Discovision Associates

Laser Magnetic Storage International Company

David E Lewis

David L Schell

Kurt W Getreuer

Marvin B Davis

Randolph Scott Crupper

Leonardus J Grassens

Johannes J Verboom

Gregory V Hofer

James C McDonald

Kent Thomas Murphy

Pierre R Sonneville

Leonardus I Grassens

Kathleen M Connelly

Cees Van Nimwegen

An optical disc system for storing information on a medium includes a light source, a focusing mechanism, and a tracking mechanism wherein the mechanisms are controlled by a feedback loop and the focusing mechanism focuses light emitted by the light source onto the medium to effect writing of information thereon. The system is provided with an electronic circuit for generating a servo error signal that is communicated in the feedback loop for effecting corrections of the focusing mechanism and the tracking mechanism. The system is further provided with a driver for energizing the light source, a bias coil disposed proximate to the medium, a bias coil driver switchably connected to the bias coil for supplying an electric current thereto, a current monitoring circuit connected to the bias coil driver having an output responsive to the electric current, and a controller connected to the output of the current monitoring circuit and to the driver. The controller thereby enables the driver when the output of the current monitoring circuit exceeds a predetermined magnitude so that information processed through the focusing mechanism is written onto the medium when the electric current flowing in the bias coil exceeds a threshold.

Optical disc system and method for controlling bias coil and light source to process information on a storage medium

An analog to digital circuit assembly includes a circuit for multiplexing a reference voltage input of an analog to digital converter to produce alternating normalized and referenced digital outputs of an analog signal input at a rate controlled by a sampling clock which includes a switch including first and second inputs, an output, and a control input for alternately connecting the first and the second inputs to the output, the output being applied to the reference voltage input. An information detection device having a detection output and a servo mechanism that controls operations on detected information is provided in conjunction with a signal summing circuit, a direct current voltage reference, a control clock connected, a servo error signal circuit having a servo error signal output and input, a sampling clock, and a processing circuit having an input connected to a digital output of the analog to digital converter and an output for controlling the servo mechanism. The analog to digital circuit assembly is also implemented in an optical disc system for improved operation thereof.

Analog to digital converter assembly for normalizing servo error signals and multiplexing reference voltage inputs and digital outputs and improved optical drive system including same

A method for moving an optical head from an initial track to a target track on a storage medium having data arranged in tracks thereon. The method includes determining a track crossing number indicating a number of tracks between the initial track and the target track, moving the optical head from the initial track toward the target track, and measuring a reflectivity level of light from the medium. The method continues with deriving a tracking error signal responsive to the reflectivity level. A waveform of the tracking error signal has zero crossings corresponding to the optical head crossing one of the tracks. The method may further include incrementing a track count number for each the zero crossing, and passing the reflectivity level through a high pass filter to obtain a data indicator signal. In this embodiment, a waveform of the data indicator signal has indicator points corresponding to the zero crossings. The method may conclude by decrementing the track count number for each the zero crossing corresponding to changes in the reflectivity level in response to the data, and terminating the step of moving the optical head when the track count number equals the track crossing number. In an alternative method, the passing step may be replaced with deriving a data indicator signal responsive to the reflectivity level. Apparatus for controlling an optical head according to the present methods include a tracking error signal generator, a preamplifier, a track/hold sector, and a track crossing signal generator.

Method and apparatus for controlling an optical head relative to an initial track and a target track on a storage medium having data arranged thereon in tracks

An optical drive system includes a computer that monitors the current in an improved bias coil assembly in conjunction with a magnetomotive field generator to determine when a predetermined current threshold is exceeded. The bias coil assembly includes a wire coil wrapped around a center bar contained by a bias coil housing. The bias coil assembly is positionable above an information storage medium so that the entire medium may be within the magnetic field thereby allowing writing of information to all portions of the medium. When the threshold is exceeded, a sufficiently strong magnetic field is generated to permit writing of information on the storage medium utilizing a laser. A laser pulse generator is then enabled. The device thereby achieves a substantially shortened write cycle while employing the improved bias coil assembly.

Optical disc system having current monitoring circuit with improved bias coil assembly and controller for laser driver and method for operating same

An optical drive system includes a computer that monitors the current in the bias coil of a magnetomotive field generator to determine when a predetermined current threshold is exceeded. When the threshold is exceeded, a sufficiently strong magnetic field is generated to permit writing of information on a storage medium utilizing a laser. A laser pulse generator is then enabled. The system is provided with an optics module for processing light produced by the laser light source. A laser driver for energizing the laser light source is positioned in close proximity to the optics module and the laser light source to reduce noise in signals associated with the optics module. The system thereby achieves a substantially shortened write cycle while reducing relevant signal noise.

Optical disc system including current monitoring circuit assembly having controller with improved optics module and laser driver and method for operating same

An analog to digital circuit assembly for use in an optical information includes a circuit for multiplexing a reference voltage input of an analog to digital converter to produce alternating normalized and referenced digital outputs of a plurality of analog signal inputs at a rate controlled by a sampling clock which includes a switch including first and second inputs, an output, and a control input for alternately connecting the first and the second inputs to the output, the output being applied to the reference voltage input. An information detection device having multiple detection outputs and having at least one servo mechanism that controls operations on information being detected is provided in conjunction with a signal summing circuit, a direct current voltage reference, a control clock connected, a servo error signal circuit having a servo error signal output and multiple inputs, a sampling clock, and a processing circuit having an input connected to a digital output of the analog to digital converter and an output for controlling at the least one servo mechanism.

Analog to digital converter and assembly for use in optical drive system to normalize servo error signals and multiplex reference voltage inputs and digital outputs

An optical drive system includes an optical assembly, a light source, a lens positioned to direct light between the optical assembly and an information storage medium or disc, and an actuator suspending the lens. A photodetector is disposed in a path of returning light to measure light received from the medium. A monitoring circuit is provided to monitor a Quad Sum signal associated with return light. A first servomotor is employed to move the lens in a tracking direction and to move the lens during focus capture while system circuitry searches for a maximum Quad Sum signal. A second servomotor is employed to move the lens in a focusing direction. A first electronic circuit is provided to control the first and second servomotors. A servo error circuit is coupled to the first electronic circuit and the photodetector to determine when return light exceeds a predetermined value, to search for a first zero crossing, and to indicate to the first electronic circuit to close focus by the second servomotor when the Quad Sum signal exceeds a predetermined amplitude. A focus capture method for use in the system includes impinging light upon the disc, moving the lens, monitoring the Quad Sum signal, moving the lens while looking for a maximum Quad Sum signal, monitoring light received from the disc, determining when the light is above a measured peak value, searching for the first zero crossing, determining when the Quad Sum signal exceeds a predetermined amplitude, and closing focus at the predetermined amplitude.

Optical disc system having servo motor and servo error detection assembly operated relative to monitored quad sum signal and focus capture method for use in same

A magneto-optical drive system having a computer that monitors the current in the bias coil of a magnetomotive field generator to determine when a predetermined current threshold is exceeded. When the threshold is exceeded, a sufficiently strong magnetic field is generated to permit writing of information on a storage medium utilizing a laser. A laser pulse generator is then enabled. The device thereby achieves a substantially shortened write cycle.

Optical disc system having current monitoring circuit with controller for laser driver and method for operating same

A mechanical isolation apparatus suited for mitigating the effects of undesired mechanical forces upon disc drive system components, such as those found in compact disc, laser disc, magneto-optical player/recorder devices and similar devices. Component members are provided for mitigating the effects of compressive forces, vibration isolation, and thermal expansion, and may include compression ribs mounted on a housing for absorbing compressive forces. The housing is preferably adapted to fit on the end of a pole piece assembly. A crash stop may also be provided as a shock absorbing bumper and isolator to prevent a moving carriage from crashing into a solid surface. The compressive ribs and the crash stop are made of a material that exhibits minimum creep, such as a silicon rubber, polyurethane, or injection molded plastic.

Isolation apparatus for use in disc drive system to mitigate effects of

An optical disc drive system is employed in conjunction with a storage medium having a plurality of data sectors each provided with a header and a data storage area. The system includes a data detection device for retrieving stored data from the storage medium and outputting a data signal, an amplifier for providing a variable gain to the data signal and outputting an amplified data signal, a detector that is responsive to the amplified data signal for evaluating a predetermined one of the sectors to ascertain whether the storage area is blank, and an automatic gain control circuit producing a gain control output for controlling the gain of the amplifier. The control circuit has a first mode and a second mode, the first mode being active during retrieval of the header and the second mode being active during retrieval of the data storage area. The system is further provided with a sampling device for sampling the gain control output during retrieval of the stored data in a respective one of the storage areas containing previously stored data. The sampling device outputs results of the sampling, and a fixed gain control circuit is responsive to the results of the sampling for outputting a fixed gain control signal. The fixed gain control signal is applied to the amplifier during evaluation of the predetermined one of the sectors.

Optical disc system having improved circuitry for performing blank

An optical drive system includes an objective lens subassembly for directing light from a light source toward an information storage medium. An amount of the directed lighted light is returned from the storage medium. An objective lens is disposed in the objective lens subassembly. A first servomotor moves, during focus capture, the objective lens to a first position, away from the first position toward the storage medium being read while looking for a maximum Quad Sum signal, and back away from the storage medium. An electronic control circuit is connected to the first servomotor. A servo error detector is coupled to the electronic control circuit and disposed in a path of light returning from the information storage medium. The servo error detector is implemented to determine when total light returned from the information storage medium exceeds a predetermined value, to search for a first zero crossing, corresponding to when the Quad Sum signal exceeds a predetermined amplitude, and to indicate to the electronic control circuit to direct close of focus when the Quad Sum signal exceeds the predetermined amplitude.

Optical drive system having servomotor operated relative to maximum quad

A laser driver for controlling an electrical current supplied to a laser in an optical disc system. The laser driver includes pass transistors for delivering electrical current to the laser, an operational amplifier for setting a reference voltage on the bases of the pass transistors, and a CMOS buffer for applying a drive voltage to emitter circuits of the pass transistors. The drive voltage has a first voltage level and a second voltage level, and the electrical current is supplied to the emitter circuits only when the drive voltage is at the first voltage level. The laser driver further includes a switch for switching the drive voltage between the first voltage level and the second voltage level so that electrical power is consumed only when the laser is energized and enhanced rise and fall switching characteristics are thereby achieved.

Laser driver for controlling electrical current passed to a laser in an

An optical disc system using CMOS logic as part of a power driver assembly is employed to actually switch electrical currents to a system laser so that power is consumed more efficiently, thermal problems are mitigated, and very fast rise and falls times are achieved.

Apparatus for controlling an electrical current passed to a writing

An optical drive system includes an optical assembly, a light source capable of transmitting light through the optical assembly, an objective lens positioned to direct light between the optical assembly and a respective information storage medium, and an actuator suspending the objective lens for relative motion thereof with respect to the actuator. A photodetector is disposed in a path of returning light to measure return light received from the respective medium. A monitoring circuit is provided to monitor a Quad Sum signal associated with the return light. A first servomotor is employed to move the objective lens in a tracking direction relative to the actuator and to move the objective lens during focus capture relative to the respective medium being read while system circuitry searches for a maximum Quad Sum signal. A second servo motor is employed to move the objective lens in a focusing direction relative to the actuator assembly. A first electronic circuit is provided to control the first and second servomotors. A servo error circuit is coupled to the first electronic circuit and the photodetector to determine when the return light exceeds a predetermined value, to search for a first zero crossing determining when the Quad Sum signal exceeds a predetermined amplitude, and to indicate to the first electronic circuit to direct close of focus by the second servomotor when the Quad Sum signal exceeds the predetermined amplitude.

Optical disc system having servo motor and servo error detection

An apparatus for controlling a magnetic field strength of a bias coil at a focal point of a lens during recording on a medium. The apparatus includes a first controller for determining a distance between the focal point of a lens and a reference point on the recording media. A source generates a stray magnetic field having a stray field strength at the focal point. A second controller calculates a digital signal which is a function of the distance and the stray field strength. A digital-to-analog converter converts the digital signal to a driver voltage and passes the driver voltage to a current driver, which drives the bias coil. The magnetic field strength of the bias coil is thereby controlled at a predetermined value. A method is also shown for controlling the strength of a magnetic field, including the steps of determining a distance between the focal point of a lens and a reference point on the recording media, generating a stray magnetic field strength at the focal point, calculating a digital signal which is a function of the distance and stray magnetic field, converting the digital signal to a driver voltage, and applying the driver voltage to a current driver to provide a bias current to the bias coil, thereby controlling the magnetic field strength at a predetermined value.

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Black Forest, CO, United States of America

David E Lewis