Abstract: An optical head with a plurality of semi-conductor laser chips for use in reducing inclination or gradient of more than one beam presently falling onto a focusing lens is disclosed. To this end, a double mirror or alternatively beam reshaping means is disposed which has different reflection planes for permitting reflection of a plurality of laser beams incoming from the semiconductor laser chips.

Abstract: When it is intended to realize a lens having a large NA with one lens, an adjustment precision between both surfaces of the lens is very strict. Accordingly an objective lens having an NA of 0.8 or more was usually realized by two lenses. However, a working distance is small, and collision of the objective lens with a disc is apt to occur. A coma corrector for compensating coma caused by decentering of both surfaces in realizing the high NA lens with one lens is added. However, in this case, astigmatism occurs when the objective lens decenters from the coma corrector relatively accompanied with a tracking operation. The objective lens and the coma corrector are fixed to a mirror barrel so as to be unified with each other, and driven by a two-dimensional lens actuator. With such a constitution, decentering of the objective lens and the coma corrector does not occur, and hence astigmatism does not occur.

Abstract: A data recording and reproducing apparatus includes a recording disabled state determining device for determining whether or not the optical disc is in a recording disabled state, in which the data recording and reproducing apparatus controls the rotation of the optical disc to increase a rotational speed during reproduction processing higher than the rotational speed during recording processing to reproduce data when the recording disabled state determining device determines that the optical disc is in the recording disabled state, thereby accepting a recording instruction and a reproduction instruction as required at any time, and avoids reproducing data at the same reproducing speed as a recording speed which is unnecessarily slower than the reproducing speed.

Abstract: Before original information is recorded in areas such as a recording medium management area where the same pattern of information is recorded many times, a dummy pattern that minimizes a recording film flow is recorded. Because the direction of the recording film flow depends on the length of a mark length, the dummy pattern is a pattern including marks with a unique length. Randomly or sequentially selecting and recording a plurality of dummy patterns, each with a recording film flow direction different from others, prevents jitters, which will be caused by the recording film flow, from increasing.

Abstract: An optical disc drive using either one of a first disc (e.g., DVD) and a second disc (e.g., CD), is provided with a first laser diode that emits a shorter wavelength beam, a second laser diode that emits a longer wavelength beam, an objective lens, and a driving unit that holds and rotates the optical disc. The optical axis of the objective lens is inclined relative to a normal to the optical disc. The first laser diode is located at a first position so that the coma, which is caused when the first laser beam is converged on a data recording surface of the first disc, is minimized, and the second laser diode is located at a second position so that the coma, which is caused when the second laser beam is converged on a data recording surface of the second disc, is minimized.

Abstract: Before original information is recorded in areas such as a recording medium management area where the same pattern of information is recorded many times, a dummy pattern that minimizes a recording film flow is recorded. Because the direction of the recording film flow depends on the length of a mark length, the dummy pattern is a pattern including marks with a unique length. Randomly or sequentially selecting and recording a plurality of dummy patterns, each with a recording film flow direction different from others, prevents jitters, which will be caused by the recording film flow, from increasing.

Abstract: In an apparatus and method for information storage and retrieval, information is retrieved from the storage apparatus in a manner which includes varying an operational parameter of the storage apparatus according to a property of the information being retrieved. In the same apparatus and method, information is stored onto the storage apparatus in a manner which includes varying an operational parameter of the storage apparatus according to a property of the information to be stored. In this way, the energy consumption of the storage apparatus can be kept low.

Abstract: An optical head having a plurality of laser light source and a plurality of photodetectors corresponding to the plurality of laser light sources. The plurality of laser light sources have at least three wavelengths with frequencies which are different from one another, a first laser module includes at least two laser light sources with two frequencies which are in close proximity and two photodetectors corresponding to the at least two laser light sources, and a second laser module includes another laser light source and another photodetector corresponding to the another laser light source.

Abstract: Before original information is recorded in areas such as a recording medium management area where the same pattern of information is recorded many times, a dummy pattern that minimizes a recording film flow is recorded. Because the direction of the recording film flow depends on the length of a mark length, the dummy pattern is a pattern including marks with a unique length. Randomly or sequentially selecting and recording a plurality of dummy patterns, each with a recording film flow direction different from others, prevents jitters, which will be caused by the recording film flow, from increasing.

Abstract: An optical head having a plurality of laser light source and a plurality of photodetectors corresponding to the plurality of laser light sources. The plurality of laser light sources have at least three wavelengths with frequencies which are different from one another, a first laser module includes at least two laser light sources with two frequencies which are in close proximity and two photodetectors corresponding to the at least two laser light sources, and a second laser module includes another laser light source and another photodetector corresponding to the another laser light source.

Abstract: An optical disc drive using either one of a first disc (e.g., DVD) and a second disc (e.g., CD), is provided with a first laser diode that emits a shorter wavelength beam, a second laser diode that emits a longer wavelength beam, an objective lens, and a driving unit that holds and rotates the optical disc. The optical axis of the objective lens is inclined relative to a normal to the optical disc. The first laser diode is located at a first position so that the coma, which is caused when the first laser beam is converged on a data recording surface of the first disc, is minimized, and the second laser diode is located at a second position so that the coma, which is caused when the second laser beam is converged on a data recording surface of the second disc, is minimized.

Abstract: An objective lens converges a shorter wavelength laser beam on a DVD having a protective layer, which is 0.6 mm thick, and a longer wavelength laser beam on a CD having a protective layer, which is 1.2 mm thick. A common region is defined on the objective lens. The common region provides a numerical aperture appropriate for converging the longer wavelength laser beam on the CD. Coma of the objective lens in the first region is compensated better in a case where the longer wavelength laser beam is converged on the CD than a case where the shorter wavelength laser beam is converged on the DVD.

Abstract: In an optical head for recording on or reproducing from a plurality of kinds of optical information recording media corresponding to a plurality of kinds of different wavelengths, coma aberration is prevented, and low price and high reliability are realized. To that end, in an optical head constituted by laser light sources of three wavelengths and photodetectors corresponding to the laser light sources of the three wavelengths, a two-laser module including laser light sources of two adjacent wavelengths and photodetectors corresponding to the laser light sources, a laser module including a laser light source of the rest one wavelength and a photodetector corresponding to the laser light source, and a dichroic mirror bonded with a rising mirror are combined.

Abstract: In optical heads with multiple semiconductor laser chips with different wavelengths, coma aberrations generated by laser beams projected at an angle relative to the entry axis of a focus lens is reduced.

Abstract: In a wobble signal detecting circuit provided by the present invention, a wobble signal is converted into binary data before being supplied to a PLL circuit by way of a polarity switching circuit and a clock switching circuit. The PLL circuit outputs a recording/playback timing generation clock signal. The frequency of the recording/playback timing generation clock signal is divided by a frequency dividing circuit before being fed back to the PLL circuit. A difference in phase between the wobble signal and the feedback signal is detected by a phase inversion detecting circuit and, if the difference in phase exceeds a phase difference determined in advance, the phase inversion detecting circuit generates a polarity switching signal for switching the polarity of the wobble signal. The polarity switching signal is used to invert the polarity of the polarity switching circuit.

Abstract: The recording and reproducing apparatus comprises an Small Computer System Interface (SCSI) controller, an optical disc device, a magnetic disc device, a disc controller which controls the optical disc device and the magnetic disc device, connectors which connects directly the optical disc device and the magnetic disc device, and a selector which selects one of the optical disc device and the magnetic disc device. A Copy or Verify command is carried out within the apparatus without an SCSI bus, and data are transferred through the connector. Therefore occupation of the SCSI bus and overhead of the SCSI protocol are eliminated, and the apparatus is miniaturized by common use of the SCSI controller and the disc controller.

Abstract: A MCAV optical disc read/write system with a postscript type of recording medium is disclosed, which uses a pit edge method of recording information in spiral physical tracks of the medium. The spiral physical tracks are grouped into logical tracks in which a single track address is assigned to each logical track. The logical tracks in turn are grouped into circumferential zones. The number of physical tracks constituting a logical track in adjacent circumferential zones, and the number of track sectors per logical track are set such that the increment in the number of sectors per physical track in proceeding from an inner one to an outer one of such zones is controlled to minimize rate changes in the read/write clock frequency at zone boundaries. Sector addresses thereby may be read even when a read/write head is positioned in a wrong one of adjacent zones.

Abstract: A super high density optical disk apparatus is obtained by using an exchangeable recording medium having a recording capacity of at least 1.5 Gb/in.sup.2 in an optical recording and reading apparatus for recording or reading at least using a laser beam or by using one of means which can record on a recording medium only once and means which can record at least two times repeatedly as recording means to be used.

Abstract: In a write control method on an optical recording, at least one shift amount selected from the defocus amount of a laser beam on a recording medium, the shift amount of a recording position on a recording track and the shift amount of laser power during recording is controlled such that the selected amount falls within a predetermined range. Subsequently, a trial signal is trially recorded at a plurality of trial zones on the recording medium by using a laser power value as a parameter. The recorded trial signal is read and a difference .DELTA.V between center levels of a highest density waveform and a lowest density waveform is detected. In connection with each trial zone, the laser power value when a reading trial signal which makes the difference .DELTA.V minimum is recorded is defined as an optimum recording power value.

Abstract: A super high density optical disk apparatus is obtained by using an exchangeable recording medium having a recording capacity of at least 1.5 Gb/in.sup.2 in an optical recording and reading apparatus for recording or reading at least using a laser beam or by using one of an element which can record on a recording medium only once and another element which can record at least two times repeatedly as recording elements to be used.