formed on at least one of the common area and the exclusive area; wherein the common area transmits the first light flux which is formed into a converged spot on the information recording surface, and transmits the second light flux which is formed into a converged spot on the information recording surface, and the exclusive area transmits the first light flux which is formed into a converged spot on the information recording surface, and transmits the second light flux which is not formed into a converged spot on the information recording surface.

Abstract: An information-recording medium having a substrate and a recording part formed on the substrate allowing three-dimensional formation of recording pits, the recording part, comprising multiple recording layers, in which the recording pits are formed with a converged recording light at a wavelength of ?2 and reproduced with a converged reproducing light with a wavelength ?1 shorter than the wavelength ?2, and intermediate layers alternately laminated between the recording layers, wherein the reflectance at the recording light wavelength of ?2 in the unrecorded region is smaller than the reflectance at the reproducing light wavelength of ?1 in the unrecorded regions of the recording layers.

Abstract: An optical pickup apparatus for reading and writing information from and to optical data media in different formats and a method thereof are provided. The optical pickup apparatus comprises a twin laser diode (Twin LD), a diffraction element for dividing a laser beam incident on a data medium into five beams, and an optical detector for focusing a laser beam reflected from the data medium to detect an information signal and signals for carrying out servo controls. The divided beams are focused on a predetermined location in based on a data medium format, and the beam reflected from the data medium is received on and detected from the corresponding photodiodes of the optical detector so that a focus error signal and a tracking error signal are generated.

Abstract: A beam irradiation device includes a light source for emitting laser light, an actuator for displacing a propagation direction of the laser light in accordance with a control signal, and a scan expansion lens for increasing a swing width of the laser light to be generated by the actuator. A spectral element is arranged between the actuator and the scan expansion lens. The spectral element allows at least a part of the laser light to be incident from the actuator to transmit, and reflects at least a part of the laser light to be incident from the scan expansion lens. The beam irradiation device further includes a light detector for receiving the laser light to be reflected on the spectral element to output an electrical signal.

Abstract: According to one embodiment, the invention provides an optical disk device having an irradiation section which applies a laser beam to an optical disk, a detection section which receives a reflected light emitted from the irradiation section and reflected from the optical disk to output a detection signal, and a discrimination section which performs focus search using the irradiation section and the detection section and determines whether the optical disk is a triple layer optical disk on the basis of the detection signal upon performing focus search.

Abstract: Two optical discs used with a laser light having the same wavelength but having different substrate thicknesses can be handled by a single optical disc apparatus and a multilayer optical disc can also be reproduced. A refractive lens unit and liquid crystal elements are provided so as to condense laser light on an optical disc having a thin substrate thickness with a first NA and to condense laser light on an optical disc having a thick substrate thickness with a second NA smaller than the first NA. The refractive lens unit is designed such that the amount of RMS wavefront aberration is minimized with respect to an intermediate substrate thickness between the two optical discs in the range of the second NA; and the RMS wavefront aberration is 0.05? or less with respect to the substrate thickness of the optical disc in an area outside the second NA. A liquid crystal element for compatibility corrects spherical aberration due to the difference in substrate thickness between the two optical discs.

Abstract: It is an object of the present invention to maintain a light flux separating unit in a stable state with a high positioning accuracy relative to a physical deformation when the light flux separating unit is attached or a great temperature change after the light flux separating unit is attached, in an optical pickup device including in a casing a projection optical system, a light receiving optical system and the parallel flat plate shaped light flux separating unit that separates a light flux advancing in the light receiving optical system from a light flux advancing in the projection optical system. In the present invention, the light flux separating unit 23 fixes at least two parts of two surfaces opposed to each other to attaching parts 2C and 2D provided in a floor surface 2A side of the casing and a wall surface 2B side vertical thereto by two kinds of adhesive agents 41 and 42 whose hardness is respectively different after curing.

Abstract: An optical-pickup slider is characterized in that a light-transmitting-property substrate is bonded to a surface of a layer having a tapered through hole, on which surface a larger opening of the tapered through hole exists. Thereby, it is possible to prevent the layer having an aperture from being destroyed. A method of manufacturing the optical-pickup slider comprises the steps of a) making a tapered through hole in a layer layered on a first substrate and having a thickness smaller than that of the first substrate; and, after bonding a light-transmitting-property substrate to a surface of the layer, removing the first substrate so as to expose an aperture at a tip of the tapered through hole.

Abstract: An objective optical element for use in an optical pickup apparatus for recording and/or reproducing information on first—third optical information recording media using first—third light fluxes respectively, includes: a first phase structure for compensating a deterioration in a performance forming the converged spot on the information recording surface of the first optical information recording medium caused by an temperature change, a second phase structure for reducing a spherical aberration based on a thickness difference between the protective substrates of the first and second optical information media or the a wavelength difference between the first and second wavelengths, and a third phase structure for reducing a spherical aberration based on a thickness difference between the protective substrate of the first and third optical information media.

Abstract: A method is disclosed to determine an optimal optical detector orientation to decode information encoded holographically. The method supplies a matched filter, an orientation image, a holographic data storage medium encoded with the orientation image, and an optical detector comprising a moveable input screen comprising a plurality of detector elements. The method positions the input screen in a plurality of input screen orientations and calculates a correlation factor for each of the input screen orientations. The method determines an optimal optical detector orientation using the plurality of correlation factors.

Abstract: An optical head to access data on an optical recording medium, which has two data storage densities, includes two sets of optical path systems to provide two optical paths that are crossed. Each optical path system includes a laser light generation unit, a light guiding unit, a converging objective lens and a photo detector. The light guiding unit is located on the optical path of the laser light generation unit, to direct the laser light to pass through the converging objective lens and focus on the data side of the optical recording medium to carry optical data signals from the data side. The laser light returns to the light guiding unit and travels along the optical path and is received by the photo detector.

Abstract: An optical element for optical pickup device is provided with an optical path difference providing structure which provides a substantial phase change to a light flux having a predefined wavelength. The optical path difference providing structure is provided with a step portion having a smaller step difference than the predefined wavelength in an optical axis direction.