Eastman-kodak Company

Edward C Gage

Steven C Dohmeier

Clarke K Eastman

Roger A Hajjar

David B Kay

James A Barnard

Randall H Victora

Mark V Hettel

Boris A Shtipelman

Ronald E Gerber

A recording apparatus and method are disclosed for forming marks on a recording medium. The recording apparatus includes an arrangement having an adjustable light source for producing a beam of light having first and second portions, with the second portion for recording marks on the medium, and an arrangement responsive to the first portion of the light beam and including a front facet detector positioned to receive the first portion of the light beam directly from the light source for producing a front facet signal. The recording apparatus also includes an arrangement for detecting light from the second portion of the light beam which is reflected from the medium and for producing a mark formation signal, and circuitry responsive to the front facet signal and the mark formation signal for producing a mark formation effectiveness signal. The recording apparatus further includes an arrangement for storing a mark formation effectiveness reference signal and circuitry responsive to the mark formation effectiveness signal and the mark formation effectiveness reference signal for adjusting the power of the light source during recording so that the amount of power is adjusted to maintain optimum mark quality.

Direct read during mark formation for laser power correction

Apparatus for optically writing information on or reading information from a disc having tracks includes a carriage moveable in a radial direction relative to the disc tracks and at least first and second optical heads spaced and mounted on the carriage; the first and second optical heads being moveable with the carriage, and at least one of the heads being pivotally mounted; and the first head being adapted to write information on a track of the disc, the second head being adapted to read information and produce a signal representative of recorded data. The apparatus further includes a structure connected to the pivotally mounted head and adapted to pivot the optical head as the carriage is displaced in the radial direction so that both the first and second optical heads are spaced from each other but aligned on the same track within the tracking ability of the head, and an arrangement responsive to the read head signal to adjust operation of first head during writing to improve the recording of data.

Multihead optical disc drives with direct reading after writing operation

A magneto-optic head for reading and writing information on a magneto-optic recording medium so that diffraction effects can be monitored during writing is disclosed. The magneto-optic head includes a source of laser light for projecting a laser light beam during writing and reading, a first partial polarizing beamsplitter disposed in the beam of light for causing one beam of light to be transmitted to the recording medium and for receiving reflected light and for projecting such light in a first direction, a second polarizing beamsplitter for receiving polarized light in the first direction from the first partial polarizing beamsplitter and projecting such polarized light in second and third directions, a first detector for receiving light in the second direction from the second polarizing beamsplitter and a second detector for receiving light in the second direction from the second polarizing beamsplitter, each detector including at least two photosensitive elements being split in the in-track direction so that in-track diffraction effects can be determined.

Diffraction-based direct read during write using magneto-optic recording

Apparatus for reading data from an optical medium having improved settling time characteristics and reduced bandwidth requirements is disclosed. The apparatus includes a front facet detector for producing a front facet monitor signal from a laser light beam; first and second detectors for producing first and second data signals, respectively; and a first gain control circuit responsive to the front facet monitor signal to produce a gain adjusted front facet monitor signal. The apparatus further includes a second gain control circuit responsive to the first data signal and the gain adjusted front facet monitor signal to produce a first gain adjusted data signal; a third gain control circuit responsive to the second data signal and the gain adjusted front facet monitor signal to produce a second gain adjusted data signal; circuitry responsive to the first and second gain adjusted data signals to produce a magneto-optic data signal as a function of the difference between the first and second gain adjusted data signals; or to produce a combined data signal as a function of the sum of the first and second gain adjusted data signals and responsive to the gain adjusted front facet monitor signal and the combined data signal to produce a write-once data signal as a function of the difference between the gain adjusted front facet monitor signal and the combined data signal.

Bandwidth reduction in writeable optical data storage apparatus

An apparatus for producing a tilt error signal representative of the tilt of an optical disk is disclosed. The apparatus includes a source of laser light for focusing a laser beam onto the disk and reflecting such beam from the disk, a beamsplitter positioned to receive the reflected light beam and to direct the light beam in a first direction, and a structure for separating the reflected light beam from the beamsplitter into at least four portions and for producing detection signals for each portion. The apparatus further includes circuitry responsive to the detection signals for producing first and second tracking error signals, the first and second tracking error signals being produced by different combinations of the detection signals and both being sensitive to cross-track diffraction, and circuitry responsive to the first and second tracking error signals for producing the tilt error signal.

Tilt error signal producing apparatus using multiple tracking error

A method for reading data from an optical medium having improved settling time characteristics and reduced bandwidth requirements, including producing a gain adjusted front facet monitor signal from a laser light beam, producing first and second data signals from data read from the medium, and producing first and second gain adjusted data signals in response to the gain adjusted front facet monitor signal and first and second data signals, respectively. The method further includes producing a magneto-optic data signal in response to the first and second gain adjusted data signals, the magneto-optic data signal being a function of the difference between the first and second gain adjusted data signals; or producing a combined data signal in response to the first and second gain adjusted data signals, the combined data signal being a function of the sum of the first and second gain adjusted data signals, and producing a write-once data signal in response to the gain adjusted front facet monitor signal and the combined data signal, the write-once data signal being a function of the difference between the gain adjusted front facet monitor signal and the combined data signal.

Method for bandwidth reduction in writeable optical data storage

An optical drive apparatus for use with a multilayer optical data storage device, includes: at least two spaced apart storage layers, each of such layers being adapted to store information; a spacer layer positioned between alternating storage layers; at least one of the storage layers including tracking and/or format information, while another storage layer does not include tracking and/or format information; and writing apparatus including a plurality of radiation beams arranged such that at least one beam is focused on a layer with tracking and/or format information and provides tracking and/or format information to at least one other beam that is focused on a layer to be written that does not have substantial tracking and/or format information.

Optical drive apparatus for use with a multilayer optical data storage

An optical recording system for recording data on an optical medium comprising: an optical source capable of providing at least one write pulse incident upon the optical medium; a direct read during write (DRDW) verification and control system within the optical source having a capability of measuring light reflected from the optical medium into a return beam aperture, the DRDW system including a plurality of detectors configured to receive light from different areas of the return aperture; and a comparison circuit for comparing light received in different portions of the return aperture.

Phase detected direct read during write

A multilayer optical data storage device is disclosed which has at least two spaced apart storage layers, each of such layers being adapted to store information; a spacer layer positioned between alternating storage layers; and at least one of the layers including tracking and/or format information, and at least one storage layer that does not include substantial tracking and/or format information.

Multilayer optical data storage device

An apparatus and method for detecting a data signal read from a magneto-optic (MO) storage medium. First and second detected signals are generated from first and second portions, respectively, of a radiation beam reflected from the medium. First and second gain control circuits are coupled to the first and second detectors, respectively. Each of the gain control circuits is operative to alter the gain of a signal path of the corresponding detected signal in response to a control signal which varies in accordance with a difference between the corresponding detected signal and a reference signal. The reference signals in each gain control circuit may be a common reference voltage level. A signal difference circuit produces a data signal corresponding to the difference between the detected signals.

Magneto-optic data storage system with differential detection channels

An apparatus and method for providing a tracking error signal in an optical system in which a radiation beam is applied to an optical storage medium having a number of marks formed thereon. A return beam resulting from application of the incident radiation beam to the medium is separated into a first polarization component and a second polarization component. First and second detectors detect the first and second polarization components and generate first and second detected signals therefrom. A tracking error signal is generated from the first and second detected signals, and is responsive to variations in the return beam arising from diffraction of the incident beam from, for example, cross-track edges of the marks on the medium. The marks may be previously-recorded data marks or preformatted tracking marks, and the medium may be a non-grooved magneto-optic medium.

Apparatus and method for differential tracking in a magneto-optic data

An apparatus and method for providing tracking and focus error signals for controlling an application of a radiation beam to a data track of an optical storage medium. A data signal, indicative of the data stored on the storage medium, may also be provided. One apparatus in accordance with the present invention includes an optical source to generate a radiation beam; a transparent substrate arranged between the optical source and an optical storage medium; and a grating beam splitter formed on a surface of the substrate and having first, second, third and fourth grating elements for separating a return beam reflected and diffracted from the data track into first, second, third and fourth portions, respectively. In other embodiments, more or less than four grating elements and return beam portions could be used. The portions of the return beam are directed onto a detector array. The first and second grating elements separate the return beam along a plane substantially parallel to a reference plane defined by an optical axis of the radiation beam and a tangent to the data track, and the resulting first and second portions may be used to generate a tracking error signal. The third and fourth grating elements, arranged on opposite sides of and adjacent to the first and second grating elements, separate the return beam along a plane substantially perpendicular to the reference plane, and the resulting third and fourth portions may be used to generate a focus error signal. The optical source, transparent substrate, grating beam splitter and detector array are part of an LDGU contained within a single package.

Read/write laser-detector-grating unit (LDGU) with an

An apparatus and method for providing differential detection and source noise subtraction in data signals read from magneto-optic (MO), write-once (WO) or other types of optical storage media using an incident radiation beam. A source monitor signal is generated by detecting radiation from an optical source providing the radiation beam. An error detector generates an error signal corresponding to a difference between the source monitor signal and a reference signal. A power level of the radiation beam is adjusted in response to the error signal. A data signal generator is adapted to receive a return beam resulting from application of the radiation beam to the medium and to generate a WO data signal from the return beam. A signal combiner combines the data signal and the source monitor signal to provide a compensated WO data signal. An MO data signal may be generated using a separate AGC circuit to adjust the gain of each differential detection channel in accordance with low-frequency amplitude differences between the detected signals and a reference signal. The same reference signal may be used in both the source noise subtraction and the MO data signal generation.

Optical data storage system with differential data detection and source

An apparatus and method for providing a sampled tracking error signal in an optical system using multiple illumination spots. An optical source generates radiation which is applied to a storage medium to produce a first illumination spot, a second illumination spot and a third illumination spot thereon. A return beam resulting from application of the radiation to the medium is detected, and a data signal is generated from the detected return beam. A sampled tracking error signal is generated from a first sample of the data signal, taken when the second spot illuminates a portion of a tracking mark, and a second sample of the data signal, taken when the third spot illuminates another portion of a tracking mark. The data signal samples may be normalized to samples of a source monitor signal. The data signal may be generated from magneto-optic, write-once, or other types of optical storage media.

Apparatus and method for multi-spot sampled tracking in an optical data

An apparatus and method for reducing optical source noise and other common-mode system noise in a data signal read from an optical storage medium. An exemplary apparatus in accordance with one aspect of the present invention includes a first detector to generate the data signal by detecting a return beam resulting from application of a radiation beam to the medium; a second detector to generate a source monitor signal by detecting radiation from an optical source providing the radiation beam; a correction circuit adapted to receive the data signal and the source monitor signal and generate a corrected data signal therefrom; and means for controlling the gain of a signal path of at least one of the data signal and the source monitor signal in response to, for example, low-frequency amplitude differences between the data signal and the source monitor signal. One or more delay lines may be included to provide phase matching of the data signal and source monitor signal at the correction circuit input.

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Fairport, NY, United States of America

Edward C Gage