JPH0246517A - Method for measuring gap width of magnetic head - Google Patents

Abstract

PURPOSE:To eliminate the impossibility of the judgement of a boundary part by a diffused light and to attain the high accurate measurement by measuring a gap width with the number of bits obtained by the A/D conversion of an analog signal voltage from a line sensor built in a microscope. CONSTITUTION:The gap width of a magnetic head composed of a material with a different reflecting ratio is detected as an analog signal voltage by a line sensor 9 built in the microscope, after the correction is executed up to the reference voltage set beforehand, the suitable slice level is applied by the circuit, the number of the bits of the horizontal signal at this time is obtained by the A/D conversion, and with the correction curve of the real value of the gap width and the number of the bits obtained beforehand, the number of the bits of the horizontal signal is corrected. Thus, the judgement imposibility of the boundary part to occur by the diffused light due to the material with a different reflecting ratio is eliminated and a high accurate gap measurement can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for measuring the gap width of a magnetic head made of three types of materials having different reflectances.

<Prior art> Conventionally, as shown in Fig. 1(a), a non-magnetic material made of glass or the like is used between the magnetic cores, and permalloy or FeAtSi is used.
The gap width of a magnetic head called metal-in-gap, which uses a magnetic material such as an alloy (sendust) or amorphous, has been measured visually using an optical microscope (shearing method).

<Problems to be solved by the invention> In the conventional visual measurement, an operator uses a microscope to judge the gap width, but it is difficult to measure the width of the gap by using a microscope. When a material having a relatively low reflectance is combined with a material having a relatively low reflectance, the smaller the glass portion 1c becomes, the more difficult it becomes to visually determine the boundary between the glass portion 1c and the metal portion 1b. For this reason, there is a problem in that errors are likely to occur in measurement, and measurement accuracy varies (variation) due to individual differences among workers.

In addition, in the shearing method, only the metal part 1b is measured;
After that, the glass portion 1c has to be measured independently from the previous measurement, so there is a problem that simultaneous measurements are impossible in principle and it takes time to measure the gap width.

<Means for solving the problem> In a method for measuring the gap width of a magnetic head formed from materials with different reflectances using an analog signal voltage from a line sensor built into a microscope, an analog signal from the line sensor is used. The maximum value of the vertical voltage signal is corrected to a preset reference voltage value, the corrected analog signal voltage waveform is multiplied by a predetermined slice level in a circuit, and the bits of the horizontal signal of the line sensor at the slice level are The gap width is determined by A/D conversion (analog-to-digital conversion), and the correlation between the true value of the gap width determined in advance using a microscope and the number of bits determined by the measurement is made into a correction curve.
This is a method for measuring a gap width of a magnetic head, in which a gap width determined by correcting the number of bits determined by the A/D conversion using the correction curve is measured.

<Operation> According to the means described in item 1, reflections of materials with different reflectances are detected as an analog signal voltage by a line sensor built into the microscope, and the maximum value of the analog signal voltage is increased to a preset reference voltage. After the correction, a predetermined slice level is applied to the circuit, the number of bits of the horizontal signal at this time is determined by A/D conversion, and a correction curve is created between the true value of the gap width determined in advance and the number of bits. By correcting the number of bits using , it is no longer impossible to determine the boundary due to diffused light as in the conventional method, and by performing digital processing, highly accurate measurement is possible.

<Example> Hereinafter, the principle and one example of the present invention will be described with reference to the drawings.

FIGS. 1(a) to 1(c) are diagrams illustrating detailed explanations of the present invention,
Figure 2 is a block diagram showing the signal processing system; Figure 3 is a block diagram showing the signal processing system;
The figure is a waveform diagram showing the processing principle of analog signal voltage waveform.
FIG. 4 is a correction curve showing the correlation between the measured value (bit number) measured by the measuring method of the present invention and the actual measured value (true value) measured by an optical microscope.

In FIGS. 1(a) and 1(b), l is an object to be observed, such as a gap part of a magnetic head, and this object 1 is
For ease of explanation, for example, 1a is Fe-Si-A
The object 1b with a high reflectance such as a t-alloy magnetic material is an object with an intermediate reflectance such as a ferrite magnetic material, and the object 1c is an object with a low reflectance such as glass, and three types of materials are combined. Let it be the gap of the magnetic head. 2 is a microscope lens, and FIG. 1 (C) is, for example, a built-in microscope (not shown).
The figure shows the output waveform of the analog signal voltage from the line sensor.

An image captured through the lens 2 of the microscope is output as an analog signal voltage 4 through a line sensor.

3 indicates a preset reference voltage, 7 indicates a voltage increasing direction, and 6 indicates a horizontal signal scanning direction. In addition, in the example, the line sensor is 512 Bi in % inch.
Although a resolution having a resolution of t was used, the present invention is not limited to this.

FIG. 2 shows a block diagram of the signal processing system, and input signals are processed as follows. For example, as shown in FIG. 3, if there is one concave and convex portion in the analog signal voltage output 4, the concave portion is a portion of an object 1c with a low reflectance such as glass (hereinafter referred to as the glass portion). ) The convex portion is the object 1a portion (hereinafter referred to as metal portion) having a high reflectance such as the magnetic alloy. Center 8 of the lowest value of the recess
a and the center 8b of the highest value of the convex portion are treated as separate objects. In FIG. 3, the analog signal voltage 4 appearing horizontally corresponds to an object 1b having an intermediate reflectance, such as a ferrite material constituting a magnetic circuit of a magnetic head.

(hereinafter referred to as ferrite section) First, the analog signal voltage from the line sensor 9 is read by the drive circuit 10 shown in FIG. After correcting the voltage to reach the reference voltage, the value is held. In FIG. 3, 4d is the distance from the ferrite part of the glass part 1c, and as shown, the ferrite part 1b and the glass part 1c, the ferrite part 1b and the metal part 1a, and the metal part 1a. At the boundary with the glass portion 1c, the resolution of the line sensor 90 cannot follow changes in reflectance, so the waveform becomes a curve. Therefore, since the true values 4F and 4C of the glass part IC or the metal part 1a cannot be obtained accurately, a slice level is applied to a part where there is no influence from the curve of the waveform. Find the number 4f. The processing in the circuit in step 1 is performed by the sample and hold amplifier circuit. Similarly, when finding the true value 4C of the metal part 1a, the metal part 1a is a part obtained by finding the distance 4a from the lowest value of the concave part to the highest value of the convex part, and processing it at an appropriate slice level like the glass part IC. 4C is obtained, and this part 4C is B of the metal part 1a.
The number of bits is 9. By A/D (analog-digital) conversion of this bit number by the A/D circuit 12, the values of the glass part IC and the metal part 1a are calculated by the integrating and averaging circuit 13, and the memory circuit 14. Next, using a personal computer 15'r, the correction curve shown in FIG. Alternatively, the cumulative gap width can be measured by adding them. The gap width determined above is displayed on a CRT (cathode ray tube). Accurate measurements can be made because there is a high degree of linearity between the measurement results obtained by the method described above and the actual measurement values obtained using a microscope. (FIG. 4) Therefore, the measuring method of the present invention can be put to practical use.

In the present invention, a line sensor is used, but it goes without saying that similar measurements can be made by using a CCD and image processing. Further, if the analog signal voltage 4 does not reach a specified voltage even after correction, a display is displayed indicating that measurement is not possible through circuit processing.

<Effect> As explained above, the present invention detects the gap width of a magnetic head made of materials with different reflectances as an analog signal voltage using a line sensor built into a microscope, corrects it to a preset reference voltage, and then detects the gap width of a magnetic head made of materials with different reflectances. Apply an appropriate slice level to the circuit, find the number of bits of the horizontal signal at this time by A/D conversion, and use the correction curve of the true value of the gap width and the number of bits found in advance to Since the number of signal bits is corrected and the gap width of the magnetic head is measured, there is no longer an inability to judge boundaries caused by diffused light caused by materials with different reflectances, which was the case in the past.
Moreover, by performing digital processing, there is a remarkable effect that highly accurate gap measurement can be performed.

[Brief explanation of the drawing]

1(a) to 1(C) are diagrams explaining the present invention in detail. FIG. 1(a) is a plan view showing the structure of the gap portion of the magnetic head, and FIG. FIG. 1C is a cross-sectional view of the main part of the gap portion of the head, and is a diagram showing an analog signal voltage waveform when the gap portion of the magnetic head is scanned by a line sensor. FIG. 2 is a block diagram showing an example of the signal processing system of the present invention. FIG. 3 is a waveform diagram showing the processing principle of analog signal voltage waveforms. FIG. 4 is a correction curve showing the correlation between measured values measured by the measuring method of the present invention and actual measured values. 1... Gap part of magnetic head, 1a... Metal part, 1b... Ferrite part, IC... Glass part, 2...
...Microscope, 3...Reference voltage, 4...Analog signal voltage waveform, 4F, 4C...Actual value measured by microscope, 4f
, 4c... Measured value of the present invention, 8a... Minimum value of analog signal voltage, 8b... Maximum value of analog signal voltage,
9...Line sensor 1r built into the microscope Figure 11

Claims (1)

Claims: In a method for measuring gap widths of magnetic heads formed from materials with different reflectances, the gap widths are measured. Attach a line sensor to the microscope, correct the analog signal voltage from the line sensor to a preset reference voltage, and then apply a predetermined slice level to the horizontal signal of the analog signal voltage waveform from the line sensor at this time. 1. A method for measuring a gap width of a magnetic head, characterized in that the number of bits is determined, and the gap width is measured by correcting the number of bits using a correction curve determined in advance.