JPH0737898B2 - Flatness meter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a flatness meter for measuring the flatness of various flat plate flat surfaces such as hot and cold steel plates.

[Prior Art] As a conventional example of measuring the flatness of a plate material plane using an optical means, there is the following method.

(1) A method of observing contour lines of an object to be measured as moire fringes using the moire photography technique (Japanese Patent Laid-Open No. 63-2920).
(See publication 8).

(2) He was simultaneously modulated with two frequencies using a laser rangefinder.
-Illuminate an object with Ne laser light, collect the diffused reflected light, convert it into an electrical signal with a high-speed photomultiplexer via an automatic focusing mechanism, frequency-convert the received signal and average it, and measure the phase difference Then, the distance to the object is measured, and the flatness is measured thereby (see Japanese Patent Publication No. 63-2324).

(3) A method in which a plurality of laser rangefinder sensors are used to measure the distance to the object for each predetermined length of the object, and the flatness is measured based on the distance (see Japanese Patent Publication No. 60-10563).

(4) A method of measuring the plate wave height value using a plurality of laser displacement gauges arranged in the width direction of the object, and simultaneously measuring the arc length of the plate wave in a constant traveling section in the width direction (Japanese Patent Laid-Open No. 54- 2770
(See the official gazette).

(5) A method in which two laser displacement gauges are used, parallax is given to detect laser reflected light, and the flatness is measured based on the detected laser reflected light (see Japanese Patent Laid-Open No. 58-111708).

(6) A method of irradiating two different wavelength laser beams and detecting the reflected light to measure the flatness (JP-A-58-115314).
(See the official gazette).

[Problems to be Solved by the Invention] The conventional flatness measuring techniques include the above-mentioned methods, but each has a problem as described below.

The moiré photography method (1) above is performed with a large amount of cutting light, but when the resolution is poor due to the ITV continuum and the detection of flatness in the longitudinal direction is difficult in terms of calculation processing, and the path line fluctuation is large. Since the pass line variation and the flatness defect are added, the displacement of the plate in the thickness direction cannot be accurately measured.

The method of (2) is characterized in that the modulation of the laser light is used, but there is a large variation due to a flat defect during the modulation, and a large portion of the visual field cannot be measured. In addition, since the structure of the measuring device is complicated, the adjustment error factor is included in the measurement value, resulting in a large error. He-N as modulated light
Since the e-laser is used, the life of the laser light source is short, about 10 ⁴ Hr.

In the above method (3), since the laser rangefinder is used, an error factor due to path line fluctuation is included in the measured value, and the S / N ratio deteriorates. In addition, since the distance detection sensitivity of the rangefinder itself varies depending on the length, it is unclear what the actual measurement accuracy is.

In the method of (4) above, since the laser displacement meter is used, the error due to the pass line variation factor becomes large,
The flatness accuracy becomes as large as about ± 4, and the relative detection accuracy becomes low, especially for thin objects. Further, although the twin beam method is adopted in consideration of the plate vibration of the object, accuracy control is practically difficult because the displacement difference is small. Furthermore, since the beam method cannot see the whole, it is difficult to detect the widthwise distribution of flatness. Further, since the distance between the sensor and the object to be measured cannot be made large, the installation location of the sensor is limited.

In the above method (5), since two laser beams are focused on one detector, a supplementary limit occurs on the detector depending on the angle of flatness. Also, because a displacement meter is used,
The error due to the fluctuation of the pass line is included.

In the above method (6), since laser beams of two different wavelengths are used, it is necessary to perform numerical correction and at the same time, a wavelength discriminating means is required.

As described above, the method of the conventional example has a problem of path line variation,
There are problems such as difficulty in detecting the distribution of flatness in the width direction, large measurement error because a sensor with a large S / N ratio must be used, and the necessity of wavelength identification and numerical correction.

[Means for Solving the Problems] In order to solve the problems of the above-described conventional techniques, in the present invention, a measurement target is irradiated with laser light, and the reflected light is reflected by a plurality of two-dimensional detectors to form a visual field. It is characterized in that it is provided and detected, and the flatness can be measured by calculating the detection signal.

[Embodiment] FIG. 1 shows an embodiment of the present invention, in which 1 is a plate material such as a steel plate which is an object to be measured, 2 is a laser light source for irradiating the width direction of the plate material, 3 _{A 3B} is a laser light source 2
-Dimensional CCD that detects the light reflected from the plate material 1
A camera, 4 is an E / O device, 5 is a CPU, 6 is a process computer, 7 is a desk, 8 is a recorder, 9 is a CRT display, and 10 is a pulse for detecting the rotation of a roll for transferring the plate material 1. The output PLGs, 11 are counters for counting the pulses from the PLG 10 and detecting the traveling speed of the plate 1.

The principle of the present invention will be described with reference to FIGS.

As shown in FIG. 2, the laser light source 2 is configured to irradiate the laser light in parallel in the width direction of the plate material 1 with a predetermined width W in the longitudinal direction (travel direction). The center line is arranged so as to intersect with the measurement point O of the plate material 1. The cameras 3 _A and 3 _B are arranged at a predetermined height H with respect to the surface of the plate member 1, and the outermost end (outer side in the longitudinal direction) of the parallel laser light is in an ideal flat state (virtual plane). It is arranged so that the reflected light from the points P ₁ and P ₂ that intersect the plate member 1 can be detected at a predetermined angle θ. The line connecting the camera 3 _A and the point P ₁ and the line connecting the camera 3 _B and the point P ₂ are arranged so as to intersect at the point R on the center line of the parallel laser light. The distance to and is ho. The distances from the point R to the cameras 3 _A and 3 _{B in} the longitudinal direction are L, respectively.

When the above relationship is expressed by a mathematical expression, tan θ = 2ho / W = (H + ho) / L (1) There is no unevenness in the portion of the plate material 1 irradiated with the parallel laser light,
If it is flat, the cameras 3 _A and 3 _B are both point P ₁ ,
Since it is detected that the point P ₂ is the extreme end point where the parallel laser beam is irradiated, as shown in the lower part of FIG.
In AB, it is detected that the deviations a ₁ , a ₂ and b ₁ , b ₂ from the points P ₁ and P ₂ viewed from the respective cameras are all 0,
Therefore, the deviation a ₀ = (a ₁ + a ₂ ) / 2 = 0 b ₀ = (b ₁ + b ₂ ) / 2 = 0 at the detection point O is obtained, and the point O has no unevenness when viewed from the virtual plane. Things are detected.

On the other hand, if there is a convex portion near the point O of the plate 1 as shown in FIG. 3, the end of the laser beam intersects the plate 1 at the points P ₁ ′ and P ₂ ′, so that the camera 3 _A The end of the laser beam is detected to be in the directions of points P _1A and P _2A , and the camera 3 _B detects that the end of the laser beam is in the directions of points P _1B and P _2B . Therefore, as shown in the lower part of FIG.
Deviations from P ₁ to a ₁ and b ₁ and deviations from points P ₂ to a ₂ and b ₂ are detected.

Then, by averaging these deviations, the displacement at the point O
a ₀ and b ₀ are obtained by the calculation of a ₀ = (a ₁ + a ₂ ) / 2 b ₀ = (b ₁ + b ₂ ) / 2.

A method for obtaining the displacement in the height direction at the point O based on a ₀ and b ₀ thus obtained will be described with reference to FIG.

FIG. 4 is an enlarged view of a portion around the point R in FIG. 3, and the displacements a ₀ and b ₀ are obtained as described above.

Since the angle θ ′ is θ ′ = π / 2−θ as is clear from the figure, h _A = a ₀ / tan θ ′ = a ₀ / cot θ (2) ha = b ₀ / tan θ ′ = b ₀ / cot θ (3), and the displacement in the height direction at the point O is hx = h _B + {b ₀ (h _A −h _B )} / (a ₀ , where hx is the distance from the point R to the point R ′. + b ₀₎ = a _{(a 0 h B + b 0} h a) / (a 0 + b 0). Then, if the above equation is modified based on the equations (2) and (3), hx = 2a ₀ b ₀ / {cotθ (a ₀ + b ₀ )} (4) and further, based on the equation (1), hx = 2a ₀ b ₀ / (a ₀ + b ₀ ) × H / (2L−W) (5) is obtained, and the displacement amount hx is obtained using the equation (4) or the equation (5).

As described above, the displacement hx in the height direction at the point O is obtained, but the cameras 3 _A and 3 _B scan the plate 1 in the length direction by a predetermined width (width W of the parallel laser light or more). The displacement of the point O which is the center point thereof is detected based on the detected reflected light, and the displacement of each point in the plate width direction including the point O is detected by repeating it in the plate width direction. Further, since the plate material 1 is traveling at a predetermined speed, by repeating the above, the longitudinal direction of the plate material 1 is also scanned, and the flatness can be detected over substantially the entire surface of the plate material 1.

Returning to FIG. 1, the outline of the operation of the present invention will be described. The reflected light signals detected by the two-dimensional CCD cameras 3 _A and 3 _A are sequentially passed through the E / O device 4 according to the scanning operation of the camera. It is supplied to the CPU 5 and the calculation as described with reference to FIGS. The obtained value hx is determined as the coordinate of the measurement point based on the scanning operation and the traveling speed signal of the plate 1 from the counter 11, and the detected value hx is stored in the memory unit in the CPU in association with the coordinate. To be done. The stored detection value is recorded in the recorder 8 and, if necessary, is supplied to the CRT display 9 to visually display the flatness. The process computer 6 incorporates a program and controls the operation of the entire apparatus.

[Effect] Since the present invention is configured as described above, the following operational effects can be obtained.

a. If the installation height H of the camera is increased to some extent, it is possible to make the influence of the path line variation negligible.

b. By appropriately adjusting the distance L in the longitudinal direction from the H and the measurement point O to the camera, the values of the deviations a ₀ and b ₀ can be changed to sufficient accuracy, and the value can be set to a value larger than the actual flatness. Can also detect large fluctuations, and therefore even minute displacements can be detected.

c. The accuracy can be further improved by adjusting the beam width W.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing one embodiment of the present invention, and FIGS. 2 to 4 are explanatory diagrams for explaining the principle of the present invention. 1 ...... plate 2 ...... laser light source 3 _{A, 3 B} ...... 2-dimensional CCD camera

Claims (1)

[Claims] 1. A flatness meter for measuring flatness of a plate material, which comprises a light source arranged above the plate material and irradiating a parallel beam having a predetermined width in the longitudinal direction of the plate material over the entire width direction of the plate material. Two two-dimensional cameras for detecting reflected light emitted from a light source and reflected by a plate material, the two-dimensional cameras being arranged symmetrically with respect to the light source when viewed in the longitudinal direction of the plate material, and having a range wider than the width of a parallel beam in the longitudinal direction. 2 and the reflected light in the same direction and the same pitch in the width direction.
Based on the two-dimensional cameras that detect two-dimensionally and the detection signals from each two-dimensional camera, the direction from each two-dimensional camera of the two points where the plate material intersects the longitudinal ends of the parallel beam, And a computing device that computes the displacement in the height direction of the point where the longitudinal centerline of the parallel beam intersects the plate material based on the direction.