International Business Machines Corporation

Alan A Fennema

Nhan Xuan Bui

Allen Keith Bates

William W Chow

Tetsuo Semba

Ronald J Kadlec

Benjamin C Fiorino

Reed Alan Hancock

Edwin Ralph Childers

Ian E Henderson

Spencer D Roberts

Robert A Klem

Daniel James Winarski

Glen Alan Jaquette

Wayne Isami Imaino

Brian Gerald Goodman

Raymond Yardy

Hal Jervis Rosen

Blair I Finkelstein

Morovat B Tayefeh

Yoshihiro Hirasaka

Julian Lewkowicz

Timothy S Gardner

Lawrence D Tipton

David P McReynolds

Francisco Antonio Baca

James J Dente

William O Wightman, Jr

Jesse L Campbell

William G Rance, Jr

Paul H Whittington

Robert B Henderson

Joseph H DiMatteo

W Wai-Chung Chow

Dave P McReynolds

Enrique E Aviles

The invention provides a system for compensating for hard sector noise degradation of tracking error signals in an optical data storage system. The system includes a hard sector detection circuit which generates a first output signal in response to receiving a first input signal representing detection of a hard sector on a magneto-optical disk; a logic circuit which generates a second output signal in response to receiving the first output signal and a second input signal; and a tracking error signal reconstruction circuit which generates an approximated tracking error signal in response to receiving a tracking error signal and the second output signal. The invention may be embodied as hardwired circuitry or as a combination of hardware and software embodied in a computer readable medium and implemented in a digital computer.

System for compensating for hard sector noise degradation of tracking

A method for cancelling optical servo crosstalk within an optical disk drive is disclosed. In accordance with the method and system of the present invention, the optical disk drive system includes a focus control module, a tracking control module, a variable frequency notch filter, and a lookup table. The focus control module is utilized for moving an objective lens in response to a focus error signal in order to maintain a laser beam in an in-focus condition on an optical disk. The tracking control module is utilized for moving a moving optical element in response to a tracking error signal to direct the laser beam onto a desired track position of the optical disk. The lookup table within the focus control module is utilized for storing several sets of tap coefficients for the variable frequency notch filter. An appropriate set of tap coefficients from the lookup table is supplied to the variable frequency notch filter in response to a head velocity signal from the tracking control module such that the effects caused by a false FES in the optical disk drive system are reduced.

Method and sytem for cancelling optical servo crosstalk in optical disk

An optical disk drive with a multiple data layer optical disk uses computed axial velocity values of the data layers to optimize the interlayer transition of the focused light beam. In the preferred embodiment, the axial velocities of the data layers are computed for a set of radial and angular positions on the data layer surfaces using one of several techniques. The data layer axial velocity values are computed from the measured current values to the voice coil motor focus actuator or from the output of the detector that generates the focus error signal (FES). A routine is run at disk drive startup, or at various times during disk drive operation, to measure the coil current or FES at different radial and angular positions and compute the axial velocity values. The computed axial velocity values are then mapped into memory storage according to addresses corresponding to their radial and angular positions. When it is desired to move the focused light beam from one data layer (the initial or take-off data layer) to another data layer (the final or target data layer) the computed axial velocity values are retrieved for the radial and angular positions nearest the take-off and target sectors on the respective data layers. These velocity values are then used to modify the acceleration profile of the focusing lens so that the focused light beam arrives at the desired position on the target data layer with a velocity close to the target data layer axial velocity.

Optical disk drive with multiple data layer disk and system for focusing

In an optical disk recorder, during the sensing of closely-spaced, position-indicating, machine-sensible indicia, a first peak of a track error signal is detected. In response to the first peak being detected, a half-track counter is decremented from a value which depends upon the position of the destination track relative to a current track. In response to the occurrence of a selected value of the half-track counter and the presence of a zero crossing of the tracking error signal, a first timer is activated to mask any defects occurring during the selected first half cycle of the last cycle of the tracking error signal. The half-track counter is again decremented in response to a second peak being detected and the occurrence of a next-to-last zero crossing of the tracking error signal and a second timer is then activated to mask any subsequent defects occurring during the second half cycle of the tracking error signal. The seek operation is terminated when the count value in the half-track counter equals zero and a final zero crossing is detected. Thereafter, a track following operation is activated.

Masking of tracking error signal abnormalities due to media defects

A relative position error signal is calibrated in an optical storage device in which a tracking error signal (TES) varies as the light beam shifts its position through the objective lens. The calibration is performed by moving the coarse carriage to a predetermined region of the optical disk and measuring the TES. The fine actuator is adjusted until the tracking error signal equals a predetermined value. Then, the relative position error signal is read and an adjustment to the RPE gain is calculated to bring the gain to a predetermined value. The adjusted gain is used during normal disk access operations.

Relative position sensing calibration for optical storage device

A rotary positioner is rotatably mounted upon a reciprocating carriage of a optical disk drive. To detect and indicate one of a plurality of possible orientations of the disk drive, a side bias force is applied to the rotary positioner in a direction orthogonal to the radius of the disk drive. It has been found that each orientation has a side bias at which gravity effects are removed from the rotary positioner. At these points of gravity accommodation, certain instabilities in servo operation occur. Since each orientation requires a different side bias force to create the respective servo instabilities, the side bias force causing such instability indicates the drive orientation. Two modes of testing for orientation are disclosed. The carriage positioner is actuate for causing a momentary uncorrected radial movement of the carriage. The response of the carriage servo is measured in one of two ways. The uncorrected momentary carriage motion is detected either by detecting changes in a position error signal of either the rotary position or the carriage.

Apparatus and method for detecting physical orientation of a position

A single loop servo is used for positioning a lens holding element with respect to an optical disk. The dynamic range of the error signal used in the positioning is dynamically frequency shifted such that the servo summing of the error signal with a reference signal (velocity reference) is always performed within the same dynamic range. This action simplifies circuit operation as the dynamic range of the error signal is compressed at high speeds. Two embodiments of the invention are described.

Single loop servo-positioning systems having means for changing the

The focus acquire system on optical disk recorder as well as other optical systems, signal processes a focus error signal FES to produce a modified FES which has a peak amplitude occurring closer to a desired focus position than the occurrence of peak amplitude of the FES. The modified FES also is signal processed to sharpen or slim the peak portion such that increasing the amplitude of the modified FES reaches an amplitude detection threshold closer to the true peak of the modified FES, and hence closer to the desired focus position than if the amplitude detection threshold were used on the FES. In a preferred form of the invention, FES is differentiated to produce a differentiated FES, then the differentiated FES is subtracted from FES to produce the modified FES.

Acquiring focus in an optical disk system using a time and shape

An optical disk recorder has a fine actuator which holds an objective lens and which is movably mounted on a head carriage. Servo systems connected to the head carriage and the fine actuator cause the fine actuator to seek and track follow based upon signal recovered from a disk while the head carriage is caused to follow the motions of the fine actuator. A tracking error signal is generated indicating the relationship of the beam supplied through the objective lens with respect to tracks on the record medium. An RPE signal (relative position error) is generated by an RPE detector which indicates the relationship of the relative motion of the fine actuator to the head carriage. Both the RPE and TES are calibrated as to offset and as to gain for providing a more precise servo positioning system.

Operating optical disk drives including calibrating a tracking error

A focus acquisition system includes providing a focus offset and changing the offset symmetrically for each measurement cycle. The amplitudes of the readback or tracking error signal are sensed and compared. When the amplitudes of the tracking error or readback signal is different at each of the offsets, then a new measurment cycle is performed after calculating a new offset value. The process is repeated until the temporary measurement offsets result in readback amplitudes that are substantially equal. A best focus is then indicated as being a position in which small defocussing will not substantially degrade the quality of the readback signal.

Acquiring a best focus using a focus signal offset

A servo positioning system, such as used in an optical disk or other types of disk drives includes focus and positioning servo circuits. When a focus error is detected, then it is desired to stop the operation of the positioning system. Similarly, when a positioning error is detected, such as excessive speed or a non-zero velocity at the end of a seek or positioning motion, the head carriage should also be stopped. The stopping of the head carriage is by dynamic braking through use of a power amplifier which is switched from a transconductance mode used during normal servo positioning operations to a voltage amplifying mode which is set to a zero input for dynamically braking the servo positioning system to a safe speed and thence to a stop condition whereupon further error recovery procedures may be employed.

Anti-skating control of a positioning servo system

An optical disk recorder includes disk reflectance calibration means for measuring variations in disk reflectance over the recording area of the disk. Correction factors based on measured reflectance for adjusting sensed signal level and gain reduce the effects of varying reflectance on the sensed signal. In a preferred embodiment, the sensed signal is employed as a signal in quadrature to a tracking error signal for ensuring reliable track counting in a track seeking operation. In a grooved medium, reflectance is calibrated for both grooves and mesas between the grooves.

Reducing amplitude variations of optical disk readback signals and

An optical disk recorder is capable of operating with diverse types of optical media. A device initialization procedure is repeated for each receipt of each optical medium. Such procedure includes moving an objective lens to an extreme radial position, defocussing the lens at a most remote position, then calibrating the laser circuits to ensure that the emission of radiation from the laser will not inadvertently destroy signals recorded on the just received medium. Then the medium type is read from the medium and based upon the type indication, various additional calibrating procedures are followed and different sources of laser control values are used for signal exchanging operations between the recorder and received optical medium.

Optical disk recorder for diverse media types and having a predetermined

This disclosure deals with an optical disk recorder/player (drive) of the type that receives a removable disk for signal exchanging operations. Once a disk is inserted into the drive, the rotation of the disk begins a period of accelerating rotational speed called spin up. During spin up, the focus and tracking systems of the drive are calibrated. Once the disks reach a desired operating rotational speed, a menu is provided for determining when to calibrate a laser in the drive for recording operations. Such writing or recording calibration of the laser occurs at different times in accordance with the types of signal processing functions to be performed with respect to the particular disk. Description includes a media library in which a plurality of optical disk drives are controlled in a manner for minimizing access times to any optical disk within the media library.

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Tucson, AZ, United States of America

Alan A Fennema