JPH02170007A - Plate thickness measuring instrument - Google Patents

Abstract

PURPOSE:To accurately measure the thickness of a plate material such as a steel plate, aluminum plate, and a nonmetallic plate over a wide range by incorporating an adjusting mechanism for holding the length of an optical path constant following up the thickness-directional variation of an object of measurement. CONSTITUTION:Mechanisms B which detect the thickness-directional variation position of the steel plate S is provided opposite both surfaces of the steel plate S and coupled through a synchronizer 17. The laser light 6 from a light source 5 is projected on the surface of the steel plate S through a fixed mirror 1 and a movable mirror 2 and its reflected light is made incident on an optical position detecting element 12 through the fixed mirror 1 and movable mirror 2. The position of the movable mirror 2 is accurately detected by a position detector 3 and moved at right angles to the surface of the steel plate S by a linear motor which is driven according to the variation of the steel plate S. The thickness of the plate material S is calculated from the movement distance of the movable mirror 2 by controlling the movement of the movable mirror 2 corresponding to the thickness-directional variation of the plate material S which is generated in thickness measurement so that the length of the optical path reaching an optical position detecting element 12 from the light source 5 through the surface of the plate material S is constant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for accurately measuring the thickness of a plate material such as a steel plate in a non-contact manner.

[Conventional technology]

As a thickness measuring device, a radiation method is known that utilizes the fact that a measurement target is irradiated with radiation and the amount of intensity attenuation when the radiation passes through the measurement target changes in proportion to the thickness. For example, in Japanese Unexamined Patent Publication No. 61-219808, unevenness is detected by sequentially determining the integral value of the output of a radiation detector per a predetermined unit time by shifting it by a shorter time than that time.

Also known is an optical method in which a measurement target is irradiated with light and the reflected light is detected. For example, JP-A-60-572
In Publication No. 03, measurement accuracy is improved by using optical distance sensors placed on running rails installed above and below the plate material to be measured, and performing comparative measurements with the plate material and a standard plate provided at the corresponding position. ing.

[Problem to be solved by the invention]

Radiation-based thickness measurement equipment measures plate thickness from the amount of attenuation due to transmission, so even if the measurement target changes in the thickness direction, the fluctuation does not have a negative effect on the measurement results, making it possible to measure with high precision. . However, this type of thickness measuring device is much more expensive than the optical type, so its use is limited to special applications that require a very high degree of measurement accuracy.

On the other hand, optical thickness measuring devices are based on a triangulation method, and determine the displacement of the measurement object by changing the triangle formed by the light projecting section, the measurement object, and the light receiving section. This method uses an optical system that narrows the light onto the measurement target, so if the distance (reference distance) between the displacement measurement mechanism and the measurement target is too short or too long, the light will not be diffused. arise. Furthermore, when trying to improve the accuracy of the light receiving element, there is a limit to the measurable range even if the spread of light is small. For example, when the measurement target changes in the thickness direction, the displacement measurement target position on one surface becomes too close to the light receiving element, and the displacement measurement target position on the other surface becomes too far away. As a result, both the front and back surfaces become unmeasurable.

Therefore, the present invention is capable of accurately measuring the thickness of plate materials such as steel plates, aluminum plates, non-metal plates, etc. over a wide range by incorporating an adjustment mechanism that changes the optical path in accordance with changes in the thickness direction of the object to be measured. With the goal.

[Means to solve the problem]

In order to achieve the purpose, the plate thickness measuring device of the present invention has the following features:
A fixed mirror arranged to face both sides of the plate material whose thickness is to be measured, a movable mirror provided on the back side of the fixed mirror, and a measurement light irradiated onto the surface of the plate material through the movable mirror and the fixed mirror. a light receiving section including a light position detection element through which measurement light reflected on the surface of the plate material enters through the fixed mirror and the movable mirror, and a displacement of the plate material so that the optical path length is constant. A displacement detection mechanism is provided, which includes a motor that moves the movable mirror according to the position of the movable mirror, and a position detector that detects the position of the movable mirror and outputs it to a computing unit, and the displacement detection mechanism is arranged on both sides of the plate material. It is characterized in that the detection mechanism is connected by a tuner.

[Effect]

In the present invention, in order to avoid changing the length of the optical path from the light source to the light receiving section via the surface of the plate material that is the object to be measured, a movable mirror is placed midway along the optical path into which the measurement light that has been bent by the fixed mirror is incident. It is set up in The amount of movement of this movable mirror is controlled in response to variations in the thickness direction of the plate material that occur during thickness measurement. Therefore, a clear image can always be formed on the optical position detection element of the light receiving section. Furthermore, the wall thickness of the plate material is calculated based on the moving distance of the movable mirror at this time.

〔Example〕

Hereinafter, the features of the present invention will be specifically explained using examples with reference to the drawings.

The plate thickness measuring apparatus of this embodiment has optical paths as shown in FIG. 1 on both sides of the steel plate S to be measured. That is,
Fixed mirrors 1a and lb are arranged on both sides of the steel plate S, and movable mirrors 2a and 2b are arranged on the back side thereof. These movable mirrors 2a and 2b are position detectors 3a.

3b, the position of which is accurately detected, and by linear motors 4a and 4b that are driven according to the fluctuations of the steel plate S.
It moves along the direction perpendicular to the surface of the steel plate S.

Each measuring mechanism has the configuration shown in FIG. 2, which shows one of the mechanisms. A laser beam 6 emitted from a semiconductor laser 5 serving as a light source is focused into a narrow beam by a collimating lens 7, and is irradiated onto a steel plate S to be measured. This irradiation light is reflected outward by the reflective surface 8 of the fixed mirror 1 and is incident on the movable mirror 2. This movable mirror 2 is made up of two mirrors 9a and 9b joined together at a predetermined angle with their reflective surfaces inside. The reflective surfaces of the mirrors 9a and 9b are opposed to the reflective surface 8 of the fixed mirror 1.

The movable mirror 2 is movable in six directions of arrows,
It absorbs changes in the optical path length between the collimating lens 7 and the steel plate S and between the steel plate S and the light receiving lens 10 due to displacement of the steel plate S from the measurement initial position or the measurement reference position. That is, the laser beam 6 is directed to the fixed mirror 1 as shown in FIG.
The light is bent at a right angle by the reflective surface 8 of the light beam, then is folded back by the movable mirror 2, passes through the fixed mirror 1, and is irradiated onto the steel plate S.

A part of the laser beam 6 that is diffusely reflected on the surface of the steel plate S is reflected by the movable mirror 2 and the fixed mirror 1, and is imaged by the light receiving lens 10 as a minute spot light on the optical position detection element 12 via the interference filter 11. .

Here, when the steel plate S and the movable mirror 2 are at the solid line position in FIG. Adjust it. Further, when the steel plate S is displaced as shown by the dotted line in FIG. 3, the movable mirror 2 is moved by a distance β (-δ/2) corresponding to half of the displacement amount δ of the steel plate S.

Due to this movement of the movable mirror 2, the amount of displacement δ of the steel plate S is absorbed in the reciprocation of the optical path. As a result, the laser beam 6 is imaged as a minute spot light at the imaging reference position on the optical position detection element 12, similarly to when the steel plate S is at the solid line position.

Therefore, by measuring the moving distance l of the movable mirror 2, the amount of displacement δ of the steel plate S can be determined. The movement amount of the movable mirror 2 is controlled as follows. That is, when the optical path length changes due to the displacement of the steel plate S, the diameter of the light focused on the optical position detection element 12 increases, and the imaging position shifts from the reference position. Therefore, the optical diameter and imaging position are detected by the position detector 13 shown in FIG. It also outputs a signal to the position controller 15 to reduce the light diameter and return the imaging position to the reference position. Then, from the position controller 15 to the linear motor 4,
A signal is generated to move the movable mirror 2 by a moving distance β corresponding to the displacement amount δ of the steel plate S.

By moving the movable mirror 2 with the linear motor 4, the displacement amount δ of the steel plate S is absorbed and the optical path length becomes constant. imaged as. The moving distance β of the movable mirror 2 at this time is detected by the position detector 3 and input to the calculator 14. And the moving distance of movable mirror 2! By doubling , the displacement amount δ of the steel plate S can be obtained.

Note that between the semiconductor laser 5 and the position detector 13,
A modulation signal generator 16 is provided. This modulation signal generator 16 outputs a transmission command to the semiconductor laser 5. Further, the modulation signal generator 16 is also electrically connected to the position detector 13 in order to determine the output timing.

The mechanism for detecting the displacement amount δ of the steel plate S described above is provided facing both sides of the steel plate S.

These pair of displacement detection mechanisms B are connected via a tuner 17. The tuner 17 is provided to detect displacements on both sides of the steel plate S to be tested in the same plate thickness direction at the same timing, and connects displacement detection mechanisms B provided on both sides of the steel plate S. .

As shown in FIG. 3, when the steel plate S is displaced to the right, the movable mirror 2a on the right is moved back by a moving distance β corresponding to the amount of displacement δ, and the movable mirror 2b on the left is moved the distance ! only move forward. Thereby, even if the steel plate S changes in the thickness direction, the positions of both sides of the steel plate S can be accurately detected at the same time. And movable mirrors 2a on both sides
, 2b, the movable mirror 2
By subtracting L2, the distance between a and 2b and the surface of the steel plate S, the thickness of the steel plate S is determined as L-(Ll+L2>).

At this time, since the optical path length changes according to the amount of displacement δ of the steel plate S, even if the steel plate S is displaced in the thickness direction during running, for example,
The laser beam 6 reflected on the surface of the steel plate S is focused and clearly imaged at the imaging reference position of the optical position detection element 12. Therefore, the detection accuracy is as high as ±0.1%, which is comparable to that of the radiation method, and the measurement range is greatly expanded without being restricted by the detection range of the optical position detection element 12.

In the above example, the fixed mirror 1 has a shape that allows the reflected light from the movable mirror 2 to pass therethrough. However, the present invention is not limited to this, and it is possible to use a fixed mirror provided with only the reflecting surface 8, or a mirror provided with a mirror that further reflects the reflected light from the movable mirror 2. Further, the light for measurement is not limited to laser light, and other light sources such as LED can also be used.

〔Effect of the invention〕

As explained above, in the present invention, the movable mirror is moved according to the amount of displacement of the plate material, and the optical path length from the emission of the measurement light to the reception of the measurement light is maintained constant. Then, the positions of both surfaces of the plate are detected from the amount of movement of the movable mirror when a clear image is formed on the optical position detection element, and the wall thickness is calculated from the detected values. In this way, even if the plate material changes in the thickness direction during thickness measurement, it is possible to accurately measure the wall thickness of the plate material.

[Brief explanation of the drawing]

FIG. 1 shows a state in which the thickness of a steel plate is being measured according to the present invention, FIG. 2 shows one displacement detection mechanism, and FIG. 3 is a diagram for explaining the present invention in detail. 1, la, lb: fixed mirror 2.2a, 2b:
Movable mirror 3, 3a, 3b: position detector 4.4a,
4b: Linear motor 5: Semiconductor laser 6゛Laser beam 7: Collimating lens 89 Reflective surfaces 9a, 9b: Mirror 10: Light receiving once 11゛Interference filter 12: Optical position detection element 13:
Position detector 14: Arithmetic unit 15: Position controller 17: Tuner δ: Steel plate displacement 16: Modulation signal generator S: Steel plate (measurement target)! = Moving distance of movable mirror

Claims (1)

[Claims] 1. A fixed mirror placed facing both sides of the plate material whose thickness is to be measured, a movable mirror provided on the back side of the fixed mirror, and a measuring light directed to the surface of the plate material through the movable mirror and the fixed mirror. a light source that irradiates the surface of the plate; a light receiving unit that includes a light position detection element through which the measurement light reflected on the surface of the plate enters through the fixed mirror and the movable mirror; A displacement detection mechanism includes a motor that moves the movable mirror according to the displacement of the movable mirror, and a position detector that detects the position of the movable mirror and outputs it to a computing unit. A plate thickness measuring device characterized in that a displacement detection mechanism is connected by a tuner.