JPH05101352A - Grinding method for magnetic head and height adjusting method for magnetic head - Google Patents

Abstract

PURPOSE:To provide a grinding method of a magnetic head capable of forming an optional front surface shape and a height adjusting method of the magnetic head capable of adjusting the exact height on a rotary cylinder by solving such problems that an exact grinding and a height adjustment are impossible or that much labors and times are required, in the grinding method of the magnetic head being used in a magnetic recording device and the height adjusting method of the magnetic head. CONSTITUTION:The front surface of the magnetic head 1 attached on the rotary cylinder 8 is optically measured by using laser beams reduced in interference property. By using a fuzzy arithmetic circuitry 12, shape recognition is performed and a running tension of a grinding tape 13 is controlled and the front surface of the magnetic head 1 is ground in an optional shape. Also on the rotating cylinder, a head base is mounted and a surface of a magnetic head attaching part on the head base is heated and fused and the attaching height of the magnetic head is adjusted. Manufacture of the magnetic head having an optional front surface shape and the exact height adjustment of the magnetic head are available.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of polishing a magnetic head used in a magnetic recording apparatus and a method of adjusting the height of the magnetic head.

[0002]

2. Description of the Related Art The front shape of a magnetic head used in a magnetic recording apparatus using a rotary cylinder is shaped by a magnetic head front polishing apparatus. This is attached to a small diameter cylinder so that the front of the magnetic head projects from the side of the cylinder.
By rotating the small diameter cylinder and running the polishing tape along the small diameter cylinder, the front surface of the magnetic head is lapped into a desired shape.

There is also a demand for highly accurate positioning of the magnetic head mounted on the rotary cylinder, especially for height adjustment of the head. This is a state where the rotating cylinder is stationary,
It is adjusted by the screw protruding from the cylinder. Furthermore, recently, a technique has been developed in which a height of a magnetic head is adjusted by melting a point on the head base and deforming the head base using a high-energy laser beam.

[0004]

With the recent diversification of magnetic recording devices and the increase in recording density, it is desired that the front surface of the magnetic head has various shapes. Since the small diameter cylinder rotates at a high speed, conventionally, the rotation is stopped and the head front surface shape is measured by a contact type shape measuring machine or a projector.
Based on the result, a great deal of labor and time were required to change the front surface polishing conditions to obtain a desired head shape. Also, since the height of the head attached to the rotating cylinder is adjusted while the cylinder is stationary, accurate height adjustment can be performed with a structure in which the magnetic head height is determined by dynamic balance using a fluid bearing or the like. There wasn't.

In order to solve these problems, there is a demand for measuring the shape of the head on a cylinder that rotates at a high speed. Conventionally, a strobe has been used to photograph a fast-moving subject. When stroboscopic light is applied to a rotating object and the rotation cycle and the pulsed light cycle match, the object appears to be stationary. However, the strobe accumulates charge on the capacitor,
Since it emits light, it is difficult to emit light of 1 μs or less. Further, when the light emission cycle becomes shorter, the amount of light decreases because the electric charge is not sufficiently accumulated. Further, when a high-power light source is used to increase the light quantity, a large spark noise occurs, which causes a serious adverse effect on the peripheral circuit system. A laser microscope using a laser as a light source uses a confocal optical system to avoid speckle noise due to interference of laser light. According to this method, speckle noise is reduced, but since light is scanned using an acousto-optic device or the like, surface measurement of an object moving at high speed cannot be performed.

The present invention is intended to solve the above problems,
An object of the present invention is to provide a magnetic head polishing method capable of extremely front polishing in a very short time and a magnetic head height adjusting method capable of accurately controlling the position.

[0007]

In order to achieve the above object, the present invention changes the shape of the front surface of a magnetic head by synchronizing the rotation of a magnetic head mounted on a rotating cylinder with the light emission of a light source. Optically measured, the magnetic head polishing conditions are changed in real time according to the measured sliding surface shape to polish the magnetic head.The head base is mounted on a rotating cylinder to rotate the light source and the light source. In synchronization with the cylinder, the gap position of the magnetic head is measured by a TV camera, the surface of the magnetic head mounting portion of the head base is heated and melted, and the mounting height of the magnetic head is adjusted.

[0008]

When the surface state is simply observed by using the laser light as the light source, as described above, speckle noise, which is a black and white mottled pattern, is generated due to the temporal and spatial coherence of the laser light. I cannot measure. This is an essential problem peculiar to laser light caused by interference between optical systems, dust, or surface roughness of a measurement object. In order to eliminate this coherence, a semiconductor laser is used
A high frequency sine wave is superimposed on the input. As a result, the spectrum has sidebands and the coherence is significantly reduced. Therefore, a clear image without speckle noise can be obtained. Therefore, an accurate head shape can be confirmed by observing the magnetic head on the cylinder that rotates at high speed using the objective lens, and an interference fringe image that is a contour map can be obtained by observing the magnetic head using the objective interference lens.

The shape of the front surface of the magnetic head greatly differs depending on the running tension of the polishing tape. If the traveling tension is high, a head having a small curvature is obtained, and if the traveling tension is low, a head having a large curvature is obtained.
Further, in order to change the shape of the sliding surface, a method is known in which different polishing tapes are used to change the polishing rate, the head protrusion amount, and the like.

According to the present invention, the running tension control of the polishing tape is performed by fuzzy reasoning. Here, fuzzy inference is an inference method that processes a variable (sensor input) according to a specific rule (fuzzy rule) and outputs a control amount. The fuzzy rule is expressed as if (x1 = A and x2 = B ....) then (y = z), which is similar to the human sense, and (x1 = A an
d x2 = B ....) is called the antecedent part, and (y = z) is called the consequent part. x1 = A
Means to find the degree to which a variable (sensor output, etc.) belongs to the membership function A (concept of the number of interference fringes).

FIG. 4 is a diagram for explaining one known method of outputting an inference result according to such a fuzzy rule. (A) and (b) of the figure show the membership functions corresponding to the two terms of the antecedent part, and (c) of the figure show the membership functions corresponding to the consequent part. Here, there are two cases (a) and (b) as the membership function of the antecedent part, but the membership function also increases as the conditions input to the antecedent part increase. In FIG. 4, the horizontal axis represents the value of the variable and the vertical axis represents the membership value (affiliation degree).

In FIG. 4A, it is assumed that the value of the variable X1 in the first term of the antecedent part is 0.2 and the degree of belonging thereof is 0.5. Further, in FIG. 4B, it is assumed that the value of the variable X2 of the second item of the antecedent part is 0.4 and the degree of belonging thereof is 0.3. In such a case, the fuzzy calculation unit takes the minimum value of the degree of belonging. In the above example, the degree of affiliation is 0.3. Next, the membership function corresponding to z is truncated at 0.3. When such inference is performed on one rule and the operation results corresponding to all the rules are ORed, an inferred value shown in the shaded area in FIG. 4C is obtained.
Normally, one quantitative value is determined, and the barycenter y ′ of the shaded portion for operation control is calculated with this value, and this is output as a fixed value. In the above inference method, the logical AND operation rule of the degree of belonging to the antecedent part (an operation to select the smaller degree of belonging) and the rule of the logical sum operation of the trapezoidal part to the consequent part are called mini-max rules. By performing such processing, smooth and quick control can be performed.

Further, when the surface of the head base is heated and melted by a high-energy laser beam, the head base bends due to thermal strain at the time of melting, and high-precision positioning is possible. If observation is performed using a laser beam with reduced coherence, the track height can be observed on the rotating cylinder even if the head rotates at a high speed of several tens m / s. Therefore, the height can be adjusted while measuring the head height in real time.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic head polishing method and a magnetic head height adjusting method according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram illustrating a method of polishing a magnetic head according to an embodiment of the present invention. FIG. 2 shows the interference fringes on the front surface of the magnetic head observed and extracted by the image processing circuit. In FIG. 1, 1 is a magnetic head, 2 is a semiconductor laser, 3 is an RF superimposing circuit, 4 is a laser power supply section, 5 is a rotary cylinder drive circuit, 6 is a beam splitter, 7 is an objective interference lens, and 8 is the magnetic head 1. Attached rotary cylinder, 9 TV camera, 10 TV monitor, 11 image processing circuit, 12 fuzzy arithmetic circuit, 13 polishing tape, 14 tension detecting arm, 15 photo coupler, 16 tension detecting circuit, 17 Is a take-up reel,
Reference numeral 18 is a supply reel, 19 is a take-up reel motor, 20 is a supply reel motor, 21 is a take-up reel motor drive circuit, and 22 is a supply reel motor drive circuit.

The semiconductor laser 2 has a wavelength of 780n.
m, output 40 mW, and emission time 0.5 μs. As the semiconductor laser 2 to be used, a semiconductor laser having an appropriate wavelength and output from a blue laser to an infrared laser may be selected depending on the wavelength characteristic of the TV camera 9 to be used and the object to be observed. A gas laser or the like is not suitable because the spectrum does not spread due to RF superposition and the transmission is not stable. The RF superimposing circuit 3 is 800M for a rectangular wave pulse.
It is a circuit that can superimpose a sine wave of Hz. The RF frequency should be higher than the rectangular wave frequency, 100 MHz
To 10 GHz is suitable. As a result, laser light emission with a wide side band can be obtained. The half-width of a semiconductor laser is usually 0.5 nm or less, but it can be expanded to about 5 nm by applying RF superposition, and a surface image with less speckle noise can be obtained. The conventional strobe method cannot set the pulse width in such a short time, and if the pulse width is long, an image is blurred and becomes unclear.

The rotation pulse of the rotary cylinder drive circuit 5 synchronizes the rotation of the rotary cylinder 8 and the light emission of the semiconductor laser 2. The laser light reduces the coherence by using the RF superposition circuit 3 and is reflected by the beam splitter 6 onto the surface of the magnetic head 1. The interference fringes generated on the surface of the magnetic head 1 are measured by the TV camera 9 with the objective interference lens 7. Simultaneously with the observation on the television monitor 10, the image processing circuit 11 extracts the interference fringes to obtain the three-dimensional shape of the surface of the magnetic head 1. The extracted interference fringe lines are shown in FIG. The obtained interference fringe pattern is input to the phage calculation circuit 12. The running tension of the polishing tape 13 is detected by the photocoupler 15 at the position of the tension detecting arm 14 and input to the fuzzy arithmetic circuit 12.

The fuzzy operation circuit 12 performs fuzzy inference based on this input, and outputs the drive currents of the take-up reel motor 19 and the supply reel motor 20 which are definite operation values. The take-up reel motor drive circuit 21 and the supply reel motor drive circuit 22 drive the take-up reel motor 19 and the supply reel motor 20.

The fuzzy arithmetic circuit 12 determines the polishing conditions by comparing the desired sliding surface shape input in advance with the interference fringe pattern. When the number of interference fringes is small, the running reel tension is increased by lowering the rotation speed of the supply reel motor 20 to be lower than that of the take-up reel motor 19, and the wrapping of the polishing tape 13 is tightened. Can be made smaller. When the number of interference fringes is large, the traveling tension can be reduced and the curvature can be reduced.

In order to change the shape of the sliding surface, several kinds of polishing tapes 13 having different stiffness are used, but it is also possible to change the protruding amount of the magnetic head 1. These controls may be performed in combination with phage control.

In order to reduce the coherence of the semiconductor laser 2 used as a light source, the light emitted from the semiconductor laser 2 by RF superposition is emitted as an acousto-optical element (A0 element), a rotary half mirror, a rotary prism, etc. Further spatial modulation can be applied by scanning the optical axis with (not shown). Thereby, speckle noise can be further reduced. RF emitted from the semiconductor laser 2
The phase of the laser light can be disturbed by passing the superimposed light through an optical fiber or an aspherical lens.
That is, phase modulation can be applied to the laser light. This method can further reduce speckle noise. Further, spatial modulation by an acousto-optic element or the like and phase modulation by an optical fiber or the like may be used together.

Although the case where the curvature of the head sliding surface is changed has been described above, it goes without saying that it can be used for controlling the center position of the interference fringes in the head thickness direction, controlling the gap depth, and the like.

It is also effective to perform the operation of the fuzzy operation unit by learning using a neuro element.

In the present invention, the membership functions in the antecedent part are the number of interference fringes and the running tension, but more membership functions may be input here. The membership function of the consequent part is running tension, and FIG. 3 shows the membership function for each variable. 3A shows the number of interference fringes, FIG. 3B shows the output of the running tension detection circuit, and FIG. 3C shows the membership function relating to the amount of current passed through the reel motor drive circuit. The symbols shown in FIG. 3 indicate the following contents. Output of image processing circuit VS: Small number of interference fringes SM: Slightly low MD: Almost target value LA: Slightly high BG: High output of running tension detection circuit VS: Low SM: Slightly low MD: Normal LA: Slightly high BG: High Reelmo -Current control amount DC: small difference in rotational speed DL: slightly small ZE: unchanged IL: slightly large IC: large Fuzzy inference is performed using such a membership function to supply reel motor 20 and take-up reel motor The definite value of the current control amount of 19 is obtained.

As a result, an arbitrary traveling tension can be set and an arbitrary sliding surface shape of the magnetic head 1 can be obtained.

FIG. 5 is a schematic configuration diagram for explaining a height adjusting method of a magnetic head according to an embodiment of the present invention, and FIG. 6 is an enlarged view of the magnetic head portion. 5 and 6, in FIG.
The same components as those shown in are attached with the same reference numerals and the description thereof will be omitted, and different components will be described. 23
Is an objective lens, 24 is a high energy laser emission source, 25
Is a head base, and 26 is a magnetic head mounting portion of the head base 25 melted by laser light.

The head base 25 is mounted on the rotary cylinder 8, and the rotation of the rotary cylinder 8 and the light emission of the semiconductor laser 2 are synchronized by the synchronizing pulse of the rotary cylinder drive circuit 5. The laser light reduces the coherence by using the RF superposition circuit 3 and is reflected by the beam splitter 6 onto the surface of the magnetic head 1. The gap portion of the magnetic head 1 is observed with the TV camera 9 using the objective lens 23, and the gap height is measured with the television monitor 10. The head base 25 is irradiated with the laser light emitted from the high energy laser emission source 24 in synchronization with the rotary cylinder 8 for a short time, and the magnetic head mounting portion 26 of the head base 25 is heated and melted. Thereby, the gap height of the magnetic head 1 can be changed. In this way, it is possible to adjust the head height on the rotating cylinder 8. The irradiation amount and irradiation time of the laser light may be fuzzy controlled.

[0028]

As is apparent from the above embodiments, according to the present invention, the sliding surface of the magnetic head can be rapidly polished and the mounting height of the magnetic head can be controlled, which is extremely industrial. It has high utility value.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an apparatus for carrying out a magnetic head polishing method according to an embodiment of the present invention.

FIG. 2 is a diagram in which an interference fringe generated on the front surface of the magnetic head is extracted by an image processing circuit.

FIG. 3A is a diagram showing a membership function used in the fuzzy inference unit used in the same embodiment, and FIG. 3B is a diagram showing a membership function used in the fuzzy inference unit used in the same embodiment. FIG. 7C is a diagram showing a membership function used in the fuzzy inference unit used in the embodiment.

FIG. 4A is a diagram for explaining fuzzy inference used in the magnetic head polishing method and the magnetic head height adjusting method according to an embodiment of the present invention; and FIG. 4B is an embodiment of the present invention. FIG. 3C is a diagram for explaining fuzzy inference used in the magnetic head polishing method and the magnetic head height adjusting method of FIG. 6C. FIG. 7C is a magnetic head polishing method and a magnetic head height adjusting method according to an embodiment of the present invention. To explain fuzzy inference used in

FIG. 5 is a schematic configuration diagram of an apparatus for carrying out a magnetic head height adjusting method according to an embodiment of the present invention.

FIG. 6 is an enlarged perspective view of the magnetic head portion.

[Explanation of symbols]

 1 magnetic head 2 semiconductor laser 8 rotating cylinder 9 TV camera 25 head base 26 magnetic head mounting portion

Claims (11)

[Claims] 1. The shape of the front surface of the magnetic head is optically measured by synchronizing the rotation of a magnetic head mounted on a rotating cylinder with the light emission of a light source, and the shape of the front surface of the magnetic head is measured according to the measured sliding surface shape. The method of polishing a magnetic head is characterized in that the polishing conditions of the magnetic head are changed in real time. 2. The method of polishing a magnetic head according to claim 1, wherein the light source is a laser light source with reduced coherence. 3. The method of polishing a magnetic head according to claim 2, wherein a semiconductor laser is used as the laser light source, and the input voltage to the semiconductor laser is frequency-multiplexed. 4. A method of polishing a magnetic head according to claim 2, wherein the laser light from the laser light source is spatially modulated by an acoustooptic device. 5. The method of polishing a magnetic head according to claim 2, wherein the laser light from the laser light source is passed through an optical fiber or an aspherical lens to perform phase modulation. 6. The polishing of a magnetic head according to claim 1, wherein the running tension of the polishing tape is fuzzy controlled on the basis of recognizing the shape of the front surface of the magnetic head from the interference fringes of the laser beam measured by the objective interference lens. Method. 7. A head base is mounted on a rotating cylinder, the light source and the rotating cylinder are synchronized, the gap position of the magnetic head is measured by a TV camera, and the surface of the magnetic head mounting portion of the head base is heated and melted. And a method of adjusting a height of a magnetic head, which comprises adjusting a mounting height of the magnetic head. 8. The height adjusting method for a magnetic head according to claim 7, wherein the light source is a laser light source with reduced coherence. 9. The height adjusting method for a magnetic head according to claim 8, wherein a semiconductor laser is used as the laser light source, and the input voltage to the semiconductor laser is frequency-multiplexed. 10. The laser light from the laser light source is spatially modulated by an acousto-optic device.
The height adjusting method of the magnetic head described. 11. The height adjusting method for a magnetic head according to claim 8, wherein the laser light from the laser light source is passed through an optical fiber or an aspherical lens for phase modulation.