Abstract: The invention presents an optical element with which an optical head can be configured, in which there is little deterioration of the correctional effect when the objective lens shifts, as well as an optical head and an optical recording/reproducing apparatus using such an optical element. The invention also presents a novel optical recording/reproducing apparatus and optical recording/reproducing method. The optical element, includes a first voltage application electrode 13, a first opposing electrode 17 arranged in opposition to the first voltage application electrode 13, and a first phase changing layer 15 arranged between the first voltage application electrode 13 and the first opposing electrode 17. By changing a voltage between the first voltage application electrode 13 and the first opposing electrode 17, a phase that converts plane waves into spherical waves is imparted on light that is incident on the first phase changing layer 15.

Abstract: An aberration correcting element includes a first aberration correction element movable along the optical axis of the light beam for correcting the aberration of the light beam; a driver for positioning the first aberration correction element along the optical axis in response to a drive control signal; a second aberration correction element having a plurality of phase adjustment portions each generating an amount of phase change in the light beam, the amount corresponding to an adjustment signal; a phase adjuster for supplying the adjustment signal to the respective adjustment portions in response to a phase control signal; a light receiver for receiving the light beam reflected from the recording medium to generate a light-receiving signal; and a controller for generating the drive control signal and the phase control signal based on the light-receiving signal.

Abstract: A optical scanning device (1) for scanning an information layer (2) with a radiation beam (25) in a writing mode and a reading mode comprises a radiation source (7) for emitting the beam and an objective lens (10) for converging the beam so as to form a scanning spot (19) in the information layer. The device also includes a scanning spot power switch (20) for switching the size of the cross-section of the beam between a first size at the writing mode and a second, larger size at the reading mode so as to switch the rim intensity of the beam between a first intensity level (Irim,writing) at the writing mode and a second, higher intensity level (Irim,reading) at the reading mode, thereby switching the light power of the scanning spot between a first power level (Pwriting) at the writing mode and a second, lower power level (Preading) at the reading mode.

Abstract: The invention presents an optical element with which an optical head can be configured, in which there is little deterioration of the correctional effect when the objective lens shifts, as well as an optical head and an optical recording/reproducing apparatus using such an optical element. The invention also presents a novel optical recording/reproducing apparatus and optical recording/reproducing method. The optical element, includes a first voltage application electrode 13, a first opposing electrode 17 arranged in opposition to the first voltage application electrode 13, and a first phase changing layer 15 arranged between the first voltage application electrode 13 and the first opposing electrode 17. By changing a voltage between the first voltage application electrode 13 and the first opposing electrode 17, a phase that converts plane waves into spherical waves is imparted on light that is incident on the first phase changing layer 15.

Abstract: An optical pickup and an optical information recording/reproducing device are provided, each of which is capable of forming a super-resolution spot to conduct micro-mark recording, and does not undergo signal degradation due to an increased sidelobe in a reproducing operation. A variable phase filter having three regions to produce a phase difference in a radial direction is used, to provide a phase difference of ? between the center region and the side regions in a recording operation, so that a super-resolution spot is formed on a recording layer of the optical disk. In a reproducing operation, a phase difference is nullified between the regions of the variable phase filter, so that a normal light spot at a diffraction limit having a smaller sidelobe is formed. The variable phase filter can be formed with a homogeneous-alignment liquid crystal element.

Abstract: A disk recording apparatus for recording data to a disk includes: a reading and writing element for emitting a read beam onto the disk to read out recorded data therefrom while emitting a plurality of write beams simultaneously onto the disk to record data thereto in parallel; and a controlling element for controlling where to emit on the disk the plurality of write beams in accordance with the data read out by the reading and writing element.

Abstract: An optical pickup is provided for recording and reproduction of information onto and from an optical disk. In the optical disk, in a forward optical path, a single polarized optical beam is converted to plural polarized optical beams. Polarization modes of the plural polarized optical beams are then converted to a polarization mode suitable for one of the recording and the reproduction to produce polarization-converted optical beams and to radiate the polarization-converted optical beams to the disk. In the backward optical path, polarization modes of the polarization-converted optical beams reflected from the disk are returned to the same polarization mode as that of the plural polarized optical beams, so that plural polarized reflected optical beams are produced. Polarization modes of the plural polarized reflected optical beams are then returned to the same polarization mode as the single polarized optical mode.

Abstract: An aberration correcting unit is provided for correcting an aberration of a light beam radiated onto an object to be detected and then reflected from the object. This unit comprises an aberration correcting device comprising a first corrector configured to correct the aberration of the light beam radiated onto the object; and a second corrector configured to correct the aberration of the light beam reflected from the object and to divide the reflected light beam into a plurality of light beams. The aberration correcting unit further comprises a first driver configured to drive the first corrector and a second driver configured to drive the second corrector.

Abstract: The astigmatic aberration in an optical system is to be adjusted. Specifically, in an optical disc device on which can be selectively loaded a first optical disc having a first index of double refraction or a second optical disc having a second index of double refraction larger than said first index of double refraction, and which includes a liquid crystal device 31 between a light source 11 and an objective lens 15 converging a light beam radiated from said light source on the optical disc 2 loaded on the optical disc device, the voltage applied to the liquid crystal device 31 is adjusted to correct the coma aberration or the astigmatic aberration for the first disc or the second disc, respectively.

Abstract: An aberration correction apparatus includes a first aberration correction element having aberration correction portions, a second aberration correction element which causes the wave front of the transmitted light beam to have a blaze hologram shape, a discriminator which discriminates the aberration of the reflected light beam, a coarse phase adjuster which drives the second aberration correction element on the basis of the magnitude of the aberration of the reflected light beam, and a fine phase adjuster which corrects aberration remained after the aberration correction by the coarse phase adjuster.

Abstract: The astigmatic aberration in an optical system is to be adjusted. Specifically, in an optical disc device on which can be selectively loaded a first optical disc having a first index of double refraction or a second optical disc having a second index of double refraction larger than said first index of double refraction, and which includes a liquid crystal device 31 between a light source 11 and an objective lens 15 converging a light beam radiated from said light source on the optical disc 2 loaded on the optical disc device, the voltage applied to the liquid crystal device 31 is adjusted to correct the coma aberration or the astigmatic aberration for the first disc or the second disc, respectively.

Abstract: A device for reading and/or writing a record carrier (13), the device comprising converging means (35, 45, 47, 106, 108) for focusing a radiation beam (27, 101) originating from a radiation source (25) on the record carrier (13). The converging means comprises polarization means (103) and a diffraction grating (107) of birefringent material. Dependent on the direction of polarization, the radiation beam (101) is focused on one of two possible surfaces corresponding to DVD and DVR, respectively. A diffraction grating (107) is present in a central area of the radiation beam (101) and causes diffraction of a first order for one direction of polarization of the radiation beam (101) and diffraction of a second, higher, order for a second direction of polarization of the radiation beam (101). The diffraction grating (107) is made of birefringent material.

Abstract: An optical disk device is provided with an optical pickup that includes a convergent optical system having an objective lens for converging a light beam emitted from the laser light source to form a microspot on an optical disk and an aberration correcting optical system for controlling a spherical aberration of the convergent optical system, and performs information recording or reproduction with respect to a multi-layer optical disk having at least a first recording layer and a second recording layer. In the optical disk device, an operation of changing a correction quantity of the spherical aberration from a value adequate for the first recording layer to a predetermined value is started before an operation of moving a focus position of the microspot from the first layer to the second layer is completed.

Abstract: To stably carry out recording and reproducing to and from a high density optical disk without using a double servo in the optical disk using a high NA objective lens. A detection of a spherical aberration and a detection of a coma aberration in a radial direction are simultaneously performed, and the coma aberration generated with the offset of an objective lens 109 is corrected in real time, thus enlarging an allowable offset amount of the objective lens. In order to simultaneously detect the spherical aberration and the coma aberration, focal shift and tracking shift signals in an inside region and outside region of reflected light flux are detected respectively, and the differential signals are set as spherical aberration and coma aberration signals.

Abstract: A single high resolution holographic pickup, for reading/writing both a CD and DVD optical recording medium, has an electrical tuning control for applying a DC and AC signal to a tunable Bragg cell, which AC is phase locked with respect to the fundamental repetition frequency of the recorded data on the CD to produce accurate tracking. A special high resolution holographic lens is recorded within the Bragg cell that focuses the light signals read off of the optical storage mediums upon a pickup detector, and its focal length is varied to read a selected CD and or DVD from a group of CDs or DVDs in response to changes in the DC applied to the Bragg cell. The holographic lens within the Bragg cell is formed by an interference pattern produced by interfering light emitted from the tip of a one micron optical fiber and a plane broad light beam.

Abstract: The astigmatic aberration in an optical system is to be adjusted. Specifically, in an optical disc device on which can be selectively loaded a first optical disc having a first index of double refraction or a second optical disc having a second index of double refraction larger than said first index of double refraction, and which includes a liquid crystal device 31 between a light source 11 and an objective lens 15 converging a light beam radiated from said light source on the optical disc 2 loaded on the optical disc device, the voltage applied to the liquid crystal device 31 is adjusted to correct the coma aberration or the astigmatic aberration for the first disc or the second disc, respectively.

Abstract: An optical head device including a phase correcting element having an anisotropic optical medium sandwiched between a pair of substrates. The paired substrates have surfaces provided with electrodes for voltage application to the anisotropic optical medium. One electrode on at least one of the substrates has two or more power supply electrodes provided thereon at different positions, thereby providing different voltages to the respective power supply electrodes. The phase correcting element is provided between a collimating lens and a quarter wave plate in the optical head device.

Abstract: The invention presents an optical element with which an optical head can be configured, in which there is little deterioration of the correctional effect when the objective lens shifts, as well as an optical head and an optical recording/reproducing apparatus using such an optical element. The invention also presents a novel optical recording/reproducing apparatus and optical recording/reproducing method. The optical element, includes a first voltage application electrode 13, a first opposing electrode 17 arranged in opposition to the first voltage application electrode 13, and a first phase changing layer 15 arranged between the first voltage application electrode 13 and the first opposing electrode 17. By changing a voltage between the first voltage application electrode 13 and the first opposing electrode 17, a phase that converts plane waves into spherical waves is imparted on light that is incident on the first phase changing layer 15.

Abstract: Tilt which is inclination of a normal of optical disk relative to optical axis of optical head is corrected with a liquid crystal element. In a driver for the liquid crystal element, a periodic waveform generator generates periodic waveform and an inverting element inverts the periodic waveform. The periodic waveform and the inverted waveform are connected to two ends of a potential divider which provides partial voltages. The periodic waveform is connected to a common electrode of the liquid crystal element, and the partial voltages of the potential divider are connected to electrodes opposing the common electrode. A structure of a driver circuit for each direction is simple. Tilt in a plurality of directions can be performed independently of each other. Spherical aberration is also corrected. When the liquid crystal element is mounted to a fixed component, deterioration due to jitters is reduced.

Abstract: An optical disk device is provided with an optical pickup that includes a convergent optical system having an objective lens for converging a light beam emitted from the laser light source to form a microspot on an optical disk and an aberration correcting optical system for controlling a spherical aberration of the convergent optical system, and performs information recording or reproduction with respect to a multi-layer optical disk having at least a first recording layer and a second recording layer. In the optical disk device, an operation of changing a correction quantity of the spherical aberration from a value adequate for the first recording layer to a predetermined value is started before an operation of moving a focus position of the microspot from the first layer to the second layer is completed.

Abstract: The present invention provides a compact liquid crystal optical element for optical modulation and a compact optical device. A liquid crystal optical element for optical modulation is prepared by connecting two transparent substrates, each formed with a transparent electrode and an orientation film, with a sealing member, leaving a clearance between the two transparent substrates. On at least one surface of at least one of these transparent substrates, a diaphragm is formed using a shielding member. With this arrangement, it is possible to provide a more compact liquid crystal optical element than has been conventionally available. At the same time, it is possible to substantially reduce the occurrence of noise. Therefore, it is possible to provide a liquid crystal optical element and an optical device having excellent performance.

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: A liquid crystal element is provided as a polarization plane rotating device between a laser beam source and a beam splitter. Light emitted from the laser beam source passes through the liquid crystal element and the beam splitter, and is converted into parallel light by a collimating lens. The collimated light is incident on a first light-selection device, is reflected at a flat first reflecting surface or a concave second reflecting surface, and is then incident on a super-resolution cut-off filter as a second light-selection device. The light having passed through the second light-selection device is incident on an objective lens, and is converged onto a recording surface. The selection of the reflecting surface of the first light-selection device is determined based on an operation mode of the liquid crystal element.

Abstract: A laser beam emitted from a laser diode and having a wavelength of 780 nm is S-polarized. A polarization plane rotating means (?/4 phase plate) is disposed between a super-resolution cut-off filter comprising a polarizing filter film and an objective lens. When reading on DVD, the objective lens, the polarization plane rotating means and the super-resolution cut-off filter in combination are set to the optical path. The S-polarized laser beam is focused to a micro spot diameter by super-resolution effects by the super-resolution cut-off filter together with the objective lens. Also, the S-polarized laser beam reflected at a disk and traveling backward along the incoming optical path is converted into a P-polarized laser beam while passing backward through the polarization plane rotating means. The P-polarized laser beam passes through the super-resolution cut-off filter without loss is received by a photo-detector.

Abstract: An optical pickup device including a light source, an objective lens for converging a light beam emitted from the light source at a signal recording surface of an optical recording medium and irradiating the signal recording surface of the optical recording medium with the light beam, and a liquid crystal device, disposed in a light path between the light source and the objective lens, for giving a predetermined phase distribution to transmission light that passes through the liquid crystal device, with both front and back surfaces of the liquid crystal device being flat surfaces. In the optical pickup device, the liquid crystal device is constructed by sandwiching a liquid crystal molecule layer by a pair of transparent substrate.

Abstract: The invention presents an optical element with which an optical head can be configured, in which there is little deterioration of the correctional effect when the objective lens shifts, as well as an optical head and an optical recording/reproducing apparatus using such an optical element. The invention also presents a novel optical recording/reproducing apparatus and optical recording/reproducing method. The optical element, includes a first voltage application electrode 13, a first opposing electrode 17 arranged in opposition to the first voltage application electrode 13, and a first phase changing layer 15 arranged between the first voltage application electrode 13 and the first opposing electrode 17. By changing a voltage between the first voltage application electrode 13 and the first opposing electrode 17, a phase that converts plane waves into spherical waves is imparted on light that is incident on the first phase changing layer 15.

Abstract: In an optical pickup, an objective lens and an aberration correcting mechanism are held so that they can be moved together.

Abstract: A tilt servo control device of an apparatus for recording information on and reproducing information from an optical recording medium set in the apparatus, the apparatus comprising an optical system for leading a laser beam emitted from a light source to a recording surface of the optical recording medium and a laser beam reflected by the recording surface of the recording medium to a photo detector and a read signal generator for generating a read signal in accordance with an output signal of the photo detector. The tilt servo control device determines a type of the optical recording medium, generates a tilt drive signal so as to reduce a tilt angle at a position of the laser beam irradiating the recording surface and an optical axis of the laser beam by a method for generating a tilt drive signal corresponding to the recording medium type, and drives a tilt angle adjuster for adjusting the tilt angle in accordance with the tilt drive signal.

Abstract: An optical disk device is provided with an optical pickup that includes a convergent optical system having an objective lens for converging a light beam emitted from the laser light source to form a microspot on an optical disk and an aberration correcting optical system for controlling a spherical aberration of the convergent optical system, and performs information recording or reproduction with respect to a multi-layer optical disk having at least a first recording layer and a second recording layer. In the optical disk device, an operation of changing a correction quantity of the spherical aberration from a value adequate for the first recording layer to a predetermined value is started before an operation of moving a focus position of the microspot from the first layer to the second layer is completed.

Abstract: An optical pickup apparatus for reproducing information from an optical information recording medium or for recording information onto an optical information recording medium, is provided with a first light source for emitting first light flux having a first wavelength; a second light source for emitting second light flux having a second wavelength, the first wavelength being different from the second wavelength; a converging optical system having an optical axis and a diffractive portion, and a photo detector; wherein in case that the first light flux passes through the diffractive portion to generate at least one diffracted ray, an amount of n-th ordered diffracted ray of the first light flux is greater than that of any other ordered diffracted ray of the first light flux, and in case that the second light flux passes through the diffractive portion to generate at least one diffracted ray, an amount of n-th ordered diffracted ray of the second light flux is greater than that of any other ordered diffracted

Abstract: An objective lens for recording and/or reproducing information of an optical information recording medium, is a single lens having an aspherical surface on at least one surface. The objective lens is a finite conjugate type to converge a divergent light flux from a light source onto an information recording plane of the optical information recording medium and satisfies the following formula: NA?0.7 where NA is an image-side numerical aperture necessary for conducting recording and/or reproducing information of the optical information recording medium.

Abstract: The present invention can simplify and miniaturize an optical pickup and further can prevent the deterioration of various characteristics even if an aberration correction mechanism is composed of a liquid crystal and the like by transmitting a drive signal of an actuator and a drive signal of an aberration correction mechanism by multiplexing them.

Abstract: The present invention is capable of selectively reproducing an information signal from an optical disk with any of a plurality of types having different track pitches of recording tracks, that is, capable of selectively reproducing an information signal from an optical disk having a low or high recording density by determining the type of the optical disk, that is, determining whether a mounted optical disk is a low-recording-density optical disk or a high-recording-density optical disk. The present invention deliberately generates aberration in an optical beam by controlling a voltage applied to a liquid-crystal device in order to vary the diameter of the optical beam in accordance with the determined type of the optical disk.

Abstract: An optical pickup device which includes (A) a light source, and (B) an objective lens and an aberration correcting optical system which are located in a light path from the light source to an optical recording medium is so arranged that the aberration correcting optical system imparts a phase distribution to luminous flux which transmits the aberration correcting optical system, so as to correct a predetermined aberration; and an amount of phase of the aberration correcting optical system when correcting the aberration is set in such a manner that the aberration correcting optical system imparts a larger amount of phase at a position farther from a point where the aberration correcting optical system crosses an optical axis of light emitted from the light source. With this, it is possible to increase a tolerance for the center misalignment of the objective lens so as to reduce aberration caused by the center misalignment.

Abstract: The quantity of spherical aberration correction is predetermined for each recording plane of an optical disk on which focusing control is performed. Before operating the focusing control, the quantity of spherical aberration to be corrected by an aberration correcting system is set based on an output signal from an aberration correction quantity switching device that corresponds to the type of the optical disk and the recording plane to be subjected to the focusing control. This makes it possible to perform stable focusing control on each recording plane of a multi-layer optical disk with high density by using an objecting lens having a large NA after spherical aberration has been corrected properly.

Abstract: Light emitted from a laser is divided into two light waves so that the ratio of the power of one light wave to the power of the other will be appropriate. The resultant light waves are irradiated to the same track on a medium. The preceding spot is used for erasure, and modulated so that the same pattern as the one formed with a recording pulse will be formed. The high-power component of the modulated light of the erasing spot causes the temperature of a recording layer to be equal to or higher than the melting point. The medium-power component of the modulated light forms a crystallizing temperature area on the recording layer. A liquid crystal diffraction grating is used to divide power, and a power division ratio is variable and controllable.

Abstract: An optical pickup includes a light emitting unit, an object lens, and a correction unit. The object lens focuses a beam of light onto a recording surface of an optical disc. The correction unit has a light transmitting surface. A plurality of electrodes are arranged on a plurality of divided areas of the light transmitting surface. The correction unit corrects an aberration caused by a tilt of an optical axis of the beam of light relative to the recording surface of the recording disc by applying voltages to the electrodes. The applied voltages correspond to the tilt of the optical axis of the beam of light. The correction unit also changes phases of the beam of light passing through the divided areas of the light transmitting surface.

Abstract: An aberration correcting optical unit includes an optical element for causing a phase change to light passing therethrough by the application of voltage and electrode layers for applying voltages to the optical element. The optical element is sandwiched between the electrode layers. At least one of the electrode layers includes a plurality of electrodes which are electrically isolated from one another. The plurality of electrodes are disposed such that an electric field generated in a portion of the optical element corresponding to a portion between the plurality of electrodes is larger than a predetermined intensity when a predetermined voltage is applied to the optical element.

Abstract: An optical disk device has a light source which emits light; and light converging means of, in each of signal mark forming regions, each of lands, or each of grooves of an optical disk, converging the light from the light source onto a signal surface of the optical disk with selectively positioning a signal mark at any one of plural positions which are arranged in a direction that is substantially perpendicular to tracks, each of the signal mark forming regions surrounded by adjacent two of boarder lines which are between two the tracks on the signal surface of the optical disk, and which are substantially parallel to the tracks, and each of which substantially divides an area between adjacent tracks in two parts.

Abstract: An optical wavefront modifier (27) is adapted for modifying a wavefront of an optical beam passing through the modifier. The modifier comprises a first and a second transparent electrode layer (42?, 43?) and a flat medium (46) for modifying the wavefront in dependence on electrical excitation and arranged between the electrode layers. The first electrode layer (42?) comprises three or more electrodes (51-55) of a transparent, conductive material. The electrode layer also comprises a series arrangement of resistors, comprising three terminals (48, 48?, 48?) connected to the electrodes and resistors (49, 49?) connecting the terminals. The resistors are made of the same transparent conductive material as the electrodes.

Abstract: A phase device for providing a phase difference between an inner radius portion and an outer radius portion of a light beam which is emitted from a light source is provided in an optical path between the light source of an optical pickup apparatus and an objective lens. The light beam to which the phase difference has been provided is converged by the objective lens and irradiated to an optical disc. An interference of an inner radius portion and an outer radius portion of the returning light beam caused when the light beam is diffracted by the optical disc with ±1 primary diffracted light caused by the diffraction is suppressed. Therefore, an intensity fluctuation of the returning light beam caused by the interference is suppressed. A spherical aberration error showing a thickness error of the optical disc and a focusing error having a high linearity can be detected with high precision on the basis of the returning light.

Abstract: A compact liquid crystal optical element for optical modulation and a compact optical device. A liquid crystal optical element for optical modulation is prepared by connecting two transparent substrates, each formed with a transparent electrode and an orientation film, with a sealing member, leaving a clearance between the two transparent substrates. On at least one surface of at least one of these transparent substrates, a diaphragm is formed using a shielding member. With this arrangement, it is possible to provide a more compact liquid crystal optical element than has been conventionally available. At the same time, it is possible to substantially reduce the occurrence of noise. Therefore, it is possible to provide a liquid crystal optical element and an optical device having excellent performance.

Abstract: An aberration correcting unit includes: a first element having a liquid crystal sandwiched between first electrode layers, the first element having a first predetermined orientation direction and providing a light with a phase change by applying a voltage; a second element having a liquid crystal sandwiched between the second electrode layers, the second element having a second predetermined orientation direction that is substantially perpendicular to the first orientation direction and providing a light with a phase change by applying a voltage; and a polarization-direction changing element which is arranged between a light source of the light beam and the first and second elements to change a polarization direction of the light beam.

Abstract: An optical member of the invention is an optical member for photolithography used together with light having a wavelength of not more than 250 nm. The optical member is made of a fluoride crystal in which a maximum diameter dmax (cm) of scattering bodies existing internally and a quantity ns of the scattering bodies per 1 cm3 satisfy a condition represented by following formula (1): 0<dmax2×ns<6.5×10?4 (cm?1)??(1).

Abstract: A light orientation film and a liquid crystal thin film are formed adjacent to each other. Light is irradiated to the light orientation film and the liquid crystal thin film, so as to cause the light orientation film to be orientated while viscosity of the liquid crystal thin film is lowered by a temperature increase by the light irradiation, so that an intermolecular force on the boundary between the light orientation film and the liquid crystal thin film causes the liquid crystal molecules in the liquid crystal thin film to the orientation of the light orientation film. By this orientation of the liquid crystal molecules, recording information is maintained. Thus, it is possible to realize a sufficient signal amount while using the light orientation film as well as to obtain a thermal stability and a stability against light irradiation.

Abstract: Disclosed are a compatible type optical pick-up device for writing/reading data at a high density and a method for operating the optical pick-up device, thereby allowing the optical pick-up device to be easily assembled and improving optical efficiency. The compatible type optical pick-up device includes a laser beam source for outputting a laser beam having a writing mode power level for writing data from a disk, a collimator lens for collimating the laser beam outputted from the laser beam source, an optical attenuator located on an optical route of the laser beam passing through the collimator lens for attenuating the power of the laser beam, and an objective lens for converging the laser beam, incident thereon, onto the disk.

Abstract: The invention presents an optical element with which an optical head can be configured, in which there is little deterioration of the correctional effect when the objective lens shifts, as well as an optical head and an optical recording/reproducing apparatus using such an optical element. The invention also presents a novel optical recording/reproducing apparatus and optical recording/reproducing method. The optical element, includes a first voltage application electrode 13, a first opposing electrode 17 arranged in opposition to the first voltage application electrode 13, and a first phase changing layer 15 arranged between the first voltage application electrode 13 and the first opposing electrode 17. By changing a voltage between the first voltage application electrode 13 and the first opposing electrode 17, a phase that converts plane waves into spherical waves is imparted on light that is incident on the first phase changing layer 15.

Abstract: A recording apparatus and method for recording a mark on a recordable recording medium includes an optical pickup having a light source and an objective lens for focusing light emitted from the light source as a light spot on a recording surface of a recording medium. When recording on a rewritable recording medium, the size of the light spot formed on the recording surface of a recording medium is increased more than when recording on a write once recording medium and/or reproducing from a recording medium. Accordingly, when recording on a rewritable recording medium, the size of a light spot is enlarged more than when recording on an only once writable recoding medium and/or reproducing from a recording medium. Thus, when a mark is recorded on the rewritable recording medium, the erasing rate of an existing recorded phase-change mark is increased to improve the overwriting characteristics.

Abstract: The present invention is directed to an optical head adapted for performing recording or reproduction of information signals with respect to an optical disc (102), which controls light coupling efficiency with respect to light beams irradiated onto the optical disc (102) by light coupling efficiency adjustable element such as a liquid crystal element (214), etc. in accordance with type of the optical disc (102), recording surface of multi-layer optical disc and/or operation mode to change power of light beams irradiated onto the optical disc (102) to a large extent without excessively increasing change quantity of output power of a semiconductor laser element (212). A beam splitter (218) divides incident light beams of P-polarized light at a predetermined ratio to allow the light beams thus obtained to be incident on a light detector (219) for disc surface power monitor.

Abstract: An optical disk device has an aperture of an objective lens in an incoming path of a beam from a semiconductor laser to an optical disk formed larger than an aperture in a return path from the optical disk or an aperture is varied in recording and in reproduction. This configuration improves recording/reproducing ability since light is focused on an optical disk with high numerical aperture. In addition, since reflected light from the optical disk is detected with low numerical aperture, margins for tilt and defocus are not reduced. Furthermore, since unnecessary signal components contained in the reflected light can be eliminated, a S/N (signal-to-noise ratio) of an information signal also increases. Thus, a high-performance optical disk device can be obtained. Alternatively, by varying the aperture of an objective lens in recording and in reproduction, an optical disk device in which recording density and recording quality are increased without deteriorating reproduction quality can be obtained.