Abstract: A disk drive is disclosed comprising an actuator arm, a head attached to a distal end of the actuator arm, a voice coil motor for rotating the actuator arm about a pivot, and an optical sensor operable to generate a first position signal representing a position of the actuator arm with respect to the disk, wherein the first position signal is substantially unaffected by a vibration mode of the actuator arm. Servo sectors recorded on the disk are processed to generate a second position signal representing a position of the head with respect to the disk, wherein the second position signal comprises a significant component due to the vibration mode of the actuator arm. A control signal is applied to the voice coil motor in response to the first and second position signals.

Abstract: In method of feedback control for active damping of slider air bearing vibrations in a hard disk drive slider, a slider is isolated from ground. A velocity signal is acquired from the slider. The velocity signal is filtered to acquire a vibration signal. The vibration signal is adjusted in amplitude to achieve an amplitude adjusted vibration signal. The amplitude adjusted vibration signal is applied to the slider to actively dampen vibrations in the slider.

Abstract: An air pressure sensor capable of measuring air pressure highly accurately with a simple configuration is provided. The sensor includes: a sealed case with a sealed space formed therein; a first thin plate member which constitutes at least a part of the wall of the sealed case and deforms to allow the capacity of the sealed space to vary corresponding to changes in the outside air pressure; a first PZT which contacts the first thin plate member to thereby detect the natural frequency thereof; and a second thin plate member which has the same vibration characteristics as those of the first thin plate member and is provided outside the sealed case while contacting it; and a second PZT which has the same temperature characteristics as those of the first PZT and contacts the second thin plate member to thereby detect the natural frequency thereof.

Abstract: A method and system for determining contact potential voltages between a slider body and a hard disk of a hard disk drive. In embodiments of the present invention, at least one continuous negative direct current (DC) voltage is applied between a slider body and a hard disk of a hard disk drive. Then, at least one continuous positive direct current (DC) voltage is applied between the slider body and the hard disk. A contact potential voltage between the slider body and the hard disk is then determined in response to the applying of the direct current voltages.

Abstract: An information recording apparatus comprises a recording medium, a swing arm driven by an actuation unit, the swing arm swinging over a surface of the recording medium in response to driving by the actuation unit, a recording head carried by the swing arm and scanning over the surface of said recording medium with a swinging motion of the swing arm by the actuation unit, the recording head recording information to the recording medium, a head retracting mechanism retracting the recording head out of the recording medium in an unload state where no recording is to be made on the recording medium, an optical injection unit injecting a light into the recording head, the recording head including an optical irradiation part irradiating the light injected to the recording head upon the recording medium when recording information to the recording medium, wherein the optical injection unit is integrated with the head retracting mechanism to form a unitary optical-injection and head-retraction mechanism.

Abstract: In a method of feedback control for active damping of slider air bearing vibrations in a hard disk drive slider, a slider is isolated from ground. A slider velocity signal is filtered to acquire a vibration signal. The vibration signal is adjusted in amplitude to achieve an amplitude adjusted vibration signal. The amplitude adjusted vibration signal is applied to the slider to actively dampen air bearing vibrations in the slider.

Abstract: Track mis-registration (TMR) correction is conditionally made in a hard disk drive using servo data in a closed loop servo control scheme, along with one or more alternative sensing schemes when an external shock or vibration occurs. The alternative sensing schemes include measurement of spindle motor speed using a frequency of servo markers read from a rotating disk, voice control motor (VCM) back emf, spindle motor speed back emf, and accelerometer readings. The predicted TMR resulting from the signal generated by the alternative sensing scheme(s) is simulated based upon a model of the disk drive system, and corrections are applied only if the expected TMR due to the disturbances is large enough that application of the corrections using the alternative sensing scheme would be likely to reduce the overall TMR.

Abstract: The method and a device to measure the repeatable and non-repeatable runouts of a rotating component of a spindle motor with the aid of at least one probe measuring changes in the distance between the probe and the rotating component depending on the angle of rotation. The probe records a first test signal in a first test cycle from which a signal defining the RRO is determined and stored. In a second test cycle, a command signal proportional to the amplitude and phase of the RRO signal is generated and fed to an electromechanical actuator supporting the probe. Depending on the command signal derived from the first test signal, the actuator changes the distance between the probe and the outer perimeter of the rotating component, thus compensating the runout defined by the RRO signal, while the probe records a second test signal defining the NRRO.

Abstract: Magnetic alignment marks are recorded on a recording surface of a magnetic hard disk to mark the location where the disk is abutted against the hub of the spindle of a multiple-disk servo-writer. The alignment marks for each recording surface may be different so as to distinguish between top and bottom disk surfaces so that when the discs are assembled onto the spindle of a disk drive they may be assembled with the proper orientation, i.e., the top surface is mounted “up.” The marks may be large, low frequency patterns that are both written and detected by non contact means other than the servo-track writer's or the disk drive's heads.

Abstract: A disk drive is disclosed comprising a disk, an actuator arm, a head coupled to the actuator arm, a base, and an optical sensor operable to detect a position of the actuator arm. The optical sensor comprises a light source that is stationary relative to the base, a plurality of light sensitive sensors positioned to receive light from the light source, and a substantially opaque element positioned between the light source and the light sensitive sensors configured to control an amount of light at least one of the plurality of light sensitive sensors detects relative to the position of the actuator arm.

Abstract: In a feedback control mechanism for active damping of slider air bearing vibrations in a hard disk drive slider, an assembly is used to acquire a velocity signal from the slider. A filter, electrically coupled with the assembly, is used to filter a velocity signal to achieve a vibration signal. A phase-shifter, electrically coupled with the filter, shifts the phase of the vibration signal to achieve a phase-shifted vibration signal. An amplifier, electrically coupled with the phase-shifter, adjusts the amplitude of the phase-shifted vibration signal to achieve an amplitude adjusted vibration signal. An electrical coupler couples the amplitude adjusted vibration signal with the slider for actively damping air bearing vibrations in the slider.

Abstract: A disk drive includes a disk for storing information, a head with a transducer that writes data to and reads data from the disk, and an AC power source. The head is suspended adjacent to the disk and a flying height gap exists at the head/disk interface. The AC power source generates an AC exciter signal across the flying height gap that discharges electrostatic charge at the head/disk interface. The head/disk capacitance can be measured based on the AC exciter signal to sense the flying height. The AC exciter signal can also alter an attraction force between the head and the disk and thus control flying height. The AC exciter signal can also be based on a flying height signal representative of the head/disk capacitance and thus the flying height.

Abstract: In a feedback control mechanism for active damping of slider air bearing vibrations in a hard disk drive slider, a filter is used to filter a velocity signal from a slider to acquire a vibration signal. A phase-shifter, electrically coupled with the filter, shifts the phase of the vibration signal. An amplifier, electrically coupled with the phase-shifter, adjusts the amplitude of the phase-shifted vibration signal to achieve an amplitude adjusted vibration signal. An electrical coupler couples the amplitude adjusted vibration signal to the slider for actively damping air bearing vibrations in the slider.

Abstract: A data storage medium such as a disc for a disc drive having a data signal layer configured for providing a data signal and a servo signal layer that includes first material a second materials having thermal characteristics that are distinct from one another. The first material and second material define at least one signal feature for providing a modulating servo signal based upon the variation of thermal properties in the servo signal layer. The first material may define spaced features of a servo pattern such as grooves and pits and the second material may fill the grooves and pits or other features. The intersection of the first and second material may provide a distinct thermal transition so that when the medium, typically a disc, is rotated around an axis, the servo features generate a thermo signal having a frequency proportional to the spacing between the signal features and an amplitude that is a function of the thermal properties of the first material and the second material.

Abstract: In one example, a method is provided for detecting the relative position of a transducer head with respect to a storage medium utilizing existing or previously written data structures on a magnetic storage tape and optically diffractive media. The method includes generating a read signal from a read element associated with a transducer head, the read signal generated from a reference data track stored on a magnetic storage medium, and determining a relative position of a first diffractive medium with respect to a second diffractive medium, wherein the first diffractive medium is associated with the storage medium. The transducer head is repositioned relative to the storage medium in response to the read signal and the relative position of the first diffractive medium and the second diffractive medium.

Abstract: The present invention provides servo systems and accompanying methods for determining the relative position of a transducer head to a magnetic storage tape utilizing existing data structures on the magnetic storage tape and the position of the tape edge. In one example, a method for positioning a transducer head relative to a magnetic storage medium includes sensing a read signal from a read element associated with a transducer head, the read signal in response to a reference data track stored on a magnetic storage medium, optically sensing a position of an edge of the storage medium, and repositioning the transducer head relative to the storage medium in response to the read signal and the position of the edge of the storage medium.

Abstract: Track mis-registration (TMR) correction is conditionally made in a hard disk drive using servo data in a closed loop servo control scheme, along with one or more alternative sensing schemes when an external shock or vibration occurs. The alternative sensing schemes include measurement of spindle motor speed using a frequency of servo markers read from a rotating disk, voice control motor (VCM) back emf, spindle motor speed back emf, and accelerometer readings. The predicted TMR resulting from the signal generated by the alternative sensing scheme(s) is simulated based upon a model of the disk drive system, and corrections are applied only if the expected TMR due to the disturbances is large enough that application of the corrections using the alternative sensing scheme would be likely to reduce the overall TMR.

Abstract: A compact optical tracking system for magnetic tape is disclosed which is independent of the magnetic format and head structure which can generate a position error signal without encoding on the servo track. A plurality of optical servo modules is arranged in a linear array. Each optical servo module contains an optical beam source, preferably a laser, an optical beam interference composite hologram for producing a predetermined pattern on a target and at least one detector for detecting an optical beam reflection. A position correction signal is generated by one or all of the optical servo modules for re-positioning a magnetic head, which reduces the error in the correction signal from tape degradation and dimensional changes. Reference grating may be added to provide further position calibration prior to the tape being positioned over the head.

Abstract: A disk includes an actuator assembly, a spindle motor and a disk that defines a plurality of servo wedges. A wedge to wedge timer is configured to measure the time elapsed between at least two circumferentially adjacent servo wedges and to output a wedge to wedge correction signal that defines a count between circumferentially adjacent servo wedges that is dependent upon the measured elapsed time. A servo frequency generator is configured to output a servo frequency generator signal having a frequency that is modulated by the wedge to wedge correction signal. A spindle motor control timer outputs a spindle control timer signal that is dependent upon the servo frequency generator signal and upon the time elapsed between at least two successive detections of circumferentially adjacent servo wedges. A spindle motor controller controls the spindle motor with a control signal that changes according to the spindle control timer signal.

Abstract: A recording target error rate is selected for one or more of data storage devices, and for each data storage device, a dither value is determined for each read/write head in the data storage device, wherein for each head, using a dither value for writing data, essentially provides the selected recording target error for all the heads.

Abstract: To detect the position of an object in a non-contact state at high reliability, high accuracy, and high resolving power, a linearly polarized light beam from a semiconductor laser source is converted into an almost parallel light beam by a collimator lens, transmitted through a non-polarization beam splitter, focused by an objective lens, and transmitted through a crystal plate. When an appropriate thickness t is given to the crystal plate, the principal rays of polarized light beams o and e emerge while being shifted by a predetermined amount and are focused into a spot or line having a width w near a slit-shaped marking (M) formed on a head arm, whereby portions shifted from each other are illuminated. The two reflected light beams pass back through the crystal plate. The principal rays of the two light beams match again and are returned to the non-polarization beam splitter, and split into transmitted light and reflected light.

Abstract: A servo writer system for a disk drive uses the reader element of a magnetic transducer head in the disk drive to read head position information during servo writing of the disk drive. A positioning system in the servo writer uses both the head position information and actuator position information, as feedback signals to accurately position the transducer during servo writing, resulting in high quality servo tracks.

Abstract: A disk-shaped magnetic recording medium having a reference track and a plurality of data tracks is rotated by a motor which generates an index signal at a predetermined position. A magnetic head is slightly moved in the radial direction of the medium for each predetermined unit distance smaller than the data track width, and a reproduction output amplitude measuring circuit measures the reproduction output amplitude of a signal read from the data track for each index signal. A CPU obtains a position where the amplitude has the maximum value based on the number of head movements and the amplitude at that time so as to control data track positioning. Further, the CPU calculates a relative position between the data track position and the reference track position to perform reference track positioning. The data or reference track positioning of the magnetic head can be performed accurately in a short time.

Abstract: A hard disk device includes a servo control unit that constitutes a servo loop for a head seek for performing read/write of data from/to a recording medium, a correction signal generation unit for generating a correction signal for correcting a control by the servo control unit based on an output of a predetermined sensor, and a correction signal control unit for estimating an effect of supplying the correction signal to the servo loop and for controlling whether or not the correction signal is to be supplied to the servo loop in response to a result of the estimation. Moreover, the gain of the sensor is dynamically controlled in response to the above estimation result.

Abstract: A data recording disk drive has a plurality of capacitive sensors, each sensor facing a surface of an associated disk, a capacitance sensing circuit for converting the sensed capacitance to a voltage representative of the distance between the sensor and the disk surface, and a feedforward controller that receives the voltage signal. The feedforward controller has a transfer function with gain and phase characteristics designed to match the transfer function from the out-of-plane disk vibration to the position of the read/write head while accounting for the effects of the sensor dynamics and the dynamics of the actuator. The output from the feedforward controller is combined with the output from the disk drive's servo feedback controller so that the effects of disk vibration on track misregistration of the head are removed from the control signal to the actuator.

Abstract: A position information signal pattern is recorded into a recording medium. The position information signal pattern is configured by arranging graphics having a circular shape, a rectangular shape or the like surrounded by a certain closed curve as pattern elements on a plane, and arranging the pattern elements in circumferential and radial directions of a disc so that a phase and a head position establish a proportional relationship in two or more frequency components of a reproduced signal. Position signals of the two frequency components included in the reproduced signal from the position information signal pattern are obtained, and the two position signals are added up with a certain ratio so that a position signal without error is obtained.

Abstract: A system and methods for efficiently performing media writing functions is disclosed. The system and methods include: detecting media movement with respect to a base and heads during reading and writing, and moving the heads in response; using an interferometer, such as a dual beam differential interferometer, to dynamically monitor disk position and address perceived errors; and minimizing repeatable and non repeatable runout error by writing data, such as servo bursts, in multiple revolutions to average adverse runout conditions. The present system has the ability to use an interferometer to enhance media certification and perform on line, in situ monitoring of the media, and includes shrouding, head mounting, disk biasing, and related mechanical aspects beneficial to media writing.

Abstract: In an information recording method of the present invention by carrying out recording data while carrying out tracking servo accurately, high density recording of signals at a good S/N can be carried out, and high density recording by a vertical magnetic recording system can be carried out. A magnetic disk comprises a magnetic recording layer, and the magnetic recording layer is magnetized in advance such that magnetized regions A and B having different magnetization directions are formed. At a time of recording data, vertical magnetic recording is carried out by a magnetic head while carrying out accurate tracking servo by optically tracking by a magneto-optical effect utilizing a difference in the magnetization directions of the magnetized regions A and B. Therefore, high-density recording at a good S/N is possible.

Abstract: A disk drive (HDD) subject to linear and rotational vibration, includes an independent sensing unit for sensing a rotational velocity component of the HDD rotational vibration in a predetermined frequency range.

Abstract: A method and a system for formatting a magnetic tape with identifiable optical servo tracks are disclosed. Multiple optically detectable servo tracks extending lengthwise parallel to the tape transport direction are written simultaneously by directing a spatial beam dot pattern unto the magnetic tape. The beam dot pattern is capable of imparting not only a unique identification, but also other information such as tape longitudinal address, and manufacturer's data to each servo track. The spatial beam dot pattern may also include two arrays of beam dots created via the use of two one-dimensional diffractive optical elements.

Abstract: Magnetic alignment marks are recorded on a recording surface of a magnetic hard disk to mark the location where the disk is abutted against the hub of the spindle of a multiple-disk servo-writer. The alignment marks for each recording surface may be different so as to distinguish between top and bottom disk surfaces so that when the discs are assembled onto the spindle of a disk drive they may be assembled with the proper orientation, i.e., the top surface is mounted “up.” The marks may be large, low frequency patterns that are both written and detected by non contact means other than the servo-track writer's or the disk drive's heads.

Abstract: A method of generating a composite signal in a closed loop servo signal system of a data recording system used to drive a recording head to any given position within a dynamic range of a servo tracks includes an optical pickup system for generating optical spots focused on a recording medium, the spots separated by equal distances across a track, the optical pickup system receiving a set of reflectances from the spots, a media system for providing the servo tracks responsive to optical spot illumination, an electric system for generating a set of filtered signals from the reflectances and for generating a set of S-curves by pair wise subtraction of the filtered signals, a processing system to generate a composite servo position signal from the S-curves and filtered reflectances, and a servo system for driving the recording head to a desired position by comparing the desired position to a measured position from the composite servo position.

Abstract: A method of positioning a selected recording channel on a recording head relative to an optical servo system includes positioning the optical servo system at a first position relative to the selected recording, processing an alignment tape to determine a lateral offset between the optical servo system and the selected recording channel and positioning the optical servo system at a second position relative to the selected recording channel using the lateral offset. An alignment tape is also provided, which includes an elongated continuous web of flexible plastic substrate material having two edges and defining a front major surface and a back major surface, a magnetic storage medium formed on the front major surface, an inert medium formed on the back major surface and a track of alignment voids for indicating actual lateral displacement of the selected recording channel relative to the optical servo system.

Abstract: A method of reducing rotational vibration effects in a disk drive by sensing vibration in a sensor and generating corresponding sensor data; deriving a statistical sensor (SS) value based on the sensor data; deriving a statistical position error signal (SPES) value from servo sectors read by the head; comparing the SS value to a SS-threshold value; comparing SPES value to a SPES-threshold value; and generating a feed-forward command effort signal for reducing rotational vibration effects if the SS value exceeds the SS-threshold value and if SPES value exceeds the SPES-threshold value.

Abstract: An information recording system includes a storage medium, such as a magnetic or an optical medium, that is formed to have a plurality of adjacent tracks. Each track includes a plurality of storage elements that are arranged substantially along the track in a regular manner. A head disposed in proximity to the storage medium and has a width that spans at least two adjacent tracks. The storage elements are further arranged substantially along first and second axes, such that the first and second axes are substantially perpendicular to each other and are each substantially oriented 45° from an along-track direction associated with a track. The head reads and/or writes information from at least two adjacent tracks spanned by the head.

Abstract: A magnetic disk tester has a head clamp (35, 218) to position a magnetic head (15, 289). The head clamp has a micromotion stage (55, 273) provided with a stage (59, 205) which is horizontally moved by a piezo-element (77). The magnetic head is attached to the piezo-stage (55, 273). On the head clamp (218), a reflective scale (222) is attached to a back face of the piezo-stage, and a laser head (217) is oriented toward the head clamp (218). According to a reflected laser beam from the reflective scale, the position of the magnetic head (289) is detected. An error signal indicating the difference between the detected position and a reference position is used to control the head clamp (218). The piezo-element can operate at high frequencies, to easily make the magnetic head trace a target track and improve the positioning accuracy of the magnetic head.

Abstract: Described herein is a read/write transducer for a hard disk drivewith dual actuation stage, comprising at least one hard disk and at least one suspension carrying the read/write transducer. The read/write transducer comprises a supporting body having a substantially parallelepipedal shape, a read/write head arranged on a front face of the supporting body, and a grating defined on one of the side faces of the supporting body during the process of manufacture of the read/write transducer. The grating enables measurement of the position of the read/write transducer with respect to the corresponding suspension in an optical way using a laser transmitter emitting and directing towards the grating a laser beam, and a laser receiver arranged to intercept the laser beam reflected by the grating and outputting a position signal on the basis of which it is possible to calculate, in a simple way, the position of the read/write transducer with respect to the corresponding suspension.

Abstract: A hard disk drive that has a reaction mass and a transducer that can be used to move and/or sense the acceleration of an actuator arm of the drive. The transducer is coupled to a disk controller that can provide output signals which induce a movement of the reaction mass. Movement of the reaction mass will cause a responsive movement of a head(s) coupled to the actuator arm. The transducer can also provide input signals to the controller that correspond to an acceleration of the actuator arm. The acceleration signal can provide force feedback for a servo system of the drive.

Abstract: A magnetic recording apparatus which, even when crosstalk occurs between signals from three photosensitive parts of a photodetector, can detect a high-precision tracking error signal with stability. In a signal processing unit which processes electrical signals outputted from a photosensitive part of a photodetector to detect a tracking error signal, an output signal from and I-V converting unit is subjected to voltage division by voltage-dividing units, and voltage-divided output signals and output signals from I-V converting units are subjected to differential calculation by differential arithmetic units, respectively.

Abstract: Method and apparatus for operating a motor. During a commutation state current is applied to a motor while field effect transistors (FETs) are held in an enable or disable state to effect current in phases of the motor. The phases have a high FET and a low FET. Control circuitry is employed to detect back electromotive force and zero crossing (Zc) signals that indicate transition timing for the commutation states. At a transition state the current is decreased in accordance with a noninstaneous decay function and applying a pulse width modulated signal to a switching element. Alternatively, the current is decreased by enabling either all low side FETs or all high side FETs to allow the current to decay. The next commutation state is applied after the current has been reduced, avoiding negative current to be source from ground and reducing current spikes in the motor.

Abstract: A disk drive (HDD) (and method) subject to linear and rotational vibration, includes an independent sensing unit for sensing a rotational velocity component of the rotational vibration in a predetermined frequency range, and an optimal filter combination for receiving an output from the sensing unit.

Abstract: The present invention relates to controlling an actuator for positioning a read/write head in storage devices such as disk drives. More specifically, the invention relates to using a sensor to detect the disk vibration amplitude perpendicular to the disk surface, and using feed forward control to cancel or counteract the tendency of the read/write head to deviate off-track due to disk vibration. Various approaches are proposed to detect the disk vertical vibration.

Abstract: A scanning device for scanning data-carrying disks. The disks include a magnetisable layer to and from which data is written and read using a magnetic transducer, such as a Giant Magneto-Resistive (GMR) transducer. Positioning of the transducer over a data track is achieved by optical tracking using a land/groove structure, and positioning of the transducer with respect to the optical tracking system by means of a reference beam transmitted through the disk.

Abstract: An apparatus for optically detecting rotational position information of a rotating object, includes a light source, a detector which is located at a position to receive scattered light from the rotating object when the rotating object is irradiated with a light beam from the light source, and outputs a frequency signal based on the scattered light, a signal processing system for detecting rotational position information by performing signal processing for the frequency signal from the detector, and a rotation control system for controlling rotation of the rotating object. The rotation control system preliminarily rotates the rotating object in detecting the rotational position information.

Abstract: An apparatus and method of indirectly measuring half frequency whirl in a spindle motor having a rotor adapted to rotate a disc having a track which is followed by a transducer head that is actuated by a control system is provided. Vibration signals produced at the transducer head while the transducer head follows the track are detected. The half frequency whirl is determined as a function of the detected vibration signals.

Abstract: This invention discloses a method for controlling the position of flexible portions of a mechanical structure by attaching one or more Momentum Transfer Actuators on the flexible portions of the mechanical structure near the points whose position is to be controlled, sensing the position of the flexible portions of the mechanical structure, and, employing one or more feedback loops, to control the Momentum Transfer Actuators to cause the flexible ends of the mechanical structure to follow a desired position as a function of time. The invention also addresses the use of combined actuating and sensing devices that incorporate both a Momentum Transfer Actuator and an inertial sensor to provide acceleration, velocity, and position information to the feedback control system.

Abstract: An information recording and reproducing device includes a magnetic information detecting section for magnetically detecting magnetic information recorded at a given position on a recording medium, an optical information detecting section for optically detecting optical information recorded at a given position on each track of the recording medium, and a positional control section for controlling a position on the track using the detected magnetic information and optical information.

Abstract: The controller circuit is designed to generate the positioning control signal based on the positional deviation of the head from a target recording track on a recording medium. A feedback control is effected to position the head right on a trajectory corresponding to the target recording track based on the generated positioning control signal. The positioning control signal is subjected to filtering at a notch filter. The cutoff frequency of the notch filter is set depending on the temperature detected at a thermal sensor. Even when the resonant frequency shifts in response to variation in temperature, the cutoff frequency of the notch filter follows the shift of the resonant frequency. A narrower bandwidth of the cutoff frequency still achieves reduction in the amplitude of the frequency component corresponding to the resonant frequency. The resonance or continuous vibration can reliably be prevented in the head.

Abstract: The diffraction-based monitoring techniques described herein can be used, for example, as quality assurance measure in manufacture of magnetic recording media with servo tracking. In one embodiment, the invention presents a system comprising a light source such as a laser that directs light upon a surface of a magnetic recording medium. The magnetic recording medium has two or more physical marks, and the light striking the magnetic recording medium produces a diffraction pattern. A light detector such as a photodiode detects some or all of the diffraction pattern. The physical marks may be servo tracks on the magnetic recording medium, and the detected diffraction pattern is a function of the characteristics of the servo tracks.

Abstract: Marks with curved edges are used in data patterns and sensed with proximity recording. Circular, elliptical, and oval marks are examples of marks with curved edges that can be used in the present invention. The marks with curved edges are used to define data patterns (e.g. position error signal patterns) as a function of radius. If the marks with curved edges have been recorded longitudinally, an amplitude of a read back signal, such as a peak amplitude, is determined in order to generate a position error signal. If the marks with curved edges have been recorded vertically, an area under the curve of the read back signal is determined in order to generate a position error signal.