Abstract: A magnetic transfer method includes a first step (ST103) of preparing a magnetic disk, a second step (ST105) of forming a layer of lubricant on the magnetic disk, a third step (ST108) of bringing a surface of the magnetic layer on the magnetic disk into close contact with a magnetic transfer master having a magnetic film formed on at least one side and magnetically transferring a pattern of the magnetic film on the magnetic transfer master onto the surface of the magnetic disk through application of an external magnetic field, and a fourth step (ST104, ST106) of burnishing at least a surface of the magnetic disk that comes into contact with the magnetic transfer master. The first step, the fourth step, the second step, the fourth step, and the third step are performed in the stated order.

Abstract: A magnetic transfer device for bringing a master carrier with information and a slave medium into intimate contact with each other and then applying a transfer field to transfer the information to the slave medium. The master carrier has an inclined face on its radially outer end. After the magnetic transfer of the information, claws are inserted in the gas formed by the inclined face of the master carrier and the slave medium. The slave medium held in intimate contact with the master carrier is separated from the master carrier by lifting the slave medium with the claws.

Abstract: Defects of a hard disk drive servo pattern stamper are detected by comparing a scattered light beam pattern against the known servo pattern. A magnetic field is applied to stamper and the beam is linearly polarized. Variations in the physical offset of the beam, its scatter, are indicative of physical defects. Variations in the Kerr rotation of scattered beam are indicative of magnetic defects.

Abstract: A method and an apparatus encodes and decodes blocks having a predetermined number of sectors of data bytes to detect and correct data bytes in error in each sector of a block. The method and the apparatus generates sector level check bytes for each sector in the block responsive to the data bytes in each sector according to a first level of an error correction code, and generates block level check bytes for a predetermined sector in the block responsive to the sector level check bytes of various sectors, including the predetermined sector, according to at least a second level of the error correction code.

Abstract: The present invention includes a method and apparatus to write and read copy protected data on a disc drive storage system by encoding and decoding data to be copy protected using servo wedge data as the encoding element. In one aspect, the drive is marked by a number generated from the servo wedge data.

Abstract: A magnetic transfer method includes a first step (ST103) of preparing a magnetic disk, a second step (ST105) of forming a layer of lubricant on the magnetic disk, a third step (ST108) of bringing a surface of the magnetic layer on the magnetic disk into close contact with a magnetic transfer master having a magnetic film formed on at least one side and magnetically transferring a pattern of the magnetic film on the magnetic transfer master onto the surface of the magnetic disk through application of an external magnetic field, and a fourth step (ST104, ST106) of burnishing at least a surface of the magnetic disk that comes into contact with the magnetic transfer master. The first step, the fourth step, the second step, the fourth step, and the third step are performed in the stated order.

Abstract: A method of designing a thermally-assisted magnetic recording apparatus having a magnetic recording medium, a heater and a magnetic head includes, determining a stable retention time tst for recorded magnetization and a thermal-fluctuation stability coefficient ?st calculated from ?(T)=KuV/kBT, where Ku is a magnetic anisotropy energy density, V is an activation volume, and kB is Boltzmann's constant, obtaining an equivalent degradation time tEQ calculated from tEQ=?(?tEQ), that sums values of ?tEQ within a period of time ?t for a time span during which the medium is substantially degraded, where ?tEQ=exp(ln(?t)????st) and ? is a thermal-fluctuation stability coefficient for a medium temperature T in ?t, and determining specifications of the medium, the heater and the magnetic head in a manner to meet the relationship of tEQ<tst.

Abstract: A disk drive of perpendicular magnetic recording method including a read head comprising a GMR element and a drive using a double-layered disk medium, is disclosed. In the magnetic field response characteristic of the GMR element, the relationship between the degree of nonlinearity and a pulse width at 50% threshold (PW50) of a differentiated read signal is used. The degree of nonlinearity of the GMR element is adjusted such that the PW50 is smaller than the maximum value. The read channel comprises a differentiation circuit for converting the read signal output from the GMR element into the differentiated read signal.

Abstract: A system and method for decoding magnetic media. Parallel decoders, each with a different equalization magnitude, are used to decode a read signal. A Viterbi metric is used to determine the direction and magnitude of equalization shift that best compensates for a systematic separation, such as pole tip recession. If optimal equalization has changed, the equalization coefficients of the decoders is shifted to compensate.

Abstract: An audio or other program signal is modified to provide protection against copying on a magnetic tape recorder. The signal from a source (10) is amplified (16) and then subjected to Fourier analysis (11) to determine the signal amplitude in a plurality of subbands across the audible range. The subband containing the component of greatest magnitude is selected on an adaptive basis and applied to a stored psycho-sensorial model (12), which determines the maximum amplitude of interference which can be masked by the selected subband. An anti-copy signal is generated (14) by complex division of the desired interference by a stored representation of the response of a tape recorder (13).

Abstract: A write driver circuit selectively provides a write current through a write head in first and second opposite directions. The write driver circuit is connected to the write head through an interconnect. The write driver circuit provides an incident write current signal through the interconnect to the write head, and also provides a reflection cancellation signal through the interconnect to the write head. In an exemplary embodiment, the incident write current signal is provided by providing an incident voltage signal across the write head, and the reflection cancellation signal is provided by providing a reflection cancellation voltage signal across the write head. In an exemplary embodiment, the reflection cancellation signal is a delayed and filtered version of the incident write current signal that cancels a reflected signal that is reflected at the interface between the interconnect and the write head due to impedance mismatching.

Abstract: A preamplifier system is provided for use with a magneto-resistive (MR) sensor. Included is an alternating current (AC) coupling module connected to the MR sensor for blocking a direct current (DC) voltage associated with an input signal, and filtering low frequency noise associated with the input signal. Also provided is a gain stage module coupled to the AC coupling module. The gain stage module includes a plurality of cascode field effect transistors (FETs) configured for amplifying the input signal, while reducing intrinsic noise and increasing operational bandwidth. Coupled to the gain stage module is a control circuit for feeding back an output of the gain stage module for bias regulation and disturbance rejection.

Abstract: The invention provides a signal transmission apparatus using a rotary transformer by which a wide bandwidth and a high transfer rate can be used without a significant increase of the cost. The signal transmission apparatus includes a transmission side circuit and a reception side circuit between which a rotary transformer is interposed. A passive element circuit including an inductance element is connected to an output stage of the rotary transformer in parallel to the transformer. The passive element circuit has an inductance value set substantially equal to or lower than an equivalent inductance value when the circuit of the rotary transformer side is viewed from the reception side circuit.

Abstract: A servo mark detector detects a servo mark from each servo information item detected by the servo detector. A counter measures a time period each time a servo mark is detected, thereby measuring a servo interval. A correction circuit corrects a time period T2 on the basis of the measured servo interval and an ideal servo interval. A determination circuit determines which one of the time period T2 and a time period T2? obtained by correcting the time period T2 should be used. A servo-sector-pulse-generating unit generates a servo sector pulse a time period T1 after the detection of each servo mark, and generates a pseudo servo sector pulse when the time period determined by the determination circuit has elapsed after the detection of each servo mark, if the next servo mark is not detected during the determined time period.

Abstract: A method for optimizing the read-to-write offset of a disk drive system in respect of a track is provided. In one aspect the method includes the step of determining a first read position amongst a range of test positions offset relative to the track on the basis of read signal strength. The method further includes the steps of calculating a subrange of test positions about the first read position, selecting a second read position from the subrange on the basis of bit error rates and setting the read-to-write offset as a function of the second read position. In addition a disk drive system including means for optimally setting the read-to-write offset in respect of a track is provided.

Abstract: A holder for magnetic transfer is formed by a chamber base and a chamber body which are moved toward and away from each other and form therebetween an inner space in which a master information carrier and a slave medium are accommodated and held in close contact with each other. The holder is provided at different parts with a first sealing portion for sealing the inner space between the chamber base and the chamber body and a second sealing portion allowing the pressing faces of the chamber base and the chamber body to move toward each other to press the master information carrier and the slave medium against each other with the inner space kept sealed.

Abstract: A master information carrier for magnetic transfer has a concentric irregularity pattern representing information to be transferred to a disc-like magnetic recording medium. The top surface of the protruding portions of the irregularity pattern is formed of magnetic material. The irregularity pattern is formed so that the width L [nm] in a circumferential direction of a protruding portion at a distance R [nm] from the center satisfies the condition L=&agr;(&ohgr;·&Dgr;T·R), 0.8≦&agr;≦1.4, wherein &ohgr; represents in [rad/sec] the angular velocity of the magnetic recording medium when a signal is read out from the magnetic recording medium after the magnetic transfer and &Dgr;T represents in [sec] a desired signal time width of a reproduction signal waveform in a magnetization transition region corresponding to an interval between the ends of the protruding portion in the circumferential direction.

Abstract: A data tape drive for recording information on the data tape of a tape cartridge has a transducer head with air bleed slots that define side walls, a tape guide, and a device for detecting damage to the transducer head and tape guide. The damage detection device has a conductor loop that is located along the outer edges of the air bleed slots and tape guide for detecting any brittle fracture damage that may be present. The conductor loop is a thin filament of wire that is preferably attached to the ends of the side walls. When the transducer head or tape guide experiences a fracture, such as a fracture in one of the side walls, the delicate filament breaks and forms an open circuit. The open circuit in the conductor loop is detected by the data tape drive so that remedial actions can be taken.

Abstract: A method of encoding and decoding data involving the simultaneous application of pulse amplitude modulation, pulse width modulation, and pulse position modulation systems to data intended for storage on a magnetic disk medium.

Abstract: A method for forming a magnetic pattern in a magnetic recording medium, which includes irradiating energy beams to a magnetic recording medium having a magnetic layer on a substrate via a photomask having a transmitting portion and a nontransmitting portion to heat locally an irradiated portion of the magnetic layer. The method also includes applying an external magnetic field to the magnetic layer. The transmitting portion and the non-transmitting portion of the photomask each has a reflectivity of energy beam of 30% or less in at least one surface facing the magnetic recording medium. By using techniques of heating a local portion and applying an external magnetic field in combination, a fine magnetic pattern can be effectively and accurately formed while the production of an interference fringe is suppressed.