JP3019647B2 - Non-contact thickness gauge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact thickness gauge capable of accurately measuring the thickness of a sheet-like object in a non-contact manner.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram of a conventional non-contact thickness gauge, which is described in Japanese Utility Model Laid-Open Publication No. 59-32907.
In FIG. 1, M is a sheet-like object, 11 is a laser oscillator,
Reference numeral 12 denotes a detector that receives the laser beam incident on and reflected by the sheet-like object M, and reference numeral 13 denotes an amplifier that receives the output of the detector. These laser oscillator 11 constitutes a first non-contact distance meter and the detector 12 and amplifier 13, to measure the detector 12 and the distance d ₁ between the object M. On the other hand, laser oscillator 1
4, a detector 15 and an amplifier 16 are a second non-contact distance meter disposed below the object M, and measure a distance d ₂ between the detector 15 and the object M.

[0003] 17 is an oscillation coil, 18 is a target, 1
Reference numeral 9 denotes a detection coil, which constitutes a third non-contact distance meter for measuring a distance 1 between the first and second non-contact distance meters. As the third non-contact distance meter, it is necessary to measure the distance 1 between the first distance meters passing through the object M, and therefore, for example, an eddy current type distance meter is used. Reference numeral 30 denotes an upper head in which the laser oscillator 11, the detector 12, the amplifier 13, the oscillation coil 17, and the detection coil 19 are integrated. Reference numeral 31 denotes a lower head in which the laser oscillator 14, the detector 15, the amplifier 16 and the target 18 are integrated.

Reference numeral 20 denotes the output Vd of the amplifier 13 _{and the} amplifier 16
A calculator for outputting a signal V _d corresponding to the thickness d of the object M by receiving the output Vl of the output Vd ₂ and the detection coil 19. As the arithmetic unit 20, for example, a microcomputer is used.

FIG. 3 is a diagram for explaining the operation of the non-contact distance meter. The laser light emitted from the laser oscillator 11 is incident on the object M and then reflected. The reflected light forms an image at point P via the lens L. Varying the distance d ₁ between the oscillator 11 and the object M, the imaging point P is moved up and down on the straight line l _1. Therefore, if a plurality of light receiving elements are arranged on the straight line l ₁ and the outputs of these light receiving elements are taken out differentially, the differential output corresponds to d ₁ , so that the distance d ₁ is measured. can do.

Next, the operation of the third non-contact distance meter will be described. Assuming that a magnetic material is used as the target 18, the impedance of the detection coil 19 is
It changes according to the distance 1 between the target 18. From this, the distance l can be measured. Since the distance 1 between the oscillation coil 17 and the target 18 is equal to the distance between the first and second non-contact distance meters disposed on the upper and lower heads, the distance l between the upper and lower first and second non-contact distance meters is equal. The distance can be measured. The signal corresponding to 1 is output from the detection coil 19 as Vl.

As described above, the distances d _{1 and} d ₂ between the detectors 12 and 15 and the object and the distance ₁ between the detectors 12 and 15 are obtained, so that the thickness d of the object M can be obtained by the following equation. d = 1− (d ₁ + d ₂ ) (1) As is apparent from the equation (1), an accurate thickness d can always be measured even when the relative position 1 between the upper and lower heads changes. .

[0008]

Incidentally, such a non-contact thickness gauge is used for online measurement in a paper making process. In that case, the sheet-like object to be measured is, for example, several K per hour.
It moves at a speed of m to several tens of km, and the upper and lower heads are separately driven with the sheet-like object interposed therebetween. Therefore, a swell (inclination) is generated in the sheet-like object, and the upper and lower heads are displaced in the X, Y, and Z directions.

FIG. 4 shows the relationship between the sheet-like object and the irradiation points A and B of the first and second distance meters disposed on the upper and lower heads. FIG. 4A shows a state in which the sheet-like object has undulation. ,
(B) shows the case where the undulation is enlarged and there is no deviation between the upper and lower heads, and (c) shows the case where the undulation is enlarged and the upper and lower heads are displaced. When the sheet-like object is tilted due to undulation as shown in FIG. 9B, the apparent thickness (l ₁ ) is 1 / cos θ with respect to the actual thickness t, and the upper and lower heads are displaced. Has an apparent thickness of l ₁ + the deviation distance l ₂ · tan θ. There is a problem that a measuring device having such an error cannot be applied as a measuring device requiring high quality on the order of μm.

The present invention has been made to solve the above-mentioned problems of the prior art. A first distance meter is composed of at least three optical sensors, and the average value of the outputs of the optical sensors and the second distance are calculated. An object of the present invention is to provide a non-contact thickness gauge capable of more accurately measuring the thickness of a sheet-like object by calculating the output of the gauge and the output of the third distance meter.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for measuring the distance between an upper and lower head disposed on a sheet-like object and a distance from the upper and lower heads to the sheet-like object. A first and second optical rangefinders, and a third rangefinder for measuring a distance between the first and second rangefinders;
A non-contact thickness meter configured to calculate an output of the first and second distance meters and an output of the third distance meter to measure the thickness of a sheet-like object. One of the rangefinders is composed of at least three optical sensors, and when each light of the sensors irradiates a different point on the surface of the sheet-like object, an area formed by connecting the irradiation points is predicted in advance. The upper and lower heads are arranged so as to form a range larger than the range of the displacement of the upper and lower heads, and the average value of the outputs of the sensors composed of the at least three optical sensors, the output of the second distance meter, and the third The thickness of the sheet-like object is measured by calculating the output of the range finder.

[0012]

By calculating the average value of the outputs of the sensors composed of at least three optical sensors, errors due to the displacement of the upper and lower heads are reduced.

[0013]

1 (a) and 1 (b) are explanatory views of a non-contact thickness gauge showing an embodiment of the present invention, and show a case where three sets of optical sensors are provided. The present invention differs from the conventional example shown in FIG.
1, three detectors 12 and three amplifiers 13 are provided, and each signal is input to an arithmetic unit 20. This arithmetic unit 20 calculates the average value of the outputs from the three sets of sensors.

In FIG. 1, d indicated by a two-dot chain line indicates a range of the deviation of the upper and lower heads which is predicted in advance. The range of the deviation d is previously driven under the same conditions as in the measurement state. Determined based on the maximum deviation amount. A, A ₁ ,
Point indicated by A ₂ three optical sensor indicates the point of irradiating the sheet-like object, is one side in the tangent of the diameter d to form an equilateral triangle of l _4. Point o indicates a point where the second rangefinder on the other side irradiates the sheet-like object with no deviation between the upper and lower heads.

[0015] (b) drawing waviness in the sheet-like article was A ₁ (or A ₂₎ l _4/2 shift to points irradiation point of the second distance meter (E) is shown in Figure 1 with inclination occurs occurs The state is shown. In this case, the arithmetic unit 20 (see FIG. 2) determines the distance to the sheet-like object based on the output from each sensor as L ₁ +
Computed as L ₂ + L _3/3. When the distance between the upper and lower heads measured by the third distance meter is D and the distance measured by the second distance meter is U, the thickness t measured by the thickness meter is as follows. _{t = D-U- (L 1} + L 2 + L 3/3)

That is, according to the present invention, the displacement of the conventional head
Error tanθ · l _ThreeHalf the t
anθ · l_Three/ 2. Also, like this
The device measures the thickness of a traveling sheet-like object by, for example,
This is performed at a position where the sheet width is divided into several equal parts.
Is constantly changing.

In the present invention, since three sets of optical sensors are used, the distances (d ₁₁ , d ₁₂ ,
The difference d ₁₃ ) can be calculated by the calculator 20, and the difference corresponds to the undulation (tilt) of the sheet-like object. Therefore d
_{11 -d 12, d 11 -d 13} , calculates a d ₁₂ -d _13, those exceeding the set value is the difference measured more exact thickness if in the manner to disable its data can do. In this embodiment, the optical sensor is described as a device using laser light. However, the sensor may be a light emitting diode, and the number of sensors is four, five or more. You may.

[0018]

According to the present invention, one of the first and second rangefinders is constituted by at least three optical sensors, and the sensor of the sensor is constructed as described above. When each light illuminates a different point on the surface of the sheet-like object, the area formed by connecting the illuminated points is arranged so as to form a range larger than the range of the deviation of the upper and lower heads which is predicted in advance. , At least 3
The thickness of the sheet-like object is measured by calculating the average value of the outputs of the sensors constituted by the two optical sensors, the output of the second distance meter, and the output of the third distance meter. A non-contact thickness gauge capable of measuring thickness can be realized.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing one embodiment of the present invention.

FIG. 2 is a configuration explanatory view showing a conventional example.

FIG. 3 is a diagram illustrating the operation of a non-contact distance meter.

FIG. 4 shows a sheet-like object and first and second heads arranged on upper and lower heads.
It is a figure which shows the relationship of the irradiation points A and B of a 2nd range finder.

[Explanation of symbols]

 11, 14 Laser oscillator 12, 15 Detector 13, 16 Amplifier 17 Oscillation coil 18 Target 19 Detection coil 20 Calculator 30 Upper head 31 Lower head A Irradiation point of first sensor B Irradiation point of second sensor M Sheet-shaped object

Claims (1)

(57) [Claims] A first and a second optical distance meter provided on the upper and lower heads for measuring a distance to the sheet-like object; A third distance meter that measures the distance between the second distance meters;
A non-contact thickness meter configured to calculate an output of the first and second distance meters and an output of the third distance meter to measure the thickness of a sheet-like object. One of the rangefinders is composed of at least three optical sensors, and when each light of the sensors irradiates a different point on the surface of the sheet-like object, an area formed by connecting the irradiation points is predicted in advance. And an average value of the outputs of the sensors composed of the at least three optical sensors, the output of the second distance meter, and the third output. A non-contact thickness meter, wherein the thickness of a sheet-like object is measured by calculating the output of a distance meter.