JP2011180059A - Device and method for support of visual inspection - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for detecting defects with high accuracy, or a technology for supporting defect detection, regardless of a surface shape of an inspection object to be subjected to visual inspection. <P>SOLUTION: The surface of the inspection object is divided until being settled in the range of a prescribed curvature, and images are acquired in each divided domain. Namely, even if the surface of the inspection object is a curved surface having unequal curvatures, imaging is performed in a unit assumable approximately as a plane. Further, the acquired image is subjected to image processing to detect a defect. A discrimination method by a threshold is used for defect detection as hitherto. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a product surface appearance inspection technique. In particular, the present invention relates to a technique for inspecting the appearance of a surface having a free-form surface with a constant curvature.

  There is an appearance inspection technique for imaging a reflected light of illumination light irradiated on a product surface and detecting defects on the product surface. In the appearance inspection technique, for example, the obtained image is binarized, and a defect such as a scratch is detected by discriminating it based on a threshold (see, for example, Patent Document 1). The inspection object is, for example, a sheet-like object, a cylindrical object, or the like (see, for example, Patent Document 2 and Patent Document 3).

JP-A-4-244949 JP-A-10-197231 JP-A-11-183391

  When the product surface to be inspected is a flat surface or a curved surface with a constant curvature, reflection by illumination is constant. However, in the case of an object with a complicated shape such as the surface of a headlight of an automobile, the curvature of the surface is not constant, so that reflection by illumination changes in a complicated manner. For this reason, the difference in lightness and darkness changes in a complex manner depending on the part, which also affects the appearance of scratches. As described above, discrimination based on the threshold becomes difficult, and the detection accuracy of scratches and the like is not stable.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a technique for detecting a defect with high accuracy or a technique for supporting the detection of a defect regardless of the surface shape of an inspection target for performing an appearance inspection. To do.

  In the present invention, the surface to be inspected is divided until it falls within a predetermined curvature range, and an image is acquired for each divided area. That is, even if the surface to be inspected is a curved surface with a non-constant curvature, imaging is performed in units that can be regarded as a substantially flat surface. Further, the acquired image is subjected to image processing to detect a defect. For detection of defects, a discrimination method using a threshold value is used as in the prior art.

  Specifically, it is an appearance inspection support device that supports an appearance inspection for inspecting the surface state of an object, and includes an imaging unit that images the surface of the object, and a display unit that displays an image captured by the imaging unit. And a driving means for moving the photographing means, and a control means for controlling the photographing means and the driving means, wherein the control means determines each area where the photographing means performs photographing as a photographing unit area. Photographing unit determining means for performing, and for each of the photographing unit areas, arrangement position determining means for determining an arrangement position of the photographing means according to the position of the photographing unit area, and the photographing unit determining means includes the target The object data is used to divide the surface of the object until the curvature of the divided area is equal to or less than the predetermined value, and each divided area is set as an imaging unit area, and the control unit includes the imaging unit. region Each time the shooting, to provide an appearance inspection support apparatus, characterized in that for controlling the drive means to move said imaging means to position said position determination means has determined.

  Further, an appearance inspection apparatus for inspecting a surface state of an object, an imaging unit that images the surface of the object, a driving unit that moves the imaging unit, and a control that controls the imaging unit and the driving unit. Means for performing image processing on the image photographed by the photographing means to determine the presence / absence of a defect, and an output means for outputting a determination result by the defect determining means. A shooting unit determination unit that determines each of the shooting unit areas as a shooting unit area, and an arrangement that determines the position of the shooting unit for each shooting unit area according to the position of the shooting unit area. A position determining unit, wherein the photographing unit determining unit divides the surface of the target object using the data of the target object until the curvature of the divided area is equal to or less than the predetermined value, And the control means controls the driving means to move the photographing means to the arrangement position determined by the arrangement position determining means every time the photographing unit area is photographed. A feature visual inspection apparatus is provided.

  Further, an appearance inspection support method for supporting an appearance inspection of an object using an image obtained by photographing the surface of the object with an imaging means, wherein the curvature of a region after dividing the surface of the object is a predetermined value or less A shooting unit area determining step in which each divided area is set as a shooting unit area, and shooting is performed by moving the shooting unit according to the position of the shooting unit area for each shooting unit area. And a display step for displaying on the display means the image photographed in the photographing step, and in the photographing unit region determining step, the data of the object is used, and the surface of the object is divided into regions. The appearance inspection support method is characterized in that the area is divided until the curvature becomes equal to or less than the predetermined value, and each area after the division is used as an imaging unit area.

  According to the present invention, it is possible to detect a defect with high accuracy regardless of the surface shape of an inspection target for which an appearance inspection is performed. Or it can support detecting a defect with high precision.

It is explanatory drawing for demonstrating schematic structure of the external appearance inspection apparatus of embodiment of this invention. It is explanatory drawing for demonstrating schematic structure of the zoom camera of embodiment of this invention. (A), (b) is explanatory drawing for demonstrating the change of the illumination reflective direction by a shape change. (A)-(c) is explanatory drawing for demonstrating the outline | summary of embodiment of this invention. It is a functional block diagram of a control device of an embodiment of the present invention. (A)-(c) is explanatory drawing for demonstrating the outline | summary of the imaging | photography unit determination method of this invention. It is explanatory drawing for demonstrating the relationship between the curvature of embodiment of this invention, zoom magnification, and an area. It is a flowchart of the imaging | photography process of embodiment of this invention. It is a flowchart of the imaging unit determination process of embodiment of this invention. It is a flowchart of an example of the re-division process of embodiment of this invention.

<< First Embodiment >>
Hereinafter, a first embodiment to which the present invention is applied will be described. Hereinafter, in all the drawings for explaining the embodiments of the present invention, those having the same function are denoted by the same reference numerals, and repeated explanation thereof is omitted.

  FIG. 1 is a schematic configuration diagram of an appearance inspection apparatus 10 according to the present embodiment. As shown in the figure, an appearance inspection apparatus 10 according to the present embodiment includes a zoom camera 12 that captures a surface (work surface) 11 of a target product (work), a support unit 13 that supports the zoom camera 12, and a support unit. 13 includes a drive unit 14 that moves the zoom camera 12 via 13 and a control device 15 that controls the overall operation of the appearance inspection apparatus 10. The control device 15 includes a display device 16 and an input device 17 that are interfaces between the control device 15 and the user.

  The drive unit 14 includes a motor, a motor drive circuit, and the like, and moves the zoom camera 12 to a predetermined position in response to a command from the control device 15. In this embodiment, for example, the position of the zoom camera 12 is controlled in the x, y, and z axis directions using a predetermined XYZ coordinate system such as world coordinates.

  FIG. 2 is a schematic configuration diagram of the zoom camera 12 of the present embodiment. As shown in the figure, the zoom camera 12 of the present embodiment includes a photographing unit 21 that performs photographing, an illumination unit 22, and a zoom lens unit 23. The illumination unit 22 irradiates the work surface 11 with light having a predetermined intensity in accordance with a control signal from the control device 15. For the illumination unit 22, for example, ring illumination or the like is used. Further, the zoom lens unit 23 changes the zoom amount (zoom magnification) of the lens of the zoom camera 12 in accordance with a control signal from the control device 15.

  Prior to detailed description of each function of the present embodiment, a change in the illumination reflection direction due to a shape change will be described with reference to FIG.

  As shown in FIG. 3A, when the workpiece surface 11 is a plane, the reflection direction by illumination is constant as shown by the solid arrow. Therefore, when the reflected light is imaged, an intensity difference due to the difference in the direction of the reflected light does not occur. On the other hand, when the workpiece surface 11 is a curved surface with a non-constant curvature, the direction of reflection by illumination varies as shown by the solid arrow in FIG. Therefore, when the reflected light is imaged, an intensity difference occurs depending on the direction of the reflected light.

  In the present embodiment, the workpiece surface 11 is divided into regions of a size that can be regarded as a substantially flat surface according to the curvature, and each divided region is set as a photographing unit for performing photographing. That is, the measurement resolution is changed according to the complexity of the change of the workpiece surface 11, and each measurement region is inspected in a shape close to a plane. As shown in FIGS. 4A to 4C, the workpiece surface 11 is divided into a predetermined curvature or less, that is, a region 30 that can be regarded as a substantially flat surface, and an image is acquired in units of the region 30. Thereby, imaging (imaging) can be performed with the direction of the reflected light being substantially constant.

  In order to realize this, as shown in FIG. 5, the control device 15 according to the present embodiment includes a shooting control unit 50 that controls the drive unit 14, the shooting unit 21, the illumination unit 22, and the zoom lens unit 23 to perform shooting. An imaging unit determination unit 51 that divides the workpiece surface 11 to determine an imaging unit, an arrangement position determination unit 52 that determines an arrangement position of the zoom camera 12 according to the position of each imaging unit, and an area of each imaging unit A zoom amount determining unit 53 that determines the zoom amount (zoom magnification) according to the above, an illumination intensity determining unit 54 that determines the illumination intensity according to the area of each photographing unit, and processing the obtained image to detect a defect And an image processing unit 55.

  In addition, the control device 15 includes a shooting unit database (shooting unit DB) 61 that stores necessary information for each shooting unit determined by the shooting unit determination unit 51.

  The photographing unit determination unit 51 determines a photographing unit from CAD data of a photographing object (work) that is held in advance. Specifically, as shown in FIGS. 6A and 6B, the photographing unit determination unit 51 generates initial mesh data 31 of the workpiece surface 11 from CAD data. Then, the curvature of each mesh is calculated and compared with a predetermined curvature threshold. As shown in FIG. 6C, for the mesh 311 larger than the curvature threshold, the division is repeated until the curvature of the divided mesh is equal to or less than the curvature threshold, and each finally obtained mesh is used as a photographing unit.

  The shooting unit determination unit 51 generates a shooting unit database (DB) 61 that stores the size (area), position (center of gravity or central world coordinates), curvature, and the like, together with an identification code that identifies a mesh (shooting unit). To do.

  The CAD data does not necessarily have to be held in advance by the control device 15. For example, when the shooting unit determination unit 51 determines the shooting unit, it may be configured to acquire from the outside. The data of the object to be photographed is not limited to CAD data, as long as it can determine even the curvature.

  For example, as shown in FIG. 7, for each mesh of the generated initial mesh data, the area of the photographing unit is small in a region with a large curvature. In addition, the zoom amount (zoom magnification) of the region where the area of the photographing unit is small increases.

  Since the photographing unit is a unit photographed by the zoom camera 12, the mesh shape of the initial mesh data is, for example, a rectangle in which the ratio of the long side to the short side is the screen aspect ratio of the zoom camera 12. Or it is set as the rectangle whose aspect ratio is silver ratio. A predetermined initial value is used for the size of the initial mesh data.

  The arrangement position determination unit 52 refers to the imaging unit DB 61 generated by the imaging unit determination unit 51 and determines the arrangement position of the zoom camera 12 for each imaging unit. The arrangement position is determined so that the lens of the zoom camera 12 is directed to each photographing unit under the same conditions. For example, the optical axis of the zoom camera 12 is matched with the normal direction of the center of gravity (center) of the photographing unit. In this case, the position is a predetermined distance from the curved surface on the normal passing through the center of gravity of the curved surface serving as a photographing unit. The determined position is represented by a coordinate system adopted by the appearance inspection apparatus 10 of the present embodiment, and is stored in the photographing unit DB 61 in association with the photographing unit.

  As described above, the zoom amount determination unit 52 determines the zoom amount corresponding to the size (area) for each photographing unit, and the region determined as the photographing unit is within the predetermined range of the image area of the zoom camera 12. Control. Thereby, in this embodiment, imaging | photography for every imaging | photography unit determined by the imaging | photography unit determination part 51 is implement | achieved. In the present embodiment, for example, the zoom amount is set to the maximum value within a range in which the photographing unit falls within the field of view (image area) of the zoom camera 12. As shown in FIG. 7, when the area of the photographing unit is small, the zoom amount is enlarged. The determined zoom amount is stored in the photographing unit DB 61 in association with the photographing unit.

  The illumination intensity determination unit 54 determines the illumination intensity corresponding to the size (area) for each photographing unit. The illumination intensity is controlled so that the amount of light per unit area in the field of view of the zoom camera 12 is constant for each acquired image in order to make each photographing unit look the same (eliminate the difference in illuminance). Accordingly, the amount of light applied increases as the size of the photographing unit decreases. The determined illumination intensity is stored in the photographing unit DB 61 in association with the photographing unit.

  The photographing control unit 50 outputs a control signal so as to photograph the surface of the work 11 for each photographing unit determined by the photographing unit determining unit 51, and the photographing unit 21, the illumination unit 22, the zoom lens unit 23, and the driving unit 14 are output. Control.

  That is, the shooting control unit 50 generates a control signal so that the lens of the zoom camera 12 is directed to the shooting position determined by the arrangement position determination unit 54 for each shooting unit, and outputs the control signal to the drive unit 14. Move. Further, a control signal is generated so as to realize the zoom amount determined by the zoom amount determination unit 52, and is output to the zoom lens unit 23 to adjust the zoom amount. A control signal is generated so as to generate the amount of light determined by the illumination intensity determination unit 54, and is output to the illumination unit 22 for irradiation. Then, the photographing unit DB 61 is referred to, and after adjusting each part by these control signals, the photographing unit 21 performs photographing.

  The image processing unit 55 processes the image photographed by the photographing unit 21 and extracts defects, for example, scratches. The extraction uses a known defect detection technique for a plane. For example, the obtained image is binarized, and the presence or absence of scratches is determined using a threshold value.

  Each function of the control device 15 is realized by the CPU provided in the control device 15 loading and executing a program stored in advance in the storage device. Further, the photographing unit DB 61 is stored in a storage device provided in the control device 15.

  A flow of shooting processing by the shooting control unit 50 of the present embodiment will be described. FIG. 8 is a processing flow of the photographing process of the present embodiment. The photographing process starts in accordance with an instruction from the user.

  When receiving the instruction, the imaging control unit 50 causes the imaging unit determination unit 51 to perform an imaging unit determination process, and determines an imaging unit (imaging unit determination process; step S1001). Details of the photographing unit determination process will be described later. When the shooting unit is determined, the shooting control unit 50 sets the arrangement position in the arrangement position determination unit 52, the zoom amount in the zoom amount determination unit 53, and the illumination intensity in the illumination intensity determination region 54 for each determined shooting unit. Calculation is performed (step S1002).

  The imaging control unit 50 performs imaging according to the data held in the imaging unit DB 61 for each imaging unit, obtains an image for each imaging unit (step S1003), and displays it on the display device 16 (step S1004). The image processing unit 57 performs image processing on the image generated by the image generation unit 56, determines the presence / absence of a defect, detects a defect, and outputs the result (defect determination processing; step S1005). An image may be taken for each photographing unit, and the image processing unit 57 may determine the presence or absence of a defect, or the image processing unit 57 may determine the presence or absence of a defect after capturing images of all photographing units. .

  Next, the flow of shooting unit determination processing by the shooting unit determination unit 51 of this embodiment will be described. FIG. 9 is a processing flow of the photographing unit determination process of the present embodiment. The shooting unit determination process starts in accordance with an instruction from the shooting control unit 50.

  When receiving the start instruction, the imaging unit determination unit 51 reads the CAD data (step S1101). Then, initial mesh data 31 obtained by dividing the workpiece surface 11 into meshes of a predetermined size is generated from the CAD data (step S1102).

  Next, for each mesh, a re-division process that repeats the re-division is performed until a predetermined curvature is achieved. The outline of the subdivision process is as follows. First, the curvature χ of each mesh is calculated from CAD data (step S1103), and each mesh is compared with a curvature threshold T held in advance (step S1104). If it is larger than the curvature threshold value T, the image is re-divided (step S1105), the process returns to step S1103, the curvature of the division unit after the re-division is calculated from the CAD data, and the process is repeated. On the other hand, if the value is equal to or less than the curvature threshold, the division unit is set as a photographing unit, the center coordinates and the area are registered in the photographing unit database 61 (step S1106), and the photographing unit determination process is terminated.

  The re-division process is performed by the following method, for example. FIG. 10 is a diagram for explaining the flow of an example of the re-division process. After generating the initial mesh data 31, the photographing unit determining unit 51 calculates the center of gravity (center) coordinates and the curvature for each mesh, and registers them in the work mesh database (mesh DB) (step S1201). The center of gravity (center) coordinates and curvature are calculated from CAD data.

  Among the meshes registered in the mesh data DB, the smallest x coordinate value, the smallest y coordinate value, the smallest z coordinate value, the smallest z coordinate value (the smallest coordinate value) (Step S1202), and the curvature χ of the mesh is compared with the curvature threshold T (step S1203).

  When the curvature χ is larger than the curvature threshold T, the mesh is divided into four equal parts by a predetermined method (step S1204), and the center of gravity (center) coordinates and the curvature are calculated for each of the four divided meshes to obtain the fourth equal division. The center-of-gravity (center) coordinates and curvature of each subsequent mesh are registered in the mesh data DB, and the mesh data before division is deleted from the mesh data DB (step S1205). Then, the process returns to step S1202.

  Note that the quarter equal division is performed by dividing the short side and the long side of the rectangle into two equal parts by straight lines parallel to the long side and the short side, respectively. The division is not limited to such four divisions. For example, only the long side of the rectangle may be divided into two equal parts by a straight line parallel to the short side. However, since the data processing becomes complicated when the aspect ratios of the shapes after the division are different, a division method that can maintain the aspect ratio like the four-part division by the above-described method is preferable.

  On the other hand, in the comparison in step S1203, when the curvature χ is equal to or less than the curvature threshold T, the area of the mesh is calculated, the center coordinates and the area are registered in the photographing unit DB, and the mesh data is deleted from the mesh data DB ( Step S1206). And it is discriminate | determined whether the process of all the mesh data registered into mesh DB was completed (step S12079). If all the mesh data has not been processed, the process returns to step S1202. On the other hand, when all the mesh data has been processed, the process ends.

  As described above, according to the present embodiment, the surface of the workpiece that is the object of appearance inspection is divided into regions of a size that can be regarded as a substantially flat surface according to the curvature, and photographing is performed in units of divided regions. For this reason, even if the work surface to be inspected is a free-form surface having a non-constant curvature, it is difficult to be affected by the change in reflected light caused by the difference in curvature, and a stable image can be obtained. Therefore, the same determination accuracy can be obtained and a stable determination can be performed by a method similar to the appearance inspection of a plane regardless of the shape of the plane to be inspected.

  In addition, since the division size is determined according to the curvature, less calculation processing is required compared to the processing for equally dividing the whole to reduce the curvature of the photographing unit. Therefore, an increase in the processing amount can be suppressed, and defects such as scratches on the surface of the object to be inspected can be detected with an appropriate resolution.

  Furthermore, the illumination intensity is changed according to the size of the photographing unit. Therefore, an image with the same amount of light per unit area in the image area (field of view) of the zoom camera 21 can be obtained for each photographing unit, and discrimination can be performed under approximate conditions for every photographing unit. .

  In the above embodiment, the arrangement position, the zoom amount, and the illumination intensity are calculated for each area of the photographing unit. However, the present invention is not limited to this. For example, a database that specifies the arrangement position, zoom amount, and illumination intensity for each area of the photographing unit may be stored in advance, and the arrangement position, zoom amount, and illumination intensity may be determined based on the database.

  Further, the illumination intensity may not be changed for each photographing unit. In this case, the illumination unit 22 may be provided outside the zoom camera 21. Furthermore, the illumination intensity determination unit 54 may not be provided.

  In the above embodiment, image processing is performed on the generated image to automatically determine the presence or absence of a defect, but the present invention is not limited to this. The generated image may be displayed on the display device 16 so that the user can determine whether or not there is a defect. In this case, the image processing unit 56 may not be provided.

  Moreover, the said division | segmentation method is an example and is not restricted to this. There are no restrictions on the method as long as the final unit can be divided so that the curvature of each division unit is a certain value or less. For example, the division may be repeated for each mesh of the initial mesh data 31. In this case, after the initial mesh data 31 is generated, the curvature of each initial mesh is calculated, and the initial mesh larger than the curvature threshold is repeatedly divided into 2 divisions, 4 divisions, and 8 divisions in units of the initial mesh. At this time, the division is repeated until the curvature of all divided meshes constituting the initial mesh is equal to or less than the curvature threshold.

  Furthermore, in the above-described embodiment, the photographing unit having different areas is stored in the same image area by keeping the distance from the curved surface of the zoom camera 12 constant and changing the zoom amount. However, the present invention is not limited to this method. . A specified zoom amount may be realized by adjusting the distance from the curved surface of the zoom camera 12. In this case, the zoom lens unit 23 may not be provided.

  Note that the appearance inspection technique of the present embodiment can be used for appearance inspections such as the surface of a headlamp, a tail lamp, etc. of an automobile, the surface of a dashboard of an automobile, and the body surface of an automobile.

10: Appearance inspection device, 11: Work surface, 11: Mesh, 12: Zoom camera, 13: Support unit, 14: Drive unit, 15: Control device, 16: Display device, 17: Input device, 21: Imaging unit, 22: illumination unit, 23: zoom lens unit, 30: area, 31: initial mesh data, 50: shooting control unit, 51: shooting unit determination unit, 52: arrangement position determination unit, 53: zoom amount determination unit, 54: Illumination intensity determination unit, 55: image processing unit, 61: photographing unit DB

Claims (4)

An appearance inspection support device for supporting an appearance inspection for inspecting a surface state of an object,
Photographing means for photographing the surface of the object;
Display means for displaying an image taken by the photographing means;
Driving means for moving the photographing means;
Control means for controlling the photographing means and the driving means,
The control means includes
Shooting unit determining means for determining an area where the shooting means performs shooting as a shooting unit area, and
An arrangement position determining unit that determines an arrangement position of the imaging unit according to the position of the imaging unit region for each of the imaging unit regions;
The photographing unit determining means divides the surface of the target object using the data of the object until the curvature of the divided area is equal to or less than the predetermined value, and sets each divided area as a photographing unit area. ,
The visual inspection support apparatus, wherein the control unit controls the driving unit to move the photographing unit to the arrangement position determined by the arrangement position determining unit every time the photographing unit region is photographed. The appearance inspection support device according to claim 1,
The photographing unit determining means obtains a curvature for each region obtained by dividing the data of the object into a predetermined same size, and repeats equally dividing the region larger than the predetermined value into four, thereby determining the photographing unit region. An appearance inspection support device characterized by deciding. An appearance inspection apparatus for inspecting the surface state of an object,
Photographing means for photographing the surface of the object;
Driving means for moving the photographing means;
Control means for controlling the photographing means and the driving means;
Defect determination means for performing image processing to determine the presence or absence of defects on the image captured by the imaging means;
Output means for outputting the determination result by the defect determination means,
The control means includes
Shooting unit determining means for determining an area where the shooting means performs shooting as a shooting unit area, and
An arrangement position determining unit that determines an arrangement position of the imaging unit according to the position of the imaging unit region for each of the imaging unit regions;
The photographing unit determining means divides the surface of the target object using the data of the object until the curvature of the divided area is equal to or less than the predetermined value, and sets each divided area as a photographing unit area. ,
The visual inspection apparatus characterized in that the control means controls the driving means to move the photographing means to the arrangement position determined by the arrangement position determining means every time the photographing unit area is photographed. An appearance inspection support method for supporting an appearance inspection of an object using an image obtained by photographing the surface of the object with an imaging means,
An imaging unit area determination step in which the surface of the object is divided until the curvature of the divided area is equal to or less than a predetermined value, and each area after the division is an imaging unit area;
For each shooting unit area, a shooting step for shooting by moving the shooting means according to the position of the shooting unit area;
A display step of displaying on the display means the image taken in the shooting step,
In the shooting unit area determination step, the data of the object is used to divide the surface of the object until the curvature of the divided area is equal to or less than the predetermined value, and each divided area is set as the shooting unit area. A visual inspection support method characterized by that.

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