JPH07234116A - Warpage rate measuring method for plate material - Google Patents

Abstract

PURPOSE:To provide a method for measuring a warpage rate of a plate material which can accurately measure even when a reflectivity of a front surface of the material to be measured is not constant. CONSTITUTION:The method for measuring a warpage rate of a plate material comprises the steps of irradiating the material 10 to be measured with a plurality of parallel spot rays provided in the vicinity, imaging the reflected rays by a camera 12 disposed at a predetermined position, obtaining a position of a center of gravity of an entirety from positions of centers of gravity of the imaged reflected rays, and measuring the rate of the material 10 by using the obtained position of the center of gravity of the entirety.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention uses spot light to
For example, it relates to a method for measuring the amount of warpage of a plate material such as a steel plate manufactured in an iron mill.

[0002]

2. Description of the Related Art The flatness of a steel sheet is one of the important quality control items at the time of product shipment, and it has been performed by visual inspection in the past, but it is extremely inefficient and inaccurate. As described in JP-A-59-138906, a steel plate is irradiated with spot laser light, the laser light is moved in the width direction of the steel plate, and the position of the laser spot irradiated on the steel plate is detected by an optical sensor. There has been proposed a method of detecting and measuring the warp of the steel sheet from the displacement amount. A triangulation method is used as a method of measuring the amount of warpage of a steel sheet or the like using such spot light. A general method will be briefly described with reference to FIG. Irradiate 51 with spot light,
The reflected laser light from the spot irradiation portion Q is imaged by a CCD camera (an example of an optical sensor) 52, and the distance d from the displacement b on the imaging surface to the steel plate 51 based on the following equation.
Is measured. d = a / (cot θ + b / f) (f is the focal length of the lens) (1) Then, in the method for measuring the warpage of the steel plate or the like, the spot light for measuring a specific position is one, A CCD camera captures the spot light of the spot light reflected from a steel plate, etc., but when capturing it as an image signal, the image of the reflected spot light is divided for each brightness, and an image with a certain area is provided by setting a specific threshold value. The position of the center of gravity of the signal is calculated and used as the image position of the reflected spot light.

[0003]

However, when the object to be measured is a steel plate, the reflectance of the steel plate surface is not constant and the spot light to be irradiated has a constant area. Is not a perfect circle and is distorted and does not have a uniform shape. Therefore, there is a problem in that the measurement varies. Such a problem has been a common problem not only in the case of measuring the steel plate but also in the case of measuring the amount of warp of other plate materials. The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for measuring a warp amount of a plate material capable of accurate measurement even when the reflectance of the surface of the measurement target plate material is not constant. To do.

[0004]

A method according to the above-mentioned object.
The warp amount measuring method of the plate material described above irradiates a plurality of parallel spot lights closely arranged to the plate material to be measured, and images these reflected spot lights by a camera arranged at a predetermined position. The overall barycentric position is obtained from each barycentric position of the reflected spot light, and the warp amount of the plate material to be measured is measured using the obtained total barycentric position.

[0005]

In the method for measuring the amount of warp of a plate material according to the first aspect, a plurality of parallel spot lights arranged in close proximity are used, and the overall barycentric position is obtained from each barycentric position of each imaged reflected spot light. . Therefore, even if the plate material to be measured has a surface reflectance different from place to place like a steel plate, the image of the reflected spot light is distorted from a circle, and its center of gravity position is deviated from the normal center of gravity position. ,
Since multiple reflected spot lights are used, the amount and direction of variations are scattered, and by further averaging the scattered center of gravity positions to determine the overall center of gravity position, variations in the center of gravity positions are also averaged. Therefore, the more accurate position of the center of gravity can be obtained.

[0006]

EXAMPLES Next, examples embodying the present invention will be described to provide an understanding of the present invention. 1 is a perspective view showing a method for measuring the amount of warpage of a plate material according to an embodiment of the present invention, FIG. 2 is an explanatory view showing the measurement principle, and FIG. 3 is a flow chart.

First, an apparatus used in the method for measuring the amount of warpage of a plate material according to an embodiment of the present invention will be described. As shown in FIG. 1, the optical axis is set to the steel plate 10 which is an example of the plate material to be measured. A semiconductor laser group 11 which is an example of a plurality of spot light sources arranged side by side in a substantially vertical direction, a CCD camera 12 for imaging the reflected spot laser light irradiated onto the steel plate 10 by the semiconductor laser group 11, and The image processing device 13 is connected to the CCD camera 12. These will be described below.

Each of the semiconductor laser groups 11 has three
The semiconductor laser elements 11a are arranged in parallel on the vertices of an equilateral triangle, and three parallel laser beams are applied to the steel plate 10 from the vertical direction. These semiconductor laser groups 11 are arranged so as to cross the steel plate 10 in the threaded plate, and the amount of warpage of the steel plate 10 in the width direction can be measured. In order to improve accuracy, the distance between the semiconductor laser elements 11a is preferably a small distance within a range in which images obtained by capturing the adjacent laser light and its reflected laser light do not interfere with each other. Keep it about 2 to 10 times. And
Although the number of the semiconductor laser groups 11 is five in this embodiment, a larger number of semiconductor laser groups 11 are used in order to measure a more precise profile of the steel sheet.

The CCD camera 12 is arranged at a predetermined angle with respect to the optical axis of the semiconductor laser group 11, and the spot laser light emitted from the semiconductor laser group 11 is reflected by the steel plate 10. Can be imaged obliquely.

The image processing device 13 includes a CCD camera 1
2, a memory circuit for receiving the video signal from the digital signal 2, converting the video signal into a digital signal and storing the digital signal if necessary, and a computer for arithmetically processing the digital video signal. . The computer has binarized the image signal, detects the center of gravity of each of the reflected spot laser light groups, and calculates the overall center of gravity, and the overall center of gravity position and the CCD camera 12.
It has arithmetic processing means for calculating the position and angle from the position to the surface of the steel plate 10 irradiated with laser light by applying the above-mentioned triangulation method, and the profile of the warp amount.

Hereinafter, referring to FIGS. 1 to 3 (A),
A method of measuring the amount of warpage of a plate material according to an embodiment of the present invention will be described in detail. As shown in FIG. 1, the steel plate 10 is irradiated with three parallel spot laser light groups from each semiconductor laser group 11, and the oblique direction is applied. The image is picked up by the CCD camera 12 (step a). When the image captured by the CCD camera 12 is converted into a digital signal and binarized by a predetermined threshold value (step b), an image partially shown in FIG. 2A is obtained. In the figure, the dotted circle is steel plate 1
0 shows the general range of the laser light irradiated onto the image 0, but the binarized images S _{1 to} S ₃ of the reflected spot laser light are distorted from a circle. This is because the reflectance of the surface of the steel plate 10 differs depending on the location.

Since the xy positions of the pixels forming each of the binarized images S _{1 to} S ₃ are known from the image, the barycentric position G ₁ (x ₁ , y ₁ ) of each binarized image S _{1 to} S ₃ is found. , G
₂ (x ₂ , y ₂ ) and G ₃ (x ₃ , y ₃ ) are obtained (step c). Further, the total gravity center position G (x, y) of these gravity center positions G ₁ , G ₂ , G ₃ is calculated by the following equation (step d) x = (x ₁ + x ₂ + x ₃ ) / 3 , Y = (y ₁ + y ₂ +
y ₃ ) / 3 Based on the overall center-of-gravity position G (x, y), the position of the steel plate 10 irradiated with the laser beam is calculated using, for example, the above-mentioned mathematical expression (1). This process is performed for each spot laser light group to calculate the warp amount or profile of the steel plate 10 (step e).

Incidentally, FIG. 2B shows an example in which one spot laser beam is used to binarize the reflected spot laser beam to obtain the position of the center of gravity. It can be seen that when the ratios are not uniform, the barycentric position G _{0 of the} image may deviate significantly from the actual center position G _C of the laser light. Table 1 compares the dispersion of the center of gravity of the spots when three spot laser beams were used in the experiment and when one spot laser beam was used. It can be seen that the accuracy is improved.

[0014]

[Table 1]

In the above embodiment, the case where three spot laser beams are used per group has been described.
The same applies to the case of four or more lines. The position of the center of gravity of each spot laser light is detected, and the xy coordinates of the positions of these center of gravity are averaged to calculate the position of the entire center of gravity. The warp amount is calculated based on the position of the center of gravity. Further, in the above-described embodiment, for example, the warpage amount is measured based on the triangulation method using the mathematical formula (1), but even if the measurement method is another method, the warpage amount is based on the irradiation position of the laser light. It goes without saying that the present invention is applied to a measuring method for calculating a quantity.

[0016]

As is apparent from the above description, the method for measuring the amount of warpage of a plate material according to claim 1 is relatively accurate even if the surface of the plate material is partially different in reflectance. The amount of warpage of the plate material can be measured.

[Brief description of drawings]

FIG. 1 is a perspective view showing a method for measuring the amount of warpage of a plate material according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a measurement principle.

FIG. 3 is a flowchart.

FIG. 4 is a schematic configuration diagram of an apparatus for measuring a warp amount of a steel sheet using laser light according to a conventional example.

[Explanation of symbols]

 10 Steel Plate (Plate to be Measured) 11 Semiconductor Laser Group 11a Semiconductor Laser Element 12 CCD Camera 13 Image Processing Device

Claims (1)

[Claims] 1. A plurality of parallel spot lights that are closely arranged are irradiated to a plate material to be measured, and these reflected spot lights are picked up by a camera arranged at a predetermined position. A method for measuring the amount of warpage of a plate material, which comprises obtaining an overall position of center of gravity from each of the positions of center of gravity and using the obtained overall position of center of gravity to measure the amount of warpage of the plate material to be measured.