CN111650392A - Detection method of metal plate motion speed based on line scan camera stereo vision - Google Patents

Abstract

The present invention provides a method for detecting the motion speed of a metal plate based on the stereo vision of a line scan camera, which comprises the following steps: based on the movement of the metal plate to be measured, acquiring the surface of the metal plate to be measured at different positions through a plurality of line scan cameras image; determine the position difference of any pixel position on the surface of the metal sheet to be tested in the images collected by the two line scan cameras through stereo matching; combine the sampling line frequency set by the line scan cameras to realize the metal sheet to be tested Real-time detection of motion speed. The invention is suitable for the real-time detection of the movement speed of the metal plate, so that the surface image of the plate collected by the area array camera is not missing, the surface image of the plate collected by the line array camera is not distorted, and the positioning of the surface defect of the metal plate is more accurate.

Description

Detection method of metal plate motion speed based on line scan camera stereo vision

technical field

The present invention relates to the technical field of speed detection methods, in particular, to a method for detecting the movement speed of a metal plate based on the stereo vision of a line scan camera.

Background technique

Surface defects of sheet metal have an important influence on the quality of sheet metal strips. Affected by raw materials, rolling process, system control and other factors, surface defects of metal sheets, such as cracks, scratches, roll marks, scarring, inclusions, etc., not only affect the wear resistance, fatigue resistance, corrosion resistance and corrosion resistance of metal sheets. Electromagnetic characteristics have varying degrees of influence, and may also cause serious accidents such as belt breakage and parking during production, resulting in inestimable economic and brand losses to production enterprises. Therefore, manufacturers in various countries attach great importance to the detection of the surface quality of metal sheets, and spend huge sums of money to improve the detection technology and improve the detection level.

On-line detection technology of metal sheet surface defects based on machine vision is an important advanced means and technology for surface quality monitoring of metal sheet production lines. On-line inspection based on machine vision can perform real-time, full-continuous, and full-coverage metal surface quality inspection, which has attracted wide attention from production enterprises and has been widely used. There are mainly two methods for detecting surface defects of metal sheets based on machine vision. One is the method of using an area scan camera combined with a surface light source, and the other is a method of using a line scan camera combined with a linear light source. No matter which method is used, when using the camera to image the metal surface, it is necessary to match the image acquisition speed with the movement speed of the metal plate, otherwise it will affect the acquisition of the surface image of the steel plate: for the area scan camera, the mismatch of the movement speed will lead to There are missing or overlapping plate surface images between adjacent frame images; for line scan cameras, the mismatch of motion speeds will lead to inconsistent spatial resolution of plate surface images in the direction of motion, resulting in image distortion.

Aiming at the problem that the surface image of the metal sheet needs to be strictly matched with the moving speed of the sheet, the current method for obtaining the moving speed of the sheet is to use an encoder installed on the conveying roller of the metal sheet. However, due to the slippage between the conveying roller and the metal plate, the method of obtaining the conveying speed of the metal plate by using the encoder on the conveying roller is not accurate enough.

SUMMARY OF THE INVENTION

According to the above technical problem that the method of using the encoder on the conveying roller to obtain the conveying speed of the metal plate is insufficient due to the slippage between the conveying roller and the metal plate, a metal plate based on the stereo vision of a line scan camera is provided. The motion speed detection method is characterized in that, comprises the following steps:

Step S1: based on the motion of the metal plate to be tested itself, acquire surface images of the metal plate to be tested at different positions through a plurality of line scan cameras;

Step S2: determining the pixel position difference of any point on the surface of the metal plate to be tested in the images collected by the two line scan cameras through stereo matching;

Step S3: Real-time detection of the movement speed of the metal plate to be measured is realized in combination with the sampling line frequency set by the line scan camera.

Further, a plurality of the line scan cameras are arranged on the same surface of the metal plate to be tested.

Further, the position of the field of view of the plurality of line scan cameras on the surface of the metal plate to be tested is different.

Further, the line scan camera is a common line scan camera or a time-lapse integrating line scan camera.

Further, the position difference of any pixel position of the surface of the metal sheet to be tested in the images captured by the two line scan cameras is determined by stereo matching, and the calculation method for the motion speed of the metal sheet to be tested is:

V=Pf/S;

Wherein, V represents the moving speed of the metal plate to be measured, P represents the field of view distance of the line scan camera on the surface of the metal plate to be measured, f represents the sampling line frequency of the line scan camera, and S represents any point on the surface of the metal plate Differences in pixel positions in the images are collected between the line scan cameras after stereo matching.

Compared with the prior art, the present invention has the following advantages:

The invention is suitable for the real-time detection of the moving speed of the metal plate, so that the surface image of the plate collected by the area array camera is not missing, the surface image of the plate collected by the line array camera is not distorted, and the positioning of the surface defect of the metal plate is more accurate.

Description of drawings

In order to illustrate the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description These are some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can also be obtained from these drawings without any creative effort.

FIG. 1 is a schematic diagram of the arrangement of the camera of the present invention. Among them, (a) is the line scan camera angle of view parallel; (b) the line scan camera angle of view is opposite; (c) the line scan camera angle of view is opposite.

FIG. 2 is a schematic diagram of the mode of cooperation between the light source and the camera according to the present invention. Among them, (a) the position of the field of view is close, and the light source is shared; (b) the position of the field of view is far away, and the light source is independent.

Detailed ways

In order to make those skilled in the art better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only Embodiments are part of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

It should be noted that the terms "first", "second" and the like in the description and claims of the present invention and the above drawings are used to distinguish similar objects, and are not necessarily used to describe a specific sequence or sequence. It is to be understood that the data so used may be interchanged under appropriate circumstances such that the embodiments of the invention described herein can be practiced in sequences other than those illustrated or described herein. Furthermore, the terms "comprising" and "having" and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those expressly listed Rather, those steps or units may include other steps or units not expressly listed or inherent to these processes, methods, products or devices.

As shown in Figures 1-2, the present invention provides a method for detecting the motion speed of a metal plate based on the stereo vision of a line scan camera. The basic principle is to use the motion of the metal plate itself. In this application, two line scan cameras are used. Take an example to describe it accordingly. First, based on the motion of the metal sheet to be tested, two line scan cameras with different viewing angles are used to obtain two-dimensional scanning images of the surface of the metal sheet, and then the two-dimensional images of the two different viewing angles are matched to obtain any point on the surface of the metal sheet. The time difference in the two-dimensional images of different viewing angles is finally combined with the sampling line frequency set by the line scan camera to realize the real-time detection of the movement speed of the metal sheet.

Determine the pixel position difference of any point on the surface of the metal sheet to be tested in the images collected by the two line scan cameras through stereo matching. The calculation method for the motion speed of the metal sheet to be tested is as follows:

V=Pf/S;

Wherein, V represents the moving speed of the metal plate to be measured, P represents the field of view distance of the line scan camera on the surface of the metal plate to be measured, f represents the sampling line frequency of the line scan camera, and S represents any point on the surface of the metal plate The position difference in the images is collected between the line scan cameras after stereo matching.

In Figure 1, the arrangement of the two line scan cameras can be parallel, opposite or opposite, and the two line scan cameras have different positions of the field of view on the surface of the metal plate.

In Figure 2, according to different camera arrangements, the light source can be used to fill the surface of the plate to improve the image quality: 1) When the two line scan cameras have basically the same field of view position on the metal surface, use the same LED strip, The linear light source or laser light source is projected perpendicular to the movement direction of the metal plate; 2) When the field of view of the two line scan cameras on the metal surface is different, regardless of whether the two line scan cameras are facing opposite or opposite, choose to use two independent Light source, independent light source adopts LED strip, line light source or laser light source. Each viewing angle line scan camera is matched with a group of independent light sources, and each group of independent light sources is projected to the metal surface along the imaging plane of the line scan camera matched with it.

In the present application, the two line scan cameras are arranged on the same surface of the metal plate to be tested. And the position of the field of view of the line scan camera on the surface of the metal plate to be tested is different.

Meanwhile, in this application, the line scan camera is a common line scan camera or a time-lapse integrating line scan camera.

The above-mentioned serial numbers of the embodiments of the present invention are only for description, and do not represent the advantages or disadvantages of the embodiments.

In the above-mentioned embodiments of the present invention, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments. In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. The apparatus embodiments described above are merely illustrative.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The technical solutions described in the foregoing embodiments can still be modified, or some or all of the technical features thereof can be equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present invention. scope.

Claims (5)

1. a metal plate motion speed detection method based on line scan camera stereo vision, is characterized in that, comprises the following steps: S1: Based on the movement of the metal sheet to be tested itself, acquire surface images of the metal sheet to be tested at different positions through a plurality of line scan cameras; S2: Determine the pixel position difference of any point on the surface of the metal plate to be tested in the images collected by the two line scan cameras through stereo matching; S3: Real-time detection of the movement speed of the metal sheet to be measured is realized in combination with the sampling line frequency set by the line scan camera. 2 . The method for detecting the motion speed of a metal sheet based on stereo vision of a line scan camera according to claim 1 , wherein a plurality of the line scan cameras are arranged on the same surface of the metal sheet to be tested. 3 . 3 . The method for detecting the motion speed of a metal sheet based on the stereo vision of a line scan camera according to claim 1 , wherein the position of the field of view of the plurality of line scan cameras on the surface of the metal sheet to be measured is different. 4 . 4 . The method for detecting the motion speed of a metal sheet based on the stereo vision of a line scan camera according to claim 1 , wherein the line scan camera is an ordinary line scan camera or a time-delay integral line scan camera. 5 . 5. The method for detecting the motion speed of sheet metal based on line scan camera stereo vision according to claim 1, wherein: Determine the pixel position difference of any point on the surface of the metal sheet to be tested in the images collected by the two line scan cameras through stereo matching. The calculation method for the motion speed of the metal sheet to be tested is as follows: V=Pf/S; Wherein, V represents the moving speed of the metal plate to be measured, P represents the field of view distance of the line scan camera on the surface of the metal plate to be measured, f represents the sampling line frequency of the line scan camera, and S represents any point on the surface of the metal plate Differences in pixel positions in the images are collected between the line scan cameras after stereo matching.

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