Abstract: A tunable optical device including a substrate, at least one support unit, a flexible frame, an elastic component, a first reflector, and at least one actuator is provided. The support unit is fixed onto the substrate. The flexible frame is connected to the support unit and suspended above the substrate. The elastic component is connected to the flexible frame. A stiffness of the elastic component in the Z-axis is smaller than a stiffness of the flexible frame in the Z-axis. The Z-axis direction is parallel to a normal direction of the substrate. The first reflector is connected to the elastic component. The actuator is located between the flexible frame and the substrate or located between the first reflector and the substrate.

Abstract: An anti-reflection coating having an three-layer structure comprising first to third layers formed in this order on a substrate, the substrate having a refractive index of 1.6-1.9, the first layer having a refractive index of 1.37-1.57, the second layer having a refractive index of 1.75-2.5, and the third layer having a refractive index of 1.18-1.32, to light in a wavelength range of 550 nm; the third layer being formed by silica aerogel; and the first and second layers containing no Al2O3.

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

Abstract: There is provided an optical pickup including a light source, an objective lens configured to focus light from the light source onto one signal face of an optical disc, the optical disc including two or more signal faces, each of the signal faces having a groove formed therein, a photodetector configured to receive returning rays from the optical disc, the photodetector having a light receiving face divided into four light receiving regions by a dividing line that is substantially parallel to a track direction of the optical disc and by a dividing line that is substantially perpendicular to the track direction, and a shading unit disposed at an incident side of the photodetector and configured to block, of returning rays from a signal face other than the one signal face of the optical disc, at least a diffracted ray that is diffracted by the groove.

Abstract: An optical head device includes a light blocking region disposed on a light flux of a reflected light beam resulting from reflection by a recording layer on which a blue light beam is focused, and blocks, when there are at least two recording layers on a blue light beam incident side of the recording layer on which the blue light beam is focused or on a side thereof opposite to the blue light beam incident side, reflected light beams resulting from reflection by the at least two recording layers which are incident on a region in a photodetector where the reflected light beams resulting from the reflection by the at least two recording layers interfere with each other. The light blocking region is not formed on an optical axis of the reflected light beam resulting from the reflection by the recording layer on which the blue light beam is focused.

Abstract: When information is recorded or reproduced on or from an optical information medium having three or more recording layers using blue light, interference by another layer light is reduced and, when information is reproduced from an optical information medium using red light, an S/N ratio is held excellently high.

Abstract: An optical-pickup apparatus includes: a laser diode; an objective lens; a diffraction grating; a photodetector including main-beam-, first-sub-beam-, and second-sub-beam-light-receiving portions; a quarter-wave plate having either a second area allowing a reflected-laser beam to pass therethrough without polarization or a third area allowing the reflected beam to pass therethrough at a polarization angle different from that of the first area; and a polarizing member having a separate-light-amount ratio set therefor with respect to the reflected beams passing through the second or third area and an area excluding the second or third area from the first area, such that proportions of the reflected beams passing therethrough toward the photodetector are different, thereby decreasing an irradiation level when the first- and second-sub-beam-light-receiving portions are irradiated, as stray light, with the reflected beam reflected from either one, not subjected to a signal-reading operation, of the first- and secon

Abstract: An optical pickup device has an astigmatism element which imparts astigmatism to reflected light of laser light reflected on a recording layer, and a spectral element into which the reflected light is entered, and which separates the reflected light. The spectral element is divided into four third areas by a first area having a certain width and formed along a straight line in parallel to a first direction, and by a second area having a certain width and formed along a straight line in parallel to a second direction. The spectral element is configured to guide the reflected light passing through the four third areas to respective corresponding sensors on a photodetector while making propagating directions of the reflected light different from each other, and to avoid guiding the reflected light entered into the first area and into the second area to the sensors.

Abstract: An optical pickup device preventing damage or performance degradation of a second optical system. The optical pickup device includes first laser light source emitting a first light beam having a first wavelength, a first optical system guiding the first light beam emitted from the first laser light source to a first optical disc. Further, the optical pickup device includes a DVD integration unit emitting a second light beam having a second wavelength different from the first wavelength, a second optical system guiding the second light beam emitted from the DVD integration unit to a second optical disc different from the first optical disc, and a filter disposed at a position blocking incident light, of an unwanted light beam having the first wavelength and derived from the first optical system, from entering into the second optical system, so as to block the first light beam having the first wavelength.

Abstract: An optical pickup device has an astigmatism element which imparts astigmatism to reflected light of laser light reflected on a recording layer, and a spectral element into which the reflected light is entered, and which separates the reflected light. The spectral element is divided into six second areas by a straight line in parallel to a first direction, a straight line in parallel to a second direction, and a first area having a predetermined width and formed along a straight line in parallel to a third direction inclined from the first direction by 45 degrees. The spectral element is configured to guide the reflected light passing through the six second areas to corresponding sensors on a photodetector while making propagating directions of the reflected light different from each other, and to avoid guiding the reflected light entered into the first area to the sensors.

Abstract: An optical pick-up is provided. The optical pick-up includes a light source, a first objective lens configured to focus light emitted from the light source on a high-density optical information storage medium, a photo-detector configured to detect a signal by receiving light reflected from the high-density optical information storage medium, an optical-path changer configured to convert a travel path of incident light to allow the light emitted from the light source to proceed toward the high-density optical information storage medium, and to allow the light reflected from the high-density optical information storage medium to proceed toward the photo-detector, and a blocking device disposed in an optical path of signal light reflected from a target reproducing/recording layer of the high-density optical information storage medium, passes through the first objective lens, and proceeds toward the photo-detector.

Abstract: A conventional optical pickup apparatus has a problem that due to multiple optical paths provided therein, the number of parts of optical systems becomes larger and a time required for attaching the parts and adjusting an optical axis becomes longer. In optical pickup apparatus 1 of the invention, a major part of optical path 21 of a laser beam emitted from first semiconductor laser device 2 and optical path 20 of a laser beam emitted from second semiconductor laser device 3 are shared. Then, the laser beam reflected from the optical disk 17 (optical feedback) is received by shared PDIC 19 and light-receiving processing is accurately performed on the laser beam as a light detector. With this structure, the number of parts of optical systems disposed in the optical pickup apparatus 1 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 recording and reproducing device that is capable of improving its reproduction quality by efficiently detecting a reproduction signal having small low frequency noises even when reproducing data on a super-resolution optical disk including recording marks smaller than a diffraction limit.

Abstract: An optical pickup device has an astigmatism element which imparts astigmatism to reflected light of laser light reflected on a recording layer, and a spectral element into which the reflected light is entered, and which separates the reflected light. The spectral element is divided into six second areas by a straight line in parallel to a first direction, a straight line in parallel to a second direction, and a first area having a predetermined width and formed along a straight line in parallel to a third direction inclined from the first direction by 45 degrees. The spectral element is configured to guide the reflected light passing through the six second areas to corresponding sensors on a photodetector while making propagating directions of the reflected light different from each other, and to avoid guiding the reflected light entered into the first area to the sensors.

Abstract: An optical pickup is provided for directing a blue-violet laser beam to access a first information recording medium covered with a first transparent substrate or a second information recording medium covered with a second transparent substrate, which includes a light path switching unit disposed either between a light source and a coupling lens or between the coupling lens and an objective lens for switching the blue-violet laser beam between a first light path and a second light path. The coupling lens is arranged to convert the laser beam reflected on the first or second information recording medium to a converged light. The converged light of the laser beam is then received by a photo detector.

Abstract: The recording and reproducing apparatus has rotary drive unit (a motor) that rotationally drives a multilayer recordable recording medium 1; a reference-light-side recording and reproducing lens 6 and a recording-light-side recording and reproducing lens 7 that are disposed oppositely to the recording medium 1 which is rotationally driven by the rotary drive unit, an address detection lens 5 that is disposed opposite the recording medium 1 and that is provided separately from the recording and reproducing lenses 6 and 7; a light source 9 for recording and reproducing purpose that supplies recording reproduction light to the recording and reproducing lenses 6 and 7; and the address light source 9 that supplies address light to the address detection lens 5. The apparatus is configured in such a way that light whose center axis portion is optically hollow is supplied from the reference-light-side recording and reproducing lens 6 to the recording medium 1 during reproducing operation.

Abstract: An optical pickup device includes: a light source for emitting light in a first wavelength range; an optical element for transmitting the light; a supporting member for supporting the optical element through an adhesive; a first light blocking member for blocking the light emitted from the light source from entering the adhesive when the optical element guides the emitted light to the optical disc; and a second light blocking member for blocking the light reflected from the optical disc from entering the adhesive when the optical element guides the reflected light to the detector unit. In this optical pickup device, at least one of the first and second light blocking member blocks the light in the first wavelength range and transmits light in a second wavelength range.

Abstract: In order to provide a wavelength-selective light-shielding element capable of blocking circularly-polarized light beams rotating in a specific direction among light beams whose wavelengths falling in a specific range, a light-shielding region is provided in a portion of a transparent substrate, wherein the light-shielding region permits passage of first circularly-polarized light rotating in a first direction regardless of a wavelength of the first circularly-polarized light and blocks second circularly-polarized light beams whose wavelengths falling within a predetermined range, among second circularly-polarized light beams rotating in the second direction, to thus permit passage of the second circularly-polarized light beams falling outside the predetermined range.

Abstract: An optical head device includes a first light source and a second light source respectively emitting a first light beam and a second light beam, a luminous flux separating section selectively separating the first and second light beams for which the same optical path is used, to first and second optical paths, respectively, and a first objective lens converging the first light beam that has been separated to the first optical path on the first optical information recording medium. Further, the optical head device includes a second objective lens made of resin and converging the second light beam separated to the second optical path on the second optical information recording medium, and a first filtering section formed on a beam exit face of the second objective lens and reducing the transmittance of the first light beam to be lower than transmittance of the second light beam.

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

Abstract: An 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 to provide a stable operation in both low-speed and high-speed modes by controlling a change in natural frequency, the optical pickup device including: a lens holder to support an objective lens; a supporting unit spaced apart from the lens holder; and a plurality of suspension members each having one end fixed to the lens holder and another end supported by the supporting unit to enable a movement of the lens holder, wherein the supporting unit includes a fixing member, a coupling portion provided in the fixing member to couple each suspension member, magnetic fluid received in the coupling portion, and an excite device to apply a magnetic field to the magnetic fluid.

Abstract: A laminated wave plate that corresponds to a plurality of wavelengths including at least two wavelengths of ?A and ?B, and includes a first wave plate disposed on an incident side and a second wave plate disposed on an emitting side, the first wave plate and the second wave plate being laminated in such a manner that their optical axes are intersected each other, includes the following equations from (1) to (5): ?A1=360°+360°×2NA??(1); ?A2=180°+360°×NA??(2); ?B1=360°×2NB??(3); ?B2=360°×NB??(4); and NB=(?nB/?nA)×(?A/?B)×(0.

Abstract: An optical pickup includes a wave plate on an optical path to be followed by every light beam emitted from three light sources (with wavelengths ?1, ?2 and ?3, respectively) both on their way toward an optical disc and back from the disc toward a photodetector. The wave plate has two layers with different retardations and different optic axis directions. The sum of the retardations of the first and second layers is defined to be approximately 5/4?1, 3/4?2 and 1/2?3 to the light beams with the wavelengths ?1, ?2 and ?3.

Abstract: An objective lens causes birefringence, which causes wave aberration in outgoing light from the objective lens. A coated objective lens has a dielectric multilayer film that can reduce astigmatism component of the wave aberration to 5 m? rms or smaller when 10 m? rms or larger astigmatism component of wave aberration is generated.

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

Abstract: A light blocking unit includes a plate-like member which is different from a housing member, and a light blocking portion formed on the plate-like member, for blocking light. A light detector has a light receiving portion for receiving light which is partitioned into four divided regions, by a Y-axis-wise parting line and an X-axis-wise parting line in X-Y coordinates, and outputs photoelectric output signals for the respective divided regions in accordance with intensity of the light received by the respective divided regions of the light receiving portion. Of light beams emitted from a polarization beam splitter, a part of the light beams are blocked by the light blocking unit while the other part of the light beams are not blocked and thus emitted to the light detector excluding a region defined by two sides parallel to the parting lines.

Abstract: The invention discloses radio frequency zero crossing signal generators for optical disc drives, comprising a controllable low pass filter, a comparator, and a control circuit. The controllable low pass filter evaluates an average level of the magnitude of a radio frequency ripple from an optical disc drive. The comparator compares the radio frequency ripple to the average level evaluated by the controllable low pass filter to generate a radio frequency zero crossing signal. When the optical disc drive reads a fingerprint defect on an optical disc, the control circuit adjusts a cut-off frequency of the controllable low pass filter to adjust the speed at which the controllable low pass filter evaluates the average level.

Abstract: A laminated plate having a wider bandwidth at a desired retardation is provided. A laminated wave plate 1 includes a first wave plate 2 and a second wave plate 3 that are laminated to each other so that respective optical axes of the first wave plate and the second wave plate intersect each other at an angle of 51.5 degrees when the first wave plate has a retardation ?1 of 360 degrees and an in-plane azimuth of ?8 degrees, while the second wave plate has a retardation ?2 and an in-plane azimuth of 43.5 degrees. Thus, the laminated wave plate 1 functions as a desired retardation ?2 in a wavelength from 600 nm to 800 nm as a whole.

Abstract: In an optical beam transmissive adjusting mechanism (110) included in an optical pickup device, arrangement positions of a first transmissive element (111) having a first transmittance and a second transmissive element (112) having a second transmittance higher than the first transmittance are switched by a rotational drive unit (105), and an optical beam having a first optical power and an optical beam having a second optical power are output selectively. Furthermore, since a transmissive element of a non-transmissive side for an optical beam is arranged at an angle inclined to an optical axis of the optical beam, the transmissive element does not obstruct a path of the optical beam to be diffused.

Abstract: An optical pickup apparatus comprising: a collimating lens configured to convert laser light having Gaussian distribution property emitted from a laser diode from divergent light to parallel light; an objective lens configured to focus the laser light from the collimating lens onto a signal recording layer of an optical disc; and an adjustment film formed on a surface of an incident face of the collimating lens on which the laser light is incident, and configured to adjust transmittance of the laser light passing through the collimating lens, the adjustment film being formed on the surface of the incident face so that the transmittance is lower on the inner side of the incident face than on the outer side of the incident face.

Abstract: An optical pickup apparatus aiming at reduction of adverse effect on a tracking control signal and a data signal by preventing the reflected light from the adjacent layers of a multilayer disc changing to a stray light. In this optical pickup apparatus, the reflected light from the optical disc including the stray light from the adjacent layer is once focused with a focusing lens and is then reflected with the reflection plate. A flat attenuation element is provided between the lens and the reflection plate parallel to the optical axis with inclusion of the optical axis under the condition separated from the reflection plate. The reflection plate reflects the reflected light from the relevant layer and the attenuation element shields the reflected light from the adjacent layer. The light returning to the focusing lens includes less influence of the stray light. This light is detected with a detector to become a control signal and a data signal.

Abstract: There is provided an optical head which have no such problems regarding increase in cost and size thereof and can reduce errors by suppressing crosstalk components attributable to reflection on lands of a magneto-optical recording medium and thereby prevent degradation of reproduction characteristics. An optical element includes a light separating section for separating outgoing light and return light, and a phase compensation section for imparting phase compensation to light incident thereon. The optical element is provided on a light path of return light between an objective lens and a photodetector, so as to be closer to the photodetector than the light separating section is. This makes it possible to impart the phase compensation to the return light and prevent the degradation of reproduction characteristics. Light separating elements such as beam splitter are no more necessary in the configuration, with the result that decreases in size and cost can be realized.

Abstract: An optical element for use in an optical pickup apparatus includes a substrate made of resin; an antireflection layer coating the substrate and having a low refractive index layer and a high refractive index layer, wherein the resin includes a polymer with an alicyclic structure, the low refractive index layer is formed of a material selected from the group consisting of silicon oxide; aluminum fluoride; yttrium fluoride; magnesium fluoride; a mixture of silicon oxide and aluminum oxide; and a mixture thereof, the high refractive index layer is formed of a material selected from the group consisting of scandium oxide; niobium oxide; lanthanum oxide; praseodymium titanate; lanthanum titanate; lanthanum aluminate; yttrium oxide; hafnium oxide; zirconium oxide; tantalum oxide; a mixture of tantalum oxide and titanium; silicon nitride; and a mixture thereof.

Abstract: An optical head device and an optical recording and reproducing apparatus using this optical head device, which can record information and reproduce the recorded information at any of optical recording media, such as a next generation optical recording medium, in which the wavelength of the light source is made to be shorter, the numerical aperture of the objective lens is made to be higher, and the thickness of the recording medium is made to be thinner, and conventional recording media of DVD and CD standards, are provided. A light having wavelength of 405 nm, emitted from one of optics, is inputted to an objective lens as a collimated light, and is focused on a disk having thickness of 0.1 mm. A light having wavelength of 650 nm, emitted from the other of optics, is inputted to the objective lens as a diverged light, and is focused on a disk having thickness of 0.6 mm.

Abstract: An objective optical element for use in an optical pickup apparatus, includes two or more optical elements having a first surface having a first phase difference providing structure and a second surface having a second phase difference providing structure, wherein each of the first and second phase difference providing structures emit a diffracted light flux corresponding to each of the entering first-third light fluxes, or emit a transmitting light flux which is not applied a diffractive action corresponding to each of the entering first-third light fluxes, and the first-third light fluxes enter into the objective optical element as an almost infinite parallel light flux for information reproducing and/or recording on the first-third optical information recording media respectively.

Abstract: An optical disk drive (101) for optically recording and/or reproducing information signals is provided in which the power of a light beam emitted from an optical head (104) to an optical disk (102) is controlled by an optical-coupling efficiency varying elements (214, 215) correspondingly to the type of the optical disk, recording layer in a multilayer optical disk and a mode of operation selected while a variation of the optical-coupling efficiency is being detected by a light-detecting element (216), thereby positively varying the optical-coupling efficiency in a minimum necessary time. Thus, the power of the light beam focused on the optical disk can be varied in a wide range without having to extremely raise the ratio in output power between modes of operation at a light source (212).

Abstract: An objective optical system focuses light from a light source onto at least two different types of optical recording media having different substrate thicknesses in order to record or reproduce information on the optical recording media by using a variable refractive power element and an objective lens. The variable refractive power element may be a liquid crystal element with concentric zones that serves as a transparent plate having no convergence effect when no voltage is applied when selecting an AOD, DVD, or CD and as a converging lens when a voltage is applied when selecting a BD. Alternately, the variable refractive power element may electrically vary the refractive index of a nanoparticle dispersion or at least one liquid of a two-liquid lens element. A diffractive optical element may be used to assist in focusing light to four recording media. An optical pickup device includes the objective optical system.

Abstract: An optical pickup apparatus has a semiconductor laser source which emits a laser beam in a wavelength band of 405 nm having an elliptic light intensity distribution; a beam shaping element which shapes the light intensity distribution of the laser beam; a polarizing beam splitter having a polarized light separation film in contact with the air and reflecting the laser beam shaped by the beam shaping element on the polarized light separation film; and an objective lens which focuses the laser beam reflected on the polarized light separation film onto an optical information recording medium.

Abstract: There is provided a filter for an optical recording medium, including: a plurality of high refractive index layers, and a plurality of low refractive index layers, wherein the high refractive index layers and the low refractive index layers are alternately deposited, the total number of the high refractive index layers and the low refractive index layers deposited is an even number in the range of 10 to 20, and the high refractive index layers and the low refractive index layers are different in thickness from one another. Also, there is provided an optical recording medium using the filter for an optical recording medium.

Abstract: An optical reading apparatus with aberration-correcting functionality includes a light source, a lens, a liquid crystal layer and an electrode set. The light source of the optical reading apparatus emits light, which is converged onto a storing medium by the lens for accessing data stored in the storage medium. The liquid crystal layer is disposed in an optical path between the light source and the storage medium. The electrode set provides a variable electrical field across the liquid crystal layer for changing the refractive index of the liquid crystal layer. Aberration of the optical reading apparatus can thus be corrected.

Abstract: When a light-receiving element receives a first laser beam, an output power detection unit detects a differential quantum efficiency value of the first laser beam. A control unit judges whether or not an intensity filter and a filter driving unit are operated in accordance with a control signal output from the control unit by using the differential quantum efficiency value from the output power detection unit.

Abstract: An optical head device includes a focusing optical system for focusing a laser beam emitted from a semiconductor laser light source on an optical information medium with an objective lens. A chromatic aberration correction element for correcting chromatic aberration occurring in the objective lens is provided between the semiconductor laser light source and the optical information medium. A light distribution correction element in which the transmittance increases with the distance from the center of the aperture surface of the objective lens is provided so as to correct a reduction of the intensity of the light incident on the aperture surface of the objective lens with the distance from the center of the aperture surface.

Abstract: There is provided a light receiving circuit capable of preventing an output variation of the light receiving circuit due to a change in ambient temperature with a simple configuration. The light receiving circuit is provided with a photodiode 4 for LD power monitoring and an I-V amplifier 5 connected with a feedback resistor 13, wherein a light receiving section 16 of the photodiode 4 is covered with a protective film 19. Temperature dependences between a light transmittance of the protective film 19 in accordance-with a shift of a wavelength of a laser beam due to a change in ambient temperature, and a resistance value of the feedback resistor 13 are set in such a way that they may be mutually compensated and an output voltage from the light receiving circuit may be constant for a temperature change.

Abstract: An optical scanning device (3) for scanning a multiple of types of optical recording media. The optical scanning device is provided with a filtering means (301) that is arranged and configured such that when scanning an optical recording medium (15) having plurality of information layers (L0, L1) radiation reflected by another information layer than the information layer being scanned is not reaching the radiation detector (38), while the filtering means is substantially not affecting the radiation towards the radiation detector when another type of recording media is scanned. Improved data signal reproduction and tracking servo signals are obtained.

Abstract: The present invention relates to a method for improving the playability of non-ideal optical disks. Initially, an asymmetry (AsI) of the optical carrier is determined. If the asymmetry is above a pre-defined first threshold then a step of decreasing an upper cut-off frequency (HPF) to a first cut-off frequency (HPF1) of a high pass filtering (BPF) performed on a data channel (HF) in response to the asymmetry (AsI) is undertaken. Subsequently, a step of optimizing an amplification level of a radial error signal (RE) and/or a focus error signal (FE) of a servomechanism controlling the optical carrier is undertaken. Finally, a last step of determining a second indication of asymmetry (As2) of the data channel (HF) from the optical carrier is performed. The invention is advantageous because a better indication of the asymmetry is provided because the asymmetry is assessed two consecutive times interrupted by a high pass filter adjustment.

Abstract: In the present invention, by utilizing the difference between the polarization directions of an optical beam and a reflected optical beam, a neutral density filter part of a variable filter in an optical pickup reduces the light amount of the optical beam and directs the optical beam to the objective lens, and directs the reflected optical beam to a photodetector being a photodetection unit with slight change in the light amount of the reflected optical beam. When reducing a transmitted beam, which is the optical beam transmitted by diffracting the optical beam using a diffraction grating, the irradiation positions of first-order optical beams being diffracted±first-order optical beams on the recording layer of an optical disc are dispersed.

Abstract: An optical head device and an optical recording and reproducing apparatus using this optical head device, which can record information and reproduce the recorded information at any of optical recording media, such as a next generation optical recording medium, in which the wavelength of the light source is made to be shorter, the numerical aperture of the objective lens is made to be higher, and the thickness of the recording medium is made to be thinner, and conventional recording media of DVD and CD standards, are provided. A light having wavelength of 405 nm, emitted from one of optics, is inputted to an objective lens as a collimated light, and is focused on a disk having thickness of 0.1 mm. A light having wavelength of 650 nm, emitted from the other of optics, is inputted to the objective lens as a diverged light, and is focused on a disk having thickness of 0.6 nm.

Abstract: A phase shift element has a tiered phase difference pattern portion, in which an inner circular side tiered phase difference pattern portion is continuously connected with an outer circular side tiered phase difference pattern portion based on a phase function curve obtained by a single phase-function with a wavelength having the same value as a reference wavelength ?1 of a first laser light being determined as a designed wavelength ?, formed in annular shapes on one surface thereof. A tier pitch of tiers of the inner circular side tiered phase difference pattern portion is set to a height corresponding to a phase difference of substantially 1? and, on the other hand, a tier pitch of tiers of the outer circular side tiered phase difference pattern portion is set to a height corresponding to a phase difference of substantially m? (where m is a natural number which does not include 0) or a height corresponding to the phase difference of substantially m? by changing a value of m for each step.