Abstract: There are disclosed an optical storage device for accessing an optical recording medium such as a phase change type of optical disk and an optical magnetic disk, and a liquid crystal device preferably applicable to such a optical storage device. The liquid crystal device has a structure that two liquid crystal layers, each of which has stripe-like shaped electrodes arranged in a direction perpendicularly intersecting one another, are superposed. This structure makes it possible to effectively correct an aberration caused by a change in a depth from a surface of an optical recording medium to a condensing point, for example, in cases of unevenness in thickness of a protective layer and a multi-layer recording.

Abstract: There are disclosed an optical storage device for accessing an optical recording medium such as a phase change type of optical disk and an optical magnetic disk, and a liquid crystal device preferably applicable to such a optical storage device. The liquid crystal device has a structure that two liquid crystal layers, each of which has stripe-like shaped electrodes arranged in a direction perpendicularly intersecting one another, are superposed. This structure makes it possible to effectively correct an aberration caused by a change in a depth from a surface of an optical recording medium to a condensing point, for example, in cases of unevenness in thickness of a protective layer and a multi-layer recording.

Abstract: The present invention relates to an optical device with a variable numerical aperture (NA), which utilizes special optical properties of a liquid crystal medium. Through the design of external electrodes and a circuit control unit, the refraction index of the liquid crystal medium can be modulated by the external voltage so that the beam passing through the LCD produces diffraction. An optical device with a variable focal point is thus formed by combining this LC diffractive device and an objective lens. So the present invention provides an optical device with focal points of different numerical apertures by varying the external voltage, whereby the device can read optical disks of all specifications.

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.

Abstract: Disclosed herein is an optical pickup device and method of adjusting the same. The optical pickup device and method of adjusting the same of the present invention can correct aberrations due to variation of thickness of an optical disc and dispersion of the emission wavelength by a semiconductor laser, which are generated in manufacturing processes of the optical disc and the optical pickup device, correct aberrations generated in recording/reproducing of the optical disc, due to variation of the emission wavelength and secular changes in the environment of the semiconductor laser, simplify and miniaturize the construction of the optical pickup device, and easily reduce manufacturing cost thereof.

Abstract: In an optical head apparatus for an optical recording medium, including a light source for emitting a light beam, an objective lens for focusing the light beam at the optical recording medium and receiving a reflected light beam from the optical recording medium, and a photodetector for receiving the reflected light beam from the objective lens, a unit is provided between the light source and the objective lens to generate a main beam and a sub beam from the light beam. The intensity distributions of the main beam and the sub beam are different from each other, and the sub beam is divided into a plurality of portions having different phase distributions from each other. The photodetector includes photodetecting portions for each of the main beam and the sub beam, thus obtaining a push-pull signal from each of the main beam and the sub beam.

Abstract: An optical scanning device for scanning an optical record carrier. A high numerical aperture objective lens system includes at least a first lens element (12) arranged to converge the beam to a certain extent and a second lens element (13) arranged to converge the beam to a greater extent. The device comprises a spherical aberration compensation optical subsystem including an electro-optical element for altering an optical path length in a spherical aberration generating region, which region is located in the optical path between the first lens element and the location of the record carrier in the device.

Abstract: A spherical aberration compensator for compensating for spherical aberration resulting from a thickness deviation of a recording medium. The spherical aberration compensator includes a central compensation which provides a phase distribution that is effective for compensating for spherical aberration resulting from the thickness deviation and a peripheral compensation portion which surrounds the central compensation portion and provides a phase distribution that is effective for reducing a worsening of the spherical aberration caused by axial displacement of an objective lens from the central compensation portion. The spherical aberration compensator effectively relieves an optical pickup having an objective lens of an NA of 0.7 or greater of worsening of the spherical aberration resulting from thickness deviation of the recording medium.

Abstract: A liquid-crystal tilt servo apparatus in which a reference voltage generating circuit is unnecessary for a liquid-crystal driving circuit and which has a simple circuit configuration and high reliability is realized. The liquid-crystal driving circuit has a DC removing circuit for removing a DC component of a driving signal generated on the basis of a tilt error correction control signal from a control unit and supplying a resultant signal to a liquid crystal device.

Abstract: The present invention relates to an optical head unit and an optical disk unit using the optical head unit. The head unit includes a wavefront transforming optical element control unit to controls a wavefront transforming optical element so as not to transform wavefront of a light beam focused on a recording layer by a focusing unit due to the thickness error of a light transmission layer positioned between the recording layer and the focusing unit based on an electrical signal outputted from a first light detector, and an output control unit that controls light amount of a light beam radiated by a light emitting unit based on the magnitude of the electrical signal outputted from the light detector.

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: An optical pickup apparatus that can adaptive for a plurality types of optical discs different in the layout condition such as a recording density, etc. and an optical recording/reproducing apparatus employing the optical pickup apparatus. In the optical pickup apparatus, first and second light sources generate a different wavelength of light beams. An optical system allows a light beam generated from any one of the first and second light sources to be selectively irradiated onto the optical disc and have an aperture number controller allowing the number of aperture of a light beam to have a different value. A photo detector detects the light beam reflected from the optical disc to be accessed to convert the same into an electrical signal. The apparatus is capable of accessing three types of optical discs different in the layout condition by utilizing an appropriate combination of a wavelength of the light beam with the number of aperture.

Abstract: An optical element has a phase change layer for changing the phase of light passing therethrough; a plurality of aberration correcting electrodes, arranged on one side of said phase change layer, for correcting optical aberrations, each of said aberration correcting electrodes being split into a plurality of regions; an insulating film interposed between said aberration correcting electrodes; and a specific electrode arranged on the other side of said phase change layer, and wherein: said aberration correcting electrodes, at least other than the outermost aberration correcting electrode as viewed from said phase change layer, have openings formed in prescribed positions, and each of said aberration correcting electrodes, other than the innermost aberration correcting electrode, faces said phase change layer through said openings formed in other aberration correcting electrodes.

Abstract: The present invention relates to a phase-change optical information recording medium comprising a recording layer which reversibly phase-changes between the crystalline phase and the amorphous phase by irradiation of a light having a recording wavelength of 390 to 430 nm, and a light transmittance thermally controllable layer showing a light transmittance varying according to temperature, in which the light transmittance increases at a rate of 0.2 to 0.7% /10° C.

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: An exposure apparatus of an optical disk master having a laser source, a deflector for deflecting a recording laser beam obtained based on the laser beam of the laser source and an objective lens for focusing the recording laser beam on an optical disk master, has

Abstract: Systems and methods for adjusting the polarization of one or more recording laser beams can correct (in whole or in part) for the changes in the polarization of the recording laser beam(s) caused by changes in the dominant polarization direction within the film substrates used for recording holograms. Using information about the dominant polarization direction of portions of holographic film substrate, a polarization adjusting device can be used to adjust the polarization of the recording laser beam(s) to compensate for the effects that changes in the dominant polarization direction of the holographic film substrate have on the recording laser beam(s) and thus the recorded hologram.

Abstract: In order to reproduce signals from a double-layer optical disc having two signal recording surfaces, a focus jump that the focusing of an objective lens from the one signal recording surface to the other signal recording surface is quickly achieved, is necessary. When a focus error signal (FE) from a pickup (60, 70) reaches a predetermined threshold value (Vcomp), a deceleration signal for decelerating the objective lens (42) is supplied to an actuator (47). Preferably, a deceleration pulse voltage is lowered step by step. The deceleration pulse voltage is determined in accordance with the maximum value (DFEmax) of a differential focus error signal (DFE) generated by differentiating the focus error signal (FE). Preferably, the address seeking is done simultaneously with the focus jump. The focus jump is performed in accordance with the layer-to-layer distance which is measured beforehand. The focus jump is performed by using a lens (143) having a controllable focal distance.

Abstract: An optical information recording medium includes a plurality of recording layers, a reflectance of at least one of the plurality of the recording layers in a non-initialized state with respect to a light beam for initialization being smaller than a reflectance of the same in an initialized state with respect to the light beam for initialization. The recording layers are initialized by irradiating, among the plurality of recording layers, the recording layer positioned farther from a light beam irradiation side with the light beam prior to irradiating the recording layer positioned closer to the light beam irradiation side, so that the initialized recording layers have no initialization irregularities.

Abstract: A liquid crystal element is provided as a polarization plane rotating means 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 means, 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 means. The light having passed through the second light-selection means is incident on an objective lens, and is converged onto a recording surface. The selection of the reflecting surface of the first light-selection means is determined based on an operation mode of the liquid crystal element.

Abstract: The present invention provides a multi-layer disk recording/reproducing apparatus that records information on a multi-layer disk having a plurality of recording layers or reproduces the information from the multi-layer disk. The objective lens condenses the light from a light source on the recording layers, and the focus actuator moves the objective lens so that the light forms a focused light spot on the recording layers. The a spherical aberration correcting mechanism is provided on a light path between the light source and the objective lens, and it corrects the spherical aberration generated by the multi-layer disk. The control device starts the movement of the focus actuator after the start of the movement of the spherical aberration correcting mechanism when performing the focus jump operation.

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

Abstract: An optical information storage unit for reproducing information recorded on lands and grooves of a magneto-optical recording medium by means of a reflected light obtained from a luminous flux which has been emitted from a light source, irradiated onto the recording medium and reflected from the recording medium. The optical information storage unit includes a first wave plate on which the reflected light from the magneto-optical recording medium is incident; a diffraction grating on which the light having been transmitted through the first wave plate is incident; a second wave plate on which the light having been transmitted through the diffraction grating is incident; and a polarization detecting unit on which the light having been transmitted through the second wave plate is incident.

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 substrates.

Abstract: An optical pickup unit includes a light source emitting a light beam, an objective lens focusing the light beam onto an information recording medium, a light detection part receiving the light beam reflected from the information recording medium, and a light blocking part selectively blocking a part of the light beam with respect to a radial direction. The light blocking part is provided in an optical path of the light beam centered on an optical axis.

Abstract: An optical reading apparatus includes an objective lens for focusing an optical beam; an actuator for driving the objective lens; an aberration detector for detecting spherical and coma aberration of the optical beam; an aberration correction element, including a liquid crystal element, for correcting the spherical and coma aberration by applying voltages to the liquid crystal element; a lens location detector for detecting displacement of the objective lens with respect to a reference location; and a controller for controlling the amount of aberration correction of the aberration correction element in accordance with the spherical aberration, the coma aberration, and the displacement.

Abstract: An optical pickup is provided with: a light emitting device for emitting a light beam onto a record medium comprising a transparent layer, which is transparent for the light beam and through which the light beam is transmitted; a light receiving device for receiving a reflection light of the light beam from the record medium; a liquid crystal compensating device for compensating birefringence, which is generated in the light beam when the light beam is transmitted through the transparent layer, by controlling an orientation direction of liquid crystal molecules in a liquid crystal layer so as to give a canceling phase difference to the light beam transmitted through the liquid crystal layer; a generating device for generating an indication signal indicative of the birefringence; and a controlling device for controlling the orientation direction on the basis of the indication signal so that a first angle between a standard line, which is perpendicular to an optical axis of the light beam and is set in advance,

Abstract: A recording/reproducing apparatus includes an optical pickup having an objective lens, an actuator for operating the lens, an aberration correction element, and a detector for generating a reading signal; a servo control section; a driver for operating the aberration correction element; a generator for generating a focus disturbance signal and an aberration correction disturbance signal having a period different from that of the focus disturbance signal; and a controller for adjusting the focusing position and the aberration correction amount on the basis of a change in a predetermined characteristic value of the reading signal when the disturbance signals are simultaneously applied.

Abstract: The invention presents an optical element that has a good correcting effect with regard to aberrations and is easy to manufacture, as well as an optical head and an optical recording and reproducing apparatus using the same. The optical element includes a first substrate, a second substrate arranged substantially in parallel to the first substrate, a voltage applying electrode arranged between the first substrate and a liquid crystal, an opposing electrode arranged substantially in parallel to the voltage applying electrode and opposing the voltage applying electrode, and a liquid crystal arranged between the first substrate and the second substrate. By changing the voltage between the voltage applying electrode and the opposing electrode, the phase of the light incident on the liquid crystal can be changed.

Abstract: A holographic recording and/or retrieval method and apparatus are provided. An optical recording medium is used which has a recording layer, formed on a surface of a transparent substrate, through which light having an incident angle of a predetermined value or more with respect to the surface is guided, and which changes a refractive index or absorption coefficient upon simultaneous irradiation of signal light of a predetermined wavelength and reference light, and can record holograms by holding the changed refractive index or absorption coefficient. During recording, a hologram is recorded by simultaneously irradiating the recording layer with signal light of predetermined wavelength and reference light. During retrieval, reading light of wavelength that does not change a refractive index or absorption coefficient of the recording layer is guided through the recording layer, and a hologram is retrieved by diffracted light produced when the reading light is guided through the recording layer.

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: An optical wavefront modifier modifies a wavefront of an optical beam passing through the modifier. The modifier comprises a first and a second transparent electrode layer and a flat medium for modifying the wavefront depending on electrical excitation of the medium and arranged between the electrode layers. The electrode layers are provide the electrical excitation to produce a first wavefront modification of a first order of a radius in the cross-section of the beam in the plane of the medium and simultaneously produce a second wavefront modification of a second order of the radius different from the first order.

Abstract: In order to reproduce signals from a double-layer optical disc having two signal recording surfaces, a focus jump that the focusing of an objective lens from the one signal recording surface to the other signal recording surface is quickly achieved, is necessary. When a focus error signal (FE) from a pickup (60, 70) reaches a predetermined threshold value (Vcomp), a deceleration signal for decelerating the objective lens (42) is supplied to an actuator (47). Preferably, a deceleration pulse voltage is lowered step by step. The deceleration pulse voltage is determined in accordance with the maximum value (DFEmax) of a differential focus error signal (DFE) generated by differentiating the focus error signal (FE). Preferably, the address seeking is done simultaneously with the focus jump. The focus jump is performed in accordance with the layer-to-layer distance which is measured beforehand. The focus jump is performed by using a lens (143) having a controllable focal distance.

Abstract: In order to reproduce signals from a double-layer optical disc having two signal recording surfaces, a focus jump that the focusing of an objective lens from the one signal recording surface to the other signal recording surface is quickly achieved, is necessary. When a focus error signal (FE) from a pickup (60, 70) reaches a predetermined threshold value (Vcomp), a deceleration signal for decelerating the objective lens (42) is supplied to an actuator (47). Preferably, a deceleration pulse voltage is lowered step by step. The deceleration pulse voltage is determined in accordance with the maximum value (DFEmax) of a differential focus error signal (DFE) generated by differentiating the focus error signal (FE). Preferably, the address seeking is done simultaneously with the focus jump. The focus jump is performed in accordance with the layertolayer distance which is measured beforehand. The focus jump is performed by using a lens (143) having a controllable focal distance.

Abstract: In order to reproduce signals from a double-layer optical disc having two signal recording surfaces, a focus jump that the focusing of an objective lens from the one signal recording surface to the other signal recording surface is quickly achieved, is necessary. When a focus error signal (FE) from a pickup (60, 70) reaches a predetermined threshold value (Vcomp), a deceleration signal for decelerating the objective lens (42) is supplied to an actuator (47). Preferably, a deceleration pulse voltage is lowered step by step. The deceleration pulse voltage is determined in accordance with the maximum value (DFEmax) of a differential focus error signal (DFE) generated by differentiating the focus error signal (FE). Preferably, the address seeking is done simultaneously with the focus jump. The focus jump is performed in accordance with the layertolayer distance which is measured beforehand. The focus jump is performed by using a lens (143) having a controllable focal distance.

Abstract: An optical pickup for a recording medium includes a light beam division and detection unit including receiving portions dividing an incident light beam reflected on the recording medium into a first light beam portion and a second light beam portion around the first light beam portion and converting the first and second light beam portions into first and second detection signals, respectively. A thickness variation detection circuit detects a variation in thickness of the recording medium according to the first and second detection signals and outputs a thickness variation signal indicative thereof.

Abstract: An aberration correcting element includes a first electrode layer including a plurality of electrode portions; a second electrode layer opposed to the first electrode layer; and a liquid crystal sandwiched between the first and second electrode layers for producing a phase change corresponding to voltages applied to the first and second electrode layers in a light beam passing therethrough. The first electrode layer includes a plurality of position markers.

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: 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: 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 aberration compensation device includes: a phase difference generator for receiving an input signal and for generating a phase difference used for compensating for an aberration induced in a light beam; a temperature detector for detecting a temperature of the phase difference generator; and a corrector for controlling the input signal to be inputted to the phase difference generator based on the temperature detected by the temperature detector thereby to correct a variation of a characteristic of the phase difference generator resulting from a temperature variation.

Abstract: Disclosed is an optical data recording/reproducing device which is provided with a laser diode for emitting laser beam, an illuminating optical system including an objective lens which converges the laser beam emitted by the laser diode on an optical disc, a monitoring optical system including a light receiving element which receives a part of the laser beam emitted by the laser diode, and a driving circuit which drives the laser diode in accordance with an output signal of the light receiving element. A coupling efficiency of the illuminating optical system and a coupling efficiency of the monitoring optical system are made substantially the same.

Abstract: A switchable liquid crystal diffractive element for use in an optical drive capable of reading multiple tracks of an optical disk simultaneously, and writing or erasing at least one track of the optical disk is disclosed. When the liquid crystal diffractive element is in an “on” state, it splits an incident beam into multiple beams suitable for simultaneously reading multiple tracks of an optical disk. When the liquid crystal diffractive element is in an “off” state, it permits an incident beam to pass through without being split, for writing to an optical disk. Embodiments are disclosed that use multiple electrodes to create switching and non-switching regions of a liquid crystal element to form a switchable phase grating, and that use a single switching liquid crystal element and a non-switching grating, or a birefringent non-switching grating, to form a switchable diffractive element.

Abstract: An optical storage unit which uses a light beam to record information on and/or reproduce information from a recording medium. The recording medium is provided with at least one land and at least one groove, and information is recorded in plural sectors in each of the land(s) and groove(s). The optical storage unit includes an optical phase adjuster for adjusting a phase of a polarization component of the light beam reflected from the recording medium based on a track type determination of a target address. An optical pickup is provided for reproducing information recorded on the recording medium using the phase-adjusted polarization component of the light beam.

Abstract: A liquid crystal driving signal generating apparatus comprises a PWM signal generator, a low pass filter for limiting a frequency band of a PWM signal outputted from the PWM signal generator, a liquid crystal panel connected to an output of the low pass filter, and a control means for controlling the PWM signal generator. The control means controls the PWM signal generator such that the PWM signal generator generates a PWM signal with a duty ratio corresponding to a refractive index to be set in the liquid crystal panel.

Abstract: An optical pick-up device for use in an information recording/reproducing apparatus for recording and/or reproducing information on an optical record medium. The device comprises a semiconductor laser, an information record medium having plural record layers laminated thereon, an outward route system for irradiating laser light from the semiconductor laser onto the information record medium through a beam splitter and objective lens, and an inward route system having a light detector for receiving the light reflected from the information record medium and transmitted through the objective lens, the beam splitter and pin-hole. The pin-hole has a radius, which is decided in such a manner that an expression Vp=2&pgr;r/(&lgr;/NA) satisfies following condition 3≦Vp≧6, wherein r is radius of the pin-hole, NA is lens aperture of the detection system, &lgr; is wave length of the laser light, and Vp is radius of Airy disc.

Abstract: An aberration correcting apparatus for correcting an aberration of beam which is emitted from a light source and focused on an information recording medium by an optical system, the aberration correcting apparatus includes a wave front aberration correcting component aligned in an optical path between the light source and the information recording medium for correcting a wave front aberration of an incident beam by changing a refractive index corresponding to an applied voltage. A detector also detects a tilt-angle of the information recording medium, and a controller for controlling the wave front aberration correcting component corresponding to an output of the detector.

Abstract: A dynamic control diffraction grating for dynamically varying a light amount ratio of a zero-order diffracted beam of light to high-order diffracted beams of light. The dynamic control diffraction grating comprises a voltage-dependent phase varying material for transmitting a beam of light therethrough and varying the phase of the transmitted light beam in response to external voltages applied thereto, the voltages having different levels and being applied to the phase varying material at regular intervals in a comb form.

Abstract: An optical scanning device comprising means for scanning optical record carriers of predetermined different formats, such as CDs and DVDs, using scanning at different numerical apertures provided by an optical diaphragm. The optical diaphragm comprises cholesteric liquid crystal material of one or more selected helical pitches which provide the diaphragm with desired wavelength- and/or polarization-selective characteristics.

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.