International Business Machines Corporation

David E Call

Glen Alan Jaquette

Blair I Finkelstein

Julian Lewkowicz

Lawrence D Tipton

Arturo Avila Mojica

Judson A McDowell

John E Bish

Ernesto Esteban Marinero

Jerry E Hurst, Jr

Anthony Juliana

Stephen J Hrinya

Patrick C Arnett

Catherine S Singer

An optical disk recorder employs laser drive signals having diverse current or power levels. A scaling digital-analog-converter (DAC) supplies a scaled reference signal to a plurality of scaled DACs. The scaled DACs supply the diverse laser drive signals. Calibrating the scaling DAC calibrates the scaled DACs. A base array of DACs include not only the scaling DAC but a plurality of base array DACs. Such base array DACs control reading operations as well as supplying a threshold current. The threshold current is that laser drive signal current level below which laser 25 does not emit a laser beam. During writing, the CUT current is added to the laser drive currents supplied by the scaled DACs. A desired CUT current is determined by calculating a slope of the laser drive current to emission of radiation. Then the slope is extrapolated to a zero emission point below which no coherent emission of radiation occurs.

Laser power-drive circuit having a scaling DAC supplying a scaled

A light intensity, direct overwrite, magneto-optical system generates signals such that, during the formation of a recording mark on an optical disk, a laser is driven a) at a pedestal power level, then b) at a quench power level for a first quench period t.sub.1, the quench power level being less than the pedestal power level, then c) at a write power level for a write period t.sub.2 whereby the reference bit becomes oriented in the writing direction, the write power level being greater than the pedestal power level, then d) at the quench power level for a second quench period t.sub.3, and then e) at the pedestal power level until the formation of another recording mark begins. The system is provided with a controller to determine optimal lengths of the quench periods t.sub.1 and t.sub.3, thereby reducing thermal interference between closely spaced recording marks. From sample recording marks, recorded with different quench periods t.sub.1 and t.sub.3, the controller calculates a 'quality' value, such as bit error rate, jitter or figure of merit, then determines from the quality value the quench periods t.sub.1 and t.sub.3 which will produce the highest quality recording marks.

Magneto-optical recording device capable of reducing thermal

The present invention provides a method and an apparatus to accurately and consistently distinguish blank sectors from written sectors on optical media despite drive and media variations. A readback envelope threshold is established each time optical media is mounted into an optical drive. In one embodiment, the gain of readback amplifiers are set to a first level, the optical head seeks to and reads a sector or set of sectors on the optical disk known to have information recorded thereon and a first readback envelope generated. The gain of the readback preamplifier is then set to a second level, the optical head seeks to and reads another sector or set of sectors known to have information recorded thereon and a second readback envelope generated. The readback threshold is calculated from the amplitudes of the first and second envelopes. Once the threshold has been calculated for a disk, the drive can scan for a blank sector by comparing the amplitude of the sector's readback envelope with the threshold: if the amplitude is less than the threshold, and no other written format feature is readily indicated the sector can be classified as being blank and it is safe to write to the sector.

Calibration of readback threshold in an optical storage device to

A write-once optical disk data recorder automatically calibrates a laser during a write data operation and using write pulses focussed to a disk. First, the laser is calibrated using a non-focussed laser beam. Each sector of the disk has a laser checking or test area, such as an automatic laser power correction field (ALPC) of two byte lineal extent. During a first write operation after a power up or disk load, a pulse width modulated (PWM) laser test signal is recorded using a laser power level set using the non-focussed laser beam and an indicated desired recording power level on the disk. The recorded laser test signal is read back. The length of the read back laser test signal is measured. The measured length is then compared with a desired length of the PWM laser test signal that indicates a desired laser power level. That is, as laser recording power levels increase, a resultant recorded signal grows in size. This property is used to measure laser power for calibrating laser operation.

Monitoring and adjusting laser write power in an optical disk recorder

The present invention provides a method and an apparatus to accurately and consistently distinguish blank sectors from written sectors on optical media despite drive and media variations. A readback envelope threshold is established each time optical media is mounted into an optical drive. In one embodiment, the gain of readback amplifiers are set to a first level, the optical head seeks to and reads a sector or set of sectors on the optical disk known to have information recorded thereon and a first readback envelope generated. The gain off the readback preamplifier is then set to a second level, the optical head seeks to and reads another sector or set of sectors known to have information recorded thereon and a second readback envelope generated. The readback threshold is calculated from the amplitudes of the first and second envelopes. Once the threshold has been calculated for a disk, the drive can scan for a blank sector by comparing the amplitude of the sector's readback envelope with the threshold: if the amplitude is less than the threshold and no other written format feature is readily indicated, the sector can be classified as being blank and it is safe to write to the sector.

Calibration of readback threshold in an optical storage device

A laser control system for use with an erasable optical disk device to minimize laser feedback during a recording operation. Focus control circuits are utilized to establish a slightly defocused condition prior to a recording operation and maintaining that slightly defocused condition throughout the recording operation. Defocusing the write beam significantly reduces feedback and thereby significantly increases pulse-to-pulse repeatability of the write pulse amplitude at the optical disk.

Laser power control with defocusing offset during data recording

A drive circuit for a laser which has the capability of eliminating transient conditions when switching a high frequency modulator on or off, and including elements for maintaining desired depth of modulation. These capabilities are included in a circuit that automatically compensates for changing conditions due to temperature, laser characteristics and fluctuations in media reflectivity.

Compensated laser drive circuit

Calibration of the write signal power level applied to a transducer for marking a moving media to optimize a later recovered read-back signal is provided. An optimized read-back signal is one where the peak-to-peak amplitude of the read-back signal is maximized. The method provides marking test patterns on the recording media at a plurality of discrete, selected write signal power levels of the marking source, developing a read-back signal from the test pattern marks, correlating portions of the read-back signal with the write signal power levels and solving a relationship of the form

Write power calibration utilizing least squares fit of read-back signals

Apparatus and method for calibrating the drive current circuit of a semiconductor laser diode subject to reflected optical feedback from a target surface such an an optical recording disk. The method makes use of two power output vs. drive current characteristic curves for the laser, one curve for in focus condition and one for out of focus condition, wherein the curves exhibit an asymptotic region at high power levels (P.sub.2). Measurement of drive current (I.sub.2) power level P.sub.2 is taken under an out of focus condition. Measurements of drive current at a predetermined low power level P.sub.1 are taken for both (I.sub.1) and in focus condition (I.sub.3). The linear slope of the in focus curve can thus be calculated to set desired power levels.

Laser power calibration by measuring laser drive current at out of focus

An optical disk recorder has a laser driven by a digital analog converter (DAC). During initialization a pair of comparators actuated at minimum and at maximum power levels for actuating a microprocessor to calibrate a DAC 23 between the minimum and maximum power levels rended of digital input changed to the DAC. The same comparators can be used during normal recording and reading operations for detecting under and over power conditions of the laser. Procedures for the calibration and over power and under power detection are described.

Calibrating and power-protecting laser drive circuits

Method and apparatus for predicting the approach of semiconductor laser diode end-of-life from the power vs. current characteristic curve of the diode thereby obviating the need for nonvolatile memory. Current measurements are taken for three power levels and the linear slope of the characteristic curve at the high power level is compared to the linear slope at low power levels. When the comparison exceeds predetermined criteria, a flag is raised.

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Tucson, AZ, United States of America

David E Call