JPS5928607A - Multi-dimensional measurement method of very small clearance - Google Patents

Abstract

PURPOSE:To measure the multi-dimensional clearances of an object to be measured by scanning the change in the interference bands generated by an ordinary optical system multi-dimensionally in optional directions and periods, separating the signal for multi-dimensional brightness from the scanning signal and processing said signal. CONSTITUTION:The interference bands on the surface of a slider 4 by the monochromatic light generated with a light source 1 is projected on a photoelectrical conversion part 8. The top surface of a slider 4 is scanned by the signals from horizontal and vertical scanning signal generators 10, 11. A brightness signal is separated from the scanned signal by a signal sepn. circuit 20, and the voltages V1, V2, V1', V2' in the horizontal direction corresponding to the peak position in the dark part of the interference bands and the voltage V0 in the edge part of the slider 4 are determined and the min. value of the clearance between a disc 3 and the slider 4 is determined by the equation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multidimensional measurement method for a minute gap that optically measures a minute gap between two objects to be measured.

A case in which conventional optical interferometry is used to measure a minute gap between an object to be measured, such as a disk and a slider of a magnetic disk device, will be described with reference to FIG.

A monochromatic light beam of wavelength λ generated by the light source section IA is bent downward by the beam splitter 2, passes through a transparent disk 3 that is one object to be measured, and passes through a transparent slider 4 that is the other object to be measured. incident on . In this case, the beam is partially reflected by the front surface 3a and back surface 3b of the disk 3, and is also reflected by the surface 4a of the slider 4. The beam reflected by the disk 3 and slider 4 passes through the beam splitter 2 and enters the photoelectric conversion element 5.

Here, the brightness of the interference light generated when the beams reflected from the front surface 4a of the slider 4 and the back surface 3b of the disk 3 overlap, as shown in FIG. 2, changes depending on the size of the gap between the slider 4 and the disk 3. do. That is, when h-00, the brightness of the interference light is the darkest, and when h=, the brightness of the interference light is the brightest. Therefore, if the change in brightness of the interference light is converted into an electrical signal by the full photoelectric conversion element 5 and measured, the gap hy can be determined only for that measurement point. However, this method has the following drawbacks.

Medium Even though the opposing surfaces of the slider and disk are two-dimensional, only one point can be measured. Therefore, rolling, pitching, yawing, etc. of the slider cannot be measured.

(11) The brightness of the interference light is related to the brightness of the reflected light as well as the optical path difference, so due to changes in the brightness of the reflected light due to changes in the amount of light and changes in the disk 3 and slider 4,
Since the brightness of the interference light changes, measurement accuracy decreases.

In view of the above, it is an object of the present invention to easily measure the average gap and the time-varying gap amount of a multidimensional micro gap formed between two objects to be measured, and to improve the measurement accuracy. It is something to do.

In order to achieve the above object, the present invention generates interference fringes in minute gaps between objects to be measured using ordinary optical interferometry.
This interference pattern is scanned over multiple dimensions in arbitrary directions and periods, and a multidimensional brightness signal is separated from this scanning signal.
This signal is characterized by being processed.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 3, 1 is a light source with a monochromator that generates a double-color beam with a wavelength λ, 2 is a beam splitter, 3 is a transparent disk that is one of the objects to be measured, and 4 is the other transparent disk that is opposite to the transparent disk 3. An opaque slider that is the object to be measured,
7 is a mirror that changes the optical path from the beam splitter 2;
8 is a photoelectric conversion unit for projecting an interference fringe image generated by the reflected light reflected by the disk 3 and the slider 4; 9;
10 is a horizontal scanning signal generator; 11 is a vertical scanning signal generator; 12 is a setting circuit for setting the scanning center, scanning period, and scanning width; 131; 14 is a filter circuit that amplifies the output of the photoelectric conversion unit 8 and removes high-frequency noise components; 15
20 is a data processing circuit that determines the flying height from each separated two-dimensional signal, and 20 is a signal separation circuit that separates a multidimensional signal (here, a two-dimensional signal).

The signal separation circuit 20 has a configuration as shown in FIG. That is, 20-1 is a high voltage hold circuit that partially holds the output 16 of the filter circuit 14, and a 2O-2V
iA/D converter 20-3 is a switch circuit that separates the digital signal of A/D converter 20-2, 20-4 a
, 20-4b is a latch circuit for temporarily storing the digital signal; 20-5a, 2O-5b is a D/A converter for outputting the latched signal as an analog signal; 2O-6a;

2O-6b is a comparison circuit that detects the sign of the difference between the signal after latching and the signal before latching.

Next, the operation of this embodiment configured as described above will be explained.

A monochromatic light beam of wavelength λ generated by a light source 1 is bent downward by a beam splitter 2, passes through a transparent disk 3 that is one object to be measured, and is transmitted to an opaque slider 4 that is the other object to be measured. incident. In this case, the beam is partially reflected by the surface 3a and the cutting surface 3b of the disk 3, and is also reflected by the surface 4a of the slider 4. The light reflected by the disk 3 and the slider 4 passes through the beam splitter 2, is further bent by the mirror 7, and enters the photoelectric converter 8 to form an image of interference fringes.

The position of the dark or bright part of the interference fringes imaged on the photoelectric conversion unit 8 is detected, and the position of the
Dimensional minute gaps can be found. In this case, the bright areas will be considered in the same way as the dark areas, and then some of them will be discussed.

In FIG. 5, h represents the gap between the disk 3 and the slider 4, and the slider 4 is assumed to be tilted arbitrarily as shown in the figure.Slider 4
Interference fringes appear on the surface (t) as shown in FIG. By doing this, a bright explosion signal as shown in Figure 5 (3) can be changed.For example, when horizontal scanning is performed at position a in Figure 5 (2), the brightness signal is changed by +3) in Figure 5 (2).
A brightness signal of -(a) is obtained, and when horizontal scanning is performed at position b in (2) of the same figure, a brightness signal of (3)-(b) of the same figure is obtained. The position of the photoelectric conversion unit 8 can be arbitrarily determined from the horizontal scanning voltage ±Vx and the vertical scanning voltage ±VyK.

[7 Therefore, for example, the horizontal voltage VI * v2+ v,' +V corresponding to the peak position of the dark part of the interference fringe
2' and the voltage V0 at the edge of slider 4.
t1. If each calculation is t''I5, the minimum value of the gap is the queen (I
It can be obtained from the formula X2).

(k: Order of interference fringes) (2 lbs of starvation, Fig. 5 (3)) It is difficult to judge.

Next, the scanning body H shown in FIG. 5(2): (at (b)
A method for performing multidimensional scanning -i\- by scanning all at the same time will be described. Although scanning of two parallel positions S will be described here, it goes without saying that the scanning direction, scanning position, and number of scanning positions can be arbitrarily selected.

FIG. 6 shows two scanning methods.

First, the scanning waveform will be shown.

Figure 6 (1) (If is a sawtooth wave, (b) is Y for each scan.
It shows a rectangular wave that changes direction scanning position fit. e14-f,
A clock signal indicating the horizontal scan interval.

(A) in FIG. 6 (2) shows a sawtooth wave as in (1), and (C) is a clock signal showing the horizontal scanning interval. This shows a rectangular wave that changes the scanning position in the Y direction in short cycles.

Figure 6 (1) shows the alternator 1 method, scanning position (a)
This is a scanning method in which (b) is sequentially repeated. Figure (2) is a chopper type scanning method in which the scanning voltage of the Y method is chopped and input as a two-dimensional scanning signal from the XY deflection to the photoelectric conversion unit. The signals shown in (a) and (0) of FIG. 6(2) are generated by a horizontal scanning signal generator 10 and a vertical scanning signal generator 11 (see FIG. 3), respectively. Both signals are inputted to the XY deflection circuit 13 with the scanning amplitude, scanning center, and scanning period fully set by the setting circuit 12 in order to effectively scan the interference fringes on the photoelectric conversion surface. The scanning signal in the Y direction is an integral multiple of the scanning period (for example, 512etC
) is input as a square wave using the reference block.

By changing the DC level of this square wave, it is possible to match it to the center of the slider 4, and by further changing the amplitude, it is possible to scan the top surface of the slider 4. When the top surfaces of the two sliders are not parallel, scanning can be performed in the same way by inputting a square wave whose amplitude changes linearly.

On the other hand, by fully inputting the sawtooth wave as the scanning signal in the X direction, horizontal scanning, which is the same as normal 1'' scanning, is executed.

Next, a method of separating the brightness signal shown in FIG. 5(3) from the signal scanned by the above method using the signal separation circuit 20 (shown in FIGS. 3 and 4) will be described.

In FIG. 4, a signal 161-J whose waveform has been shaped by the filter circuit 14 is input to the sample and hold circuit 20-1, where it is sampled in synchronization with the square wave of the vertical scanning signal from the vertical scanning signal generator 11. Hold. This sampled and held signal 1-1: A/D converter 20-2
The converted digital signal is then separated into 11 signals by a switch circuit 20-3. The sample hold circuit 20-1 and the A/D converter 2
0-2, by controlling the switch circuit 20-3 based on the timing of the square wave, it is possible to easily change the brightness signal according to the scanning position.

The digital signals separated by the switch circuit 20-3 are sequentially held in the latch circuits 20-4a and 20-4b, and these signals correspond to (a) and (b) in FIG. 5(3). It becomes a brightness signal. By D/A converting these signals through the iD/A conversion circuits 20-5a and 20-5bi, they become brightness signals that can be observed with an oscilloscope (not shown) and input into a frame memory, etc. It can be processed as shown in Figure 5 (3) (
By observing the correspondence between the signals a) and (b), it is possible to understand the state of the slider's levitation in multiple dimensions.

Furthermore, in the latch circuits 20-4a and 20-4b, comparison circuits 2O-6a and 20-6a,
By making a determination using 2O-6b, it is possible to detect the peak positions of the bright and dark areas of the bright explosion signal. Although not shown in the figure, it is also possible to detect the portion with the largest differential feed change, and from this it is also possible to detect the edge of the slider. By counting the number of tallocks of the square wave and the timing at which the peak position and edge position occur, the V O+ v shown in Fig. 5 (2) (a) and (b) is calculated.
, IV, lv, #t■,', and thereby (1) the respective minimum gaps can be determined using the cost. These operations are performed by the data processing circuit 15.

As explained above, according to the present invention, it is possible to clamp the change in interference fringes f caused by a normal optical system in real time over multiple dimensions. It is possible to easily measure the average gap interval of minute gaps and the time-varying amount of clearance, and furthermore, the measurement accuracy can be improved kfd.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams illustrating the entire principle of the conventional optical measurement method for minute gaps, Figure 3 is a block diagram of an embodiment of the multidimensional measurement method for minute gaps according to the present invention, and Figure 4 is a block diagram of the signal separation circuit in Fig. 3, Figs. 5 (1) to (3) are diagrams explaining the relationship between the interference fringe image formed on the photoelectric conversion unit, the brightness signal, and the gap, and Fig. 6 (1) and (2) are explanatory diagrams of two-dimensional simultaneous scanning. 2... Disc, 3... Slider, 8... Photoelectric conversion unit, 10... Horizontal scanning signal oscillator, 11... Vertical scanning signal oscillator, 15... Data processing circuit, 20...
...Signal separation circuit. 1 year old 3m 24 countries [1] 0 (3) 5 years old Fungus

Claims (1)

[Claims] A minute gap between the objects to be measured is generated as interference fringes by optical interference method, and an image is formed on the interference ring gold photoelectric conversion section and scanned to detect the bright part of the interference fringes or the bones. In the method of optically measuring a minute gap from an output signal corresponding to the brightness of a part, the interference fringes are scanned in an arbitrary direction and period over multiple dimensions, and a multidimensional brightness signal is separated from this scanning signal, A micro gap multidimensional measurement method characterized in that this signal is processed to measure multidimensional gaps between objects to be measured.