Eastman-kodak Company

James A Barnard

Boris A Shtipelman

Bruce Ha

Edward C Gage

Clarke K Eastman

Thomas C Burgo

Yuan-Sheng Tyan

Fridrich Vazan

Dennis G Howe

Giuseppe Farruggia

Thomas Richard Cushman

Bruno Primerano

George R Olin

Charles J Simpson

Steven C Dohmeier

Michael G Fairchild

Michael A Inchalik

Tzuo-Chang Lee

A copy-protected optical disc, including a preformed identification number (ID) in the ATIP signal and the subcode which is impressed upon the optical disc and a number of other optical discs during optical disc manufacture, a unique identification number for the optical disc which was written on the optical disc after it is manufactured; and an encrypted program written onto the optical disc wherein the encryption of such program is based upon the preformed ID and the unique ID and includes two or more selectable security levels.

Copy protection using multiple security levels on a programmable CD-ROM

A WORM optical recording element includes a substrate; an amorphous phase-change recording layer disposed over the substrate; a dielectric layer disposed adjacent to the amorphous phase-change layer; a reflector layer disposed adjacent to the dielectric layer; and wherein the material and the thickness of the layers are selected such that recording can be performed on the optical recording element by using a focused laser beam to form crystalline marks in the phase-change layer using laser pulses with less than 40 nS in duration, the reflectivity of the amorphous phase as measured by a collimated beam is higher than 28% and the contrast of the read-back signal is higher than 0.6, and the second and subsequent writing over previous recording results in at least a 50% increase in read out jitter.

Phase-change recording element for write once applications

A hybrid optical recording disc having a substrate and a recording layer disposed over the substrate, the substrate having a read-only (ROM) area in which a groove is modulated by depressions in the substrate and a recordable area in which the groove from the read-only area extends into the substrate in the recordable area. The groove in the read-only area forming wobbling tracks having a depth greater than 170 nm and wherein the depth d of the depression in the groove in the read-only area is in a range greater than 170 nm and less than 350 nm.

Hybrid optical disc construction

A hybrid optical recording disc having a substrate and a recording layer disposed over the substrate, the substrate having a read-only (ROM) area in which a groove is modulated by depressions in the substrate and a recordable area in which the groove from the read-only area extends into the substrate in the recordable area, the groove in the read-only area forming wobbling tracks having a depth greater than 170 nm.

A DRDW differential phase tracking method including the steps of writing marks to a groove on an optical storage media utilizing a write beam; reading the trailing edge of each mark which is in the process of formation by the same write beam; detecting the diagonal signal components from a quadrature photodetector positioned in the path of the write beam reflected from the optical storage media; and forming a tracking error signal either as a function of the difference between the two diagonal signals out of the quadrant detector or as a function of the differential phase between the two diagonal signals out of the quadrant detector.

DRDW differential phase tracking method and apparatus

An optical disc is disclosed having a substrate in which data can be written on or read from, such optical disc has a transparent cover sheet which is held at a desired spacing from the substrate at least at an inner radius and an outer radius. In order to prevent the transparent cover sheet from deflecting due to pressure differences between the outside atmosphere and the air in the space between the substrate surface and the transparent cover sheet, a plurality of air passages in the transparent cover sheet are provided near an inflection point where on one lateral side of the point the transparent sheet will bulge and on the other lateral side it will be depressed due to centrifugal force acting upon air entrapped between the transparent cover sheet and the substrate surface during disc rotation in an optical disc drive. This arrangement equalizes the pressure in the air space between the transparent cover sheet and the substrate surface and the outside atmosphere.

Optical discs with cover sheets and pressure equalization of the

An apparatus and method for providing dynamic tracking error detection and control in an optical recording system in which an incident beam records data on a medium in the form of marks. A diffraction-based mark formation effectiveness (MFE) signal is generated by monitoring a reflected write signal in part of the return beam aperture or in multiple zones of the return beam aperture and is indicative of a characteristic of the marks formed on the medium. A position signal is generated to provide an indication of cross-track movement of the incident beam relative to a tracking structure on the medium. The tracking structure may be a wobbled groove on an optical disk recording medium. Variations in the diffraction-based MFE and position signals are correlated to provide a dynamic tracking error signal (TES). The diffraction-based MFE and position signal variations may be correlated by, for example, multiplying the two signals together in a multiplier circuit, or using the position signal to control application of the diffraction-based MFE signal to particular inputs of a signal difference circuit. The dynamic TES may be utilized in a servo loop with or without a push-pull signal or other conventional tracking signal.

Dynamic tracking control in an optical recording system by

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

An optical disc is disclosed having a substrate in which data can be written on or read from, such optical disc being adapted to be inserted and clamped onto a spindle in a disc drive and having a transparent cover sheet disposed over the substrate surface. The cover sheet is held at inner and outer radii so that it is positioned to have a desired spacing from the substrate to prevent contaminants from passing to the substrate surface. A plurality of air passages are formed in the optical disc to prevent the transparent cover sheet from deflecting due to pressure differences between the outside atmosphere and the air in the space between the substrate surface and the transparent cover sheet.

Air sandwiched optical discs with closable pressure relief holes

An optical disc having a substrate in which data can be written on or read from, such optical disc being adapted to be inserted and clamped onto a spindle in a disc drive and having a transparent cover sheet disposed over the substrate surface. The optical disc has a perimeter ring on the edge thereof and a spacer formed adjacent to a central opening in the disc. The perimeter ring is formed with a plurality of air passages leading from the space between the transparent cover sheet and the substrate surface to the outside atmosphere and the spacer is formed with a plurality of air passages leading from the outside atmosphere to the space between the transparent cover sheet and the substrate surface. Filters are provided in the air passages in the spacer and the perimeter ring to prevent contaminants from the atmosphere from entering into the space between the transparent cover sheet and the substrate surface.

Optical discs with cover sheets and dynamic pressure stabilization of

A focus/tracking actuator for controlling the respective focus and tracking positions of a lens used to direct a focused beam of radiation onto a desired data track on a moving recording element comprises a pair of moving coil-type linear motors. Each of the motors comprises a coil of wire disposed in a magnetic air gap and adapted to move therein in response to an applied current flow. According to the invention, the respective masses of the motor coils are optimized to achieve maximum acceleration with minimum power comsumption. Preferably, the coils have a combined mass substantially equal to the mass of the moving payload, which includes the lens assembly and its movable support.

Optimized linear motors for focus/tracking actuators in optical disk

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

A focus/tracking actuator for an optical or magnetooptical disk drive includes a pair of moving-magnet type linear motors for simultaneously controlling the focus and tracking positions of an objective lens used to focus a write/read beam on a desired data track of a rotating data storage disk. Each motor includes a pair of selectively energizable focus and tracking coils, one coil being positioned within the other so that its respective windings are perpendicular to those of the other coil. Flux lines emanating from a permanent magnet secured to a movably mounted lens housing interact with the electromagnetic fields surrounding both coils, and a single steel plate or the like, positioned inside the windings of both coils, facilitates the return of magnetic flux to the magnet while preventing such flux from cutting portions of the coils which would act to exert an undesired forces on the lens housing. Preferably, the steel plate is composed of two segments to facilitate winding of the coils about the plate.

Focus/tracking actuator with moving-magnet motors

An optical tape recording medium is provided with a transparent flexible membrane which covers the recording surface of the tape and is bonded to its edges so as to trap a small bubble of fluid, e.g., gas or liquid. During recording, the trapped bubble displaces dust particles resting on the film's upper surface to a location out of the zone of focus of a read/write beam. As the tape is longitudinally transported, the trapped bubble is held stationary at the read/write station of the recording apparatus. In a tape cassette, the optically writable tape is wound around two reels with sufficient tension to trap the bubble in that portion of the tape stretched between the supply and take-up reels. In one embodiment of the invention, the bubble contains a transparent magnetic liquid which can be properly positioned by a magnet when the cassette is first inserted into an optical recording or playback apparatus. The invention is generally useful with any optically writable media, including optical and magneto-optical write/read media.

Optical tape recording media with integral dust-defocusing transparent

Apparatus for reading out information magneto-optically recorded in a magnetic layer comprises a single, polarization-preserving optical fiber for transmitting plane-polarized readout radiation from a source to the recording layer, as well as for transmitting such radiation, upon being reflected by the recording layer, toward a pair of photodetectors for the differential detection of the Kerr rotation angles (.+-..THETA..sub.k) produced by the up/down orientation of the vertically oriented magnetic domain in the recording layer. Optical feedback of the reflected readout radiation to the readout source is minimized by the provision of a pair of polarization beam-splitters having a 45 degree magneto-optic polarization-rotator (e.g. a Faraday rotator) positioned therebetween. The polarization beam-splitters and retardation plate are positioned in the optical path between the readout source and the optical fiber.

Growing community of inventors

Scottsville, NY, United States of America

James A Barnard