Abstract: A display system comprises a waveguide having light incoupling or light outcoupling optical elements formed of a metasurface. The metasurface is a multilevel (e.g., bi-level) structure having a first level defined by spaced apart protrusions formed of a first optically transmissive material and a second optically transmissive material between the protrusions. The metasurface also includes a second level formed by the second optically transmissive material. The protrusions on the first level may be patterned by nanoimprinting the first optically transmissive material, and the second optically transmissive material may be deposited over and between the patterned protrusions. The widths of the protrusions and the spacing between the protrusions may be selected to diffract light, and a pitch of the protrusions may be 10-600 nm.

Abstract: A display system comprises a waveguide having light incoupling or light outcoupling optical elements formed of a metasurface. The metasurface is a multilevel (e.g., bi-level) structure having a first level defined by spaced apart protrusions formed of a first optically transmissive material and a second optically transmissive material between the protrusions. The metasurface also includes a second level formed by the second optically transmissive material. The protrusions on the first level may be patterned by nanoimprinting the first optically transmissive material, and the second optically transmissive material may be deposited over and between the patterned protrusions. The widths of the protrusions and the spacing between the protrusions may be selected to diffract light, and a pitch of the protrusions may be 10-600 nm.

Abstract: The present invention belongs to the technical field of underwater communication, and provides a novel highly robust underwater optical communication system which comprises a sending module and a receiving module. The novel highly robust underwater optical communication system realizes highly robust underwater optical communication under strong interference of sunlight and artificial light sources. The system uses a new physical method irrelevant to frequency, and can be used with existing MIMO and CDMA to obtain better communication effects. The circularly polarized light is used for signal transmission, thereby avoiding the problem of channel misalignment caused by the rotation of a platform underwater. At the same time, good polarization maintaining of a marine environment makes the signal characteristics difficult to lose.

Abstract: The present set of embodiments relate to a system, method, and apparatus for an optical configuration in a flow cytometer that allows for independent adjustment of focusing for each light source. Such systems, methods, and apparatuses require a final focusing element to be moved near the beginning of the optical train and for each optical element coming after the final focusing element to be configured to accommodate converging light beams while minimizing the introduction of aberrations into those beams.

Abstract: Disclosed is a measurement apparatus including: a support mechanism configured to support a cartridge in which a chamber is formed, the chamber being configured to store a measurement sample that generates light an intensity of which varies depending on an amount of a test substance; a photodetector configured to detect the light generated from the measurement sample stored in the chamber; and a reflection member provided between the photodetector and the cartridge supported by the support mechanism, the reflection member having an inner face, the reflection member being configured to reflect, at the inner face, the light generated from the measurement sample stored in the chamber, and guide the light to the photodetector, wherein the reflection member is configured to have an area surrounded by the inner face, the area decreasing from a side where the cartridge supported by the support mechanism is provided toward a side where the photodetector is provided.

Abstract: An optoelectronic device includes a semiconductor substrate and a vertical-cavity surface-emitting laser (VCSEL) light source formed on the substrate and configured to emit coherent light at a predefined wavelength along a beam axis perpendicular to a surface of the substrate. A block of a transparent material is mounted on the surface of the substrate and forms, with the VCSEL, a resonant cavity at the predefined wavelength having an entrance face that is aligned with the beam axis and an exit face that is laterally displaced with respect to the entrance face along a cavity axis running parallel to the surface of the substrate.

Abstract: There is provided an optical medium reproducing device configured to optically reproduce an optical medium including a plurality of tracks formed, the optical medium reproducing device including: an optical filter configured to receive an incident returned light beam from the optical medium, and to spatially and optically form a plurality of signals having different bands in a tangential direction and a radial direction; an arithmetic unit configured to operate the plurality of first signals formed by the optical filter so as to form a plurality of channels of second signals; and an electrical filter configured to individually receive the second signals, and to perform processing to the second signals so as to acquire a reproduced signal.

Abstract: A system for an extreme ultraviolet light source includes one or more optical elements positioned to receive a reflected amplified light beam and to direct the reflected amplified light beam into first, second, and third channels, the reflected amplified light beam including a reflection of at least a portion of an irradiating amplified light beam that interacts with a target material; a first sensor that senses light from the first channel; a second sensor that senses light from the second channel and the third channel, the second sensor having a lower acquisition rate than the first sensor; and an electronic processor coupled to a computer-readable storage medium, the medium storing instructions that, when executed, cause the processor to: receive data from the first sensor and the second sensor, and determine, based on the received data, a location of the irradiating amplified light beam relative to the target material in more than one dimension.

Abstract: An optical system capable of obtaining a high-resolution image using interference and thus capable of providing a stable signal is realized. A particular polarization state of response light emitted from an object is selected, and light in the selected particular polarization state is split into two beams. The split two beams are polarized into two different polarization states. After one of the two beams is subjected to an image inversion, the two beams are condensed such that they interfere with each other. The interfering light is split into a plurality of beams, and each of these beams is detected after they are passed through different polarizing filters. Detected signals are combined together and processed to obtain high-stability amplitude information without being influenced by a phase difference between the two beams.

Abstract: Multi-level recording is quite effective for attaining a larger capacity and a higher transfer rate in the case of an optical disk; however, with conventional technologies, a SIGNAL-TO-NOISE RATIO of a signal deteriorates along with an increase in a multi-level degree, creating a factor for limitations to the multi-level degree. In order to solve problems, when optical information is recorded by use of a standing wave occurring due to interference between two light beams, at least one of the two light beams is modulated in multi-stages. Further, at the time of regeneration, a regeneration reference beam is caused to interfere with respective polarization components of a regeneration beam, the polarization components being orthogonal to each other, thereby concurrently generating not less than three interference beams differing in interference phase from each other before being detected.

Abstract: An optical information reproducing apparatus and an optical information reproducing method using the same are provided. The optical information reproducing apparatus includes: a reference beam providing unit which inputs a reference beam to a reproduction recording area to be reproduced and a peripheral recording area around the reproduction recording area on an optical information recording medium, a peripheral beam detecting unit which transmits a reproduction beam reproduced from the reproduction recording area in response to the reference beam and detects a peripheral beam reproduced from the peripheral recording area, a tracking servo unit which analyzes optical information of the detected peripheral beam and controls a tracking position, and a reproduction beam detecting unit which detects the reproduction beam having pass through the peripheral beam detecting unit.

Abstract: Optical devices based on internal conical refraction for developing new set-ups, methods and applications based on the specific properties of internal conical diffraction. The devices include several set-ups, methods and applications consisting of biaxial crystal(s)—one or more polarization elements and optical elements. The biaxial crystal is an optical crystal which may belong to the trigonal, orthorhombic or trigonal crystal classes.

Abstract: An optical pickup device includes a polarization diffraction grating to diverge an optical beam reflected from an optical disc and an optical detector to receive the optical beam diverged by the polarization diffraction grating, a polarization of 0 order diffracted light diffracted through the polarization diffraction grating is substantially perpendicular to that of a +1 order diffracted light diffracted therethrough, and a polarization filter having a plurality of domains is mounted between the polarization diffraction grating and the optical detector.

Abstract: In an optical pickup for an optical disk device using BD, DVD and CD as recording media, simplification of constitutional elements is promoted. The optical pickup includes a dual wavelength type laser beam source generating laser beams for DVD and CD, a single wavelength type laser beam source generating a laser beam for BD, and a first wave plate converting the laser beam for BD generated from the laser beam source concerned into circular polarization. It further includes a second wave plate converting the laser beam for DVD generated from the dual wavelength type laser beam source into 45-degree linear polarization. Favorable recording and reproduction are performed by radiating the laser beam to the recording medium concerned as the circular polarization for BD and the 45-degree linear polarization for DVD.

Abstract: A disclosed optical element includes three or more sub-wavelength convexo-concave structures having pitches less than a wavelength of an incident light incident to the optical element and having groove depths equal to each other and a periodic structure having the three or more sub-wavelength convexo-concave structures, the pitch of the periodic structure greater than the wavelength of the incident light, in which a predetermined polarization direction of the incident light is diffracted mainly into a specific order.

Abstract: An optical pickup apparatus comprising: a laser light source configured to emit a laser beam; an objective lens configured to apply the laser beam to an optical recording medium; and a beam splitter including a first reflective film configured to reflect the laser beam so as to be directed to the objective lens, the beam splitter interposed in an optical path between the laser light source and the objective lens, an incidence polarization angle of the laser beam relative to the first reflective film being set such that a P-polarization component is greater than an S-polarization component in linear polarization components of the laser beam incident on the first reflective film.

Abstract: In an optical pickup apparatus, a major part of an optical path of a laser beam emitted from a first semiconductor laser device and an optical path of a laser beam emitted from a second semiconductor laser device 3 are shared. The first laser beam is transmitted through a quarter wavelength plate and a second reflecting mirror and is reflected by a first reflecting mirror. With this structure, the number of parts of optical systems disposed in the optical pickup apparatus is reduced, an attachment operation of the parts becomes easier, and a time required for adjusting an optical axis is reduced. Thus, an operational efficiency is greatly improved.

Abstract: A first laser source is arranged on a transmitting side of a polarizing beam splitter, while a second laser source is arranged on a reflecting side of the polarizing beam splitter. The splitting surface of the polarizing beam splitter has a film characteristic of substantially transmitting s-polarization component of the laser light having the first wavelength emitted by the first laser source and substantially reflecting s-polarization component of the laser light having the second wavelength emitted by the second laser source. A plate-like beam splitter serves to introduce laser light reflected off of a signal recording medium into an optical detector by directing the laser light away from the optical path in which the laser sources are located. The plate-like beam splitter includes a splitting surface which has a reflectance that is higher than its transmittance.

Abstract: A lighting device, including a first light source emitting light of a first wavelength; a second light source close to the first source, emitting light of a second wavelength in almost a same direction as that of the first source; a third light source located emitting light of a third wavelength in a direction different from that of the first and second sources; a coupling optical system coupling light from the first and second sources; another coupling optical system coupling light from the third source; and a light path synthesizer synthesizing a light path of light from the first, second and third sources, wherein the light path synthesizer includes a first surface reflecting light from the first source and transmitting light from the second and third sources and a second surface unparallel with the first surface, reflecting light from the second source and transmitting light from the third source.

Abstract: An optical pickup apparatus includes a light generating unit to generate a light to record or reproduce information, an objective lens to focus the light generated from the light generating unit onto a disk, and a multi-sectional polarizer disposed on a light path between the light generating unit and the objective lens and divided into a plurality of sectors having their individual optical axes.

Abstract: An optical pickup device has a DVD/CD laser diode for emitting a DVD/CD laser beam as linear polarized light, and a BD laser diode for emitting a BD laser beam. The optical pickup device has a dichroic mirror that regularly reflects a part of the DVD/CD laser beam, transmits a part of the DVD/CD laser beam, and transmits return light of the BD laser beam. The dichroic mirror is formed so that a product of reflectance of outward light of the DVD/CD laser beam and transmittance of return light of the DVD/CD laser beam becomes 20% or more to 25% or less. A light receiving element receives the return light of the DVD/CD laser beam transmitted through the dichroic mirror or the return light of the BD laser beam transmitted through the dichroic mirror.

Abstract: Reference light for interference with signal light from an optical information recording medium is displaced and reflected by a corner cube prism or the like with high accuracy. The signal light and the displaced reference light are made parallel with each other with high accuracy. The signal light and the reference light are each split using a polarization splitter to generate interference light. Thus, regeneration signals are stabilized. Accordingly, an interference-type optical head and optical disc apparatus of higher quality than conventional ones can be provided.

Abstract: In a beam applying method, recording and reproducing operations are performed on an optical recording medium, in which a signal is recorded and reproduced by applying a beam thereto and which has a recording layer on which the signal is recorded, a quarter-wavelength plate formed below the recording layer, a polarizing plate formed further below the quarter-wavelength plate, and a reflecting film formed below the quarter-wavelength plate. The beam applying method includes the steps of; emitting a beam to be applied to the optical recording medium; and driving a quarter-wavelength plate inserted into an optical system serving to guide the emitted beam to the optical recording medium so that the optical axis direction thereof has a predetermined angle difference at the time of performing a recording operation and reproduction.

Abstract: An optical system for efficiently extracting plural signal beams from a bundle of rays reflected from a multilayer optical disc.

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: An optical rotating plate has an optical rotating material layer. A phase plate is provided on a first surface side of the optical rotating plate and has at least one birefringent material layer. The first surface side is disposed toward an emitting side of an optical path, thereby giving different phase differences to a first linearly polarized light group containing at least a linearly polarized light having a first wavelength and a second linearly polarized light group containing at least a linearly polarized light having a second wavelength which is different from the first wavelength.

Abstract: An optical pickup device according to the present invention includes: a first light source that outputs a first laser beam; a second light source that outputs a second laser beam; and an optical system that irradiates an information medium with the first and second laser beams. The information medium includes: an information layer on which user data is written; and a recording layer on which visible information, which is directly visible to a user, is recorded. The optical pickup device is characterized by outputting the first laser beam in writing the user data on the information layer but outputting the second laser beam in recording the visible information on the recording layer.

Abstract: Disclosed herein are aspects of optical tape technology, tape manufacturing, and tape usage. Methods and systems of tape technology disclose optical tape media including: configurations, formulations, markings, and structure; optical tape manufacturing methods, systems, and apparatus methods and systems including: curing processes, coating methods, embossing, drums, testing, tracking alignment stamper strip; optical tape methods and systems including: pick up head adapted for the disclosed optical tape; and optical tape uses including optical storage media devices for multimedia applications.

Abstract: A holographic information recording and/or reproducing apparatus including: a light source unit emitting reference light and signal light; a first optical path guiding unit guiding the lights to cross; a second optical path guiding unit including a first polarization converter located on an optical path of one of the reference and signal lights, a first polarization beam splitter located at a crossing point of the reference light and the signal light, an optical path converter guiding the reference light and the signal light so that they cross again, a second polarization converter located on an optical path of the signal light before the signal light crosses the reference light, and a second polarization beam splitter uniting the optical paths of the reference light and the signal light; and an objective lens unit illuminating the reference light and the signal light onto one side of a holographic information storage medium.

Abstract: An object of the present invention is to provide an extraction optical system capable of separating and extracting a signal light and a stray light with a simple configuration, and an optical head device including the same. A phase plate and a phase plate are +?/4 phase plates, while a phase plate and a phase plate are ??/4 phase plates. A focal line, a focal line and a focal line represent a focal line of a stray light, a focal line of a reproduction light and a focal line of a stray light, respectively. All beams of the reproduction light enter the state in which a polarization direction is rotated by 90 degrees after passing through the phase element. In contrast to the all light bundles of the reproduction light, polarization directions of all light bundles of the stray lights and are not rotated even after passing through the phase element.

Abstract: An optical pickup device has a DVD/CD laser diode for emitting a DVD/CD laser beam as linear polarized light, and a BD laser diode for emitting a BD laser beam. The optical pickup device has a dichroic mirror that regularly reflects a part of the DVD/CD laser beam, transmits a part of the DVD/CD laser beam, and transmits return light of the BD laser beam. The dichroic mirror is formed so that a product of reflectance of outward light of the DVD/CD laser beam and transmittance of return light of the DVD/CD laser beam becomes 20% or more to 25% or less. A light receiving element receives the return light of the DVD/CD laser beam transmitted through the dichroic mirror or the return light of the BD laser beam transmitted through the dichroic mirror.

Abstract: It is possible to provide a new information recording/reproduction method and a device which can realize a small-size large-capacity memory having a characteristic equivalent to or higher than a hologram memory. The optical information recording/reproduction device includes: recording light generator (51) which generates a recording light (55) in a polarization state having two mutually orthogonal polarization components with a phase difference at an arbitrary polarization base; reproduction light generator (61) which generates a reproduction light (65) in a polarization state having only a single polarization component at a arbitrary polarization basis; recording medium (71) in which optical information is recorded by recording light (55) and the recorded optical information is reproduced by reproduction light; and optical information detector (polarimeter 81) which retrieves information light (72) after being applied to recording medium (71) and detects the light as optical information.

Abstract: A laminated wave plate of the present invention includes a first wave plate having a phase difference of ?1 and a second wave plate having a phase difference of ?2 with respect to a wavelength ?, the first wave plate and the second wave plate being bonded together so that an optical axis of the first wave plate and an optical axis of the second wave plate intersect each other to function as a quarter-wave plate as a whole, the laminated wave plate comprising following equations from (1) to (6): ?1=360×(n1+1) . . . (1); ?2=90×(2×n2+1 . . . (2); ??1=(?12a??11a)/(?12??11) . . . (3); ??2=(?12b??11b)/(?12??11) . . . (4); cos 2?1=1?(1?cos ??2)/{2×(1?cos ??1)}. . . (5); and ?2=45°±5°. . . (6), wherein ?1 is an optic axis orientation of the first wave plate, ?2 is an optic axis orientation of the second wave plate, and each of ?11????12, n1, and n2 is a natural number starting from 1.

Abstract: A laser converging apparatus comprising: a nonpolarizing hologram element having a first area defined by a numerical aperture corresponding to a thickness of a first protective layer of a first disk medium and a second area inside the first area, the second area defined by a numerical aperture corresponding to a thickness of a second protective layer (>the thickness of the first protective layer) of a second disk medium, the second area having a hologram pattern for diffracting laser light into zero order light and high-order diffracted light having the order of primary or higher; an objective lens having the numerical aperture corresponding to the thickness of the first protective layer, the objective lens converging the laser light having passed through a part of the first area other than the second area and the zero order light having passed through the second area onto an information surface on one side of the first protective layer, the objective lens converging the high-order diffracted light having

Abstract: An optical disc apparatus includes a laser diode, a first optical component which branches beams from the laser diode into a first beam and a second beam, an objective lens which focuses the first beam on an optical information recording medium, an actuator which drives the objective lens in an optical axis direction, a reference mirror provided in an optical path of the second beam, an optical path length varying unit which varies an optical path length of the second beam, a first photo detector, a second photo detector, a second optical component which branches beams obtained by combining the first beam which is reflected by the optical information recording medium and the second beam which is reflected by the reference mirror and which makes the branched beams incident on the first and second photo detectors, and a signal processing part.

Abstract: An optical pick-up apparatus including an optical source module having a CD optical source and a DVD optical source, a diffracting grating dividing a light beam from the optical source module to at least three divided light beams, a first optical divider changing a path of the divided light beams to an optical disk, a second optical divider reflecting and forwarding the divided light beams reflected from the optical disk in a predetermined ratio, a first optical detector including a single optical sensor receiving reflected light from the second optical divider, and a second optical detector including at least three optical detection sensors receiving forwarded light from the second optical divider. Embodiments of the present invention can provide support for multi-type optical disks with a simple optical structure.

Abstract: A polarization detection system structured for optical read-out of disc-shaped optical data/information storage and retrieval media with surfaces comprised of pits or marks configured as multilevel oriented nano-structures (ONS) with varying pit or mark orientations and widths. The polarization detection system comprises: an optical beam source; a stage for mounting and rotating an optical disc medium about a central axis; at least one photodetector; a beam splitter positioned in an optical path between the source and stage, for directing an incident beam from the source onto an optical disc mounted on the stage and a return beam from the disc onto the photodetector; and an optical polarizer positioned in an optical path between the beam splitter and the at least one photodetector, for detection and analysis of changes in polarization of the return beam effected by variation of the orientation of the walls and/or widths of the pits or marks of the disc.

Abstract: The present invention provides an optical pickup apparatus to for recording and/or reproducing information on an optical information recording medium including multilayered information recording surfaces. The optical pickup apparatus includes: a light source; an objective lens; a first optical element including a first optical area and a second optical area; a second optical element including a third optical area and a fourth optical area. The optical pickup apparatus further includes a light-converging element for receiving a main light flux from one information recording surface and a secondary light flux from another information recording surface and converging the main light flux at a position between the first optical element and the second optical element. The optical pickup apparatus further includes a polarization splitting optical member for splitting the main light flux and the secondary light flux; and a photodetector for receiving the main light flux.

Abstract: An optical pickup apparatus includes: a first light source for emitting a first light flux; a light-converging optical system including an objective lens and a diffractive structure. When the first light flux from an optical information recording medium enters into the diffractive structure, the diffractive structure emits a main light flux and a secondary light flux. The optical pickup apparatus further includes: a first optical element including a first optical area and a second optical area; a second optical element including a third optical area and a fourth optical area; a light-converging element for converging the main light flux at a position between the first optical element and second optical element; a polarization splitting optical member for splitting the main light flux and the secondary light flux each emitted from the first optical element and second optical element; and a photodetector for receiving the main light flux.

Abstract: An optical pick-up including a fold mirror having an achromatic quarter-wave plate coating is provided. To allow the thin film coating to efficiently provide the quarter-wave retardation, the optical pick-up is configured such that the polarization of light incident on the fold mirror is at a predetermined angle. According to one embodiment, the predetermined angle is provided by rotating the light sources. According to another embodiment, the predetermined angle is provided by rotating a plane containing the light sources and the beam combiners. In each embodiment, the beam combiners and the fold mirror are arranged along the same axis to further improve efficiency.

Abstract: The present invention discloses an optical system for extracting signal light components from a beam including the signal light components and stray light components. The optical system includes a condensing optical element situated on an optical path of the beam for condensing the beam, a polarization changing unit for changing the state of polarization of at least one of the signal light components and the stray light components included in the incident beam transmitted through the condensing optical element, and an extracting element for extracting the signal light components included in the beam transmitted through the polarization changing unit.

Abstract: The present invention provides an optical recording method and an optical recording apparatus for holographically recording information allowing for reductions in uneven consumption of the material through the thickness of a recording layer during recording to achieve high density recording and an increased recording capacity, an optical recording medium, and an optical reproducing method and an optical reproducing apparatus using the optical recording method. The optical recording method includes irradiating the optical recording medium with an information beam and a reference beam, dividing at least one of the information beam and the reference beam into two or more between a light source thereof and an optical recording medium, and adjusting the optical path lengths of the divided information beams and reference beams so that they focus on points different from each other through the thickness of the recording layer.

Abstract: Light emitted from a light source and having a wavelength of 400 nm is reflected by a beam splitter (BS), and converged on a disk according to a next-generation standard. Reflection light therefrom passes through the BS and is received by a photodetector. Light emitted from a light source and having a wavelength of 660 nm is reflected by the BS and passes through the BS, and converged on a disk according to a DVD standard. Reflection light therefrom passes through the BS and is received by the photodetector. About 50% of light emitted from a light source and having a wavelength of 780 nm is reflected by the BS. The light passes through the BS and is then converged on a disk according to a CD standard. Reflection light therefrom passes through the BS. About 50% of the light passes through the BS and is received by the photodetector. Thus, recording and reproduction can be performed on any of disks according to a next-generation standard, DVD standard, and CD standard.

Abstract: An optical integrated unit of the present invention includes: a semiconductor laser that is a light source; at least one light receiving element; a light dividing section which divides outgoing light from the semiconductor laser and returning light from an optical disc, and reflects the returning light so as to guide it to the light receiving element; and a support substrate, and a second support substrate is concave, the light dividing section includes at least three prisms, the prisms on both sides of the light dividing section are respectively adhered to two protrusions of the concave second support substrate, and the light receiving element is adhered to the light dividing section via a cover glass. With this, it is possible to solve a problem of a conventional technology, that is, such a problem that the light receiving element cannot be adjusted highly accurately because of the thickness errors of the support substrate and the relay substrate.

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: In multilayer optical discs and high-speed optical discs, the amount of reproduction light per unit time greatly decreases and the reproduction signal quality (S/N) significantly drops due to the low effective reflectivity and the short read time of the medium. These problems are solved by causing reflected signal light from the optical disc and reference light, which is separated from the same light source and introduced into a detector without being shone onto the optical disc, to interference with each other on the detector. Detector outputs having four different interference states are simultaneously obtained, the interference states being displaced at intervals of 90° in terms of the phase relationship between the reference light and the signal. Based on a operation of the four detector outputs, a reproduction signal can be obtained that is stable at all times and amplified with high quality, even when there is an optical path length variation due to disc undulations.

Abstract: A laser converging apparatus is disclosed that comprises a polarizing hologram element having a first area defined by a numerical aperture corresponding to a thickness of a first protective layer of a first disk medium and a second area inside the first area, the second area defined by a numerical aperture corresponding to a thickness of a second protective layer (> the thickness of the first protective layer) of a second disk medium, the second area having a hologram pattern for transmitting first laser light linearly polarized in a first direction without diffracting the first laser light while diffracting and transmitting second laser light that is linearly polarized in a second direction crossing the first direction at right angles, the second laser light having the same wavelength as the first laser light; an objective lens having the numerical aperture corresponding to the thickness of the first protective layer, the objective lens converging the first laser light having passed through the first area

Abstract: A polarizing diffraction element having a wavelength selectivity which functions as a polarizing diffraction element at a wavelength ?1, and which does not function as a diffraction grating not depending on incident polarization state and shows high transmittance at a wavelength ?2, and an optical head device employing the element, are provided. The polarizing diffraction element selectively diffracts or transmits incident light having two different wavelengths each containing a first circularly polarized light and a second circularly polarized light having a rotation opposite from the rotation of the first circularly polarized light, depending on wavelength and polarization state of the incident light. Then, a reflective wavelength region for at least the first circularly incident light, does not contain said two incident wavelengths.

Abstract: An optical information reproducing apparatus and an optical information reproducing method using the same are provided. The optical information reproducing apparatus includes: a light source; a beam splitter which splits a beam emitted from the light source into a reference beam and a temporary beam; a temporary beam splitter which splits the temporary beam into a pair of assistant beams; an incident optical system which inputs the reference beam and the assistant beams to a recording medium in which optical information is recorded; a reproduction beam detector which detects reproduction beams reproduced in response to the reference beam, sets the position of the reproduction beam having the largest light intensity as a reference position, and sets a signal region on the basis of the reference beam; and an assistant beam detector which compares the light intensity of the assistant beams incident on the signal region with each other and sets an incident angle of the reference beam.

Abstract: An optical information processing apparatus is provided. The optical information processing apparatus includes: an optical system which irradiates a reference beam on an optical information recording medium having a plurality of recording regions adjacent to each other so that the reference beam is wider than each of the recording regions; a filter which filters readout beams reproduced from the optical information recording medium to pass a selected readout beam reproduced from a selected recording region and separates neighborhood readout beams reproduced from neighborhood of the selected recording regions; a readout beam detector which detects the selected readout beam passing through the filter; a neighborhood readout beam detector which detects the neighborhood readout beams separated by the filter; and a controller which compares the neighborhood readout beams detected by the neighborhood readout beam detector to control a reproduction condition of the selected readout beam.