Abstract: An optical pickup is provided which includes a light source, an optical system for converging a laser beam emitted from the light source, and an optical element having a function of increasing a numerical aperture of the optical system, wherein recording and/or reproducing information on a recording medium is performed by using the laser beam from the light source while the optical element is brought in contact with or in close to the recording medium, and the optical element has a contamination-preventing structure.

Abstract: An objective lens for recording and/or reproducing information of an optical information recording medium, comprises a first lens group having a positive refractive power; and a second lens group having a positive refractive power. The first and second lens groups are arranged in this order from a light source side of the objective lens and are made of a plastic material respectively; and the following formula is satisfied: NA>0.85 where NA is a necessary image side numerical aperture for recording or reproducing information of the optical information recording medium.

Abstract: It is an object of the invention to provide a diffraction element having a simple configuration for detecting light beams of different wavelengths that are irradiated in order to store or reproduce information with respect to different types of optical disks, and an optical pickup head device. The diffraction element includes a first diffraction grating for diffracting a first light beam having a first wavelength &lgr;1 so as to emit a first first-order diffracted light beam, and a second diffraction grating for diffracting a second light beam having a second wavelength &lgr;2, which is different from the first wavelength &lgr;1, so as to emit a second first-order diffracted light beam. The first diffraction grating and the second diffraction grating are arranged so that the first first-order diffracted light beam diffracted by the first diffraction grating and the second first-order diffracted light beam diffracted by the second diffraction grating are focused onto a same photodetector.

Abstract: An optical pickup performing recording, reproduction and deletion of information onto an optical recording medium, said optical pickup includes light sources of blue wavelength zone, red wavelength zone and infrared wavelength zone; a single object lens which condenses a light from any of the light sources; and a single aberration correction device disposed in a common light path between each of the light sources and the object lens.

Abstract: An optical pick-up device for recording/reading an optical recording medium is provided, which can efficiently utilize light emitted from the laser light source. The optical pick-up device includes a light source, an optical system, a quarter-wave plate, a diffraction component, and a photodetector unit. The photodetector unit may further include a transmitting portion for transmitting the light beam emitted from the light source, and may be disposed opposite the light source in a vicinity of the light source so that light emitted from the light source is transmitted through the transmitting portion. The transmitting portion may be an aperture provided in the photodetector unit. Alternatively, the optical pick-up device may further include an optical path separator for separating the diffracted returning light beam from the light beam that passes from the light source to the diffraction component.

Abstract: Disclosed herein is an optical pickup device. The optical pickup device has a lead frame package and a detecting unit. The lead frame package has a lead frame, a two-wavelength light source module and a hologram optical element. The lead frame has an opening formed to communicate with the outside. The two-wavelength light source module is arranged in a portion of the opening for emitting two beams having different wavelengths toward an optical disc. The hologram optical element is arranged over the two-wavelength light source module. Further, the hologram optical element includes a hologram pattern formed in its top and a wavefront-compensation hologram pattern formed on its bottom. The detecting unit has a board arranged beneath the lead frame package to be separated from and moved independently of the lead frame package, and a photo detector mounted on said board.

Abstract: An optical pickup apparatus includes first and second light sources which selectively emit one of first and second light beams, the first and second light beams being different in wavelength, the wavelengths of the first and second light beams being appropriate for accessing first and second optical disks respectively. A coupling lens converts a corresponding one of the first and second light beams into a collimated beam. An objective lens forms a light spot on a corresponding one of the first and second optical disks by focusing the collimated beam. A holographic optical element receives a reflection beam of the light spot from one of the first and second optical disks and provides holographic effects on the reflection beam so as to diffract the reflection beam in predetermined diffracting directions depending on the wavelength of the reflection beam.

Abstract: An objective lens comprises an inner optically functional region an inner optically functional region allowing a light flux to pass through for conducting recording and/or reproducing information for a first and second optical information recording mediums, an outer optically functional region allowing a light flux to pass through for conducting recording and/or reproducing information for the first optical information recording medium; and a diffractive structure provided on the outer optically functional region. The objective lens satisfies the following formulas: &lgr;>700 nm, NA1>0.65 and t1<t2 wherein &lgr; is a wavelength, NA1 is a numerical aperture, t1 and t2 are a thickness of a transparent base board of the first information recording medium and the second information recording medium.

Abstract: The present invention relates to an optical pickup having a constant numerical aperture even if spherical aberration is compensated for. The optical pickup is used in an information recording and/or reproducing machine. The information recording and/or reproducing machine records and/or reproduces information in a recording medium upon radiation of a light beam from a light source. The optical pickup includes a condensing optical system for condensing the light beam from the light source onto a recording layer of the recording medium. The condensing optical system includes an object lens. The condensing optical system also includes an aperture positioned about a focal length of the object lens apart from a position of a principal incidence plane of the object lens toward the light source along an optical axis of the condensing optical system.

Abstract: An optical pickup device includes an illuminating optical system for focusing light beams, split in a main beam and at least one side beam, onto a track on an information storage surface of an optical storage medium to form optical spots thereon. The device also includes a light detecting optical system for introducing return light reflected back from the information storage surface and a polarizing optical element. The polarizing optical element has regions split at the center of an optical path by a parting line extending at least either in a direction of extension of the track or in a direction perpendicular to the direction of extension. The polarizing optical element also splits the main beam return light at least in two for each of the regions on a plane perpendicular to the optical path of the return light of the reflected main beam in the light detecting optical system. The polarizing optical element is disposed where the return light of the main and side beams is spatially separated.

Abstract: The invention provides a pickup head used in an optical data storage system. The pickup head contains a diffractive optical element (DOE) stack on a semiconductor substrate. The DOE stack includes multiple diffractive lenses for providing several diffractive surfaces and a middle layer serving as a beamsplitter and servo-generating element for a light reflected from an optical storage medium. The middle layer is sandwiched by the diffractive lenses that are located on both outer parts of the DOE stack. The semiconductor substrate includes at least a laser source and several photodetectors. The middle layer serving its function preferably includes a polarization-selective DOE and a quarter-wave retarder oriented to rotate a polarization state of the laser source, so that only the light reflected from the optical storage medium is diffracted by the polarization-selective DOE.

Abstract: An optical pickup head device includes a diffraction grating for generating zero-order diffracted light and at least first-order diffracted light and provides a tracking error signal with a DPP method. The diffraction grating includes grating patterns with a nonuniform period or phase. The size of the first-order diffracted light converged on an optical recording medium is larger in the direction parallel to a tangent to the track than in the direction perpendicular to the tangent. P1/P0>PW2/PW1 is established, where PW1 represents the power that is required to record information on the optical recording medium, PW2 represents the maximum power that allows information recorded on the optical recording medium to be reproduced without being erased, P0 represents the light amount of the zero-order diffracted light converged on the optical recording medium, and P1 represents the light amount of the at least first-order diffracted light converged on the optical recording medium.

Abstract: In the past there has been a problem that on a detection surface the influence of interference causes a defocusing signal to degrade, narrowing the range in which spherical aberration can be stably detected. Accordingly, a diffraction grating is used to focus the inner and outer sides of luminous flux on separate optical detectors before the optical flux is focused on an optical detector and defocusing signals are independently calculated to find the difference therebetween, thereby providing a spherical aberration signal. This makes it possible to detect spherical aberation signals more stably.

Abstract: For each channel in a parallel channel optical array, a diffractive optical arrangement (DOA) includes an input region that is configured to pass a first portion of an input beam to an output region for data transmissions and to diffract and direct a second portion to a detection region for monitoring. The input region includes the diffractive features of a computer generated hologram (CGH) or a grating for diffracting. Alternatively, the input region is coupled to the CGH or grating. Moreover, the DOA includes at least one reflective region for redirecting the second portion. In one embodiment, the DOA includes a separate active surface for each channel of the array. Alternatively, the DOA has a singular active surface that is positioned to interact with all the channels. Optical power output from the second portion is monitored to generate feedback signals for adjusting the input current to each laser. Additionally, optical power output from sensed temperature is monitored to generate feedback signals.

Abstract: An optical pickup device includes an irradiating optical system for converging a light beam to form a spot on a recording surface via a light-transmitting layer of an optical recording medium, and a photodetection optical system for converging return light reflected and returned from the spot on a photodetector. The device detects wave aberration and focal error of the light beam. A diffractive optical element is disposed on the optical axis of return light in the photodetection optical system and provided with an annulus. The diffractive optical element annularly extracts, from return light, ray components in the vicinity of a predetermined radius on a pupil on the emitting pupil surface of the irradiating optical system, which is affected by the wave aberration generated in the optical system.

Abstract: An optical disc apparatus and a wobble signal detection method in which a light beam projected onto an optical disc and reflected by the optical disc is divided into at least four light regions in the direction corresponding to the radial direction of the optical disc to detect the light regions, and a wobble signal is detected by performing a subtraction on first and second difference signals, the first difference signal obtained by performing a subtraction on detection signals for the inner light regions of the divided and/or detected light beam and the second difference signal obtained by performing a subtraction on detection signals for the outer light regions of the divided and/or detected light beam.

Abstract: An optical pick-up capable of reproducing information excellently on both CD and DVD, which are significantly different in terms of three kinds of factors, a base material thickness, a wavelength of a light source, and NA, and detecting TE signals by three kinds of methods, that is, the phase difference method, the PP method, and the 3-beam method, which are necessary to record and reproduce information. The optical pick-up is formed by integrating laser light sources having two kinds of wavelengths (&lgr;1, &lgr;2) for detecting TE signals; photodetectors, and hologram for generating the diffracted light for detecting signals.

Abstract: An optical device includes a light-emitting element for irradiating light onto an information recording medium, a diffraction grating for splitting light emitted from said light-emitting element into a plurality of beams, a focussing member for focussing the plurality of beams onto the information recording medium, a deflection member for deflecting the plurality of beams after they have been reflected from the information recording medium; and a photodetector for receiving the plurality of beams after they have been deflected by the deflection member. The diffraction grating has a first grating region and a second grating region, which have different diffraction efficiencies. The zero-order diffraction light in the first grating region is used as the main beam for reproducing the information signal, and the +1-order or −1-order diffraction light in the second grating regions is used as sub-beams for reproduction of the tracking error signal.

Abstract: An optical pickup head is provided with a light source, a diffracting means for creating a plurality of diffracted beams, a converging means for focusing the diffracted beams onto an optical storage medium, a beam branching means for branching the plurality of beams reflected by the optical storage medium, and an optical detecting means for outputting a signal corresponding to the amount of light of the received beams. The optical detecting means has main beam light receiving portions and sub-beam light receiving portions. The amount of light of the first or higher order diffracted beams when they are substantially focused on and reflected by a focus plane of the plurality of information recording planes is equal to or greater than the amount of light of the zero order diffracted beam when it is reflected without focusing by a non-focus plane other then the focus plane of the plurality of information recording planes.

Abstract: A hologram 48 as optical path branching element has two hologram areas 48b and 48c for diffracting a return light beam into different directions, and a boundary 48a between them is inclined at a predetermined angle with respect to the direction corresponding to the direction of radius of the optical disc 11. The light diffracted by the one hologram area 48b is received by light-receiving sections A1 and A2 of a photodetector IC 44, and the light diffracted by the other hologram area 48c is received by light-receiving sections A3 and A4. With the above-described structure, a position deviation of an objective lens 27 at the time of access to a desired recording track on an optical disc 11 can be detected by finding the difference between the light quantity of the light received by the light-receiving sections A1 and A2 of the photodetector IC 44 and the light quantity of the light received by the light-receiving sections A3 and A4.

Abstract: A light guide path element is provided with: a first light guide path for guiding a light beam having a first wavelength; a second light guide path for guiding a light beam having a second wavelength; a first separating device for irradiating the light beam having the first wavelength irradiated from a first light source onto an information record medium and transmitting a light beam reflected therefrom; a second separating device for irradiating the light beam having the second wavelength irradiated from a second light source onto an information record medium and transmitting a light beam reflected therefrom; a first grating for input-coupling one portion of the light beam transmitted through the first separating device to the first light guide path and transmitting another portion of the light beam transmitted through the first separating device; a second grating for input-coupling one portion of the light beam transmitted through the second separating device to the second light guide path and transmitting

Abstract: An optical apparatus can eliminate offset resulting from assembling errors and also can correct offset even in the photodetector of any optical system. An optical disk apparatus for reading information from tracks traces the track with the condensed spot of light beam depending on the tracking error signal obtained from the optical system for tracking error detection. The tracking error detecting optical system includes an optical apparatus having a photodetector for outputting, as the tracking error signal, a differential value of outputs of a plurality of light receiving sections for receiving the light beam condensed by the condenser lens. Also, an optical element is provided for relatively increasing and/or decreasing the amount of receiving light of a light receiving section depending on displacement of the optical axis of the light beam, in order to balance the light received by the light receiving sections and compensate for affect.

Abstract: An optical pickup apparatus includes a first light source to emit a first light beam having a predetermined wavelength, a first optical path changer to change a proceeding path of the first light beam, an objective lens to focus the first light beam on a recording medium, a diffraction member to divide the first light beam reflected by the recording medium into five light regions, the diffraction member having a first diffraction region having a wide width in a direction corresponding to a tangential direction of the recording medium and second through fifth diffraction regions sequentially arranged around the outside of the first diffraction region in a direction corresponding to a radial direction of the recording medium, and a first photodetector having first through fifth light receiving portions to receive the first light beam reflected by the recording medium.

Abstract: An apparatus for recording and replaying information on optical information record medium comprises: a light source for radiating a light beam to an information-bearing layer of the optical information record medium; a hologram device for splitting reflected light from the optical information record medium, the hologram device comprising a central region formed at the central area thereof and a hologram grating surface region arranged at the outer periphery of the central region; a photoreceptor device for receiving split light beams from the hologram device, the photoreceptor device comprising a first multiple-part split photoreceptor element for receiving light beams from the central region and two second multiple-part split photoreceptor elements for receiving light beams from the hologram grating surface region, means for generating a tracking error signal from signals from the first multiple-part split photoreceptor element; means for generating a focus error signal from signals from the two second multi

Abstract: In an optical head device and an optical information recording/reproducing device using the optical head device, by driving a liquid crystal panel 4a, the liquid crystal panel 4a produces wave aberration for light on a going path and light on a returning path likewise. Accordingly, when the substrate-thickness deviation or tilt of the disc 7 is corrected, the wave aberration due to the substrate-thickness deviation or tilt of the disc 7 and the wave aberration produced by the liquid crystal panel 4a are canceled by each other for both of the light on the going path and the light on the returning path, so that no wave aberration remains for the light on the returning path and the phase distribution is not varied.

Abstract: An optical pickup comprises a light source, a three-way split light diffracting section for dividing light emitted from a light source into one main beam and two subbeams, a hologram for dividing each of the main beam and the subbeams reflected from a recording medium into two predetermined directions, and a light receiving section for receiving the beams divided by the hologram. The hologram includes two regions having a small-pitch grating for diffracting each beam to a predetermined direction, the small-pitch gratings have substantially the same pitch and are symmetrical about a split line separating the two regions.

Abstract: An optical pickup device includes a photodetector divided into four light-receiving elements by two dividing lines, an incident optical system for irradiating a light beam onto an optical recording medium, and a receiving optical system for guiding a return light from the optical recording medium to the photodetector, wherein the receiving optical system includes astigmatism generating means for generating astigmatism having an astigmatism axis at an angle of 45 degree with respect to the two dividing lines.

Abstract: An optical pickup device is equipped with a first light source that emits first light, a second light source that emits second light having a wavelength different from a wavelength of the first light, and a diffraction element that deflects the first light or the second light to match optical axes of the lights. The diffraction element is a step-like diffraction element in which one of an incident face and an emitting face thereof has a step-like grating face. A step difference of the step-like grating face is set to have a measurement that generates a phase difference of one wavelength of one of the first light and the second light, and the number of steps of the step-like grating face is set to maximize a (+) first order diffraction efficiency or a (−) first order diffraction efficiency for the other light.

Abstract: An optical pickup is provided for a recording medium, including: a light source generating and emitting a light beam; a light beam division and detection unit dividing a particular light beam portion of the light beam after being reflected/diffracted from the recording medium into sub-divided light beams portions, and detecting the sub-divided light beam portions; and a spherical aberration detection circuit processing the sub-divided light beam portions to detect spherical aberration caused by thickness variation of the recording medium.

Abstract: A transmission diffraction grating body including a base material being substantially transparent with respect to wavelength &lgr;1 and having a refractive index n0; another base material being substantially transparent with respect to wavelength &lgr;1 and having a refractive index n1, which is formed on the base material having a refractive index n0; and a relief diffraction grating formed on the base material having a refractive index n1; wherein the refractive indexes n1 and n0 satisfy the relationship: n1>n0. Thus, the base material having a refractive index n1 can be formed of a high refractive index material, and when the depth of grating of the diffraction grating is set so that the diffraction grating diffracts the light with wavelength &lgr;1 and does not diffract the light with wavelength &lgr;2, the depth of grating of the diffraction grating can be made to be shallow, thus preventing the loss of the amount of the light with wavelength &lgr;1.

Abstract: In an optical head for use in an optical data recording/reproducing apparatus of the present invention, light issuing from a semiconductor layer is split into a main beam that is a zeroth order light and subbeams that are positive and negative first-order diffracted light. A focus error signal is detected from each of the main beam and subbeams. A diffraction optical element causes the main beam and subbeams to differ in light intensity distribution from each other when incident to an object lens. As a result, when a disk or optical recording medium has a thickness error, the focus error signal derived from the main beam and focus error signals derived from the subbeams differ in zero-crossing point from each other. The thickness error is detected on the basis of the difference between the zero-crossing points.

Abstract: An optical apparatus can eliminate offset resulting from assembling errors and also can correct offset even in the photodetector of any optical system. An optical disk apparatus for reading information from tracks traces the track with the condensed spot of light beam depending on the tracking error signal obtained from the optical system for tracking error detection. The tracking error detecting optical system includes an optical apparatus having a photodetector for outputting, as the tracking error signal, a differential value of outputs of a plurality of light receiving sections for receiving the light beam condensed by the condenser lens. Also, an optical element is provided for relatively increasing and/or decreasing the amount of receiving light of a light receiving section depending on displacement of the optical axis of the light beam, in order to balance the light received by the light receiving sections and compensate for affect.

Abstract: In a photodetector, the minimum size of the photodetection area for detecting a focus error signal from a light beam on the inner radius side of a hologram is made smaller than the minimum diameter of diffracted light beam spots (30, 31) for recording and reproduction, and when a CD is reproduced, a light beam close to the optical axis is made to significantly contribute to the focus error signal and the minimum size of the photodetection area for detecting the focus error signal from a light beam from the peripheral side of the hologram is made larger than the minimum diameter of diffracted light beam spots (130, 131) for recording and reproduction, whereby the focus error signal is made equal to the normal focus error signal when a DVD is reproduced, so that the focus offset variation caused when the base material thickness varies can be reduced.

Abstract: The semiconductor laser device includes a signal light diffraction grating, and a light receiving portion having a pair of photodiodes extending as two strips with a parting portion or a zonal gap interposed therebetween and receiving a focus error detecting beam from the signal light diffraction grating. The light receiving portion is arranged such that its longitudinal direction is orthogonal to the direction of diffraction grooves of the signal light diffraction grating. The pair of photodiodes is arranged such that a spot of the focus error detecting beam moves, due to temperature changes, in a range essentially limited to the parting portion therebetween. Thus, a semiconductor laser device and an optical pickup apparatus suppressing focus errors due to temperature changes and preventing reduction in signal strength can be obtained.

Abstract: An optical assembly suitable for use with an optical medium for the storage and retrieval of data, the optical assembly comprising: a source of illumination for providing a beam of optical radiation, an objective lens disposed in the optical path of the beam for redirecting the beam to the optical medium, and a diffractive optical element disposed between the redirected beam of radiation and the optical medium such that at least a portion of the redirected beam of radiation passes through a surface of the diffractive optical element and is reflected to the objective lens.

Abstract: A hologram laser unit to be used for performing recording and reproducing operations of information for an optical disk, includes a light source, a photodetector, and a hologram element which are formed integrally with each other. The hologram element includes: a first hologram for detecting information signals from the optical disk, the first hologram being provided in an area having an effective diameter corresponding to a numerical aperture suitable for the optical disk; and a second hologram for compensating for only a transmitted light amount of light traveling toward the optical disk from the light source, the second hologram being provided contiguously outside the first hologram.

Abstract: Light from a light source is applied to a diffraction grating via a collimator lens. The light diffracted by the diffraction grating is applied to a polarization beam splitter. The light polarized by the polarization beam splitter at a given polarizing plane is transmitted and is applied to a recording surface of an optical disc via a ¼-wave plate and an objective lens. The light reflected from the recording surface of the optical disc is applied to the polarization beam splitter via the objective lens and the ¼-wave plate and is reflected by the polarization beam splitter toward a focusing lens. The light incident to the focusing lens is thereby condensed and is applied to a holographic element which diffracts the light and disposes the focal points of the ±1 diffraction orders to be offset from each other along the optical axis of the zeroth diffraction order with the focal point of the zeroth diffraction order being between the focal points of the ±1 diffraction orders.

Abstract: The present invention discloses a multiple-beam holographic optical pick-up head, which has the advantages of the multiple-beam optical pick-up head and the holographic optical pick-up head and can increase the light usage efficiency. This invention uses the property that a polarized diffractive optical element can generate different optical effects for laser beam with different polarizations and places a polarized multiple-beam grating and polarized hologram on the optical path for splitting the incident light toward the disc into multiple reading beams by the multiple-beam grating. The returning laser beams reflected from the disc are diffracted and diverted by the hologram to reach a photodetector. Both the incident and reflective beams are diffracted once only; thus the light usage efficiency can be increased.

Abstract: The invention provides a pickup head used in an optical data storage system. The pickup head contains a diffractive optical element (DOE) stack on a semiconductor substrate. The DOE stack includes multiple diffractive lenses for providing several diffractive surfaces and a middle layer serving as a beamsplitter and servo-generating element for a light reflected from an optical storage medium. The middle layer is sandwiched by the diffractive lenses that are located on both outer parts of the DOE stack. The semiconductor substrate includes at least a laser source and several photodetectors. The middle layer's function preferably includes a polarization-selective DOE and a quarter-wave retarder oriented to rotate a polarization state of the laser source, so that only the light reflected from the optical storage medium is diffracted by the polarization-selective DOE.

Abstract: In an optical pickup apparatus of the present invention, either a first laser diode emits a laser beam having a first wavelength or a second laser diode emits a laser beam having a second wavelength. An optical system focuses one of the two laser beams onto a recording surface of an optical recording medium. A photodetector unit receives reflection beams, which are reflected from the recording medium, to generate detection signals from the received reflection beams. A holographic unit has a first hologram suited to the first laser diode and a second hologram suited to the second laser diode, the first hologram provided to diffract a reflection beam of the laser beam of the first laser diode to the photodetector unit, and the second hologram provided to diffract a reflection beam of the laser beam of the second laser diode to the photodetector unit.

Abstract: An optical pickup apparatus for reading/reproducing data on an optical recording medium, includes a plurality of laser diodes configured to emit laser light of different wavelengths respectively, a photodetection device configured to detect each laser light, a diffraction type-optical device configured to transmit each laser light from the plurality of laser diodes to the optical recording medium, and to diffract the light reflected from the optical recording medium to the photodetection device, and wherein the diffraction type-optical device includes a plurality of reflecting type-diffraction elements configured to reflect and diffract each laser light of a corresponding wavelength in the laser light from the plurality of light diodes, to the photodetection device so that the photodetection device can detect each laser light of the corresponding wavelength for monitoring each of the laser light, and a suppression setting device configured to set each of the plurality of reflecting type-diffraction elements t

Abstract: An optical pickup apparatus includes a light source and a light detector provided on a stem for detecting source emitted light reflected by an optical recording medium; and a light separating device, having first and second areas, for separating light incident thereon into a plurality of light components respectively directed in prescribed directions. The light detector includes a light receiver, divided into first and second light receiving regions for receiving the light components detected by those first and second areas. The first and second light receiving regions are located in a predetermined orientation determined in part by a light emitting point of the light source and a focal point on the light detector. The stem material and the wavelength emitted by the light source are selected to limit movement of that focal point in that orientation in response to temperature change of the apparatus.

Abstract: In a photodetector, the minimum size of the photodetection area for detecting a focus error signal from a light beam on the inner radius side of a hologram is made smaller than the minimum diameter of diffracted light beam spots (30, 31) for recording and reproduction, and when a CD is reproduced, a light beam close to the optical axis is made to significantly contribute to the focus error signal and the minimum size of the photodetection area for detecting the focus error signal from a light beam from the peripheral side of the hologram is made larger than the minimum diameter of diffracted light beam spots (130, 131) for recording and reproduction, whereby the focus error signal is made equal to the normal focus error signal when a DVD is reproduced, so that the focus offset variation caused when the base material thickness varies can be reduced.

Abstract: An optical device and an information recording and reproducing device, which comprise a radiation source, a transparent substrate, a waveguide layer provided on the surface of the transparent substrate opposite to the radiation source and an optical coupling means that is provided on the surface of the waveguide layer or on the interface between the transparent substrate and the waveguide layer and that has a concentric circular periodic structure with an optical axis of the radiation source in the center; wherein the waveguide layer has a cutoff part at the center of the periodic structure; the light from the radiation source excites a guided light that propagates from the periphery to the center of the periodic structure in the waveguide layer by the optical coupling means; and a part of the guided light leaks out, at the cutoff part, to a signal surface on a flat substrate provided adjacent to the waveguide layer.

Abstract: A six-segment holographic surface is divided into regions by dividing lines. A four-segment photodetection part is divided into four photodetection parts equal in area by a section line substantially parallel to the radial direction of an optical disk and a section line orthogonal thereto. A main light beam diffracted in the regions of the six-segment holographic surface are condensed as spots at positions apart from each other on opposite sides on a section line of the four photodetection parts, and the main beam diffracted in the regions is condensed as spots in the center of the photodetection parts of the four-segment photodetection part.

Abstract: An optical pickup device is adapted to read information signals from optical recording media of two different types such as a “DVD” and a “CD” for which two light beams with different wavelengths are used and comprises a photodetector having a single light receiving section that can be shared by optical recording media of two different types. Both the light beam reflected from the signal recording surface of the “DVD” 106a and the light beam reflected from the signal recording surface of the “CD” 106b are diffracted by the diffraction element 6 and focussed to a same spot on the light receiving surface of the photodiode of a photodetector 7.

Abstract: An optical head having a phase-shifting diffraction grating includes a diffraction grating for dividing the light from a light source into a plus first order diffracted light, a zero order light, and a minus first order diffracted light. An objective lens focuses light from the light source passing through the diffraction grating onto an optical recording medium, and a photodetector receives a reflected light from the optical recording medium. A signal processing circuit generates a track error signal according to an output of the photodetector. The phase difference between lights on different regions of the diffraction grating is &pgr;/2 radians allowing the optical head to detect a land/groove position on an optical recording medium even if the land and groove have identical widths.

Abstract: The optical head is arranged such that a semiconductor laser and a photodetector are formed via a buffer layer on the same substrate; and an opening portion is formed in the substrate under the semiconductor laser and the photodetector. This optical head is further arranged by that the opening portion is filled with a first transparent layer; a diffraction grating is formed on a lower surface of the first transparent layer; a second transparent layer is stacked on a lower surface of the first transparent layer; and a condenser lens is formed on a lower surface of the transparent layer.

Abstract: An optical scanning device is described which can scan a record carrier by a radiation beam. A dividing element directs radiation reflected from the record carrier to a detection system. The detection system includes at least three detectors. The dividing element has at least three gratings, each forming a sub-beam directed to one of the detectors. The longest dimension of each detector is substantially perpendicular to the bisector of the appertaining sector.

Abstract: A focus detection system for use in a multi-beam optical pickup assembly is provided that uses an optical element, either a holographic element or diffractive element, to split beams reflected off of a data-bearing surface of an optical disk into a plurality of data beams and a plurality of focus beams. The optical element also introduces astigmatism into the focus beams. The focus beams are projected onto focus detectors configured to account for overlap between adjacent focus beams to produce an accurate focus error signal.