CN218788002U

CN218788002U - Surface defect detection system and surface detection production line

Info

Publication number: CN218788002U
Application number: CN202222620856.1U
Authority: CN
Inventors: 曹文; 龙攀城; 丁玲玲; 付翱
Original assignee: Mecarmand Shanghai Robot Technology Co ltd
Current assignee: Mecarmand Shanghai Robot Technology Co ltd
Priority date: 2022-09-29
Filing date: 2022-09-29
Publication date: 2023-04-04
Anticipated expiration: 2032-09-29

Abstract

The utility model provides a surface defect detecting system, surface defect detecting method and surface detection produce the line, wherein surface defect detecting system includes bearing structure, image acquisition device and a plurality of light source. The bearing structure is used for supporting the detected surface, and the image acquisition device can move relative to the bearing structure or the detected surface in a preset path. The light source can be independently controlled to be turned on or turned off and is fixed relative to the image acquisition device, the light source is controlled to irradiate the bearing structure at different incidence angles, a strip-shaped irradiation range can be formed, and the irradiation ranges of the light sources on the bearing structure are overlapped. The embodiment of the utility model discloses a can reflect comprehensively and be detected the characteristic on surface, a plurality of light sources shine at same position with the angle of incidence of difference, can make image acquisition device acquire the reverberation of enough intensity, provide the hardware basis for improving surface defect detection method, can be applied to mirror surface or half mirror surface defect and detect.

Description

Surface defect detection system and surface detection production line

Technical Field

The utility model belongs to the technical field of the work piece surface detection technique and specifically relates to a surface defect detecting system, surface defect detecting method and surface detection production line.

Background

For a workpiece with a high-precision machining requirement, the surface of the workpiece needs to be detected before subsequent machining or delivery from factory to judge whether the surface of the workpiece has defects such as spots, bulges, pits, scratches, chromatic aberration and the like, which is a necessary process for judging whether the workpiece is qualified.

The existing method for detecting surface defects by using machine vision mainly comprises the steps of shooting the surface of a workpiece by using a 2D camera or a 3D camera, judging whether the surface of the workpiece has defects or not by using a specific algorithm according to the acquired image characteristics, and determining the type and the position of the surface defects. However, the existing surface defect detection system mainly utilizes a halcon algorithm library (a machine vision algorithm library), which is a calculation method based on a lambertian illumination mathematical model, and according to the principle of the lambertian illumination mathematical model, the brightness of the surface under all viewing angles is limited to be the same, the characteristic requires that the light source is set to be a parallel light source or an infinite point light source, and the camera is set to have an optical axis perpendicular to the detected surface.

The statements in the background section are merely prior art as they are known to the inventors and do not, of course, represent prior art in this field.

SUMMERY OF THE UTILITY MODEL

To one or more defect among the prior art, the utility model provides a surface defect detecting system, include:

a load bearing structure for supporting a surface to be inspected;

an image acquisition device configured to be capable of relative movement with the load bearing structure or the inspected surface in a predetermined path; and

the light sources can be independently controlled to be turned on or off and are fixed relative to the image acquisition device; the light sources are controlled to irradiate the bearing structure at different incidence angles and are configured to form a strip-shaped irradiation range, and the irradiation ranges of the light sources on the bearing structure are overlapped; the irradiation range of the light source is positioned in the visual field range of the image acquisition device.

According to an aspect of the present invention, wherein the optical axis of the image capturing device is directed to a plurality of the light sources are in the carrying structure or the strip-shaped irradiation range formed on the detected surface.

According to an aspect of the present invention, the carrying structure comprises a driving unit, the driving unit drives the detected surface to move along a preset path; the image acquisition device and the light source are fixedly arranged.

According to an aspect of the present invention, wherein the preset path of the detected surface includes:

translating in a first direction along a plane of the load bearing structure; and

when the detected surface moves along the first direction and the second direction, the strip-shaped illumination range of the light source on the detected surface is approximately vertical.

According to an aspect of the present invention, the surface defect detecting system further includes a control system, the control system with the image obtaining device with the light source communication is configured to be able to control the difference respectively the light source is opened or closed with a predetermined frequency and a time sequence.

According to an aspect of the present invention, wherein the optical axis direction of the image capturing device is substantially perpendicular to the long side direction of the strip-shaped irradiation range formed by the light source;

the detected surface is divided into a first side and a second side by taking a normal direction as an interface, the light sources are divided into a first light source group and a second light source group, and the first light source group and the second light source group are respectively arranged on the first side and the second side of the detected surface.

According to an aspect of the present invention, wherein the first light source group comprises a bar light source, the bar light source side illuminates to the bearing structure with an incident angle not less than 75 °.

According to an aspect of the present invention, the second light source group comprises at least three bar light sources, and the bar light sources irradiate the same position of the bearing structure at different incident angles; the strip light source with the largest incident angle in the three strip light sources of the second light source group is laterally irradiated to the bearing structure at the incident angle not less than 75 degrees.

According to the utility model discloses an aspect, wherein second light source group includes at least three bar light source, three bar light source is in be parallel and even setting in the predetermined incident angle within range of the second side of detected surface.

According to an aspect of the utility model, surface defect detecting system still includes second image acquisition device, second image acquisition device set up in be detected the first side on surface, just second image acquisition device's optical axis is directional a plurality of the light source is in bearing structure or be detected the strip irradiation range that forms on the surface.

According to an aspect of the utility model, wherein the image acquisition device with bearing structure is less than at its ascending distance of optical axis direction the second image acquisition device with bearing structure is at its ascending distance of optical axis direction.

According to the utility model discloses an aspect, with the extending direction of first side is 0 orientation, image acquisition device's optical axis direction is 30-95 with the contained angle value scope of 0 orientation to it is adjustable in this angle range.

According to an aspect of the present invention, wherein an angle between an incident direction of the first light source group and a normal direction of the detected surface is 75 to 87 degrees; the range of the included angle between the incident direction of the second light source group and the normal direction of the detected surface is 10-87 degrees.

According to an aspect of the present invention, wherein the distance between the image capturing device and the carrying structure in the direction along the optical axis is 750-850 mm.

According to an aspect of the present invention, the distance between the first light source group and the bearing structure in the irradiation direction is 600-1000 mm; the second light source group at least comprises three strip-shaped light sources which are independently controlled, and the distance between the three strip-shaped light sources and the bearing structure along the irradiation direction is 600-1000 mm.

According to the utility model discloses an aspect, wherein a plurality of bar light sources in the second light source group with bearing structure is along the ascending distance in the irradiation direction equal.

According to the utility model discloses an aspect, wherein the second image acquisition device set up in be detected the first side on surface, the optical axis direction of second image acquisition device with be detected the normal direction of surface and be 25-60 at the contained angle value range of first side.

According to an aspect of the present invention, wherein the distance between the second image capturing device and the carrying structure along the optical axis direction thereof is 940-1040 mm.

According to an aspect of the present invention, wherein the image capturing device is a 16K line scan camera; the second image acquisition device is an 8K line scan camera.

According to an aspect of the utility model, the utility model discloses still include a surface defect detection method, use as before surface defect detecting system, surface defect detection method includes:

respectively acquiring incident angles of a plurality of light sources and angles of an optical axis of an image acquisition device relative to a detected surface;

acquiring images of the detected surface under the irradiation of different light sources, and acquiring a gray value corresponding to the light source of the irradiated part in the detected surface according to the images corresponding to the different light sources;

calculating a surface normal vector and/or glossiness of the irradiated part in the detected surface according to the gray value, the incident angle of the corresponding light source and the angle of the optical axis of the image acquisition device relative to the detected surface;

calculating the curvature of the irradiated part in the detected surface according to the surface normal vector;

and judging the surface defects of the detected surface according to the curvature and/or glossiness of the irradiated part in the detected surface.

According to the utility model discloses an aspect, wherein the incident angle of a plurality of light sources to and image acquisition device's optical axis is obtained through demarcating surface defect detecting system for the angle that is detected the surface.

According to an aspect of the utility model, the utility model discloses still include a production line of surface detection, the production line of surface detection includes: a surface defect detection system as hereinbefore described.

Compared with the prior art, the embodiment of the utility model provides a surface defect detecting system, utilize a plurality of light sources to form the strip irradiation range of coincidence on being detected the surface, with the incident angle of difference shine at load-bearing structure's same position, after the image of this position has been acquireed, through the processing analysis to the image, the incident angle who combines the light source and the optical axis angle of image acquisition device, the completion is to the surface defect detection who is detected the surface, the restriction to hardware setting mode has been reduced, the hardware basis has been provided for improving surface defect detection method, can reflect the characteristics and the position that are detected the surface's middle surface defect more accurately, can be applied to the defect detection on mirror surface or half mirror surface. The utility model discloses still include the embodiment of a surface defect detection method, utilize aforementioned surface defect detecting system to carry out surface defect and detect, can improve the detection accuracy to can be applied to specular reflection or half specular reflection surface. The utility model discloses still include the embodiment of a surface detection production line, wherein include aforementioned surface defect detecting system.

Drawings

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and together with the description serve to explain the invention and not to limit the invention. In the drawings:

fig. 1 is a schematic perspective view of a surface defect detection system in an embodiment of the present invention;

fig. 2 is a schematic side view of a surface defect detection system in an embodiment of the present invention;

fig. 3 is a schematic view of a movement path of the object to be detected driven by the carrying structure according to an embodiment of the present invention;

fig. 4 is a block diagram of a surface defect detection system according to an embodiment of the present invention;

fig. 5 is a schematic structural diagram of an image capturing device according to an embodiment of the present invention;

fig. 6 is a schematic view of a surface to be inspected in an embodiment of the present invention;

fig. 7 is a timing diagram of a plurality of light sources in an embodiment of the invention;

fig. 8 is a schematic flow chart of a surface defect detection method according to an embodiment of the present invention.

Detailed Description

In the following, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and to simplify the description, but do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the present invention. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first" and "second" may explicitly or implicitly include one or more of the described features. In the description of the present invention, "a plurality" means two or more unless specifically limited otherwise.

In the description of the present invention, it should be noted that unless explicitly stated or limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection, either mechanically, electrically, or in communication with each other; they may be directly connected or indirectly connected through intervening media, or may be connected through the use of two elements or the interaction of two elements. The specific meaning of the above terms in the present invention can be understood according to specific situations by those skilled in the art.

In the present disclosure, unless expressly stated or limited otherwise, the first feature "on" or "under" the second feature may comprise direct contact between the first and second features, or may comprise contact between the first and second features not directly. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.

The following disclosure provides many different embodiments or examples for implementing different features of the invention. In order to simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. Furthermore, the present disclosure may repeat reference numerals and/or reference letters in the various examples for purposes of simplicity and clarity and do not in itself dictate a relationship between the various embodiments and/or arrangements discussed. In addition, the present disclosure provides examples of various specific processes and materials, but one of ordinary skill in the art may recognize the application of other processes and/or the use of other materials.

The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are presented herein only to illustrate and explain the present invention, and not to limit the present invention.

Fig. 1 illustrates a specific structure of a surface defect detection system 100 according to an embodiment of the present invention, which is described in detail below with reference to fig. 1.

As shown in fig. 1, the surface defect detecting system 100 includes a carrying structure 110, an image capturing device 120 and a plurality of light sources 130, wherein the carrying structure 110 is used for supporting the inspected article and making a surface of the inspected article face the image capturing device 120 and the light sources 130, and the surface is used as an inspected surface 200 in the surface defect detecting system 100. In this embodiment, the detected surface 200 and the image capturing device 120 can move relative to each other along a predetermined path, wherein the detected surface 200 and/or the image capturing device 120 can be configured to be driven by a driving unit (not shown) to move along the predetermined path. In the preferred embodiment of the present invention, the carrying structure 110 is a conveyor belt or a conveyor belt set, the detected object is fixed or directly placed on the conveyor belt, and the detected surface 200 faces upward, the image capturing device 120 and the light source 130 are fixed above the conveyor belt, so as to keep the position of the image capturing device 120 and the light source 130 stable, avoid generating deviation due to movement, affect the precision of the surface defect detecting system 100, meanwhile, the conveyor belt is used as the carrying structure 110, which is convenient for the current detected object to complete the detection, and quickly separate from the surface defect detecting system 100, and perform subsequent detection or processing, and perform surface detection on another detected object on the quick replacement. Of course, in other embodiments of the present invention, the bearing structure 110 may only provide a supporting and fixing function, and the object to be detected is placed on the bearing structure 110, while the image capturing device 120 and the light source 130 move along a predetermined path relative to the surface to be detected 200, for example, a sliding rail with a predetermined shape is provided.

In this embodiment, the image capturing device 120 may select a line scan camera, which is used to detect continuous materials, such as metal, plastic, paper, fiber, etc., and detect the entire surface thereof, in cooperation with a corresponding line scan lens. The specific type and resolution precision of the image capturing device 120 can be selected according to the detection precision requirement of the detected surface 200, for example, in a specific embodiment of the present invention, the image capturing device 120 selects the ML-HM-16K30H-00-R model 16K line scan camera of Teledyne dala brand, and is used in cooperation with the LS1626B model line scan lens of long-walkway brand. The image acquiring device 120 may further be configured with an image acquiring card to acquire the acquired image signal into the industrial control equipment, and store the acquired image signal on the hard disk in the form of a data file, so as to facilitate subsequent image processing. Specifically, the image acquisition card can be an OR-A8S0-PX840 image acquisition card of Teledyne DALSA brand.

As shown in fig. 1, the surface defect detecting system 100 includes a plurality of light sources 130, wherein the light sources 130 can be individually controlled to be turned on or off, and the light sources 130 can emit light sequentially or several light sources can emit light simultaneously according to a preset control program. In the present embodiment, the relative position of the light source 130 and the image capturing device 120 is fixed, and preferably, the light source 130 and the image capturing device 120 are both disposed at fixed positions of the surface defect detecting system 100, and the bearing structure 110 drives the object to be detected to move, and the direction of the detected surface 200 facing the light source 130 and the image capturing device 120 is maintained, so that the light source 130 is controlled to irradiate the bearing structure 110, and the irradiation range of the light source 130 on the bearing structure 110 is located within the visual field range of the image capturing device 120.

In the present embodiment, the light sources 130 illuminate the supporting structure 110 at different incident angles, and each of the light sources is capable of forming a strip-shaped illumination range on the supporting structure 110, for example, a plurality of lasers are arranged in the light sources 130 in a one-dimensional array, and a strip-shaped illumination range is formed after light is homogenized, or an optical element is arranged at the front end of the light source 130 to form a target light field. Preferably, the length of the long side of the strip-shaped irradiation range formed by the light source 130 is not less than the maximum width of the inspected surface 200 so as to cover the whole range of the inspected surface 200, and the length of the short side of the strip-shaped irradiation range is determined according to the relative movement speed of the inspected surface 200 and the light source 130 and the surface inspection accuracy of the inspected surface 200. In an embodiment of the present invention, 6 light sources 130 are provided at different positions in the surface defect detecting system 100, and the light source 130 may be a CST model CST-2LPG800-W-TS type bar light source.

The plurality of strip-shaped irradiation ranges formed by the plurality of light sources 130 on the bearing structure 110 are overlapped and irradiate at the same position, the image acquisition device 120 acquires images in the strip-shaped irradiation ranges, the positions irradiated by the light sources 130 change according to the movement path of the detected surface 200 in the process that the detected surface 200 moves relative to the image acquisition device 120 and the light sources 130, and the image acquisition device 120 acquires the images in the strip-shaped irradiation ranges in the detected surface 200 until images of all positions of the detected surface 200 are acquired for surface defect detection. Specifically, the surface defect detecting system may further include a detecting module, such as an industrial computer, which is capable of receiving the image acquired by the image acquiring device 120, and calculating the surface defect detecting result according to a preset processing procedure and a calculating method to obtain the type, range, and position of the surface defect point.

Further, as shown in fig. 1 and fig. 2, in the surface defect detecting system 100, the optical axis of the image capturing device 120 is directed to the strip-shaped illumination range formed on the carrying structure 110 or the detected surface 200 by the plurality of light sources 130. In the present embodiment, the optical axis of the image capturing device 120 is not limited to be perpendicular to the detected surface 200, but the center position of the image captured by the image capturing device 120 is ensured to coincide with the irradiation position of the light source 130, so as to ensure the image accuracy. When the line-scan camera is selected by the image capturing device 120, the irradiation position of the light source 130 is ensured to be within the visual field of the image capturing device 120, and preferably, the irradiation range direction of the bar shape formed by the light source 130 is the same as the opening direction of the light inlet of the line-scan camera (see fig. 5).

In a preferred embodiment of the present invention, the object to be detected is a flat plate, such as a plate made of various metals, plastics, glass, etc., wherein the detected surface 200 is a large plane facing upward in the flat plate, and if the bottom plane needs to be detected, the detection can be continued by using the surface defect detecting system 100 in this embodiment after the flat plate is turned over. The side detection of the flat plate shape is not within the scope of the present embodiment and will not be described. In this embodiment, the detected surface 200 is driven to move in a predetermined path by using a device such as a conveyor belt set as the bearing structure 110, and the predetermined path of the detected surface 200 includes a translation along the plane of the bearing structure 110 in a first direction and a translation along the plane of the bearing structure 110 in a second direction, so that the illumination ranges of the light source 130 in the stripe shape formed on the detected surface 200 are substantially perpendicular to each other, so as to ensure the accuracy of the curvature calculation, for example, the angle between the illumination ranges of the light source 130 in the stripe shape formed on the detected surface 200 is 90 ° and the deviation is not greater than ± 5 °. Specifically, for example, as shown in fig. 6, the detected surface 200 is substantially a rectangular plane, the first direction and the second direction of the detected surface may be set as the long side direction and the short side direction of the rectangle, and for the detected surfaces 200 with other shapes, the first direction and the second direction perpendicular to each other may also be preset in the plane, and the bearing structure 110 is controlled to drive the detected surfaces 200 to perform translational motion in two directions, respectively.

Further, for the embodiment where the image capturing device 120 and the light source 130 are fixedly disposed, the movement path of the detected surface 200 enables the detected surface 200 to pass through the field of view of the image capturing device 120, such as a set of conveyor belts disposed at a specific angle, or cooperate with other equipment, such as a gripping device, to change the movement direction of the detected surface 200. Preferably, the image capturing device 120 and the light source 130 are disposed above the carrying structure 110, as shown in fig. 3, the carrying structure 110 drives the detected surface 200 to pass through the field of view of the image capturing device 120 from below, and after the far end drives the detected surface 200 to rotate by 90 °, the detected surface is reversely translated under the coordinate system of the image capturing device 120 and passes through the field of view of the image capturing device 120.

As shown in fig. 4, according to a preferred embodiment of the present invention, the surface defect detecting system 100 further comprises a control system 140, wherein the control system 140 is in communication with the image capturing device 120 and the light sources 130 and is capable of controlling the different light sources 130 to be turned on or off at a predetermined frequency and timing, respectively, the specific frequency and timing of the light sources 130 being exemplified in the subsequent embodiments. The different light sources 130 are controlled to irradiate the detected surface 200 in a time-sharing manner, the image acquisition device 120 can acquire images of a certain position (the position irradiated by the light source 130) in the detected surface 200 under the irradiation of the different light sources 130, and the surface characteristics of the detected surface 120 can be reflected more comprehensively by setting the light rays and the incident angles emitted by the different light sources 130.

Further, according to the preferred embodiment of the present invention, as shown in fig. 1 and fig. 2, the optical axis direction of the image capturing device 120 is substantially perpendicular to the long side direction of the strip-shaped illumination range formed by the light source 130 on the supporting structure 110 or the detected surface 200, so as to avoid the occurrence of large distortion in the edge position of the captured image, and as for the deviations caused by the machining precision and the assembly precision, in the preferred embodiment of the present invention, the small inclination amount can be compensated by algorithm optimization, and the image captured by the image capturing device 120 can be corrected, but when the inclination amount of the image capturing device 120 is large, even if the correction is performed by algorithm optimization, the image precision will be greatly reduced, and the surface defect detection result will be affected. The light sources 130 are illuminated at the same position, and the light rays are distributed over the supporting structure 110 in fan shape at different central angles. The direction in which the optical axis of the image capturing device 120 extends passes through the irradiation range (the region where the light rays coincide in fig. 2) formed by the plurality of light sources 130, and may be in a plane perpendicular to the long-side direction of the strip-shaped irradiation range. To be close to specular reflection's being detected surface 200, the image acquisition device 120 deviates the reflection angle the farther, and the received reflected light intensity is lower, therefore, in the preferred embodiment of the utility model, the optical axis of image acquisition device 120 and the angle range that is detected between surface 200 can be adjusted within a certain range to the detected surface of corresponding different materials to and the surface defect detection requirement. During the primary surface defect detection, the relative position between the image capturing device 120 and the light source 130 is fixed, and the relative position is adjustable within a certain angle range with the image capturing device 120 and the light source 130.

In this embodiment, the inspected surface 200 is divided into a first side and a second side by the normal direction, for example, in fig. 2, the first side is the left side and the second side is the right side from the perspective of the observer. The light sources 130 are divided into a first light source group 131 and a second light source group 132 according to the arrangement positions, the first light source group 131 is arranged on a first side of the inspected surface 200, and the second light source group 132 is arranged on a second side of the inspected surface 200.

Specifically, in the preferred embodiment of the present invention, the first light source set 131 includes one bar light source 131-1, and the bar light source 131-1 laterally irradiates the supporting structure 110 at an incident angle of not less than 75 °. Further, the second light source group 132 includes at least three stripe light sources, and the stripe light sources in the second light source group 132 irradiate the same position of the supporting structure 110 with different incident angles. The stripe light source 132-1 with the largest incident angle among the plurality of stripe light sources of the second light source group 132 is laterally irradiated to the carrying structure 110 with an incident angle not less than 75 °, wherein the incident angles of the stripe light source 131-1 and the stripe light source 132-1 are selected according to the material characteristics of the inspected surface 200, for example, 80 °. In practical application, dust may be contaminated in the transportation process or the processing process of the detected surface 200, convex particles are formed on the detected surface 200, the convex particles do not belong to the defects of the detected surface 200, and in order to prevent misjudgment, in the embodiment, the bar-shaped light source 131-1 and the bar-shaped light source 132-1 with large incident angles are selected to irradiate the detected surface 200 from the first side and the second side respectively, so that the characteristics of the connection position of the dust and the detected surface 200 can be displayed more clearly, discrimination can be performed, misjudgment can be reduced, and the accuracy of surface defect detection can be improved.

As shown in fig. 1 and 2, in the preferred embodiment of the present invention, at least three bar light sources are included in the second light source group 132, and the three bar light sources are arranged in parallel and uniformly within a preset incident angle range of the second side of the detected surface 200. Preferably, all the bar-shaped light sources in the first and second

light source groups

131 and 132 are arranged in parallel and edge-aligned. In practical application, the strip-shaped light sources can be selected from the same specification, and are arranged in parallel and aligned by taking the overlapped irradiation positions as the center of a circle, so that the coverage range of the formed strip-shaped irradiation positions is the same. Different strip light sources are irradiated to the inspected surface 200 at different incident angles to form different reflected lights, and increasing the number of strip light sources in the second light source group 132 can improve the accuracy of surface defect detection, for example, as shown in fig. 2, the second light source group 132 includes 5 strip light sources. In various embodiments of the present invention, the number of bar light sources in the second light source group 132 is preferably not less than three, for example, the bar light sources in the second light source group 132 only remain the bar light sources 132-1, 132-3 and 132-5 in fig. 2. Of course, in order to further improve the accuracy of the surface defect detection, more strip-shaped light sources can be arranged.

Use first light source group 131 to have 1 bar light source, second light source group 132 includes 5 bar light sources for the example, in the embodiment of the utility model, 6 bar light sources open and close with different frequency and chronogenesis, further, drive and detect bearing structure 110 that surface 200 moved and also pause when light source 130 and image acquisition device 120 open to avoid reducing because of the image definition that the motion leads to acquireing, defect detail performance ability is not enough. Specifically, the moving/stopping frequency of the carrying structure 110, the on/off frequency of the image capturing device 120, and the on/off frequency of the 6 bar light sources may be as shown in fig. 7, images of the detected surface 200 under different light source illumination are captured by the image capturing device 120, specifically, an industrial personal computer may be used as a unified control switch, for example, the on and off of the image capturing device 120 and the light sources 130 are controlled by an enable signal, a low level signal is output during the translation of the detected surface 200 along the first direction or the second direction or within the visual field of the image capturing device 120, the image capturing device 120 and the light sources 130 are turned on, a high level signal is output during the rotation of the detected surface 200 or outside the visual field of the image capturing device 120, the image capturing device 120 and the light sources 130 are turned off, and a voltage signal is continuously output at a preset frequency during all the detection processes, so as to control the timing of the image capturing device 120 and the different light sources 130.

According to the preferred embodiment of the present invention, as shown in fig. 1 and fig. 2, the surface defect detecting system 100 further includes a second image capturing device 150, wherein the second image capturing device 150 is disposed on the first side of the detected surface 200, and the optical axis of the second image capturing device 150 is also directed to the strip-shaped irradiation range formed by the plurality of light sources 130 on the carrying structure 110 or the detected surface 200. Preferably, the second image capturing device 150 also selects a line scan camera, which can be used as a supplementary device of the image capturing device 120, and when the surface defect detection is performed, the image capturing device 120 and the second image capturing device 150 are simultaneously turned on, and images at different angles are respectively captured, so that the accuracy of the surface defect detection is improved. In an embodiment of the present invention, the second image capturing device 150 can select the ML-HM-08K30H-00-R model 8K line scan camera of Teledyne DALSA brand, and cooperate with the LS9001A model line scan lens of long footpath brand for use. The second image capturing device 150 may further be configured with an image capturing card to capture the captured image signal into the industrial control device, and store the captured image signal in the form of a data file on the hard disk, so as to facilitate subsequent image processing. Specifically, the image acquisition card can be a Teledyne DALSA brand OR-A8X0-PX840 model image acquisition card.

In a preferred embodiment of the present invention, the distance between the image capturing device 120 and the carrying structure 110 in the optical axis direction thereof and the distance between the second image capturing device 150 and the carrying structure 110 in the optical axis direction thereof do not overlap, so as to avoid mutual interference when adjusting the angles of the image capturing device 120 and the second image capturing device 150, specifically, standard lenses with different working distances can be selected, and in this embodiment, the image capturing device 120 is closer to the detected surface 200 than the second image capturing device 150 in the respective optical axis direction.

According to the preferred embodiment of the present invention, the bar light sources 131-1 in the first light source group 131 and the bar light sources 132-1 having the largest incident angle in the second light source group 132 are dark field light sources, and the bar light sources 132-2-132-5 except the bar light sources 132-1 having the largest incident angle in the second light source group 132 are gray field light sources. In the present embodiment, the bar light source 131-1 and the bar light source 132-1 are mainly used in cooperation with the image capturing device 120 to prevent dust from adhering to the detected surface 200 and causing erroneous judgment.

In various embodiments of the present invention, the setting angles and distances of the image capturing device 120 and the light source 130 are selected within a preferred value range. As shown in fig. 2, the extending direction of the first side of the detected surface 200 is taken as a 0 ° direction, and the included angle between the optical axis direction of the image capturing device and the 0 ° direction is 30-95 ° and is adjustable in the angle range. The optical axis of the image capturing device 120 is not limited to be perpendicular to the inspected surface 200, but can be adjusted in a wide range according to the surface characteristics of the inspected surface 200, and for the inspected surface 200 with obvious diffuse reflection, the image capturing device 120 can be disposed on the second side of the inspected surface 200, i.e. the side close to the second light source 132. While avoiding interference between the image capturing device 120 and the light source 130 and the second light source group 132 having a plurality of bar-shaped light sources is disposed at the second side, the selectable angular range of the image capturing device 120 at the first side is larger. Specifically, the image capturing device 120 may form an angle of 30 °, 60 °, 90 °, 95 °, or the like with the 0 ° direction. The distance between the image capturing device 120 and the carrying structure 110 along the optical axis is 750-850 mm, for example 800 mm.

The second image capturing device 150 is disposed on the first side of the detected surface 200, an included angle between the optical axis direction of the second image capturing device 150 and the normal direction of the detected surface 200 on the first side ranges from 25 ° to 60 °, and when the reflection characteristic of the detected surface 200 is known once, an included angle between the optical axis direction of the second image capturing device 150 and the normal direction of the detected surface 200 on the first side may be 25 °, 30 °, 45 °, 60 °, and the like, and is adjustable within an angle range of 25 ° to 60 °. The distance between the second image capturing device 150 and the carrying structure 110 along the optical axis thereof is 940-1040 mm, for example 990 mm, and the distance between the second image capturing device 150 and the inspected surface 200 along the optical axis may be set to be slightly larger than the distance between the image capturing device 120 and the inspected surface 200 along the optical axis.

The range of the included angle between the incident direction of the first light source group 131 and the normal direction of the detected surface 200 is 75-87 degrees, for example, 80 degrees, and the included angle is used for discriminating dust attached to the detected surface 200, so as to reduce misjudgment. The angle between the incident direction of the second light source group 132 and the normal direction of the detected surface 200 is in the range of 10-87 °, and the incident angles of the plurality of strip-shaped light sources are distributed in the angle range. The distance between the first light source set 131 and the supporting structure 110 in the irradiation direction is 600-1000 mm, for example, 800 mm. The second light source group 132 includes at least three individually controlled strip light sources, and the distance between the three strip light sources and the supporting structure 110 along the illumination direction is 600-1000 mm, for example 800 mm.

Further, the plurality of bar light sources in the second light source group 132 are equidistant from the supporting structure 110 along the irradiation direction, as shown in fig. 2, the plurality of bar light sources are dispersed in a fan shape in a range of an angle of 10 to 87 ° with respect to the normal direction of the detected surface 200 in a side view, and the plurality of bar light sources are equidistant from the supporting structure 110 along the irradiation direction, so that the structure is compact, the incident angle of the light sources can be conveniently adjusted, and meanwhile, when the curvature of the surface defect is calculated, the influence of the incident distances of different light sources can be ignored, and the calculation is simplified.

The utility model discloses still include a surface defect detection method S100' S embodiment, can utilize the surface defect detecting system to carry out surface defect detection to being detected the surface in the aforesaid embodiment. As shown in fig. 8, in step S101, the incident angles of the plurality of light sources and the angles of the optical axes of the image capturing devices with respect to the inspected surface are respectively obtained, and in particular, this step can be obtained when the surface defect detecting system is set up. According to the utility model discloses a preferred embodiment, the incident angle of light source and image acquisition device's optical axis can be adjusted at certain within range for the angle that is detected the surface to the adaptation has different diffuse reflection coefficients to be detected the surface, the embodiment of the utility model discloses an in not restrict to be detected the surface and be the diffuse reflection surface, be applicable equally to specular reflection or half specular reflection's surface, for example all kinds of metal face, glass face, organic macromolecular material face etc.

In step S102, images of the detected surface under irradiation of different light sources are acquired, and the gray value of the irradiated portion of the detected surface corresponding to the light source is obtained according to the images corresponding to the different light sources. The image of the inspected surface is obtained by an image acquisition device, specifically, an industrial camera, whose relative position with respect to the plurality of light sources is fixed, and which can photograph the position on the inspected surface irradiated by the light sources. The utility model discloses a different embodiments can directly obtain the grey map that is detected the surface to read the grey value, or after obtaining the image, carry out the preliminary treatment to the image, acquire the grey value. The images under the irradiation of different light sources can be respectively turned on and off in a preset time sequence by controlling the plurality of light sources, and can also be turned on simultaneously according to the setting that different light sources can emit light beams with different colors, and after the images are obtained, the images under the irradiation of different light sources are split according to the colors of the light beams.

In step S103, a surface normal vector and/or a glossiness of the illuminated portion of the inspected surface is calculated according to the gray value, the incident angle of the corresponding light source, and the angle of the optical axis of the image capturing device relative to the inspected surface, wherein the glossiness of the inspected surface can be represented by the specular reflection coefficient.

In the existing surface defect detection method, because the light source is a parallel light source or an infinite point light source, and the optical axis of the image acquisition device is perpendicular to the detected surface, the numerical values of the incident angle and the optical axis angle are not introduced in the process of calculating the normal vector of the surface, specifically, the most widely applied halcon algorithm library in the existing method for detecting the surface defect by using machine vision is taken as an example, wherein the limitation on a plurality of relative position relations set by hardware and the defects of the surface defect detection only capable of being applied to the diffuse reflection surface are all caused by the calculation principle.

The surface defect detection method S100 provided in this embodiment can adjust the incident angle of the light source and the optical axis angle of the image acquisition device according to the diffuse reflection coefficient of the detected surface, and calculate the surface normal vector according to the incident angle of the light source and the optical axis angle of the image acquisition device, and can be applied to surface defect detection of a specular reflection surface and a semi-specular reflection surface, thereby reducing the restriction on the relative position relationship of hardware, and having a wider application range.

In step S104, the curvature of the irradiated portion of the detected surface is calculated from the surface normal vector. According to the preferred embodiment of the present invention, the curvature change of the portion of the detected surface irradiated with the light source in the direction can be calculated by controlling the direction of the light source. Further, the same position, for example, the same pixel coordinate, the curvature change in different directions are calculated, and after the detection of the whole range of the detected surface is completed, the defective point in the detected surface whose curvature change exceeds the threshold (for example, it is set as a failure exceeding the threshold) and the position coordinate of the defective point in the detected surface are output. Preferably, the image of the position of the defect point can be amplified and displayed, so that the defect point can be rechecked, and the visualization degree and the accuracy of surface defect detection are improved.

In step S105, the surface defect of the surface to be inspected is determined based on the curvature and/or the glossiness of the irradiated portion of the surface to be inspected, and for example, the curvature exceeds a certain threshold value for a flat surface, and the surface defect is determined. And when the surface detection is finished in the range needing surface detection in the detected surface, the whole surface detection process of the detected surface on the current station is finished.

Further, according to the preferred embodiment of the present invention, the surface defect detecting method further includes obtaining the surface roughness of the detected surface, for example, the measured value of the detected surface, the gray value of the detected surface under the irradiation of different light sources is also related to the surface roughness of the detected surface, and after the detected surface is determined, the surface roughness can be used as a constant in the process of calculating the normal vector of the surface.

The embodiment of the utility model provides an improve Lambert (Lambert) illumination mathematical model for two-way reflection Distribution Function (Bidirectional reflection Distribution BRDF), according to two-way reflection Distribution Function's Theory, the luminance of different visual angle lower surfaces is different, consequently after setting for image acquisition device's optical axis for the angle that is detected the surface, for example mark image acquisition device, can be based on the BRDF model that Cook-Torrance model of little surface Theory (little Theory) established, concrete:

wherein F (h, l) is Fresnel's equation (Fresnel equalizations), G (l, v) is set Attenuation Factor (Geometrical Attenuation Factor), D (h, n) is Normal Distribution Function (Normal Distribution Function), in the preferred embodiment of the utility model, for simplifying the calculation process, adapt to industrial production, above three can simplify respectively to the fixed constant that is relevant with the surface roughness of detected surface, can obtain through calibration calculation in advance respectively, specific:

the fresnel equation is expressed as:

F(h，l)＝F ₀ +(1-F ₀ )(1-(h·l)) ⁵

the geometric attenuation factor is expressed as:

k＝0.5α

the normal distribution function is expressed as:

wherein alpha is the surface roughness of the detected surface, the value range is [0,1], and the alpha can be obtained through actual measurement of the detected surface or directly according to the processing process of the detected surface. l is the incident angle of the light source, v is the angle of the optical axis of the image acquisition device relative to the detected surface, which can be obtained by calibrating the light source and the image acquisition device in the surface defect detection system, and according to the above expression, the gray level value of the image at the position irradiated by one light source in the detected surface can be simply expressed as:

s ₁ G ₁ ＝K _a +K _d (n·l ₁ )+K _s (v·l ₁ )

in the formula, G is a gray value of an acquired image, after the image under irradiation of the corresponding light source is acquired by the image acquisition device, the corresponding gray value can be read, s represents an illumination coefficient of the corresponding light source, and is directly acquired when the surface defect detection system is arranged.

K _a Indicating ambient light, and in particular applications, controlling the detection environment of the surface to be detected to reduce the effect of the ambient light in the application scenario _a Approaching zero and neglecting the influence of ambient light. K _d Albedo, K, of the surface to be examined in the existing photometric stereo method _s Is the specular reflection coefficient of the surface to be inspected, where K _s Is approximately equal to K _d Reciprocal of (1), in the above formula, K _d (n.l) represents the gray value, K, contributed by diffuse reflection in the image of the inspected surface _s (v · l) represents the grey value contributed by the specular reflection in the image of the detected surface.

Further, the gray-scale values for the images of the detected surface respectively illuminated by the plurality of light sources can be expressed as:

according to the above equation set, canAccurately calculating a surface normal vector n = (Z) in the detected surface within the range of light source irradiation _x ,Z _y 1) and further calculating the curvature of the light source irradiated portion in the detected surface according to the surface normal vector n.

Compared with the existing surface defect detection and calculation method, the surface defect detection method provided by the embodiment reflects the incident angles of different light sources and the influence of the visual angle of the image acquisition device on the gray value of the detected surface image, is more flexible in setting the positions of the light source and the image acquisition device, can also perform surface defect detection on the specular reflection surface and the semi-specular reflection surface, and enlarges the application range of the surface defect detection. Compared with manual visual detection, the limit resolution of the industrial camera is superior to that of human eyes, the surface defect detection method in the embodiment is applied, the detection standard is unified, the precision is higher, the efficiency and the accuracy rate can be improved by replacing manual detection, and the labor cost is reduced.

Wherein the specular reflection coefficient K of the surface to be inspected _s The glossiness of the detected surface can be reflected and can be obtained when the normal vector n of the surface is calculated. The gloss of the inspected surface, and the combination of gloss and curvature, are also used to represent defects in the inspected surface. In practical applications, there are many different types of surface defects in the inspected surface, and for the inspected surface in which only shape defects such as projections or depressions exist, it can be reflected only by the curvature of the inspected surface, or by a combination of the curvature and the glossiness of the inspected surface. For a detected surface where only color abnormality exists, the surface defect can be judged only by the glossiness of the detected surface. Of course, in most cases, there are usually multiple surface defects in the inspected surface, and different types of surface defects can be judged by using curvature and gloss, respectively, or by using a combination of curvature and gloss.

Specifically, the detected surface is a flat surface of the anodized aluminum plate, and in the process of manufacturing the anodized aluminum plate, the possible surface defects in the detected surface mainly include 12 types in the following table, wherein each type of surface defect can be identified by curvature, glossiness or combination of curvature and glossiness, and the correspondence between the surface defect and curvature and glossiness is as shown in the following table.

For other types of inspected surfaces, it is also possible to capture the vast majority of surface defects by curvature and/or gloss.

The utility model discloses still include the embodiment of a surface detection production line, including the aforesaid embodiment surface defect detecting system 100, the surface detection production line can also be provided with and be applied to the surface defect detecting system who is detected other surfaces of article to the completion is detected the defect detecting process on article full surface or preset surface. The surface detection production line can also integrate stations or equipment for detecting the surface cleanliness of detected objects.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described in the foregoing embodiments, or equivalents may be substituted for elements thereof. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A surface defect detection system, comprising:

a load bearing structure for supporting a surface to be inspected;

an image acquisition device configured to be relatively movable with the load bearing structure or the inspected surface in a predetermined path; and

2. The system of claim 1, wherein an optical axis of the image capturing device is directed to a strip-shaped illumination area formed on the carrying structure or the inspected surface by the plurality of light sources.

3. The system of claim 1 or 2, wherein the carrying structure comprises a driving unit, and the driving unit drives the detected surface to move along a preset path; the image acquisition device and the light source are fixedly arranged.

4. The surface defect detection system of claim 3, wherein the predetermined path of the inspected surface comprises:

5. The system of claim 1 or 2, further comprising a control system in communication with the image capture device and the light sources and configured to control the different light sources to be turned on and off at a predetermined frequency and timing, respectively.

6. The surface defect detecting system of claim 2, wherein the optical axis direction of the image capturing device is substantially perpendicular to the long side direction of the strip-shaped irradiation range formed by the light source;

7. The surface defect detection system of claim 6, wherein the first light source group comprises a bar light source that is side-illuminated at an angle of incidence of not less than 75 ° to the carrying structure.

8. The surface defect detection system of claim 6, wherein the second light source group comprises at least three strip light sources, and the strip light sources irradiate the same position of the bearing structure at different incidence angles; the strip light source with the largest incident angle in the three strip light sources of the second light source group is laterally irradiated to the bearing structure at the incident angle not less than 75 degrees.

9. The surface defect detection system of claim 6, wherein the second light source group comprises at least three strip light sources, the three strip light sources being arranged in parallel and uniformly within a preset incident angle range of the second side of the detected surface.

10. The system of claim 6, further comprising a second image capturing device disposed on the first side of the inspected surface, wherein an optical axis of the second image capturing device is directed to a strip-shaped illumination area formed by the plurality of light sources on the supporting structure or the inspected surface.

11. The surface defect detecting system of claim 6, wherein the extending direction of the first side is 0 °, and the included angle between the optical axis direction of the image capturing device and the 0 ° direction is 30-95 ° and is adjustable within the angle range.

12. The system of claim 11, wherein the angle between the incident direction of the first light source set and the normal direction of the inspected surface is in the range of 75-87 °; the range of the included angle between the incident direction of the second light source group and the normal direction of the detected surface is 10-87 degrees.

13. A surface defect detection system according to claim 6, wherein the distance between the image capture device and the load bearing structure in the direction along the optical axis is 750-850 mm.

14. The surface defect detection system of claim 6, wherein the distance between the first light source group and the bearing structure in the irradiation direction is 600-1000 mm; the second light source group at least comprises three strip-shaped light sources which are independently controlled, and the distance between the three strip-shaped light sources and the bearing structure along the irradiation direction is 600-1000 mm.

15. The surface defect detection system of claim 14, wherein the plurality of bar light sources in the second light source group are equidistant from the carrier structure in an illumination direction.

16. The system of claim 10, wherein the second image capturing device is disposed on the first side of the inspected surface, and an included angle between the optical axis direction of the second image capturing device and the normal direction of the inspected surface on the first side is 25-60 °.

17. The surface defect detection system of claim 10, wherein the second image capture device is positioned 940-1040 millimeters from the support structure along the optical axis.

18. The surface defect detection system of claim 10, wherein the image acquisition device is a 16K line scan camera; the second image acquisition device is an 8K line scan camera.

19. A surface inspection production line, comprising: the surface defect detection system of any one of claims 1-18.