International Business Machines Corporation

Spencer D Roberts

Alan A Fennema

Ian E Henderson

Ronald J Kadlec

Karl Arnold Belser

Arvind M Patel

John Alexander Koski

William W Chow

Benjamin C Fiorino

Rudolf W Lissner

Paul J Dounn

John J Eige

David Stedman

The focus acquisition system on optical disk recorder as well as other optical systems, uses repeated pulse position pulses with interlead coasting of an objective lens for providing a soft focus acquire. The pulse energization of the lens to move toward an in-focus condition overcomes stiction and friction. While the coasting allows the energy level applied to the lens movement to be minimal, i.e. soft, the purpose of the interdirectional pulse control actuation is to overcome friction without requiring large power to the lens which can cause an overshoot of the lens at the in-focus position. Compensation techniques and stopping the lens at the in-focus position are also shown.

Acquiring focus in an optical system using a soft focus acquiring system

A track-seeking apparatus of a disk recorder employs a track-crossing sensor to produce track-crossing signals. An oscillator is slaved to the sensor for supplying substitute track-crossing pulses in the absence of the sensor providing such pulses or when the radial velocity exceeds a threshold velocity. A velocity profile means alters the oscillator frequency so that the oscillator produces track-crossing pulses in accordance with the profile.

Positioning systems including reliable track crossing detection for high

A track-seeking system for an optical disk using a velocity control loop with partially-digitized velocity measurement. A quadrature signal is generated based on summing the halves of a position error signal to give directionality to track-crossing counts. A so-called piggy-back construction, wherein a fine positioner is carried by a coarse positioner, is employed. Feed-forward controls are provided from the fine to the coarse positioner. At track-capture time, the dynamic range of the fine positioner is momentarily increased.

Transducer positioning servo mechanisms employing digital and analog

High tape acceleration rates are achieved in an unbuffered, capstanless tape drive system by a tape motion control apparatus employing separate drive motors for each reel of a reel-to-reel tape transport. Tape moves from one reel past a read/write head and a tape tension sensor to the other reel, there being no tachometer in the tape feed path. A tachometer on one reel shaft provides a large number of pulses per revolution which pulses are counted by a counter; and a tachometer on the other reel shaft provides only one pulse per revolution, which pulse gates out the count then accumulated in the counter for actuating means to provide motor acceleration currents of a magnitude corresponding to said accumulated count according to a predetermined servo algorithm for controlling rotation of both reels. A tape radius constant corresponding to the actual length and thickness of tape in the system is calculated during initial wrap of tape onto the takeup reel. Tension is tightly controlled by an analog tension sensor and servo system.

Tape motion control for reel-to-reel drive

A reel-to-reel web (tape) transport apparatus which has no tape length buffering between the supply and take-up reels. The tape follows a fixed length path from the supply reel, past a read/write head and guides, to a take-up reel. A two motor control mechanism is employed in which one motor drives the take-up reel and one motor drives the supply reel to maintain the appropriate tension and tape motion at the read/write head. The control mechanism is adaptive to dynamic changes as the tape is moved from the supply reel to the take-up reel. Three quantities are monitored: lineal tape position and the angular reel displacement of the supply and take-up reel. From these quantities reel radii are derived, tape inertia calculated and the velocity or position error is determined. A motor current algorithm is utilized to generate the appropriate torque for each reel to drive the control error to zero along a predetermined profile with negligible tape tension disturbances. The result is a reel-to-reel tape drive with static and dynamic performance characteristics which are independent of reel radius and inertia changes resulting from tape motion.

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Tucson, AZ, United States of America

Spencer D Roberts