KR20080083523A - Method for executing defect scan of recording medium and disk drive using the same - Google Patents

Abstract

A method for executing defect scan of a recording medium and a disk drive using the same are provided to accurately check whether a defect is generated or not according to the type of defect by analyzing a frequency spectrum through FFT. A method for executing defect scan of a recording medium comprises the steps of: writing test data on a data recording area of a disc(S501); reading the test data recorded on the disc according to the size initially set(S502); carrying out FFT(Fast Fourier Transform) of the read signal; and determining whether a defect is generated or not by analyzing a DC component of an FFT spectrum and a harmonic element(S504).

Description

Method for executing defect scan of recording medium and disk drive using the same}

1 is a plan view of a head disk assembly of a disk drive to which the present invention is applied.

2 is an electrical circuit diagram of a disk drive to which the defect inspection method of a recording medium according to the present invention is applied.

3 is a block diagram of an apparatus for inspecting a defect of a recording medium according to a first embodiment of the present invention.

4 is a block diagram of an apparatus for inspecting a defect of a recording medium according to a second exemplary embodiment of the present invention.

5 is a flowchart of a method for inspecting a defect of a recording medium according to the present invention.

6 is a diagram showing a frequency spectrum after the fast Fourier transform according to the present invention.

FIG. 7 is a diagram illustrating an example of a read signal in which thermal asperity defects are generated in the time domain.

8 is a diagram illustrating an example of a read signal in which microdefects in a time domain are generated.

The present invention relates to a method and apparatus for inspecting a defect of a recording medium, and more particularly, to a method and apparatus for accurately inspecting a defect using a Fourier transform in a manufacturing process.

In general, a hard disk drive, which is one of data storage devices, contributes to computer system operation by reproducing data recorded on a disk by a magnetic head or recording user data on the disk. As such hard disk drives are gradually increasing in capacity, density, and miniaturization, bit per inch (BPI), the recording density in the direction of disk rotation, and track per inch (TPI), the recording density in the radial direction, are increasing. Is required.

The magnitude of the signal read by the read head when the hard disk drive reads the magnetized signal to the read head after writing data to the physically defective area of the disk by the write head. Is very small compared to the signal read out from the normal area, so that correct data restoration processing cannot be performed.

Accordingly, in order to guarantee the quality of the hard disk drive in the manufacturing process, the disk defect inspection is executed.

Defect inspection of a disc according to the prior art uses a method of determining a defect by reading test data into a data area of the disc, reading the data, and obtaining an average value of the read signals. Therefore, according to the related art, it is difficult to detect a micro defect of a high frequency component by determining whether the defect is an average value. In addition, there is a problem in that a separate circuit must be added to detect a TA defect (Thermal Asperity defect) of low frequency components.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a method for inspecting a defect of a recording medium and a disk drive using the same to analyze the frequency spectrum through Fourier transform and precisely detect whether there is a defect in each defect type. .

According to an aspect of the present invention, there is provided a method for inspecting a defect of a recording medium according to an embodiment of the present invention, writing test data to a data recording area of a disc, and reading test data recorded on the disc by an initial size. And fastening a Fourier transform of the read signal according to the size and analyzing the DC component and harmonic components of the fast Fourier transformed spectrum according to the type of the defect.

According to a preferred embodiment of the present invention, the defect determination step determines that a thermal asperity defect occurs when the DC component value of the fast Fourier transformed spectrum exceeds a first threshold value. do.

According to a preferred embodiment of the present invention, the defect determination step determines that a defect occurs due to a signal level drop when the third harmonic component value of the fast Fourier transformed spectrum is less than a second threshold value.

According to a preferred embodiment of the present invention, the defect determination step is that a micro defect of a high frequency component is generated when the fifth harmonic component value of the fast Fourier transformed spectrum exceeds a third threshold value. Determine.

According to an exemplary embodiment of the present invention, the defect determination step may include determining a high frequency component when the sum of harmonic component values from the fifth harmonic component of the fast Fourier transformed spectrum to an initial order exceeds a fourth threshold. It is determined that micro defects have occurred.

Disc drive according to an embodiment of the present invention to achieve the other technical problem, a magnetic head for recording information on the disk or to read information from or read the information from the disk and the magnetic head in the defect inspection process Write test data to the disc through the controller, and control to read the test data recorded on the disc by the initial size by the magnetic head, perform fast Fourier transform of the read signal by the size, and perform the fast Fourier transform. It characterized in that it comprises a controller for determining the presence or absence of a defect by analyzing the DC component and harmonic components of the spectrum for each type of defect.

According to a preferred embodiment of the present invention, the controller is a fast Fourier transform processing unit for fast Fourier transform the signal read for each size, the DC component and the harmonic components of the fast Fourier transformed spectrum in the Fourier transform processing unit by analysis type Defect determination unit for determining the presence or absence of defects and a defect listing processing unit for listing the defects determined by the defect determination unit for each type.

According to a preferred embodiment of the present invention, the defect determination unit compares the direct current component value of the fast Fourier transformed spectrum with the first threshold value, and the thermal asperi when the direct current component value exceeds the first threshold value. A thermal asperity defect determining unit for determining that a thermal defect is generated, and comparing the third harmonic component value and the second threshold value of the fast Fourier transformed spectrum, wherein the third harmonic component value is The fifth-order harmonic by comparing the fifth-order harmonic component value of the fast Fourier transformed spectrum with the fifth-order harmonic component value of the fast Fourier transformed spectrum If the component value exceeds the third threshold value, a microdefect determination unit that determines that a micro defect of a high frequency component is generated may be included. Can be.

According to a preferred embodiment of the present invention, the defect determination unit compares the direct current component value of the fast Fourier transformed spectrum with the first threshold value, and the thermal asperi when the direct current component value exceeds the first threshold value. A thermal asperity defect determining unit for determining that a thermal defect is generated, and comparing the third harmonic component value and the second threshold value of the fast Fourier transformed spectrum, wherein the third harmonic component value is A signal level defect determining unit that determines that a defect occurs due to a signal level drop when the second threshold value is less than the sum, and adds harmonic component values from the fifth harmonic component of the fast Fourier transformed spectrum to an initial order. And a fourth threshold value are compared with the value summed in the summation section and the summing section, so that when the summed value exceeds the fourth threshold value, It can comprise a microdefect determination part which determines that a micro defect has arisen.

DETAILED DESCRIPTION In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings which illustrate preferred embodiments of the present invention and the contents described in the drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

A hard disk drive, which is a data storage device to which the storage area management method of a recording medium according to the present invention is applied, is composed of a combination of an electrical circuit and a head disk assembly (HDA) composed of mechanical components.

1 shows a configuration of a head disk assembly (HDA) 10 of a hard disk drive to which the present invention is applied.

The head disk assembly 10 includes at least one magnetic disk 12 that is rotated by the spindle motor 14. The disk drive also includes a transducer 16 located adjacent to the surface of the disk 12.

The transducer 16 can read or write information on the rotating disk 12 by sensing and magnetizing the magnetic field of each disk 12. Typically transducer 16 faces the surface of each disk 12. Although illustrated and described as a single transducer 16, it should be understood that it consists of a write transducer for magnetizing the disc 12 and a separate read transducer for sensing the magnetic field of the disc 12. Read transducers are constructed from Magneto-Resistive (MR) devices. The transducer 16 is also commonly referred to as a magnetic head.

The transducer 16 can be integrated into the slider 20. The slider 20 is structured to create an air bearing between the transducer 16 and the surface of the disk 12. The slider 20 is coupled to the head gimbal assembly 22. The head gimbal assembly 22 is attached to an actuator arm 24 having a voice coil 26. The voice coil 26 is located adjacent to the magnetic assembly 28 to specify a voice coil motor 30 (VCM). The current supplied to the voice coil 26 generates a torque for rotating the actuator arm 24 relative to the bearing assembly 32. Rotation of the actuator arm 24 will move the transducer 16 across the disk 12 surface.

The information is typically stored in an annular track of the disc 12. Each track 34 generally includes a plurality of sectors. Each sector includes a data field and an identification field. The identification field is composed of a gray code identifying a sector and a track (cylinder). The transducer 16 is moved across the surface of the disc 12 to read or write information on other tracks.

The disk 12 is largely divided into a user area and a non-user area. The user area is an area where the user can substantially write or read data, and the non-user area is an area for storing information related to the disk drive.

2 shows an electrical system 40 capable of controlling a hard disk drive according to the present invention. The electrical system 40 includes a controller 42 coupled to the converter 16 by a lead / right (R / W) channel circuit 44 and a preamplifier 46.

The controller 42 may be a digital signal processor (DSP), a microprocessor, a microcontroller, or the like. The controller 42 reads information from or writes information to the disk 12 according to a command received from a host device (not shown in the drawing) via the host interface circuit 54. The read / write channel circuit 44 is controlled.

The controller 42 is also coupled to a voice coil motor (VCM) driver 48 that supplies a drive current to the voice coil 26. The controller 42 supplies a control signal to the VCM driver 48 to control the movement of the transducer 16.

The ROM 50 stores firmware and various control data for controlling the disk drive. Of course, programs for executing the flowchart of the method for inspecting the defect of the recording medium according to the present invention shown in FIG. 5 are also stored.

When power is supplied to the disk drive, the RAM 52 is loaded with disk drive information read from a maintenance cylinder (also called a system cylinder) area of the disk 12. In particular, the defect list information is stored in the maintenance cylinder area.

First, the operation of a general disk drive will be described.

In the data read mode, the disc drive amplifies the electrical signal sensed by the transducer 16 from the disc 12 by a fixed gain value in the preamplifier 46. The read / write channel circuit 44 then converts the signal read from the disk 12 into a digital signal in accordance with the sector pulse generated by the controller 42, and then decodes it. The decoded data is executed as an example in the controller 42 by an error correction process using the Reed Solomon code, and then converted into stream data and transmitted to the host device through the host interface circuit 54.

Next, in the write mode, the disk drive receives data from a host device (not shown) through the host interface circuit 54 and adds a parity symbol for error correction by the Reed Solomon code in the controller 42. And the disc 12 through the converter 16 to the write current amplified by the preamplifier 46 at the time when the sector pulse is generated after the encoding process is performed by the read / write channel circuit 44 to suit the recording channel. To record.

In the test mode of the defect inspection process for performing the defect inspection method of the recording medium according to the present invention, the controller 42 writes test data received from the host device to a data sector which is a recordable area of the disk 12. Perform Here, the test data is set as a single high frequency signal pattern in a recordable frequency band as one embodiment.

Then, the controller 42 checks the defect while sequentially reading the test data recorded on the disk 12 in the unit of the initially set size. For the detailed operation of checking the defect, the defects shown in FIGS. 3 and 4 are described. The sector inspection apparatus will be described with reference.

3 and 4 may be built in the lead / right channel circuit 44 or the controller 42, and the present invention is limited to the built-in controller 42 as an example for convenience of description. Shall be.

As illustrated in FIG. 3, the defect inspection apparatus according to the first exemplary embodiment includes a fast Fourier transform processor 310, a defect determination unit 320A, and a defect listing unit 330.

The fast Fourier transform processor 310 extracts and outputs a DC component value and each harmonic component value of the fast Fourier transform spectrum after performing a fast Fourier transform on the read signal in units of an initially set size. Here, the initially set size unit may be set to one sector size as an example. The spectrum after performing the fast Fourier transform is generated as shown in FIG.

The defect determining unit 320A is composed of a thermal aspelity defect determining unit 320-1, a signal level defect determining unit 320-2, and a micro defect determining unit 320-3.

As illustrated in FIG. 7, a phenomenon in which a DC component of a read signal is rapidly increased in a portion where a thermal asperity defect is generated. As shown in FIG. 8, a phenomenon in which high frequency noise is increased in a read signal occurs in a portion where micro defects are generated. It can also be seen that the magnitude of the read signal level appears in the third harmonic component in the fast Fourier transformed spectrum.

Using this principle, the defect determining unit 320A is divided into the following types of defects to determine whether there are defects.

That is, the thermal asperity defect determining unit 320-1 compares the direct current component value a (x) and the first threshold value TH1 of the fast Fourier transformed spectrum to compare the direct current component value a (x). ) Exceeds the first threshold value TH1 to generate a signal that determines that a thermal asperity defect has occurred.

The signal level defect determining unit 320-2 compares the third harmonic component value b (x) and the second threshold value TH2 of the fast Fourier transformed spectrum to compare the third harmonic component value b ( When x)) is less than the second threshold value TH2, a signal is determined which determines that a defect due to a signal level drop has occurred.

Next, the microdefect determination unit 320-3 compares the fifth harmonic component value c (x) and the third threshold value TH3 of the fast Fourier transformed spectrum, and compares the fifth harmonic component value c ( When x)) exceeds the third threshold TH3, a signal is determined that determines that a micro defect of high frequency components has occurred.

In the above, the first, second, and third threshold values TH1, TH2, and TH3 may be set through experiments when designing the disk drive.

The defect listing unit 330 inputs a signal for determining the defect occurrence by the type of the defect, and writes the position information and the defect generation type information on the disk on which the defect is generated in the defect table. Here, the defect table is stored in the maintenance cylinder area of the disk 12 or the ROM 50 after the defect inspection is completed.

4 shows a configuration of a defect inspection apparatus according to a second embodiment of the present invention.

The defect inspection apparatus according to the second embodiment of the present invention includes a fast Fourier transform processing unit 310, a defect determination unit 320B, and a defect listing unit 330.

Here, the fast Fourier transform processing unit 310 and the defect listing unit 330 are the same as the configuration means described in the defect inspection apparatus according to the first embodiment shown in FIG.

The defect determining unit 320B further includes a thermal aspelity defect determining unit 320-1, a signal level defect determining unit 320-2, a sum unit 320-4, and a microdefect determining unit 320-5. It consists of.

Here, the thermal asperity defect determining unit 320-1 and the signal level defect determining unit 320-2 are the same as the components described in the defect inspection apparatus according to the first embodiment shown in FIG. 3. Will be omitted.

That is, in the defect inspection apparatus according to the second embodiment, the portion for determining the thermal aspelity defect and the portion for determining the signal level defect of the defect inspection apparatus according to the first embodiment are the same. However, the defect inspection apparatus according to the second embodiment is different from the defect inspection apparatus according to the first embodiment in determining the micro defect.

Defect inspection apparatus according to the first embodiment determines the presence of micro-defect using only the fifth harmonic component value of the fast Fourier transformed spectrum, while in the second embodiment defect inspection apparatus from the fifth harmonic component to the initial order Using the sum of the harmonic component values of, it is determined whether or not a microdefect is generated as follows. Here, the initially set order may be set to eleventh as an example.

The adder 320-4 adds harmonic component values ranging from the fifth harmonic component of the fast Fourier transformed spectrum to an initially set order. In the case of the 11th order, the summation unit 320-4 adds the 5th harmonic component value, the 7th harmonic component value, the 9th harmonic component value, and the 11th harmonic component value of the fast Fourier transformed spectrum, and adds the sums. Output one value (c (x)).

The microdefect determining unit 320-5 compares the sum of the values c (x) and the fourth threshold value TH4 with the summation unit 320-4, so that the sum of the values c (x) is equal to zero. A signal which determines that a micro defect of a high frequency component has been generated when the threshold value TH4 is exceeded is generated.

Here, the fourth threshold value TH4 may also be set through experiments when designing the disk drive, and is set to a value larger than the third threshold value TH3 mentioned in the first embodiment.

Next, a method for inspecting a defect of a recording medium according to the present invention will be described in time series with reference to the flowchart of FIG. 5.

First, test signals are recorded in all recordable areas of the recording medium. That is, data of a test pattern, which is a single high frequency signal, is written to all data sectors of the disk as an example (S501).

Then, the test signal recorded on the recording medium is read in the unit of the initially set size using the read head (S502). As an example, the initially set size unit may be set to one sector size.

Next, after the fast Fourier transform of the read signal in units of the initially set size, the DC component values and the respective harmonic component values of the fast Fourier transformed spectrum are extracted (S503).

Next, it is determined whether or not a defect is generated for each type of defect using the DC component values and the respective harmonic component values of the fast Fourier transformed spectrum (S504). Here, the types of defects include thermal asperity defects, signal level defects, and micro defects.

Specifically, the thermal asperity defect determines that a thermal asperity defect has occurred when the direct current component value of the fast Fourier transformed spectrum exceeds the first threshold value, and the signal level defect has a high speed. When the third harmonic component value of the Fourier transformed spectrum is less than the second threshold value, it is determined that a defect occurs due to the signal level drop, and the microdefect determines that the fifth harmonic component value of the fast Fourier transformed spectrum is the third threshold value. In the case of exceeding, it can be determined that a micro defect of a high frequency component has occurred.

In the above, the micro-defect is the micro-defect of the high-frequency component when the sum of the harmonic component values from the fifth harmonic component of the fast Fourier transformed spectrum to the initially set order (eg, the eleventh order) exceeds the fourth threshold. It may be designed to determine that a defect has occurred.

The above thresholds 1, 2, 3, and 4 can be set to a value that can distinguish between the occurrence of a defect and an experiment when the disk drive is designed.

Next, in step 504 (S504), the result of determining the defect occurrence for each type of defect is updated in the defect list (S505). That is, the position information and the defect generation type information on the disk on which the defect was generated are written in the defect table.

In this way, by analyzing the frequency spectrum through the Fourier transform, it is possible to precisely detect the presence or absence of defects for each defect type.

The invention can be practiced as a method, apparatus, system, or the like. When implemented in software, the constituent means of the present invention are code segments that necessarily perform the necessary work. The program or code segments may be stored in a processor readable medium or transmitted by a computer data signal coupled with a carrier on a transmission medium or network. Processor readable media includes any medium that can store or transmit information. Examples of processor-readable media include electronic circuits, semiconductor memory devices, ROMs, flash memory, erasable ROM (EROM), floppy disks, optical disks, hard disks, optical fiber media, radio frequency (RF) networks, Etc. Computer data signals include any signal that can propagate over transmission media such as electronic network channels, optical fibers, air, electromagnetic fields, RF networks, and the like.

Specific embodiments shown and described in the accompanying drawings are only to be understood as an example of the present invention, not to limit the scope of the invention, but also within the scope of the technical spirit described in the present invention in the technical field to which the present invention belongs As various other changes may occur, it is obvious that the invention is not limited to the specific constructions and arrangements shown or described. That is, it is a matter of course that the present invention can be applied not only to various disk drives including hard disk drives, but also to various kinds of data storage devices.

As described above, according to the present invention, by performing the defect inspection through the frequency spectrum analysis according to the fast Fourier transform, the effect of determining whether or not the defect is generated for each kind of defect is generated. In particular, it is possible to inspect the thermal aspelity defects, the micro defects, and the signal level defects together in a single defect test, and the effect of inspecting the defects more accurately than the conventional technology is generated.

Claims (9)

Writing test data to a data recording area of the disc; Reading test data recorded on the disc for each initially set size; Fast Fourier transforming the read signal for each size; And And a defect determination step of analyzing the DC component and the harmonic components of the fast Fourier transformed spectrum according to the type of the defect to determine whether there is a defect. The method of claim 1, wherein the determining of the defect comprises determining that a thermal asperity defect occurs when the DC component value of the fast Fourier transformed spectrum exceeds a first threshold value. Defect inspection method of the recording medium. The recording medium of claim 1, wherein the determining of the defect comprises determining that a defect occurs due to a decrease in signal level when the value of the third harmonic component of the fast Fourier transformed spectrum is less than a second threshold. Defect inspection method. The method of claim 1, wherein the determining of the defect comprises determining that a micro defect of a high frequency component is generated when the fifth harmonic component of the fast Fourier transformed spectrum exceeds a third threshold. Defect inspection method of the recording medium. 2. The method of claim 1, wherein the determining of the defect is performed when the sum of the harmonic component values from the fifth harmonic component of the fast Fourier transformed spectrum to an initial order exceeds a fourth threshold value. Defect inspection method of a recording medium, characterized in that it is determined that a defect has occurred. A disk for storing information; A magnetic head for recording information on or reading information from the disk; And In the defect inspection process, test data is written to the disc through the magnetic head, and the test data recorded on the disc is read through the magnetic head for each preset size, and the signal read for the size is fast Fourier transformed. And a controller for analyzing the DC component and harmonic components of the fast Fourier transformed spectrum according to the type of the defect and determining whether the defect is generated. The method of claim 6, wherein the controller A fast Fourier transform processor for fast Fourier transforming the read signal for each size; A Defect Determination Unit for determining whether or not a Defect is generated by analyzing the DC component and the Harmonic Components of the fast Fourier Transformed Spectrum according to the Defect type; And And a defect listing processing unit for listing the defects determined by the defect determining unit for each type. The method of claim 7, wherein the defect determination unit Thermal comparing the DC component value of the fast Fourier transformed spectrum with a first threshold value and determining that a thermal asperity defect has occurred when the DC component value exceeds the first threshold value. Aspelity Defect Determination Unit; A signal level for comparing the third harmonic component value and the second threshold value of the fast Fourier transformed spectrum to determine that a defect occurs due to a signal level drop when the third harmonic component value is less than the second threshold value. Defect determination unit; And By comparing the fifth harmonic component value and the third threshold value of the fast Fourier transformed spectrum, when the fifth harmonic component value exceeds the third threshold value, a micro defect of a high frequency component is generated. And a micro-defect determination section for determining that it is. The method of claim 7, wherein the defect determination unit Thermal comparing the DC component value of the fast Fourier transformed spectrum with a first threshold value and determining that a thermal asperity defect has occurred when the DC component value exceeds the first threshold value. Aspelity Defect Determination Unit; A signal level for comparing the third harmonic component value and the second threshold value of the fast Fourier transformed spectrum to determine that a defect occurs due to a signal level drop when the third harmonic component value is less than the second threshold value. Defect determination unit; A summing unit for summing harmonic component values from the fifth harmonic component of the fast Fourier transformed spectrum to an initially set order; And The micro-defect determination unit which compares the summed value in the summation unit with the fourth threshold value and determines that a micro defect of a high frequency component is generated when the summed value exceeds the fourth threshold value. Disk drive characterized in that it comprises.

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