JPH06341825A - Calibration method of protrusion-detection head unit as well as method and apparatus for detection of protrusion using this method - Google Patents

Abstract

PURPOSE:To provide the calibration method, of a protrusion hu, in which the dispersion of an output voltage from a head unit mhu can be calibrated, to provide its inspection method and to provide its apparatus. CONSTITUTION:A protrusion hu whose levitating characteristic is already known is selected and used as a master head unit(mhu), a protrusion hu which is used for a protrusion inspection is used as a protrusion hu to be measured, a disk whose face roughness is prescribed is used as a reference disk, the head of the mhu and the protrusion hu to be measured are loaded sequentially on the face of the reference disk which turns, they are levitated, the peripheral speed (v) of a track on the reference disk is changed, the output voltage em of the unit mhu and the output voltage es of the protrusion hu to be measured are used as functions of the peripheral speed (v), the characteristic of the output voltages is measured, the characteristic is linearly made to approximate on the orthogonal coordinates of the output voltage and the peripheral speed, a straight line em=-av+b and a straight line es=-a'v+b' are found, b/b' and b/ab' are found from them, the gain of an amplifier is corrected with reference to the output signal of the protrusion hu to be measured when the protrusion hu to be measured is used for the protrusion inspection, and the peripheral speed of a rotary disk to be measured is corrected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of calibrating a projection detecting head unit in a magnetic disk projection inspecting apparatus capable of obtaining highly reliable measurement data even if the detection characteristics of the projection detecting head unit vary. And a projection inspection method and a projection inspection apparatus using this calibration method.

[0002]

2. Description of the Related Art A magnetic disk (hereinafter simply referred to as a disk), which is one of the information recording media, is manufactured by coating a magnetic film on the surface of an aluminum or glass disk as a base. The surface of the magnetic film is required to be a smooth flat surface having no protrusions and depressions. Therefore, surface polishing is performed. However, there are still protrusions remaining after polishing. If a predetermined number or more of projections with a height of a predetermined value or more remain, the magnetic head may collide with the projections and be damaged, and an error may occur in the data to be accessed. In order to prevent such a danger, a protrusion inspection device for a magnetic disk performs a protrusion inspection, and as a result, when more than a predetermined number of protrusions with a predetermined height or more remain, the disk is re-polished. Be seen.

A projection detecting head unit (hereinafter simply referred to as a head unit) of a projection inspecting apparatus originally used a piezo element using quartz, but the piezo element has drawbacks in detection sensitivity and saturation characteristics. Since it is difficult to miniaturize, attention is paid to an ultrasonic piezoelectric sensor (hereinafter, referred to as an ultrasonic sensor) which has excellent detection sensitivity and saturation characteristics. A head unit using this ultrasonic sensor was manufactured by the inventor of the present invention. Japanese Patent Application No. 3-334319 "Magnetic disk protrusion detection device", Japanese Patent Application No. 3-334320 "Magnetic disk protrusion detection circuit". Has filed a patent application for an invention relating to this.

FIG. 4 shows an outline of a head unit according to this patent application. Reference numeral 3 denotes a head unit, which is fixed to a slider 31 as a thin film head, a suspension spring 32 that fixes the slider 31 at the tip, a support arm 33 that clamps and supports the rear end of the slider 31, and an appropriate position of the support arm 33. And an ultrasonic sensor 34. The ultrasonic sensor 34 is made of barium titanate or lead zirconate titanate polycrystalline ceramics, and has a natural frequency determined by its thickness.

In the projection inspection, the rotating disk 1
When the head of the head unit 3 is loaded on the track TR, the slider 31 floats by a predetermined flying height δH due to the air flow. And truck TR
When the slider 31 collides with the protrusion existing above, the slider 31 vibrates. This vibration is transmitted to the support arm 33 via the suspension spring 32, and the ultrasonic sensor 34 vibrates at its natural frequency to generate a voltage signal (collision detection signal) and output it.

FIG. 5 shows a block diagram of the projection inspection apparatus. The disk 1 to be inspected is mounted on a spindle 21 of a rotating mechanism 2 and is rotationally driven by a motor (M1) 22. Head units 3A and 3B (the head unit 3B is not provided in the embodiment of the above-mentioned application, but this will be described later) are provided on both the front surface (upper side) and the back surface (lower side) of the disk 1. The support arms 33, 33 are clamped to the carriage mechanism 41 of the carriage unit 4, respectively. Motor (M
2) When the slider 42 is rotated, the slider 31 moves in the radial direction of the disk 1 and stops sequentially for each track TR, or continuously moves to scan the disk 1 in a spiral shape. Normally, since the flying height .delta.H of each slider 31 is made constant for all tracks TR, memory (MEM)
The carriage control program and the peripheral speed control program are stored in 8a, and the MPU 8 executes both programs to operate the carriage control circuit 6 and the peripheral speed control circuit 7. As a result, the motor M2 is driven by the former and the motor M1 is driven by the latter.
Is rotated to sequentially stop or scan in a spiral state, and the circumferential speed of each track TR of the disk 1 is made constant, and the projection inspection is performed.

Collision detection signals output from the ultrasonic sensors 34, 34 when the head units 3A, 3B collide with the projections are input to the projection detection units 5, and their levels are compared with a predetermined threshold value. By doing so, the protrusion is detected. The resulting protrusion detection signal P (see FIG. 6)
(See (e)) is processed by the MPU 8 and is stored and managed as data in the memory (MEM) 8a as a collision position and the number of collisions. Then, these are output as the measurement data of the protrusion by the printer (PRT) 9 after the measurement.

FIG. 6 (a) is a block diagram of the protrusion detecting section 5 described above. The collision detection signal Vf output from the ultrasonic sensor 34 or the piezo element is amplified by the amplifier 51 and unnecessary components are removed by the bandpass filter (BPF) 52, and the signal of the waveform Vfc (see FIG. ) See).
The signal is envelope-detected by the detection circuit 53 and becomes a signal of the waveform VfL (see FIG. (D)), which is then compared with an appropriate slice voltage Sv by the comparator 55 and digitized,
The protrusion detection signal P shown in FIG. Projection detection signal P
Of the buffer memory (BM
The data is stored in a predetermined position of the EM) 57, and the MPU 8 reads the stored data or is transferred to the MPU 8 and processed at a suitable time.

[0009]

The slider 31, the suspension spring 32, and the support arm 33, which compose the head unit 3, have their own vibration frequencies due to their weight and elastic characteristics. Has variations and its vibrations are also uneven. The ultrasonic sensor 34 itself also has a deviation from the original natural frequency due to variation in thickness. Therefore, the flying characteristics with respect to the peripheral speed v of a certain track and the output voltage of the collision detection signal Vf generated by a collision are different for each head unit 3,
The output voltage characteristics vary.

On the other hand, in the projection inspection, the slider 31 and the ultrasonic sensor 34 are often damaged or the characteristics are deteriorated due to the collision with the projection. When the head unit 3 is deteriorated or damaged, the head unit 3 is replaced. However, due to the variation in the output voltage characteristics of the replaced head, unevenness in detection that the same size protrusion detected by the head unit before replacement could not be detected or was sometimes detected, and the protrusion inspection Reliability is reduced. In particular,
In the magnetic disk storage device in the direction of high density storage,
The result of the protrusion inspection is closely related to the reliability of the apparatus, and it is required that even a protrusion having a lower height can be detected with high reliability.

Although an example in which a head unit (head unit 3B) is provided on the back surface side has been described above with respect to the embodiment of the above-mentioned application, when the heads are provided on the front and back sides, the characteristics of these head units are made uniform. That is essential for improving the reliability of the inspection in the front and back simultaneous inspection. If the front and back head units do not have the same characteristics, the front and back heads must be separately inspected by the same head unit, and it is necessary to remove the disks that have been mounted once and turn them over to mount them, thus reducing the inspection efficiency.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to efficiently calibrate variations in the output voltage of the head unit in order to obtain highly reliable inspection data. Another object of the present invention is to provide a method of calibrating a protruding head unit capable of performing the above. Another object of the present invention is to provide a method for calibrating a projection head unit, which is capable of simultaneously performing projection inspection on the front and back by providing head units on the front and back and efficiently obtaining highly reliable inspection data. Still another object of the present invention is to provide a projection inspection method and a projection inspection device which can obtain highly reliable inspection data even when the head unit is replaced by using the above-mentioned projection head unit calibration method. is there.

[0013]

The features of the method for calibrating the projection head unit unit, the projection inspection method, and the projection inspection apparatus according to the present invention for achieving the above object are that the projection head unit is known to have a floating characteristic. The master head unit is selected, and any projection head unit used for projection inspection is used as a measurement head unit. A disk having a predetermined surface roughness is used as a reference disk. The head and the measuring head unit are sequentially loaded and floated, and the peripheral speed v of the track of the reference disk is changed to output the output voltage em of the master head unit.
And the output voltage es of the measuring head unit are measured as respective functions of the peripheral speed v to measure respective output voltage characteristics, and the respective output voltage characteristics are linearly approximated on the orthogonal coordinates of the output voltage-peripheral speed to obtain a straight line em. = -Av + b and the straight line es = -a'v + b ', the straight line em = -av
From + b and straight line es = -a'v + b ', b / b' and a'b
/ Ab 'is obtained, and when the measurement head unit is used for the projection inspection, the gain of the amplifier that amplifies the output signal of the measurement head unit is corrected by b / b' to be the inspection target. The peripheral speed of the track of the rotating disk is corrected by a'b / ab '. However, a and a'are slopes and b and b'are intercepts on the output voltage axis.

[0014]

In order to explain that such correction is effective, first, the variation in the characteristics of the head unit will be described with reference to FIG. FIG. 7A shows the flying height δH of the slider 31 with respect to the circumferential speed v (horizontal axis) of the track TR,
The characteristic curve of the output voltage e (effective value conversion) of the head unit 3 is shown. The position of the dotted line corresponds to the detection position of the maximum protrusion on the disk having a predetermined surface roughness, the flying height at that time is p, and the peripheral speed of the track on which the slider 31 is located is vp.

The output voltage e-peripheral speed v is measured by spiral scanning from the outermost track to the innermost track with the peripheral speed v kept constant with respect to a reference disk having a predetermined surface roughness. The results are obtained by measuring the effective value of the output voltage by using the average value as the voltage value for the peripheral speed, and gradually increasing or decreasing the constant value v of the peripheral speed. The range of the measurement track here does not necessarily have to be the range of the track from the outermost circumference to the innermost circumference, and may be a certain range of tracks in which a protrusion having a certain height is detected.

The flying height .delta.H of the head rises as the peripheral speed v increases, and the peripheral speed corresponding to this is vP at the point p which coincides with the maximum protrusion in the flying height .delta.H.
The protrusion is detected at a peripheral speed vP or lower, and an output voltage e is generated in the head unit. As the peripheral speed v decreases, the output voltage increases almost linearly, reaches a peak, and when the peripheral speed v further decreases, the output voltage becomes a slightly complicated curve. On the other hand, the protrusion is not detected at the peripheral speed vP or higher, but the noise component remains. In the projection inspection,
Normally, a peripheral speed equal to or higher than the peripheral speed vP is adopted, and the flying height of the head of the head unit is also equal to or higher than p. The position of the maximum protrusion indicates the measurement limit value on this characteristic before the output voltage e becomes non-linear when measuring the output voltage characteristic.

In FIG. 7 (b), two arbitrary head units Hq and Hr are taken, and the flying height δ for each peripheral speed v.
The characteristic curves eq and er of H and the output voltage e are shown. The flying heights .delta.Hq and .delta.Hr of the heads of the two head units Hq and Hr and the respective output voltages eq and er are different as shown in the figure because of variations in characteristics. The head unit Hq becomes the maximum protrusion detection position at the point q at the flying height δHq, and the head unit Hr becomes the maximum protrusion detection position at the point r at the flying height δHr. Peripheral speed v for these
q and vr are also different.

Therefore, in order to accurately inspect a protrusion having a predetermined height, it is necessary to calibrate the variation of the output voltage e of each head unit as described above by providing a constant reference value. is there. As a method of this calibration, in the present invention, attention is paid to the characteristics of the substantially linear portion of the characteristic curves eq and er of the output voltage e that move from the peaks to the valleys. If this part is overlapped, the positions of the detection points q and r of the maximum protrusions of the characteristic curves eq and er will be almost the same position or in the vicinity thereof.
Each head unit can be used as a head unit having the same characteristics. Therefore, in advance, a reference disk having a reference surface roughness is attached to the protrusion inspection device, and the reference disk is rotated to rotate the peripheral speed of a track on the reference disk of a master head unit and a measurement head unit whose flying characteristics are known. The characteristics of v vs. output voltage e (output voltage characteristics) are measured.

Next, the linear slope portion of the output voltage characteristics of both head units is linearly approximated on the ev orthogonal coordinates of the output voltage e-the peripheral speed v. The equations of the respective straight lines are obtained as em = -av + b and es = -a'v + b, and the gain correction value KG = b /
b'and the peripheral speed correction value Ks = a'b / ab 'are calculated. With these correction values, one approximate straight line is corrected so as to match the other approximate straight line. By doing so, the characteristics of the substantially linear portions that move from the peaks to the valleys of the characteristic curves of the respective output voltages coincide with each other, and the position of the detection point of the maximum protrusion also comes to the substantially same position.

By correcting the characteristics of the head unit by such a correction and using the same output voltage characteristics for the projection inspection, the reliability of the projection inspection or the measurement efficiency can be improved. For example, in the projection inspection apparatus, the respective correction values KG and KS measured for a certain measurement head unit are set in a gain correction program and a peripheral speed correction control program which are created in advance, and these programs are executed. When a protrusion is inspected by the lever measuring head unit, the gain of the amplifier that amplifies the output voltage of the head unit is corrected by the correction value KG, and the peripheral speed of the track on the inspection disk is corrected by the correction value KS.

As a result, the output voltage characteristic es of the measuring head unit is calibrated to the output voltage characteristic em of the master head unit, and the protrusion inspection can be performed with the output voltage characteristic em of the master head unit. Accordingly, it is possible to easily select two head units having the same peripheral speed during the protrusion inspection, and it is possible to provide such head units on the front and back sides and perform the protrusion inspection simultaneously on the front and back sides.
Further, even if the head unit is replaced with another head unit, the characteristics can be made uniform, so that highly reliable projection inspection can be performed.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an output voltage characteristic centered on a linear inclined portion S of a master head unit Hm and a certain measuring head unit HS which moves from a peak to a valley.
The horizontal axis is the peripheral speed v, and the vertical axis is the head unit 3
Output voltage e of the respective head units, and the output voltage characteristics of both head units are em and es, respectively. The portions indicated by alternate long and short dash lines are the approximate straight lines Lm and LS. Approximate straight line Lm
(Straight line equation straight line em = -av + b), LS (Straight line equation es = -a'v + b ') is data of characteristics measured by changing the output voltage of the master head unit Hm and the measuring head unit HS on the circumferential side v. Can be obtained from the measurement data of the portion of the measuring head unit HS that moves from the peak to the valley. At this time, a and a'are the inclinations of both straight lines. b and b ′ are intersections of the output voltage axes (vertical axis) of both straight lines, that is, intercepts of the vertical axis, and correspond to the output voltage e as a theoretical value when the circumferential sides of both head units are zero.

From these, b / b 'and a'b / a
b ′ can be calculated, and this b / b ′ is the ratio of the intercepts b and b ′ on the vertical axis. Since this is the ratio of the sensitivities of both head units Hm and HS, the gains of the amplifiers for amplifying the signals of the head units for both head units can be matched. Similarly, the intersections b / a and b '/ a' of the two approximation straight lines Lm and LS with the horizontal axis (peripheral velocity axis) are intercepts on the horizontal axis, and their ratio a'b.
/ Ab 'is the ratio of the peripheral speeds vm and vs to both head units Hm and HS. Therefore, by changing the peripheral speed on the measurement head unit side, the point b '/ a' can be changed to b
The points of / a can be matched.

Here, b / b 'is defined as a gain correction coefficient KG, so that when the head unit HS is used for the gain Gs of the amplifier 51 set for the master head unit Hm at the time of projection inspection, b'is used. Gain correction (calibration) is performed so as to match with b. a'b / a
b'is a peripheral velocity correction coefficient Ks, which allows b '/ a' when the head unit HS is used with respect to the peripheral velocity vs of the track of the inspection disk set for the master head unit Hm during the protrusion inspection. The peripheral speed is corrected (calibrated) so that is equal to b / a. As a result, the output voltage characteristic of the measuring head unit can be almost matched with the characteristic of the master head unit. Here, the amplifier 51 is a variable gain amplifier whose gain is controlled by the control signal of the MPU 8.

The above is the principle. As an actual method of calibrating the head unit, first, a head unit having known flying characteristics and having the best characteristics is selected and used as the master head unit Hm. An arbitrary head unit used for the projection inspection is referred to as a measurement head unit HS. Then, a reference disk having a predetermined reference surface roughness is separately manufactured and prepared. This reference disk is mounted on the spindle 21 shown in FIG. 5, and the gain of the amplifier 51 is set to a predetermined set value GO by a device shown in FIG. 2 which can measure the output voltage (effective value) of the head unit. Then, the peripheral speed v is changed and the output voltage characteristics em and es of both head units Hm and HS are measured. As described above, the measurement method is performed by spiral scanning with the peripheral speed kept constant to obtain the average value of the effective value of the output voltage, and the constant value is increased or decreased to be changed to the next spiral scanning. Then, the average value of the effective value of the output voltage is obtained, and such measurement is sequentially repeated to obtain the output voltage according to the change of the peripheral speed.

From the output voltage characteristics em and es of both head units Hm and HS thus obtained, a straight line is obtained by linearly approximating this portion according to the measured data of the portion from the peak to the valley. From the straight lines em = -av + b and es = -a'v + b 'thus obtained, the gain correction coefficient KG = b /
b'and the peripheral speed correction coefficient Ks = a'b / ab 'are obtained, and these are given to the measuring head unit as the correction coefficient of the measuring head unit for management. Such correction coefficient management is performed for each measurement head unit. In the measurement of the master head unit, once em = -av + b is obtained, the subsequent measurement is unnecessary unless the reference disk is changed.

If each head unit is managed together with the correction coefficient in this way, when a protrusion is inspected by a certain measuring head unit, the current gain GA of the amplifier set at the time of the protrusion inspection by the measuring head unit A and When the other measuring head unit B is replaced with the peripheral speed vA, the gain correction coefficient KGA and the peripheral speed correction coefficient KSA of the previous measuring head unit A are known. If the coefficient KGB and the peripheral speed correction coefficient KSB are known, the gain GB to be set by the amplifier for amplifying the output voltage of the head unit is GB = GA × KGB
You can ask for it with / KGA. Further, the peripheral speed vB to be set for the track can be obtained by vB = vA × KSB / KSA.

In this way, if the projection inspection is performed in the corrected state by the gain correction and the peripheral speed correction,
The output voltage characteristic of the head unit HS in FIG. 1 used for the inspection is calibrated to be substantially equal to the output voltage characteristic of the head unit Hm, and the output voltage es thereof corresponds to the approximate straight line LS and is represented by a dashed line. becomes es'. If two head units having substantially the same peripheral speed correction value are provided on the front and back sides, the gain values can be set independently for each amplifier, so that simultaneous front and back inspection can be performed. Also,
The reference disk having the reference surface roughness may be separately manufactured to use the reference surface roughness as a reference, but a general disk may be used as a reference.

FIG. 2 shows a projection inspection apparatus to which the calibration method according to the present invention is applied. The configuration is such that a measurement circuit for measuring the output voltage characteristic of the head unit is added to the projection inspection apparatus of FIG. Unit output voltage (effective value)
The measurement data of is stored in the memory and each correction coefficient is calculated,
This is designed to be managed in correspondence with the measuring head unit. Further, the memory 8a of FIG. 5 is provided with a gain correction program 80 and a peripheral speed correction control program 81, which are set at the time of setting the gain of the amplifier 51 for amplifying the signal from the head unit and the projection inspection. The peripheral speed correction of each track is automatically performed. The peripheral speed correction control program 81 is obtained by adding the peripheral speed correction function to the peripheral speed control program previously described in the prior art. Further, although the carriage control program described in the prior art is stored in the memory 8a,
This is not shown.

In the projection inspection apparatus of FIG. 2, the disk 1, the rotation mechanism 2 for rotating the disk 1 and the carriage section 4 shown in FIG. 5 are the same as those in FIG. Omitted. In addition, programs 80, 8
1 is called a program because it uses the MPU, but as described above, the actual correction is the gain value GS for the master head unit at the time of the projection inspection stored in the memory 8a in advance. Or peripheral speed vs
Alternatively, the present setting value is only multiplied by the correction value or is divided, and is not a special processing program. As for the correction, a simple numerical calculation process is sufficient, so the details are omitted. In addition, as the processing of these programs, a control value according to the calculation result is sent from the MPU 8 to the amplifier 51 and the peripheral speed control circuit 7, but this is merely a general output processing.

Reference numeral 54 is an output voltage measuring circuit, which comprises an effective value detecting circuit 54a, an A / D conversion circuit (A / D) 54b and a memory 54c. The output of the measurement head unit 34 is amplified by the amplifier 51 and applied to the effective value detection circuit 54a via the BPF 52. The gain of the amplifier 51 at this time is set by the control of the MPU 8 so as to be a predetermined gain setting value G0 for measurement. The effective value detection circuit 54a is composed of a rectifying circuit for rectifying the collision detection signal and an average value circuit for taking an average value of the output of this circuit, and the effective value is obtained by the average value circuit. Here, the detected effective value (voltage value) is added to the A / D 54b and A / D converted. The memory 54c receives the A / D conversion value and sequentially stores each conversion value at each address. A /
The D54b performs A / D conversion according to the control signal from the MPU 8 and sends the result to the memory 54c. The memory 54c updates the address according to the control signal from the MPU 8 and stores the received data.

The MPU 8 is an ev characteristic measuring program 8
2 is given to the speed control circuit 7 so that the peripheral speed of each track is constant, and spiral scanning is performed over the entire surface of the disk (here, the range from the outermost circumference to the innermost circumference). At the same time, control signals are sent to the A / D 54b and the memory 54c. As a result, the measurement data in which the peripheral speed v is constant over the entire surface of the disk is stored in the memory 54c, and the MPU 8
The measured data is read from the memory 54c, the average value thereof is calculated, and the average value is stored in the memory 8a according to the peripheral speed value given to the peripheral speed control circuit 7. Next, the spiral speed is increased (or decreased), the spiral scan is performed, the measured data is read from the memory 54c, the average value thereof is calculated, and this is given to the peripheral speed control circuit 7. It is stored in the memory 8a according to the increased or decreased peripheral speed value. As a result of repeating such measurement, the peripheral speed is changed, and the head unit output voltage characteristic e is stored in the memory 8 as a function of the peripheral speed v.
Remember in a. In the above case, the memory 54c is not always necessary if the converted value of the A / D 54b can be received by the MPU 8 in real time.

As for the overall operation of the projection detecting apparatus, the master head unit Hm is mounted on the carriage unit 4, the MPU 8 executes the ev characteristic measuring program 82, and the gain of the amplifier 51 is set by the control of the MPU 8. Value G
The master head unit Hm is set to O and a spiral scan with a constant peripheral speed is performed under the gain GO and the spiral speed is changed from the outer track to the inner track and vice versa. The effective value of the output voltage is sampled as a function of the peripheral speed v. Next, the measuring head unit HS is mounted on the carriage unit 4, and similarly, by the control of the MPU 8, the full spiral scan is performed under the gain GO as the effective value of the output voltage of the head unit Hs as a function of the peripheral speed v. Collected. As a result, the measurement data em and es are stored in the memory 8a.

Next, the MPU 8 executes the similar straight line calculation processing program 83 to read out the measured data in the range of peripheral speed lower than the peripheral speed vp corresponding to the maximum protrusion from the measured data em and es stored in the memory 8a. Then, this is expanded into data of rectangular coordinates of output voltage e-peripheral speed v, and approximated straight lines Lm and Ls are calculated from the data of a plurality of points by calculation processing (straight line calculation by general coordinate values). As a result, the linear equations for these em = -av + b, es =
-A'v + b 'are obtained and stored in the memory 8a.

The gain correction coefficient KG = b / b 'and the peripheral speed correction coefficient KS = a'b / ab' are obtained from the data of each straight line thus stored according to the above-mentioned calibration method, and these are obtained from the measuring head unit. It is stored in the correction value table 84 of the memory 8a under the identification number given to the measuring head unit which is previously input as the correction coefficient, the same measurement is performed for the next measuring head unit, and the same measurement is carried out with the identification number. The resulting correction value is stored in the table 84.
Gain correction coefficient KG for multiple measurement head units
And the peripheral velocity correction coefficient KS are obtained, they are stored in, for example, a floppy disk.

When a certain measuring head unit is used, its gain correction coefficient KG and peripheral speed correction coefficient KS are read from the floppy disk, and the gain GB of the amplifier 51 and the track of the amplifier 51 to be set in the projection inspection apparatus are set. The peripheral speed vB is calculated by the division and multiplication as described above in the relationship between the gain GA of the measuring head unit used before and the peripheral speed vA, and the gain correction coefficient KG and the peripheral speed correction coefficient KS. Is set. Further, in this case, the gain and the peripheral speed to be corrected correspond to the reference gain value GS and the reference peripheral speed vs that are assigned to the master head unit as the protrusion inspection each time the measuring head unit is mounted. It may be calculated by multiplying the correction coefficient KG by the peripheral speed correction coefficient KS.

By the way, when the head unit 34 is a piezo sensor, the band of the BPF 52 is 100 kHz to 100 kHz.
It is about 300 kHz, and in the case of an ultrasonic sensor, 3
A frequency of about 00 kHz to 600 kHz is used. Further, since there is a variation in the natural frequency of each measuring head unit HS, the bandpass filter (B
The pass band of the PF) 52 may be switched, and this switching may be performed by the control signal of the MPU 8 according to an instruction from the key board.

The projection inspection apparatus shown in FIG. 2 can originally perform the projection inspection by calibrating the measurement head unit each time the measurement head unit is replaced. Therefore, the processing will be described with reference to the flowchart of FIG. First, in the preparation process of (a), the output voltage characteristic em = -av + b of the master head unit serving as a reference is sampled by measurement and stored in the memory 8a. That is, a reference disk having a predetermined surface roughness is mounted on the spindle 21 of the inspection device, and the master head unit Hm of known flying height is clamped on the carriage mechanism 41 (step 100). Then, the gain of the amplifier 51 is set to G0 and the disk 1 is rotated (step 101). The head control unit 34 is moved by the carriage control program to be loaded on the reference disk, spiral scanning is performed at a certain peripheral speed value, the peripheral speed v is changed to perform spiral scanning, and this is repeated to output voltage for each peripheral speed. Measure em. In this case BPF5
When it is necessary to select the appropriate band 2, the MPU 8 is instructed by the keyboard to select the band of the BPF 52, and then the output voltage characteristic em is measured and stored in the memory 8a (step 102). An approximate straight line Lm is calculated from the measured data, and the linear equation em = -av + b is stored in the memory 8a (step 103).

Next, in the case of replacing the measuring head unit in the inspection of (b), the master head unit H
The reference disk used for measuring the characteristic of m is mounted on the spindle 21 of the inspection device, and the measuring head unit HS exchanged with the carriage mechanism 41 is clamped (step 1).
04). The gain of the amplifier 51 is set to G0 and the disk 1 is rotated (step 105). The head unit 34 is moved by the carriage control program to load it on the reference disk, and the peripheral speed v is changed to measure the output voltage es for each peripheral speed. In this case B
When it is necessary to select an appropriate band of PF52,
After the MPU 8 is instructed and selected by the keyboard, the output voltage characteristic es is measured and stored in the memory 8a (step 106). An approximate straight line LS is calculated from the measured data, and the linear equation es = -a'v + b 'is obtained (step 107).

Next, the gain correction coefficient KG = b / b 'is calculated based on the linear equation es = -a'v + b' and the linear equation em = -av + b obtained in step 103 and set in the gain correction program 80. Similarly, the peripheral speed correction coefficient KS = a'b / ab 'is calculated and set in the peripheral speed correction control program 81 (step 108). When the inspection is started (step 109), the MPU 8 executes the gain correction program 80 and the master head unit Hm multiplies the reference gain GS assigned when the protrusion inspection is performed by the gain correction coefficient KG, The value obtained as a result is set in the amplifier 51 as a gain setting value (step 110). Further, the peripheral speed correction control program 81 is executed by the MPU 8 and the peripheral speed correction coefficient Ks is multiplied by the reference peripheral speed vs assigned when the master head unit Hm inspects the protrusion, and the result is obtained. A control value is set in the peripheral speed control circuit 7 according to the track on which the head unit is positioned so that the value becomes the peripheral speed value of each track (step 111). Then, the projection of the inspection disk is inspected by the measuring head unit HS (step 112).

By this correction, the detection voltage es of the measuring head unit is substantially calibrated to the characteristic of the output voltage em of the master head unit, and the projection inspection is performed. In this way, by incorporating this calibration method into the projection inspection apparatus, the projection inspection apparatus can perform the projection inspection with the measurement head unit that substantially corresponds to the characteristics of the master head unit, whichever measurement head unit is used. Therefore, even if head units with almost the same peripheral speed are selected, these head units are provided on the front and back sides, and the correction gains corresponding to the respective head units are set and the inspection is performed simultaneously on the front and back sides, Highly reliable.

In this case, the peripheral speed correction coefficient KS is 2
When the value is twice or more, it is a head unit having statistically extreme characteristics, so it is treated as a defective head unit without calibration. The same applies to a head unit whose gain correction is 10 times or more. Further, if there is no reference disk when the master head unit is measured in step 104, another reference disk may be adopted. In that case, the steps of the preparatory step before the inspection in steps 100 to 103 may be performed again.

As described above, in the embodiment, in the measurement of the effective value of the output voltage of the head unit, the entire peripheral surface is spirally scanned with the peripheral speed kept constant. May span multiple tracks. Also, there are many protrusions on one track,
When the height of the protrusion is statistically high or low, the measurement of the effective value may be completed by scanning one track. Further, instead of the spiral scanning, it is also possible to stop corresponding to each track, scan a plurality of tracks, and employ the average value of the effective values as the output voltage. Further, in the embodiment, the case where the head unit is provided on the front and back sides is also described, but in the present invention, the head unit may be provided on either one of the front and back sides, and is not necessarily provided on the front and back sides.

[0044]

As is apparent from the above description, in the present invention, the linear slope portion in the output voltage characteristics of the master head unit and the measurement head unit is defined as the orthogonal coordinate of the output voltage e-the peripheral speed v. The above equation is approximated to a straight line and the equation of each straight line is em = -av + b, es =-
a'v + b, and the gain correction value KG = b / b 'and the peripheral speed correction value KS = a'b / a are obtained from both approximate linear equations.
Since b'is calculated and one of the approximate straight lines is corrected by these correction values so as to match the other approximate straight line, variations in the characteristics of the head units can be absorbed, and the output voltage characteristics of the respective head units are made uniform. It can be used for projection inspection.

As a result, the reliability of the projection inspection or the measurement efficiency can be improved. Further, it is possible to easily select two head units whose peripheral speeds are uniform during the projection inspection, and it is possible to provide such head units on the front and back sides and perform the projection inspection on the front and back sides at the same time. further,
Even if the head unit is replaced with another head unit, the characteristics can be made uniform, so that reliable projection inspection can be performed.

[Brief description of drawings]

FIG. 1 is a characteristic diagram of an output voltage with respect to a peripheral speed of a head unit for explaining the principle of a head unit calibration method according to the present invention.

FIG. 2 is a waveform diagram of a block diagram of an embodiment of a projection inspection apparatus to which the head unit calibration method according to the present invention is applied.

3A and 3B are explanatory views of a protrusion inspection procedure for FIG. 2, wherein FIG. 3A is a flowchart of approximate straight line sampling for a master head unit, and FIG. 3B is a flowchart of inspection.

FIG. 4 is a schematic diagram for explaining the invention of USSN 7,977,634.

5 is a block diagram in the case where projection detection head units are provided on the front and back sides in the projection inspection apparatus to which the invention of FIG. 4 is applied.

FIG. 6 is a block diagram of a conventional protrusion detection unit.

FIG. 7 is a characteristic diagram of a head unit,
(a) is a characteristic diagram of flying height and output voltage with respect to peripheral speed, (b)
FIG. 4 is a characteristic diagram showing variations in flying height and output voltage with respect to peripheral speeds for arbitrary two head units.

[Explanation of symbols]

1 ... Disk, 2 ... Rotation mechanism, 3, 3A, 3B ... Head unit, 4 ... Protrusion detection section, 6 ... Carriage control circuit,
7 ... Peripheral speed control circuit, 8 ... MPU, 8a ... Memory (ME
M), 9 ... Printer, 22 ... Motor (M1), 31 ... Slider, 32 ... Suspension spring, 33 ... Support arm, 34 ... Ultrasonic piezoelectric sensor, 41 ... Carriage mechanism,
42 ... Motor (M2), 54 ... Output voltage measuring circuit, 54
a ... Effective value detection circuit, 54b ... A / D conversion circuit, 54c
... Memory (MEM), 80 ... Gain correction program, 8
1 ... peripheral speed correction program, 82 ... ev characteristic measurement program, 83 ... approximate straight line calculation program, 84 ... correction table.

Claims (5)

[Claims] 1. A protrusion detection head unit whose flying characteristics are known is selected as a master head unit, and a disk having a predetermined surface roughness is used as a reference disk. The head is loaded and levitated, the peripheral speed v of the track of the reference disk is changed, the output voltage em of the master head unit is measured as a function of the peripheral speed v, and its output voltage characteristic is measured. Output voltage-peripheral speed is approximated to a straight line on a rectangular coordinate and a straight line em = -av
+ B (where a is the slope, and b is the intercept of the output voltage axis), and the head of this measurement head unit is used as the measurement head unit for any projection detection head unit used for the projection inspection. Then, the peripheral speed v of the track of the reference disk is changed and the output voltage es of the measuring head unit is measured as a function of the peripheral speed v to measure its output voltage characteristic. A straight line is approximated to a straight line es =-on the rectangular coordinates.
a'v + b '(where a'is the slope and b'is the intercept of the output voltage axis), and the straight line em = -av + b and the straight line es = -a'v + b'
From b / b 'and a'b / ab' are obtained, the gain for amplifying the output signal of the measurement head unit when the measurement head unit is used for the projection inspection is set to the b / B 'is corrected, and the peripheral speed of the track of the rotating disk to be inspected is a'b / a
A method for calibrating a protrusion detection head unit, characterized in that it is corrected by b '. 2. The measurement of the output voltage characteristic with respect to the change of the peripheral speed is performed by scanning at a constant peripheral speed in a predetermined track range to obtain an average value of the output voltage to obtain the output voltage with respect to the constant peripheral speed. The method for calibrating the protrusion detection head unit according to claim 1, wherein the constant peripheral speed is sequentially changed. 3. The predetermined track range is from the innermost track to the outermost track, the scan is a spiral scan, and the head unit loading surface of the reference disk is either a front surface or a back surface. The output voltage of the master head unit and the measuring head unit is input to an amplifier and the effective value of the amplified output signal is measured, and the gain of the amplifier is substantially the same in each measurement. The linear approximation is performed by the value of the portion of the characteristic of the output voltage characteristic that shifts from the peak to the valley, and the gain and the peripheral speed are corrected by the other than the one before the measurement head unit is used. 4. The method for calibrating the protrusion detection head unit according to claim 3, wherein the method is performed by multiplying or dividing the value of the head unit of 1. 4. A disc having a predetermined surface roughness is used as a master disc by selecting a protrusion head unit whose flying characteristics are known as a master head unit, and using an arbitrary protrusion head unit used for protrusion inspection as a measurement head unit. The head of the master head unit and the measuring head unit are sequentially loaded on the surface of the rotating reference disk to float and the peripheral speed v of the track of the reference disk is changed to output the output voltage of the master head unit. em and the output voltage es of the measuring head unit are each measured as a function of the peripheral speed v, and each output voltage characteristic is measured, and each output voltage characteristic is linearly approximated on the orthogonal coordinate of the output voltage-peripheral speed. em =
-Av + b and straight line es = -a'v + b 'are obtained, b / b' and a'b / ab 'are obtained from the straight line em = -av + b and straight line es = -a'v + b', and the measuring head is obtained. When the unit is used for the protrusion inspection, the gain of the amplifier for amplifying the output signal of the measuring head unit is corrected by b / b ', and the peripheral speed of the track of the rotating disk to be inspected is a'. A projection inspection device that corrects by b / ab '. However, a and a'are slopes and b and b'are intercepts on the output voltage axis. 5. An amplifier for amplifying the output of a projection detecting head unit, a detection circuit for receiving a signal from this amplifier and detecting a collision with the projection based on this signal, and a spindle on which an inspection disk is mounted and which rotates the disk. And a controller for controlling the rotation of the spindle, which detects the protrusion by loading the head of the protrusion detection head unit onto the surface of the inspection disk and causing the head to float to detect the protrusion. A gain correction coefficient obtained corresponding to, and a peripheral speed correction coefficient obtained corresponding to the protrusion detection head unit is provided with a control circuit, the gain of the amplifier is corrected by the gain correction coefficient,
The number of revolutions of the spindle is corrected by the peripheral speed correction coefficient to detect a protrusion, and the gain correction coefficient has a straight line em = -av + b and a straight line es = on the output voltage-peripheral speed orthogonal coordinates. -A'v +
b'to b / b '(where em and es are the output voltage of the protrusion detection head unit, the v is the peripheral speed, and a and a'are
Is a slope, b and b'are intercepts of the output voltage axis), and the peripheral speed correction coefficient is a'b / ab '. The straight line em = -av + b has a flying characteristic of A known protrusion detection head unit is selected as a master head unit, a disk having a predetermined surface roughness is used as a reference disk, and the head of the master head unit is loaded on the surface of the rotating reference disk to float.
The output voltage characteristic of the output voltage em of the master head unit is measured as a function of the peripheral speed v by changing the peripheral speed v of the track of the reference disk, and the output voltage characteristic is linearly approximated on the orthogonal coordinates. The straight line es = −a′v + b ′ is obtained by loading the head of the measuring head unit on the surface of the reference disk and using the protrusion detecting head unit as the measuring head unit to float the reference disk. The peripheral voltage v of the track is changed, the output voltage es of the measuring head unit is measured as a function of the peripheral speed v, the output voltage characteristic is measured, and the output voltage characteristic is linearly approximated on the orthogonal coordinates. Protrusion detection device that is one.