Eastman-kodak Company

Alan B Marchant

Dennis G Howe

Eugene G Olczak

Joseph J Wrobel

Alan T Brewen

Barton E Dahneke

Ingolf Sander

Frank R Whitehead

Joseph J Miceli, Jr

Herbert L Engstrom

A method for multi-track optical data recording comprising the steps of providing an optical recording medium that includes a plurality of parallel, preformatted guide tracks, with sufficient space between adjacent guide tracks for recording a plurality of data tracks; providing relative motion between the optical recording medium and an optical head in a direction generally parallel to the guide tracks; imaging a guide track onto a detector array disposed relative to the optical recording medium; and generating a first tracking error signal representing the cross-track displacement of the guide track relative to the optical head. The method further comprises driving a closed-loop servo system to reduce the residual tracking runout of the guide track and simultaneously recording a band of data tracks in the unpreformatted space adjacent to the guide track and one or more control tracks parallel to the data tracks.

Preformatted guide tracks and co-written control tracks for multichannel optical recording

A method for optical data recording and readout includes scanning a blank region of an optical recording medium while recording a data band including a plurality of adjacent data tracks; synchronizing the recording on all tracks to a common data clock; and simultaneously recording control tracks with the band of data tracks, each control track having a well-defined track center and a repetitive pattern of marks that is synchronized to the data clock. The method further includes optically sensing the cross-scan positions and clock offsets of at least one control track on either side of the data band; interpolating between the control track cross-scan positions to predict the cross-scan positions of each data track and compensate for magnification errors; interpolating between the control track clock offsets to predict the clock offset of each data track and compensate for skew errors; and simultaneously reading and decoding information recorded on all tracks of the data band.

Multi-track optical data recording and readout

A method for preformatting an optical recording medium with a plurality of parallel guide tracks, each guide track controlling the recording of a band of data tracks; said method includes providing a source laser beam along a predetermined path at a wavelength which is selected to be within the sensitivity range of the optical recording medium and providing a beam splitter in the predetermined path which divides the source laser beam into a multiplicity of preformatted recorded beams directed to impinge upon the optical recording medium. The spacing or pitch between the beams at the optical recording medium is uniform.

Preformatting optical recording medium

An error correction method for multitrack data recording and read out of recorded multitrack digital data includes organizing input digital data into a sequence of data words and encoding each data word as a fixed-length transverse error correcting code word having a fixed number of symbols which represent digital data and parity.

Multitrack data recording and read out of recorded multitrack digital data for error correction

Apparatus for simultaneously recording and reading information on a medium moveable in forward and reverse directions includes a first record laser and means for establishing a first beam path for recording information on the moveable medium and a second read laser and at least a first and second read-out detector respectively associated with the forward and reversed directions of the recording medium and means for establishing two beam paths which direct the laser light to positions forward and rearward from where the first laser beam illuminates the medium and such read laser beams are reflected respectively to the first and second detectors. The apparatus further includes means to select either the first or the second read-out detectors and to process information read by such selected detector so that as the medium is moving in the forward direction, the data are read from the first detector and when the medium is moving in the reverse direction. the data are read from the second detector.

Apparatus for recording and simultaneously reading information recorded on a moveable optical recording medium using objective lens and beam splitter

Apparatus for collimating multiple laser beams from a Vertical Cavity Surface Emitting Laser (VCSEL) array and directing the collimated beams through a common aperture includes a VCSEL array including at least two VCSEL sources disposed in a spatial pattern and each VCSEL source emitting a divergent laser beam; a microlens array with lenslet elements disposed in a spatial pattern geometrically similar to the pattern of sources on the VCSEL array, said lenslet pattern being scaled to a smaller dimension than the VCSEL source pattern and arranged to receive the divergent laser beams; and the microlens array being arranged so that the lenslet surface of the microlens array is maintained at a distance from the VCSEL array substantially equal to the focal length of the lenslets to substantially collimate the beams and also being maintained in a lateral orientation so that each beam passes through a corresponding microlens in the microlens array causing the laser beam from each VCSEL source to be directed through a common aperture.

VCSEL field correction

In a fine-focus actuator, the lens is coupled to a base by extension members. The extension members are rotatably coupled to the base and extend beyond the base. A counter-weight, positioned on the extension members, provides, in the presence of an external inertial force, a torque balancing the torque imposed on the lens holder by the external force. The counter-weight can include elements of the actuator such as magnets, etc.

Balanced focus actuator for an optical storage system

Apparatus for reading out information magneto-optically recorded in a magnetic layer comprises a single, polarization-preserving optical guide (e.g., an optical fiber or two-dimensional waveguide) for transmitting plane-polarized read-out radiation to the recording layer, as well as for transmitting such radiation, upon being reflected by the recording layer, toward a photodetector. Either the TE or TM axis of the optical guide is initially aligned with the plane of polarization of the readout source. A polarization rotator, such as a Faraday rotator, is positioned between the output end of the optical guide and the recording medium. The Faraday rotator serves to rotate the plane of polarization of the readout radiation by a total of 45 degrees, whereby the optical guide transmits reflected light in both TE and TM modes equally. A pair of photodiodes cooperate with a polarizing beam splitter to differentially detect the Kerr rotation angles (.+-..THETA..sub.k) produced by the up/down orientation of the vertically oriented magnetic domains in the recording layer.

Magneto-optic readout using a polarization-preserving optical guide

Focus and tracking error optical servo detector apparatus is shown employing a single four element detector array. Focus error detection based on spot size sensing is described in which focus error offset caused by beam transition between track and non-track areas is substantially reduced by shaping the detector element areas so as to derive servo signals from substantially only the overlap lobes between the zeroth order diffraction beam and the plus and minus first order diffraction beams in the optical readout beam from the recording element. The readout beam incident on the detector is anamorphically shaped to retain high focus error signal gain while reducing sensitivity in the tracking direction to movement of the beam caused by factors such as thermally induced beam misalignment, vibration and the like. The detector is optionally provided with a polarizer sheet positioned in front of the detector with its transmission axis parallel with the polarization of the beam incident on the recording element for the purpose of blocking birefringence effects on the readout beam from adversely affecting the detector performance.

Focus and tracking error detector apparatus for optical and

Apparatus for playing-back information on a magneto-optic recording element includes a diffraction grating for splitting a read beam reflected from the recording element and modified by the recorded information into three beams. Two of such beams (i.e., the upper and lower first order diffracted beams) are used in a differential detection scheme to recover the recorded information, and the third beam (i.e., the zero order beam) is used to provide focus and/or tracking information.

Magneto-optic playback apparatus including astigmatic diffracting means

A self-focusing optical head of the type used in magneto-optical and optical recording systems for directing a focused laser beam onto a moving recording surface uses a non-achromatized optical path between the laser and recording surface and the laser wavelength (mode) shifts induced by optically coupling reflected laser energy back to the laser cavity to automatically maintain the beam in sharp focus (i.e., self-focus) on the recording surface. A focus servo system including a photodetector positioned in the path of reflected laser energy serves to coarsely position a focusing lens relative to the recording surface. A field lens, used to concentrate reflected laser energy onto the photodetector, is achromatized to compensate for the chromatic aberration between laser and photodetector. Such achromatization allows the focus servo to operate independently of the wavelength (mode) shifts required to achieve self-focusing of the laser beam on the recording surface.

Optical head chromatically optimized for self-focusing

A right-angle optical prism is used to anamorphically shape and deflect by 90.degree. a beam of electromagnetic radiation. Preferably, one of the prism's acute angles is cut at Brewster's angle, and the prism is oriented in the optical path of the beam such that the beam (a) intercepts, at the Brewster angle, that prism face opposite the prism's Brewster angle, (b) is internally reflected by that prism face opposite the prism's other acute angle, and (c) intercepts the prism's hypotenuse face at 90.degree..

Method and apparatus for anamorphically shaping and deflecting

Given a medium comprised of a vertically recordable underlying region of a magnetic material and a cooperating overlying region of horizontally recordable material, the invention calls for the pre-recording of such tracking information, in the underlying region, that between adjacent tracks there occurs a vertically disposed flux reversal in the underlying region, each such track being approximately the width of a playback core disposed to read data recorded in the overlying region. Deposited on the side face of the playback core, in accordance with the invention, is a magneto-resistive element. So long as the playback core is on-track, the magneto-resistive element 'sees' equal vertical fields on either side of the track edge; but should the playback core start to mistrack, the magneto-resistive element will see vertical flux of one or another polarity. Such polarized vertical flux translates into a corresponding resistance change in the magneto-resistive element which, in turn, is employed to correct the mistracking.

Flux sensitive tracking

An optical disk unit, of the kind having a record element and a flexible cover sheet that are attached around an outer periphery in a manner providing an outer spacing and a generally enclosed inter-space therebetween, has an improved construction which significantly reduces the likelihood of contact between the record element and cover sheet. Central spacing means provide a central sheet-to-element spacing that is significantly larger than said outer spacing and vent means, into and out of the inter-space cause a reduction in the spacing between the record portion of the element and the cover sheet during write/read operation. The air flow through the vent means also reduces the formation of visible debris in the enclosed record element/cover sheet inter-space.

Protective construction for optical disk units

Debris suppression is effected in a sealed disk unit, of the kind having a generally enclosed record element/cover sheet inter-space, by controlling the temperature gradient across the inter-space so that thermophoretic forces, exerted by air molecules, drive ablative debris particles toward the cover sheet.

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Fairport, NY, United States of America

Alan B Marchant