JPS61191907A - Head lifting amount measuring apparatus - Google Patents

Abstract

PURPOSE:To measure the drift of a head simply and accurately, by projecting light with a specified wavelength to a head arranged at a specified position on a disc to form an interference fringe, corresponding to which the light signal thereof is converted into an electrical signal. CONSTITUTION:A head 9 is arranged at a specified position of a flat transparent disc 1. This head 9 drifts according to the rotational speed of the disc 1 upon the determination of the arranging position thereof. Then, light with a specified wavelength is projected to the head 9 through the disc 1 from an interference fringe formation means (light source 11) and (microscope 12) to form an interference fringe. The light signal from the interference fringe formation means is converted into an electrical signal by a photoelectric conversion means (TV camera 16) to be shown on a display means (monitor TV17). According to the output of the photoelectric conversion means, a signal per unit scanning period is extracted by an extraction means (1H extractor 18) and data thereof are memorized into a computer 22. Based on the data, a computation is done to determine the lifting amount of the head 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a head flying height measuring device suitable for use in measuring the flying clearance of a flying head used in a hard disk or the like.

[Summary of the invention]

The present invention is a head flying height measurement device for measuring the flying clearance of a flying head used for a hard disk, etc., in which a head is placed at a predetermined position on a flat, transparent disk so as to fly according to the rotational speed of the disk. death,
Light of a predetermined wavelength is projected onto this head via a disk to form interference fringes, and the optical signal corresponding to the interference fringes is converted into an electrical signal and displayed. By extracting and calculating, the flying clearance of the flying head can be measured using a simple device and operation.

[Conventional technology]

The following methods have been proposed for devices that measure the flying clearance of a flying head in response to changes in the amount of interference light between the head and an optical flat (a flat, transparent disk). .

The first method is to determine the flying gap by comparing a color scale with a color fringe pattern of white light that is generated in correspondence with the flying gap between the rotating optical flat and the head. The second method is to make white light into monochromatic light using a filter, monochromator, laser, or emitting diode, and to make dark stripes with a gap of 172 cm of the wavelength, in order to cover the shortcomings of the first method, which will be described later. This method uses calculations to extrapolate the distance between stripes and the shape of the head to measure the flying gap at an arbitrary point.

The third method is that the interference fringes caused by the monochromatic light generated in the second method described above do not have discrete dark spots, but are analog quantities in which the amount of light changes continuously based on a sine wave. ,
When this analog quantity is obtained using a photodiode, photomultiplier, line sensor, etc., the flying gap is determined from a theoretical formula for interference light. Furthermore, a fourth method is based on the laser Doppler method.

[Problem that the invention seeks to solve]

However, in the case of the first method described above, it requires trained human eyes, has poor accuracy, and has the disadvantage that measurement is impossible because no color appears in gaps of 0325 μm or less. In addition, in the case of the second method, it is necessary to measure the head shape in advance, and it is difficult to apply when only one stripe appears, and automatic measurement requires a huge amount of computer processing and hardware for image processing etc. The drawback was that it required clothing.

Further, in the case of the third method, there is a drawback that it is very difficult to select an arbitrary point on the image seen with a microscope or a television camera, that is, it is very difficult to position the head and the detector. Furthermore, in the case of the fourth method, although it is very accurate, absolute measurement is impossible, and it is difficult to determine where the head is relative to the disk.
The drawback was that the absolute amount could not be determined.

The present invention has been made in view of the above problems, and an object thereof is to provide a head flying height measuring device that can easily and reliably measure the flying height of a head both in terms of device and operation.

[Means for solving problems]

The head flying height measuring device according to the present invention includes a flat and transparent disk (1), a drive control means (21, +3) for controlling the rotation of this disk, and a drive control means (21, +3) arranged at a predetermined position on the disk to rotate the disk. A head (9) configured to float according to the speed, interference fringe forming means (11), (12) that projects light of a predetermined wavelength onto the head via the disk to form interference fringes, and this interference Photoelectric conversion means (1) for converting the optical signal from the stripe forming means into an electric signal
6) and display means (
I7), an extraction means (18) for extracting a signal per unit scanning period from the output of the photoelectric conversion means, and a computer (22) for storing and calculating the output of this extraction means and controlling the drive control means. It is configured to have the following.

[Effect]

Head (9) in place on flat transparent disk (1)
Place. Once the position of the head (9) is determined, the head (9) flies in response to the rotational speed of the disk (1). Then, the interference fringe forming hand￥It(1
1) and (12), light of a predetermined wavelength is transferred to a disk (
1) onto the head (9) to form interference fringes. The optical signals from the interference fringe forming means (11) (12) are converted into electrical signals by the photoelectric conversion means (16) and displayed by the display means (17).

Also, the extraction means (1 day) from the output of the photoelectric conversion means (16)
A signal per unit scanning period is extracted, various data are stored in a computer (22), and calculations are performed based on this data to determine the flying height of the head (9).

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail based on FIGS. 1 to 3.

Figure 1 shows the circuit configuration of this embodiment. In the figure, (1) is a flat and transparent disk, (2) is a motor for rotating the disk (1), and (3) is a motor ( 2)
(4) is a detector for detecting the rotation of the motor (2), and (5) is a tachometer to which the output of the detector (4) is supplied. (6) is a fixed table, (7) is a slider that slides on the table (6), (8)
is a head support plate fixed to the negative side of the slider (7), (
9) is a head; αΦ is an elastic member having one end fixed to the head support plate (8) and the other end attached to the head (9); It is supported and loaded. In addition, the head (9
) is positioned at a predetermined position on the disk (1), it floats above the disk (1) against the elastic force of the elastic member αl due to the inflow of air according to the rotational speed of the disk (1).

(11) is a light source that generates light of a predetermined wavelength (μm), (1
2) is a half mirror (
13) and (14) to the head (9) side. The light source (11) passed through this microscope (12)
) is projected onto the head (9) via the disk (1), so-called interference fringes will occur on the head (9) if the head (9) is floating relative to the disk (11). .

Also, the microscope 1 near the light source (11)! A filter (15) of a predetermined color is inserted in the optical path of (12), thereby converting the white light into monochromatic light.

Further, a television camera (16) as photoelectric conversion means is provided on the side opposite to the head side of the microscope (12), and reflected light from the head (9) is supplied via a half mirror (14). (17) is a monitor television that displays the video signal from the television camera (16), and (18) is a unit scanning period, for example, an IH (
H is an IH cutter as an extraction means for extracting a signal per horizontal scanning period), and this IH cutter generates a cutout marker on the monitor television (17), and the monitor television (17) that the cutout marker points to. A signal corresponding to the IH-equivalent portion of the image projected on the imager (F) is immediately obtained at the output side of the IH cutter (18). The cutting marker of this IH cutter (18) can be adjusted with an adjustment knob (not shown) so that it can be moved up and down on the screen of the monitor television (17).

(19) is a divider to which the output of the IH cutter (18) and the output of the photodetector (20) provided in relation to the half mirror (13) are supplied; (20) detects the flickering of the light from the light source (11), converts the reference light into an electrical signal, and supplies it to the divider (19), which in turn connects the IH cutter (18) to the divider (19).
The output of the light source (by being subtracted from the IH multiplied signal)
11) The fluctuation of light is canceled. (21) is an A/D converter that converts the output signal from the divider (21) from an analog signal to a digital signal; (22) is a computer that includes a central processing unit, memory, etc. (not shown); This computer (22) stores various information during measurement and performs calculations based on the stored information to determine the flying height of the head and to control the rotation controller (3). (23) is a printer for printing out measurement results.

Next, the operation of the circuit shown in FIG. 1 will be explained with reference to FIGS. 2 and 3.

First, the computer (22) controls the rotation controller (3) to set the motor (2) to the speed to be measured, and in conjunction with this, the disk (11) is rotated.Next, the slider (7) is moved. The head (9) is placed on the disk (1) which is rotating.The head (9) is also generated from the light 1 (11) and sent through the half mirrors (13), (14) and the disk (1). 9). At this time, if the head (9) is floating above the disk (11) as shown in Figure 2 C, interference fringes will be generated on the head (9). These interference fringes are captured by a television camera. (16) and display it on the monitor TV (17). Then, while checking the interference fringes on the monitor TV (17), set an arbitrary measurement point with the IH cutter (18) and measure the IH portion of the point you want to measure. At this time, an IH cutting marker is displayed on the monitor TV (17) for the measurement location as shown in Figure 2B.In addition, in Figure 2B, the shaded area is represents the dark part of light and darkness.Also,
The IH video signal extracted by the IH cutter (18) is expressed as an analog quantity whose light quantity changes continuously based on a sine wave, as shown in FIG. 2A.

The output signal from the IH cutter (1B) is sent to the divider (19)
The output signal is supplied to the IH cutter (18) and divided by the detection signal from the photodetector (20) to cancel the light fluctuation of the light source (11) included in the output signal of the IH cutter (18). This signal is A
The signal is converted into a digital signal by the /D converter (21) and stored in the memory of the computer (22) as information on the amount of measured light. Further, the rotational speed of the motor (2) at this time is read out by the tachometer (5) via the detector (4) and stored in the memory of the computer (22).

Next, the computer (22) controls the rotation controller (3) to change the rotation speed of the motor (2), as shown in FIG.
The maximum (+ax) and minimum (+ax) values of the light intensity closest to the measurement point of
sin) values and store them in the memory of the computer (22). In addition, the rotation speed of the motor (2) is further slowed down, and the number of times the maximum and minimum values of the light amount change are repeated until the color stops appearing is determined, and this is stored in the memory of the computer (22) as the fringe order. Remember.

Then, the light intensity at the measurement location, the maximum value and minimum value of the change in light intensity,
The fringe order is calculated by the computer (22) according to the following formula, and the calculation result is used as the floating gap (levitating 11) at the rotational speed indicated by the tachometer (5) at that time.

Here, h is the flying height of the head (μ1m), λ is the wavelength of the light source (μor), m is the maximum value of the light intensity change, the number of repetitions of the minimum value (fringe order), ■ is the light intensity at the measurement point, I
max is the maximum amount of light closest to the measurement location, and Ia+in is the minimum amount of light closest to the measurement location.

In addition, Figure 3 shows the change in brightness (change in light amount) when the flying height of the head is changed with the measurement location fixed at a certain point, and in this Figure 3, the flying height ho of the head is determined. In this case, the fringe order m can be determined by substituting 3 into the above equation.

After calculating the flying height of the head for the measurement location in this manner, the above operation may be repeated by changing the rotation speed of the motor (2).

In the above embodiment, a color television camera may be used as the television camera (16), and a color monitor television may be used as the monitor television (17).

〔Effect of the invention〕

As described above, according to the present invention, the signal per unit scanning period of the image displayed on the monitor television is extracted and used as the measurement signal, so the image seen with the eye and the measurement point match exactly, and the operation is easy. be.

Furthermore, since the television camera serving as the photoelectric conversion means also serves to detect the measurement signal, the configuration of the device is very simple and the manufacturing cost is low. Furthermore, if the system has an optical system, it can be easily applied to conventional equipment without major modification by simply adding a television camera, monitor television, IH cutter, etc. Furthermore, if a color television camera is used as the television camera (16) and a color monitor television is used as the monitor television (17), the above-mentioned first conventional method can be used in combination.
It can also be used to determine the fringe order.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing one embodiment of the present invention, and FIGS. 2 and 3 are diagrams for explaining the operation of FIG. 1. (1) is a disk, (2) is a motor, (3) is a rotation controller, (5) is a tachometer, (9) is a head, (11) is a light source, (12) is a microscope, and (16) is a television camera. ,(
17) is a monitor TV, (Engineer 8) is an IH cutter, (1
9) is a divider, (20) is a photodetector, (21) is an A/D
The converter (22) is a computer.

Claims (1)

[Scope of Claims] A flat and transparent disk, a drive control means for controlling the rotation of the disk, and a head arranged at a predetermined position on the disk so as to fly according to the rotational speed of the disk. , an interference fringe forming means that projects light of a predetermined wavelength onto the head via the disk to form interference fringes, a photoelectric conversion means that converts an optical signal from the interference fringe forming means into an electrical signal, and the photoelectric conversion means. a display means for displaying the output of the photoelectric conversion means, an extraction means for extracting a signal per unit scanning period from the output of the photoelectric conversion means, and a computer for storing and calculating the output of the extraction means and controlling the drive control means. A head flying height measuring device comprising: