Abstract: Apparatus for simultaneously recording and reading information on a medium moveable in forward and reverse directions includes a first record laser and means for establishing a first beam path for recording information on the moveable medium and a second read laser and at least a first and second read-out detector respectively associated with the forward and reversed directions of the recording medium and means for establishing two beam paths which direct the laser light to positions forward and rearward from where the first laser beam illuminates the medium and such read laser beams are reflected respectively to the first and second detectors. The apparatus further includes means to select either the first or the second read-out detectors and to process information read by such selected detector so that as the medium is moving in the forward direction, the data are read from the first detector and when the medium is moving in the reverse direction. the data are read from the second detector.

Abstract: An optical pickup apparatus including first and second light sources emitting first and second light beams, respectively, each light beam including different wavelengths; first and second optical path converters changing optical paths of the first and second light beams, respectively; an objective lens, arranged next to the first and second optical path converters, focusing a divergent light beam from one of the first and second optical path converters on one of a relatively thin disc and a relatively thick disc; and a photodetector receiving the divergent light beam from the first and second optical path converters after being reflected by the optical recording medium, wherein the optical pickup is exclusive of a collimating lens.

Abstract: In an optical head device for recording/reproducing information on/from an optical recording medium, at least one laser light source emits a laser light beam provided with a first polarized light component and a second polarized light component which are perpendicular to each other. A plurality of optical elements transmit a return light beam reflected by the optical recording medium passes to the light receiving element. A transmission efficiency for the first polarized light component and a transmission efficiency for the second polarized light component in each optical element is made different. A total transmission efficiency for the first polarized light component and a total transmission efficiency for the second polarized light component, which are defined by the respective transmission efficiencies of all the optical elements, are made substantially identical.

Abstract: The present invention has for its object to provide a compact and simplified optical pickup device which secures sufficient quantity of converged light required for recording and reproducing onto/from respective optical disks, can obtain required imaging magnification of respective optical systems, and does not generate performance degradation at lens shift, when recording or reproduction is performed onto/from optical disks with different base material thickness by plural optical systems of a single optical pickup device.

Abstract: An optical pickup apparatus has a simplified configuration for using a plurality of laser beams at different wavelength to reduce the size, and a laser diode chip for use therewith. An irradiation light path for leading a laser beam emitted from a light emitter to a recording medium is provided with an optical axis correcting element for passing a first laser beam and for diffracting a second laser beam having a wavelength different from that of the first laser beam to generate diffracted light which has the optical axis substantially matching the optical axis of the first laser beam. The optical axis correcting element is arranged at a position at which the center of a light intensity distribution of the first laser beam incident thereto matches the center of a light intensity distribution of the second laser beam incident thereto.

Abstract: An optical pickup unit includes first and second light sources of first and second wavelengths, respectively, a dichroic element, a phase plate, and an objective lens. One of the first and second light sources is selected so that information recording or reproduction is performed by converging a light beam emitted from the selected one of the first and second light sources on an optical recording medium via the dichroic element, the phase plate, and the objective lens.

Abstract: Light from a light source is applied to a diffraction grating via a collimator lens. The light diffracted by the diffraction grating is applied to a polarization beam splitter. The light polarized by the polarization beam splitter at a given polarizing plane is transmitted and is applied to a recording surface of an optical disc via a ¼-wave plate and an objective lens. The light reflected from the recording surface of the optical disc is applied to the polarization beam splitter via the objective lens and the ¼-wave plate and is reflected by the polarization beam splitter toward a focusing lens. The light incident to the focusing lens is thereby condensed and is applied to a holographic element which diffracts the light and disposes the focal points of the ±1 diffraction orders to be offset from each other along the optical axis of the zeroth diffraction order with the focal point of the zeroth diffraction order being between the focal points of the ±1 diffraction orders.

Abstract: An optical pick-up apparatus which can adaptively compensate for the aberration of a light beam. The optical pick-up apparatus employees a first light source for generating a first light beam having a first wavelength to be irradiated on a first type of disk and a second light source for generating a second light beam having a second wavelength to be irradiated on a second type of disk. A light path enables the first light beam from the first light source to be irradiated on the disk in the shape of a spot by a finite optical system. The light path allows the second light beam from the second light source to be irradiated on the disk in the shape of a spot by an infinite optical system.

Abstract: An optical pickup of this invention includes a first laser beam source having a wave length of 780 nm and a second laser beam source having a second wave length of 650 nm wherein the first laser beam source and the second laser beam source are disposed in the vicinity of each other, emission lights from the first laser beam source and the second laser beam source are emitted along substantially the same optical axis and a reflected light from the information recording medium is returned along the optical axis; the first diffraction grating, the second diffraction grating and the light receiving device substrate are disposed in order, the first diffraction grating is substantially transparent for a wave length of 780 nm and diffracts a wave length of 650 nm, and the second diffraction grating is substantially transparent for a wave length of 650 nm while it diffracts a wave length of 780 nm.

Abstract: An optical pickup can be provided, the optical pickup being capable of recording and playback of a plurality of optical disks having different specs by using light beams of different wavelengths, and further being suitable for integrating the semiconductor lasers and light receiving elements into a single package, by including: first and second semiconductor lasers adjacently disposed; a three-beam diffraction grating for generating three beams for tracking control; a second hologram element for diffracting light of the second semiconductor laser to guide it to a photosensor; a complex polarization beam splitter (PBS) for reflecting only light from the first semiconductor laser; and a first hologram element for diffracting light of the first semiconductor laser to guide it to the photosensor.

Abstract: This invention provides a multi-layer information medium wherein layer-specific information unique to the particular layer has been adequately recorded, and delay in the access to the recorded data associated with reading of the layer-specific information is suppressed. Such multi-layer information medium is also provided at low cost. The optical information medium has at least two information-storing layers each storing recorded information and/or tracking servo information, and at least one of the information-storing layers is a data layer storing recorded information, and at least one of said information-storing layers is recorded or read by the recording beam or the reading beam which has passed through other information-storing layer(s), and in this medium, the data layer has layer-specific information unique to the particular data layer recorded therein.

Abstract: An optical pickup includes an aberration correction element to correct chromatic aberration caused by variation of power from a light source when changing between operating modes in a recording medium. The aberration correction includes a first retardation member, which includes a stepped convex pattern with a plurality of steps at one side, and a second retardation member combined with the first retardation member. The second retardation member includes a stepped concave pattern with a plurality of steps at one side facing the first retardation member, the stepped concave pattern corresponding to the stepped convex pattern. The first and the second retardation members include different refractive indices for a light beam, which allows the first and the second retardation members to selectively create a phase difference of an incident light beam according to a polarization of the incident light beam.

Abstract: An optical information disk with an excellent mechanical precision is provided. Also provided is a multi-layer optical disk having a plurality of data layers wherein every data layer exhibits sufficient properties in reading. In addition, such multi-layer optical disk is provided at a low cost. The optical information comprises a disk-shaped substrate or a pair of disk-shaped substrates, and at least one annular data layer for storing at least recorded information and at least one annular resin layer disposed on said disk-shaped substrate or between said pair of disk-shaped substrates. In this medium, at least one of the substrate(s) has a configuration such that its surface facing toward the data layer is convex, and at least one of said resin layer(s) is formed such that it is thicker near its outer periphery compared to the region near its inner periphery.

Abstract: An optical recording medium having a laminated structure portion (4) including a light-emission layer (3) and a recording layer (2). The light-emission layer (3) is made of a light-emission material excited by reproducing laser light to emit fluorescent light, and the recording layer (2) is made of a material in which at least a refractive index or an absorption coefficient can be changed relative to light emitted from the light-emission layer by recording laser light. The recording layer (2) is disposed to be closer to a side into which reproducing laser light is introduced than the light-emission layer (3). Then, recorded information recorded on the recording layer by the change of the refractive index or the absorption coefficient is read out from the recording layer as the change of intensity of light emitted from the light-emission layer (3) when it is irradiated with reproducing laser light.

Abstract: An optical head comprises a photodetector 8 having divided photosensitive areas to detect light 13 reflected from an optical disk 7, means 10, 11, 12 for obtaining tracking error signal by operating signals from the photosensitive areas. The photodetector 8 has a first division line 9a parallel to an information track on the optical disk and second and third division lines 9b, 9c perpendicular to the first division line 9f and symmetrical to the optical axis. Further, a light-shielding area 8i is provided for shielding a part of the reflected light between the division lines 9b and 9c. The signals are operated to reduce offset of the tracking error signal due to a shift of object lens and a tilt of the optical disk. Accordingly, the optical head of the present invention has a small offset of tracking error signal with a simple structure.

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 &pgr; 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 polarizing beam splitter for separating an upstream beam from a downstream beam according to the polarization of an incident beam is provided between first and second light sources emitting laser beams at respective wavelength and an objective lens. A phase plate for providing a phase difference to a beam incident on the polarizing beam splitter is provided between the polarizing beam splitter and the light sources. A portion of the laser beam incident on the polarizing beam splitter is reflected by the polarizing beam splitter and caused to be incident on a photo-detecting unit, so as to prevent an unnecessary portion of the laser beam is incident on the photo-detecting unit. According to the invention, the laser beam is used efficiently and the cost of fabricating an optical disk apparatus is reduced by eliminating a need for a gain controlling circuit in the photo-detecting unit.

Abstract: An optical pickup device that is able to record/reproduce information signals for first and second optical discs with different recording capacities. The optical pickup device includes an objective lens for converging first and second light beams of different wavelengths on the signal recording layers of first and second optical discs having different substrate thicknesses, a beam splitter having the same transmittance to the first and second light beams and configured for separating the first and second light beams radiated by first and second light sources to fall on the beam splitter via a first objective lens or a second objective lens, and a hologram element arranged between the objective lens and the beam splitter for limiting the aperture of one of the first light beam an the second light beam and for correcting the spherical aberration caused by difference in the disc substrate thickness of the first and second optical discs.

Abstract: An optical recording/pickup head compatible with a CD-R and a DVD transfers a first light beam of 650 nm wavelength for a DVD and a second light beam having a wavelength of 780 nm for a CD-R, which are respectively emitted from a first light source and a second light source, to an objective lens using first and second beam splitters having polarized light beam splitting characteristics which are varied according to a wavelength. The objective lens focuses the transferred first and second light beams on the information recording surfaces of the DVD and a CD-R, respectively. The first and second light beams reflected from the information recording surfaces of the DVD and the CD-R, respectively, are transferred to first and second photodetectors by the first and second beam splitters, respectively. The first and second photodetectors detect information from the first and second light beams incident from the first and second beam splitters, respectively.

Abstract: An optical pickup compatible with optical discs having different formats. A first light source emits a first light beam suitable for a first format optical disc. An objective lens is optimized for a wavelength of the first light source. Light reflected from the first optical disc provides a reproduction signal. A second light source emits a second light beam suitable for a second format optical disc. A light splitter splits the second light beam and the objective lens focuses the split beams onto the second disc as a main light spot and a sub-light spot. Lights reflected from the main light spot and the sub-light spot are independently detected and then processed to correct for chromatic aberration caused by a difference in the wavelengths of the first and second light beams and/or spherical aberration caused by thickness difference between the first and second format optical discs.

Abstract: A bifocal optical pickup head is disclosed for use in a optical pickup apparatus having a single objective lens, for generating two different focuses (bifocus) to access a compact disc (CD) and a digital versatile disc (DVD), which the thickness is different. When a beam passes through an optical element disclosed in the present invention, numerical aperture is controlled and spherical aberration is reduced by the optical element due to variations in optical path and radius. Therefore, after beams having different numerical apertures are focused by an objective lens, various focuses can be obtained.

Abstract: An optical data storage system 100 utilizes optical fibers 102 for transfer of information to and from storage media 107. The storage media 107 comprises magneto-optical storage disks. The optical fibers 102 are low-birefringence optical fibers. As compared to the prior art, a polarization state conveyed by the optical fiber 102 is accurately reproduced with reduced noise.

Abstract: An optical information detecting apparatus includes a first optical system focusing an optical beam on a recording surface of a recording medium and a second optical system directing a reflection optical beam produced as a result of reflection of the optical beam by a recording surface of the recording medium to a photodetection unit, wherein the second optical system including a beam dividing element disposed so as to intercept the reflection optical beam and divide the reflection beam into a plurality of optical beam elements traveling generally parallel with each other in the reflection optical beam, such that the plurality of optical beam elements reach the photodetection unit along respective optical paths.

Abstract: An improved focus error signal generator device and an optical data delivery and detection system including an optical lens disposed in the path of a return read beam and a birefringent plate disposed in the path of the return beam of light after the optical lens, wherein the birefringent plate provides for a first and second focal plane of corresponding first and second polarization. A pinhole is disposed in the path of the return read beam after the birefringent plate and in close proximity to first and second focal planes. A polarizing beam splitter is positioned after the second focal plane and serves to split the return read beam into two light beams of first and second polarization. First and second detectors are disposed in the path of corresponding first and second polarization light beams. The detectors are connected to the inputs of an electrical differencing circuit that has an output to an optical head servo system.

Abstract: There is provided an optical head including a laser diode chip, a lens for focusing lights onto an object, an optical separator for separating lights reflected from the object, from an optical axis of a light directing towards the lens from the laser diode chip, and a photodiode chip receiving lights having been separated from the optical axis by the optical separator. The optical separator is defined by first and second sidewalls, and first to fourth outer surfaces, and has first and second inner planes both being inclined relative to the first outer surface. A light enters the first outer surface, passes through the first and second inner planes, leaves the optical separator at the third outer surface, and is focused onto the object by the lens. The light having been reflected by the object enters the third outer surface, and is reflected at the second inner plane by the remaining half.

Abstract: A polarizing beam splitter for separating an upstream beam from a downstream beam according to the polarization of an incident beam is provided between first and second light sources emitting laser beams at respective wavelength and an objective lens. A phase plate for providing a phase difference to a beam incident on the polarizing beam splitter is provided between the polarizing beam splitter and the light sources. A portion of the laser beam incident on the polarizing beam splitter is reflected by the polarizing beam splitter and caused to be incident on a photo-detecting unit, so as to prevent an unnecessary portion of the laser beam is incident on the photo-detecting unit. According to the invention, the laser beam is used efficiently and the cost of fabricating an optical disk apparatus is reduced by eliminating a need for a gain controlling circuit in the photo-detecting unit.

Abstract: An improved focus error signal generator device including two optical lenses in series; a birefringent optical lens followed by a standard optical lens, the lenses being disposed in the path of a return read beam wherein the birefringent optical lens has a first and second focal plane. A pinhole is disposed in the path of the return read beam in close proximity to the first and second focal planes. A polarizing beam splitter is positioned after the second focal plane and serves to split the return read beam into two light beams of polarization associated with the first and second focal planes. First and second detectors are positioned so as to read the two light beams signals output from the polarizing beam splitter and the detectors are connected to an electrical differencing circuit having an output to an optical head servo system.

Abstract: A focus error signal generator device and an optical data delivery and detection system including an optical lens disposed in the path of a return read light beam, and first and second polarizers of corresponding first and second polarizations having corresponding first and second pinholes formed therein wherein the polarizers are spaced apart, disposed in the path of the read light beam after the optical lens. A polarizing beam splitter is disposed in the path of the read light beam after the second polarizer and serves to split the read light beam into a first light beam of first polarization and a second light beam of second polarization. First and second light beams are received by corresponding first and second optical detectors and an electrical differencing circuit having inputs to the first and second detectors and an output to an optical head servo system.

Abstract: An optical system of an optical pick-up device 1 comprises a half mirror 13 and a prism 14 which serve to guide a first laser beam L1 for a CD and a second laser beam L2 for a DVD to the optical recording medium side and a common light receiving element 19. The half mirror 13 is set to have a ratio of a reflectance to a transmittance of 5:1 in the first laser beam L1 to be a P polarized light and the prism 14 is set to have a ratio of a reflectance to a transmittance of 1:3 in the first laser beam L2 having a P polarization component and an S polarization component mixed. The first laser beam for a CD can be guided to the optical recording medium without a light quantity loss. At the same time, a return light Lr can be sent in a sufficient light quantity back to the light receiving element 19 for servo signal generation. Therefore, it is possible to implement a reliable CD recording operation by using the first laser beam.