JP2007205868A - Device and method for optical shape inspection - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shape detection device and method for accurately detecting a shape by finding the gradient of the longitudinal direction of a plate without being affected by the gradient of the width direction of the plate or vertical movement of the plate in measuring the shape of the plate by photographing the virtual image of a bar-like light source reflected on the surface of the plate material. <P>SOLUTION: Outgoing light from the bar-like light source 3 is radiated to the conveyed plate material 1, the virtual image of the bar-like light source 3 reflected on the surface of the plate material is continuously sampled by an imaging means 3, the bar-like light source 3 is arranged perpendicularly to a conveying direction and width direction of the plate material 1, longitudinal positional information of the bar-like light source 3 is added to the outgoing light, and the shape of the plate material 1 is calculated based on the photographed image of the virtual image including the longitudinal positional information. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an apparatus and a method for optically detecting the shape of a strip such as a rolled material.

  2. Description of the Related Art Conventionally, various methods have been used as means for optically detecting the shape in a manufacturing process of a plate material (or a plate) which is a band-shaped body such as a metal material. As a typical measurement means, a rod-shaped light source that irradiates in the width direction of the plate and an imaging means are arranged in the vicinity of the plate material, a virtual image of the rod-shaped light source reflected on the surface of the plate is detected by the imaging means, and the distortion of the image is detected. There is a method for calculating the shape of the plate. Examples of this method include Patent Document 1 and Patent Document 2. These documents use the fact that at each position in the width direction of the plate, the position of the image when the plate is a plane is the reference position, and the amount of deviation of the image from the reference position is proportional to the inclination of the plate. Thus, the inclination in the longitudinal direction of the plate with respect to the plane is obtained for each point in the width direction. Then, this inclination is integrated in the longitudinal direction to calculate the length along the surface of the plate at each point in the width direction, and the shape parameters of the plate material such as the difference in elongation in the width direction are calculated from the difference in length. I'm calculating.

JP-A-5-157536 JP-A-8-114425

However, the conventional example has the following problems.
In Patent Document 1, a rod-shaped light source is installed as an example so as to face the plate and cross in the width direction, and in this arrangement, the vertical movement of the plate does not significantly affect the measured value of the plate inclination. Although shown experimentally, it is often difficult to arrange such light sources due to workability problems and safety problems when the plate breaks.

  In the embodiment of Patent Document 2, a rod-shaped light source is arranged perpendicular to the conveying direction and the width direction of the plate. In such an arrangement, the deviation amount from the reference position of the virtual image is There is a problem that the inclination in the longitudinal direction of the plate cannot be obtained accurately because it is affected by the inclination in the longitudinal direction, the inclination in the width direction, and the height of the plate.

  In order to solve the above problems, an object of the present invention is to reduce the inclination in the longitudinal direction of the plate without being affected by the inclination in the width direction of the plate or the height of the plate in the configuration in which the rod-shaped light source is arranged perpendicular to the plate. It is to obtain a shape with higher accuracy than before.

  In order to solve the above-described problems, in the present invention, the plate material to be conveyed is irradiated with the emitted light from the rod-shaped light source, a virtual image of the rod-shaped light source reflected on the plate material surface is collected as an image by the imaging means, and In the optical shape detection device for detecting the shape of a plate material, the rod-shaped light source is disposed beside the plate material in a direction perpendicular to the conveying direction and the width direction of the plate material, and the longitudinal position information of the rod-shaped light source is added to the emitted light. There is provided an optical shape detection device comprising a shape calculation unit for calculating the shape of a plate based on the image including the longitudinal position information of the rod-shaped light source.

  Further, in the optical shape detection device, the means for adding the longitudinal position information of the rod-shaped light source may change the emitted light color in the longitudinal direction of the rod-shaped light source, and the imaging means may be a color camera.

  Further, in the optical shape detection device, the means for adding the longitudinal position information of the rod-shaped light source scans the light emission position of the rod-shaped light source in the longitudinal direction of the rod-shaped light source as time changes, and the imaging means detects the light emission position. High-speed imaging that can be identified may be possible.

  Then, the shape calculation unit is configured to make reference to the reference plane for each point C of the plate based on the position of each point A in the rod-shaped light source and the position of the point B of the image of the rod-shaped light source corresponding to each point A. The inclination of the conveyance direction is calculated, and the shape of the plate material is calculated based on the inclination of each point C of the plate material.

  In order to solve the above-described problem, according to the present invention, a virtual image of the rod-shaped light source reflected on the plate material surface is photographed by an imaging unit by irradiating the plate material to be conveyed with light emitted from the rod-shaped light source. In the optical shape detection method for detecting the shape of the plate material by taking an image by the method, the rod-shaped light source is disposed beside the plate material in a direction perpendicular to the conveying direction and the width direction of the plate material, and is formed into a rod shape for the emitted light. An optical shape comprising means for adding longitudinal position information of a light source, wherein the shape of a plate material is derived by a predetermined calculation based on the image including the longitudinal position information of the rod-shaped light source A detection method is provided.

  In the optical shape detection method, the means for adding the longitudinal position information of the rod-shaped light source may change the emitted light color in the longitudinal direction of the rod-shaped light source, and the imaging means may be a color camera.

  In the optical shape detection method, the means for adding the longitudinal position information of the rod-shaped light source scans the light emission position of the rod-shaped light source in the longitudinal direction as time changes, and the imaging means can identify the light emission position at high speed. You may make it image-capable.

  Then, the predetermined calculation is based on the position of each point A in the rod-shaped light source and the position of the point B of the image of the rod-shaped light source corresponding to each point A with respect to the reference plane for each point C of the plate material. The inclination of the conveyance direction is calculated, and the shape of the plate material is calculated based on the inclination of each point C of the plate material.

  According to the present invention, the shape of the plate material is calculated based on the image of the rod-shaped light source by adding an index indicating the position to the light emitted from each position of the rod-shaped light source. Even when it is arranged vertically, the inclination in the longitudinal direction of the plate can be obtained with higher accuracy than before without being affected by the inclination or inclination in the width direction of the plate. In addition, since the rod-shaped light source does not cross the plate, workability is good, and there is an advantage that the device is not damaged even when the plate is broken.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing an outline of an embodiment for carrying out the optical shape inspection apparatus of the present invention.

  In this Embodiment, the shape measuring apparatus of the said steel plate 1 which conveys the manufacturing process of steel in a horizontal direction is demonstrated in detail about the case where the board | plate material to be examined is a steel plate. Next to the steel plate 1 conveyed by the roll 2, the rod-shaped light source 3 is installed in the normal direction of the flat steel plate surface without unevenness (that is, perpendicular to both the conveying direction and the width direction of the steel plate 1). A virtual image reflected by the rod-shaped light source 3 on the steel plate 1 is picked up by a color CCD camera (hereinafter referred to as a camera) 4 which is an image pickup means. At this time, a line connecting the point 4 with the camera 4 and the rod-shaped light source 3 is perpendicular to the conveying direction of the steel plate 1 (longitudinal direction of the steel plate 1) so that a straight image can be obtained when the steel plate 1 is flat. In addition, the viewing direction of the camera 4 (the center direction of the visual field, that is, the optical axis) is arranged so as to intersect the extended line of the rod-shaped light source 3.

  The rod-shaped light source 3 changes its emission color along the longitudinal direction so that the longitudinal position corresponding to each point of the virtual image captured by the camera 4 can be specified. The image picked up by the camera 4 is sent to the shape calculation unit 5, and the virtual image position in the picked-up image and the corresponding longitudinal position of the rod-shaped light source 3 are obtained. Further, the shape calculation unit 5 calculates the inclination in the longitudinal direction of the steel sheet 1 from the virtual image position and the corresponding longitudinal position of the rod-shaped light source 3, and calculates the shape of the steel sheet 1 by integrating the inclinations.

<Basic procedure for optical shape measurement>
FIG. 2 is a cross-sectional view in the longitudinal direction of the steel sheet including a certain point in the width direction at a position R in the longitudinal direction of the steel sheet 1. The shape measurement procedure and principle of the optical shape inspection apparatus of the present invention will be described with reference to FIGS.
(A) The longitudinal inclination q with respect to the horizontal plane is determined at each point Wi in the plate width direction of the steel plate 1. Each point Wi is located at a plurality of appropriate positions in the plate width direction of the steel plate 1. In FIG. 1, as an example, each point Wi is set to five points on both edges, the center, and the left and right 1/4 width positions of the steel plate 1.
(B) Multiplying the imaging interval Ts (typically 1/60 second) of the camera 4 by the conveying speed Vd of the steel plate 1 to obtain the measurement pitch Ls, and using this measurement pitch Ls, the hypotenuse length Ld is obtained. The length L along the surface of the steel plate 1 is obtained by integrating for a certain section.
(C) The length L (i) along the surface of the steel plate 1 is obtained at each point Wi in the width direction (for example, five points at both edges, the center, and the left and right 1/4 width positions), and the length L (i) By dividing the length L (i) of each point by the minimum value L (imin) in the width direction, the difference in elongation at each point Wi in the width direction, which is the shape parameter of the plate, is calculated.

<Relationship between captured image, longitudinal inclination of steel sheet, position on bar light source, and camera position>
FIG. 3 shows an image obtained by photographing a virtual image of the rod-shaped light source 3 with the camera 4. In FIG. 3, the horizontal direction corresponds to the longitudinal direction of the steel sheet 1, and the vertical direction corresponds to the width direction. A vertical line passing through the visual field center O ′ indicated by a solid line as an image of the rod-shaped light source 3 is obtained using the horizontal and flat surface of the steel plate 1 as a reference plane. This straight line is set as a reference position. On the other hand, when the steel plate 1 is flat and has an inclination in the longitudinal direction, it becomes a diagonal line shifted from the center of the visual field as shown by a broken line.

FIG. 4 is a diagram showing the arrangement of the coordinate system used in the following description. The origin O of the three-dimensional coordinate system (x, y, z) is located at the center of the horizontal and flat steel plate 1 (center in the width direction of the steel plate 1), x is the width direction of the plate (steel plate 1), and y is the plate In the transport direction (longitudinal direction), z is the coordinate in the height direction. Camera 4 has a point Q (xq,
0, zq), and the direction of the line of sight is such that the origin O of the three-dimensional coordinates is at the center of the visual field. The rod-like light source 3 is arranged beside the steel plate 1 (y = 0) and parallel to the z-axis at a distance of xl from the origin O in the negative direction.

  Now, a plane I (screen) passing through the origin O and perpendicular to the viewing direction of the camera 4 will be considered. A coordinate system (s, t) on the plane I is provided. The s-axis is a direction passing through the origin O and parallel to the y-axis, and the t-axis is a direction passing through the origin O and perpendicular to the s-axis. When the image is taken by the camera 4, the intersection of the plane I with a straight line connecting a certain point on the virtual image of the rod-shaped light source 3 and the point Q which is the position of the camera 4 is defined as V (s, t). That is, as shown by the broken line in FIG. 4, the light emitted from a certain point P2 (-xl, y2, z2) on the rod-like light source 3 is reflected by the point P1 (x1, y1, z1) on the plate, and the camera. The position Q (xq, 0, zq) is reached, and then the straight line P1Q passes through the point V (s, t) on the plane I. Therefore, each point on the rod-shaped light source 3 is reflected by the steel plate 1 and is imaged on the imaging surface of the camera 4 so that the virtual image of the rod-shaped light source 3 is captured by the locus of the point V on the plane I described above. Can be thought of as The coordinate V of the rod-shaped light source image on the plane I from the captured image of the rod-shaped light source 3 is calibrated by calibrating the image by placing the scale parallel to the y-axis (s-axis) and passing through the origin O. It is easy to find (s, t).

  In the above arrangement, when the coordinates V (s, t) on the plane I are given from the image of the steel plate 1, the longitudinal inclination of the steel plate 1 with respect to the horizontal plane is determined by the contact at the point P1 on the steel plate 1. This is to obtain the inclination in the y direction of the plane. If the tangent plane of the steel plate 1 at the point P1 is expressed as in equation (1), this corresponds to obtaining the inclination in the y direction q. If the slope q is obtained, an elongation difference representing the shape of the steel sheet 1 can be derived by the procedures (a), (b), and (c) described above.

Hereinafter, a method for deriving the tangent plane parameters p, q, and r will be described.
The relational expression between the tangent plane parameter p, q, r in the equation (1) and the point V (s, t) on the plane I indicates that the ray entering the camera position Q (xq, 0, zq) is Q → V → P1. → By tracing in the reverse direction as in P2, it is obtained as follows.

  First, a point V (s, t) on the plane I is expressed as V (xv, yv, zv) in the coordinates of the three-dimensional coordinate system. The relationship between (xv, yv, zv) and (s, t) is expressed by equation (2) using a known coordinate value of the position Q (xq, 0, zq).

Then, a point as an intersection of the straight line QV connecting the camera position Q (xq, 0, zq) and the point V expressed by the equation (2) and the tangent plane (parameter p, q, r) of the equation (1). The coordinates (x1, y1, z1) of P1 are related.

By the way, a vector W toward the light source opposite to the incident direction is obtained from the direction vector of the straight line QV and the normal vector of the tangent plane (represented by parameters p, q, r). In addition, the incident light to the steel plate 1 passes through P1 and becomes a straight line having a direction vector (−W). As an intersection of this straight line and a plane parallel to the yz plane including the rod-shaped light source represented by Expression (3), P2 (−xl,
y2, z2) is required.

  The y2 and z2 obtained in this way are functions of the tangential plane parameters p, q, r, but since the rod-like light source 3 is located at y = 0, the y coordinate y2 of P2 is also zero. Therefore, p, q, r must satisfy equation (4).

Expression (4) is a conditional expression equivalent to q = 0 only when s = 0, and represents a conditional expression that there is no inclination in the y direction when the virtual image is at the center of the screen. In the case of s ≠ 0, there are an infinite number of pairs of p, q, r that satisfy this condition, and any point on the curved surface represented by Expression (4) in the (p, q, r) space. That is, there are two independent variables in p, q, and r.

  FIG. 5 shows an example in which equation (4) is illustrated in the (p, q, r) space. This is a calculation example when the camera 4 is at the position of the point Q (xq = 4000mm, zq = 850mm), the position of the rod-shaped light source 3 (xl = 3200mm), and the position of the point V (s = 10mm, t = 0mm) It is.

  As can be understood from the above description, in the optical shape measuring method of the method of observing the light source image reflected on the steel plate 1, the deviation amount (represented by s and t) from the reference position of the image and the steel plate 1 There is no one-to-one correspondence between the longitudinal inclinations q of the plates, and the inclination q in the longitudinal direction of the plate cannot be obtained without any assumptions or additional information.

<Comparison example that is a prior art>
In the conventional method disclosed in Patent Document 2 and the like, this is equivalent to calculation assuming that the inclination p in the width direction and the vertical movement component r are zero. As an example, in the same camera / light source arrangement as in FIG. 4, the plate is a plane equivalent to equation (1), the longitudinal inclination q is 0.1, and p = 0, q = 0.1, r = 50mm lifted 50mm from the reference position In this case, assuming that the inclination p in the width direction and the vertical movement component r are 0 (p = 0, r = 0), the equation (4) is solved to obtain the plate width direction distribution of q in FIG. Show. It can be seen that there is an error with respect to the true value of 0.1 when p = 0 and r = 0, which corresponds to the conventional example.

<Data Processing Method in Optical Shape Inspection Apparatus of the Present Invention>
On the other hand, in this embodiment, as described below, the longitudinal position information of the rod-shaped light source 3 is used as the additional information. That is, the z-direction position z2 on the rod-shaped light source 3 corresponding to a certain image position (s, t) on the plane I is also a function of p, q, r, and a color changed in the longitudinal direction of the rod-shaped light source 3 is attached. Assuming that the measured value C is obtained by means such as, equation (5) is established, and this is an equation that defines a curved surface in the (p, q, r) space, as in equation (4).

  Therefore, the true values of p, q, and r are on the intersection line of equations (4) and (5). Therefore, assuming that the vertical motion component r of the steel sheet 1 is zero and substituting r = 0 in Equation (4) and Equation (5), p and q are solved by simultaneously solving Equation (4) and Equation (5). Can be requested. FIG. 7 shows two curved surfaces when C = 0 in the equations (4) and (5) under the same conditions as in FIG. As you can see, the intersecting line of the two curved surfaces is almost perpendicular to the q axis, so even if the assumption of r = 0 deviates from the true value, the error due to it is mainly the error of p. Since it appears, q can be obtained with high accuracy. FIG. 8 shows the distribution of q in the plate width direction when z2 is calculated under the same conditions as in FIG. FIG. 8 shows that the calculated value and the true value are almost overlapped.

In this example, a specific numerical example was examined. However, a practical range (| p | <0.2, | q | <0.2, 0 <
It was confirmed by numerical calculation that the accuracy of q is greatly improved when z2 is obtained at r <200mm).

<Form of Light Source in the Present Invention>
In order to measure z2, there is a method of observing a virtual image with the camera 4 comprising a color camera by changing the emission color along the z direction of the rod-shaped light source 3. In order to change the emission color in the z direction, for example, red and green LEDs are arranged in the z direction, mixed by a white translucent diffuser arranged in close proximity, and the brightness of the LED is changed in the z direction. You can use the method of changing with. If the red emission intensity is Ir (z), the green is Ig (z), and the maximum value of z, that is, the upper end of the rod-like light source 3 is set to zmax, the emission intensity is given as in equation (6).

  If Ir and Ig can be measured with a color camera, z2 can be measured from the ratio of Ir and Ig using equation (7).

  As another method for measuring z2, z2 may be specified by scanning the light emitting portion of the rod-like light source 3 in the longitudinal direction and taking an image using the camera 4 capable of high-speed imaging. Specifically, at time i, only a part centered on z = zi on the rod-shaped light source 3 is caused to emit light, and the measured value of z2 corresponding to the virtual image photographed at time i may be zi. This method has the problem that the full width in the plate width direction cannot be measured at the same time, and should be used according to the application.

For example, when the conveying speed is 1000 m / min (16.7 m / sec) in the rolling line of the steel plate 1, 60 times per second can be taken with a normal color camera, so the longitudinal measurement pitch Ls is 16.7.
(m / sec) / 60 (times / sec)
= 0.28m, which is a practically sufficient value, but there is a problem that it is costly to produce a high-intensity and long-life multicolor light source. On the other hand, when scanning the light emitting unit, a high-speed camera with a frame rate several times to 10 times is required when measuring at the same pitch, but there is an advantage that the light source needs only a single color.

<Data processing in shape calculation unit>
Based on the calculation described above, the shape calculation unit 5 calculates the longitudinal inclination q (i) at each point i in the width direction of the steel sheet 1 from V (s, t) and z2 based on the image measured by the camera 4. It is required with high accuracy. Subsequently, the shape calculation unit 5 performs shape parameter calculation according to the following procedure.
(A) From the measurement pitch Ls obtained by multiplying the conveyance speed of the steel plate 1 by the shooting time interval, the hypotenuse length Ld (i) at each point i in the width direction is expressed as Ls × √ (1 + q (i) ² ) Ask.
(A) Repeat this several times to 10 times and accumulate Ld (i) to obtain the length L (i) along the surface of the plate at each point i in the width direction.
(C) With L (imin) being the smallest of L (i) as a reference, the elongation difference Δεi at each point in the width direction is expressed as L (imin) It is obtained by dividing by, and this is output to a display or the like. Shape parameters such as wave heights other than the elongation difference Δεi may be derived based on the L (i).

  In the present embodiment, a steel plate is taken as an example of the plate material, and the optical shape inspection apparatus and method in the arrangement when the steel plate is transferred in the horizontal direction have been described. As a plate material, a metal plate material such as a steel plate is a strip-shaped body having a sufficiently smooth surface property for obtaining a reflection image of a rod-shaped light source from a book, and is also an application target of the present invention. Or, in the manufacturing process in which the plate material is transferred in a direction other than the horizontal direction, it is obvious that the optical surface inspection apparatus and method of the present invention may be applied by replacing the reference plane in the above description with the plate material transfer direction. It is. In addition to the camera, a known imaging device having the above-described performance may be used.

  Further, the data processing in the shape calculation unit is based on processing for extracting (s, t) and z2 by performing image processing and extracting (s, t) and z2 for the image collected by the imaging means, and based on these detection values. Thus, the process of deriving a desired shape parameter may be executed by a computer.

It is a figure which shows the outline of one Embodiment of this invention. It is a principle figure which calculates | requires the length along the steel plate surface from the longitudinal direction inclination of a steel plate. It is a figure which shows the change of a virtual image when a steel plate inclines to a longitudinal direction. It is a figure explaining the coordinate system of a camera, a steel plate, and a rod-shaped light source. It is the figure which illustrated the curved surface of Formula (4). It is a figure which shows the example which a measurement error generate | occur | produces by the conventional method. It is the figure which illustrated the curved surface of Formula (4) and Formula (5) in piles. It is a figure which shows the example which a measurement error reduces by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Steel plate 2 ... Roll 3 ... Bar light source 4 ... Camera 5 ... Shape calculating part 6 ... Point q on bar light source ... Longitudinal inclination of plate
Ls: Longitudinal measurement pitch
Ld: Oblique side length L ... Length along the surface of the plate O ... Origin Q of the three-dimensional coordinate system ... Camera position P1 ... Reflection position P2 of the rod-shaped light source image on the steel plate shape ... Position on the rod-shaped light source corresponding to the virtual image position p: inclination in the width direction of the steel sheet r: vertical position of the steel sheet

Claims (8)

Optically detecting the shape of the plate material by irradiating the plate material to be conveyed with light emitted from the rod-shaped light source and continuously collecting virtual images of the rod-shaped light source reflected on the plate material surface as images. In the shape detection device,
The rod-shaped light source is disposed perpendicular to the conveying direction and the width direction of the plate material on the side of the plate material, and has means for adding longitudinal position information of the rod-shaped light source to the emitted light,
An optical shape detection device comprising: a shape calculation unit that calculates the shape of the plate material based on the image including the position information in the longitudinal direction of the rod-shaped light source. The means for adding the longitudinal position information of the rod-shaped light source is to change the emitted light color in the longitudinal direction of the rod-shaped light source,
The optical shape inspection apparatus according to claim 1, wherein the imaging unit is a color camera. The means for adding the longitudinal position information of the bar light source scans the light emission position of the bar light source in the longitudinal direction of the bar light source as time changes,
The optical shape detection apparatus according to claim 1, wherein the imaging unit is capable of high-speed imaging capable of identifying the light emission position with a predetermined accuracy. Based on the position of each point A in the rod-shaped light source and the position of the point B of the image of the rod-shaped light source corresponding to each point A, the shape calculating unit Calculate the longitudinal slope,
The optical shape detection device according to any one of claims 1 to 3, wherein the shape of the plate material is calculated based on a longitudinal inclination of the steel plate at each point C of the plate material. An optical system for detecting the shape of the plate material by irradiating the plate material to be conveyed with light emitted from the rod-shaped light source and capturing a virtual image of the rod-shaped light source reflected on the plate material surface with an imaging means. In the automatic shape detection method,
The rod-shaped light source is disposed beside the plate material in a direction perpendicular to the conveying direction and the width direction of the plate material, and has means for adding longitudinal position information of the rod-shaped light source to the emitted light,
An optical shape detection method, wherein a shape of a plate material is derived by a predetermined calculation based on the image including longitudinal position information of the rod-shaped light source. The means for adding the longitudinal position information of the rod-shaped light source is to change the emitted light color in the longitudinal direction of the rod-shaped light source,
The optical shape inspection method according to claim 5, wherein the imaging unit is a color camera. The means for adding the longitudinal position information of the rod-shaped light source scans the emission position of the rod-shaped light source in the longitudinal direction as time changes,
The optical shape detection method according to claim 5, wherein the imaging unit is capable of high-speed imaging capable of identifying the light emission position with a predetermined accuracy. The predetermined calculation is based on the position of each point A in the rod-shaped light source and the position of the point B of the image of the rod-shaped light source corresponding to each of the points A. Calculate the longitudinal slope,
The optical shape detection method according to any one of claims 5 to 7, wherein the shape of the plate material is calculated on the basis of the inclination in the longitudinal direction of the steel plate at each point C of the plate material.

Images