JPS6144307A - Minute gap measuring method - Google Patents

Abstract

PURPOSE:To facilitate the measurement of dynamic spacing and to perform the highly accurate measurement, by picking up interference colors yielded by the projection of white light on a surface to be measured by a TV camera, and measuring the gap between an optical head and the surface to be measured based on the ratios of the output signals R (red), G (green) and B (blue). CONSTITUTION:White light from a light source 4 is inputted in an optical head 1 from the directly upper side through a half mirror 5. The inputted white light 2 is reflected by the lower surface of the optical head 1 and the upper surface of a disk 3 comprising a magnetic disk and the like, and the reflected light beams 2a and 2b are obtained. Fringes of interference colors are yielded on the surface of the optical head 1 based on the interference of both light beams. The interference colors are picked up by a color TV camera 6. The output signals of R, G, and B from the camera are accommodated in frame buffers 7a-7c. The outputs of the frame buffers 7a-7c are compared with a color operating table by an operation control device 8. The digital spacing values are outputted to a display or a hard copy device.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for measuring a minute gap, particularly when measuring a minute gap between a magnetic disk and a magnetic head due to various factors, such as in a floppy disk device, a hard disk device, etc. The present invention relates to a method for measuring the minute gap in a magnetic disk drive device that is displaced by a distance.

[Background of the invention]

In a magnetic disk response device having a floating magnetic head, the magnetic head floats with a small gap above a magnetic disk rotating at high speed. Furthermore, in a floppy disk drive, a magnetic head floats or tilts with a small gap relative to a magnetic disk rotating at high speed. The gap between the magnetic disk and the magnetic head changes from moment to moment, and has a large effect on electromagnetic conversion characteristics. Particularly in recent years, with the increase in recording density, it has become necessary to stably maintain the gap between the magnetic disk and magnetic head in the sub-micron range. A measurement method is needed.

Therefore, the present inventors placed an optical head 1 made of optical glass on a magnetic disk 3, as shown in FIG. Reflected light 2'a reflected from the upper surface of the disk 3,
We invented the measurement of interference fringes due to interference of 2'b.

In this case, the gap d between the optical head 1 and the magnetic disk 3 is determined by the intensity of the interference light, and n is the interference order (n=
0*L2,...), the interference light intensity is d
It is minimum when =nλ/2, and maximum when d=(2n+1)λ/4. However, the state in which fl13eA d can be measured is only when d is an integer multiple of λ/4, and therefore the incident light 2
It has been difficult to perform dynamic spacing measurements because it is necessary to find the wavelength at which the interference light is at its maximum or minimum by changing the wavelength of '. Furthermore, for an extremely small amount of time 11
In order to measure d, it is necessary to reduce the wavelength of the incident light 2' to produce bright and dark interference fringes, but since it is difficult to measure if the wavelength is below visible light, the minimum measurable gap d is was limited to about 0.1 μm.

[Purpose of the invention]

It is an object of the present invention to provide a minute gap measuring method that allows single-singing measurement to be extremely easy and highly accurate.

Another object of the present invention is that the visual error of the measurer (
The purpose of the present invention is to provide a method for measuring minute gaps that is free from individual differences (individual differences) and that allows quick measurement processing.

[Summary of the invention]

The above-mentioned object of the present invention is to image the interference color generated by projecting white light onto a surface to be measured such as a disk through an optical head with a television camera, and to use the optical This is accomplished by measuring the gap between the head and the surface to be measured.

[Embodiments of the invention]

FIG. 1 shows an outline of the definition device of the present invention. Reference numeral 1 denotes an optical head made of a transparent material, which is made of optical glass, plastic, etc., and mounted on a carriage for mounting the magnetic head of a magnetic disk drive. Installed in place of the L air head. It is preferable that this optical head 2 has a shape similar to the shape of the above-mentioned magnetic head for mounting, and although it is a+abbreviated in the illustration, it is made to match the shape of a floating head, a floppy head, etc., and is an oral tradition. It is sufficient to have at least a small number of such optical parts, and is attached to the carriage by a known gimbal spring so that it can be moved along the radial direction of the disk 3.

Reference numeral 4 denotes a white light source, and the white light 2 from the light source is incident from directly above the optical head l via the -7 mirror 5. The incident white light 2 is reflected by the lower surface of the optical head 1 and the upper surface of the disk 3 made of a magnetic disk or a simulated magnetic disk, resulting in reflected light 2a.

2b, and as a result of interference between the two, the surface of the optical head 1 is
For example, interference color fringes as shown in FIG. 2 are generated. (In one example, 1a is black, 1b is gray, IC is white, 1d is yellow, and 1e is red. (The above interference colors are photographed by a color television camera 6, and the R (red), G (green), and B (black) output signals of the camera 6 are used to record the interference colors. are stored in frame buffers 7a, 7b, and 7c as
The outputs of ~7C are compared and calculated using a color calculation table prepared in advance, and the spacing values are output digitally to a display or hard copy device.

In other words, the color reproduction of a TV image is performed by combining the R, G, and B signals, and if we do not consider the brightness of the R, G, and B colors, the interference color is the ratio of the R, G, and B signals. You can decide.

Therefore, by determining the relationship between the signal ratios of 11Ad and R, G, and B between the optical head 1 and the disk 3 in advance, the actual value can be calculated from the ratio of the imaged interference color output signals of 凇, G, and B. The gap d is determined by the calculation control circuit 8.

Figures 3 and 4 illustrate a technique for calibrating the relationship between the ratio of the R, G, and B output signals and the inter-id relationship. If a lens 10 is placed on the optical flat 9 and white light is incident from above the lens 10, Newton's ring interference color fringes will be observed as shown in FIG. The distance between the optical flat 9 and the lens 10 at a distance l from the center of the Newton ring [id is the lens 1
If the radius of curvature of 0 is R, then it is expressed as d = l''/2'm. Therefore, when the interference color fringes shown in Figure 5 are imaged on a color television, the radius of curvature of Newton's ring is R at a point spaced by a length l from the center of the Newton's ring. , G, and B signals can be made to correspond to the gap d, and the gap lid can be determined by the ratio of the color components.

Here, the R, G, and B output signals 6a, 6b, and 6c of the color television camera 6 have three different wavelengths λF and λG.

It is a value obtained by correcting the intensity of light of λ1 by human visibility with respect to λ凰, λG, and λliao. Therefore, the wavelength λ凰, λG
.

The light of λ1 is emitted by the color television camera 6, for example.

By correcting the ratio of Ko and Km, the wavelength λ is determined.

The ratio of the light intensity of λO2λB is R/Kl : G/KG
: B/ is set to 1. (However, 几, G, B are 几・
G. Represents, for example, a digital or analog quantity of the B output signal. ) In addition, Fig. 5 shows a coordinate system with the optical intensities Ii, Io, and Io of the wavelengths λF, λG, and λ1 as axes, respectively.
Vector C represents interference color, and the length of vector C represents brightness, and the direction of AC represents saturation and hue.

For Ir, Ig, 11), the ratio of light intensities of beam length λTatsumi, λG, and λ3 is (1:O:0), (0:1:O), and (0
:O:1), and point C is pect/I
/C is the point where it intersects with the triangle formed by I, , Ig, and Ib, and represents a hue of 1 saturation, and FIG. 6 shows such Ir.

It represents a colored triangle formed by Ig and Ib.

In Figure 6, W is expressed as an achromatic color ft by the imaginary center of the triangle,
The saturation is close to W, and the point representing the hue C' is a half-line drawn from point W in the direction of C, at vertices Ir and I.
It is expressed by the point that intersects the triangle formed by g and Ib.

Therefore, Ir= (1,O,O), Ig= (0,1,
O), Ib = (0, 0, 1), the point C representing the saturation and hue of the color (interference color) in the G, B output signals of the color television 6 is given by It turns out. Note that the point W representing an achromatic color is W=(1/3.l/3, 1/3).

On the other hand, the point C' representing the hue is the above R', G', B
' depends on the size of , and is given by . However, it is said that.

That is, for the interference color photographed by the color television camera 6, the hue C' etc. are quantitatively calculated and detected by the above formula, and this hue C' etc. is determined in advance by the gap d shown in FIG. By comparing and calculating the hue component values calibrated correspondingly to each other using a calculation table, etc., the gap d between the optical head 1 and the disk 3 can be reliably, easily, and quickly determined using interference color. 3, it becomes possible to measure the dynamic spacing between the optical heads 1. In addition, since the white light 2 having a continuous wavelength of visible light is the incident light, it is possible to measure minute gaps, l1fl l! of about 0.03 μm. ja
It was confirmed that it was possible to measure d. Furthermore, compared to when a measurer visually compares and visually observes interference colors using a reference color scale, it is possible to perform precise measurements without any visual errors.

In addition, in the examples, the present invention will be described as a magnetic disk device.
Although an application example has been shown, it goes without saying that the spirit of the present invention can be applied to various types of ware in a good manner.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to easily and highly accurately measure the dynamic spacing needle side, and also
This method has great industrial advantages, such as the fact that there are no individual differences in the process and speedy processing is possible.

[Brief explanation of the drawing]

Figures 1 to 6 relate to embodiments of the present invention, with Figure 1 being a schematic diagram showing one example of a measuring device, Figure 2 being an explanatory diagram showing interference colors on an optical head, and Figure 3 being an optical head. An explanatory diagram showing the relationship between the tical flat and the lens, Fig. 4 is an explanatory diagram showing Newton rings on the lens in Fig. 3, Fig. 5 is an explanatory diagram showing the color companding system, and Fig. 6 is an explanatory diagram showing the color triangle. FIG. 7 is an explanatory diagram showing a measuring method at a preliminary stage leading to the creation of the present invention. DESCRIPTION OF SYMBOLS 1... Optical head, 2... White (input) light, 3... Disc, 6... Color television camera, 7a. 7b, 7c...7 reme x, fa, 8...
...Arithmetic control device. Fig. 1 Fig. 3 Fig. 4 Fig. 5 G Fig. 7 Procedural amendment Lu (self 0R1,) October 22, 1980

Claims (2)

[Claims] (1) Interference between reflected light from the optical head and the surface to be measured occurs when an optical head made of a transparent material is placed on a flat surface to be measured and white light input is projected onto the surface to be measured via the optical head. 1. A method for measuring a minute gap, characterized in that the interference color is imaged by a television camera, and the gap between an optical head and a surface to be measured is measured from the ratio of R, G, and B output signals of the television camera. (2) The surface to be measured is the surface of a magnetic disk, and the optical head is attached via a gimbal spring to a carriage that is transported along the radial direction of the disk, and has a shape that simulates the shape of the mounting magnetic head. The micro gap measuring method according to claim (1), characterized in that a micro gap is formed.