Abstract: A switchable liquid crystal diffractive element for use in an optical drive capable of reading multiple tracks of an optical disk simultaneously, and writing or erasing at least one track of the optical disk is disclosed. When the liquid crystal diffractive element is in an “on” state, it splits an incident beam into multiple beams suitable for simultaneously reading multiple tracks of an optical disk. When the liquid crystal diffractive element is in an “off” state, it permits an incident beam to pass through without being split, for writing to an optical disk. Embodiments are disclosed that use multiple electrodes to create switching and non-switching regions of a liquid crystal element to form a switchable phase grating, and that use a single switching liquid crystal element and a non-switching grating, or a birefringent non-switching grating, to form a switchable diffractive element.

Abstract: The present invention provides an optical system having a read mode, during which multiple tracks of an optical disk are simultaneously read, and a write mode, during which data is written to at least one track of the optical disk. The multiple light beams employed during read mode may be generated by a single laser diode operated at low power used in combination with a diffractive element, multiple laser diodes, or combinations thereof.

Abstract: A focus detection system for use in a multi-beam optical pickup assembly is provided that uses an optical element, either a holographic element or diffractive element, to split beams reflected off of a data-bearing surface of an optical disk into a plurality of data beams and a plurality of focus beams. The optical element also introduces astigmatism into the focus beams. The focus beams are projected onto focus detectors configured to account for overlap between adjacent focus beams to produce an accurate focus error signal.

Abstract: Methods and apparatus are provided for illuminating an optical disk in a multi-track optical disk reader. A laser beam is collimated and focused onto an area including multiple, adjacent data tracks on the optical disk. To minimize noise caused by interference resulting from the reflection of multiple beams from the optical disk the coherency of the laser beam is reduced. This is accomplished by one or more of the following techniques: passing the laser beam through a multi-mode optical fiber, combining laser beams from multiple independent laser sources, and modulating the laser operating current at high frequency.

Abstract: Methods and apparatus are provided for improving optical drive access times using a detector having multiple sensing elements to sense and count disk tracks. The detector may be oriented either radially or tangentially with respect to the disk radius, and either capable of sensing more than one disk location simultaneously or have a length greater than the maximum distance between detectable features of the disk.

Abstract: Focussing system methods and apparatus are provided for apparatus capable of simultaneously reading multiple tracks of an optical disk. Astigmatism introduced by a cylindrical lens disposed adjacent to the light source, or before the focus detectors arranged at the edge of a wide-area field of illumination, is used to compute an error signal corresponding to the degree of out-of-focus, which error signal is provided to a servo-system that moves the objective lens to correct the focus. An alternative embodiment employs a pair of focus detectors and a pair of micro-lenses having different focal lengths that directs the reflected light onto the focus detectors to generate a focus correction signal. Further alternative embodiments of employing the astigmatism method of focussing are described.

Abstract: Focussing system methods and apparatus are provided for apparatus capable of simultaneously reading multiple tracks of an optical disk. Astigmatism introduced by a cylindrical lens disposed adjacent to the light source, or before the focus detectors arranged at the edge of a wide-area field of illumination, is used to compute an error signal corresponding to the degree of out-of-focus, which error signal is provided to a servo-system that moves the objective lens to correct the focus. An alternative embodiment employs a pair of focus detectors and a pair of micro-lenses having different focal lengths that directs the reflected light onto the focus detectors to generate a focus correction signal. Further alternative embodiments of employing the astigmatism method of focussing are described.

Abstract: A method of reading data from an optical disk comprises providing means for illuminating the required part of the disk and acquiring the optical image of a plurality of tracks, providing a detector matrix comprising a plurality of detectors, each of the detectors being capable of producing an output signal which is proportional to the intensity of the light detected by it causing an optical image corresponding to an illuminated area to fall on the detector matrix, transferring the output signal of the detector matrix to image processing means, determining position coordinates of the track center for each data track, by analyzing the output signal of the detector matrix, saving in memory means expected track center data, comprising position coordinates of the track center located by the analysis of the output signal, and if an actually detected track center is shifted with respect to the expected track center, electronically moving the track center position.

Abstract: A method of writing data simultaneously on a plurality of tracks of an optical disk, comprises providing an array of light sources, each light source being independently modulated, providing means to determine the position of each light source with respect to the center of a given track, and varying the intensity of each light source so as to generate a plurality of writing light beams, each generated by a plurality of adjacent light sources, each of the said light beams having the desired width, intensity and position on the written track.

Abstract: A method of reading data from an optical disk comprises providing means for illuminating the required part of the disk and acquiring the optical image of a plurality of tracks, providing a detector matrix comprising a plurality of detectors, each of the detectors being capable of producing an output signal which is proportional to the intensity of the light detected by it causing an optical image corresponding to an illuminated area to fall on the said detector matrix, transferring the output signal of the detector matrix to image processing means, determining position coordinates of the track center for each data track, by analyzing the output signal of the said detector matrix, saving in memory means expected track center data, comprising position coordinates of the track center located by the analysis of the output signal, and if an actually detected track center is shifted with respect to the expected track center, electronically moving the track center position.

Abstract: An optical disk reader system comprises (1) a wide area illumination source for illuminating at least a part of one track of an optical disk; (2) a detector for detecting light reflected from the optical disk illuminated by the wide area illumination source; and (3) a detector for summing the light in the along-track direction detected by the detector.

Abstract: A method of reading data from an optical disk comprises providing means for illuminating the required part of the disk and acquiring the optical image of a plurality of tracks, providing a detector matrix comprising a plurality of detectors, each of the detectors being capable of producing an output signal which is proportional to the intensity of the light detected by it causing an optical image corresponding to an illuminated area to fall on the said detector matrix, transferring the output signal of the detector matrix to image processing means, determining position coordinates of the track center for each data track, by analyzing the output signal of the said detector matrix, saving in memory means expected track center data, comprising position coordinates of the track center located by the analysis of the output signal, and if an actually detected track center is shifted with respect to the expected track center, electronically moving the track center position.

Abstract: A method of reading data from an optical disk comprises providing means for illuminating the required part of the disk and acquiring the optical image of a plurality of tracks, providing a detector matrix comprising a plurality of detectors, each of the detectors being capable of producing an output signal which is proportional to the intensity of the light detected by it causing an optical image corresponding to an illuminated area to fall on the said detector matrix, transferring the output signal of the detector matrix to image processing means, determining position coordinates of the track center for each data track, by analyzing the output signal of the said detector matrix, saving in memory means expected track center data, comprising position coordinates of the track center located by the analysis of the output signal, and if an actually detected track center is shifted with respect to the expected track center, electronically moving the track center position.

Abstract: A method of reading data from an optical disk comprises providing means for illuminating the required part of the disk and acquiring the optical image of a plurality of tracks, providing a detector matrix comprising a plurality of detectors, each of the detectors being capable of producing an output signal which is proportional to the intensity of the light detected by it causing an optical image corresponding to an illuminated area to fall on the said detector matrix, transferring the output signal of the detector matrix to image processing means, determining position coordinates of the track center for each data track, by analyzing the output signal of the said detector matrix, saving in memory means expected track center data, comprising position coordinates of the track center located by the analysis of the output signal, and if an actually detected track center is shifted with respect to the expected track center, electronically moving the track center position.