Mitsubishi Denki Kabushiki Kaisha

Mitsubishi Electric Corporation

Masahisa Shinoda

Kenya Nakai

Daisuke Matsubara

Nobuo Takeshita

Keiji Nakamura

Kenjiro Kime

Hironori Nakahara

Takeshi Ito

Toru Yoshihara

Toshiya Matozaki

Morihiro Karaki

Naoyuki Egusa

Manabu Koike

Yasuyuki Satou

Yasuyuki Sato

Takeshi Utakouji

Masaharu Ogawa

Shigenori Yagi

Eiji Yokoyama

Akihiro Shima

Teruo Fujita

Norihiro Watanabe

Akira Ishimori

Kouichi Komawaki

Masayuki Omaki

Mitsuru Irie

Hideaki Kobachi

When using an optical disc medium that includes pit trains having their widths narrower than a diffraction limit, it is difficult to detect a tracking error signal and take a tracking-servo control while increasing pit density in a direction orthogonal to a pit-train extension direction. Information pit trains are arranged spirally or concentrically and formed in a structure in which their depths are changed periodically at a pitch radially along the optical disc medium, so that the tracking error signal can be obtained by push-pull detection of diffraction light from the structure.

Optical disc medium and optical disc device

An optical head device mounted in an optical disc device. The optical head device is provided with a diffractive optical element and a photodetector. The diffractive optical element has: a primary diffraction region at a location on which the positive and negative first-order components and some of the zero-order component of a reflectively diffracted light beam are incident; and secondary diffraction regions at locations on which the rest of the zero-order component but none of the positive or negative first-order components of the reflectively diffracted light beam are incident. A main light-receiving section of the photodetector receives the zero-order component of a transmissively diffracted light beam that has passed through the primary diffraction region and the secondary diffraction regions. Secondary light-receiving sections receive the positive first-order component and/or the negative first-order component of the transmissively diffracted light beam that has passed through the secondary diffraction regions.

Optical head device and optical disc device

An optical pickup with a simplified structure in which, according to the type of optical disc, diffracted light from three types of laser light can be directed efficiently onto a photodetector and appropriate focus control can be performed based on the signals detected by the photodetector, and a diffractive optical element that can be used in the optical pickup, which has a semiconductor laserthat can emit three types of laser light, a diffractive optical elementthat diffracts the laser light reflected from the optical disc, and a single photodetectorthat detects the diffracted light exiting the diffractive optical element. The diffractive optical elementis structured so that 0-order light is the maximal component of the diffracted light generated from each of two of three types of laser light, the two having close wavelengths (with a small wavelength difference), and +1-order light or &#x2212;1-order light is the maximal component of the diffracted light generated from the remaining one type of laser light.

Diffractive optical element and optical pickup

An optical pickup has a semiconductor laser device that can emit laser beams with different wavelengths. A beam splitter and objective lens direct the emitted beam onto a rotating optical disc. Reflected light returns through the objective lens and beam splitter to a photodetector. A pair of liquid crystal elements on the optical path from the optical disc to the photodetector have controllable lens functions acting in different directions to produce an adjustable astigmatic effect that enables the photodetector to generate a focus error signal with a linear range appropriate for the type of optical disc, the number of signal layers in the optical disc, and the spacing between the layers.

Optical pickup and optical disc drive

An optical pickup device is provided. The optical pickup device includes a first, second, and third light emitting portions emitting light beams having first, second, and third wavelengths, respectively; an adjusting element for optical axes enabled to control the optical axis of the return light beam reflected by the optical recording media after output from the light emitting portion, and a single photo detector receiving the return light beams passing through the adjusting element for optical axes. The first light emitting portion and the second light emitting portion are arranged in such a way that the optical axis of the first light beam and the optical axis of the third light beam approximately coincide with each other. The adjusting element for optical axes controls the axis of the return light beam of said second light beam and the single photo detector receives the return light beams of the first light beam, the second light beam and the third light beam.

Optical pickup device and optical disc device

A diffractive optical element whose two diffraction gratings diffract three different wavelength light beams is provided. The diffractive optical element includes a first diffraction grating and a second diffraction grating that is located opposite the first one, and is configured in such a way that, among three different wavelength incident light beams, the diffraction efficiency in one light beam diffracted on the first diffraction grating is a predetermined value or less, and the diffraction efficiencies in the other two different incident light beams diffracted on the second diffraction grating are predetermined values or less. This arrangement can achieve a diffractive optical element capable of diffracting the three different wavelength light beams in a simple configuration.

Diffractive optical element and optical head

An optical-pickup-adjustment optical disk used for adjusting or producing an optical pickup device, includes a transparent protective substrate; and an optical-pickup-adjustment middle-depth information recording layer formed on a side of an inside surface of the transparent protective substrate, wherein the optical-pickup-adjustment middle-depth information recording layer is formed to have a middle depth which is a center of the maximum depth of the maximum-depth information recording layer prescribed by the optical disk standard and the minimum depth of the minimum-depth information recording layer prescribed by the optical disk standard.

Optical-pickup-adjustment optical disk, method of adjusting optical pickup device, and method of producing optical pickup device

A laser emitting device () includes a light emitting portion () that emits light of a wavelength &#x3bb;(approximately 405 nm), a light emitting portion () that emits light of a wavelength &#x3bb;(approximately 650 nm), and a light emitting portion () that emits light of a wavelength &#x3bb;(approximately 780 nm). The light emitting position of the light emitting portion () and the light emitting position of the light emitting portion () are approximately on the same position as seen in the direction of an optical axis of emitted light of the laser emitting device (). An optical axis adjusting element () is provided for adjusting an optical axis of return light of at least one of the wavelengths among return lights of the wavelengths &#x3bb;and &#x3bb;so that respective return lights emitted by the light emitting portions (and) of the laser emitting device () and reflected by an optical recording medium () are received by a common light detector ().

Optical pickup device and optical disk device

A semiconductor laser unit includes a plurality of semiconductor laser elements arranged parallel with one another in a laser beam-emitting direction, and a base for positioning and fixing the plurality of semiconductor laser elements. The plurality of semiconductor laser elements are arranged such that a laser beam emitted from the semiconductor laser element greatest in astigmatism, of the plurality of semiconductor laser elements, is coincident in its axis with a reference axis of the base. In the case that the semiconductor laser unit is arranged on an optical head device, the focusing characteristic on the plurality of laser beams can be improved.

Semiconductor laser unit and optical head device

The reference character 5 denotes a supporting shaft holding base, which holds the lower end of a supporting shaft 103 coated with fluororesin with a small frictional coefficient. The reference characters 107a and 107b are tracking magnets bipolar-magnetized in the right and left direction, which are fixed to a fixing base 1 by bonding. The character 108 denotes a mirror for reflecting a light beam 2 incident from the front in the vertical upward direction. The character 6 denotes a lens holder formed of a plastic material, or the like, with light weight and high stiffness, which holds objective lenses 3 and 4 corresponding to a plurality of optical information recording media with different substrate thicknesses and different recording densities at positions eccentrically displaced by almost equal distances from the supporting shaft 103.

Optical information processing device having switchable optics for use

The second harmonic wave of a solid laser light which is emitted from a second harmonic wave light source is divided into a plurality of laser beams by a diffraction grating. The divided laser beams are converged on a record carrier into a plurality of light spots by an optical head. Magnetic field generating coils for applying magnetic fields to the respective light spots in accordance with the recording signals from a signal line are disposed under the record carrier. Part of the solid laser light is reflected and input to a beam splitter. Since part of the light input to the beam splitter is taken out, a stabilizer controls the output of the solid laser light from the second harmonic wave light source, parallel recording/reproduction using the plurality of light spots which are arranged on the record carrier is enabled and the formation of the plurality of light spots is effectively controlled. Thus, a magneto-optical recording and reproducing apparatus which is capable of high-density recording and high-speed data transfer, which supplies a stable and accurate optical output, and which facilitates the control of the optical output is provided.

Magneto-optical recording and reproducing apparatus

An optical recording apparatus which reduces light loss by expanding the laser beam diameters irradiated from a plurality of beam sources, and reducing the expanded beam diameters immediately before focusing the beams onto an information recording/reproducing medium to make the beams circular, thereby minimizing deviation of the laser beam from the optical axis. An optical system for use in recording apparatus with a multi-beam optical head provided with a plurality of laser beam sources in a fixed unit which reduces light loss by minimizing deviation of the laser beam from the optical axis, and also by maintaining the laser power of each laser beam at a predetermined intensity independent of changes in distance between the fixed unit half and the moving unit half of the optical system by detecting intensities of the laser beams focused on a recording medium.

Laser power control of an optical head with a plurality of beam sources

An optical recording and reproducing apparatus uses a laser to form one or more spots on an information recording medium preformatted with wobbling guide grooves, and detects tracking error. If the differential push-pull method of detecting tracking error is used, a center spot is flanked by satellite spots distant by an odd multiple of half the repeating period of tile wobble. If the three-beam method is used, the distance is an odd multiple of one-fourth the repeating period of the wobble. If the push-pull method is used, a split photodetector generates a pair of electrical signals. The sum and difference of these signals are filtered, then synchronously detected, and the result is combined with the difference signal to generate a corrected tracking error signal.

Optical recording and reproducing apparatus for tracking wobbling guide

An optical recording and reproducing apparatus uses a laser to form one or more spots on an information recording medium preformatted with wobbling guide grooves, and detects tracking error. If the differential push-pull method of detecting tracking error is used, a center spot is flanked by satellite spots distant by an odd multiple of half time repeating period of tile wobble. If tile three-beam method is used, the distance is an odd multiple of one-fourth the repeating period of the wobble. If the push-pull method is used, a split photodetector generates a pair of electrical signals. The sum and difference of these signals are filtered, then synchronously detected, and the result is combined with the difference signal to generate a corrected tracking error signal.

Growing community of inventors

Tokyo, Japan

Masahisa Shinoda