Abstract: In general, the mode field pattern of a single-mode polarization-maintaining fiber is symmetric. There are preferred axes for the polarization states, but the intensity pattern emerging from the fiber is rotationally symmetric. If a short piece of multi-mode fiber is spliced onto the end of a polarization-maintaining single-mode fiber, it is possible to change the apparent shape of the mode field. The use of a fusion splicer affects the stress pattern in polarization-preserving fiber, and introduces asymmetry into the shape of the fiber mode field. If the spliced fiber is cleaved near the splice, and the asymmetry of the fiber mode field is matched to the asymmetry of a laser diode beam, then the laser beam is coupled efficiently into the fiber without the use of additional beam-shaping optics. The asymmetric beam from the laser is brought to a focus, which is also asymmetric.

Abstract: Disclosed is a near field optical recording head for use with light from a light source to read data from and to write data to a surface of an optical recording media. The recording head includes a slider body adapted to fly a first distance above the surface of the optical recording media, the first distance being less than one wavelength of the light from the light source. The recording head also includes separate read and write apertures having dimensions which optimize read and write functions, respectively.

Abstract: A system and method for directly measuring the alignment error in a fiber-optic coupler is disclosed. In one embodiment, an optical switch utilizes a beam deflection mirror. When the beam deflection mirror directs an incident light beam to a particular fiber, the incident light beam may enter the fiber at a location offset from the center of the fiber. When the incident beam is reflected at the opposite end of the fiber, the beam returns and exits the fiber exactly at the center of the fiber. The difference between the entry and exit points results in a return beam path different than the incident beam path. This different return beam path may be used to impinge upon a quadrant detector, whose anode currents may then contain a direct measurement of the distance between the entry and exit points on the fiber.

Abstract: A disc drive for performing data operations relative to a disc includes a head positionable near the disc. The head is optically coupled to a light source by optics that direct a light beam from the light source to the head. The optics include a tracking position sensor that has first and second light detectors and a reflective surface. The first and second light detectors are capable of providing first and second electrical signals indicative of the amount of light incident on the respective light detectors. A third light detector is coupled to the optics and is receptive of light reflected from the disc.

Abstract: A slider for an optical read head includes a liquid-immersion-lens between an objective lens and an optically transparent base of the slider. The liquid-immersion-lens includes a high index of refraction liquid, thereby eliminating a lens-air interface at the lower surface of the objective lens. The liquid-immersion-lens provides for the production of a small light spot at the surface of the optical disc.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: In an optical storage system, a non-signal radiation component from a laser unit which is leaves the optical path as a result of selection of a signal polarization component for interaction with the optical storage medium is applied to a first detector. The output electrical signal from the first detector is combined with the output electrical signal from the second detector to which the radiation component, which has interacted with the storage medium, is applied. The two electrical signals are combined in a manner to reduce the noise from the laser unit which is superimposed on the signal from the second detector. In the typical read/write head, the non-signal beam can be the deflected radiation from the beam splitter.

Abstract: In a sensor system for use in the read/write head of an optical information storage and retrieval system, a dual prism separates the resulting radiation beam into two radiation components, the radiation components having a division perpendicular to a projection of a data track or groove on the storage medium projected on the dual prism. Each of the two radiation components is focused by a focus sensor lens on one of two four-quadrant sensors, the four-quadrant sensors forming the system sensor array. The application of the two radiation components generates a tracking signal, a focusing error signal, and a data signal. The orientation of the dual prism results in reduced cross-talk between the tracking signal, which is derived from positive and negative diffraction components, and the focusing signal, which is derived from radiation components having contributions from both the positive and negative diffraction components.