Abstract: Providing an objective lens with a large numerical aperture (NA), the present invention records or plays conventional optical disks such as CDs and DVDs using an optical head capable of recording or reproducing high-density optical disks. An optical element (8) is provided between a first and second laser light source and an objective lens (18) for the purpose of converting a wave front of a second optical beam 32. Furthermore, the optical element (8) and the objective lens (18) are fixed to move as a single piece.

Abstract: The present invention provides a wavelength-selective diffraction element, configured such that light having a plurality of wavelengths are incident thereon as incident light, which is provided with: a transparent substrate; a concavo-convex part, formed on the transparent substrate such that concave portions and convex portions are cyclically extended in one direction, and comprised of a first material which is optically isotropic; and a filling part, filling at least the concave portions and comprised of a second material which is optically isotropic. The first material and the second material have no absorbance with respect to the wavelengths of the incident light. The first material and the second material have an identical refractive index with respect to light having a first wavelength which is at least one of the wavelengths of the incident light.

Abstract: The present invention makes it possible to use an optical pickup in common with conventional optical disks. In a three-dimensional mark recording layer (111v) of a voluminal medium (100v), information is recorded by forming a three-dimensional record mark (RM) in the vicinity of the focus (Fb) of a blue light beam (Lb) according to the blue light beam (Lb) that is concentrated and has a light intensity equal to or larger than a predetermined intensity. The information is reproduced from the three-dimensional mark recording layer (111v) on the basis of a reproducing blue light beam (Lbr) deriving from irradiation of the blue light beam (Lb). A servo layer (114v) of the voluminal medium (100v) reflects at least part of the red light beam (Lr) which is irradiated in order to square the position of the blue light beam (Lb) in the three-dimensional mark recording layer (111v) with an arbitrary target mark position and whose wavelength is different from that of the blue light beam (Lb).

Abstract: An objective lens, for an optical information read/write device that performs read/write operations on each of a plurality of optical discs using a corresponding one of three laser beams having first, second, and third wavelengths ?1, ?2, and ?3 (nm) satisfying a relationship ?1<?2<?3, respectively, includes a phase shift structure having a plurality of ring-shaped refractive surface zones into which at least one surface of the objective lens is concentrically divided. The objective lens is made of material with an Abbe number ?d satisfying a condition 40??d?80. The phase shift structure has a step between each couple of the adjacent refractive surface zones that gives an optical path difference to an incident laser beam, so that a condition 2N+1.00<|?OPD/?1|<2N+1.30 is satisfied, where ?OPD represents the optical path difference (nm) that the step gives to the laser beam with the first wavelength, and N represents a non-negative integer.

Abstract: An optical pickup device includes: a laser source for emitting, to an optical disk, a laser beam having a wavelength ?1 and a laser beam having a wavelength ?2, which is longer than the wavelength ?1; a light receiver, for receiving laser beams that are reflected by the optical disk; a beam splitter, for directing, to the light receiver, the laser beams reflected by the optical disk; and an astigmatism generation element, located between the beam splitter and the light receiver, for generating the laser beams to be used for focusing control, by designating as the front of the light receiver a focal point on one of the intersecting cross sections that include the light axes of the laser beams, and by designating as the rear of the light receiver, a focal point on the other cross section, wherein the astigmatism generation element is an optical element, which is like a Fresnel lens, whose step depth is substantially a natural number times either the wavelength ?1 or the wavelength ?2.

Abstract: A beam spot position control device, for controlling multiple beam spot positions irradiated onto an optical recording medium so as to be disposed linearly, includes a light detecting unit for detecting the amount of return light for each of a plurality of beam spots disposed linearly, a tracking control unit for performing tracking control based on tracking error signals of at least one of the beam spots detected with the optical detecting unit, and a rotation control unit for rotating the plurality of beam spots which are disposed linearly, based on the DC offset amount of the tracking error signals of at least two of the beam spots detected with the optical detecting unit.

Abstract: An information recording/reproducing device diffracts laser light into main- and sub-beams, irradiates evanescent light in relation to the main beam by an evanescent light generating element to a track where a recording pit provided on a recording surface of a recording medium is formed and evanescent light in relation to the sub-beam to be separated to a track where no recording pit provided on the recording surface of the recording medium is formed. A moving element moves the evanescent light generating element to change a gap with the recording surface. Return light in relation to the sub- and main-beam are received by sub- and main-light receiving elements, respectively. A control element controls the moving element so as to make the gap become a predetermined target value in accordance with a gap error signal containing a signal indicative of an amount of the return light in relation to the received sub-beam.

Abstract: There is provided a diffractive element including a first member 2, which includes a first resin 2a and has a predetermined refractive index, and a second member 3, which has the same refractive index as the first member 2 having the predetermined refractive index in one wavelength of light and has a refractive index different from the first member 2 having the predetermined refractive index in the other wavelength of light. The first member 2 and the second member 3 are alternately arranged within an incidence plane of the two wavelengths of light, thereby constituting a diffraction grating. The second member 3 includes a second resin 3a to dissolve an organic matter 5 having optical absorption in a predetermined wavelength range at a molecular level, whereby the refractive index of the second member 3 is formed.

Abstract: An optical pickup which includes first to third light sources each emitting a light beam each having a first to third wavelength; an objective lens condensing each of the light beams emitted from the light sources on a signal recording face of an optical disc; a collimator lens provided between the light sources and the objective lens to convert a divergent angle of each of the light beams emitted from the light sources so as to obtain a parallel light beam; and a diffractive optical element provided between the collimator lens and the objective lens. The diffractive optical element includes first and second diffractive parts which respectively diffract the light beam having the second wavelength and the third wavelength. The second diffractive part has a diffraction structure formed by a plurality of concentric ring zones, having first to fourth optical faces, each having a different height in an optical axis direction.

Abstract: An optical information recording/reproducing apparatus for an optical disc using a light beam having a wavelength of ? including: an objective lens that converges the light beam onto a recording surface of the optical disc and satisfies a condition: 0.48 < d · ( n - 1 ) f 2 < 0.75 ( 1 ) where f represents a focal length (unit: mm) of the objective lens with respect to the wavelength ?, d represents a thickness (unit: mm) of the objective lens along an optical axis of the objective lens, and n represents a refractive index with respect to the wavelength ?; a photoreceptor to receive the beam reflected from the optical disc; a detector to detect quality of a signal, and an objective lens driving unit to tilt the objective lens in a direction to improve the quality of the signal based on a result of detection by the detector.

Abstract: An information recording and reproducing device diffracts by a diffracting means (14) to make laser light separated into a main beam and a sub-beam, irradiates evanescent light in relation to the main beam, by an evanescent light generating means (21), to a track where a recording pit provided on a recording surface of a recording medium is formed and also irradiates evanescent light in relation to the sub-beam to be separated to a track where no recording pit provided on the recording surface of the recording medium is formed. A moving means (210) moves the evanescent light generating means to a direction to change a gap with the recording surface.

Abstract: An optical pickup module with enhanced aberration correctability is disclosed. This pickup includes more than two different types of laser light sources, an objective lens for collecting and focusing any one of the laser beams leaving the light sources onto an optical disc, and an aberration correction device of the liquid crystal (LC) type, which is disposed between the light sources and the objective lens. The aberration corrector has a surface on which multiple spaced-apart electrodes are patterned for enabling aberration correction relative to incident beams. The corrector controls the potential of a voltage being applied to each electrode in deference to incident beam properties and variations occurrable thereto, e.g., wavelength, effective beam diameter and relative incidence position offsets, thereby to optimally correct beam aberrations, such as coma aberration or wavefront aberration. An optical information reproduction apparatus using the pickup is also disclosed.

Abstract: The apparatus comprising a pickup for reading data from or writing data to an optical storage medium, wherein the pickup comprises a laser providing a laser beam, an objective lens for focusing the laser beam onto the optical storage medium, a first detector and a beam splitter arranged between the laser and the objective lens for guiding light reflected from the optical storage medium onto the first detector. A selecting means, arranged in front of the beam splitter, with regard to the reflected light from the optical storage medium, is provided for guiding reflected light passing through an outer section of the objective lens onto a second detector. The light guided onto the first detector is utilized for providing a tracking error signal and the light guided onto the second detector is utilized for providing a data signal.

Abstract: Disclosed herein is an optical pickup device. In an embodiment of the present invention, sub beams from which an AC component has been removed are generated using a first diffractive element based upon properties that a beam incident on a disc is reflected with being separated by the track structure of the disc, and beams reflected from adjacent layers are prevented from being diffracted to sub cells for receiving the sub beams using a second diffractive element. In this case, the grating direction of the first diffractive element and the second diffractive element is adjusted, and thus the influence of dead zones generated in a tracking error signal due to the second diffractive element is removed.

Abstract: An optical scanning device scans optical record carriers, such as three optical record carriers, where each optical record carrier has an information layer having a depth which is different from the information layer depth of other optical record carriers, where d3<d2<d1, and where d1, d2, d3 are the information layer depths of the first, second, and third optical record carriers, respectively. The scanning device includes a radiation source system for producing three radiation beams of different wavelengths for scanning the three record carriers. The scanning device further includes a diffraction structure for introducing three different wavefront modifications into the three radiation beams, respectively. The diffraction structure is arranged to operate at selected diffraction orders m1, m2, m3, for the three radiation beams, respectively.

Abstract: An information storage apparatus uses an optical data element (nano-grating) with features that are smaller than the wavelength of light. The optical data element alters one or more properties of the light such as reflected amplitude, polarization, phase, wavelength, and spatial orientation to encode data in a massively multi-level format.

Abstract: An optical pickup includes a diffraction grating partitioned into three areas, in which the phase of periodic grating groove structure in an area is successively shifted from that in the adjacent area by 90°. In the generation of a differential push-pull signal, an amplification factor K for sub push-pull signals is varied depending on the type of the optical disk. By such composition of the optical pickup, amplitude deterioration of the tracking error signal accompanying displacement of the object lens is reduced.

Abstract: An optical pickup includes a diffraction grating partitioned into three areas, in which the phase of periodic grating groove structure in an area is successively shifted from that in the adjacent area by 90°. In the generation of a differential push-pull signal, an amplification factor K for sub push-pull signals is varied depending on the type of the optical disk. By such composition of the optical pickup, amplitude deterioration of the tracking error signal accompanying displacement of the object lens is reduced.

Abstract: An optical pickup includes a detector, a plurality of light guiding units, and a switching controller. The detector detects, using a plurality of detection areas, a reflected light beam that is emitted from a predetermined light source and is reflected off an optical recording medium. Each of the light guiding units has a specific light guide pattern and inputs a predetermined part of the reflected light beam to a predetermined detection area in accordance with the light guide pattern. The switching controller switches and selects the light guiding unit that acts on the reflected light beam from among the plurality of light guiding units according to a predetermined switching condition.

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

Abstract: Semiconductor lasers emit lights having wavelengths of about 400 nm, 650 nm, and 780 nm, respectively. A transmittance adjustment element is provided in an optical path of the light reflected from a disk. The transmittance adjustment element includes a first optical thin film that changes transmittance of a 650-nm-wavelength light relatively to transmittance of 400-nm- and 780-nm-wavelength lights, and a second optical thin film that changes transmittance of a 780-nm-wavelength light relatively to transmittance of 400-nm- and 650-nm-wavelength lights. The transmittance adjustment element has the function of maintaining constant the intensity of light incident onto a photodetector irrespective of the type of medium.

Abstract: In the optical pickup device, while reflection light reflected from the optical multi-layer disc is divided into a plurality of regions so as to produce a plurality of divided optical beams, the divided optical beams are focused onto different positions on a photodetector, and a focus error signal is detected by employing a plurality of the divided optical beams by utilizing the knife edge method, and further, a tracking error signal is detected by employing a plurality of the divided optical beams. Furthermore, the dividing regions of the optical beam and light receiving parts are arranged in such a manner that stray light derived from other layers of the optical disc is not entered to a servo signal-purpose light receiving part of the photodetector when the divided optical beam is focused onto a target layer of the optical disc.

Abstract: An optical head unit includes, apart from an objective lens toward a light source, an optical device that changes the image height of light incident onto the objective lens, wherein the optical device includes a concave lens and a convex lens. The objective lens is designed so that a coma aberration having a specific polarity occurs if the optical axis of the incident light tilts toward a specific direction. If the disk tilts, the convex lens is moved within the plane perpendicular to the optical axis, to change the image height of the light incident onto the objective lens, to thereby tilt the optical axis of light exiting from the convex lens with respect to the optical axis of light incident onto the concave lens. The objective lens generates a coma aberration having a polarity opposite to the polarity of the coma aberration attributable to the tilt of disk, to thereby cancel the coma aberration attributable to the tilt.

Abstract: An optical drive device generates a fist push-pull signal and a first sum signal based on a light receiving amount in two light receiving areas of which each width in a signal light tangent direction is smaller than a diameter of a spot of signal light, generates a first normalized push-pull signal by normalizing the first push-pull signal by using the first suits signal, and generates a tracking error signal based on the first normalized push-pull signal.

Abstract: Undesired disturbance components leak eventually into various detection signals and reproduction signals as stray optical beams reflected from recording layers other than a reproduction layer overlap with signal beams on a light reception surface of an optical detector and interference occurs between them when an optical disc having multi-layered recording layers is reproduced. A diffraction grating having a specific grating groove pattern is arranged immediately ahead of an optical detector or in a return optical path. Such optical unit averages the disturbance components resulting from interference between a signal beam and a stray beam and can satisfactorily improve influences of leak.

Abstract: An objective lens according to the present invention is an objective lens used for an optical pickup apparatus, and the objective lens includes a superimposed structure on a surface of a lens with a power in which a first optical path difference providing structure changing spherical aberration in under-corrected direction when a wavelength of an incident light flux becomes longer, and a second optical path difference providing structure changing spherical aberration in over-corrected direction when a wavelength of an incident light flux becomes longer are superimposed.

Abstract: A laser emitting device (9) includes a light emitting portion (4) that emits light of a wavelength ?1 (approximately 405 nm), a light emitting portion (5) that emits light of a wavelength ?2 (approximately 650 nm), and a light emitting portion (6) that emits light of a wavelength ?1 (approximately 780 nm). The light emitting position of the light emitting portion (4) and the light emitting position of the light emitting portion (6) are approximately on the same position as seen in the direction of an optical axis of emitted light of the laser emitting device (9). An optical axis adjusting element (18) is provided for adjusting an optical axis of return light of at least one of the wavelengths among return lights of the wavelengths ?1, ?2 and ?3 so that respective return lights emitted by the light emitting portions (4, 5 and 6) of the laser emitting device (9) and reflected by an optical recording medium (16) are received by a common light detector (20).

Abstract: A pickup device includes a diffraction grating 12 for separating a light beam emitted from the light source into at least three light beams. The diffraction grating 12 is divided into four regions by straight lines extending in a direction parallel to a tangential direction of tracks of an optical information recording medium. A periodic structure of a second region 12B has a phase difference of approximately 180 degrees from a periodic structure of a third region 12C, and a periodic structure of a first region 12A has a phase difference of approximately 180 degrees from a periodic structure of a fourth region 12D.

Abstract: A diffraction element for an optical pick-up apparatus is capable of precisely controlling the tracking of the pick-up apparatus. The diffraction element includes a diffraction grating divided into a first, a second, and a third region. The second region is located between the first and third regions. Any one of the first region and the third region is inclined at a predetermined angle ? with respect to the second region.

Abstract: An optical data storage medium comprises an optical medium with multiple data marks. Each data mark is arranged for modifying a portion of an optical reading beam incident thereon. At least one of the data marks is a delocalized data mark comprising a set of multiple diffractive elements collectively arranged for modifying a portion of the optical reading beam incident thereon. A method for recording data on an optical data storage medium comprises forming on or in the optical medium multiple data marks encoding the recorded data, including the at least one delocalized data mark. A method for reading an optical data storage medium comprises: successively illuminating with the optical reading beam the multiple data marks; sensing variations among the respective portions of the optical reading beam modified by the multiple data marks; and decoding from the sensed variations data encoded by the multiple data marks.

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

Abstract: The present invention relates to composite optical elements, and particularly to a composite optical element including a first optical component and a second optical component coupled to the first optical component. The present invention is advantageous in enhancing optical properties. A composite optical element (1) includes a first optical component (10) and a second optical component (20). The first optical component (10) is made of first glass and has a lens surface (12). The second optical component (20) is made of a material different from the first glass, is coupled to the first optical component (10) at a lens surface (22), and has a lens surface (22) at a side opposite to the first coupling surface (21). The lens surface (12) partially has a first uneven region (12a). The lens surface (22) partially has a second uneven region (22a).

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

Abstract: In an optical pickup for irradiating a laser beam emitted from a photoemission element on a disk-like recording medium through an objective lens, there is provided a diffraction element including a first region for splitting the laser beam emitted from the photoemission element into a main beam and a pair of first sub-beams and a second region for splitting the laser into a main beam and a pair of second sub-beams, wherein a following relation hold or approximately hold: (2n?1)×P/2, where D is a distance between a spot center of the first sub-beam and a spot center of the second sub-beam, the spots being formed on a recording surface of the disk-like recording medium spaced in a substantially radial direction of the disk-like recording medium, n is a natural number, and P is a track pitch of the disk-like recording medium.

Abstract: An optical pickup apparatus comprising: a diffraction grating configured to diffract laser light from a laser diode so that signals recorded in first and second optical discs are selectively reproduced, thicknesses of protective layers between surfaces and signal recording surfaces of the first and second optical discs being different from each other; a polarization beam splitter configured to divide laser light from the diffraction grating into first and second laser lights whose light amounts are substantially the same; a first objective lens configured to focus the first laser light onto the signal recording surface of the first optical disc; a second objective lens configured to focus the second laser light onto the signal recording surface of the second optical disc; and a photodetector configured to be applied with return lights of the first and second laser lights reflected from the signal recording surfaces of the first and second optical discs.

Abstract: Light emitted from a radiation light source 1 passes through a diffraction grating 3a and is separated into transmitted light a, +1st order diffracted light b, and ?1st order diffracted light c. The transmitted light a, +1st order diffracted light b, and ?1st order diffracted light c are collected through an objective lens 7 on tracks on the signal plane 8a of an optical disc 8 in a partially overlapped state. Light reflected by the tracks on the signal plane 8a passes through the objective lens 7 and is incident upon light diverging means 13a.

Abstract: In an integrated optical unit of the present invention, a photo detector (12) and a holding member (17) that sustains a semiconductor laser (11) are provided on a polarizing beam splitter (14). This makes it possible to reduce a deviation from a designed value due to tolerance, and adjust a relative positional relationship between the semiconductor laser (11) and the photo detector (12). Therefore, returned light from an optical disk (4) is accurately adjusted with respect to a division line of a photo-detecting device (13). As a result, stable servo-control is realized, and an information signal with fine quality is obtained.

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

Abstract: An optical information reproducing apparatus includes a light-receiving unit that receives a first reproduction light of an information output from a first region of an information recording layer and a second reproduction light of an information output from a second region of the information recording layer, the first region and the second region being formed by dividing the information recording layer with a line segment that intersects a plane of incidence of the reference light and a plane of the information recording layer, and outputs a first reproduction signal that is a reproduction signal of the first region and a second reproduction signal that is a reproduction signal of the second region.

Abstract: Provided is an optical pickup device capable of suppressing an increase in the number of parts and complication of an optical system while a diffraction grating is used as an optical axis correcting element. Three kinds of blue, red, and infrared laser light beams are emitted from laser element provided in the same CAN package. A blue light emitting point (wavelength: 405 nm) and an infrared light emitting point (wavelength: 780 nm) are arranged in a layer forming direction of the laser elements such that an interval (d2) between the light emitting points becomes shorter than an interval (d1) between each of the light emitting points and a red light emitting point. An optical axis of the laser light beam emitted from the red light emitting point (wavelength: 650 nm) is aligned with an optical axis of the laser light beam emitted from the blue or infrared light emitting point by using the diffraction grating.

Abstract: A diffraction element for use in an optical pick-up is capable of calculating a TE signal more stably irrespective of any assembly error in optical elements. The diffraction element of the invention is divided into three areas, a first, a second, and a third area. Each area comprises a diffraction grating with a predetermined period, and the second area is provided between the first area and the third area. The diffraction grating of the first area is substantially parallel to the diffraction grating of the third area, and the diffraction grating of the second area is substantially perpendicular to the diffraction gratings of the first and the third area.

Abstract: An objective lens of this embodiment is used in an optical head in which a distance between a DVD laser and a CD laser is fixed. The objective lens focuses a laser beam emitted from the DVD laser on a DVD by a numerical aperture of 0.60, and focuses a laser beam emitted from the CD laser on a CD by an numerical aperture of 0.47. The wavefront aberration in design for CD is set greater than the wavefront aberration in design for DVD.

Abstract: A diffractive part for an optical scanning device is described. The device is for scanning a first information layer by means of a first radiation beam having a first wavelength and a first polarisation, a second information layer by means of a second radiation beam having a second wavelength and a second polarisation, and a third information layer by means of a third radiation beam having a third wavelength and a third polarisation. The first, second and third wavelengths differ from each other. The device includes a radiation source for supplying the first, second and third radiation beams, an objective lens system for converging the radiation beams on the respective information layer, and a diffractive part arranged in the optical path of the radiation beams.

Abstract: A method for adjusting an aberration is disclosed that adjusts the aberration existing in a light spot by using a control signal generated from a wobbling signal and a reproduction signal, and thereby maintaining an appropriate S/N ratio for both the wobbling signal and the reproduction signal even when astigmatism, spherical aberration, or other aberrations are present. In an optical pickup, by moving a collimator lens along a light path, a spherical aberration is generated on the light emitted from a light source, a reproduction signal (RF signal) is obtained from the light reflected from an optical disk, a wobbling signal is obtained from the light reflected from grooves on the optical disk, and the correction aberration is adjusted based on the RF signal and the wobbling signal.

Abstract: The present invention relates to an appliance for reading from and/or writing to optical recording media 1 having a first laser diode LD1 for producing a first scanning beam AS1 at a first wavelength ?1 and having a second laser diode LD2 for producing a second scanning beam AS2 at a second wavelength ?2, with the scanning beams AS1, AS2 running along a common optical axis 9, scanning an information layer 6 on the recording medium 1 and falling on a single photodetector 8 in order to produce an information signal IS, with a beam combination element being arranged at one point on the optical axis 9. According to the invention, the beam combination element is a diffraction grating 12.

Abstract: A diffraction element for an optical pick-up apparatus is provided that enables more accurate focusing control. The diffraction element for an optical pick-up apparatus is divided into first and second regions, each being formed with a grid pattern in which grids are repeated with a predetermined pitch P. The grid pattern in at least one of the first and second regions is tilted by a predetermined angle with respect to a virtual line VL substantially perpendicular to a division line DL that divides the first and second regions.

Abstract: An optical pickup including a light source, a light focus device, a diffraction element, an optical split element, a ¼ wavelength board, a light reception device and a correction element wherein the correction element is divided into multiple areas in a surface vertical to an optical axis, each area of the multiple areas has a sub-wavelength convexo-concave structure having a pitch equal to or shorter than a wavelength of the outgoing light beam and the sub-wavelength convexo-concave structures of the multiple areas adjacent to each other have groove directions perpendicular to each other, and the filling factors of adjacent areas of the multiple areas are determined to substantially equalize effective refractive indices with regard to the polarization direction of the outgoing beam emitted from the light source and impart a phase difference of ? with regard to a polarization direction perpendicular to the polarization direction of the outgoing beam.

Abstract: A polarizing element usable for two wavelengths in a predetermined wavelength region and having a simple structure. The polarizing element has a two-layer structure in which a grid pattern of a constant period ? having a triangular cross-section is formed on a substrate and a film with a refractive index higher than that of the substrate is deposited on the grid pattern. When first and second wavelengths ?1, ?2 satisfy ?1<?2, ? cos ?0<?1 where ?0 is the angle of incidence on the grid surface.

Abstract: An optical pickup includes a diffraction grating partitioned into three areas, in which the phase of periodic grating groove structure in an area is successively shifted from that in the adjacent area by 90°. In the generation of a differential push-pull signal, an amplification factor K for sub push-pull signals is varied depending on the type of the optical disk. By such composition of the optical pickup, amplitude deterioration of the tracking error signal accompanying displacement of the object lens is reduced.

Abstract: The present invention relates to a phase retardation plate including a thin organic film with a phase retardation function due to birefringence and a fixed substrate bonded to at least one surface of the thin organic film using an adhesive, and to an optical pickup device having the phase retardation plate. In the phase retardation plate and the optical pickup device using the same, a liner thermal expansion coefficient (L1) of the thin organic film, a liner thermal expansion coefficient (L2) of the adhesive and a liner thermal expansion coefficient (L3) of the fixed substrate satisfy a relationship of L1>L2>L3; and the thin organic film retards the phase of incident light with a wavelength in a range of 400 to 800 nm by ?/2 or ?, the thin organic film having a phase retardation value between 0 and ?.