Mitsubishi Denki Kabushiki Kaisha

Mitsubishi Denki K.k.

Teruo Fujita

Nobuo Takeshita

Morihiro Karaki

Kazuhiko Nakane

Mitsuru Irie

Shinsuke Shikama

Mitsushige Kondo

Kenjiro Kime

Keizo Kono

Kazuo Okada

Masahisa Shinoda

Toshiya Matozaki

Michihiro Tadokoro

Yoko Inoue

Akira Sekiguchi

Yoshiyuki Goto

Hiroo Shimegi

Naoyuki Egusa

Hideaki Kobachi

Manabu Koike

Yasuyuki Sato

A light wavefront measuring apparatus () includes a separating element () for separating a flux of light which exits from an optical head () into a first beam and a second beam, a first interference fringe display section () for displaying interference fringes formed from the first beam, a Dove prism () for rotating a wavefront of the second beam around its optical axis (AX), and a second interference fringe display section () for displaying interference fringes formed from the second beam which passed through it. In adjustment of the light source device, position of a collimator () in the optical head () is adjusted in optical axis direction so as to approximate the interference fringe patterns displayed in the interference fringe display sections () each other.

Light wavefront measuring instrument, light wavefront measuring method, and light source adjusting method

An image display apparatus includes a plurality of light emission sources, a drive circuit for pulse-driving the plurality of light emission sources in order in a predetermined period, a moving reflecting mirror for swinging in order in an incidence direction of light from each of the light emission sources in response to the pulse driving timing of each of the light emission sources and reflecting light beams from the light emission sources in order approximately in the same direction, and a combining optical system for guiding the light reflected by the moving reflecting mirror into a light valve.

Image display apparatus

Light reflected from an information recording surface is branched into first and second substantially parallel beams. The first beam is directed to a focus error detection system and the second beam is directed to a tracking error detection system. The photodetector includes light receiving sections for the two detection systems. The light receiving sections include Light receiving surfaces and are housed in a single package. A substantially flat plate is placed either in the focus error detection system or in the tracking error detection system, serving to shorten the optical path so as to create a difference in optical path length to the light receiving surfaces between the two detection systems, thereby enlarging the light spot on the light receiving sections for the tracking error detection system. A cylindrical lens placed in the tracking error detection system serves as astigmatism generating and to make the light spot on the light receiving section in the tracking error detection system to be enlarged in one direction. The light receiving surfaces of one detection system have division lines substantially perpendicular to that of the other detection system. The perpendicular division lines are effective in eliminating an inherent problem encountered in the prior art optical head that adjustment of the tracking error detection system affects the adjustment of the focus error detection system.

Optical head having focus error detection and tracking error detection

To achieve a tracking error detection, a device for use in a simple optical system is disclosed which reduces offset resulting from the lateral movement of an objective lens or a tilt of an information recording medium. The disclosed device maintains the maximum amplitude of a tracking error signal irrespective of variations in track pitch of the information recording medium. The device produces a light beam having substantially-half portions about 180 degrees out of phase with each other, and another light beam which are directed and focused via an objective lens to an information recording medium. The light spots formed by the two light beams are disposed on the information recording medium with a spacing of substantially an integral multiple of the track pitch in the direction perpendicular to the tracks on the information recording medium. Each light beam returning from the information recording medium is received by a pair of split photodetectors, and a tracking error signal is obtained from the difference between the differential outputs.

Optical head tracking error detection device

In an optical disk device for recording or playing back information on or from an optical information recording medium having land parts forming information tracks and groove parts interposed between adjacent land parts, the land part is illuminated with a first light spot, and the groove part is illuminated a second light spot, a first focus error signal is produced in accordance with the reflected light beam of the first light spot, and a second focus error signal is produced in accordance with the reflected light beam of the second light spot, and focus control is performed in accordance with the first and second focus error signals. In another aspect of the invention, each of the light receiving sections of a photodetector used for receiving the reflected light has an array of tapered projections along in a region between main parts the light receiving sections, and the tapered projections of the light receiving sections are interdigitated with each other. Improved devices for tilting the objective lens is also provided.

Optical disk device

An optical device inclination angle adjuster for adjusting an optical axis of an optical device. The optical device has an optical axis and a peripheral portion, and is held by a holder. The adjuster includes an annular plate inserted between the optical device and the holder. The annular plate is in alignment with the peripheral portion of the optical device, and has an opening with an axis in alignment with the optical axis of the optical device to permit passage of light through the opening of the annular plate and through the optical device. A first pair of projections are formed between the annular plate and the optical device. The first pair of projections are disposed diametrically opposite to each other with respect to the optical axis and project in a direction parallel to the optical axis. A second pair of projections are formed between the annular plate and the holder. The second pair of projections are disposed diametrically opposite to each other with respect to the optical axis and project in a direction parallel to the optical axis. The first pair of projections and the second pair of projections are disposed at different rotary angles about the optical axis; whereby the inclination angle is adjusted by rotating the optical device about the first pair of projections or about the second pair of projections.

Optical device inclination angle adjuster

A focus error detecting device includes a reflected beam obscurer and a two-division photodetector. The observer obscures a part of the reflected beam. The two-division photodetector includes first and second light receiving sections separated from each other by a division band region which receive the reflected light beam not obscured by the obscurer. A focus error signal is produced based on the output of each light receiving section. Each light receiving section has an array of tapered projections along its edge in the division band region. Alteratively, the light receiving sections have a main part with an edge coincident with an edge of the division band region, and groups of light receiving stripes extending in a direction parallel with the edges of the main part.

Focus error detecting device

A focus error detecting device includes a reflected beam splitter and at least two two-division photodetectors. The reflected beam splitter includes a diffraction grating part and a non-diffraction grating part separated by a line dividing a reflected beam. The dividing line projects to a line orthogonal to a guide groove on the information recording medium. The diffraction grating part produces a first split beam, and non-diffraction grating part produces a second split beam. Each two-division photodetector receives one of the first and second split beams incident and their light receiving sections, and produces a signal for effecting focus control.

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 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.

Optical recording/reproducing apparatus

An optical head for recording, reproducing or erasing data by emitting a light beam irradiated from a light source onto a recording medium. To reduce the height of the optical head, an optical axis shifting device is disposed between a light beam emitting device and a condensing device for condensing the light beam onto the recording medium. This optical axis shifting device shifts the first optical axis of the light beam from the light beam emitting device to a second optical axis positioned in parallel and spaced apart from each other. As the optical axis shifting device, there is preferable employed a prism having two reflecting faces lying in parallel, and the optical axis, after shifting is to be positioned downwardly of the position of the optical axis before shifting, thereby reducing the height of the optical head.

Optical head

An optical read/write apparatus includes an optical device for directing a main scanning spot and a pair of satellite spots, one on either side of the main scanning spot, onto a recording. It further includes a wobbling device for moving the satellite spots in relation to the main scanning spot. The satellite spots are moved with an oscillatory motion in a direction perpendicular to tracks on the recording medium. A tracking control device detects light reflected from the satellite spots, generates a tracking error signal, and moves the main scanning spot according to the tracking error signal in a direction perpendicular to the. This keeps the main scanning spot accurately centered on a track without offset and without wobbling the main scanning spot.

Optical read/write apparatus with improved tracking performance

An optical read-write apparatus for reading and writing information in tracks on an optical medium such as an optical disk has two or more beam sources for producing light beams with different wavelengths, and corresponding dichroic mirrors mounted in the path of the beams. Each of the dichroic mirrors reflects light of the wavelength of one of the beams and transmits light of other wavelengths. Piezoelectric transducers are provided for tilting one or more of the dichroic mirrors to adjust the tracking of the beams. An objective lens receives the beams after reflection from the dichroic mirrors and focuses them onto the optical medium.

Optical read-write apparatus

Optical information recording and reproducing apparatus with tracking

Optical information recording/reproducing apparatus

The present invention has an object to provide a focus sensor or tracking sensor for an optical recording and reproducing device, which has a simplified optical system whose adjustment is much facilitated. The operational principle of this device is to produce a focusing error signal or tracking error signal by vibrating light spot on an optical disc with a small amplitude to scan interference fringes produced in the far field on an optical disc on the basis of a periodicity of information tracks of the optical disc and processing output signals of an optical sensor arranged in the far field.

Growing community of inventors

Nagaokakyo, Japan

Teruo Fujita