JPH0961124A - Dimension measuring device of rod steel with screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure the screw dimension of a work such as total screw PC steel rod running in a rolling line. SOLUTION: A dimension measuring device has a strobo 3 opposing a work W and a camera 2 for picking up the image of the work W for the emission of strobo, binarizes the image picked up by the camera 2, and calculates the screw dimension of the work from the binary image. In that case, an infrared ray cut filter 4 is provided in front of the camera.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for measuring the dimensions of a steel bar with a thread (such as a fully threaded PC steel bar). In particular, it relates to an apparatus and method for measuring dimensions in-line during rolling.

[0002]

2. Description of the Related Art The following is known as a technique related to the measurement of the dimension of a screw surface. The probe is brought into contact with the surface of the screw to be inspected, and the dimensions are measured (see JP-A-61-45901 and JP-A-1-47503). Parallel light is radiated onto the screw surface from an oblique direction, the image is taken with a camera, and the screw thread is inspected from the brightness distribution of the image (visual inspection automation technology: January 1987, published by Nikkan Kogyo Shimbun, written by Yoji Marutani. ).

[0003]

However, the contact-type technique using the measuring element cannot be applied when the inspection object moves at high speed on the manufacturing line. In particular, in order to measure the dimensions of an inspection object (such as a total screw PC steel bar) that is continuously formed by hot rolling, it is necessary to cut out the formed inspection object, cool it, and then measure it. Therefore, it takes time to adjust the position of the rolling roll, and the production efficiency is reduced. In addition, even with the technology using parallel light, when the inspection target moves at high speed,
The image may be blurred. In particular, when the inspection object itself emits light (for example, red heat of a steel rod), it is difficult to obtain a clear brightness distribution in an image of reflected light of parallel light, and the state of the screw surface cannot be accurately grasped. Therefore, there is a problem that it cannot be applied to accurate dimension measurement.

[0004]

In order to solve such a problem, the present invention improves the technique of capturing an image of an object to be inspected (such as a steel bar with a screw) and measuring the dimensions from the image, and a manufacturing line for the object to be inspected. Above all, it is configured so that the dimensions can be accurately measured. That is, the device of the present invention comprises a strobe facing a steel bar with a screw, a camera for imaging the steel bar with a screw according to the light emission of the strobe, a means for binarizing an image captured by the camera, and a dimension of the screw from the binarized image. It is characterized by comprising means for calculating.

The camera is fixed at the boundary between the inspection object and the background in the image so that the unevenness state of the inspection object is displayed. It is preferable that the camera and the strobe face each other.
A projected image can be obtained by moving the inspection object between the two. When the inspection target emits light, a filter that cuts light of a specific wavelength in the light is attached to the camera. At that time, the strobe light has a wavelength that is not cut by this filter. For example, if the inspection target is red hot, the camera is equipped with an infrared cut filter, and the strobe light has a wavelength containing a large amount of ultraviolet rays. Specifically, the emission wavelength having a peak at 350 to 500 nm is preferable. If one camera cannot capture the screw surface, a plurality of cameras may be installed. By arranging the camera and strobe on the rolling line for threaded steel bar, the dimension of threaded steel bar can be measured inline. Also,
According to the method of the present invention, a steel bar with a screw traveling at a speed of 3.0 m / s or more is imaged by a camera according to the light emission of a strobe, the imaged image is binarized, and the binarized image is obtained. It is characterized in that the dimensions of the screw are calculated from.

[0006]

[Function] By capturing an image with strobe light emission,
The image is not blurred even when the inspection target is moving at high speed. In addition, a projection image can be obtained by causing the strobe and the camera to face each other and running the inspection target therebetween. In particular, even when the inspection target emits red heat and emits red light, an image with high contrast can be obtained by using the infrared cut filter. Therefore, in the image captured by the camera, the inspection target and the background can be clearly distinguished from each other, and highly accurate dimension measurement can be performed.

[0007]

EXAMPLES The present invention will be described below based on examples.
FIG. 1 is a schematic plan view showing a state in which the device of the present invention is installed on a rolling line for a work W (a total screw PC steel rod). The work W having the threaded surface formed by the rolling roller 1 is guided to the right in the figure, travels between the camera 2 and the strobe 3, and the dimensions are calculated based on the image captured by the camera 2. . First, the structure of the rolling roller 1 and the shape of the work W will be described.

As shown in FIG. 2, the rolling roller 1 comprises an upper roller 1A and a lower roller 1B, and ribs (corresponding to a screw surface) are formed on the upper and lower surfaces of the work W sandwiched between them. The outer peripheral surfaces of both rollers 1A and 1B are concave curved surfaces, and helical gear-shaped teeth are formed therein. Further, since the rotation axes of the upper and lower rollers are slightly displaced in the traveling direction of the work W, the ribs on the upper and lower sides of the work are formed out of phase, and these ribs function as male threads. On the other hand, the total screw P that is the work
The C steel rod 10 is provided with a rib 11 corresponding to the outer peripheral shape of the roller on the outer peripheral surface of the round steel rod (see FIG. 7). The threads (here, the rib 11) are not formed all around. That is, an arc-shaped rib that is inclined with respect to the axial direction
11 are divided into parallel positions on the outer circumference (upper and lower),
The upper and lower ribs 11 are out of phase.

In such a rolling line, the camera 1 is set in the direction (see FIG. 5A) in which the uneven state of the rib 11 is displayed at the boundary between the work W and the background in the image. A CCD camera was used as the camera 1. An infrared cut filter 4 was attached to the front of the camera lens. As a result, even if the work W emits red light due to red heat, an image with high contrast can be obtained. The strobe 3 was installed in front of the camera 1 with the work W interposed therebetween. In this example, an emission time of 4 to 10 μs and an emission wavelength of 350 to 1000 nm with a peak at 350 to 500 nm was used. By using the strobe 3,
Work that moves at high speed can be captured as a clear image without blurring.

In the dimension measurement, the camera 2 captures the work W at the time of strobe light emission as an image. At this time, the light from the strobe 3 is not cut by the infrared cut filter 4, and the work W is captured as a projected image with a substantially monochromatic background. Further, the work itself that glows red is also clearly caught by using the infrared cut filter 4, and an image in which the boundary between the work W and the background is clear can be obtained.

The obtained image is sent to the image processing device 5. The configuration of the image processing device 5 will be described with reference to FIG.
The image processing device 5 includes an image memory 6, a CPU 7, and an external I / O 8, controls the correspondence between imaging and strobe light emission, and performs calculation for dimension measurement. First, the image is captured in the memory 6 and binarized based on a threshold value preset by the processing device 5 or a threshold value automatically set by the processing device 5 based on the brightness of the image. This allows
The work and the background are clearly distinguished by black and white, for example. The boundary data between the work and the background is extracted from the binarized image. The image is represented by coordinates with one corner of the screen (for example, upper left) as the origin. The boundary data between the work and the background is recognized by, for example, examining the color (black and white) of each coordinate in order from the lower part of the screen toward the upper side and finding the change point. The change point is used as the starting point, and the brightness of each coordinate is checked in the left-right and up-down directions in sequence, and the set of change points found is used as boundary data. The extracted data is divided into three parts: the valley between ribs, the hypotenuse of the rib, and the top of the rib. Calculate the slope with the adjacent change point from several points before and after the boundary coordinate,
The part where a certain slope is continuous is recognized as the hypotenuse of the rib. The horizontal part where the inclination is close to 0 is the top or valley of the rib.
From the positive and negative of the slope, the horizontal part before and after it is distinguished whether it is a peak or a valley. Each divided data is approximated by the least square method. The hypotenuse part is not a straight line but a rather curved line, so it is approximated by a quadratic function, and the crests and valleys are horizontal lines, so a linear function is approximated. From this result, as shown in FIG. 4, a horizontal line located in the middle of the horizontal lines forming the crest and the valley is obtained, and the intersection between this horizontal line and the hypotenuse of the rib is obtained. Recognize as position. Also,
The position of the trough is obtained from the intermediate position of the adjacent ribs. Then, the pitch / diameter (peak diameter and valley diameter) of the ribs and the phase shift between the upper and lower ribs (phase shift between the upper and lower rollers) are calculated. The image captured by the camera 2 and the binarized image are displayed by switching on the monitor 9.

As described above, according to the present invention, it is possible to directly measure the material size while traveling on the rolling line. Therefore, it is not necessary to wait for the workpiece to cool before measuring.
In the above example, only one camera is used, but if the diameter of the work is large and one camera cannot capture the ribs above and below the work, two cameras 2 may be used (see FIG. 5). reference). In that case, two images are taken in, one at the top and one at the bottom, and the dimension measurement is processed by combining these. The image combination is based on one image and overlaps a part of the other image. Figure 6 shows the upper image 20 and the lower image
It is explanatory drawing which shows the state which overlapped a part of 21. here,
The X axis and Y axis of each image are divided into positions 0 to 512, the coordinates of the upper image 20 are (x1, y1), and the coordinates of the lower image 21 are (x
2, y2). In this case, if the x-coordinate shift amount of both images is Δx and the y-coordinate shift amount is Δy, the coordinates (X, Y) with the upper left of the upper image as the origin (0, 0) are expressed as follows. . Upper image X = x1 Y = y1 Lower image X = x2 + Δx Y = y2 + 512−Δy Therefore, the positions of the tops and valleys of the ribs calculated in each image are converted into the combined coordinates by the above procedure and calculated. , The dimensions of each part can be calculated. The present invention can be applied to materials other than the threaded steel bar as long as it is a long material having irregularities such as screw surfaces on the surface.

[0013]

As described above, according to the apparatus and method of the present invention, an object to be inspected moving at high speed can be captured as a clear image, and dimension measurement can be performed with high accuracy. In particular, the dimensions of the material running on the production line can be directly measured, and the production efficiency can be improved. Therefore, it becomes possible to guarantee the dimension of the entire length, which was difficult in the past.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing how the device of the present invention is used.

FIG. 2 is a sectional view showing the structure of a rolling roller.

FIG. 3 is a schematic explanatory view of the device of the present invention.

FIG. 4 is an explanatory diagram showing a procedure for calculating a rib position from image data.

FIG. 5 is a schematic explanatory view of the device of the present invention in which two cameras are installed.

FIG. 6 is an explanatory diagram showing a procedure for combining two images.

FIG. 7 shows a total screw PC steel rod to be inspected by the method of the present invention, where (A) is a front view and (B) is a cross-sectional view.
(C) is a plan view.

[Explanation of symbols]

1 Rolling roller 1A Upper roller 1B Lower roller 2 Camera 3 Strobe 4 Infrared cut filter 5 Image processing device 6
Image memory 7 CPU 8 External I / O 9 Monitor 10 Total screw PC Steel rod 11 Rib 20 Top image 21 Bottom image W Work

Claims (9)

[Claims] 1. A strobe facing a steel bar with a screw, a camera for imaging the steel bar with a screw according to the light emission of the strobe, a means for binarizing an image captured by the camera, and calculating the dimension of the screw from the binarized image. A dimension measuring device for a steel bar with a screw, comprising: 2. The dimension measuring device for a steel bar with a screw according to claim 1, wherein the camera is provided with an infrared cut filter. 3. The wavelength of strobe irradiation light is 350 to 500n.
The dimension measuring device for a steel bar with a screw according to claim 2, wherein m has a peak. 4. The dimension measuring device for a steel bar with a screw according to claim 1, wherein a plurality of cameras are provided so that a screw surface of the steel bar with a screw can be captured as an image. 5. The dimension measuring device for a threaded steel bar according to claim 1, wherein a camera and a strobe are arranged on a rolling line for the steel bar with a thread. 6. The dimension measuring device for a steel bar with a screw according to claim 1, wherein the camera and the strobe are opposed to each other. 7. A binarized image obtained by imaging a rod-shaped steel bar running at a speed of 3.0 m / s or more with a camera in accordance with the flash light emission, binarizing the imaged image, and binarizing the image. Measuring method of steel bar with screw to calculate the dimension of screw. 8. The method for measuring the dimensions of a threaded steel bar according to claim 7, wherein the threaded steel bar is in a state of being red-heated. 9. The method for measuring the dimensions of a threaded steel bar according to claim 7, wherein a strobe and a camera are opposed to each other, and a steel bar with a thread is run therebetween.