JP2007149333A - Testing device for magnetic recording medium or magnetic head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize the high accuracy and acceleration of a magnetic recording medium or a magnetic head test in accordance with the high frequency processing of a magnetic disk drive. <P>SOLUTION: A disk reproduced signal is distributed into N and a sampling clock is distributed into N, phase difference is given to either the disk reproduced signal or the sampling clock, and N A/D converters and N memories which are provided to the disk reproduced signal are operated parallelly to thereby convert the disk reproduced signal into a digital value at a high speed, storing the digital value in the memories. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetic recording medium or a magnetic head inspection apparatus for inspecting a writable and readable magnetic recording medium or a magnetic head.

  Conventionally, a magnetic recording device has been used as an external storage device in an information processing apparatus such as a workstation. In particular, the magnetic disk device has been improved in the recording density, the recording frequency, and the price of the magnetic disk device due to the recent improvement of the magnetic body or magnetic head and the improvement of signal processing technology. It is well known that it plays a part in speeding up and cost reduction.

  In addition, magnetic disk devices are required to have high reliability for data recorded / reproduced as external storage devices, and inspection of magnetic disks or magnetic heads used in magnetic disk devices is performed at the actual use frequency. Alternatively, a method of inspecting by recording / reproducing test data using a magnetic head is often used.

  Particularly for magnetic disks, the test data recorded on the magnetic disk is recorded / reproduced, and the average amplitude value of the disk reproduction signal as shown in FIG. 11, for example, which is a test parameter recommended by the International Disk Drive Association (IDEMA). The parametric test for measuring the average pulse width of the disc playback signal at the 50% point of the TAA (Track Average Amplitude) or the average amplitude value TAA, etc. is performed to evaluate and inspect the disc to be inspected.

  Also, when writing / reading data with a fixed period to / from the magnetic disk, the disk playback signal amplitude is smaller than the missing error or average amplitude that is reproduced with an amplitude smaller than the average disk playback signal amplitude in data pulses. A certification test or the like for detecting a spike error or the like reproduced with an excessive amplitude is performed to evaluate and inspect the disc to be inspected.

  FIG. 10 is a diagram showing a configuration of a conventional magnetic recording medium or magnetic head inspection apparatus.

  In the inspection apparatus shown in FIG. 10, first, the magnetic disk 101 to be inspected is rotated by the disk rotating unit 103. In response to this, the test signal generating circuit 602 generates a test signal St of the frequency fo and the write control circuit. In addition to 603, the write control circuit 603 generates test data, and the write / read amplifier 601 converts the test data into a write current of a predetermined level to recognize a non-defective product or magnetic characteristics 102. The test data is sequentially written to the magnetic disk 101 via

  After the writing is completed, the disk reproduction signal is sent to the track on the magnetic disk 101 into which the test data is written as the two signals of the normal phase and the reverse phase sequentially by the R / W head 102 via the write / read amplifier 601. It is reproduced and sent to a level adjustment amplifier (AMP) 604. The two disc playback signals (signals corresponding to the test signal St having the frequency fo) Ss1 and Ss2, which are adjusted in level, are input to the TAA detection circuit 605, the PW detection circuit 607, and the waveform comparison circuit 608.

  The TAA detection circuit 605 is configured using, for example, a voltage comparison circuit (comparator), a control current source, a capacitor, and a track one-round integration circuit (not shown), and compares the capacitor charging voltage with the disk reproduction waveform voltage. If the disc playback signal voltage is higher than the capacitor charging voltage, the control current source is controlled by the comparator so as to charge the capacitor, and the envelope voltage near the peak value of the disc playback signal is detected. An envelope voltage integrated value for one period is detected. The average amplitude value TAA of the disc playback signal is detected by performing division processing on the envelope voltage integral value by the time of one track round, that is, by averaging the envelope voltage of the disc playback signal. To the slice level creation circuit 606.

  The CPU 111 of the control unit 110 reads an average amplitude value TAA that is an output of the TAA detection circuit, and performs TAA measurement.

  The slice level creation circuit 606 outputs a voltage of 50% of the TAA voltage level as a threshold value (slice level) as the slice setting 1 to the PW detection circuit 607, and the control signal P output by the CPU 111 of the control unit 110. As a result, a voltage value of P% with respect to the voltage level of TAA is output to the waveform comparison circuit 608 as slice setting 2.

  The PW detection circuit 607 includes, for example, a voltage comparison circuit (comparator), a control current source, a capacitor, and a track one-round integration circuit (not shown), and only during the time when the above-described disk reproduction signal exceeds the level of slice setting 1. The control current source is controlled by a comparator so as to charge the capacitor, and the capacitor charging voltage is integrated for one track period in the track one-round integration circuit to detect a pulse width integrated value (voltage). The CPU 111 of the control unit 110 divides the pulse width integrated value (voltage), which is the output of the PW detection circuit 607, by the charging current value of the control current source and the number of disk reproduction signal pulses during one track period, thereby performing the above-described processing. The average pulse width PW50 is measured.

  The waveform comparison circuit 608 is constituted by, for example, a voltage comparison circuit (comparator), and outputs a comparison result between the voltage value of the disk reproduction signal and the voltage value of slice setting 2 to the error detection circuit 609 as a detection signal. The error detection circuit 609 is composed of a gate circuit, and the peak position of the disk reproduction signal pulse is determined only for a predetermined set period based on the timing signal T corresponding to each bit of the test data sent from the test signal generation circuit 602 described above. A window pulse to be detected is generated, and an error such as a missing error or a spike error is detected from the detection signal output from the waveform comparison circuit 608 and the window pulse, and a bit error signal is synchronized with each bit of the timing signal T. Er is output to the error memory 610. The error detection circuit 609 can also switch the operation state according to the type of error so as to detect each error such as the above-described missing error and spike error in response to the control signal P from the CPU 111 of the control unit 110.

  The error memory 610 sequentially updates the address of the error memory 610 in response to the timing signal T generated by the test signal generation circuit 602, and the error signal Er output from the error detection circuit 609 is converted to defective data “1”, “0”. Are sequentially stored in the updated addresses. The CPU 111 reads the contents of the error memory 610 into the memory 112 via the bus and evaluates the magnetic disk 101 when the test of the entire circumference of the magnetic disk 101 to be inspected is completed.

In the above description, the inspection target is a magnetic disk. However, when the inspection target is a magnetic head, a magnetic disk having a good quality or a recognized magnetic characteristic is used as the magnetic head 101 in FIG. The R / W head 102 which is a head is evaluated.
Therefore, the conventional magnetic recording medium or magnetic head inspection apparatus shown in FIG. 10 performs the above-described circuit operation on the magnetic disk 101 to be inspected, thereby measuring the TAA or PW50 and realizing the parametric test. In addition, a missing test or spike error is measured to realize a certification test. As a known example related to the present technology, for example, Japanese Patent Laid-Open No. 10-83501 of Patent Document 1 describes an outline of a conventional certifier.
Japanese Patent Laid-Open No. 10-83501

  However, in the conventional magnetic recording medium or magnetic head inspection apparatus based on the analog method, for example, the disk reproduction signal amplitude value is detected using the envelope detection circuit as described above, so the TAA shown in FIG. 11 is strictly measured. In order to measure TAA and PW50 from the disc playback signal by further averaging using a track one-round integration circuit, for example, pulses in an arbitrary number of disc playback signal pulses that are discontinuous It has not been considered to perform a detailed and highly accurate inspection on a magnetic disk by detecting a width or an amplitude value.

  Further, in a conventional magnetic recording medium or magnetic head inspection apparatus using an analog method, when a disk reproduction signal becomes a high frequency, for example, in a TAA detection circuit, the response of the comparator does not keep up with the change in input and the TAA detection accuracy deteriorates. . When TAA is measured with a detection accuracy similar to that of the conventional method for future increase in frequency of the magnetic disk device, for example, the frequency bandwidth is 8 GHz or more with respect to a comparator having a performance of 54 dB / frequency bandwidth of 2 GHz at present. It is necessary to improve the IC process performance by four times or more, and it is difficult to realize with the current IC process technology. Therefore, there is a possibility that the conventional method cannot inspect the magnetic disk or the magnetic head with high accuracy at the actual use frequency in response to the higher frequency of the magnetic disk device in the future. There is a problem that the reliability of the magnetic disk or the magnetic head is reduced.

  Also, in a conventional magnetic recording medium or magnetic head inspection apparatus using an analog method, the disk reproduction signal is observed and measured using a digital sampling oscilloscope or the like, and inspection corresponding to high frequency of the magnetic disk apparatus is performed. Although there is a method, there is a problem that it is impossible to observe and measure a disk reproduction signal waveform with a digital sampling oscilloscope for writing non-periodic inspection data. Even when the disk playback signal waveform is measured with a digital sampling oscilloscope using periodic inspection data, the inspection time is required when the test data is recorded / reproduced on all tracks of the magnetic disk. The speed of the magnetic disk cannot be increased, and the throughput in the inspection process of the magnetic disk is reduced. Therefore, there is a problem that the price of the magnetic disk cannot be reduced.

  An object of the present invention is to provide a magnetic recording medium or magnetic head inspection apparatus capable of performing detailed and high-precision inspection on a magnetic disk or magnetic head.

  It is another object of the present invention to provide a magnetic recording medium or magnetic head inspection apparatus capable of performing detailed and highly accurate inspection on a magnetic disk or magnetic head.

  It is another object of the present invention to provide a magnetic recording medium or magnetic head inspection apparatus capable of realizing high-speed inspection of a magnetic disk or magnetic head in a magnetic recording medium or magnetic head inspection apparatus.

  Another object of the present invention is to provide a magnetic recording medium or magnetic head inspection apparatus capable of measuring the average amplitude value TAA and the average pulse width PW50 of reproduction test data at high speed in a magnetic recording medium or magnetic head inspection apparatus. Is to provide.

  The present invention relates to an inspection apparatus for recording test data on a magnetic recording medium with a magnetic head, and reproducing the recorded test data with the magnetic head and performing desired processing to inspect the magnetic recording medium or the magnetic head. The test data is converted into a digital value, and the magnetic recording medium or the magnetic head is inspected by performing arithmetic processing on the magnetic characteristics of the magnetic recording medium from the converted digital value. Device.

  In the present invention, the arithmetic processing uses the converted digital value to measure a peak value of the arbitrary reproduction test data or a threshold time exceeding or below an arbitrary threshold, and the peak value or the threshold time. Is a statistical calculation process or a frequency analysis calculation process for calculating an average value, a variance value, a deviation value, or a cumulative frequency value.

  The present invention also provides a magnetic recording medium in which test data is recorded on a magnetic recording medium by a magnetic head, and the recorded test data is reproduced by the magnetic head and subjected to desired processing to inspect the magnetic recording medium. Alternatively, in the magnetic head inspection apparatus, conversion means for converting reproduced test data into a digital value, holding means for holding the digital value converted by the conversion means, and the magnetic value from the digital value held in the holding means. An inspection apparatus comprising: data processing means for performing arithmetic processing related to magnetic characteristics of a recording medium, and inspecting the magnetic recording medium or the magnetic head.

  In addition, the present invention records test data on a magnetic recording medium by a magnetic head, and reproduces the recorded test data by the magnetic head and performs desired processing to inspect the magnetic recording medium. In the inspection apparatus, N (N is an integer) conversion means for converting the reproduced test data into a digital value, and a sampling clock control means for operating the N conversion means at a predetermined sampling frequency for each conversion means N holding means for holding the digital values converted by the N converting means, and data for performing arithmetic processing on the magnetic characteristics of the magnetic recording medium from the digital values held in the N holding means And an inspection device for inspecting the magnetic recording medium or the magnetic head.

  In addition, the present invention records test data on a magnetic recording medium by a magnetic head, and reproduces the recorded test data by the magnetic head and performs desired processing to inspect the magnetic recording medium or the magnetic head. In the inspection apparatus, N conversion means for converting the reproduced test data into digital values, a sampling clock control means for operating the N conversion means at a sampling frequency fADC for each conversion means, and the N number of conversion means N holding means for holding the digital values converted by the converting means, data processing means for performing arithmetic processing on the magnetic characteristics of the magnetic recording medium from the digital values held in the N holding means, and the data Analysis processing means for determining the magnetic recording medium from the output of the processing means, and for the frequency fin of the reproduced test data M, which is a ratio to the target sampling frequency fs, the frequency fin, and the sampling frequency fADC for operating the conversion means are in a relation of N ≧ M × fin / fADC and are an integer. It is an inspection device.

  In addition, the present invention records test data on a magnetic recording medium by a magnetic head, and reproduces the recorded test data by the magnetic head and performs desired processing to inspect the magnetic recording medium or the magnetic head. In the inspection apparatus, rotation control means for rotating the holding rotating means for holding the magnetic recording medium by the output of the first oscillating means that oscillates at a desired frequency, and facing the magnetic recording medium on the holding rotating means A recording means for recording the test data on the magnetic recording medium, and a reproducing means for reproducing the test data recorded on the magnetic recording medium by the magnetic head. N conversion means for converting the test data into a digital value; a reproduction signal distribution means for distributing and supplying the reproduced test data to the N conversion means; A clock signal based on the second oscillation means that oscillates at a frequency is converted by the sampling clock distribution means for operating the N conversion means at the sampling frequency fADC per conversion means, and the N conversion means. N holding means for holding digital values, a data processing means for performing arithmetic processing on the magnetic characteristics of the magnetic recording medium from the digital values held in the N holding means, and an output from the data processing means Analysis processing means for determining the magnetic recording medium, and control means for varying the oscillation frequency of the first oscillation means, the second oscillation means, and the sampling frequency for operating the conversion means, and The ratio M of the target sampling frequency fs to the frequency fin of the reproduced test data, the frequency fin, and the sample for operating the conversion means The magnetic recording medium inspection apparatus is characterized in that the pulling frequency fADC is an integer which is a relation of N ≧ M × fin / fADC.

  In addition, the present invention records test data on a magnetic recording medium by a magnetic head, and reproduces the recorded test data by the magnetic head and performs desired processing to inspect the magnetic recording medium or the magnetic head. In the inspection apparatus, rotation control means for rotating the holding rotation means for holding the magnetic recording medium by the output of the first oscillation means that oscillates at a desired frequency, and an index signal representing the number of rotations from the rotation control means And a mode and timing for generating a write mode signal indicating the start and end of writing and a read mode signal indicating the start and end of reading in response to the start signal and stop signal based on the encode signal indicating the rotation position Based on the control means and the write mode signal, the magnetic recording medium on the holding and rotating means The test data recorded on the magnetic recording medium by the magnetic head based on the read mode signal, and the recording means for recording the test data on the magnetic recording medium by the magnetic head arranged as described above Reproduction means for reproducing the reproduced test data, N conversion means for converting the reproduced test data into digital values, reproduction signal distribution means for distributing and supplying the reproduced test data to the N conversion means, The clock signal based on the second oscillating means that oscillates at a frequency of N is converted by the sampling clock distributing means for operating the N converting means at the sampling frequency fADC per converting means, and the N converting means. N holding means for holding the digital values, and data for performing arithmetic processing on the magnetic characteristics of the magnetic recording medium from the digital values held in the N holding means A processing means, an analysis processing means for determining the magnetic recording medium from an output of the data processing means, an oscillation frequency of the first oscillation means and the second oscillation means, and a sampling frequency for operating the conversion means M which is a ratio of the target sampling frequency fs to the frequency fin of the reproduced test data, and the sampling frequency fADC for operating the conversion means Is an integer that is a relation of N ≧ M × fin / fADC and is an integer.

  In addition, the present invention records test data on a magnetic recording medium by a magnetic head, and reproduces the recorded test data by the magnetic head and performs desired processing to inspect the magnetic recording medium or the magnetic head. In the inspection apparatus, L test data recorded on the magnetic recording medium are reproduced as L individual signals (L is an integer equal to or larger than 2) by L magnetic heads arranged opposite to the magnetic recording medium. L reproducing means, N converting means for converting the reproduced test data into digital values (N is an integer of 2 or more), and the N converting means for bringing the reproduced test data into a desired connection state Reproduction signal distribution means for distributing and supplying the data, sampling clock control means for operating the N conversion means at a predetermined sampling frequency per conversion means, and the N conversion means N holding means for holding the converted digital values; and data processing means for performing arithmetic processing on the magnetic characteristics of the magnetic recording medium from the digital values held in the N holding means. An inspection apparatus for inspecting a medium or a magnetic head.

  The present invention also provides a magnetic recording medium in which test data is recorded on a magnetic recording medium by a magnetic head, and the recorded test data is reproduced by the magnetic head and subjected to desired processing to inspect the magnetic recording medium. Alternatively, in the magnetic head inspection apparatus, the reproduced test data is converted into a digital value, and the magnetic recording medium or the magnetic head is inspected by performing arithmetic processing on the magnetic characteristics of the magnetic recording medium from the converted digital value. In the inspection apparatus, the arithmetic processing includes first frequency measuring means for selectively counting a plurality of counting means based on the converted digital value, and output of the first frequency measuring means. The first histogram processing means for measuring and outputting the average amplitude value of the reproduced waveform by histogram calculation processing, and 1 for the output of the first histogram processing means. Coefficient means for multiplying a count of 2, comparison means for comparing the output of the coefficient means with the output of the conversion means and outputting a comparison result, and only in a period when the output of the comparison means is at a predetermined level A pulse counting means that counts clock signal pulses that oscillate at a desired frequency, and a plurality of counting means that operate based on changes in the output of the comparing means and that select a plurality of counting means based on the pulses output by the pulse counting means Second frequency measuring means for performing a counting operation and second histogram processing means for measuring and outputting an average pulse width of the reproduced waveform by histogram calculation processing based on the output of the first frequency measuring means. An inspection apparatus for inspecting the magnetic recording medium or the magnetic head by measuring an average amplitude value and an average pulse width of the reproduced waveform in a desired period. .

  The present invention also provides a magnetic recording medium in which test data is recorded on a magnetic recording medium by a magnetic head, and the recorded test data is reproduced by the magnetic head and subjected to desired processing to inspect the magnetic recording medium. Alternatively, in the magnetic head inspection apparatus, the reproduced test data is converted into a digital value, and an arithmetic process relating to the magnetic characteristics of the magnetic recording medium is performed from the converted digital value to inspect the magnetic recording medium or the magnetic head. In the inspection apparatus, the arithmetic processing is based on the converted digital value, and the data written in the address of the first memory corresponding to the digital value is added using the first addition circuit. First frequency value holding means for measuring the frequency by writing to the same address, and histogram calculation processing based on the output of the first frequency value holding means The first histogram processing means for measuring and outputting the average amplitude value of the raw waveform, the threshold holding means for holding predetermined threshold data, and comparing the output of the threshold holding means with the output of the conversion means Based on the output of the comparison means for outputting the result, the pulse counting means for counting the clock signal pulse of the desired frequency only during the period when the output of the comparison means is at a predetermined level, and the output of the pulse counting means, Second frequency value holding means for measuring the frequency by adding the data written in the address of the second memory corresponding to the digital value using a second adder circuit and writing the same at the same address; Second histogram processing means for measuring and outputting the average pulse value of the reproduced waveform at a predetermined threshold value by histogram calculation processing based on the output of the frequency value holding means of By measuring the average amplitude value and the average pulse width of the reproduction waveform during a test apparatus characterized by inspecting the magnetic recording medium or magnetic head.

  According to the present invention, in an inspection apparatus for a magnetic recording medium or a magnetic head, test data for reproduction from the magnetic recording medium is converted into a digital value, and an arithmetic process related to the magnetic characteristics of the magnetic recording medium is performed from the converted digital value. As a result, a detailed and highly accurate inspection can be realized for the magnetic disk or the magnetic head.

  Further, according to the present invention, the reproduction test data from the magnetic recording medium is converted into a digital value at high speed using N number of conversion means, and the calculation relating to the magnetic characteristics of the magnetic recording medium is performed from the converted digital value. By performing the processing, it is possible to realize a detailed and highly accurate inspection on the magnetic disk or the magnetic head, and to achieve an effect that can realize an inspection corresponding to a higher frequency of the magnetic disk device in the future.

  Further, according to the present invention, in a magnetic recording medium or magnetic head inspection apparatus, it is possible to realize a high-speed inspection of a magnetic recording medium or a magnetic head by individually converting a plurality of reproduction test data into digital values and processing them. There is an effect.

  In addition, according to the present invention, it is possible to realize the high-speed measurement of the average amplitude value TAA and the average pulse width PW50 of the reproduction test data in the magnetic recording medium or magnetic head inspection apparatus.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a configuration diagram showing a first embodiment of the present invention. For example, test data set on a magnetic recording medium is recorded, the test data recorded on the magnetic recording medium is reproduced, and the test data is reproduced. FIG. 3 is a configuration diagram of a magnetic recording medium or magnetic head inspection apparatus that performs quality determination or characteristic measurement of the magnetic recording medium or magnetic recording head using a test data reproduction signal.

  In the magnetic recording medium or magnetic recording head inspection apparatus 1 shown in FIG. 1, as a recording operation, the disk rotating unit 103 holds and rotates the disk 101 which is a magnetic recording medium, and the write data generation unit 121 uses it for the inspection. Test data is generated and output, the output of the write data generation unit 121 is amplified and output by the write amplifier 122, the R / W head 102 is disposed on the track to be tested in the disk 101, Based on the output of the write amplifier 122, the magnetic field of the R / W head 102 is changed to perform a write operation on the disk 101 having magnetic characteristics, so that the test target track of the disk 101 during the rotation operation is set. The test data is recorded in the circumferential direction.

  Further, as a reproduction operation, a change in magnetic field based on test data recorded on the rotating disk 101 is detected by the R / W head 102, the detection signal is amplified by a reproduction amplifier 131, and a disk reproduction signal is output. The disk reproduction signal is divided into four (N = 4) by the disk reproduction signal distribution circuit 132, and four (N = 4) of the four divided disk reproduction signals are arranged by using independent sampling clock signals. The digital values are independently converted into digital values and output by the / D conversion circuits 141 to 144, and the digital values output from the A / D conversion circuits 141 to 144 are held in the memories 151 to 154.

  Based on the digitized disc playback signal data held in the memories 151 to 154, the data processing unit 135 calculates and outputs a target measurement value for the disc playback signal by arithmetic processing or the like, Based on the measured value of the disc reproduction signal output by the data processing unit 135, the analysis processing unit 136 performs a determination operation for calculating and determining whether or not the disc to be inspected is normal. Thus, the magnetic disk or magnetic head to be inspected is inspected.

  The disk rotation control unit 103 generates a disk rotation control signal based on the output of the variable frequency oscillation circuit 113 that oscillates at a predetermined frequency under the control of the CPU 111 disposed in the control unit 110, and sends the disk rotation control signal to the disk rotation unit 103. On the other hand, the disk 101 is controlled to rotate at a predetermined rotational speed. Since the CPU 111 controls the above-described variable frequency oscillation circuit 113 and a variable frequency oscillation circuit 114 described later independently, the disk 101 is controlled to perform a constant rotation operation independently of writing and reading of test data.

  Further, the disk rotation control unit 104 outputs an index signal (output one pulse per disk rotation) or an encoder signal (for example, one output per disk rotation) to the mode switching / timing control unit 137 based on the disk rotation number detection signal output from the disk rotation unit 103. 1024 or 2048 pulse output per disc rotation).

  The mode switching / timing control unit 137 operates in response to a reference clock signal output from the variable frequency oscillation circuit 114 that oscillates at a predetermined frequency under the control of the CPU 111 provided in the control unit 110, and performs internal recording / reproduction. In a sector discriminating unit (not shown), a sector counter is provided by a pulse counting circuit such as a counter, for example, and the sector counter is set to 0 using the index signal output from the disc rotation control unit 104 as shown in FIG. The sector position (hereinafter referred to as the sector position) of the disk where the R / W head 102 records / reproduces test data is discriminated by counting the number of pulses of the encoder signal.

  In addition, a start detection signal and a stop detection signal are internally generated by comparing the set start sector value and stop sector value with the sector position which is the output value of the sector counter, and a write mode or read operation for the disk 101 is performed. The start / end timing of the mode is determined, and a write mode signal or a read mode signal is generated to perform mode switching and timing control on each part of the inspection apparatus 1.

  FIG. 2 (1) shows an example in which an arbitrary sector is inspected by using an index signal and an encoder signal. For example, the disk rotation control unit 104 outputs 2048 pulses per rotation of the disk and outputs a start sector value. 6 is a diagram illustrating an example in which an inspection target period is discriminated and a write mode signal / read mode signal switching operation is performed when the stop sector value is 2044.

  Here, each mode period of writing and reading is a predetermined period determined by the user of the inspection apparatus 1, and the mode switching / timing control unit via the CPU 111 by a test program held in the memory 112 in the control unit 110. A start sector value and a stop sector value are set in a register or the like in 137. By the above-described recording / reproducing sector discriminating unit provided in the mode switching / timing control unit 137, the start detection signal outputs a voltage level representing a valid state only during a period in which the sector position and the start sector value match, and the stop detection signal Outputs a voltage level representing an effective state only during a period in which the sector position and the stop sector value match.

  Therefore, the mode switching / timing control unit 137 can discriminate between the start detection signal pulse output time and the stop detection signal output time as the inspection target period. For example, as shown in FIG. By generating the write mode signal in the period to be inspected by the eye and generating the write mode signal in the period to be inspected in the rotation of the disk N + 1, it becomes possible to test any sector of the disk 101.

  Although not particularly shown in FIGS. 1 and 2, the recording / reproducing sector discriminating unit can individually set the start sector value and the stop sector value for each mode when writing and reading test data. Thus, the test data writing period and the reading period can be set independently. In addition, by adding an index signal counting circuit and adding a disc rotation number discriminating function, it is possible to write and read test data at an arbitrary rotation number and an arbitrary sector.

  Next, FIG. 2 (2) shows an example in which the disk inspection is performed using only the index signal. Fig. 2 (2) shows that the write mode signal or read mode signal becomes valid and the first index signal pulse is output as the start pulse, and the next pulse after the index signal pulse used as the start pulse in the write or read mode is the stop pulse. In this example, writing or reading operation for one rotation of the disk is performed, that is, inspection for each track of the magnetic disk 101 is performed.

  FIG. 2 (2) shows an example in which a start pulse is output at the Nth and N + 2th rotations of the disk 101, and a stop pulse is output at the N + 1th and N + 3th rotations of the disk 101, for example. Here, FIG. 2 (2) shows an example in which a write or read operation is performed on the disk 101 in units of rotational speed, but the recording / reproducing sector discriminating unit operates with a clock signal of any frequency and the index signal. It goes without saying that any sector can be inspected by providing a counting circuit that performs a reset operation in order to have a function of performing a sector counting operation as in FIG. Nor.

  The mode switching / timing control unit 137 controls, in addition to the above-described sector discrimination operation, three operation states including, for example, a write operation, a read operation, and an analysis processing operation for each unit of the inspection apparatus 1. That is, at the time of the write operation which is the first operation state, the mode switching / timing control unit 137 determines whether to write to the disk 101 based on the write mode signal generated by discriminating the write sector by the sector detection function described above. A data generation signal timing signal set equal to the recording bit frequency is output to the write data generation unit 121 to perform write data generation control, and the R / W head 102 changes the write magnetic field according to the test data. By controlling so that the output terminal of the write amplifier 122 can be output by the write mode signal, the data write operation to the disk 101 is controlled.

  Further, during the write operation, the mode switching / timing control unit 137 disables the read mode signal, thereby allowing the sampling clock distribution circuit 132, the A / D conversion circuits 141 to 144, and the memory control signal distribution circuit 134. And the memories 151 to 154 output control signals so as to stop the respective operations, and control each unit so that a write signal to the disk 101 is not erroneously read as a disk reproduction signal. . The write operation described above describes the operation state of the inspection apparatus during the inspection target period (write) shown in FIG.

  In the read operation which is the second operation state, the mode switching / timing control unit 137 uses the above-described sector detection function to discriminate the read sector and generates a disc reproduction signal distribution circuit. The sampling clocks CLK1, CLK2, CLK3, and CLK4 are generated at the timing set in the sampling clock distribution circuit 133 in order to sample the N disk reproduction signals distributed by 132 in the A / D conversion circuits 141 to 144 arranged. The read mode signal and the sampling clock are output to the sampling clock distribution circuit 133 so as to be output.

  At the same time, the mode switching / timing control unit 137 switches the memory address in the memories 151 to 154 and sequentially stores the digital value of the disk reproduction signal obtained by the sampling operation in the memory 151 to 154. A read operation of the digitized disc reproduction signal data by outputting a memory control signal and a read mode signal, such as a write enable signal, to the memory control signal distribution circuit 134 at a frequency equal to or lower than the sampling clock. The timing control is performed.

  Further, the mode switching / timing control unit 137 stops the data generation signal timing signal for the write data generation unit 121 to control the write data generation unit 121 in the output stop state, and sets the output terminal of the write amplifier 122. For example, the writing mode signal is controlled to be in an invalid state in order to stop the output in a high impedance state or the like, thereby stopping the writing operation to the disk during the reading operation.

  That is, the mode switching / timing control unit 137 controls the write operation and the read operation so that the write operation and the read operation are not performed at the same time, so that the write operation and the read operation are not performed simultaneously. To do. The reading operation described above describes the operation state of the inspection apparatus during the inspection target period (reading) shown in FIG.

  In the analysis processing operation which is the third operation state, the mode switching / timing control unit 137 uses the average value of the disc playback signal (hereinafter referred to as data) based on the digital values held in the memories 151 to 154 (hereinafter referred to as data). Since the data processing unit 135 performs arithmetic processing for obtaining TAA), pulse width (PW50), etc., a data processing timing signal indicating whether or not the data written in the memories 151 to 154 is valid is used for the data processing. The analysis processing unit 136 outputs to the analysis processing unit 136 an analysis processing timing signal indicating whether or not the calculation processing result of the data processing unit 135 used for the calculation processing is valid.

  For example, if the data written in the memories 151 to 154 is valid, the analysis processing can be performed even during the above-described read operation or write operation. The data processing timing signal or the analysis processing timing signal is a write mode signal. And it is controlled independently from the read mode signal. That is, the analysis processing operation described above describes the operation state of the inspection apparatus that operates in parallel independently of either the inspection target period (write / read) or the non-inspection target period shown in FIG.

  In the magnetic recording medium or magnetic head inspection apparatus 1 shown in FIG. 1, a central processing unit (CPU) 111 disposed in the control unit 110 performs the operation of the entire inspection apparatus according to an operation control program written in the memory 112. Control.

  That is, in FIG. 1, the CPU 111 controls the oscillation frequency for the variable frequency oscillation circuits 113 and 114, sets timing control data such as start / stop sector values for the mode switching / timing control unit 137, and write / read mode, and writes Setting of write data to the data generation unit 121, a holding operation for reading the result of pass / fail judgment of the inspection target magnetic disk or magnetic head, the operation state of each part of the inspection apparatus, and the like, which is an output of the analysis processing unit 136, and holding the read data Communication processing with the host computer 2 arranged outside is performed.

  As shown in FIG. 1, in the inspection apparatus 1, a display device 160 is provided, and the measured value, arithmetic processing result, determination processing result, or inspection of the disk reproduction signal obtained by the data processing unit 135 under the control of the CPU 111. The operation state of each part of the apparatus is displayed to the inspection apparatus user.

  Here, in the magnetic recording medium or magnetic head inspection apparatus 1 shown in FIG. 1, the data processing unit 135 is configured by a logic circuit such as a DSP (Digital Signal Processor) that performs digital signal processing, and is a disk held in the memory 151. Interpolation processing is performed based on the digital value of the playback signal, and the amplitude value or average amplitude value for each pulse or pulse for each pulse at an arbitrary threshold value for any sector position or any number of disk playback signal pulses The width or average pulse width is calculated by calculation.

  That is, the magnetic recording medium or magnetic head inspection apparatus according to the present invention digitizes a disk reproduction signal in an arbitrary data reproduction period or all data reproduction period and holds it in a memory. As shown in FIG. 3, a statistical calculation process for calculating an average value, a variance value, a deviation value, a cumulative frequency value, etc. is performed on the amplitude value of the disc reproduction signal or the pulse width at an arbitrary threshold value, or the stored discrete value is obtained. On the other hand, by performing frequency analysis calculation processing such as FFT (Fast Fourier Transform), it is possible to perform a detailed inspection on the magnetic recording medium or the magnetic head.

  For the sake of explanation, FIG. 3 shows a statistical calculation process for the a to b-th consecutive disc playback signal pulses where a <b with respect to the pulses of the disc playback signal, but the present invention is limited to this. However, it goes without saying that it is possible to perform arithmetic processing on any number of disc reproduction signal pulses, for example, discontinuous pulses such as every other disc reproduction signal pulse.

  Further, in the magnetic recording medium or magnetic head inspection apparatus 1 shown in FIG. 1 described above, the configuration using the disk 101 which is a magnetic recording medium as an inspection target is described. The magnetic head can be inspected by performing recording / reproduction on the disk using the disk being inspected and the magnetic head to be inspected.

  Further, FIG. 2 illustrates a configuration and a method using discrimination of an inspection target section in a recording / reproducing track on the disc 101 using an index signal or an encoder signal from the disc rotation control unit 104. The inspection apparatus is not limited to this. For example, a sector determination signal or an inspection section start / end signal is recorded on the recording / reproducing track of the disk 101, and the sector determination signal or the inspection section start / end signal is reproduced. Thus, it is possible to determine the inspection target section and to inspect the magnetic recording medium or the magnetic head.

  In FIG. 2 (2), the inspection in units of the number of disk rotations using the index signal from the disk rotation control unit 104 is described. However, the inspection apparatus in the present invention is not limited to this, and for example, a disk Inspection of the magnetic recording medium or magnetic head is performed by measuring the number of rotations 101 and the recording time on the disk 101 and discriminating / controlling the recording time, or measuring the reproducing time and discriminating / controlling the reproducing time. Is possible.

  Next, the conversion operation of the disk reproduction signal into the digital value in the first embodiment according to the present invention shown in FIG. 1 will be described with reference to FIG.

  FIG. 4 shows an example of the conversion operation after the read mode signal becomes valid for the digital value conversion operation when four A / D conversion circuits and four memories are provided (N = 4). The D conversion circuits 141 to 144 each perform a sampling operation and a digital value conversion operation at a sampling frequency fADC, and the memories 151 to 154 each perform a digital value data holding operation at a frequency equal to the fADC.

  The sampling clock for controlling the operation of each of the A / D conversion circuits 141 to 144 is a sampling frequency fs targeted for the frequency of the disk reproduction signal. In the example shown in FIG. A sampling clock CLK0 that is four times the sampling frequency fADC of 144 (N = 4) is generated in the mode switching / timing control unit 137 during the period when the read mode signal is valid, and the sampling clock CLK0 is generated by the sampling clock distribution circuit 133. Dividing into four and distributing to CLK1 to 4 by dividing and controlling so that CLK0 outputs one pulse per four pulses to one of the A / D conversion circuits 141 to 144 Are respectively input to the A / D conversion circuits 141 to 144.

  The memory control signal is an address control signal that sequentially increases the memory address at the frequency fADC after the read mode signal is enabled for each of the memories 151 to 154 connected to the A / D conversion circuits 141 to 144. By outputting the write enable signal at the same frequency and in the same phase as the above address control signal, the digital value obtained by the conversion by the A / D conversion circuits 141 to 144 is output by the address control signal. Control is performed so as to perform a write operation to the controlled memory address.

  Here, in the sampling clock distribution circuit 133, the phase difference between the sampling clocks of CLK1 to CLK4 is set to, for example, 1 / N of the sampling time per circuit of the A / D conversion circuit, which is the reciprocal of fADC. On the other hand, by controlling the A / D conversion circuits 141 to 144 to operate in parallel, each of the A / D conversion circuits 141 to 144 converts the disk reproduction signal into a digital value in a time division manner, and samples data Data1 to 4 Are output in the time division order of S1-> S2-> S3-> S4-> S5-> S6->.

  That is, it realizes high-speed sampling and conversion into a digital value with N times the fADC with respect to the disc reproduction signal. In the above description, it has been described that high-speed sampling is realized by distributing the disc playback signal without giving a phase difference and giving the sampling clock a phase difference, but conversely, sampling is performed. Even if the clock distribution circuit 133 distributes the sampling clock without giving a phase difference and the disk reproduction signal distribution circuit 132 gives the phase difference to the disk reproduction signal and distributes and samples it, high-speed sampling can be similarly realized. Not too long.

  1 and 4 describe the case where N = 4, the parallel number N of A / D conversion circuits, the disk reproduction signal frequency fin, the sampling frequency fADC per one A / D conversion circuit, The relationship shown in Equation 1 holds between the ratio M of fin and the target sampling frequency fs (M = 16 in FIG. 4). However, fin uses either the n-order harmonic component fina of the disk reproduction signal frequency for measuring the target pulse portion for the disk reproduction signal or the repetition frequency component finb of the disk reproduction signal pulse. In the disk reproduction signal waveform shown in FIG. 4, a sine wave is used for explanation, and the sine wave does not have an n-order harmonic component as is generally known, and the repetition frequency and the fundamental frequency component are the same. This is the case where finb matches.

N ≧ M × fin / fADC Number 1
However, in Formula 1, N is an integer of 1 or more. The disk reproduction signal frequency fin is controlled by the CPU 111 disposed in the control unit 110 by varying the oscillation frequency of the variable frequency oscillation circuits 113 and 114, that is, the recording frequency of the write data and the number of disk rotations during recording / reproduction. And determined by the data pattern.

  Further, the ratio M between fin and the target sampling frequency is defined by using the target measurement accuracy for the characteristics of the magnetic recording medium or magnetic head to be inspected, and per one A / D conversion circuit. The sampling frequency fADC is a frequency obtained by distributing the sampling clock generated in the mode switching / timing control unit 137 with the maximum sampling frequency of the A / D conversion circuit as the upper limit.

  Accordingly, fin, fADC, and M described above can be set to known values and values intended by the inspection apparatus user in the magnetic recording medium or magnetic disk inspection apparatus 1 shown in FIG.

  Therefore, by finely sampling the disc playback signal in the time axis direction with the above-described configuration, for example, it is possible to convert a steep fluctuation of the disc playback signal into a digital value with high accuracy, for example, TAA or PW50, etc. By using high-precision digital value data when calculating the value by digital arithmetic processing, a magnetic disk or a magnetic head can be inspected with high accuracy.

  That is, the present invention converts a reproduced test data into a digital value in an inspection apparatus for a magnetic recording medium or a magnetic head, performs arithmetic processing on the magnetic characteristics of the magnetic recording medium from the converted digital value, and By inspecting the medium, it is possible to realize a detailed and highly accurate inspection of the magnetic recording medium or the magnetic head.

  According to the present invention, in a magnetic recording medium or magnetic head inspection apparatus, N (N is an integer) conversion means for converting reproduced test data into a digital value, and the N conversion means are converted into one conversion means. Sampling clock control means operating at a predetermined sampling frequency, N holding means for holding digital values converted by the N conversion means, and digital values held by the N holding means. Data processing means for performing arithmetic processing related to the magnetic characteristics of the magnetic recording medium, and by inspecting the magnetic recording medium, a detailed and higher-precision inspection can be realized for the magnetic recording medium or the magnetic head. is there.

  According to the present invention, in the magnetic recording medium or magnetic head inspection apparatus, as in the above-described embodiment, N conversion means, sampling clock reproduction means, N holding means, data processing means, and analysis processing means Can be implemented for a magnetic recording medium or a magnetic head at a high speed. Therefore, the magnetic disk or the magnetic head can be inspected with high accuracy in response to the future increase in the frequency of the disk reproduction signal.

  Next, a second embodiment according to the present invention will be described with reference to FIG. In FIG. 5, L R / W heads and playback amplifiers corresponding to the R / W heads are arranged on a disk which is a magnetic recording medium to be inspected, for example, disk playback in different tracks or sectors. A signal is detected by each R / W head and amplified by a reproduction amplifier to obtain L disk reproduction signals, and distributed to a plurality of N A / D conversion circuits in a disk reproduction signal distribution circuit. The changeover switch SW is controlled by the control signal to switch and output the distribution number and distribution destination of the disk reproduction signal, and each A / D conversion circuit converts it into a digital value at the sampling frequency fADC and outputs it to the memory.

  In FIG. 5, four (L = 4) R / W heads 301 to 304 and reproduction amplifiers 311 to 314 are input to the disk reproduction signal distribution circuit 132, and the distribution control signals S1 and S2 are switched to select the disk reproduction signal. A configuration example in which the distribution number of the disk reproduction signal is variably controlled with respect to four (N = 4) A / D conversion circuits 141 to 144 by changing the connection state between the input and output of the distribution circuit 132. Show.

Further, the sampling clock distribution circuit 133 operates the counter 331 using the sampling clock output from the mode switching / timing control unit 137 in FIG. 1, and the N comparison circuits 332 to 335 provide the counter in the read mode. A sampling clock cycle in which a sampling pulse is output only when the output of 331 matches N set values, the sampling clock is divided by N, and the phase difference between the sampling pulses is divided by N Is converted into an N-phase clock equal to a time equal to N, and a sampling clock having a frequency N times the sampling frequency fADC, which is an operating frequency of one A / D conversion circuit, is switched to the mode switching / timing control unit. The sampling frequency for each A / D conversion circuit is generated by 137. The sampling clock is supplied with the number fADC and the phase difference of N phase.
Here, the configuration using the counter 331 and the comparison circuits 332 to 335 as the sampling clock distribution circuit 133 is described. However, the circuit configuration is not limited to this, and for example, the sampling clock is set to N-phase using a delay element or the like. A configuration may be adopted in which N is distributed with a phase difference.

  In FIG. 5, a sampling clock having a frequency that is four times (N = 4) fADC is input to the sampling clock distribution circuit 133 to operate the counter 331, and four output states of the counter 331, that is, 00, 01, 10, 11 And the set value are compared by the comparison circuits 332 to 335, and the sampling clock CLK0 delayed by the delay circuit 330 is gated by the AND gates 336 to 339 based on the coincidence outputs of the comparison circuits 332 to 335. The configuration in which the outputs of the gates 336 to 339 are output to the A / D conversion circuits 141 to 144 as sampling clocks CLK1 to CLK4 is shown.

  The outputs of the A / D conversion circuits 141 to 144 are supplied to memories 151 to 154 similar to those shown in FIG. 1, and the outputs are connected to the data processing unit 135 and the analysis processing unit 136.

  FIG. 6 shows a second embodiment of the present invention shown in FIG. 5, in which the mode switching / timing controller 137 (not shown in FIG. 5) in FIG. FIG. 5 illustrates the sampling circuit operation when the sampling operation is started, and shows the case where the distribution control signal shown in FIG. 5 is S1 = 'L' and S2 = 'H'.

  Here, the disc reproduction signal in1 is an output signal from the R / W head 101 and the reproduction amplifier 311 and is distributed and inputted to the A / D conversion circuits 141 and 143, and the disk reproduction signal in2 is inputted to the R / W head 302 and the reproduction amplifier. 3 shows an example of an output signal from 312 that is distributed and input to A / D conversion circuits 142 and 144, that is, two types of disc playback signals to be output from disc playback signal distribution circuit 132 (L = 2). This is an example. Further, an example is shown in which the sampling operation is started by determining that the reproduction sector number of the disk reproduction signal in1 is 2 for the two disk reproduction signals in1 and in2.

  That is, in the sampling operation for each disk reproduction signal, as shown in FIG. 6, the disk reproduction signals distributed to the A / D conversion circuits 141 and 143 are sampled at the timings of the sampling clocks CLK1 and CLK3, respectively, and the sampling data Data1 and Data3 are sampled. The disk reproduction signals that have been converted and distributed to the A / D conversion circuits 142 and 144 are sampled at the timings of the sampling clocks CLK2 and CLK4, respectively, and converted into sampling data Data2 and Data4.

  Accordingly, the disc playback signal in1 is finally written as sampling data in the memories 151 and 153 (not shown) in the order of S1, S3, S5, S7,..., And the disc playback signal in2 is recorded as sampling data S2 → S4 →. The data is written in the memories 152 and 154 (not shown) in the order of S6 → S8 →.

  Here, for the sake of explanation, only the reproduction sector number of the disk reproduction signal in1 is used to determine the start of the sampling operation for the two disk reproduction signals in1 and in2. It is also possible to discriminate sector numbers individually and to inspect each set arbitrary track or sector section independently.

  Further, when the distribution control signal is set to S1 = "L" and S2 = "L" in the disk reproduction signal distribution circuit 132 shown in FIG. 5, this means that each of the four disk reproduction signals in1 to in4 (N = 4). Each of the distributed A / D conversion circuits 141 to 144 is distributed 1: 1 (L = 4), and the disk reproduction signals in1 to in4 are sampled at the frequency fADC.

  When the distribution control signal is set to S1 = "H" in the disk reproduction signal distribution circuit 132 shown in FIG. 5, this is an A / D conversion circuit 141 in which only four disk reproduction signals in1 (N = 4) are arranged. In this case, the circuit operation of the inspection apparatus 1 is equal to the circuit operation shown in FIG. 2, and is equivalent to sampling the disk reproduction signal in1 at a frequency four times that of fADC. The disc reproduction signal in1 is converted into a digital value in the order of S1, S2, S3, S4, S5,.

  Here, focusing on the sampling frequency fsample for one disk reproduction signal with the sampling frequency of each of the A / D conversion circuits 141 to 144 as fADC, fsample is equal to (N / L) × fADC, and is equal to the disk reproduction signal. By switching the distribution control signal, the sampling frequency can be variably controlled.

  That is, as described above, in the magnetic recording medium or magnetic head inspection apparatus, the disk reproduction signal frequency fin is controllable and is a known value, so that the A / D conversion circuit defined using the relationship shown in Equation 1 is used. By controlling the connection state of L disk playback signals in the disk playback signal distribution circuit with respect to the parallel number N, the sampling frequency fsample for one disk playback signal can be controlled with the relationship shown in Formula 2.

fsample = (N / L) × fADC number 2
Therefore, for example, when the frequency component targeted for measurement with respect to the disc playback signal is higher than the sampling frequency of the A / D conversion circuit, L = 1, that is, playback with one R / W head in the relationship shown in Equation 2. In a magnetic recording medium or magnetic head inspection apparatus that realizes a high-speed sampling operation using an amplifier and N A / D conversion circuits, a measurement target is used when a disk or magnetic head to be measured is used. When the frequency component of the disc playback signal is not higher than the sampling frequency of the A / D conversion circuit or when there is a margin in measurement accuracy, L> 1 (L = 2 in FIG. 5) in the relationship shown in Equation 2. In other words, by using L R / W heads, playback amplifiers and N A / D conversion circuits, different tracks on the disk can be measured simultaneously using L multiple heads. Becomes ability, throughput can be improved in the inspection process of the disc or the magnetic head.

  In the inspection apparatus according to the present invention, the number of disks to be inspected is not limited. For example, by using a plurality of magnetic heads and a reproducing amplifier corresponding to the magnetic head for a plurality of disks, A configuration in which a plurality of magnetic heads can be measured simultaneously and a disk transport device is provided to improve the throughput of the disk inspection may be adopted.

  Here, in FIGS. 5 and 6, for the purpose of explaining the second embodiment of the present invention, a variable frequency oscillation circuit, a test data writing function, a digital value data holding function obtained by digitizing a disk reproduction waveform, and An arithmetic processing function and a timing control function for calculating a desired measurement value from the digital value data are not described, but these functions are the same as those of the first embodiment according to the present invention shown in FIG. The magnetic recording medium or magnetic head inspection apparatus according to the present invention has these functions.

  5 and FIG. 6, the phase of the sampling clock is fixedly supplied for each A / D conversion circuit for the sake of explanation. However, the present invention is not limited to this, and for example, disc reproduction signal distribution A configuration is also possible in which the phase difference of the sampling clocks distributed in the sampling clock distribution circuit 133 is switched in accordance with the distribution control signal to the circuit 132, and sampling is performed at the sampling frequency shown in Equation 2 for each of the L disk reproduction signals. What is necessary is just to realize. Further, the sampling clock frequency may be variably controlled in accordance with the control of the distribution control signal, that is, the number of parallel A / D conversion circuits for one reproduction signal.

  That is, in the present embodiment, when the test data recorded on the magnetic recording medium is read and the test of the magnetic recording medium medium or magnetic head is performed in the magnetic recording medium or magnetic head inspection apparatus, R arranged R The reproduction signal distribution circuit is used to distribute a plurality of reproduction signals in parallel by distributing the L disk reproduction signals output from the / W head and the reproduction amplifier to N A / D conversion circuits. In addition, by separately converting to digital values and processing, it is possible to realize a high-speed inspection of the magnetic recording medium or the magnetic head.

  Next, a third embodiment according to the present invention will be described. In the magnetic recording medium or magnetic head inspection apparatus, the magnetic recording medium or magnetic head is inspected by measuring the average amplitude value TAA and the average pulse width PW50 with respect to the disk reproduction signal as described above. TAA and PW50 are obtained by measuring the amplitude and pulse width of the disk reproduction waveform and, for example, processing the average value for one round of the disk as shown in FIG.

  Here, when sampling the disc playback waveform at regular time intervals, the sampling density is low in the amplitude direction at the portion where the voltage change rate, that is, the slope of the disc playback waveform is large, and the disc playback waveform has a small slope. Sampling density is higher with respect to direction.

  For example, in the case of a disc playback signal as shown in FIG. 8 (1), the frequency of occurrence of sample values is high near 0 [V] and near the peak value. In this case, the sample value having the highest occurrence frequency in the vicinity of the disc playback signal peak value is substantially equivalent to the average amplitude TAA of the disc playback signal shown in FIG. Therefore, the TAA measurement is possible by measuring the occurrence frequency of the disc reproduction signal sample value and discriminating the sample value at which the occurrence frequency is the peak value.

  Further, as shown in FIG. 8 (2), the number of time measurement pulses is measured for each disk reproduction signal pulse while the disk reproduction signal amplitude is larger than the threshold voltage, and the number of pulses is measured in the same manner as the above TAA measurement. The frequency of occurrence for each number of pulses is measured, and the number of pulses with the highest frequency of occurrence is detected. Here, the threshold voltage is 50% of the above-mentioned TAA value. The pulse width time obtained by multiplying the reciprocal of the oscillation frequency of the time measurement pulse by the number of pulses is substantially equivalent to the average pulse width PW50 of the disc reproduction signal shown in FIG. Therefore, the PW50 measurement can be performed by measuring the pulse width of the disk reproduction signal for each reproduction signal pulse and determining the pulse width at which the frequency of occurrence of the pulse width is a peak value.

  FIG. 7 shows a magnetic recording medium or magnetic head inspection apparatus according to the present invention based on the measurement method described above when reproducing test data written on a magnetic disk and inspecting the magnetic disk or magnetic head. It is the figure shown about the structure of the apparatus which measures the average amplitude value TAA and average pulse width PW50 of a disk reproduction signal waveform.

  That is, in the magnetic recording medium or magnetic head inspection apparatus shown in FIG. 7, the test data is rotated from the magnetic disk 101 rotated by the disk rotating unit 103 and written with the test data via the R / W head 102 and the reproduction amplifier 131. The A / D conversion circuit 403 samples the signal according to the sampling clock CLK1 and converts it into a digital value.

  For example, the frequency measuring unit 404 includes a frequency counter for each digital value output from the A / D conversion circuit 403, and performs the A / D conversion based on the frequency count clock having the same frequency as the sampling clock CLK1. The count value of the frequency counter corresponding to the digital value output from the circuit 403 is incremented. The histogram processing unit 406 is composed of a gate circuit. For example, simultaneously with the end of the reading operation for one rotation of the disk 101, a plurality of frequency counter outputs arranged in the frequency measuring unit 404 are sequentially read and a peak near the disk reproduction waveform amplitude is obtained. The value is output as a TAA measurement value.

  In the magnetic recording medium or magnetic head inspection apparatus shown in FIG. 7, the digital comparator 408 outputs the output value of the A / D conversion circuit 403 and the threshold data in which the TAA output from the histogram processing unit 404 is 50%. And the counter enable signal En having the same number of pulses as the number of disk reproduction signal pulses is generated. The counter 409 performs a count operation with the clock CLK2 having a known frequency generated in the oscillation circuit 402 and the counter enable signal En, and measures the number of pulses of CLK2 during a period in which En is valid for each En pulse.

  The frequency measuring unit 405 includes a frequency counter for each discrete value output from the counter 409, for example, and uses the counter enable signal En as a frequency count clock to correspond to the discrete value output by the counter 409. Increase the count value. The histogram processing unit 407 includes a gate circuit. For example, simultaneously with the end of the reading operation for one rotation of the disk 101, a plurality of frequency counter outputs arranged in the frequency measuring unit 405 are sequentially read, and the frequency counter output value is maximum. The counter value corresponding to the frequency counter is output as a PW measurement value.

  Here, the PW measurement value is given by the number of pulses of the time measurement clock CLK2, but since the oscillation frequency of the time measurement clock CLK2 is known, a CPU (not shown) provided in the control unit or the like. A PW value is obtained by multiplying the reciprocal of the oscillation frequency of the time measurement clock CLK2 by the number of pulses.

  In the above description, a configuration using a plurality of counters in the frequency measuring units 404 and 405 is described. However, the present invention is not limited to this. For example, as shown in FIG. 9, memories 511 and 521, an adder circuit 512, A configuration using 522 may be adopted.

  That is, in the TAA measurement, based on the discrete value of the disc reproduction signal converted by the A / D conversion circuit 403, the data written in the address of the memory 511 corresponding to the digital value is added using the memory 511. It is also possible to measure the frequency by adding using 512 and writing to the same address. Also for the PW50 measurement, the frequency can be measured by adding the data written in the address of the memory 521 corresponding to the output value of the counter 525 using the memory 521 and writing the same at the same address using the adder circuit 522. Is possible.

  FIG. 9 shows a configuration example in which the operation of the counter 525 is controlled by comparing the outputs of the register 523 holding arbitrary threshold data and the A / D conversion circuit 403 using the digital comparator 524. According to the above, it is possible to measure the average pulse width with respect to an arbitrary threshold, and when measuring the PW50, it is only necessary to set the register 523 to measure 50% of the above-mentioned TAA measurement value. Needless to say.

  Although not specifically illustrated, for the PW50, the total pulse width and the number of pulses of the counter enable signal En during the test data reading period are measured, and the total value of the pulse width is calculated by the number of pulses after the reading is completed. It can also be measured by dividing and averaging.

  7, 8, and 9 do not describe the test data writing function and timing control function for the purpose of explaining the third embodiment according to the present invention. This is the same as the first embodiment according to the present invention shown in FIG. 1, and the magnetic recording medium or magnetic head inspection apparatus according to the present invention has these functions.

  That is, according to the present invention, in the magnetic recording medium or magnetic head inspection apparatus for measuring the average amplitude value TAA of the disk reproduction waveform or the average pulse width PW at an arbitrary threshold level, the frequency of the measured values is obtained by obtaining the frequency of the measured values. It is characterized in that both or one of them is statistically processed and measured.

It is a figure which shows 1st Embodiment in the inspection apparatus of the magnetic recording medium or magnetic head concerning this invention. It is a figure which shows the operation | movement of FIG. It is a figure explaining the statistical calculation process about the peak value and pulse width of a disk reproduction signal. FIG. 2 is a diagram for explaining an operation of sampling a disk reproduction signal using a plurality of A / D conversion circuits and converting it into a digital value in the first embodiment of FIG. It is a figure which shows 2nd Embodiment in the inspection apparatus of the magnetic recording medium or magnetic head concerning this invention. FIG. 9 is a diagram for explaining an operation of sampling a plurality of disc reproduction signals individually and converting them into digital values using a plurality of A / D conversion circuits in the second embodiment of FIG. It is a figure which shows 3rd Embodiment in the test | inspection apparatus of the magnetic recording medium or magnetic head concerning this invention. FIG. 9 is a diagram for explaining the principle of measuring an average amplitude value TAA and an average pulse width PW50 of a disk reproduction waveform in the third embodiment of FIG. It is a figure which shows another embodiment about 3rd embodiment of FIG. It is a figure which shows the structure of the inspection apparatus of the conventional magnetic recording medium or a magnetic head. It is a figure explaining the definition of the disk reproduction signal average amplitude value (TAA) with respect to a disk reproduction signal and the disk reproduction signal average pulse width (PW50) at the 50% point of TAA.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Magnetic disk / magnetic head inspection apparatus, 2 ... Host computer, 101 ... Disk, 102 ... R / W head, 103 ... Disk rotation part, 104 ... Disk rotation control part, 110 ... Control part, 111 ... CPU, 112 ... Memory 113, 114 ... Variable frequency oscillation circuit 121 ... Write data generator 122 ... Write amplifier 131 ... Reproduction amplifier 132 ... Disc reproduction signal distribution circuit 133 ... Sampling clock distribution circuit 134 ... Memory control signal distribution Circuit, 135 ... Data processing unit, 136 ... Analysis processing unit, 137 ... Mode switching / timing control unit, 141, 142, 143, 144 ... A / D conversion circuit, 151, 152, 153, 154 ... Memory, 160 ... Display Apparatus, 301, 302, 303, 304 ... R / W head, 311, 312, 313 314: Regenerative amplifier, 321, 322, 323, 324, 325, 326, 327, 328 ... Buffer amplifier (Buf), 330 ... Delay circuit, 331 ... Counter, 332, 333, 334, 335 ... Comparison circuit, 336, 337 338, 339 ... AND gate, 401, 402 ... oscillation circuit, 403 ... A / D conversion circuit, 404, 405 ... frequency measurement unit, 406, 407 ... histogram processing unit, 408 ... digital comparator, 409 ... counter, 410 ... Coefficient circuit 501, 502 ... Oscillator circuit, 503, 504 ... Delay circuit, 511, 521 ... Memory, 521, 522 ... Adder circuit, 523 ... Register, 524 ... Digital comparator, 525 ... Counter, 601 ... Write / read amplifier 602: Test signal generation circuit 603: Write control circuit 6 4 ... level adjustment amplifier (AMP), 605 ... TAA detection circuit, 606 ... slice level creating circuit, 607 ... PW detection circuit, 608 ... waveform comparison circuit, 609 ... error detection circuit, 610 ... error memory.

Claims (4)

Inspection of the magnetic recording medium in which the test data is recorded on the magnetic recording medium by the magnetic head and the recorded test data is reproduced by the magnetic head and the reproduced test data is subjected to a desired processing. In the device
A test apparatus for a magnetic recording medium for converting the reproduced test data into a digital value, performing an arithmetic process on the magnetic characteristics of the magnetic recording medium from the converted digital value, and inspecting the magnetic recording medium,
The arithmetic processing includes: first frequency measuring means for selectively counting the first plurality of counting means based on the converted digital values;
First histogram processing means for measuring and outputting the average amplitude value of the waveform of the reproduced test data by histogram calculation processing based on the output of the first frequency measuring means;
Coefficient means for multiplying the output of the first histogram processing means by a factor of 1/2;
A comparison means for comparing the output of the coefficient means and the output of the conversion means of the conversion means for converting the reproduced test data into a digital value and outputting a comparison result;
Pulse counting means for counting clock signal pulses that oscillate at a desired frequency only during a period when the output of the comparison means is at a predetermined level;
Second frequency measuring means that operates based on a change in the output of the comparing means and selectively counts the second plurality of counting means based on the pulses output from the pulse counting means;
Second histogram processing means for measuring and outputting the average pulse width of the waveform of the reproduced test data by histogram calculation processing based on the output of the second frequency measurement means,
An inspection apparatus for a magnetic recording medium, wherein the magnetic recording medium is inspected by measuring an average amplitude value and an average pulse width of a waveform of the reproduced test data in a desired period. Inspection of the magnetic recording medium in which the test data is recorded on the magnetic recording medium by the magnetic head and the recorded test data is reproduced by the magnetic head and the reproduced test data is subjected to a desired processing. In the device
A test apparatus for a magnetic recording medium for converting the reproduced test data into a digital value, performing an arithmetic process on the magnetic characteristics of the magnetic recording medium from the converted digital value, and inspecting the magnetic recording medium,
The arithmetic processing is based on adding the data written at the address of the first memory corresponding to the digital value based on the converted digital value using the first adder circuit and writing the same at the same address. First frequency value holding means for measuring the frequency;
First histogram processing means for measuring and outputting the average amplitude value of the waveform of the reproduced test data by histogram calculation processing based on the output of the first frequency value holding means;
Threshold holding means for holding predetermined threshold data;
A comparison means for comparing the output of the threshold value holding means with the output of the conversion means for converting the reproduced test data into a digital value and outputting a comparison result;
Pulse counting means for counting clock signal pulses of a desired frequency only during a period in which the output of the comparison means is at a predetermined level;
Based on the output of the pulse counting means, the frequency is measured by adding the data written in the address of the second memory corresponding to the digital value using the second adder circuit and writing to the same address. Second frequency value holding means;
Second histogram processing means for measuring and outputting an average pulse width of the waveform of the reproduced test data in the predetermined threshold data by histogram calculation processing based on the output of the second frequency value holding means. ,
An inspection apparatus for a magnetic recording medium, wherein the magnetic recording medium is inspected by measuring an average amplitude value and an average pulse width of a waveform of the reproduced test data in a desired period. In a magnetic head inspection apparatus for recording test data on a magnetic recording medium by a magnetic head, and reproducing the recorded test data by the magnetic head and performing a desired process on the reproduced test data. ,
An inspection apparatus for a magnetic head for converting the reproduced test data into a digital value, performing an arithmetic process on the magnetic characteristics of the magnetic recording medium from the converted digital value, and inspecting the magnetic recording medium,
The arithmetic processing includes: first frequency measuring means for selectively counting the first plurality of counting means based on the converted digital values;
First histogram processing means for measuring and outputting the average amplitude value of the waveform of the reproduced test data by histogram calculation processing based on the output of the first frequency measuring means;
Coefficient means for multiplying the output of the first histogram processing means by a factor of 1/2;
A comparison means for comparing the output of the coefficient means and the output of the conversion means for converting the reproduced test data into a digital value and outputting a comparison result;
Pulse counting means for counting clock signal pulses that oscillate at a desired frequency only during a period when the output of the comparison means is at a predetermined level;
Second frequency measuring means that operates based on a change in the output of the comparing means and selectively counts the second plurality of counting means based on the pulses output from the pulse counting means;
Second histogram processing means for measuring and outputting the average pulse width of the waveform of the reproduced test data by histogram calculation processing based on the output of the second frequency measurement means,
An inspection apparatus for a magnetic head, wherein the magnetic head is inspected by measuring an average amplitude value and an average pulse width of a waveform of the reproduced test data in a desired period. In a magnetic head inspection apparatus for recording test data on a magnetic recording medium by a magnetic head, and reproducing the recorded test data by the magnetic head and performing a desired process on the reproduced test data. ,
A test apparatus for a magnetic head for converting the reproduced test data into a digital value, performing an arithmetic process on the magnetic characteristics of the magnetic recording medium from the converted digital value, and inspecting the magnetic recording medium,
The arithmetic processing is based on adding the data written at the address of the first memory corresponding to the digital value based on the converted digital value using the first adder circuit and writing the same at the same address. First frequency value holding means for measuring the frequency;
First histogram processing means for measuring and outputting the average amplitude value of the waveform of the reproduced test data by histogram calculation processing based on the output of the first frequency value holding means;
Threshold holding means for holding predetermined threshold data;
A comparison means for comparing the output of the threshold value holding means with the output of the conversion means for converting the reproduced test data into a digital value and outputting a comparison result;
Pulse counting means for counting clock signal pulses of a desired frequency only during a period in which the output of the comparison means is at a predetermined level;
Based on the output of the pulse counting means, the frequency is measured by adding the data written in the address of the second memory corresponding to the digital value using the second adder circuit and writing to the same address. Second frequency value holding means;
Second histogram processing means for measuring and outputting an average pulse width of the waveform of the reproduced test data in the predetermined threshold data by histogram calculation processing based on the output of the second frequency value holding means. ,
An inspection apparatus for a magnetic head, wherein the magnetic head is inspected by measuring an average amplitude value and an average pulse width of a waveform of the reproduced test data in a desired period.

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