Ricoh Company, Ltd.

Shigeru Ohuchida

Hideo Maeda

Toshiyuki Inokuchi

Kazuhiro Fujita

Nobuyuki Baba

Junichi Kitabayashi

Hiroyoshi Funato

Hideaki Hirai

Eiji Noda

Yuji Sumi

An optical pickup unit includes first and second light sources of first and second wavelengths, respectively, a diachronic 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 diachronic element, the phase plate, and the objective lens.

Optical element, optical pickup unit, and optical disk drive unit

An optical pickup apparatus for reading/reproducing data on an optical recording medium, includes a plurality of laser diodes configured to emit laser light of different wavelengths respectively, a photodetection device configured to detect each laser light, a diffraction type-optical device configured to transmit each laser light from the plurality of laser diodes to the optical recording medium, and to diffract the light reflected from the optical recording medium to the photodetection device, and wherein the diffraction type-optical device includes a plurality of reflecting type-diffraction elements configured to reflect and diffract each laser light of a corresponding wavelength in the laser light from the plurality of light diodes, to the photodetection device so that the photodetection device can detect each laser light of the corresponding wavelength for monitoring each of the laser light, and a suppression setting device configured to set each of the plurality of reflecting type-diffraction elements to suppress laser light other than the laser light of the corresponding wavelength to the photodetection device.

Optical pickup apparatus and optical pickup method

In an optical pickup apparatus of the present invention, either a first laser diode emits a laser beam having a first wavelength or a second laser diode emits a laser beam having a second wavelength. An optical system focuses one of the two laser beams onto a recording surface of an optical recording medium. A photodetector unit receives reflection beams, which are reflected from the recording medium, to generate detection signals from the received reflection beams. A holographic unit has a first hologram suited to the first laser diode and a second hologram suited to the second laser diode, the first hologram provided to diffract a reflection beam of the laser beam of the first laser diode to the photodetector unit, and the second hologram provided to diffract a reflection beam of the laser beam of the second laser diode to the photodetector unit.

Optical pickup apparatus having an improved holographic unit, and optical disk drive including the same

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.

An optical pickup apparatus used in an optical data recording/reproducing apparatus for reading/reproducing data on an optical recording medium, including a light source, a diffracting device configured to transmit a light beam and to diffract a light beam reflected from the optical recording medium, an optical device having a reflecting portion and a transmitting portion configured to reflect one part of the light beam emitted from the light source and to transmit another part of the light beam to the optical recording medium and from the optical recording medium, and a photodetecting device to detect the light beam from the optical recording medium for signal light detection, and the light beam reflected by the reflecting portion of the optical device for monitor light detection of the light source.

Optical pickup apparatus, optical data recording/reproducing apparatus, and optical data recording/reproducing method

Optical apparatus for recording/reproducing and reading/reproducing data on an optical recording medium, and method for using same

Optical pickup apparatus and optical pickup method adapted for selectively using laser light of different wavelengths

An optical pick-up having a high-density double diffraction grating constructed with two high-density diffraction gratings superposed on each other wherein polarized light rays are separated so that P-polarized light rays pass through the double diffraction grating and S-polarized light rays are diffracted. The optical pick-up is disposed in the optical path between a light source and a recording medium.

Optical pick-up device and method using a high-density double

An optical head which records data onto an optical data recording medium and reproduces the data therefrom includes a laser light source, a collimator lens, an objective lens, a light splitting device arranged between the laser light source and the objective lens, for splitting the emitted light from the laser light and a reflected light from the optical data recording medium. A diffraction grating is provided to which only the reflected light split at the light splitting device is incident to, and which leads the reflected light split at the optical element onto a photo-detector. Thereby, an optical head of high effectiveness in utilization of light and low cost can be obtained.

Optical head with forward and reflected light beams propagating through

The present invention relates to an optical head for recording, reproducing and erasing data on an optical data recording medium. The optical head has a fixed optical system having a laser optical source for emitting a light and a signal detecting optical system for detecting an error signal. A movable optical system having a beam splitter provided with a prism boundary face and having an objective at a position thereof opposing a surface of the optical data recording medium for receiving the emitted light through the beam splitter and focusing the received light onto the surface of the optical data recording medium as an optical spot. The beam splitter has, at the prism boundary face thereof, a polarizing film for transmitting one portion of the emitted light from the laser light source. The beam splitter has, at one side face thereof, reflective face for reflecting one portion of or all of the transmitted light through the polarizing film, and has, at another side face thereof, a light receiving element thereof for receiving the reflected light from the reflective face and one portion of said reflected light from the surface of the optical data recording medium.

Optical head

In a wavelength converting element, an oscillation line at a predetermined wavelength is excited on the basis of excited light having a predetermined wavelength. Frequencies of the excited light and light on the oscillation line are mixed with each other in a nonlinear optical medium to generate light having a sum frequency. The wavelength converting element has resonators for the oscillation line and the excited light. A system for recording and reproducing optical information has a first light source capable of being directly modulated, and a second light source for emitting light having a wavelength shorter than that of a light beam emitted from the first light source. The first beam from the first light source is superposed on the short wavelength light from the second light source to record and reproduce the optical information. This system uses an overwrite recording system in which a writing operation of data is performed by emitting and superposing a modulated light beam from the first light source on the short wavelength light, and data indicative of value '0' are equivalently written to a memory medium by erasing data therefrom in this writing operation.

Wavelength converting element and system for recording and reproducing

An optomagnetic information recording and reproducing apparatus includes an optomagnetic optical pick-up for recording or reproducing information on or from an optomagnetic information recording disc. An optomagnetic optical pick-up includes a first diffraction grating for receiving light reflected from the disc and separating the light into a first transmitting light which transmits through the first diffraction grating beam and a first diffracted light beam which is diffracted by the first diffraction grating. A second diffraction grating is disposed to receive the first transmitging and diffracted light beams and discharges a second transmitting light beam and a second diffracted light beam. A tracking error detector is provided to receive the second transmitting light beam and a focusing error detector is disposed to receive the second diffracted light beam. An optomagnetic signal is obtained as a difference between outputs from the tracking and focusing error detectors.

Optical pick-up for use with an opto-magnetic signal

In an apparatus for recording and reproducing optical information, light emitted from a laser beam source is irradiated to an optical information recording medium to record the optical information and the light reflected from the recording medium is guided to a signal detecting optical system to detect tracking and focusing error signals and a reproducing signal. The apparatus comprises a dual grading arranged through a detecting lens on an optical path on which the light reflected from the recording medium is guided to the optical system, the dual grating having diffraction gratings formed at an equal pitch on the front and rear faces of a substrate, a refractive index of the substrate being greater than the refractive indexes of the diffraction gratings; and a photodetector for detecting light transmitted through the dual grating. The dual grating may have diffraction gratings respectively formed at equal and irregular pitches on both faces of a substrate. The dual grating may have a front face grating formed on a first incident side of the reflected light and a rear face grating formed on the side of a substrate opposite to the first incident side; the front face grating having a pitch smaller than that of the rear face grating; an incident angle of the reflected light with respect to the front face grating being set to be greater than a Bragg angle with respect to the front face grating.

Optical pickup device with dual grating element

In an apparatus for recording and reproducing optical information, a light beam splitter is disposed on an optical path between a laser beam source and an optical information recording medium. The light beam splitter has a three-beam forming diffraction grating on one face of this light beam splitter on a light-emitting side thereof. The light beam splitter also has a light branching diffraction grating on another face thereof. A light beam emitted from the laser beam source is divided into three beams by the three-beam forming diffraction grating. The light branching diffraction grating is used to branch light reflected from the optical information recording medium. A polarizing/separating diffraction grating is formed in the light beam splitter on the same plane as the three-beam forming diffraction grating. The polarizing/separating diffraction grating is used to polarize and separate a light beam branched by the light branching diffraction grating.

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Zama, Japan

Shigeru Ohuchida