JPH04166705A - Minute-interval measuring method - Google Patents

Abstract

PURPOSE:To measure a minute interval between objects simply by casting light on the light scattering surface of the object which is located at a position separated from a mirror surface by a minute distance, condensing the reflected light with a lens, and projecting the light on a detecting element. CONSTITUTION:An object 13 having the light scattering surface is located at a distance of a height (h) from a mirror surface 11. The object 13 has an irregularly reflecting surface 13a in a plane which is intersected with the mirror surface. When light is emitted from a light source 15, the light is irregularly reflected from the irregularly reflecting surface 13a. When the light is observed from the side of the light source 15 with respect to the reflecting surface 13a, the reflecting surface 13a and a mirror image 13a' are brightly observed, and the part between the surface 13a and the surface 13a' is darkly observed. The image is picked up with a lens 17 and projected and focused on a line sensor 19. Then, the image comprising a bright part EF, a dark part FG and a bright part GH is projected. Therefore, the length of the dark part FG can be obtained at the error of about one picture element by detecting the edge part of the output on the line sensor 19.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for measuring minute intervals that can be applied to measuring the flying height of a magnetic head.

Follow the speed! 14 In magneto-optical recording, especially magnetic field modulation type magneto-optical recording,
Since the recording signal quality is affected by the strength of the magnetic field, it is necessary to drive the magnetic head while maintaining it at a constant height above the recording medium.

However, in magneto-optical disk drives, there are foreign objects such as dust on the disk, warpage of the disk itself, displacement due to the tilt of the encoded disk, etc., and if the magnetic head is kept in a predetermined position, it will not be possible to maintain a constant position. Particularly in magneto-optical disk drives in which it is not possible to obtain a magnetic head flying height of 100.degree., loading and unloading of the disk is repeated, so the inclination of the disk changes each time it is loaded. Therefore, it is necessary to constantly measure the distance between the magnetic head and the disk, and control and drive the magnetic head so that this distance remains constant.

The following method is known as a method for measuring the minute flying distance of a slider or the like floating above a rotating disk.

■ A method of measuring interference fringes by irradiating light beams with multiple wavelengths.

■ A method to measure the capacitance between a slider, etc. and the disk surface.

■ A method of measuring distance based on the intensity of the received light, which shines diverging light onto the disc surface and receives the reflected light through an aperture.The intensity of the received light varies depending on the distance.

However, the above method (2) requires a very expensive measurement system, and is not suitable for measurement when the interference fringes move quickly.

On the other hand, the above methods (1) and (2) require precise calibration with respect to a reference value, and cannot be easily measured, so they are not suitable as measurement methods for actual equipment.

The above description has focused on measuring the flying height of a magnetic head from a recording disk in magneto-optical recording, but there are many other cases in which it is necessary to measure a minute distance between two objects without contact.

The purpose of the present invention is to measure minute distances with a simple system.

The method of measuring minute intervals of the present invention involves irradiating light onto a light scattering surface of an object located a minute distance from a mirror surface, condensing this reflected light with a lens, and projecting it onto a sensing element. , of this projected image,
It is characterized by measuring the distance between the mirror surface and the object by detecting the distance between the image of the light scattering surface and its mirror image.

- Light irradiated onto an object with a light-scattering surface is diffusely reflected,
After being reflected directly or from a mirror surface, the light is focused by a lens and projected onto a detection element. At this time, this projected image becomes a "bright-dark-one-bright" image in which the portion between the light-scattering surface of the object and its mirror image is dark, and the image of the light-scattering surface and its mirror image are bright. Therefore, by detecting the length of the dark part, the distance between the mirror surface and the object is calculated from this length and the lens position.

FIG. 1 is an explanatory diagram showing the principle of the measuring method of the present invention.

An object 13 having a light scattering surface is located at a distance of height h from the mirror surface 11. This object 13 has a diffused reflection surface 13a in a plane that intersects with the mirror surface 11.

FIG. 1 shows a state in which the surface including the diffused reflection surface 13a and the mirror surface 11 are substantially perpendicular to each other. From light source 15 to object 1
3, the light is diffusely reflected by the diffusely reflecting surface 13a.

This is observed from the direction of light reflection, that is, from the light source 15 side with respect to the diffused reflection surface 13a.

The diffused reflection surface 13a and the mirror image 13a' of the diffused reflection surface are bright, and the area between them is observed to be dark. When this is photographed by the lens 17 and imaged and projected onto the line sensor 19, an image consisting of the bright area (revised) - dark area (Oka) - bright area (GH) is projected, so it is projected onto the line sensor 19. By detecting the edge portion of the output, the length of the dark portion FG can be determined with an error of about one pixel.

Now, set each length and angle as shown in FIG.

a: Distance between the object 13 and its mirror image 13' = 2hb: Projection length of a on the plane perpendicular to the optical axis of the lens 17 (AB) θ: Angle between the optical axis of the lens 17 and the mirror surface 11 D1: Lens Distance between 17 and line segment AB: If the distance is between lens 17 and line sensor 19, then b = 2 Sashi is required.

Since b is the projected length of a caused by measurement at an angle θ with respect to the mirror surface 11, b = a

h = + a = + - x divination = divination x 7 x yuan... (2) Above (2
) In the formula, θ+pz is determined by the measurement system and can be fixed, so if D can be fixed.

The distance between the object 13 and the mirror surface 11 can be easily measured from the output of the line sensor 19.

Furthermore, once D□ and D2 are fixed and the absolute values are calibrated, the absolute value of the distance can be directly measured. The larger D2 is with respect to D, the more accurate distance measurement becomes possible.

Furthermore, in FIG. 1, if the mirror surface 11 is a recording medium (magneto-optical disk) surface and the object 13 is a magnetic head or a support member on which a magnetic head is mounted, it can be applied to measurement and control of the flying height of a magnetic head in magneto-optical recording. I understand.

FIG. 2 is an explanatory diagram showing an embodiment applied to a flying height measurement/control method of a magnetic head in a magneto-optical recording device.

A slider 21 (magnetic head mounting member) on which a magnetic head (not shown) is mounted is supported by an arm 23, and this arm 23 is fixed to a support member 25. The support member 25 is controlled and driven by an actuator (not shown), drives the magnetic head in the radial direction of the magneto-optical disk 41, and also drives the slider 21 on which the magnetic head is mounted.
The flying height of the magnetic head can be controlled by moving up and down. The arm 23 includes a light source 31, a lens 33, and a light receiving element 3.
5 is fixed.

When the magneto-optical disk 41 rotates in the direction of arrow A and the magneto-optical recording device is driven, a light source 31 such as an LED fixed to the arm 23 irradiates the diffused reflection surface 21a of the slider 21 with light. This state is photographed with a lens 33, and an image is formed and projected onto a light receiving element 35 such as a line sensor. Thereby, the flying height h of the slider 21, that is, the flying height of the magnetic head can be measured, and by supplying this as a servo signal to the actuator and driving the support member 25 up and down,
The distance between the magnetic head and the magneto-optical disk 41 can always be kept constant. Since the lens 33 and the slider 21 are both fixed to the same arm 23, the distance (Dl in FIG. 1) between the lens 33 and the diffused reflection surface 21a is fixed, making it easy to control the measurement of the flying height. The diffused reflection surface 21a of the slider 21 is a polished surface, but it is polished to the extent that it causes light scattering.

Note that the slider 21 used as a support and mounting member for the magnetic head in this embodiment has different properties from the winchiesta type floating head slider used in hard disk drives and the like. This floating head slider attempts to maintain a constant distance from the disk by receiving the buoyancy force caused by the rotation of the disk. On the other hand, in this embodiment, the distance between the slider 21 and the disk 41 is measured by the method of the present invention as described above, and the actuator 4 is driven by feedback control.
remains constant. The slider 21 has a large area,
This is to prevent the second slider 21 (magnetic head) from colliding with the magneto-optical disk 41 due to the air floating blade when the slider 21 and the magneto-optical disk 41 suddenly approach abnormally.

Although the above description has focused on measuring and controlling the flying height of a magnetic head on a magneto-optical disk, the measuring method of the present invention can be applied to measuring distances between various objects having mirror surfaces and light scattering surfaces, respectively.

According to the present invention, light is irradiated onto an object having a light scattering surface located a minute distance from a mirror surface, and the reflected light is projected and detected by a lens, thereby creating a simple illumination system. By combining imaging systems, it is possible to measure minute distances between objects. Since this measurement system has a simple configuration and is inexpensive, it can be incorporated into various devices including magneto-optical disk drives.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the principle of the present invention. FIG. 2 is an explanatory diagram showing an embodiment applied to a flying height measurement/control method of a magnetic head in a magneto-optical recording device. 11...Mirror surface 13.Object 13'...Mirror image of object 15...Light source F...Lens
19 Line sensor 21...Slider
23...Arm 25...Supporting member 31...
・Light source 33...Lens 35・Light receiving element 4
1... Magneto-optical disk

Claims (1)

[Claims] 1. Light is irradiated onto the light-scattering surface of an object located a minute distance from the mirror surface, and this reflected light is collected by a lens and projected onto a detection element, and the light of this projected image is A method for measuring minute distances, characterized in that the distance between the mirror surface and the object is measured by detecting the distance between the image of the scattering surface and its mirror image. 2. The measuring method according to claim 1, wherein the distance between the object and the lens is fixed. 3. The measuring method according to claim 1 or 2, wherein the mirror surface is a recording medium, and the object is a magnetic head or a mounting member for a magnetic head.