JPS6287804A - Apparatus for measuring floating quantity of magnetic head - Google Patents

Abstract

PURPOSE:To make it possible to measure the floating quantity of a magnetic head, by forming either one of a plurality of information recording medii and the magnetic head from a transparent body and directing a plurality of lights between both of them to measure a generated interference fringe. CONSTITUTION:Magnetic head sliders 6-1-6-4 are inserted between transparent glass disks 5-1, 5-2 and a plurality of lights are successively directed from a light source part 121 to generate interference fringes. These interference fringes are converted to electric signals by photoelectric converter parts (cameras) 131-1-131-4 and an image is frozen on a frame memory 17 to perform the positional detection of slider rails. These positional informations are obtained and brightness data of all of cameras and all of wavelengths are transmitted to an access memory 20. Next, the operational processing of image data based on brightness data is performed to calculate a peak position and an edge position. Thereafter, degree discrimination is performed to the surfaces of the slider rails to calculate floating quantity at the peak position. All of the floating quantities are subjected to least square approximation by a n-degree formula to calculated a floating quantity curve and the quantity at the edge position is measured as the floating quantity of a magnetic head part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a magnetic head flying height measuring device, and is applicable to an information recording device 1 such as a magnetic disk device or a VTR.

The present invention relates to a magnetic head flying height measuring device suitable for automatically measuring the flying height of a magnetic head slider in a floppy device or the like, particularly at high speed and with high precision.

[Background of the invention]

Conventionally, regarding a head flying height measurement device for a rotating disk device, IEEE Transactions
n Magnetics, Vol.
, λfAG-12゜&6, November 1
As seen in the report described in No. 976, P., and No. 725, this is a visual measurement, and the flying height is determined from the interference color.

For this reason, it was unsuitable for high-speed measurements and had insufficient measurement accuracy.

Next, an example of a prior art technique in which the same principle is applied to a magnetic rad slider will be described.

In general, a magnetic disk slider of a magnetic disk device floats while maintaining a spacing, that is, a gap on the order of submicrons, by the action of a hydrodynamic wedge force against the surface of a magnetic disk rotating at high speed. This gap is called the flying height.

It is an essential condition for ensuring the reliability of a magnetic disk device to thoroughly inspect and confirm that the magnetic head unit maintains this flying height stably.

FIG. 10 is a schematic configuration diagram of a conventional flying height measuring device, and shows the principle of a conventional measuring method using optical interferometry.

With reference to FIG. 10, a case will be described in which a minute gap floating by air force between a glass disk simulating a magnetic disk of a magnetic disk device and a slider is measured.

1 is a white light source including a broadband wavelength; 2 is a white light source 1
3 is the camera, 4 is the filter 2
And the no-f mirror 5' installed opposite to camera 3 is:
This is a glass disk into which the light flux from the half mirror 4 is incident. 6' is a slider installed facing the glass disk 5', and 5'a and 6'b indicate edge portions.

The filter 2 converts the light from the white light source 1 into a monochromatic luminous flux, and a part of this luminous flux is incident on the glass disk 5' through the half mirror 4, and a part of this is incident on the back surface of the glass disc 5'. The remaining part is reflected by the slider 6'. Interference fringes are generated by the light reflected from the front surface of the slider 6' and the light reflected from the back surface of the glass disk 5', and these interference fringes are observed by the camera 3 through the half mirror 4. ITV camera is used for camera 3, and TV
The flying height is calculated visually from the interference image on the monitor.

In the past, the flying height was determined by reading the position of the interference fringes on the slider 6' surface by photographic recording or visual inspection, but this method (1) is time-consuming and labor-intensive; (2)
There were problems such as the inability to directly determine the order of interference fringes and (3) poor measurement accuracy.

In addition to the above method, there is a method in which white light is irradiated and interference fringe images of the reflected light are observed with a color camera, and order discrimination and flying height are determined simultaneously based on the interference color. This too,
There are limits to measurement accuracy, and measurement takes time.

With the recent increase in the capacity of magnetic disk devices.

As recording density improves, the spacing between the magnetic disk slider and the information recording medium such as a magnetic disk is required to be smaller and more stable.

Therefore, in order to ensure the reliability of information recording devices such as magnetic disk drives, it has become important to improve the accuracy and precision of spacing measurements, shorten measurement time, and automate them.

[Purpose of the invention]

The present invention has been made in view of the actual state of the prior art, and is capable of automatically measuring the spacing between a rotating information recording medium and a magnetic head, that is, the flying height of a magnetic head with high precision and high speed. Its purpose is to provide measuring equipment.

[Summary of the invention]

The structure of the magnetic head flying height measuring device according to the present invention is as follows: Either the information recording medium or the magnetic head is a transparent body, and the information recording medium has a plurality of measurement units.

A magnetic head flying height measurement device that measures the spacing between magnetic heads from interference fringes caused by optical interference, which includes a light source section that has multiple wavelengths and is equipped with a means for smoothing unevenness in light amount, and a white light and a plurality of monochromatic lights. An optical system consisting of a wavelength variable means that changes the wavelength of light, a lens system that simultaneously generates interference fringes on multiple measurement units and forms an image of the interference fringes, and multiple photoelectric conversion units that convert the interference fringes into electrical signals. With the system.

a switching circuit that sequentially switches output signals from the plurality of photoelectric conversion units;

First, the plurality of measurement sections are irradiated with white light by the optical system, the images of the measurement sections output by the plurality of photoelectric conversion sections are input, and the position of the measurement sections is detected by detecting the outline of the image. Then, using the position information that is the position detection result, while changing the wavelength by the wavelength variable means, input brightness data of interference fringes generated at specific positions of the plurality of measurement units at each wavelength in sequence. A frame memory having a preprocessing circuit that stores image data based on brightness data from the plurality of photoelectric conversion units at each of the wavelengths, and image data based on the brightness data of these interference fringes. detecting the edge position of the magnetic head in the measuring section; detecting the peak positions of bright and dark parts of the brightness data of the interference fringes; correcting the peak position by removing noise at the peak position; correcting optical distortion of the optical system; and an arithmetic control means for determining the order of the interference fringes to obtain a magnetic head flying height line and calculating the flying height of the magnetic head at a specific position from the curve; At the command, the information recording medium.

It consists of a magnetic head and a control means for controlling the optical system.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 9.

First, FIG. 1 is a block diagram of a magnetic head flying height measuring device according to an embodiment of the present invention, FIG. 2 is a detailed diagram showing the optical system of FIG. 1, and (a) is a block diagram; 1)) is an enlarged view of the field lens, and (C) is an enlarged front view of the filter table.

In FIG. 1, 5-1.5-2 is a glass disk modeled by using a transparent magnetic disk as a recording medium, and 6-1. 6-2. 6-3.6-4 indicates a plurality of magnetic RAD sliders to be measured. That is, in this embodiment, four sets of magnetic RAD sliders 6-1. 6-2
．． 6-3. 6-4 with two glass disks 5-1.
Insert it between 5-2.

ff1 from both sides of glass disk 5-1.5-2 at the same time
11 will be explained below.

It should be noted in advance that the number of magnetic disk sliders, the configuration of the glass disk, etc. are not limited to the present embodiment.

The glass disk 5-1.5-2 is supported by a spindle 7 and rotated by a motor 8. A rotation detector 9 is attached to the motor 8 coaxially with the motor 8 so as to be able to measure the number of rotations of the glass disk 5-1, 5-2.

Magnetic Herad Slider 6-1. 6-2. 6-3゜6-
4 is attached to the guide arm 10, and this guide arm 1
0 is directly connected to the load/unload mechanism 11, and is loaded between the glass disks 5-1 and 5-2 in response to a measurement command and positioned at a measurement point.

The load/unload mechanism 11 is controlled by a mechanical controller 13. After the measurement is completed, the load/unload mechanism 11 moves the magnetic hesod sliders 6-1, 6-2, 6-3, 6-
Take out 4 (unloading).

Two left and right optical systems 12-1.12-2 are arranged facing the glass disk 5-1.5-2, and a plurality of (in this example, four) optical systems 12-1.
glass disk related to the measurement part of

Interference fringes are simultaneously generated between the magnetic herad sliders, and photoelectric conversion units 131-1, 131-2, 131-3° 131
-4 to detect.

Next, this optical system will be explained in more detail with reference to FIG.

In Figure 2, the photoelectric conversion unit is 131-1 out of the four optical systems.
The optical system No. 4 is shown as a representative example, and the other sets have similar configurations.

As shown in FIG. 2(a), the light source section 121 emits a luminous flux of 120v% from a xenon lamp with multiple wavelengths and high brightness through a field lens through a cold mirror 120-1 as elliptically reflected light 120-0. The light is focused on 120-2.

Note that the cold mirror 120-i can provide sufficiently high reflectance to visible light and suppress reflectance to unnecessary heat rays.

The field lens 120-2 is only for removing unevenness in light amount, and functions as a means for smoothing unevenness in light amount. As shown in FIG. 2(b)K, this field lens 120-2 has a sand coating process of about 400 mm on the negative surface (arrow side), and an outer surface with a radius of 28 mm on the other surface. Diameter 14, length 1
It has a cylindrical shape and is made of 2m+ BK-7 material (heat-resistant material for lenses).

Note that the degree of sanding is not limited to ≠400, and the shape (R1 outer diameter, length dimension) is not limited to the above values.

The output light beam of the field lens 120-2 is converted into a parallel light beam by the collimating lens 120-3, and then the output light beam from the mirror 120
-4 to the filter table 122. The parallel light beam that has passed through the filter is split into two by a half mirror 124, and the two are irradiated onto the magnetic fields of the inner and outer circumferential sides of the RAD slider.

In FIG. 2(a), the outer peripheral side is shown, and the light flux passing through the half mirror 124 is directed to the condenser lens 1.
25. Objective lens 127 through half mirror 126.
The objective lens 12 is guided on the axis of the photoelectric conversion unit 131-4.
7 as a parallel beam of light.

Glass disk 5-2. Magnetic hent slider 6 on the outer circumference side
- Irradiate the measuring section of 4.

Note that the luminous flux split toward the inner circumferential side is split by a half mirror 124.
' After passing through the same route, go through the glass disk 5-
2. The measuring portion of the magnetic head slider 6-3 on the inner circumferential side is irradiated.

In the measuring section, a glass disk 5-2. Interference fringes are generated corresponding to the spacing between the magnetic helad sliders 6-4, that is, the flying height of the magnetic head.

The reflected light of this interference fringe is reflected by the objective lens 127. lens 12
8, 129, and 130, an image is formed at a specific magnification on a photoelectric conversion unit 131-4, which is an MO8 type camera. This photoelectric conversion section 131-4 converts interference fringes into electrical signals.

The same holds true for the other three sets of optical systems.

As shown in FIG. 2(C), the configuration of the filter table 122 is such that it can output white light (wavelength λ0) and a plurality of monochromatic lights (wavelengths λ1, λ2, λ3, λ4, λ5 in this embodiment). ND filter 122-0 and interference filter 12
2-1, 122-2, 122-3.

122-4 and 122-5 are arranged on the table. As shown in FIG. 1, the filter table 122 is rotated by a drive motor 123 to switch between the respective filters. The rotation angle of the drive motor 123 is controlled by the mechanical controller 13.

In this way, in this embodiment, by sequentially switching the wavelength from white light to a plurality of monochromatic lights, it is possible to image the most efficient interference fringes in terms of measurement.

Interference fringes imaged by the optical systems 12-1 and 12-2 are generated simultaneously at four measuring sections. As shown in FIG. 1, these image signals are sequentially switched by a switching circuit 14 and taken into an image processing device 15.

The image processing device 15 includes an A/D converter 16, a frame memory 17, a preprocessing circuit 18, and a CPU 1 related to arithmetic control means.
9. In particular, the CPU 19 has an access memory 20 reserved for storing image data.

21 is a protective cover for the glass disk 5-1.5-2.

In addition, in this embodiment, as shown in FIG.
1 are arranged independently on the left and right sides, but it is also possible to use one light source unit and divide the light beam into two systems via a half mirror.

Here, the functions and operations of each part of the control system will be explained.

The switching circuit 14 is a circuit for sequentially switching images from the photoelectric conversion units 131-1, 131-2, 131-3, and 131-4 in accordance with a command from the CPU 19.

The A/D converter 16 is a circuit for converting the above image signal into a digital signal.

The frame memory 17 is stored in the photoelectric conversion units 131-1, 131-2, 131-3°13 according to instructions from the CPU 19.
The image output from 1-4 is changed to 1 so that the screen does not flow.
A memory that freezes and stores the screen.

It is coupled to a preprocessing circuit 18 .

The preprocessing circuit 18 performs Ibara's operations.

1) Image on frame memory 17, generally horizontal (X)
An image consisting of 512 pixels and 480 pixels in the vertical direction (Y) is scanned M lines in the Y direction at intervals in the X direction, and the luminance data of the line is transferred to the access memory 20 in the CPU 19. At this time, depending on the case, m scans may be performed for each of the M scans, and the average of the m scans may be transferred to the access memory 20.

2) Based on the position information (described later) from the CPU 19, a line (in this embodiment, two lines as described later) is scanned in the X direction at intervals in the Y direction, and the brightness data of the line is sent to the CPU 19.
19 to the access memory 20. At this time, depending on the case, each book may be scanned separately and then transferred to the access memory 20 as an average of the books.

The CPU 19 performs image data processing. for example.

Arithmetic processing such as edge detection, peak position detection, peak position correction, and optical distortion correction, which will be described later, is performed by directly calling the data in the access memory 20.

The mechanical controller 13 operates according to instructions from the CPU 19,
Control of load door/load mechanism 11, filter table 1
22, that is, drive the drive motor 123.

Next, a measuring method using the magnetic head flying height measuring device having such a configuration will be explained with reference to FIGS. 3 to 9 in conjunction with FIGS. 1 and 2 above.

FIG. 3 is a flowchart showing the procedure for measuring the flying height using the apparatus shown in FIG. 1, FIG. 4 is an explanatory diagram showing the procedure for detecting the rail position using white light, and FIG. 5 is an explanatory diagram showing the procedure for detecting the rail position using white light.

Diagrams showing an example of image data, (a) is white light brightness data, (b) is monochromatic light (λ1) brightness data, (C) is a flying height curve, and Figure 6 is peak position detection and peak position. FIG. 7 is an explanatory diagram showing the details of correction, FIG. 7 is an explanatory diagram of optical distortion correction, FIG. 8 is an explanatory diagram showing the order discrimination method, and FIG. 9 is an explanatory diagram showing the order determination method.
FIG. 3 is a diagram showing a distribution of flying height corresponding to a change in wavelength of an optical system.

In the following description of FIG. 3, the guide arm 10 is equipped with a magnetic helide slider 6-1. 6-2. 6-3. The plurality of measurement objects equipped with the head unit 6-4 will be referred to as a head unit. In addition, photoelectric conversion sections 13-1, 13-2, 13-3.
13-4 is simply a camera, magnetic radar slider 6-1.
6-2. 6-3. The flat portions of the slider on both sides of the magnetic head in 6-4 are referred to as slider rail surfaces (interference fringe generating portions), and the position detection of the magnetic helad slider is referred to as rail position detection.

The details of this slider rail surface are shown in FIG. 8(a).

Shown in (b). In FIGS. 8(a) and (b), 5 is a glass disk, 6 is a magnetic helad slider, and the first
Glass disk 5-1.5-2, magnetic helad slider 6-1.6-2. 6-3. 6-4 is shown as a representative p, 6a is a magnetic head, and 6b is a slider rail surface.

As shown in FIG. 3, first, in preparation for measurement, the head unit is attached to the load/unload mechanism 11 and loaded between the glass disks 5-1 and 5-2.

The measurement process from the time the device is positioned at the measurement point to the time of unloading and removal of the head unit is completely automated, as explained below.

The mechanical controller 13 rotates the system pin lure, and when the number of rotations of the glass disk 5-1, 5-2 reaches the measurement number of rotations and is positioned at the measurement point, a measurement start ready signal is input to the CPU 19.

The CPU 19 controls the filter table 122 via the mechanical controller 13 to output the ND filter 122-0.
irradiates the measuring section with white light (wavelength λ0).

For white light, the CPU 9 controls the switching circuit 14 and converts this image signal into A as camera +1 (131-1).
After /D conversion, one screen is stored in the frame memory 17 and the image is frozen. The frozen image is scanned by three lines in the Y direction, which will be described later, by the preprocessing circuit 18, and the CP
U19 detects the contour of the magnetic herad slider 6-1,
Rail position detection is performed to detect the center position of the slider rail surface 6b.

This rail position is sent to the CPU 19 as position information of the measuring section.
held within.

Here, details of the rail position detection procedure using white light will be explained with reference to FIG. 4.

As shown in Fig. 4(a), xl + X2 + X3 is spaced in the X direction with respect to the two slider rail surfaces.
Input the luminance signals of 3 lines and convert the luminance data to C.
Transfer to the access memory 20 of the PU 19.

Therefore, as shown in FIG. 4(b), the CPU 19 detects the edge position in the Y direction. FIG. 4(b) shows the luminance signal input of the X1 line shown in FIG. 4(a). The dimensions of each slider rail surface edge from the reference point are 1. as shown in the figure. -1. Then, the center position of the two slider rail surfaces is.

Each t1+42 -13+t4 is required.

This is obtained for each line xl t x2 + x3 and approximated by a straight line.

The rail center center line is y as shown in Figure 4 (C).
=ax-)-b, address coordinate system X within one screen,
It is detected as an intercept bl and a slope at for Y. In Figure 4 (C), there are two slider rails, so h
(at*bt)t (221b2).

This (all b,) is called position information.

Once the position information for camera ≠ 1 is found, then move the camera to +2
(131-2), +3 (131-3), Su4 (13
1-4) and performs the same process to obtain position information of the measurement units by all cameras.

Since the rail position is detected by irradiating white light, the brightness level of the interference light on the slider rail surface can be increased. Therefore, it is possible to completely eliminate detection errors that occur when the dark part of the interference fringes caused by monochromatic light coincides with the scanning position in the Y direction, thereby making automatic measurement possible.

Note that the number of scanning lines in the Y direction is X l r X2 v
It is not limited to three X3.

When all location information is obtained for all four cameras,
This time, the position information is used to import luminance data for the required number of lines.

In Fig. 3, return to camera 4P1 with white light (wavelength λ0), freeze the image, and (att
b+), the lines, for example 4 lines (not shown), are sequentially captured and averaged, and the average processing is performed from 4 lines to 1 line, and the luminance data of 1 line for each slider rail is stored in the CPU 19. Transfer to access memory 20.

Do this for all cameras. This is the step of image capture 1 shown in FIG.

Next, the mechanical controller 13 controls the filter table 1.
220 rotation angle is controlled, monochromatic light of wavelength λl is irradiated using the interference filter 122-1, and the same processing as shown in step 1 of capturing one image is performed based on the position information obtained using white light. This is the step of image acquisition 2, and the wavelength λ
2. λ3゜λ4. For λ, the camera is +1, respectively.
While switching from +4 to +4, the luminance data of one line per slider wheel is transferred to the access memory 20 in the CPU 19.

Image capture is completed when luminance data of all cameras and all wavelengths have been captured.

Next, arithmetic processing is performed on image data using these luminance data.

An example of the captured image data is shown in FIG.

Figure 5(a) shows the image data of the measuring section using white light.
The horizontal axis represents the address of 512 pixels, and the vertical axis represents the brightness. The abrupt change part e of the interference fringes is the edge position of the magnetic head slider.

FIG. 5(b) shows image data of the measurement unit using monochromatic light of wavelength λ1, with address on the horizontal axis and brightness on the vertical axis. The extreme value p indicated by the arrow is the peak position.

e is the edge position.

As shown in FIG. 3, edge position detection, peak position detection, peak position correction, and optical distortion correction are performed on the interference fringes of the image data shown in FIGS. 5(a) and 5(b).

Edge position detection is a process for measuring the shape of the magnetic slider in the X direction, and the maximum point of brightness change is determined to be the edge position.

Peak position detection is to find the extreme value of one image data.

Note that peak position detection is not performed for white light.

FIG. 6 is an explanatory diagram showing the details of peak position detection and peak position correction, and shows the interference fringes of image data, where the horizontal axis is the address and the vertical axis is the brightness. ) Luminance differential peak detection.

(C) Noise peak removal and (d) Peak position correction methods are shown separately.

First, as shown in FIG. 6(a), smoothing is performed to smooth out the thin unevenness of the line before processing and replace it with a simple and smooth line like the line after processing. An example of the smoothing method is shown in the following equation.

Subsequently, brightness differential peak detection is performed to determine the position where the brightness differential value=0 as the peak. In Figure 6(b).

■ is the range of the line going up from the lower peak to the upper peak, e is the range of the line going down from the upper peak to the lower peak, and each peak detection position is indicated by an arrow on the X axis. .

As it is, incorrect peak positions due to noise are included, so the peaks due to noise are removed. This is shown in FIG. 6(C).

As the noise peak removal method, either a slice level method or a peak shape discrimination method may be adopted.

The slice level method sets a fixed width, or noise removal zone, in the center of each of the upper and lower peaks of luminance data, and automatically detects peak positions with addresses within this range as noise peaks. This is a method of removing it. The peaks excluding those shown as noise peaks in the figure (C) are the interference fringe peaks, and the positions of the interference fringe peaks excluding the noise peaks are indicated by arrows on the X-axis.

The peak shape determination method is a method for determining noise peaks by focusing on the alternating symmetry of an interference fringe pattern.

In the example shown in FIG. 6(C), both methods are adopted.

For the peak position determined in Figure 6(C), further
Peak position correction is performed as shown in Figures (d) and (e).

(e) is a detailed enlarged view of section E in (d).

That is, with respect to the peak position determined in FIG. 6(C),
Furthermore, around each peak position, ±m in the vicinity
Take pixels (for example, ±20 pixels).

A least squares approximation is performed using an n-dimensional equation to obtain an approximate curve, and this extreme value is determined to be the correct peak position.

Note that in this embodiment, n=2.

As is clear from the figure, the detected peak position indicated by the broken line is
Although the position of the maximum value of the detected peak is taken, the correct peak position after correction shown by the dashed line can be obtained by the above-mentioned correction calculation.

Using the method described above, the peak position and edge position can be found for all wavelengths and brightness data on all slider rail surfaces.

Next, optical distortion is corrected for each of the determined peak positions and edge positions.

As shown in Figure K7, optical distortion correction is performed by photoelectronically converting the input image (see Figure 7 (a)) obtained by fixing a grating whose accuracy is known in advance to the measurement point of the magnetic rad slider and photographing it with the optical system. Measure the entire optical distortion, including the geometric distortion on the conversion surface.

From this measurement result, correction amounts that should be correctly detected are determined for all cameras, and one image is processed to correct the detected edge positions and peak positions.

For the optical strain measurement values, as shown in Figure 7),
From the measured values, f is a quadratic function approximation of the strain amount of the reference grid
(y)=a y''+b y+c It is possible to calculate the null correction amount function and correct optical distortion from (a, b, C).

In other words, the optical distortion can be replaced with an approximation curve of the n-th order equation, and the distortion can be corrected using this coefficient.

This makes it possible to significantly reduce the amount of data stored for correction.

Next, edge position detection and peak position detection were performed on the luminance data from wavelength λ0 to λ5 for each slider rail surface on all cameras as described above, and as shown in Figure 3. Next, the order is determined for each slider rail surface on all cameras to determine the flying height at each peak position.

Next, the order discrimination method will be explained with reference to FIG.

FIG. 8 (→ is a front view of the measurement section where the magnetic herad slider 6 and the glass disk 5 face each other, and 6a indicates the magnetic head.

FIG. 8(b) shows the slider rail surface 6 that generates interference fringes.
b is a plan view showing the center rail 6C.

FIG. 8(C) is a diagram showing the peak of the interference fringe, with the horizontal axis representing the position (address) and the vertical axis representing the brightness, and the wavelength λ
When the luminous flux is l, the peak position of the interference fringe in the dark area is Xr,
Assuming that X2 is obtained, Fig. 8 (a), (b),
(C) Corresponding positions are indicated by dashed lines in each figure.

Glass disks in Xl, X2 positions5. The spacing between the magnetic helide sliders 6, ie, the flying height of the magnetic head, is determined by the following equation.

Note that the following equation holds true for the interference fringe peak in the bright area.

...(2)' Next, the peak position of the interference fringe of λ2 (λ2>λ,) is used to determine the order n. Assume that Xs moves less than X' as shown by the broken line in FIG. 8(C).

The order n can be determined by the following equation.

Such processing is carried out at wavelength λ! The order can be determined accurately by performing this on the dark part of ~λ5.

If the slider rail surface 6b of the magnetic herad slider 6 is a straight plane, the order n can be determined in principle by one calculation using equation (3). If it is not a straight plane.

Repeat the calculation of equation (3) as many times as necessary. Once the order n is determined, the flying height at each detected peak position is (2)
, can be determined by equation (2').

The number of peak positions in the dark and bright areas of the five wavelengths λl to λ5 is about 10 to 40 in this example, and the flying heights of these are as follows:
It changes depending on the shape of the rail surface.

Figure 5 (C) shows the distribution of the flying height corresponding to each address position of the edge and peak shown in the image data of Figures 5 (a) and (b), with the horizontal axis representing the address and the vertical axis representing the flying height. Amount (μm
) is shown.

Further, in FIG. 9, wavelengths λl, λ2. The distribution of flying height measured with the optical system of λ3゜λ4 is shown on the horizontal axis (address).
, the vertical axis shows the flying height.

In this way, all the flying heights in the bright and dark areas measured by the optical system with wavelengths λ1 to λ5 are calculated using the n-order equation (in this example, the quadratic equation).
A least squares approximation is performed to obtain a flying height curve that approximates the surface, and the flying height at the edge position is measured as the flying height of the magnetic head section.

The final flying height curve shows a low-order ridge distribution of the surface shape. By extending the flying height curve, the flying height at the edge position can be detected with high accuracy without error.

According to this embodiment, the spacing between the glass disk and the magnetic head slider, that is, the flying height of the magnetic head, is
High precision and high speed automatic measurement is possible.

Furthermore, the surface shape of the magnetic herad slider can be detected, and higher-order surface roughness components can also be automatically detected with high precision and high speed.

Therefore, it is possible to simultaneously detect the flying height and the surface shape, which was not possible in the past, so that detailed product inspection is possible and reliability can be ensured.

In addition, although the above-mentioned Example explained the flying height measurement of the magnetic Herad slider of a magnetic disk device, this invention is not limited to this, and is applicable to a VTR.

It can be applied not only to magnetic heads of information recording devices such as floppy disk drives, but also to measuring the spacing between perpendicular magnetic heads, thin film heads, etc. and information recording media.

Further, in the above embodiment, the magnetic disk of the magnetic disk device is a transparent glass disk. However, the present invention is not limited to this, and the magnetic head slider may be made transparent. It is possible to generate interference fringes, and similar effects can be expected.

Furthermore, by devising noise removal techniques and least squares approximation formulas for image processing, it is possible to improve the accuracy of measurements.

Further, by providing a highly accurate detection of wavelength changes in the optical system, it is possible to achieve high precision in quantity measurement.

〔Effect of the invention〕

As described above, this embodiment provides a magnetic head flying height measurement device that can automatically measure the spacing between a rotating information recording medium and a magnetic head, that is, the magnetic head flying height with high precision and high speed. can be provided.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a magnetic head flying height measuring device according to an embodiment of the present invention, FIG. 2 is a detailed diagram showing the optical system of FIG. 1, and (a) is a block diagram; ) is an enlarged view of the field lens, (C) is an enlarged front view of the filter table, and (C) is an enlarged front view of the filter table.
4 is an explanatory diagram showing a procedure for detecting a rail position using white light. FIG. 5 is a diagram showing an example of image data. (a) is white light luminance data, (b) is monochromatic light (λ
1) Brightness data, (e) is the flying height curve, Figure 6 is an explanatory diagram showing details of peak position detection and peak position correction, Figure 7 is an explanatory diagram of optical distortion correction, and Figure 8 is first order FIG. 9 is an explanatory diagram showing the determination method, FIG. 9 is a diagram showing the distribution of the flying height corresponding to the wavelength change of the optical system, and FIG. 10 is a schematic configuration diagram of a conventional flying height measuring device. 5.5-1.5-2...Glass disk, 6.6-1
゜6-2. 6-3. 6-4...Magnetic slider, 6a...Magnetic head, 6b...Slider rail surface, 7...Spindle, 11...Load/unload mechanism, 12-1.12-2... Optical system, 120...
Xenon lamp, 120-2...field lens,
121... Light source section, 122... Filter table,
123... Drive motor, 124, 124', 126.
... Nohef mirror, 125 ... Condensing lens, 127
...Objective lens, 128°129.130...Lens, 131-1,131-2°131-3,131-
4... Photoelectric conversion unit, 13... Mechanical controller, 1
4...Switching circuit, 15...Image processing bag! , 16・
・・A/D converter, 17・・Frame memory, 18・
...Preprocessing circuit, 19...CPU, 20...A1
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Claims (1)

[Claims] 1. A magnetic method in which one of the information recording medium and the magnetic head is a transparent body, and the spacing between the information recording medium and the magnetic head is measured from interference fringes caused by optical interference. A head flying height measurement device comprising: a light source section having multiple wavelengths and equipped with a light amount unevenness smoothing means; a wavelength variable means for switching the wavelength between white light and a plurality of monochromatic lights; and a plurality of measurement sections. an optical system consisting of a lens system that simultaneously generates interference fringes and forms an image of the interference fringes, a plurality of photoelectric conversion sections that convert the interference fringes into electrical signals, and a switch that sequentially switches output signals from the plurality of photoelectric conversion sections. circuit, and the plurality of measurement sections are first irradiated with white light by the optical system, the images of the measurement sections output by the plurality of photoelectric conversion sections are input, and the outline of the measurement sections is detected by detecting the outline of the image. Position detection is performed, and then, using the position information that is the result of the position detection, while changing the wavelength by the wavelength variable means, brightness data of interference fringes generated at specific positions of the plurality of measurement units at each wavelength is sequentially obtained. A frame memory having a preprocessing circuit that stores image data based on luminance data from the plurality of photoelectric conversion units at each of the wavelengths; detecting the edge position of the magnetic head in the area, detecting the peak positions of bright and dark areas of the brightness data of the interference fringe, correcting the peak position by removing noise at the peak position, correcting optical distortion of the optical system, and detecting the interference. an image processing device comprising an arithmetic control means for determining the order of stripes to obtain a magnetic head flying height curve and calculating the flying height of the magnetic head at a specific position from the curve; A magnetic head flying height measuring device comprising an information recording medium, a magnetic head, and a control means for controlling the optical system. 2. In the image processing apparatus according to claim 1, the frame memory is provided with a preprocessing circuit, the CPU related to the arithmetic control means is provided with an access memory, and frozen interference fringes are stored in the frame memory. The image is configured to perform a plurality of line scans in the X and Y directions of the image by the preprocessing circuit, and transfer luminance data for contour detection from the frame memory to the access memory. A magnetic head flying height measurement device.