Eastman-kodak Company

Steven C Dohmeier

Edward C Gage

Clarke K Eastman

Roger A Hajjar

Michael E Meichle

Mark V Hettel

James A Barnard

Michael G Fairchild

Jeffrey T Klaus

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

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

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 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

Method for correcting the length of marks and lands representing information taken from an optical disk is disclosed. The method includes digitizing amplified analog data having marks and lands played back from an optical disk and providing a data synchronization clock by using a phase lock loop (PLL). The method further includes providing an adjustment to a threshold signal level based upon the difference in timing position in mark and land edge marks with reference to the data synchronization clock and changing the data mark and land lengths with reference to the adjusted threshold signal.

Correcting recorded marks and land lengths taken from an optical disk

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 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 optical recording system and method which provide verification of recorded data, while the data is being written onto an optical recording medium, by detecting the rate of change of a reflected write pulse. The system includes an optical source for supplying a intensity-modulated incident write signal, having at least one write pulse, to an optical recording medium. The write signal records a logic level of the data on the medium as a mark having a distinct reflectivity. An optical detector detects a reflection of the incident write signal from the medium to provide a reflected write signal which includes a reflected write pulse corresponding to the incident write pulse. The reflected write pulse has a rate of change resulting from a change in reflectivity of the optical medium as the mark is formed thereon. A mark formation effectiveness signal generator receives the reflected write signal and generates a mark formation effectiveness signal which estimates a normalized rate of change of the reflected pulse, to provide an indication of the quality of mark formation on the medium. Comparison means may be included for comparing the measured mark formation effectiveness signal with a predetermined range of acceptable rates of change in order to verify proper mark formation.

Write verification in an optical recording system by sensing mark

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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Rochester, NY, United States of America

Steven C Dohmeier