JP2022124812A - Check device, check method, and program - Google Patents

Abstract

To provide a check device capable of easily preparing a reference image.SOLUTION: A check device 100 checks a workpiece W having an outer periphery which has a form rotationally symmetrical about a symmetry axis AX4 or has a pattern provided repeatedly at a cycle of 2π/n. The check device 100 comprises an imaging unit 3 which moves in a circumferential direction about the symmetry axis AX4 with respect to the workpiece W to capture a plurality of images of the outer periphery including n first images A at approximately equal intervals in the circumferential direction, a RAM 53 in which the n first images A are stored, a reference image generation unit 511 which generates a first reference image R1 by using values of m pixels of which the positions in appearance of the outer periphery in the images are identical between m first images for generation being m first images A, and a determination unit 512 which compares a sample image being one of the n first images to the first reference image R1 to determine whether a defect is present in the outer periphery at a position where the sample image has been captured.SELECTED DRAWING: Figure 1

Description

The technology disclosed in the present specification provides an inspection apparatus, an inspection method, and a program used in the inspection apparatus for inspecting a workpiece having an outer peripheral portion in which a shape or pattern that is rotationally symmetrical about an axis of symmetry is periodically repeated. Regarding.

2. Description of the Related Art As an apparatus for inspecting the appearance of a work that is rotationally symmetrical about an axis of symmetry, for example, an inspection apparatus described in Patent Document 1 is known.

Japanese Patent Laid-Open No. 2002-200002 introduces a method of inspecting an image of a workpiece by comparing it with an image of a non-defective product that has been registered in advance.

Japanese Patent Application Laid-Open No. 2019-60628

A plurality of non-defective samples can be imaged to create a standard image (hereinafter also referred to as a "reference image") that is compared with an image of the object being inspected. It takes a lot of time and effort to create a reference image from a non-defective sample.

The technology disclosed in the specification of the present application has been made in view of the problems described above. This technique relates to an inspection apparatus that can easily prepare a reference image.

A first aspect of the technology disclosed in the present specification has an outer peripheral portion in which a rotationally symmetrical shape or pattern is repeatedly provided with a period of 2π/n (n is an integer of 3 or more) around the axis of symmetry. An inspection apparatus for inspecting a workpiece, wherein the outer peripheral part is imaged while moving relative to the workpiece in the circumferential direction around the axis of symmetry, so that the outer peripheral part is approximately in the circumferential direction. an imaging unit that captures a plurality of images including n first images at equal intervals; a storage unit that stores the n first images; 3 ≤ m ≤ n) of the m first creation images, the m pixels located at positions in which the external appearance of the outer peripheral portion in the image is common to each other. A reference image creation unit that creates a first reference image using the value of and compares a sample image that is one of the n first images and the first reference image. and a determination unit that determines whether or not there is a defect in the outer peripheral portion at the position where the sample image was captured. It should be noted that imaging the outer peripheral portion while moving relative to the work in the circumferential direction about the axis of symmetry means not only imaging during relative movement, but also after moving relative to the work. , imaging in a relatively stationary state, and then repeating the operation of performing relative movement to perform imaging.

A second aspect of the technology disclosed in the specification of the present application is, in the first aspect, n≧4 and m≧4, and the reference image creation unit generates the m number of m The average value of the pixel values of , excluding the maximum and minimum values, is used to create the first reference image.

A third aspect of the technology disclosed in the specification of the present application is, in the first aspect or the second aspect, wherein the plurality of images are different from any of the first images, and substantially extend the outer peripheral portion in the circumferential direction. further comprising n second images at regular intervals, wherein the reference image creating unit is k second images (an integer of 3≤k≤n) among the n second images; further creating a second reference image using the values of the k pixels whose positions in the appearance of the outer peripheral portion in the image are common among the k second creation images, and , when it is determined that there is a defect in the outer peripheral portion at the position where the sample image was captured, and the outer peripheral portion at the position where the second image adjacent to the position where the sample image was captured was captured Only when it is determined that there is a defect in the outer peripheral portion, it is determined that the outer peripheral portion is defective.

A fourth aspect of the technology disclosed in the specification of the present application is, in the third aspect, a position at which the first image is captured and a position at which the adjacent second image is captured, centering on the axis of symmetry. is 1°.

A fifth aspect of the technology disclosed in the present specification has an outer peripheral portion in which a rotationally symmetrical shape or pattern is repeatedly provided with a period of 2π/n (n is an integer of 3 or more) around the axis of symmetry. An inspection method for inspecting a work, wherein an image of the work is captured while moving relative to the work in a circumferential direction about the axis of symmetry, so that the outer peripheral portion is substantially evenly spaced in the circumferential direction. a capturing step of capturing a plurality of images including n first images; a storing step of storing the n first images; and m (3≤ using the values of the m pixels having a common position in the appearance of the outer peripheral portion in the image among the m first creation images which are the first images of m≦n) , a reference image creating step of creating a first reference image; comparing a sample image, which is one of the n first images, with the first reference image to obtain the sample image; and a determination step of determining whether or not there is a defect in the outer peripheral portion at the position where the is imaged.

A sixth aspect of the technology disclosed in the specification of the present application is the fifth aspect, wherein n≧4 and m≧4, and the reference image creating step includes, between the first creating images, the m The average value of the pixel values of , excluding the maximum and minimum values, is used to create the first reference image.

A seventh aspect of the technology disclosed in the specification of the present application is that in the fifth aspect or the sixth aspect, the imaging step is different from any of the first images, and the outer peripheral portion is substantially the same in the circumferential direction. The step of creating a reference image includes capturing n second images at intervals, wherein the step of creating a reference image includes k second images (an integer of 3 ≤ k ≤ n) among the n second images. Further creating a second reference image using the values of the k pixels whose positions in the outer appearance of the outer peripheral portion in the image are common among the k second creation images, and the determination The step determines that the outer peripheral portion is defective only when it is determined that the outer peripheral portion at the position where the second image adjacent to the position where the sample image was captured is defective.

According to an eighth aspect of the technology disclosed in the specification of the present application, in the seventh aspect, the position at which the first image is captured and the position at which the adjacent second image is captured, centering on the axis of symmetry. is 1°.

A ninth aspect of the technology disclosed in the present specification has an outer peripheral portion in which a rotationally symmetrical shape or pattern is repeatedly provided with a period of 2π/n (where n is an integer of 3 or more) around the axis of symmetry. A program used in an inspection device for inspecting a work, wherein the inspection device moves relatively to the work in the circumferential direction around the axis of symmetry, and moves the outer peripheral portion substantially evenly in the circumferential direction. an imaging unit that captures n first images at intervals; and a storage unit that stores the n first images. The values of the m pixels having a common position in the appearance of the outer peripheral portion in the image among the m first creation images that are the first images (integer of 3≦m≦n) used to create a first reference image.

A tenth aspect of the technology disclosed in the specification of the present application is, in the ninth aspect, a sample image which is one of the n first images and the first image, which is one of the n first images. 1 reference image to determine whether or not there is a defect in the outer peripheral portion at the position where the sample image was captured.

According to the first to tenth aspects of the inspection apparatus disclosed in the specification of the present application, an inspection apparatus is provided that can easily create a reference image.

Objects, features, aspects, and advantages associated with the technology disclosed herein will become more apparent from the detailed description and accompanying drawings set forth below.

It is a figure showing the whole inspection device composition about a 1st embodiment. It is a block diagram which shows the electrical structure of an inspection apparatus. FIG. 2 is a perspective view showing the configuration of a work holding unit of the inspection device according to the present embodiment; It is a top view which shows an imaging unit from upper direction. 3 is a block diagram showing the connection relationship between an imaging unit and a control unit; FIG. FIG. 4 is a flow chart showing the flow of quality determination of a workpiece in the inspection device; The first of the four first images stored in the control unit at an angle of α degrees. The first of the four first images stored in the control unit at an angle of α+90 degrees. The first of the four first images stored in the control unit at an angle of α+180 degrees. The first of the four first images stored in the control unit at an angle of α+270 degrees. FIG. 11 is a table showing an example of values of four pixels whose positions in the appearance of the outer peripheral portion in the images are common to each other in the four first creation images; FIG. FIG. 11 is a flow chart showing the flow of quality determination of a workpiece in the inspection apparatus according to the second embodiment; FIG. 5 is an explanatory diagram showing the relationship between a position where a first image of a work is captured and a position where an adjacent second image is captured; FIG. 4 is an explanatory diagram showing a first sample image together with a portion recognized as a defect; FIG. 10 is an explanatory diagram showing a second sample image together with a portion recognized as a defect; FIG. 11 is an explanatory diagram showing a modified second sample image in which each pixel of the second sample image is moved according to the first sample image;

Embodiments will be described below with reference to the attached drawings. In the following embodiments, detailed features and the like are also shown for technical explanation, but they are examples, and not all of them are necessarily essential features for enabling the embodiments.

It should be noted that the drawings are shown schematically, and for convenience of explanation, the configurations are omitted or simplified in the drawings as appropriate. In addition, the mutual relationship of sizes and positions of configurations shown in different drawings is not necessarily described accurately and can be changed as appropriate. Also, in drawings such as plan views that are not cross-sectional views, hatching may be added to facilitate understanding of the contents of the embodiments.

In the description presented below, similar components are labeled with the same reference numerals in the drawings, and their names and functions are similar. Therefore, detailed descriptions thereof may be omitted to avoid duplication.

In the description set forth below, when a component is referred to as "comprising," "including," or "having," such description excludes the presence of other components unless specifically stated otherwise. not an expression.

Although ordinal numbers such as "first" and "second" may be used in the description set forth below, these terms are used for convenience to facilitate understanding of the content of the embodiments. The techniques used and described in the embodiments are not limited to the order that can occur with these ordinal numbers.

In the drawings, the dimensions and numbers of each part may be exaggerated or simplified for the purpose of facilitating understanding. In addition, XYZ orthogonal coordinate axes (right-handed system) are appropriately attached to each drawing for explaining directions. The Z direction on the coordinate axis indicates the vertical direction, and the XY plane is the horizontal plane. Hereinafter, one side in the X direction may be called the +X side, and the other side may be called the -X side. The same applies to the Y-axis and Z-axis, and the +Z side indicates the vertical upper side.

<First embodiment>
The inspection apparatus 100 according to this embodiment will be described below.

<Configuration of Inspection Apparatus 100>
FIG. 1 is a diagram showing the overall configuration of an inspection apparatus 100 according to this embodiment. FIG. 2 is a block diagram showing the electrical configuration of the inspection apparatus 100. As shown in FIG. The inspection apparatus 100 is an apparatus for inspecting the appearance of the work W. As shown in FIG. This inspection apparatus 100 has a loading unit 1 , a workpiece holding unit 2 , an imaging unit 3 , an unloading unit 4 and a control unit 5 .

The workpiece W has an outer peripheral portion in which a rotationally symmetrical shape or pattern is repeatedly provided around the axis of symmetry AX4 at a period of 2π/n (where n is an integer of 3 or more). The workpiece W is, for example, a machine part provided with a gear Wb. In this embodiment, the workpiece W is arranged with the axis of symmetry AX4 parallel to the Z axis.

The workpiece W is transported to the loading unit 1 for inspection by an external transport robot (not shown) or an operator. The loading unit 1 is provided with a workpiece storage section (not shown). The work container is, for example, a table or a stocker. Then, for example, when the work W is temporarily stored in the work storage unit by an external transfer robot (not shown), the work detection sensor (not shown) provided in the work storage unit detects the work W. When the work detection sensor detects the work W, a signal indicating the detection is sent to the control unit 5 . The loading unit 1 is provided with a transport device (not shown). A transfer device transfers the work W from the loading unit 1 to the work holding unit 2 in accordance with a command from the control unit 5 .

<Work holding unit 2>
FIG. 3 is a perspective view showing the configuration of the workpiece holding unit 2 of the inspection apparatus 100 according to this embodiment. The work holding unit 2 is equipped with holding tables 21A and 21B that hold the work W conveyed by the conveying device. These holding tables 21A and 21B have the same configuration, and hold the work W in a posture in which the gear Wb is in a horizontal state. The configuration of the holding table 21A will be described below with reference to FIG. Since the holding table 21B has the same configuration as the holding table 21A, the holding table 21B is given the same reference numerals and the description thereof is omitted.

In the holding table 21A, as shown in FIG. 3, a chuck mechanism 22, a horizontal positioning mechanism 23, a rotating mechanism 24, and a vertical positioning mechanism 25 are stacked in the vertical direction. The chuck mechanism 22 includes movable members 221, 222, and 223 that are approximately L-shaped when viewed from the side, and a moving portion 224 that radially moves the movable members 221, 222, and 223 in accordance with a movement command from the control unit 5. and A protruding member 225 protrudes from the upper end surface of each movable member 221 , 222 , 223 . The work W is held by engaging the work W between the upper end surface and the projecting member 225 . In response to a gripping command from the control unit 5, the moving part 224 moves the movable members 221, 222, and 223 closer to each other, thereby aligning the central axis of the chuck mechanism 22 with the central axis of the workpiece W. W is retained. In addition, the workpiece W is released by moving the movable members 221, 222, and 223 away from each other according to the release command from the control unit 5. FIG. In this way, the work W can be held and released, and the uninspected work W can be loaded by the loading unit 1 and the inspected work W can be unloaded by the unloading unit 4 .

The chuck mechanism 22 constructed in this manner is supported by a horizontal positioning mechanism 23 . The horizontal positioning mechanism 23 has respective tables that are moved in directions (X-axis direction and Y-axis direction) perpendicular to each other in the horizontal direction (XY plane direction). Therefore, each table is driven according to the movement command from the control unit 5, and the chuck mechanism 22 can be positioned in the horizontal plane with high accuracy. As a driving method for each table, for example, a method combining a motor and a ball screw mechanism or a method combining two orthogonal linear motors are adopted.

The rotating mechanism 24 has a motor 241 . The rotating shaft of the motor 241 extends vertically upward (in the Z-axis direction). A horizontal positioning mechanism 23 is connected to the upper end of the rotating shaft. When a rotation command is given from the control unit 5 , the motor 241 is activated to integrally rotate the horizontal positioning mechanism 23 , the chuck mechanism 22 , and the workpiece W gripped by the chuck mechanism 22 around the rotation axis of the motor 241 .

In this embodiment, a horizontal positioning mechanism 23 is provided between the chuck mechanism 22 and the rotating mechanism 24 . This is for adjusting the relative positional relationship among the central axis of the chuck mechanism 22 , the axis of symmetry AX4 of the workpiece W, and the rotation axis of the motor 241 . By aligning the central axis of the chuck mechanism 22 with the rotation axis of the motor 241, the workpiece W gripped by the chuck mechanism 22 can be rotated around the shaft portion Wa. However, when the axis of symmetry AX4 of the gear Wb is off the shaft Wa, the gear Wb is out of alignment with the motor 241, and the gear Wb rotates eccentrically. Therefore, a horizontal positioning mechanism 23 is provided to correct the amount of deviation and the direction of deviation. When the deviation amount and the deviation direction are corrected, the axis of symmetry AX4 of the gear Wb and the rotation axis of the motor 241 are aligned. As a result, the image of the gear Wb is captured with high accuracy by the imaging unit 3, and the inspection accuracy of the work W is improved.

The vertical positioning mechanism 25 includes a holding plate 251 holding the motor 241, a base plate 252 arranged below the motor 241, four connecting pins 253 connecting the holding plate 251 and the base plate 252, and the base plate 252 vertically. and an elevating unit 254 for elevating in the direction. The lifting section 254 lifts and lowers the base plate 252 according to a lifting command from the control unit 5 . As a result, the rotation mechanism 24, the horizontal positioning mechanism 23, and the chuck mechanism 22 move integrally in the vertical direction. Then, the height position of the workpiece W is optimized at the pre-alignment position PA and the inspection position PI, which will be described below.

The holding tables 21A and 21B configured in this way are fixed on the support plate 261 with a certain distance therebetween, as shown in FIG. Further, a support plate 261 is supported by a turning driving portion 262 at an intermediate position between the holding tables 21A and 21B. The turning driving portion 262 can turn the support plate 261 by 180° around a turning axis AX1 extending in the vertical direction in response to a turning command from the control unit 5. As shown in FIG. In this embodiment, the pivot axis AX1 is arranged parallel to the Z-axis.

As shown in FIG. 3, a first position where holding tables 21A and 21B are positioned at prealignment position PA and inspection position PI, respectively, and a second position where holding tables 21A and 21B are positioned at inspection position PI and prealignment position PA, respectively. It is possible to switch between For example, the work W held by the holding table 21A positioned at the pre-alignment position PA is pre-aligned. In parallel with the pre-alignment process, the holding table 21A is shifted from the pre-alignment position PA to the inspection position PI by being switched from the first position to the second position by the turning drive unit 262 . The prealigned workpiece W is positioned at the inspection position PI.

After finishing the inspection of the workpiece W, the holding table 21A is rotated in the opposite direction, thereby shifting from the inspection position PI to the pre-alignment position PA. The inspected work W is positioned at the pre-alignment position PA. In the present embodiment, a position switching mechanism 26 that switches the position of the work W by the support plate 261 and the turning drive section 262 is provided.

The pre-alignment position PA is a position where pre-alignment processing is performed. An alignment camera 27 is arranged above the holding table 21 (or holding table 21B) positioned at the pre-alignment position PA. As shown in FIG. 3, the alignment camera 27 is arranged above the work W on the side opposite to the motor 241 with the work W interposed therebetween. The alignment camera 27 captures an image of the upper surface of the work W using a line sensor 271 extending radially outward with respect to the axis of symmetry AX4 of the work W. As shown in FIG. By rotating the work W at least once, an image including all of the protrusions (tooth addendum) and the recesses (tooth root) formed on the outer peripheral portion of the gear Wb is obtained.

An alignment illumination unit (not shown) is provided to illuminate the workpiece W held by the holding table 21A (or holding table 21B). Since the work W is illuminated by this alignment illumination unit, the alignment process is performed satisfactorily. The alignment camera 27 can image the work W rotated by the rotation mechanism 24 while the alignment illumination unit illuminates the work W. Image data of the imaged workpiece W is sent to the control unit 5 . Based on the image data sent to the control unit 5, the axis of symmetry AX4 of the gear Wb and the rotation axis of the motor 241 are aligned to correct the misalignment. Thus, the pre-alignment process is executed.

The inspection position PI is a position where inspection processing is performed. The imaging unit 3 is arranged beside the holding table 21A (or holding table 21B) positioned at the inspection position PI. At this inspection position PI, the workpiece W rotates with the axis of symmetry AX4 of the gear Wb and the rotation axis of the motor 241 coinciding. The imaging unit 3 images the rotating workpiece W. Image data of the imaged workpiece W is sent to the control unit 5 . Based on the image data sent to the control unit 5, for example, the gear Wb is inspected for flaws or defects.

The holding table 21A (or holding table 21B) that holds the inspected work W is shifted from the inspection position PI to the pre-alignment position PA by the position switching mechanism 26 . Then, the unloading unit 4 unloads the inspected work W from the holding table 21A (or the holding table 21B). The basic configuration of the unloading unit 4 is the same as that of the loading unit 1. FIG. More specifically, the unloading unit 4 has a workpiece storage unit (not shown) that temporarily stores inspected workpieces W, a workpiece detection sensor (not shown), and an unloader (not shown). . The unloading unit 4 conveys the inspected work W from the holding table 21 (or holding table 21B) to the work accommodation unit in accordance with an operation command from the control unit 5 .

<Imaging unit 3>
FIG. 4 is a plan view showing the imaging unit 3 from above. As shown in FIG. 4 , the imaging unit 3 has an inspection camera 31 , an inspection lighting section 32 , and a support plate 34 fixing the inspection camera 31 and the inspection lighting section 32 . The inspection camera 31 images the workpiece W from a direction perpendicular to the axis of symmetry AX4 of the workpiece W. When the work W makes one rotation about the axis of symmetry AX4, the outer peripheral portion of the work W is imaged.

The inspection illumination unit 32 is arranged in the circumferential direction with respect to the axis of symmetry AX4 of the workpiece W, and illuminates the workpiece W. As shown in FIG. For example, two inspection illumination units 32 are arranged. The inspection illumination unit 32 is arranged so as to illuminate the workpiece W obliquely, for example, with respect to the imaging direction of the inspection camera 31 . The inspection illumination unit 32 is arranged, for example, so that the angle formed by the imaging direction of the inspection camera 31 and the light irradiation direction of the inspection illumination unit 32 is 45°. If the imaging direction of the inspection camera 31 and the light irradiation direction are the same, the light reflection of the portion imaged by the inspection camera 31 will excessively improve the brightness. This makes it difficult to distinguish between light reflection and actual defects. For this reason, it is difficult to image defects in the outer peripheral portion of the work W. FIG. It is suitable for detecting defects in the outer peripheral portion of the workpiece W to set the angle formed by the imaging direction of the inspection camera 31 and the light irradiation direction of the inspection illumination unit 32 to about 45°. When the work W is rotated by the rotation mechanism 24 , the work W illuminated by the inspection illumination unit 32 is imaged by the inspection camera 31 . Image data captured by the inspection camera 31 is sent to the control unit 5 . The control unit 5 inspects the workpiece W based on the sent image data.

The imaging unit 3 includes a moving section 35 for appropriately arranging the positions of the inspection camera 31 and the inspection lighting section 32 with respect to the work W. As shown in FIG. The moving portion 35 includes two guide rails 351 for moving the support plate 34 with respect to the base portion 33 and a ball screw type driving portion 352 . The two guide rails 351 extend in the X direction with respect to the upper surface of the base portion 33 . Also, the support plate 34 moves along the guide rails 351 . The drive unit 352 is driven by known drive technology. For example, the driving part 352 is composed of a motor, a ball screw and a nut. In this case, the ball screw rotates and the nut moves in the X direction together with the support plate 34 when the motor is actuated by a command from the control unit 5 . It should be noted that another method, for example, a linear motor method, may be adopted as the driving method of the driving unit 352 .

The imaging unit 3 also has an arm 36 on the upper surface of the support plate 34 . The inspection camera 31 and the inspection lighting section 32 are attached to the arm 36 . Thereby, the inspection camera 31 and the inspection lighting section 32 are fixed to the support plate 34 .

<Control unit 5>
FIG. 5 is a block diagram showing the connection relationship between the imaging unit 3 and the control unit 5. As shown in FIG. The control unit 5 includes a central processing unit (i.e., CPU) 51 that performs various arithmetic processing, and a read only memory (i.e., ROM) 52 that is a read-only memory for storing basic programs. and a random access memory (ie, RAM) 53 which is a readable and writable memory for storing various information. The CPU 51 also includes a reference image creation unit 511 that creates a reference image, and a determination unit 512 that determines whether or not there is a defect in the outer peripheral portion of the work W. FIG.

The control unit 5 is connected to the operating sections (for example, the inspection camera 31, the inspection lighting section 32, the rotation mechanism 24, and the position switching mechanism 26) of each section of the inspection apparatus 100, and controls their operations. The control unit 5 also performs various calculations. This calculation includes, for example, creation of a reference image (described later) using image data captured by the inspection camera 31, comparison of a sample image (described later) with the reference image, detection of defects in the outer periphery of the workpiece W, and This is an operation for determination of presence/absence. Also, the control unit 5 records a program for performing each process of the inspection apparatus 100 . By executing this program, each process of the embodiment described later is realized.

The control unit 5 inputs signals from various sensors of each part of the inspection apparatus 100 and outputs signals to the operating parts of each part. The control unit 5 also performs image processing. Image processing is performed by, for example, binarizing the image data captured from the alignment camera 27 or the inspection camera 31 .

<Good/bad judgment of workpiece W>
FIG. 6 is a flow chart showing the flow of quality determination of the work W in the inspection apparatus 100. As shown in FIG. 7 is the first image A at an angle of α degrees among the four first images A stored in the control unit 5, and FIG. The first image A at an angle of α+90 degrees, FIG. 9 is the first image A at an angle of α+180 degrees among the four first images A stored in the control unit 5, and FIG. Of the four first images A, this is the first image A at an angle of α+270 degrees. α is the angle formed between the initial position and the imaging position with the axis of symmetry AX4 of the work W as the center when the initial position of the work W is 0 degree.

When determining whether the work W is good or bad, first, the imaging unit 3 takes 360 images of the outer peripheral portion of the work W in the circumferential direction of the work W at intervals of 1 degree in the circumferential direction. As a result, the imaging unit 3 captures n first images A of the outer periphery of the work W at substantially equal intervals (step S1) (imaging process). The imaging unit 3 moves relative to the workpiece W in the circumferential direction around the axis of symmetry AX4, and captures the outer peripheral portion of the workpiece W as n first images A at substantially equal intervals in the circumferential direction. functions as a department.

For example, when the workpiece W has 44 teeth, the inspection camera 31 captures four first images A. As shown in FIG. The reason for this is as follows. When images are taken every 1 degree in the circumferential direction of the workpiece W, 360 images are taken. The greatest common divisor of the number of teeth 44 and the number of captured images 360 is four. Divide 360 by 4 to get 90. That is, the same shape (or pattern) should be imaged at intervals of 90 degrees. In other words, four images in which the appearance of the workpiece W in each image is the same should be captured at intervals of 90 degrees. It should be noted that the term "substantially equal spacing" includes the spacing between positions close to the position where the same shape (or pattern) should be imaged. For example, when the same shape (or pattern) is not captured at a position where it should be captured, the image captured at a position similar to the position where the same shape (or pattern) should be captured is used as the first image A. Adopted. Therefore, the term “substantially equal intervals” is a concept that includes not only the case where the intervals are equal but also the case where the intervals are slightly deviated (for example, ±10 degrees or less).

The number of n is not limited to 4, but is preferably 3 or more in order to create an accurate reference image. When n is 4 or more, as will be described below, among the values of pixels whose positions in the appearance in the images are common to each other in the images adopted to create the reference image, the maximum value, the minimum value, and the can be removed and the average of the remaining values taken. On the other hand, when n is 3 or less, the maximum value and the minimum value among the values of the pixels whose positions in the appearance in the image are common to each other in the images adopted to create the reference image are If you leave it out, you can't take the average of the remaining values. Therefore, the number of n is preferably 4 or more. "The positions in the appearance in the image are common to each other" specifically means that each pixel for creating the reference image is common (corresponding) in the appearance of the work W reflected in the respective first images A. It includes the meaning of being located in a position to

Next, 360 captured images are transmitted from the imaging unit 3 to the CPU 51 of the control unit 5 . As a result, the four first images A are transmitted from the imaging unit 3 to the CPU 51 of the control unit 5 and stored in the RAM 53 (step S2) (storage step). Note that the imaging unit 3 may transmit to the control unit 5 sequentially each time it captures each image instead of transmitting to the control unit 5 after all 360 images have been captured. The RAM 53 functions as a storage section that stores the first image A. FIG. The first reference image R1 is created based on the four stored first images A shown in FIGS. 7 to 10 (step S3) (reference image creation step). Also, the first reference image R1 is created by the reference image creating unit 511 shown in FIG. The creation of the first reference image R1 will be described below.

The reference image creating unit 511 adopts m first images A, which are integers of 3 or more and n or less, as first creation images. Then, the reference image creation unit 511 creates the first reference image R1 based on the m first creation images. Of the four first images A stored in the RAM 53, for example, four first images A are employed as first creation images. A first reference image R1 is created based on this first creation image. Here, it is not limited to using four first images A as the first creation images. The number of first creation images may be a number m (here, 3 or less) that is smaller than the number n (here, 4) of the first images A stored. That is, other numbers may be adopted if n≧m.

A case where four first images A out of the four first images A stored in the RAM 53 are adopted as the first image for creation will be described below. First, the four first creation images are aligned at positions corresponding to each other. For this alignment, for example, the technique of "swaying process", which is a well-known technique described in Japanese Unexamined Patent Application Publication No. 2004-246110, is employed. A first reference image R1 is created using the values of four pixels that have common (corresponding) positions in the outer appearance of the outer periphery in the images of the four aligned first creation images. be. "The position of the outer peripheral portion in the image is common to each other" specifically means that four pixels are common (corresponding) in the appearance of the work W reflected in each of the first creation images. It includes the meaning of being located in a position.

FIG. 11 shows an example of values of four pixels (also referred to as “pixel values” in FIG. 11 and below) having common positions in the appearance of the outer peripheries in the images among the four first creation images. is a table showing In the example of FIG. 11, luminance is represented in grayscale. Among these values, the average value of each value excluding the maximum value and the minimum value is adopted for creating the first reference image R1. In the example table of FIG. 11, 187 values (maximum value) obtained at an angle of α+270 degrees and 95 values (minimum value) obtained at an angle of α+90 degrees are excluded. A value 115.5 obtained by averaging 125 values obtained at an angle of α degrees and 106 values obtained at an angle of α+180 degrees, excluding the above maximum and minimum values, is the value of the first reference image R1. It is adopted as the value of the predetermined pixel. Although an example of brightness values in grayscale is described here, color values may be employed instead of grayscale, and brightness may be employed instead of brightness.

Next, the sample image and the first reference image R1 are compared (step S4). The sample image is one first image A out of four first images A. The sample image does not have to be limited to the first creation image. Even if m of the n first images A are used as the first creation images to create the first reference image R1, the first images A other than the m first creation images are sampled. You may compare as an image. For the comparison between the sample image and the first reference image R1, for example, the technique of "swaying comparison", which is a well-known technique described in Japanese Unexamined Patent Application Publication No. 2006-269624, is employed. This "shaking comparison" is a technique of moving the arrangement of one of the image data to be compared, for example, up and down or left and right within a range of ±2 pixels. This "swaying comparison" corrects the positional deviation of pixels occurring between the sample image and the first reference image R1. Therefore, both images are compared with the original difference value at each pixel.

As a result of comparing both images, it is determined whether or not there is a defect in the outer periphery at the position where the sample image was captured (step S5) (determination step). When the value of each pixel in the sample image has a difference value equal to or greater than a predetermined value from the value of each pixel corresponding to the sample image of the first reference image R1, there is a defect in the outer peripheral portion at the position where this sample image was captured. is determined. On the other hand, when the value of each pixel in the sample image is a difference value less than a predetermined value from the value of each pixel corresponding to the sample image of the first reference image R1, a defect exists in the outer peripheral portion at the position where this sample image was captured. It is determined that there is no From the viewpoint of preventing over-detection of defects, minor flaws (for example, flaws on white straight lines) made during processing may be masked automatically or manually by an operator. A known image processing technique is used for the mask processing.

In step S5, when it is determined that there is a defect in the outer periphery at the position where the sample image was captured, the determination section 512 of the control unit 5 determines that the work W is defective (step S6), and the process ends. . On the other hand, if it is determined in step S5 that there is no defect in the outer periphery at the position where the sample image was captured, the control unit 5 determines that the work W is good (step S7). Then, other first images A among the four first images A are also sequentially determined as sample images as to whether or not there is a defect.

<Second Embodiment>
An inspection apparatus 200 according to the second embodiment will be described below. The inspection apparatus 200 of the present embodiment uses the first image A and the second image B to determine the quality of the workpiece W, which is different from the inspection apparatus 100 that uses only the first image A. FIG.

FIG. 12 is a flowchart showing the flow of quality judgment of the work W in the inspection apparatus 200 according to the second embodiment.

In the present embodiment, when determining whether the work W is good or bad, as in the first embodiment, the image capturing unit 3 captures images of the outer peripheral portion of the work W 360 times at intervals of 1 degree in the circumferential direction. 360 images including n first images A spaced substantially at regular intervals are captured (step S11) (imaging step). As in the first embodiment, for example, when the workpiece W has 44 teeth, the inspection camera 31 captures four first images A. As shown in FIG.

Next, 360 captured images are transmitted from the imaging unit 3 to the CPU 51 of the control unit 5 and stored in the RAM 53 (step S12) (image storage step). A first reference image R1 is created based on the first creation image selected from the four stored first images A (step S13) (first reference image creation step). The first reference image R1 created in step S13 is created by the same method as the method of creating the first reference image R1 described in the first embodiment. After that, the first sample image and the first reference image R1 are compared (step S14). The first sample image is one of the four first images A. As a result of comparing both images, it is determined whether or not there is a defect in the outer peripheral portion at the position where the first sample image was captured (step S15) (first determination step).

In step S15, when it is determined that there is no defect in the outer peripheral portion at the position where the first sample image was captured, the control unit 5 determines that the work W is good (step S23) (good/bad decision process). On the other hand, in step S15, if it is determined that there is a defect in the outer peripheral portion at the position where the first sample image was captured, the next second image B is determined. The reference image creation unit 511 acquires n second images B obtained by imaging the outer peripheral portion of the work W at approximately equal intervals in the circumferential direction from the 360 images stored in the RAM 53 . (Step S16) (Second Image Acquisition Step) For example, in this embodiment, as in the first embodiment, the workpiece W has 44 teeth, and the reference image creating unit 511 acquires four second images. Get image B. This second image B is different from any of the first images A. FIG. 13 is an explanatory diagram showing the relationship between the position where the first image A of the workpiece W is captured and the position where the adjacent second image B is captured. It is preferable that the angle θ between the position O at which the first image A is captured and the position P at which the adjacent second image B is captured about the axis of symmetry AX4 of the workpiece W be small. The angle θ between the position O at which the first image A is captured and the position P at which the adjacent second image B is captured is, for example, 1°, with the axis of symmetry AX4 of the workpiece W as the center.

Next, similarly to the creation of the first reference image R1, the reference image creation unit 511 adopts k second images B, which are integers of 3 or more and n or less, as second creation images. Then, the reference image creation unit 511 creates the second reference image R2 based on the k second creation images. Of the four second images B stored in the RAM 53, for example, four second images B are employed as second creation images. Here, it is not limited to adopting four second images B as the second creation images. The second creation image may be a number k (here, 3 or less) that is smaller than the number n (here, 4) of the stored second images B. That is, it suffices if the relationship n≧k is satisfied.

A second reference image R2 is created based on this second creation image (step S17). The second reference image R2 created in step S17 is also created by the same method as the method of creating the first reference image R1 described in the first embodiment.

After that, the second sample image and the second reference image R2 are compared (step S18). The second sample image is one second image B out of the four second images B. FIG. As a result of comparing both images, it is determined whether or not there is a defect in the outer peripheral portion at the position where the second sample image was captured (step S19) (second determination step).

In step S19, when the value of each pixel in the second sample image is a difference value less than a predetermined value from the value of each pixel corresponding to the sample image of the second reference image R2, this second sample image is captured. It is determined that the perimeter at the location is free of defects. In step S19, when it is determined that there is no defect in the outer peripheral portion at the position where the second sample image was captured, the control unit 5 determines that the work W is good (step S23) (defective determination step).

On the other hand, in step S19, when the value of each pixel in the second sample image has a difference value equal to or greater than a predetermined value from the value of each pixel corresponding to the second sample image of the second reference image R2, this second sample image It is determined that there is a defect in the outer periphery at the position where is imaged.

In step S19, when it is determined that there is a defect in the outer peripheral portion of the position where the second sample image was captured, image processing (hereinafter referred to as "moving processing ” is executed (step S20). FIG. 14 is an explanatory diagram showing the first sample image together with a portion recognized as a defect. FIG. 15 is an explanatory diagram showing the second sample image together with a portion recognized as a defect. FIG. 16 is an explanatory diagram showing a modified second sample image in which each pixel of the second sample image is moved according to the first sample image. Incidentally, in FIG. 15, the moving part of the part recognized as the defect to the second sample corrected image is indicated by the dotted line as an auxiliary.

Movement processing is performed by the control unit 5 . The moving process is performed by calculating the moving distance and moving direction of each pixel using a vector, for example, using a known optical flow technique. Specifically, in the second sample image, the moving distance and moving direction of the feature point on the image from the first sample image are calculated. The value of each pixel is moved in accordance with the first sample image by the amount of the movement distance and the movement direction, and a second sample corrected image is obtained. In this way, once the moving distance and moving direction of the feature point on the image are obtained, this value is also used for comparison between the second sample image and the first sample image at other positions.

Next, the first sample image and the second sample modified image are compared (step S21). As shown in FIG. 14, there are portions a, b, c, d, and e recognized as defects in the first sample image. On the other hand, as shown in FIG. 15, there are portions f, g, and h recognized as defects in the second sample image. FIG. 16 shows the result of vector movement of the second sample image using the optical flow technique. A second sample modification in which portions f, g, h recognized as defects in the second sample image are moved to portions i, j, k when each pixel of the second sample image is moved to match the first sample image. An image is obtained. Here, when the first sample image and the second sample corrected image are compared, among the parts a, b, c, d and e, the parts a, d and e match the parts i, j and k. That is, portions a, d, e and portions i, j, k are recognized as defects at the same position. The remaining non-matching portions b and c are not recognized as defects in the second sample image, and thus are determined to be overdetection of defects in the first sample image. Since portions a, d, and e are recognized as defects in the second sample as well, they are determined to be original defects. In this case, the control unit 5 determines that the workpiece W is defective (step S22). Conversely, if there is no portion recognized as a defect at the same position between the first sample image and the second sample corrected image, the control unit 5 determines that the work W is good (step S23).

Then, other first images A among the four first images A are sequentially determined as first sample images as to whether or not there is a defect.

<Others>
Although the number of sample images is four in the above-described embodiment, the number of sample images is not limited to this. In order to ensure sample images in which the same shape (or pattern) should be captured, it is preferable that there is a correlation between the period of the shape (or pattern) and the number of captured images. For example, the first image A (second image B) is captured at each angle of the greatest common divisor between 2π/the number of captured images and n with respect to the outer peripheral portion repeatedly provided with a period of 2π/n. is preferred. For example, if the number of teeth is 7 and the number of captured images is 360, there is no greatest common divisor of integers between 7 and 360. However, between 7 and 350, there is the greatest common divisor of the number 7. Therefore, in the above-described embodiment, 360 images are acquired by imaging the outer peripheral portion of the workpiece W every 1 degree in the circumferential direction. An image may be taken and seven first images A may be obtained. Also, the imaging position of the first image A (second image B) may be a position close to the position where the same shape (or pattern) should be imaged, and the same shape (or pattern) should be imaged. As a position approximating the position of , seven first images A (second images B) may be captured at intervals of 51 degrees to 52 degrees, which is a value close to 2π/7.

Further, in the above-described embodiment, when creating the first reference image R1, the average value of the values excluding the maximum value and the minimum value among the common pixel values of the first image for creation is adopted. but not limited to this. Even if the average value of the values excluding only the maximum value among the mutually common pixel values of the first creation image is adopted, the average value of the values excluding only the minimum value is adopted, or the median value is adopted , the average value of all values may be adopted. The same applies to the pixel values of the second creation image when creating the second reference image R2.

In the above-described embodiment, the inspection camera 31 is fixed to the support plate 34, but there is a configuration in which the inspection camera 31 moves in the circumferential direction about the axis of symmetry AX4 with respect to the workpiece W. May be adopted.

Further, in the above-described second embodiment, 360 images including the first image and the second image are acquired in step S11 (imaging step). It is also possible to pick up only n images, and if there is a defect in step S15 (first determination step), pick up n images to be the second image separately.

The embodiments disclosed this time are examples, and are not limited to the above-described contents. The scope of the present invention is indicated by the scope of claims, and is intended to include all modifications within the meaning and scope of equivalence to the scope of claims.

1 loading unit 2 workpiece holding unit 3 imaging unit 4 unloading unit 5 control unit 21A, 21B holding table 22 chuck mechanism 23 horizontal positioning mechanism 24 rotating mechanism 25 vertical positioning mechanism 26 position switching mechanism 27 alignment camera 31 inspection camera 32 inspection lighting section 33 base portion 34 support plate 35, 224 moving portion 36 arm 51 CPU
52 ROMs
53 RAM
100, 200 inspection device 221, 222, 223 movable member 225 protruding member 241 motor 251 holding plate 252 base plate 253 connecting pin 254 lifting section 261 support plate 262 rotating driving section 351 guide rail 352 driving section 511 reference image creating section 512 judging section A 1st image B 2nd image W Workpiece Wa Shaft Wb Gear PA Pre-alignment position PI Inspection position AX1 Turning axis AX4 Symmetry axis

Claims (10)

An inspection device for inspecting a workpiece having an outer peripheral portion in which a rotationally symmetrical shape or pattern is repeatedly provided with a period of 2π/n (n is an integer of 3 or more) about an axis of symmetry,
By imaging the outer peripheral portion while moving relative to the workpiece in the circumferential direction about the axis of symmetry, n first images of the outer peripheral portion are obtained at substantially equal intervals in the circumferential direction. an imaging unit that captures a plurality of images including
a storage unit that stores the n first images;
A position in appearance of the outer peripheral portion in the images between the m first creation images that are the m first images (integer of 3≦m≦n) among the n first images a reference image creation unit that creates a first reference image using the values of the m pixels located at positions common to each other;
A sample image, which is one of the n first images, is compared with the first reference image to determine whether or not there is a defect in the outer peripheral portion at the position where the sample image was captured. a judgment unit for judging;
inspection device. In the inspection device according to claim 1,
n≧4, m≧4,
The reference image creation unit creates the first reference image by adopting an average value of the m pixel values excluding the maximum value and the minimum value between the first creation images. inspection equipment. In the inspection device according to claim 1 or claim 2,
The plurality of images are different from any of the first images, and include the n second images spaced substantially at equal intervals along the outer peripheral portion in the circumferential direction,
The reference image creation unit is configured to, between the k second creation images, which are the k second images (an integer of 3≦k≦n) among the n second images, Further creating a second reference image using the values of the k pixels having a common position in the appearance of the outer peripheral portion of
The determining unit, when it is determined that there is a defect in the outer peripheral portion at the position where the sample image was captured, and the position where the second image adjacent to the position where the sample image was captured was captured. The inspection device determines that the outer peripheral portion is defective only when it is determined that the outer peripheral portion of the is defective. In the inspection device according to claim 3,
The inspection apparatus, wherein an angle between a position where the first image is captured and a position where the adjacent second image is captured is 1° around the axis of symmetry. An inspection method for inspecting a workpiece having an outer peripheral portion in which a rotationally symmetrical shape or pattern is repeatedly provided with a period of 2π/n (n is an integer of 3 or more) about an axis of symmetry,
A plurality of images including n first images of the outer peripheral portion at approximately equal intervals in the circumferential direction by imaging the work while moving relative to the work in the circumferential direction about the axis of symmetry. an image capturing step of capturing an image of
a storing step of storing the n first images;
Between the m first images for creation, which are m first images (integer of 3 ≤ m ≤ n) among the n first images, the appearance of the outer peripheral portion in the image a reference image creating step of creating a first reference image using the values of the m pixels whose positions are common to each other;
A sample image, which is one of the n first images, is compared with the first reference image to determine whether there is a defect in the outer peripheral portion at the position where the sample image was captured. a judgment step of judging;
An inspection method comprising: In the inspection method according to claim 5,
n≧4, m≧4,
In the reference image creation step, the first reference image is created by adopting an average value of the m pixel values excluding the maximum value and the minimum value between the first creation images. Inspection methods. In the inspection method according to claim 5 or claim 6,
The imaging step includes imaging the n second images that are different from any of the first images and are spaced substantially equal in the circumferential direction in the outer peripheral portion,
In the reference image creation step, between the k second creation images that are k second images (integer of 3 ≤ k ≤ n) among the n second images, further creating a second reference image using the values of the k pixels having a common position in the appearance of the outer peripheral portion;
The determining step determines that the outer peripheral portion is defective only when it is determined that the outer peripheral portion at the position where the second image adjacent to the position where the sample image is captured has a defect. ,Inspection methods. In the inspection method according to claim 7,
The inspection method, wherein an angle between a position where the first image is captured and a position where the adjacent second image is captured is 1° around the axis of symmetry. A program used in an inspection apparatus for inspecting a workpiece having an outer peripheral portion in which a rotationally symmetrical shape or pattern is repeatedly provided with a period of 2π/n (n is an integer of 3 or more) about an axis of symmetry,
The inspection device moves relative to the workpiece in a circumferential direction around the axis of symmetry, and captures n first images of the outer peripheral portion at substantially equal intervals in the circumferential direction. ,
a storage unit that stores the n first images,
In the inspection device, between the m first creation images which are m first images (an integer of 3 ≤ m ≤ n) among the n first images, the outer circumference in the image A program for creating a first reference image using the values of the m pixels whose positions in the appearance of the part are common to each other. In the program according to claim 9,
The inspection device compares a sample image, which is one of the n first images, with the first reference image, and the outer peripheral portion at the position where the sample image was captured. A program that determines the presence or absence of defects in

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