International Business Machines Corporation

Blair I Finkelstein

David E Call

Timothy Carl Strand

Morovat B Tayefeh

Terry W McDaniel

Glen Alan Jaquette

Kurt A Rubin

Andrew A Gaudet

Daniel James Winarski

Raymond Yardy

Hal Jervis Rosen

Ernesto Esteban Marinero

Alan A Fennema

Patrick C Arnett

Hideo Ueno

James J Dente

Marc Ethan Goldfeder

William C Williams

Michael T Solan

Michael R Madison

Hal A Rosen

Catherine S Singer

By adjusting the advancement rate of an optical data storage medium in response to the amount of data to be written, and operating a laser with a minimum amount of write laser power level for the particular advancement rate to achieve a desired level of write effectiveness, data signals are written to the optical medium with a minimum amount of power. Where the optical medium comprises an optical disk, choosing the rate of disk rotation selectively establishes the advancement rate. Similarly, where the optical medium comprises an optical tape, choosing the rate of tape advancement from source reel to take-up reel selectively establishes the advancement rate. Preferably, the advancement rate is increased or decreased depending upon whether a greater or lesser quantity or write length of data resides in a write queue. The invention may be implemented, for example, to provide a process, apparatus or program storage medium useful for laser storage of digital data signals to an optical data storage medium with minimal power consumption.

Optical storage drive employing variable write speed for reduced laser

An optical disk player reads either thin-substrate disks or thick-substrate disks. The disk players optical system is designed for reading the thin-substrate optical disks and has an effective numerical aperture. Thick-substrate optical disks having a thicker substrate than the thin-substrate optical disk result in the laser beam reading such thick-substrate optical disks having spherical aberration sufficient to prevent reliable data detection. When thick-substrate optical disks are being read, the read portion of the optical system is automatically changed to accommodate the undesired spherical aberration. The thick-substrate disk reflected laser beam is subjected to annular filtering that reduces spherical aberration sufficiently for enabling data and servo signal detection. Annular filtering is provided in an optical read path by an effective opaque or translucent disk centrally located in a pupil of the laser beam optical filter disposed in the read portion. An apertured plate having an aperture comparable to a known diffraction limited spot size is disposed between the laser beam filter and photo detectors. The apertured plate is disposed in the focal region of a lens in the optical read path.

Reading optical disks having substrates with diverse axial thicknesses

This invention provides an optical disk device with a switchable filter for reducing the light intensity from a write level to a read level or an erase level. The filter can further be used to modulate the light intensity between a write level and a gap level for the process of recording data. For semiconductor laser sources, this filter reduces laser feedback noise by allowing the laser to operate at a higher, more stable power level during data sensing, and by reducing the amount of light reflected from the storage disk back to the laser cavity. Because the filter transmission can be high during the write process, the power requirements of the semiconductor laser are not increased in the device of this invention. In one embodiment, the switchable filter of this invention includes a variable retarder with means to select light on the basis of its phase or polarization, for example, with polarizers. This retarder can comprise a liquid crystal cell wherein either the optical orientation or retardance is electro-optically tunable.

Switchable filter for modulating laser intensity and reducing laser

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

A laser read beam power level is increased with increasing radii and decreased with decreasing radii of scanning a spiral track in an optical disk. The change of read beam power level is adjusted in accordance with an established erasure profile. The erasure profile indicates beam power level at various radii at which recorded data are erased, such as in a magneto-optical disk. Read beam power level is adjusted from a pre-established minimum read beam power level (used at an inner disk radius) following the erasure profile. This action maximizes read power level without exceeding the erasure profile indicated power levels. Radial ranges are established for reading from the optical disk. Within each range, the laser beam read power level is kept constant, preferably at the desired power level at an radially inner-most portion of the respective range. Optical disks have the minimum laser read beam power level and an erasure profile recorded therein.

Optimized laser read power based upon scan speed of optical medium and

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

A magnetooptical disk has two axially space-apart translucent recording layers. Each translucent recording layer is axially closer to an outer surface of the disk than to the other recording layer. This geometry enables closely axially disposing a magnetic field biasing means to each of the recording layers from opposite axial sides of the disk, respectively. Laser beams are axially introduced into the disk to pass through one of the translucent recording layers in a defocussed state to reach a second recording layer in a focussed state. In this manner, recording in the second layer is effected by a modulated magnetic bias field using a constant intensity laser beam. Two sets of laser beams and magnetic biasing means are provided for recording on both data in both of the recording layers.

Optical disk recorders using disks coatings close to outer surfaces with

Two-sided optical disks having recording layers disposed close to outer

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

An optical disk drive apparatus includes a magnet-optic optical disk, laser generator, optical system, first and second photodetectors, data detecting and amplifying device connected to the photodetectors and a laser generator control device. The photodetectors each have first and second detecting sections receiving leading and trailing light beam segments, respectively, and each photodetector producing a magnitude proportional output signal. The control device includes a mode setting device for operating in a read only mode using both first and second sections and a read while performing a write mode using only the second sections.

Split detector system for direct read-while-write operation on

A magnetooptic recorder uses a magnetooptic disk for any predetermined number of radially inward tracks which are designated as calibration tracks. One of the calibration tracks is selected as a laser calibration track. The selected track is high powered erased and a test pattern is written on the track. A test pattern is repeated at diverse levels of laser recording power. A test pattern preferably includes or is limited to the highest frequency to be recorded in the ensuing data recordings. The recorded test pattern is read back with the readback signal amplitude being envelope indicated and detected. A table of signal envelope values is created in a digital computer. The values then are fit to a curve using second order polynomial curve fitting techniques. The maximal readback signal amplitude is then selected from the curve corresponding to laser write power used to obtain that maximum signal amplitude and is then selected as a criteria for indicating the laser write power as well as the erase write power.

Calibrating lasers for optical recording using a maximal readback signal

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.

System for predicting laser end-of life from the power vs. current curve

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

A laser in a magneto optical recorder supplies a laser light beam to be used in processing signals to and from a magneto optical record member. The laser beam is split into two portions. A first portion is the data beam which is directed to impinge upon a magnetooptic storage member. A second portion is so-called wasted light which is directed away from the storage member. The wasted light is intercepted by a mirror and reflected into a beam splitter to phase-coherently combine with light reflected from the storage member for improving signal-to-noise ratio of the reflected storage member light beam. This action improves signal-to-noise ratio and enhances servo operation in the focusing position control of the optical head with respect to an optical storage medium. The focus control signal derived from the reflected light is not only used to control the focus of an objective lens in the system but also for positioning the mirror in synchronism with the movement of the storage member along the axis of the objective lens so that the phase-coherence of the wasted light beam and the data beam is maintained.

Growing community of inventors

Tucson, AZ, United States of America

Blair I Finkelstein