Mitsubishi Denki Kabushiki Kaisha

Morihiro Karaki

Mitsuru Irie

Nobuo Takeshita

Teruo Fujita

Kazuhiko Nakane

Masahisa Shinoda

Yasuyuki Satou

Hideaki Kobachi

Shigenori Yagi

Akihiro Shima

Kenjiro Kime

Akira Ishimori

Naoyuki Egusa

Manabu Koike

Takeshi Utakouji

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

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

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

A lens actuating system for an optical disk drive has an objective lens movably mounted in a movable frame with orthogonal X-, Y-, and Z-axes. A seeking servo moves the frame in the X-direction. A tracking servo moves the objective lens in the X-direction. A focusing servo moves the objective lens in the Z-direction. An optoelectronic sensor detects the relative position of the objective lens and frame in the X-direction, so that the tracking servo can maintain a fixed relative position during track-seeking, or in the Z-direction, to establish a neutral point on the Z-axis for the focusing servo. Force applied by the focusing servo or tracking servo to move the objective lens in one direction can be opposed by an equal and opposite force applied to a driven mass, so that a net zero force is transmitted to the frame.

Lens actuating system for an optical disk drive having a driven mass for

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.

Lens actuating system with improved frequency response for optical disk

A multi-beam optical recording-reproducing device is capable of detecting the focusing and tracking errors of respective beams independently of each other by means of a simple optical system. The optical system for independent tracking error detection may include a wedge prism 39 and a four-partitioned photosensor 42, and that for the independent focusing error detection may include a half prism 33 for dividing the beams into reflected and transmitted portions, first and second knife-edges 34 and 19 for the reflected and transmitted beams, respectively, and a first and second two-partitioned photosensors 35 and 20 for receiving the beams via the first and the second knife-edge, respectively (FIG. 7). Alternatively, the optical system for independent focusing error detection may include a single knife-edge plate 61 having two knife-edges, and a four-partitioned photosensor 64 (FIG. 10), or a wedge prism 71 and an eight-partitioned photosensor 74 (FIG. 12). Further, the optical system for independent tracking error detection may include a concave cylindrical lens 83 (FIG. 14) forming a far field pattern perpendicular to the tracks on the information storage optical medium 9.

Multi-beam optical recording-reproduction device with independent error

An optical recording/reproducing apparatus capable of detecting recording defects on an information recording medium comprises a beam irradiation device for irradiating a first beam, by which information pits are recorded on/reproduced from the information track on the information recording medium, a second beam preceding the first beam and a third beam following the first beam, along the information track; an optical detector having a plurality of light receiving surfaces for individually detecting the reflected light of the first beam, the second beam and the third beam, which have been reflected from the information recording medium; a monitoring device for, in a recording mode, monitoring the condition of the information track prior to and after recording in response to amount-of-light signals which respectively correspond to the reflected light of the second beam and the third beam; and a signal generator for, in a reproducing mode, producing a tracking error signal in response to the amount-of-light signals. The optical recording/reproducing apparatus is characterized in that the beam irradiation device includes a light spot switching device for changing the light spot locations of the second beam and the third beam on the information recording medium, depending upon the recording mode or the reproducing mode.

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Nagaokakyo, Japan

Morihiro Karaki