JP2007305286A - Disc defect inspection method, protrusion inspection device, and glide tester - Google Patents

Abstract

【Task】
It is possible to provide a disk defect inspection method and inspection apparatus capable of inspecting the waviness of the surface of the disk and improving the accuracy of determination of pass / fail of the disk.
[Solution]
This invention obtains a detection signal component corresponding to surface blurring due to rotation of the disk through a low-pass filter from the detection signal from the head, and compares the maximum value of the signal level with a predetermined reference value to determine pass / fail of the disk. To do. As a result, it is possible to extract an unacceptable disc that causes erroneous writing, erroneous reading, or a crash caused by the waviness of the surface of the disc even when the problematic height protrusion does not exist on the disc. it can.
[Selection] Figure 1

Description

  The present invention relates to a disk defect inspection method, a protrusion inspection apparatus, and a glide tester, and more particularly to a disk defect that can inspect the surface undulation of the disk and improve the accuracy of pass / fail judgment of a magnetic disk. The present invention relates to an inspection method and a glide tester.

In recent years, magnetic disks used as information recording media such as computers have been increasingly required to have a higher storage density and have been reduced in size.
A hard magnetic disk which is one of information recording media is manufactured by using a glass substrate or an aluminum substrate as a base and applying a magnetic film on the surface thereof. The magnetic film needs to be a smooth flat surface without projections and other irregularities. Therefore, the surface of the magnetic disk is polished and smoothed by a burnishing process. However, even if the surface is smoothed by the burnishing process, protrusions may remain. Therefore, the disk is inspected by a protrusion inspection device, and if there are any remaining protrusions, they are returned to the burnishing process and re-polished.
The protrusion inspection device rotates the magnetic disk at a predetermined peripheral speed to give a constant flying height to the slider of the thin film head (this slider may or may not have a thin film head) and to the top of the slider. Is equipped with a piezoelectric sensor (piezo element), and the vibration when the slider collides with the protrusion on the magnetic disk is converted into an electric signal by the piezoelectric sensor (piezo element) to obtain a protrusion detection signal to obtain the protrusion height. The detection technique is well-known (patent documents 1 and 2).
JP-A-6-341825 Japanese Patent Laid-Open No. 7-6365

As the recording density of magnetic disks (hereinafter referred to as disks) increases, the flying height of the magnetic head is decreasing. Recently, for a 1.8 inch or smaller disk, a slider of about 3 mm to 5 mm square is attached to the tip of a suspension spring of about 15 mm to 20 mm, and the distance between the thin film magnetic head and the disk is more than 10 nm. Is approaching to a distance of several tens of nanometers.
In addition, the rotation speed of a disk of 1.8 inches or more has shifted from 5,400 rpm to 7,200 rpm, and now it is from 15,000 rpm to 20,000 rpm, and a higher-speed hard disk drive (HDD). Is sold. Even with a disk of 1.8 inches or less, the number of revolutions is increasing from 4200 rpm to 5,400 rpm and beyond.
For this reason, the importance of the protrusion inspection (glide test) on the surface of the disk when determining pass / fail of the disk is increasing.

When the distance between the magnetic head and the disk approaches a distance of several tens of nanometers to several tens of nanometers, the height of the protrusion to be detected becomes ten nanometers or less. In addition, when such a projection height is detected, not only the projection of the disc but also surface blur due to the rotation of the disc becomes a problem. If the distance between the magnetic head and the disk becomes the above-described distance and the amount of surface blurring increases, it may cause erroneous writing or erroneous reading, or cause a head crash. For this reason, even if there are no protrusions of such a height as to cause a problem, the disk has to be rejected.
Surface wobbling is caused by the deterioration of the balance due to the waviness of the surface of the disk and the eccentricity of the disk with respect to the center of rotation, especially when the thickness is 0.3 mm to 0.5 mm as in the case of a recent glass disk. Sometimes surface wobbling is likely to occur due to the waviness of the disk surface.
SUMMARY OF THE INVENTION An object of the present invention is to solve such a problem of the prior art, a disc capable of inspecting the waviness of the surface of the disc and improving the accuracy of the pass / fail judgment of the disc. A defect inspection method will be provided.
Another object of the present invention is to provide a protrusion inspection apparatus that can improve the inspection accuracy of pass / fail of a disk by inspecting surface blurring together with inspection of protrusions existing on the surface of the disk.
Still another object of the present invention is to provide a glide tester capable of improving the accuracy of disc pass / fail inspection by inspecting surface waviness as well as inspection of protrusions existing on the surface of the disc.

In order to achieve such an object, the disk defect inspection method, projection inspection apparatus or glide tester according to the present invention has a structure in which a magnetic disk is rotated at a predetermined peripheral speed and a head mounted with a piezoelectric sensor on a slider is moved to a predetermined flying height. In the defect inspection of the disk, in which the electric signal from the piezoelectric sensor is obtained as a detection signal and inspected the disk
Passing the detection signal through a low-pass filter to obtain a detection signal component corresponding to the surface blur caused by the rotation of the disc, and comparing the maximum value of the level of this signal component with a first predetermined reference value, the pass / fail judgment of the disc is determined It is.

As described above, the present invention obtains a detection signal component corresponding to surface blurring due to rotation of the disk through a low-pass filter from the detection signal from the head, and compares the maximum value of the signal level with a predetermined reference value. Judge whether or not As a result, even if there is no problem height projection on the disc, it is possible to extract an unacceptable disc that causes erroneous writing, erroneous reading, or crash caused by the waviness of the surface of the disc.
Here, the reason why the surface blur component signal is obtained through the low-pass filter is that when the disk rotates, a disk having a waviness on the surface or an eccentric disk tends to cause surface vibration that vibrates up and down according to the rotation of the disk. . Moreover, the amount of blur is larger than that of a normal disk. When the amount of surface blur is detected, not only the surface waviness but also the surface blur of the eccentric disk is included, but when the thickness is 0.3 mm to 0.5 mm as in the recent glass disk, It is easy to cause surface shake due to the waviness of the disk surface, and an eccentric disk that causes more than a certain amount of surface shake can easily be handled as a failed disk because erroneous writing and reading are likely to occur, and the latter For this reason, such an eccentric disk is regarded as a disk similar to the undulation of the disk surface and is included in the undulation of the disk surface.
That is, according to the present invention, the amount of surface wobbling of the disc when the disc rotates is detected as the amount of waviness on the surface of the disc, and the pass / fail of the disc is determined based on the amount.

By the way, at present, the disc is polished and smoothed so that the height of the protrusion is, for example, 10 nm or less in the burnish process, but the height of the protrusion to be detected is 10 nm, Below this, for example, when the thickness is 8 nm or less, the collision signal between the protrusion and the slider obtained on the piezoelectric sensor affixed to the top of the slider having a size of 5 mm square or less is not a vibration waveform. Noise is put on the peak waveform as shown in (b).
The frequency corresponding to the surface shake obtained from the protrusion detection head as described above depends on the number of revolutions of the disk, but the number of revolutions of the disk is considered to be 30,000 rpm or less at present, The vibration frequency detected by the piezoelectric sensor through the vibration of air by rotating the disk at 30,000 rpm or less is about 100 kHz to 500 kHz. Therefore, a signal whose amplitude increases in the range of 100 kHz to 500 kHz according to the amount of surface blur can be obtained by a piezoelectric sensor attached to the upper part of a slider having a size of 5 mm square or less.
On the other hand, in the slider having the above-mentioned size, the protrusion detection signal has a frequency of 1 MHz to 2 MHz. Therefore, the surface blurring is divided into a lower-frequency filter and a higher-frequency filter at 500 kHz. The component detection signal and the protrusion detection component detection signal can be obtained separately.
As a result, it is possible to inspect the surface of the disc, which has not been subject to conventional determination, by detecting the amount of surface blur of the rotating disc by obtaining the detection signal of the surface blur component. The accuracy of determining such a defective disk can be improved.

FIG. 1 is a block diagram centering on a protrusion / disk surface waviness detection circuit portion to which the disk defect inspection method of the present invention capable of detecting disk surface waviness is applied, FIG. 2 is an explanatory view of the detected waveform, and FIG. FIG. 4 is a block diagram of the glide tester of the present invention, and FIG. 4 is an explanatory diagram of the protrusion detection head.
In FIG. 3, a glide tester 10 includes a disk rotation mechanism 2, two protrusion detection heads 3 and 3 corresponding to both surfaces of the disk 1, and a head carriage 4 that seeks the protrusion detection head 3 to a predetermined track. A projection / surface waviness detection circuit 5 that receives a detection signal from the projection detection head 3, a carriage control circuit 6, a peripheral speed control circuit 7, and a data processing / control device 9. In the figure, the polishing head of the glide tester is omitted.
The disk rotation mechanism 2 includes a spindle 2a for mounting the disk 1 to be inspected, and a motor 2b for rotating the spindle 2a. The spindle 2a is provided with an encoder, and generates an index signal IND serving as a rotation reference for one rotation of the disk.

In FIG. 3, O is the rotation center of the disk. In FIG. 3, the relationship between the disk 1 and the carriage 4 as viewed from above is shown together with the disk 1 as viewed from the side cross section.
As shown in FIG. 1, the data processing / control device 9 includes a microprocessor (MPU) 21, a memory 22, an interface 23, a CRT display (CRT) 24, and the like. These are connected to each other by a bus 25.
As shown in FIGS. 3 and 4, the protrusion detection head 3 corresponding to the surface of the disk has a slider 3a and a support spring 3b attached to the arm 41 of the head carriage 4, and a piezoelectric element 8 as a piezoelectric sensor is the slider 3a. It is mounted on the top head of the top surface. The arm 41 is fixed to the moving table of the head carriage 4.
The shield wiring lines 8a and 8b (see FIG. 3) for extracting the detection signal from the piezo element 8 are connected to the protrusion / surface waviness detection circuit unit 5.

In the projection inspection, the data processing / control device 9 controls the drive of the voice coil motor (not shown) of the head carriage 4 by the carriage control circuit 6 under the command of the MPU 21 to move the moving table of the head carriage 4. Then, both the front and back protrusion detection heads 3 and 3 are loaded on the front and back surfaces of the disk 1, respectively, and a predetermined track is accessed by the protrusion detection heads 3 and 3.
At this time, the disk 1 is rotated at a reference constant circumferential speed V _C by the motor 2 b controlled by the circumferential speed control circuit 7, and the slider 3 a of each protrusion detection head 3 is moved by the air flow generated by this rotation. Ascend at a certain height from the surface. Therefore, if a protrusion having a height higher than a certain height is present on the disk surface, it collides with the slider 3a and the piezo element 8 vibrates or deforms, and its output signal is input to the protrusion / surface waviness detection circuit section 5. Both protrusions and surface waviness are generated as detection signal components.
Such detection signal components of the protrusion detection head 3 are processed by the MPU 21, protrusion data or surface waviness data is stored in a predetermined area of the memory 22, and an image showing the position is displayed on the CRT display 24.

In the above, the reason for the constant circumferential speed V _C is the flying height of the slider 3a is changed, it is not preferable to cause variation in the projection detection performance, regardless of the position of the slider 3a of the disk, the flying height This is for always maintaining a constant value.
Here, the peripheral speed V _C of the disk is determined with respect to the protrusion height that becomes NG by inspecting a standard disk having various protrusion heights. If there is a protrusion with a certain protrusion height that will be NG (fail) on the disk, the disk is NG.
In the standard disk, protrusions having a certain height are formed for each circumferential track by a thin film edging technique, and the protrusion height is different for each track. Therefore, this makes it NG circumferential speed V _C is determined, which is previously stored in the parameter area 22d of the memory 22 (see FIG. 1). This type of standard disc is disclosed in US Pat. No. 5,898,491.
The flying height of the slider 3a in this embodiment is about 8 nm from the surface of the disk 1, the size of the slider 3a is about 3 mm square, and the size of the piezo element 8 is also about 2 mm × 3 mm. The protrusion / surface waviness detection circuit unit 5 generates detection signal components of both protrusions and surface waviness (surface wobbling) at a peripheral speed V _C of a flying height of 8 nm when the disk is rotated.

FIG. 1 shows a circuit configuration of the protrusion / surface waviness detection circuit unit 5. In FIG. 1, a detection signal from the piezo element 8 of the protrusion detection head 3 is input to the protrusion / surface waviness detection circuit unit 5 via a read amplifier 11 and a buffer amplifier 12. These circuits are provided corresponding to the protrusion detection heads 3 on the front and back sides, but only one of them is shown in the figure.
The protrusion / surface waviness detection circuit unit 5 receives a detection signal as an input signal by the variable amplifier 14 via the buffer amplifier 13 and amplifies it by a predetermined amount (1 to 100 times) to constitute a filter circuit unit. The signals are input to the bandpass filter (H · BPF) 15 and the low-pass bandpass filter (L · BPF) 16, respectively. Here, the bandwidth of the H · BPF 15 is 1 MHz ± 100 kHz, and the bandwidth of the L · BPF 16 is 300 kHz ± 50 kHz.
The bandwidth of H · BPF 15 can be selected from a frequency range of ± 150 kHz or ± 150 kHz or less with a frequency in the range of 1 MHz to 2 MHz as the center frequency, and the bandwidth of L · BPF 16 is a frequency of 200 kHz to 400 kHz. The center frequency may be selected from a range of frequencies of ± 100 kHz or less than ± 100 kHz.
The output of the H · BPF 15 is input to a maximum voltage value hold circuit (peak hold circuit) 17 where the maximum peak voltage value in one track circumference is held here, and an A / D conversion circuit (A / D) A / D converted at 18 and sent to the data processing / control device 9.
On the other hand, the output of the L · BPF 16 is input to the maximum voltage value hold circuit 19 where the maximum voltage value (maximum amplitude value) in one track circumference is held here, and the A / D conversion circuit (A / D) A / D converted at 20 and sent to the data processing / control device 9. The maximum voltage value hold circuit (peak hold circuit) 17 and the maximum voltage value hold circuit 19 each have a hold value reset by a rising signal of the index signal IND (FIG. 2A).

FIG. 2 is an explanatory diagram of the detected waveform. In the projection inspection, each time the index signal IND is generated, the carriage control circuit 6 causes the front and back projection detection heads 3 and 3 to perform the projection inspection of the positioned track, and in response to the generation of the next index signal IND. It is moved and positioned on the next inspection track, and the track of the disk 1 to be inspected is sequentially updated. As a result, whether or not there is a protrusion on each track is inspected for each track, and the protrusion inspection for all tracks is performed.
FIG. 2A shows an index signal IND that serves as a reference for rotation of one round of the disk, and FIG. 2B shows a detection signal generated by the protrusion detection head 3 that has collided with the protrusion in a certain track.
Microvibration components such as high-frequency noise on the detection signal are excluded from the detection signal for convenience of explanation. It can be easily removed by a noise filter or the like provided in the amplifier. The signal is input as an input signal to the protrusion / surface waviness detection circuit unit 5 via the read amplifier 11 and the buffer amplifier 12, and further input to the filter circuit unit via the buffer amplifier 13 and the variable amplifier 14 of the detection circuit unit 5. 2B is obtained as the output of the H · BPF 15, and the surface blur signal component A of FIG. 2D is obtained as the output of the L · BPF 16. Is obtained.

Here, the reason why the surface blur component signal A in FIG. 2D is obtained as the output of the L · BPF 16 is that the disk 1 has a waviness on the surface when the disk 1 rotates or a disk with an eccentricity according to the rotation of the disk. This is because the surface vibration that vibrates up and down becomes large, and the amount (amplitude) of the vibration gradually increases from the center toward the outside. Therefore, the signal is as shown in FIG. Most of them are caused by waviness on the surface, but here, as described above, the eccentric disk is also put in the surface waviness to judge the disk defect.
Since the piezo element 8 floats with air and is restrained on the disk surface by the support spring 3b via the slider 3a, if surface blurring increases, the air also vibrates in accordance with the vibration of the slider 3a, and the air vibration Is transmitted to the piezo element 8 through the slider 3a, and a surface blur component signal A is generated in the piezo element 8.
The waveform of such a signal component is not limited to the protrusion inspection of 8 nm or less described in this embodiment, but is 5 mm square or less when the protrusion of about 10 nm or less is inspected. When a piezoelectric sensor is attached to the upper part of the slider and a detection waveform is obtained when it collides with a protrusion on the disk, it is possible to obtain a substantially similar waveform.

In the shape of the current thin film head slider (5 mm square or less), when the frequency range of the voltage is examined with respect to a protrusion of 10 nm or less, the surface blur component of the frequency in the range of 300 kHz ± 50 kHz Signal A could be captured. Therefore, the band of L · BPF 16 is set to 300 kHz ± 50 kHz, and the signal of the surface blur component A is obtained at the output.
In this embodiment, the protrusion detection component signal B and the surface blur component signal A are applied to a maximum voltage value hold circuit (peak hold circuit) 17 and a maximum voltage value hold circuit 19, respectively. VB and VA (see FIGS. 2D and 2E) are converted into digital values and input to the data processing / control device 9.
The memory 22 of the data processing / control device 9 stores a defect data collection program 22a, a projection presence / absence determination program 22b, a surface waviness determination program 22c, a peripheral speed Vc, determination reference thresholds VhB, VhF, and the like in a parameter area 22d. A work area 22e and the like are provided.

The MPU 21 executes the defect data collection program 22a, reads the peripheral speed Vc set in the parameter area 22d, inspects all the tracks on the disk 1, and detects the protrusion detection component B and the surface blur component signal A. The respective maximum voltage values VB and VA are obtained for each track and stored as digital values in the work area 21e of the memory.
When there are a plurality of protrusions in one track, the maximum values VB and VA are detected from these component signals. Further, a protrusion is detected for each track. When the collection of the protrusion detection data for all tracks is completed, the MPU 21 calls the protrusion presence / absence determination program 22b.
The MPU 21 executes the protrusion presence / absence determination program 22b to determine whether or not the maximum peak voltage value for the protrusion stored in the work area 21e of the memory exceeds the determination reference threshold value VhB. If it has exceeded, it is determined as NG and processing for storing the inspection disk in the NG cassette is performed. Otherwise, the MPU 21 calls the surface waviness determination program 22c.

The MPU 21 executes the surface waviness acceptance / rejection determination program 22c to determine whether or not the maximum voltage value for the surface shake stored in the work area 21e of the memory exceeds the determination reference threshold value VhF. If it has exceeded, the test disk is determined to be NG and the test disk is stored in the NG cassette. When not exceeding, it is determined as pass (GD) and the inspection disk is stored in a pass cassette.
Of course, in the above inspection, even when no protrusion is detected, the signal A of the surface blur component is present.
In the above determination order, the MPU 21 may first execute the surface waviness determination program 22c and then execute the protrusion presence / absence determination program 22b. In this case, the threshold value VhF for the surface blur component signal A may be separately provided as a value lower than the threshold value when the above-described protrusion is detected first.
The threshold values VhB and VhF, which are discriminating criteria for disc pass / fail, are given as test values that are NG of discs that are actually inspected at a peripheral speed Vc and subjected to protrusion / surface blur inspection.
By the way, the flowchart in the defect detection process described above is omitted because the above-described programs are sequentially called and executed.

As described above, in the embodiment, the signal B of the protrusion detection component and the signal A of the surface blur component are respectively obtained to determine whether or not the disk is acceptable. However, in the present invention, only the signal A of the surface blur component is determined. It is also possible to obtain only the surface waviness determination.
Further, in this case, the protrusion detection component signal B and the surface blur component signal A are obtained for each track. However, the projection detection component signal B and the surface blur component signal A that are maximum for all tracks are obtained. You may make it obtain. In this case, the hold voltage values of the maximum voltage value hold circuit (peak hold circuit) 17 and the maximum voltage value hold circuit 19 are not reset until the entire disk inspection is completed.
Further, in the embodiment, the signal B of the projection detection component and the signal A of the surface blur component are A / D converted into digital values, and the data processing / control device compares the predetermined reference value to determine whether the disc is acceptable. In the present invention, the comparator / corrugation detection circuit unit 5 is provided with comparators corresponding to the projection detection component signal B and the surface blur component signal A, respectively, without using the data processing / control device. The pass / fail may be determined by providing a comparison determination using analog voltages corresponding to the threshold values VhB and VhF as reference values.
Incidentally, in the embodiment, the example of the glide tester is shown in FIG. 3, but the projection inspection apparatus not provided with the polishing head or the like has the same configuration as FIG.

FIG. 1 is a block diagram centering on a protrusion / disk surface waviness detection circuit portion to which the disk defect inspection method of the present invention capable of detecting disk surface waviness is applied. FIG. 2 is an explanatory diagram of the detected waveform. FIG. 3 is a block diagram of the glide tester of the present invention. FIG. 4 is an explanatory diagram of the protrusion detection head.

Explanation of symbols

1 ... disk to be inspected, 2 ... disk rotation mechanism,
2a ... spindle, 2b ... motor,
3 ... Projection detection head, 3a ... Slider, 3b ... Support spring,
4 ... head carriage, 4a ... arm,
5 ... Projection / surface waviness detection circuit section,
6 ... carriage control circuit, 7 ... peripheral speed control circuit,
8 ... Piezo element, 9 ... Data processing / control device,
10 ... Glide tester, 11 ... Readout amplifier,
12, 13 ... Buffer amplifier,
14 ... Variable gain amplifier, 15 ... High bandpass filter (HBPF),
16: Low-pass bandpass filter (L / BPF),
17: Maximum voltage value hold circuit (peak hold circuit),
18, 20 ... A / D conversion circuit,
19: Maximum voltage value hold circuit,
21 ... Microprocessor (MPU), 22 ... Memory,
22a ... Defect data collection program,
22b... Projection determination program,
22c ... Surface waviness pass / fail judgment program,
22d ... parameter area, 21e ... work area,
23 ... interface, 24 ... CRT display (CRT).

Claims (17)

A disk defect in which a magnetic disk is rotated at a predetermined peripheral speed, a head mounted with a piezoelectric sensor on a slider is levitated with a predetermined flying height, and an electric signal from the piezoelectric sensor is obtained as a detection signal to check pass / fail of the disk In the inspection method,
The detection signal is passed through a low-pass filter to obtain a first signal component corresponding to surface blur due to rotation of the disk, and the maximum value of the level of the first signal component is compared with a first predetermined reference value. A defect inspection method for determining pass / fail of a disc.   The maximum value of the level of the first signal component is obtained in one track or all tracks of the disk, the flying height is 10 nm or less, and the size of the slider is 5 mm square. 2. The defect inspection method according to claim 1, wherein the low-pass filter is a bandpass filter having a frequency in a range of 200 kHz to 400 kHz and a frequency in the range of ± 100 kHz or less than ± 100 kHz. .   The head is a protrusion detection head, and the detection signal is further passed through a high-pass filter to obtain a second signal component for protrusion detection, and the maximum peak value of this signal component is compared with a second predetermined reference value. The defect inspection method according to claim 1, wherein pass / fail is determined.   The piezoelectric sensor is a piezo element, and the low-pass filter is provided as a bandpass filter with a frequency of 500 kHz or less as a low frequency, and the high-pass filter is provided as a bandpass filter with a frequency above 500 kHz as a high frequency. The defect inspection method according to claim 3.   The flying height is 10 nm or less, the size of the slider is 5 mm square or less, and the bandwidth of the high-frequency bandpass filter is ± 150 kHz with a frequency in the range of 1 MHz to 2 MHz as a center frequency. The frequency band of the low-pass bandpass filter is ± 100 kHz with a frequency in the range of 200 kHz to 400 kHz as the center frequency or a frequency range of ± 100 kHz or less. The defect inspection method according to claim 4. A protrusion that rotates a magnetic disk at a predetermined peripheral speed and floats a protrusion detection head mounted with a piezoelectric sensor on a slider with a predetermined flying height, and obtains an electrical signal from the piezoelectric sensor as a detection signal to check the pass / fail of the disk In inspection equipment,
A low-pass filter for obtaining from the detection signal a first signal component corresponding to surface blur due to rotation of the disc;
A projection detecting apparatus comprising: a determination unit that determines whether the disk is acceptable by comparing a maximum value of the level of the first signal component with a first predetermined reference value.   The maximum value of the level of the first signal component is obtained in one track or all tracks of the disk, the flying height is 10 nm or less, and the size of the slider is 5 mm square. The protrusion detection device according to claim 6, wherein the low-pass filter is a bandpass filter having a frequency in the range of 200 kHz to 400 kHz and having a frequency in the range of ± 100 kHz or ± 100 kHz. . And a high-pass filter for obtaining a second signal component for protrusion detection from the detection signal,
7. The protrusion inspection according to claim 6, wherein the determination unit determines pass / fail of the disk separately from determination of pass / fail of the disk by comparing a maximum peak value of the second signal component with a second predetermined reference value. apparatus.   And a first peak hold circuit that holds a maximum value of the amplitude voltage of the first signal component of one or all tracks of the disk, The second peak hold circuit holds the maximum peak value of the entire track or the entire track, and the determination means includes the amplitude voltage obtained from the first peak hold circuit and the first peak value. The projection inspection apparatus according to claim 8, wherein the projection inspection apparatus compares the maximum peak value with the second predetermined reference value by comparing with a predetermined reference value. Furthermore, it has a defect detection circuit, an A / D conversion circuit, and a data processing device, the piezoelectric sensor is a piezo element, and is provided with the low-pass filter with a frequency of 500 kHz or less as a low frequency, and above 500 kHz. The high-pass filter is provided with a frequency of
The defect detection circuit includes the first and second peak hold circuits, the low-pass filter, and the high-pass filter, and the data processing device includes the determination unit, and outputs the low-pass filter. 10. The protrusion detection device according to claim 9, wherein a signal and an output signal of the high-pass filter are received as digital values via the A / D conversion circuit, and pass / fail determination of the disk is performed.   The flying height is 10 nm or less, the size of the slider is 5 mm square or less, and the bandwidth of the high-frequency bandpass filter is ± 150 kHz with a frequency in the range of 1 MHz to 2 MHz as a center frequency. The frequency band of the low-pass bandpass filter is ± 100 kHz with a frequency in the range of 200 kHz to 400 kHz as the center frequency or a frequency range of ± 100 kHz or less. The protrusion detection apparatus according to claim 10. A glide that rotates a magnetic disk at a predetermined peripheral speed and floats a protrusion detection head mounted with a piezoelectric sensor on a slider with a predetermined flying height to obtain an electrical signal from the piezoelectric sensor as a detection signal to check the pass / fail of the disk In the tester,
A low-pass filter for obtaining from the detection signal a first signal component corresponding to surface blur due to rotation of the disc;
A glide tester comprising: determination means for determining pass / fail of the disk by comparing the maximum value of the level of the first signal component with a first predetermined reference value.   The maximum value of the level of the first signal component is obtained in one track or all tracks of the disk, the flying height is 10 nm or less, and the size of the slider is 5 mm square. 13. The glide tester according to claim 12, wherein the low pass filter is a band pass filter having a frequency in the range of 200 kHz to 400 kHz and having a frequency in the range of ± 100 kHz or less than ± 100 kHz. And a high-pass filter for obtaining a second signal component from the detection signal,
13. The glide according to claim 12, wherein the determination means further determines the pass / fail of the disk separately from the determination of the pass / fail of the disk by comparing a maximum peak value of the second signal component with a second predetermined reference value. Tester.   And a first peak hold circuit that holds a maximum value of the amplitude voltage of the first signal component of one or all tracks of the disk, The second peak hold circuit holds the maximum peak value of one track or all of the tracks, and the determination unit compares the amplitude voltage with the first predetermined reference value to determine the maximum peak value. The glide tester according to claim 14, wherein the value is compared with the second predetermined reference value. Furthermore, it has a defect detection circuit, an A / D conversion circuit, and a data processing device, the piezoelectric sensor is a piezo element, and is provided with the low-pass filter with a frequency of 500 kHz or less as a low frequency, and above 500 kHz. The high-pass filter is provided with a frequency of
The defect detection circuit includes the first and second peak hold circuits, the low-pass filter, and the high-pass filter, and the data processing device includes the determination unit, and outputs the low-pass filter. 16. The glide tester according to claim 15, wherein a signal and an output signal of the high-pass filter are received as digital values via the A / D conversion circuit, and pass / fail judgment of the disk is made.   The flying height is 10 nm or less, the size of the slider is 5 mm square or less, and the high-pass filter has a frequency range of ± 150 kHz centered on 1 MHz to 2 MHz, or ± 150 kHz or less. The glide tester according to claim 16, wherein the glide tester is a band-pass filter, and the low-pass filter is a band-pass filter having a frequency in a range of ± 100 kHz or less than ± 100 kHz centering around 200 kHz to 400 kHz.

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