JPS63149508A - Apparatus for measuring head levitation gap - Google Patents

Abstract

PURPOSE:To measure the levitation gap of a head in a short time by a simple constitution, by a method wherein a monochromatic filter provided with an optically transparent window is interposed in the illumination system of a metal microscope and a spectroscope is arranged to the image forming position of an image forming system to irradiate a photodetector. CONSTITUTION:The levitation state of the floatable head 21 levitating on a rotary disc 20 is illuminated by a white light source 1 through an objective lens 3 and a reflected image is observed through an eyepiece 5. The formed image passing through an image forming lens 4 is spectrally diffracted by the spectral prism 8 arranged at the image forming position thereof to be again formed into an image by a converging lens 10 and said image is detected by a unidimensional photodetector 11 to detect light spectrum intensity distribution. A monchromatic filter having an optical transparent window provided to a part thereof is used in an illumination system and the image thereof is projected on the head 21 to subject a whole image visually observed to monochromatic illumination and the density of monochromatic interference is observed corresponding to the gap between head 21 and the disc 20 and only an objective part is illuminated by a while spot. Therefore, a measuring place is easily confirmed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a device for measuring the flying clearance of a floating head for a magnetic disk.

(Prior art and its problems) Conventionally, in order to check the flying clearance of a floating head for a magnetic disk, the floating head is floated on a transparent glass disk, etc., and the interference color due to white interference is observed. (C, Lin and R, P,
5ullivan, “An Application
of'Seo teLight Interreromet
ry in Th1n Film Measureme
nts”lBM J, RES, Develop, Vol.
1B, p. 269 (1972)), this method is simple and quick, as it evaluates the flying clearance by observing the flying state of the floating head using an ordinary microscope and comparing it with a standard color-gap composition table prepared separately. Although it is possible to measure time, it has the disadvantage that color discrimination accuracy decreases in areas where the gap is 0.3 μm or less. For this reason, an optical interference intensity measurement method using monochromatic light is used in the low flying clearance region (J
, M. Pleischer and C. Lin, In.
rrared La5er Interf'erome
ter f'or Measuring Air-B
earing 5eparat ton''IBM J,
Rcs, Devcrop, Vol.B, p 529(1
974) ).

This means that the optical interference intensity at a single wavelength (λ) is S (λ)−
S, +32-s, -・S2xeos(4π〒)...(
1) However, SL -3o A method of calculating the floating gap from the intensity of light using
A method is used to calculate the flying clearance by using a variable wavelength light source (such as a monochromator) to find the wavelength at which the light intensity is maximum or minimum (Maruyama ``Spacing measurement device using wavelength scanning method''). ” Showa 60
National Conference of the Communications Society of Japan No. 058.1985).

However, as a result of using a single wavelength in the former method, there is a region where the measurement sensitivity is extremely reduced (dmmλ/4.m; a positive integer) periodically with respect to the size of the gap, and it is generally not suitable for use as a measuring instrument. The latter had the drawback of requiring time ranging from tens of seconds to several minutes, as the latter requires mechanical movement of a diffraction grating to scan wavelengths. For this reason, it has been impossible to dynamically observe, for example, when the circumferential speed changes continuously, such as when starting or stopping, and the flying clearance of the floating head also changes accordingly. Furthermore, in any case, in order to observe the setting state of the head, a separate microscope is required to observe the flying state using white interference, which has the drawback that the measurement system becomes heavy and large. Normally, in floating measurements, a floating head is placed below a rotating disk placed horizontally, and the observation is made from above, resulting in an overhanging measurement system. In order to achieve this increase, weight reduction is necessary, but this has been difficult with conventional single-wavelength interference methods.

SUMMARY OF THE INVENTION An object of the present invention is to provide a head flying clearance measuring device which has a compact configuration and is capable of determining M1 of a minute flying clearance of a floating head with high precision and in a short time.

(Means for Solving the Problems) In order to achieve the above object, the present invention disposes a floating head on one side of a rotating transparent disk, and places a floating head in close proximity to the other side of the disk. In a head floating gap measuring device equipped with a microscope, a monochromatic filter provided with an optically transparent window is interposed in a part of the illumination system of the metallurgical microscope, and is disposed in the imaging system of the metallurgical microscope. A spectrometer is placed at an imaging position where a part of the light separated by one spectrometer is imaged,
It is characterized by providing a one-dimensional light receiving element that receives light from the spectroscope.

(Function) According to the above configuration, the light passes through the window of the monochromatic filter disposed in the illumination system to spot illuminate a part of the floating head, and the remaining light passes through the monochromatic filter and similarly illuminates the floating head. By illuminating the entire area, the entire image of the floating head can be observed through the eyepiece. Further, by separating the light using a spectrometer disposed at the imaging position of the imaging system, the light receiving element can be irradiated with a monochromatic light.

(Example) Object lens, 4 is an imaging lens, 5 is an eyepiece lens, 6 is a spectroscopic prism, 7 is a support barrel, 8 is a spectroscopic prism, 9 is an aperture, 10 is a converging lens, 11 is a one-dimensional light receiving element, 1
2 is a condensing lens, 13 is a monochromatic filter, 14 is a converging lens, 20 is a transparent disk rotated by a drive shaft, 21
2 shows a floating head disposed under the disk 20, and 22 a gimbal spring that supports the floating head. The above-mentioned components 1 to 7 constitute an ordinary metallurgical microscope, and the microscope is arranged at a position facing the floating head on the upper surface side of the disk. The spectroscopic prism 8 is arranged at an imaging position of the imaging system of the metallurgical microscope set outside the aperture 9, and is arranged in a -dimensional manner. Further, the monochromatic filter 13 is disposed in a part between the condenser lens 12 and the convergent lens 14, which are the illumination system of the metallurgical microscope.

The floating state of the floating head 21 floating on the rotating disk 20 is illuminated by the white light source 1 through the objective lens 3 and the disk 20, and the reflected image can be observed with the eyepiece 5, and an image is formed through the imaging lens 4. imaged at the location. After the image is separated by a spectroscopic prism 8 placed at the image forming position, it is again imaged by a converging lens 10 and sent to a -dimensional light receiving element 11.
Detected in Naturally, the positional relationship between the spectroscopic prism 8 and the converging lens 10 may be reversed.

In a normal illumination system, the entire field of view is uniformly illuminated, so it is necessary to illuminate only the target area with white light. Usually, a field stop is provided in the illumination system for this purpose, but using a field stop makes it impossible to observe the entire object. Therefore, in the present invention, a monochromatic filter (for example, a 550 nm filter) partially provided with an optically transparent window (for example, a hole)
By using a transmission filter 13 to illuminate only the position corresponding to the window with white light, it is possible to perform spectroscopy while visually observing the entire image. That is, the monochromatic filter 13
By projecting the image onto the floating head 21, which is the object to be observed, the entire visually observed image is illuminated in a monochromatic color, and the shading of the monochromatic interference corresponds to the gap between the floating head 21 and the disk 21. Since only the area to be observed and targeted is illuminated with a white spot, it is easy to confirm the measurement location. As shown in Figure 2, the spectroscopic results show a strong monochromatic spectral part (550 nm in this example), but since this is the only wavelength that can be predicted, it can be removed from the measurement results and the problem can be solved. do not have. Monochrome filter 13
A common multilayer dielectric film is sufficient.

The size of the spectroscopic prism 8 is, for example, a total of 111
If one area is 0.01 mm and the microscope magnification is 100 times, the size of the real image will be 1 mm.It only needs to be a little larger than that, for example about 1.5 mm, and the objective lens 3
The weight is negligible compared to the weight of the supporting lens barrel 7. The light that passes through the aperture 9, which has an opening large enough to block stray light generated within the support barrel 7, is emitted from the white light source 1, and a specific wavelength (λ-d) is transmitted to the head slider surface and the transparent disc. Because it is emphasized by multiple interference with the 20th plane,
This results in the same spectral intensity distribution as in equation (1).

That is, since the wavelength λ takes an extreme value in the relationship λ-4d/m, the flying clearance can be evaluated by finding the wavelength at which the spectral intensity at the target position is maximum or minimum.

When light passes through the spectroscopic prism 8, it is spatially separated by the wavelength that passes through the spectroscopic prism 8, so when this is received by the -dimensional light receiving element 11, the spectral intensity distribution of the light is electrically detected at once. can. - Although a photodiode array or one-dimensional COD can be used as the dimensional light receiving element 11,
For example, a general 512 element C with a clock of 4 MHz
When OD is used, the spectral intensity distribution can be measured at a repetition rate of 8 KHz, and it is extremely easy to find the maximum or minimum wavelength. If the measurement wavelength range at this time is, for example, 0.25 μm to 0°75 μm, the minimum observable gap range is 0°0625 μm, the resolution is 5 angstroms, and the accuracy is sufficiently high.

Since one measurement can be performed in an extremely short time, this method not only allows dynamic measurements such as starting and stopping, but also clearance fluctuations during one rotation, and is also suitable for research on the effects of disk vibration. It can be used in a wide range of applications.

As mentioned above, in the present invention, the illumination system and objective eyepiece system have the same configuration as the microscope optical system used in conventional white light interferometry, so it is of course possible to visually observe the entire floating head. No new optical system is required to check head settings. Therefore, since there is almost no increase in weight, no new vibration countermeasures are required.

Although the spectroscopic prism 8 and the converging lens 10 have been explained here, instead of these, for example, as shown in FIG.
A converging prism 30 having both a prism function and a lens function may be used. It is well known that such prisms can be easily obtained by injection molding of plastics. In addition, when using a prism, the transmittance of the material may be poor in the extremely short wavelength or long wavelength region, but in that case, a diffraction grating with flat spectral characteristics is used, which also serves as light condensing, as shown in Figure 4. Of course, a concave diffraction grating 40 that can be used may also be used. In this case, a large diffraction grating is required to improve the spectral efficiency, so the M1 constant system becomes somewhat large, but the structure is simple.

In addition, although we have explained here that measurement is performed by subtracting the spectrum from the monochromatic filter from the data, this subtraction may be performed computationally or electrically.
Furthermore, it is of course possible to insert a complementary color filter to the above-mentioned monochromatic filter into the spectroscopic system for correction.

(Effects of the Invention) As explained above, according to the present invention, a floating head is disposed on one surface of a rotating transparent disk, and a metallurgical microscope is provided close to the other surface of the disk. In the head floating gap measuring device, a monochromatic filter provided with an optically transparent window is interposed in a part of the illumination system of the metallurgical microscope, and a monochromatic filter provided with an optically transparent window is provided in a part of the illumination system of the metallurgical microscope. A second spectrometer is placed at the imaging position where part of the light separated by the spectrometer is imaged, and a one-dimensional light-receiving element is provided to receive the light from the second spectrometer. - A high-precision measurement system can be configured to be compact and lightweight, and there is no need to worry about deterioration in accuracy due to vibration in the measurement system, which was a problem when using conventional monochromatic light sources. In addition, white interference allJ
Since the optical system and optical system are shared, it has the advantage of being easy to operate and can be constructed at low cost.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the principle of the floating gap measuring device according to the present invention, Figure 2 is an example of the electrical output of the measurement results, Figure 3 is another diagram of the configuration of the spectroscopic section when a converging prism is used, and Figure 4 is A configuration diagram of a spectroscopic section when using a concave diffraction grating is shown. DESCRIPTION OF SYMBOLS 1... White light source, 2... Half mirror 13... Objective lens, 4... Imaging lens, 5... Eyepiece lens,
6... Spectroscopic prism, 7... Support barrel, 8... Spectroscopic prism, 9... Aperture, 10... Converging lens, 11... -dimensional light receiving element, 12... Condensing light Lens, 13... Monochromatic filter, 14... Convergent lens, 2
0... Transparent disk, 21... Floating head, 30...
Converging prism, 40... concave diffraction grating, arrows indicate the progress of light.

Claims (1)

[Claims] In a head floating gap measuring device that includes a floating head disposed on one surface of a rotating transparent disk and a metallurgical microscope provided in close proximity to the other surface of the disk, a part of the illumination system of the metallurgical microscope is provided. A monochromatic filter provided with an optically transparent window is interposed, and a part of the light separated by the first spectrometer disposed in the imaging system of the metallurgical microscope is formed at an imaging position. 1. A head floating clearance measuring device, characterized in that a second spectrometer is disposed, and a one-dimensional light receiving element for receiving light from the second spectrometer is provided.