Abstract: This optical disc drive can read and/or write data from/on an optical disc 20 with multiple information layers including first and second information layers. The drive includes: a light source 3, 4 that emits the light beam; an objective lens 1; an actuator 2 for moving the objective lens perpendicularly to the information layers; a focus error generator 7 for generating a focus error signal representing how much the light beam has been converged on a target one of the information layers; and focus control means for forming a focal point of the light beam on the target information layer by driving the actuator in accordance with the focus error signal. According to the present invention, while a focus jump is being made to shift the focal point of the light beam from the first information layer of the optical disc 20 to the second information layer thereof by moving the objective lens 1, wavelengths and/or numerical apertures for the light beam are changeable while the objective lens 1 is moving.

Abstract: A reproducing system reproduces data recorded on an optical record carrier. The system includes a light source driver unit that modulates and controls a light output by a light source, such as a laser, in order to read data from an optical record carrier. The system is configured to operate in two modes: a reading mode and a light source lifetime extension mode. During the reading mode, the light source generates a continuous light output while data is read from the optical record carrier. During the light source lifetime extension mode, the light source generates a pulsed light output which may provide continued tracking and focus of the light on the optical record carrier, even when no data is being read from it.

Abstract: In an optical disc drive that needs an aberration correcting element for correcting spherical aberrations, it takes long time to conduct a processing operation of the aberration correcting element in an interlayer movement of a multilayer disc and a drive initializing operation. In order to eliminate the problem, an optical disc drive using a pickup includes a focus actuator for moving an objective lens in a rotation axis direction of a disc, a tracking actuator for moving the objective lens in a radial direction of the disc, an aberration corrector for correcting aberrations, and a feeder for moving the pickup in the disc radial direction. A control operation of the aberration corrector and a control operation of the feeder are conducted in parallel.

Abstract: An optical pickup includes: a first emitting unit to emit an optical beam of a first wavelength; a second emitting unit to emit an optical beam of a second wavelength; a third emitting unit to emit an optical beam of a third wavelength; an object lens to condense optical beams emitted from the first through third emitting units onto a signal recording face of an optical disc; and a diffraction unit provided on one face of an optical element or the object lens positioned on the optical path of the optical beams of the first through third wavelengths; wherein the diffraction unit includes a generally circular first diffraction region provided on the innermost perimeter, a ring zone shaped second diffraction region provided on the outer side of the first diffraction region, and a ring zone shaped third diffraction region provided on the outer side of the second diffraction region.

Abstract: There is provided an assembling method for expanding a maximum admissible astigmatism of objective lens which includes defining a maximum admissible astigmatism for the entire optical system, installing the collimator lens on the optical system to cause a predetermined amount of astigmatism lying within a range of up to the maximum admissible astigmatism by tilting the collimator lens from a condition where a point source of the semiconductor laser lies on an optical axis of the collimator lens, and installing the objective lens on the body case of the optical system to bring a total amount of astigmatism of the entire optical system to a level smaller than or equal to the maximum admissible astigmatism for the entire optical system by rotating the objective lens from a condition where the point source of the semiconductor laser and the center of the collimator lens lie on the optical axis of the objective lens.

Abstract: An optical disc apparatus, which discriminates types of optical discs having different thicknesses of transparent layers by using the same wavelength of laser light, includes an aberration correction unit for correcting spherical aberration, an objective lens for condensing the laser beam onto a recording surface of an optical disc, an actuator for moving the objective lens with respect to the optical disc, a signal detection unit for delivering a focus error signal or a sum light signal, a control unit for controlling the aberration correction unit, the actuator and the signal detection unit.

Abstract: An optical pickup apparatus includes an astigmatic element, an angle adjusting element for contradicting propagation directions of luminous fluxes within four different luminous flux regions out of a reflected light, a polarization adjusting element. Two of the luminous flux regions are placed in a direction in which aligned are a set of opposite angles made by the two mutually crossing straight lines respectively parallel to a first convergence direction and a second convergence direction vertical to the first convergence direction by the astigmatic element, and the remaining two luminous flux regions are placed in a direction in which an alternate set of opposite angles are aligned. The polarization adjusting element differentiates polarization directions of luminous fluxes which are selected out of the luminous fluxes within the four luminous flux regions and which are adjacent in a peripheral direction in which the optical axis of reflected light serves as an axis.

Abstract: An optical disc apparatus includes a laser diode, a first optical component which branches beams from the laser diode into a first beam and a second beam, an objective lens which focuses the first beam on an optical information recording medium, an actuator which drives the objective lens in an optical axis direction, a reference mirror provided in an optical path of the second beam, an optical path length varying unit which varies an optical path length of the second beam, a first photo detector, a second photo detector, a second optical component which branches beams obtained by combining the first beam which is reflected by the optical information recording medium and the second beam which is reflected by the reference mirror and which makes the branched beams incident on the first and second photo detectors, and a signal processing part.

Abstract: A transmitting/reflecting member for transmitting a laser beam of a first wavelength emitted from a first light source includes a first surface on which the laser beam of the first wavelength emitted from the first light source is incident and a second surface which faces the first surface and from which the laser beam of the first wavelength emerges, an angle ? defined between the first and second surfaces satisfies a condition of ??0, and a third-order astigmatism and a third-order coma aberration occurring when the laser beam of the first wavelength passes through the transmitting/reflecting member are both 5 m? or smaller. In this way, good recording performance or reproduction performance for various optical discs can be realized by focusing laser beams having different wavelengths on information recording surfaces of optical discs whose protective substrates differ in thicknesses.

Abstract: An optical pickup device is provided, in which, supposing that an angle formed by the meeting of a straight line connecting a center of an optical disk and an accessing position of an HD objective lens with a diameter L of the optical disk is a track angle ?1, an oscillation angle ? of an optical system including an HD laser, an HD half mirror, and an HD sensor, and a distance z of the HD objective lens are set so as to satisfy ??(?1max+?1min)/2=±45°, where ?1max is the track angle ?1 when the HD objective lens is positioned at an innermost circumference of the optical disk, and ?1min is the track angle ?1 when the HD objective lens is positioned at an outermost circumference of the optical disk.

Abstract: Of the beams reflected by an optical disk, only peripheral beams excluding the push-pull region are used to generate a DPD signal in order to optimize internal wire connections among the light receiving areas of the optical detector and thereby reduce the amplification factor of the lens error signal, required for generating the tracking error signal of the DPP method. A beam reflected from a multilayered optical disk is divided into some beam diffraction areas. The divided beam diffraction areas and the light receiving areas are so arranged that the divided beams focus at different positions on the optical detector and that, when a beam is focused on a target recording layer of the disk, stray light from other than the target recording layer being reproduced does not enter into the servo signal light receiving area of the optical detector.

Abstract: An optical pickup apparatus comprising: a first objective lens; and a second objective lens arranged with the first objective lens in a radial direction of an optical disc, the first objective lens being configured to focus laser light for reproduction, which is laser light for reproducing a signal recorded in a signal recording layer of the optical disc, onto the signal recording layer, the second objective lens being configured to focus laser light for recording, which is laser light for recording a signal, onto the signal recording layer.

Abstract: An objective lens formed of a synthetic resin material having characteristics of substantially not reducing transmittance of the objective lens when a first laser beam having a first wavelength passes through the objective lens, and reducing the transmittance according to an elapsed time to apply a second laser beam when the second laser beam having a second wavelength shorter than the first wavelength and longer than a wavelength of ultraviolet light passes through the objective lens, the objective lens being irradiated with the ultraviolet light in advance for a predetermined time such that a change in the transmittance for the second laser beam is set within a predetermined range.

Abstract: A method for detecting head-disc contact is disclosed. The method comprises locating a head including a head positioning microactuator and at least one of a read transducer and a write transducer adjacent to a disc such that the head is in communication with the disc, monitoring an output signal from the head positioning microactuator of the head, and evaluating the output signal to determine if the head contacts the disc.

Abstract: A first phase structure corrects at least one of a spherical aberration due to a difference between a protective substrate thickness t1 and a protective substrate thickness t2 and a spherical aberration due to a difference between a first wavelength ?1 and a second wavelength ?2, and a second phase structure corrects at least one of a spherical aberration generated when the first wavelength ?1 is changed in a range of ±10 nm, a best image point movement generated when the first wavelength ?1 is changed in a range of ±10 nm, and a spherical aberration generated when environmental temperature is changed.

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: In an optical pickup device including light sources for emitting laser light, an objective lens for collecting the laser light emitted from the light sources on a disc surface of an optical disc, a light receiving unit for receiving the reflected light reflected by the disc surface, a collimator lens for correcting spherical aberration of the exit light from the objective lens, a lens driving unit for moving the collimator lens in an optical axis direction, and a control unit for controlling the operation of the lens driving unit based on the output of the light receiving unit, the astigmatism of the exit light from the objective lens is corrected by tilting the collimator lens by a predetermined angle by the lens driving unit.

Abstract: The invention relates to an optical scanning device for scanning at least one information layer (101, 102) in an information carrier (10), comprising means (1) for generating a radiation beam (11) intended to be focused on the information layer (101, 102). A spherical aberration (SA) compensation module (40) is arranged in the light path of the radiation beam (11) and comprises a SA compensation means (41) and a reflective means (42) for folding the light path of the radiation beam (11).

Abstract: An optical disk apparatus according to the present invention includes: a light emission section for emitting laser light; an optical system for irradiating the optical disk medium with the laser light; and an aberration control section for controlling aberration of the laser light. In one embodiment, the aberration control section repeatedly switches between a plurality of aberration setting states in a focus lock-in operation. In another embodiment, the aberration control section simultaneously sets a plurality of aberration setting states in a focus lock-in operation. As a result, a plurality of aberration setting states can be allowed to substantially coexist within a single optical system.

Abstract: In a photo pickup device, an incident area 30 for a reflection light of a light spot is divided into four areas 30a˜30d by parting lines 31, 32 making axial-symmetrical angles with a direction Y of a projected track on an optical disc. In these areas, the so-divided areas 30a, 30c are formed so as to diffract the light in one or more directions in a range of 90 degrees±20 degrees to the direction Y and impress misalignment on each diffraction light. In each diffraction light, two focal lines produced due to the astigmatism make approx. 45 degrees with the direction Y of the projected track. Further, the divided areas 30b, 30d are characterized by diffracting the light in one or more directions in a range of 90 degrees±20 degrees to the direction Y.

Abstract: The invention relates to an optical disk drive. The optical disk drive has an objective lens to be driven by a focus actuator with a focus offset for focusing an incident beam onto an optical disk into a spot with a spherical aberration, and a processor to derive a first and a second characteristic from a sensor output signal and obtain a spherical aberration correction value (SA) from a pre-determined function, the pre-determined function defining a spherical aberration correction value in dependence on a focus offset difference value (?FO). The focus offset difference value (?FO) is determined from a difference between a second optimal focus offset at which the second characteristic is optimal and a first optimal focus offset at which the first characteristic is optimal. The spherical aberration correction value (SA) can be used to achieve a correction to the spherical aberration of the spot.

Abstract: An optical pickup includes: a light source; an objective lens; a beam splitter; a quarter wave plate that transforms the optical beam into a circularly polarized optical beam and also transforms the circularly polarized reflection optical beam into an optical beam whose polarization direction is perpendicular to the optical beam; a light detector; a neutral density filter section placed on a mutual optical path of those beams, reducing the intensity of the optical beam while maintaining the intensity of the reflection optical beam; and a filter drive section that puts the neutral density filter section in the mutual optical path or outside of it, wherein the intensity of the optical beam and the filter drive section are controlled such that the amount of the optical beam emitted to the optical disc is maintained at a predetermined level.

Abstract: A pickup lens with a phase compensator is composed of a condenser lens and a phase compensator. At least one surface of the condenser lens has a step-like annular zone structure to compensate wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of t1 with a laser beam having a wavelength ?1 and wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of t2 with a laser beam having a wavelength ?2. The phase compensator compensates wavefront aberration generated when recording and reproducing data on an information recording medium having a substrate thickness of t3 with a laser beam having a wavelength ?3.

Abstract: A compensation value setting device selects, based on the first and second index values calculated by the first and second index value calculation sections for each combination of the spherical aberration compensation value and the lens' position compensation value, one combination of the spherical aberration compensation value and the lens' position compensation value and then sets the selected combination for correcting the spherical aberration and the position of the objective lens.

Abstract: An optical pickup includes a light emitting device, a prism, and an objective lens. The light emitting device emits a laser beam. The prism has an entrance face and an exit face. In the prism, the laser beam emitted from the light emitting device is perpendicularly incident on the entrance face, is parallel-shifted, is perpendicularly reflected, and is emerged from the exit face. The objective lens focuses the laser beam emerged from the prism on a recording surface of an optical disk.

Abstract: An optical information recording and reproducing apparatus for performing, using a light beam, recording of information or reproducing of recorded information with respect to a plurality of recording layers of an information recording medium. An objective lens condenses a light beam onto the recording layers. A light beam expander corrects spherical aberration caused by a difference in substrate thickness by changing one of a divergent angle and a convergent angle of a light beam entering the objective lens. A coma aberration correcting device corrects coma aberration caused by tilt of the recording medium.

Abstract: An initialization apparatus that has a simplified configuration and that forms an initial hologram in an information recording medium is provided. An initialization apparatus (10) rotates an optical disk (100) and emits blue light beams (Lb1) and (Lb2) to either side of the optical disk (100) while causing a red light beam (Lr1) to follow a track formed in a reference layer (102). Thus, the initialization apparatus (10) can perform an initialization process in which a linear initial hologram IH is formed in a recording layer (101) in a spiral pattern that corresponds to the track formed in a reference layer (102). Accordingly, the initialization apparatus (10) can form a planar initial hologram layer (YH) with significantly reduced optical energy or thermal energy emitted to the optical disk (100) at one time.

Abstract: An optical head includes a first laser diode configured to generate a laser beam with a wave length of ?1, a second laser diode configured to generate a laser beam with a shorter wave length of ?2 than the wave length ?1, a collimator lens arranged so that the laser beams are incident on it, an aperture filter arranged on an optical axis of the collimator lens, and an object lens 0 arranged on the optical axis so that the laser beams passing through the aperture filter are incident on it, wherein the second laser diode is arranged at a position on the optical axis further away from collimator lens than the first laser diode is away from the collimator lens.

Abstract: An optical pickup apparatus and an optical recording/reproducing system including the same, the optical pickup apparatus includes at least two optical systems for different types of optical recording media, one of objective lenses of the optical systems being offset from a central line of the optical recording medium, wherein the optical system including the offset objective lens having a diffraction grating diffracting light emitted from a light source to form a main beam and sub-beams, wherein the diffraction grating includes first and second diffraction regions having different grating patterns arranged alternately thereon, and a center of each sub-beam is arranged at a boundary of the first and second diffraction regions of the diffraction grating, and a center of the diffraction grating and an optical axis of the light source are adjusted to be coincided with each other, preventing generation of an alternating current in a Push-Pull signal of the sub-beams.

Abstract: This invention provides a technique which ensures that if a recording error occurs in an optical disc, recorded data will be immediately erased from the disc without leaking to third parties. While recording data onto the optical disc, a controller judges whether the recording process has been executed to completion properly. If the recording process is judged to have failed, the controller will stop the recording process and activate an optical pickup to erase recorded data from the data-recording area on the optical disc by overwriting this area with required erasing data.

Abstract: An aberration detection device of the present invention is such that an absolute value of detection sensitivity of an aberration error signal is increased, and variation in detection sensitivity of the aberration error signal is little even when displacement between the center of light beam dividing means and the center of a bundle of light beams occurs due to a shift of a condensing optical system at the time of tracking control. A hologram element (2) divides light beams reflected from an information storage medium into at least two positive first order diffracted light beams. The hologram element (2) has a line (D1) extending in a radial direction and passing through an optical axis (OZ) and a division line (D2) having segments at least both ends thereof and a bulge in a center thereof, wherein the segments are substantially parallel to the line (D1), and the bulge (44) bulges toward the periphery of the hologram element (2) so that a top (D5) of the bulge (44) is substantially parallel to the line (D1).

Abstract: An objective lens for an optical pick-up which is used to record data to and/or to reproduce data from at least three types of optical discs by selectively using one of at least three light beams having different wavelengths is provided. When thicknesses of a first, second and optical discs are represented by t1, t2 and t3, respectively, a relationship t1?t2<t3 is satisfied. When numerical apertures required for the first, second and third optical discs are represented by NA1, NA2 and NA3, respectively, a relationship NA1?NA2>NA3 is satisfied. The first, second and third light beams are incident on the objective lens as substantially collimated light beams, respectively. In this configuration, at least one of surfaces of the objective lens includes a first area for attaining the numerical aperture required for recording data to and/or reproducing data from the third optical disc, and a second area located outside the first area.

Abstract: An optical pickup device has a first light source and a second light source each adapted for outputting a laser beam of a predetermined wavelength, a photodetector for detecting an intensity of the laser beam outputted from the first light source or the second light source to control the power of the laser beam to be outputted from the first light source or the second light source, a wideband quarter wavelength plate for converting the laser beam outputted from the first light source or the second light source into a circularly polarized laser beam, and a first rise-up mirror and a second rise-up mirror for guiding a P-polarized component in the laser beam converted by the wideband quarter wavelength plate to the photodetector, and guiding an S-polarized component in the laser beam different from the P-polarized component to an optical recording medium.

Abstract: A transmissive or reflective diffractive optical element, comprising: a substrate having a top surface, the top surface being etched into a pattern, the pattern including a periodic surface pattern of grooves formed such that when an incoming light beam is shone onto the top surface, the incoming light beam will be split into a plurality of diffracted light beams, the plurality of diffracted light beams including a plurality of primary diffracted order beams and a plurality of secondary diffracted order beams, wherein the primary diffracted order beams have a primary aggregate efficiency above ninety percent, wherein the plurality of secondary diffracted order beams have a secondary aggregate efficiency of lower than ten percent, and wherein a maximum power of the primary diffracted order beams and a minimum power of the primary diffracted order beams differ by at least ten percent of an average power of the primary diffracted order beams.

Abstract: A light flux from the first light source forms a converged spot on first optical information recording medium by only a refraction action of the aspheric surface, or by a combination of the refraction action and an optical action given by at least one of the first phase structure and the second phase structure, a light flux from the second light source forms a converged spot on second optical recording medium by a combination of a refraction action of the aspheric surface and an optical action given by at least one of the first phase structure and the second phase structure, and a light flux from the third light source forms a converged spot on third optical recording medium by a combination of a refraction action of the aspheric surface and an optical action given by at least one of the first phase structure and the second phase structure.

Abstract: The present invention provides an afocal lens for an optical head that can ensure WD while satisfying NA, the optical head, an optical disk apparatus, a computer, an optical disk player, and an optical disk recorder. Using a blue-violet laser beam source with wavelength of about 400 nm, and in an optical head compatible to optical disks having different protective substrate thickness, an afocal lens that expands a diameter of light flux of light from a collimating lens and emits the light as substantially parallel light to an objective lens is provided between the collimating lens and the objective lens. The configuration makes it possible to ensure WD while satisfying NA.

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 pickup device includes light sources for respectively emitting a plurality of different wavelengths of light, a unit structured for causing at least a part of the light emitted from the light sources to pass a same optical path; and a focusing unit for focusing the light. The focusing unit includes at least first and second focusing parts, the first focusing part being to focus mainly a wavelength of light different from a wavelength of light to be mainly focused by the second focusing part. The optical pickup device and optical disk device are capable of realizing at least one of thickness reduction, size reduction and suppression against characteristic deterioration even where coping with various wavelengths of laser including a blue laser.

Abstract: An optical pickup apparatus is provided for recording and/or reproducing information on an optical disc in which information can be recorded at recording positions. The optical pickup apparatus includes: a light source; a relay optical system; an objective lens for converging a light flux onto one of the plurality of recording positions; a photodetector for receiving a light flux from the optical disc; a detector; a first actuator; and a second actuator. The detector is provided for detecting information for keeping a distance between the optical disc and the objective lens a predetermined value. The first actuator is provided for driving the objective lens for keeping the distance between the optical disc and the objective lens the predetermined value. The second actuator is provided for driving the relay optical system corresponding to one of the plurality of recording positions where information is recorded and/or reproduced.

Abstract: A half-wave plate is attached to a lens holder holding a collimator lens, and a servo operation to the collimator lens and insertion and retraction of the half-wave plate in and from an optical path of a laser beam are performed by a common actuator. When the lens holder is moved to a servo position, the half-wave plate is inserted in and retracted from the optical path of the laser beam. Therefore, the laser beam is formed in S-polarized light or P-polarized light with respect to a polarization beam splitter, and the laser beam is guided to a first objective lens or a second objective lens.

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: There is provided an optical information recording/reproducing apparatus including a unit for detecting the focus error signal from the reflected light flux from a recording layer of an optical recording medium, and a unit for focusing the light flux on the recording layer of the optical disk on the basis of the focus error signal. In the case of detecting the focus error signal, the light flux of the effective numeric aperture NAeff<1 due to an objective lens and the SIL within a pupil is obtained by a splitting device as the focus error signal, whereby it is possible to suppress the reflected light from the bottom surface of the SIL from being mixed into the focus error signal as a noise.

Abstract: An optical pickup device includes: a light source; an objective lens which condenses a light beam that is emitted from the light source on a recording layer of an optical recording medium; and a photo detector which receives reflected light that is reflected by the optical recording medium. Further on an optical path between the light source and the objective lens, a liquid lens which performs correction of spherical aberration by changing state of convergence or divergence of the input light beam and a liquid crystal element on which a plurality of phase shift regions are formed to adjust phase of the input light beam, and which performs correction of the spherical aberration by phase adjustment of the phase shift regions are arranged.

Abstract: A laser beam 32 reflected by an information layer of a multilayer optical disc 26 is reflected and split by reflecting surfaces 31a?, 31b, 31c and 31d to be incident on a photodetector element 36 as laser beams 33, 34 and 35. The laser beam 34 is collected on a light receiving region 38 for RF detection to generate an RF signal. The laser beams 33, 35 are incident on light receiving regions 37a, 37b for focus detection, and a focus error signal is generated by an SSD method. A laser beam 65 reflected by an information layer adjacent to the above information layer partially transmits through the reflecting surface 31a? to be imaged on a light receiving region 66 for tracking detection, and a tracking error signal is generated.

Abstract: An optical information recording-reproducing apparatus comprising a light source, an objective lens for condensing a light beam from the light source on a recording layer of an optical recording medium, a divergence angle-converting element provided in an optical path from the light source to the optical recoding medium for converting a divergence angle of the light beam to be introduced to the objective lens, a focus error detecting optical system including a photodetector for detecting a focus error of the light beam, an optical element for introducing a part of the light beam emitted from the divergence angle-converting element to the focus error detecting optical system, a circuit for detecting the divergence angle of the light beam emitted from the divergence angle-converting element from output from the photodetector, and a circuit for compensating spherical aberration in the recording layer of the optical recording medium by driving the divergence angle-converting element in accordance with the detecti

Abstract: Light emitted from a light source and having a wavelength of 400 nm is reflected by a beam splitter (BS), and converged on a disk according to a next-generation standard. Reflection light therefrom passes through the BS and is received by a photodetector. Light emitted from a light source and having a wavelength of 660 nm is reflected by the BS and passes through the BS, and converged on a disk according to a DVD standard. Reflection light therefrom passes through the BS and is received by the photodetector. About 50% of light emitted from a light source and having a wavelength of 780 nm is reflected by the BS. The light passes through the BS and is then converged on a disk according to a CD standard. Reflection light therefrom passes through the BS. About 50% of the light passes through the BS and is received by the photodetector. Thus, recording and reproduction can be performed on any of disks according to a next-generation standard, DVD standard, and CD standard.

Abstract: A very small spot-size light beam forming apparatus of the present invention comprises: a conductive film for generating a surface plasmon when an inputted light is applied thereto: a plurality of nano projections, each connected to the conductive film at one end, for receiving a portion of the surface plasmon, and outputting a plurality of input surface plasmons, respectively, from the other end of each of the plurality of nano projections, the other end of each of the plurality of nano projections having a diameter smaller than a wavelength of the inputted light; a coupling unit, connected to the other end of each of the plurality of nano projections, for receiving and coupling the plurality of input surface plasmons, so as to generate a coupled surface plasmon; and a negative-refractive-index lens, connected to the coupling unit and having a negative refractive index, for receiving a near-field light generated due to the coupled surface plasmon, and collecting the near-field light on a recording surface of

Abstract: Fifth order spherical aberration in addition to third order spherical aberration for an optical information recording medium of which thickness of a light transmission layer changes greatly is corrected. An objective lens collects a laser beam emitted from a semiconductor laser on an optical information recording medium. A spherical aberration correcting portion corrects spherical aberration generated according to a thickness of the light transmission layer of the optical information recording medium, in which the spherical aberration correcting portion includes a collimator lens, a lens holder and a stepping motor for correcting the third order spherical aberration and a liquid crystal element and an applied voltage control portion for correcting the fifth order spherical aberration.

Abstract: An optical disc apparatus for recording, reproducing or erasing an information signal by converging a light flux onto a recording layer through a transparent substrate. The apparatus includes one or a plurality of optical heads having a plurality of objective lenses whose aberrations have respectively been corrected for a plurality of disc substrates of different thicknesses, a cartridge for enclosing the optical disc, a discrimination hole which is formed on the cartridge, and a sensor for detecting the opening/closing state of the discrimination hole and for generating a discrimination signal. In accordance with the result of the discrimination as to the thickness of the loaded optical disc, the objective lens, in which the occurrence of the aberration is smallest, is used, so that the information signal can preferably be recorded, reproduced or erased onto/from the optical discs having different substrate thicknesses.

Abstract: An optical disc apparatus for recording, reproducing or erasing an information signal by converging a light flux onto a recording layer through a transparent substrate. The apparatus includes one or a plurality of optical heads having a plurality of objective lenses whose aberrations have respectively been corrected for a plurality of disc substrates of different thicknesses, a cartridge for enclosing the optical disc, a discrimination hole which is formed on the cartridge, and a sensor for detecting the opening/closing state of the discrimination hole and for generating a discrimination signal. In accordance with the result of the discrimination as to the thickness of the loaded optical disc, the objective lens, in which the occurrence of the aberration is smallest, is used, so that the information signal can preferably be recorded, reproduced or erased onto/from the optical discs having different substrate thicknesses.