International Business Machines Corporation

Delbert A Hansen

Timothy S Gardner

Ronald P Stahl

Nhan Xuan Bui

Tomoaki Kimura

Keith A Bates

A magnetooptical disk recording device has a far-field detector for detecting radial position of a laser beam with respect to tracks on the disk. The far-field detector has a reference line dividing first and second photo detectors. The reference line is centered radially with respect to center lines of the tracks. The reference line is also center lengthwise to be tangentially center with respect to a tangential point on the track. The detector is adjustable both radially and tangentially. The tangential adjustment is based upon sensing two low reflective calibration marks on the disk that indicate centering the laser beam, hence the track tangent point, on the reference line. The calibration is based upon obtaining minimum noise in the detector output signal that signifies that the laser beam is centered on the length of the detector reference line. The calibration marks are in a mirror area disposed at one radial extremity of the disk. The marks are radially elongate and disposed in a radially outward diverge with respect to each other. The marks are disposed at 45 degrees with respect to two circumferentially spaced apart radial lines of the disk.

Calibrating an optical detector to minimize noise from undesired

Optical disk with marks used for calibrating an optical detector to

A coarse position sensor is provided for an optical recording device to generate a substantially linear coarse position signal, indicative of the position of a coarse carriage along the range of its travel, and which also is substantially immune to environmental and device variations. The sensor includes a light source mounted to a drive frame at one end of the range of travel, a position sensitive device fixed to the frame at the opposite end of the range of travel and facing the light source, and a deflecting optical element mounted to the coarse carriage in the path of the light. As the coarse carriage travels along its stroke between the inner and outer diameters of the optical disk, the amount of deflection of the light beam on the position sensitive device from a reference location will change. Based upon a trigonometric equation, a coarse position signal generator receives the output of the position sensitive device and generates a substantially linear coarse position signal indicative of the position of the coarse carriage.

Coarse position sensor, and method for locating same, in an optical disk

A circuit for electronically compensating for optical and mechanical instabilities induced into the focus control and tracking control servo circuits of an optical disk apparatus. The circuit contains a filter and a variable gain amplifier for passing a tracking error signal compensation component at a selected frequency within the range of frequencies in which mechanical resonance is significant and at a magnitude equal to the focus error signal component at that frequency. The result is the electronic elimination of optical feedthrough at mechanically resonating frequencies. A calibration circuit establishes the compensation component magnitude for each optical disk inserted into the apparatus.

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Tucson, AZ, United States of America

Delbert A Hansen