JP7415216B1 - Visual inspection equipment - Google Patents

Abstract

An object of the present invention is to provide an appearance inspection device that can obtain a clear image of a workpiece and perform accurate inspection while suppressing an increase in inspection time.
[Solution] The appearance inspection device of the present invention captures a plurality of captured images with different focus positions within a focus adjustment range, and selects a highly focused image with the highest degree of focus from among the captured multiple captured images. Then, it is determined whether the focus position of the selected high-focus image is in the intermediate region or the border region of the focus adjustment range, and if it is determined that it is in the intermediate region, the high-focus image is determined as the optimally focused image. However, if it is determined that it is a boundary area, the focus adjustment range is reset, multiple re-captured images with different focus positions are taken within the reset focus adjustment range, and the Select the highly focused image with the highest degree of focus.
[Selection diagram] Figure 2

Description

The present invention relates to an appearance inspection device that images the appearance of an object to be inspected (work).

BACKGROUND ART Appearance inspections have conventionally been carried out to check whether there is any abnormality in the shape of the workpiece, adhesion of foreign matter, etc. from an image obtained by capturing an image of the appearance of the workpiece with an imaging device such as a camera.

In such a visual inspection, the imaging device repeatedly captures images by changing the focus position of the imaging device by a predetermined pitch within a preset adjustment range to obtain a plurality of captured images. Then, the appearance of the workpiece may be inspected using the image with the highest degree of focus from among the plurality of captured images.

JP2018-87708A

However, because the distance between the workpiece and the imaging device changes due to dimensional tolerances of the workpiece and thermal contraction and expansion caused by temperature changes in the imaging environment, the optimal focus position may not exist within the adjustment range. In that case, the visual inspection is performed based on an unclear image, making accurate inspection difficult.

On the other hand, if the adjustment range is set wide, the workpiece can be imaged at the optimal focus position and a clear image can be obtained, but the number of times the image is taken increases and the inspection time becomes longer.

The present invention has been made in view of the above points, and an object of the present invention is to provide an appearance inspection device that can obtain a clear image of a workpiece and perform accurate inspection while suppressing an increase in inspection time. .

The present invention includes the embodiments shown below.

[1] An appearance inspection device that includes an imaging device that images a workpiece and a control unit that controls the imaging device , and performs an appearance inspection of the workpiece based on an optimally focused image , wherein the control unit Imaging processing that changes the focus position of the device within a focus adjustment range and causes the imaging device to image the workpiece at each focus position to generate a plurality of captured images; A selection process that calculates the degree of focus for the captured image and selects a high-focus image with the highest degree of focus, and defines an area within a predetermined range from the boundary of the focus adjustment range as a boundary area If an area other than the boundary area is an intermediate area, the high-focus image selected in the selection process is an image captured at the focus position of the intermediate area, or an image imaged at the focus position of the boundary area. a determination process for determining whether the high-focus image is an image taken at a focus position in the intermediate area, and a determination process for determining whether the high-focus image is optimally focused, on the condition that it is determined in the determination process that the high-focus image is an image captured at a focus position in the intermediate area. A determination process for determining the in-focus image, and a new image beyond the boundary area on the condition that the high-focus image is determined to be an image taken at the focus position of the boundary area in the determination process. a resetting process for setting a focus adjustment range, and changing the focus position of the imaging device within the new focus adjustment range, causing the imaging device to image the workpiece at each focus position, and re-imaging a plurality of times. re-imaging processing that generates an image; and re-selection processing that calculates the degree of focus for the plurality of re-imaging images generated in the re-imaging processing and selects a highly focused image with the highest degree of focus. and an external appearance inspection device that sets the focus adjustment range in the image capturing process from the next time onwards based on the focus position at which the optimally focused image was captured .

[2] The control unit executes the determination process, the determination process, the resetting process, the reimaging process, and the reselection process on the high-focus image selected in the reselection process. The appearance inspection device according to [1] above.

[3] The control unit selects the high-focus image with the highest degree of focus from among the high-focus image selected in the selection process and the high-focus image selected in the re-selection process. The visual inspection device according to [1] or [2] above, which determines the optimally focused image.

[ 4 ] Any one of [1] to [ 3 ] above, wherein the pitch at which the focus position of the imaging device is changed in the re-imaging process is smaller than the pitch at which the focus position of the imaging device is changed in the imaging process. The appearance inspection device described in .

[ 5 ] The visual inspection device according to [2] above, wherein the control unit executes a notification process for canceling the re-imaging process and notifying an error if the resetting process continues for a threshold number of times. .

[ 6 ] The control unit executes a notification process for notifying an error without executing the determination process when the degree of focus of the highly focused image selected in the selection process is lower than a threshold value. 1]～
The appearance inspection device according to any one of [ 5 ].

According to the present invention, it is possible to acquire a clear image of a workpiece and perform accurate inspection while suppressing an increase in inspection time.

A diagram showing a schematic configuration of an appearance inspection device according to an embodiment of the present invention Flowchart showing a method for visually inspecting a workpiece W using a visual inspection device 2 is a graph illustrating the relationship between the focus position of a captured image and the degree of focus, in which (a) shows a case where a high focus image is an image captured at a focus position in a boundary area, and (b) shows a case where a high focus image is an image captured at a focus position in a boundary area. A case is shown in which the image is captured at a focus position in the intermediate region.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

(1) Configuration of visual inspection device 1 First, the configuration of visual inspection device 1 of this embodiment will be described based on FIG. 1. The appearance inspection device 1 includes a stage 2, an imaging device 3, and a control device 5, and the imaging device 3 photographs a workpiece W placed on the stage 2, and based on the captured image obtained by photographing. This is a device for inspecting a workpiece W.

On the stage 2, a workpiece W to be inspected is placed. An imaging device 3 is provided above a workpiece W placed on a stage 2.

The imaging device 3 includes a housing 32 in which an imaging sensor 31 is provided, a lens barrel 34 that holds an inspection lens 33, and an optical system drive device 35 that moves the focus position of the inspection lens 33.

In the imaging device 3, the inspection lens 33 is arranged to face the upper surface of the workpiece W placed on the stage 2 in the vertical direction. The optical system driving device 35 moves the inspection lens 33 in a direction parallel to the optical axis to adjust the focus of the image formed on the image sensor 31. Thereby, the imaging device 3 magnifies the upper surface of the workpiece W placed on the stage 2 with the inspection lens 33, which is an optical system, and images it with the imaging sensor 31.

The control device 5 includes a processing device 51 consisting of a computer and a storage device 52 such as a memory, and when the processing device 51 reads and executes a program stored in the storage device 52, the imaging processing unit 53, functions as a data acquisition section 54, a selection processing section 55, a determination processing section 56, a determination processing section 57, a resetting processing section 58, a reimaging processing section 59, a reselection processing section 60, and an evaluation section 61.

The imaging processing unit 53 controls the imaging sensor 31 and the optical system driving device 35 of the imaging device 3 to perform imaging processing. The imaging processing unit 53 changes the focus position from the start position to the end position, and causes the imaging device 3 to image the work W every time the focus position changes by a predetermined amount, thereby generating a plurality of captured images with different focus positions. let

That is, the imaging processing unit 53 sets the range (focus adjustment range) Rp in which the focus position is changed and the amount of change (focus pitch) Δf in the focus position between adjacent captured images, and focuses within the focus adjustment range Rp. The imaging device 3 is caused to generate a plurality of captured images P whose positions differ by a focus pitch Δf.

In the following description, the image captured at the start position is referred to as the first captured image P1, the image captured at the end position is referred to as the n-th captured image Pn, and the 1st to nth captured images P1 to Pn are referred to as the first captured image P1. These are collectively referred to as captured images P.

The data acquisition unit 54 acquires data of a plurality of captured images P generated by the imaging device 3. The data acquisition unit 54 associates the data of the acquired captured image P with the number of the captured image P (that is, the ordinal number of the captured image P). The data linked in the data acquisition unit 54 is stored in the storage device 52.

The selection processing unit 55 performs a selection process of selecting a highly focused image from a plurality of captured images P generated in the imaging process.

Specifically, the selection processing unit 55 reads the plurality of captured images P generated by the imaging device 3 from the storage device 52, and calculates the degree of focus of each of the plurality of captured images P. Various methods can be adopted as a method for calculating the degree of focus. For example, the selection processing unit 55 calculates a sharpness value for each captured image P, and a captured image with a larger sharpness value is an image with a higher degree of focus. I evaluate it as.

Then, the selection processing unit 55 selects the captured image P with the highest degree of focus among the calculated degrees of focus as the high-focus image, and stores the result in the storage device 52.

The determination processing unit 56 determines whether the high focus image selected by the selection processing unit 55 or the high focus image selected by the reselection processing unit 60 is an image captured at a focus position in the boundary area of the focus adjustment range Rp. , a determination process is performed to determine whether the image is captured at a focus position in the middle area of the focus adjustment range Rp.

Here, the boundary area of the focus adjustment range Rp is an area within a predetermined range from the start position and end position of the focus adjustment range Rp. Further, the intermediate area is an area excluding the boundary areas on the start position side and the end position side.

For example, when 50 captured images P are captured by changing the focus position within the focus adjustment range Rp, the boundary area is twice the focus pitch Δf from the start and end positions of the focus adjustment range Rp. This can be the area up to the focused position. At this time, the first to third captured images P1 to P3 and the 48th to 50th captured images P48 to P50 are images captured at the focus position of the boundary area of the focus adjustment range Rp, The fourth to forty-seventh captured images P4 to P47 are images captured at focus positions in the middle region of the focus adjustment range Rp.

The determination processing unit 57 performs determination processing to determine the highly focused image determined by the determination processing unit 56 to be an image captured at a focus position in the intermediate region as the optimally focused image.

On the other hand, if the determination processing unit 56 determines that the highly focused image is an image captured at the focus position of the boundary area, the resetting processing unit 58 moves the boundary area where the highly focused image was captured to the outside. A resetting process is performed to set a new focus adjustment range Rp' that exceeds the range Rp'.

In setting the new focus adjustment range Rp', the resetting processing unit 58 sets the new focus adjustment range Rp' so that it overlaps with the boundary area where the highly focused image was captured in the original focus adjustment range Rp. .

For example, the relationship between the focus position and the focus degree of the plurality of captured images P becomes as shown in FIG. When it is determined that the image is a captured image, the resetting processing unit 58 performs a new focus adjustment on a range in which the focus adjustment range Rp is shifted toward the end position so as to include the boundary area of the original focus adjustment range Rp. The range Rp' is set (see FIG. 3(b)).

More specifically, when the focus adjustment range Rp is set so that the focus position changes from the back to the front of the workpiece W from the start position to the end position, the focus position in the boundary area on the end position side When the captured image is selected as a highly focused image, the reset processing unit 58 sets a range in which the start position and end position are shifted toward the front side of the workpiece W as a new focus adjustment range Rp'. At that time, the start position of the new focus adjustment range Rp' is arranged further back of the workpiece W than the boundary area on the end position side of the original focus adjustment range Rp, and the new focus adjustment range Rp' is set to the original focus adjustment range Rp'. It overlaps with the boundary area on the end position side of the range Rp.

The re-imaging processing unit 59 processes a plurality of captured images whose focus positions differ by a focus pitch Δf′ within the new focus adjustment range Rp′ set in the re-setting processing unit 58 (these captured images are referred to as “re-imaging images”). re-imaging processing that causes the imaging device 3 to generate P' is performed.

The data of the plurality of re-imaged images P' generated by the imaging device 3 is determined by the data acquisition unit 54 according to its ordinal number (the number indicating the number of the re-imaged image from the re-imaged image taken at the starting position). The information is linked and stored in the storage device 52.

Note that the focus pitch Δf′ set in the re-imaging processing unit 59 may be the same size as the focus pitch Δf set in the imaging processing unit 53, or may be the same size as the focus pitch Δf set in the imaging processing unit 53. It may be smaller than Δf.

The reselection processing unit 60 performs reselection processing to select a highly focused image from a plurality of reimaging images P' generated in the reimaging processing.

Specifically, the reselection processing unit 60 reads the plurality of re-imaging images P' generated by the re-imaging processing unit 59 from the storage device 52, and calculates the degree of focus for each of the plurality of re-imaging images P'. do. Then, the re-selection processing unit 60 selects the re-captured image P' having the highest degree of focus among the calculated degrees of focus as the high-focus image, and stores the result in the storage device 52.

The method of calculating the degree of focus in the reselection processing section 60 can be the same as the method of calculating the degree of focus in the selection processing section 55, and various methods can be adopted, for example, sharpness The re-captured image P' with a larger sharpness value is evaluated as having a higher degree of focus.

The evaluation unit 61 then performs an external appearance inspection of the workpiece W based on the captured image P determined as the optimally focused image by the determination processing unit 57.

(2) Inspection method using the appearance inspection apparatus 1 The appearance inspection method of the workpiece W using the above-mentioned appearance inspection apparatus 1 will be explained with reference to FIGS. 2 and 3.

First, the imaging processing unit 53 performs imaging processing in which the workpiece W placed on the stage 2 is imaged by the imaging device 3 while changing the focus position from the start position to the end position by the focus pitch Δf within the focus adjustment range Rp. . As a result, a plurality of captured images P whose focus positions differ by a focus pitch Δf are generated (step S1).

Next, in the selection processing unit 55, the control device 5 calculates the degree of focus of each of the plurality of captured images P generated by the imaging device 3, and selects the captured image with the highest degree of focus among the calculated degrees of focus. A selection process is performed to select P as a highly focused image (step S2).

Next, in the determination processing unit 56, the control device 5 determines whether the captured image selected or reselected as a high-focus image in step S2 and step S6, which will be described later, is an image captured at a focus position in an intermediate region of the focus adjustment range Rp. A determination process is performed to determine whether or not (step S3).

The relationship between the focus position and the degree of focus of the plurality of captured images P is illustrated in FIG. 3(a), and the captured image selected as the highly focused image is an image captured in the boundary area of the focus adjustment range Rp. If so (No in step S3), the process advances to step S4.

In step S4, the resetting processing unit 58 performs resetting processing to set a new focus adjustment range Rp' that extends outside the boundary area where the highly focused image is captured. For example, as shown in FIG. 3(a), if the captured image selected as the high-focus image is an image captured at the focus position of the boundary area on the end position side, as shown in FIG. 3(b), , a new focus adjustment range Rp' is set so as to extend outward beyond the boundary area on the end position side.

Next, the re-imaging processing unit 59 images the workpiece W placed on the stage 2 with the imaging device 3 while changing the focus position by the focus pitch Δf' within the new focus adjustment range Rp' to obtain a re-imaging image. generate. Thereby, re-imaging processing is performed to generate a plurality of re-imaging images P' in which the focus positions differ by the focus pitch Δf' (step S5).

Next, in the reselection processing unit 60, the control device 5 calculates the focus degree of each of the plurality of re-imaging images P' generated by the imaging device 3, and selects the focus degree that is the highest among the calculated focus degrees. A reselection process is performed to reselect the highly re-captured image P' as a highly focused image (step S6).

After re-selecting the high-focus image, the process returns to step S3 and the new focus adjustment range Rp' is continued until the captured image re-selected as the high-focus image is captured at a focus position in the middle area of the focus adjustment range Rp'. A resetting process (step S4) for setting a re-imaged image P' (step S5), and a reselection process (step S6) for reselecting a highly focused image are repeatedly performed.

On the other hand, as shown in FIG. 3(b), if the captured image selected or reselected as a high-focus image in step S2 and step S6 is an image captured in the middle region of the focus adjustment range Rp, (step (Yes in S3) Proceed to step S7. Then, the determination processing unit 57 performs a determination process to determine the captured image selected as the highly focused image as the optimally focused image (step S7), and based on the captured image P determined as the optimally focused image by the evaluation unit 61. The appearance of the workpiece W is inspected (step S8).

(3) Effect In the visual inspection apparatus 1 of this embodiment, when a highly focused image is captured at the focus position of the boundary area, the focus adjustment range Rp is changed to generate a re-captured image P' and a highly focused image. Even if the focus position is outside the focus adjustment range Rp, a clear image of the workpiece W can be obtained at the optimal focus position. .

In addition, in the appearance inspection apparatus 1 of this embodiment, when a highly focused image is captured at a focus position in the intermediate region, the appearance inspection of the workpiece W is performed based on the highly focused image without changing the focus adjustment range. Therefore, a captured image is not generated while changing the focus position over an unnecessarily wide range, and an increase in inspection time can be suppressed.

(4) Modification Examples The embodiments of the present invention have been described above, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and gist of the invention as well as within the scope of the invention described in the claims and its equivalents. An example of the change will be explained below. Note that any one of the plurality of modification examples described below may be applied to the above embodiment, or any two or more of the modification examples described below may be applied in combination. It's okay. Note that various changes are possible in addition to the following example of change.

(4-1) Change example 1
In the above-described embodiment, if the high-focus image selected by the selection processing unit 55 is an image captured at a focus position in the boundary area of the focus adjustment range, it is higher than the image captured at a focus position in the intermediate area. The resetting process, reimaging process, reselection process, and judgment process were repeated until the focused image was selected, but the resetting process, reimaging process, and reselection process were performed only once, and the reselection process The appearance of the workpiece W may be inspected based on the selected highly focused image.

In addition, if a high-focus image is not selected from the images captured at a focus position in the middle area of the focus adjustment range, and the resetting process is continuously executed a predetermined threshold number of times D, that is, the resetting process , re-imaging processing, re-selection processing, and determination processing are taken as one cycle. If each processing is repeated for a predetermined threshold number of cycles D, the processing device 51 does not perform any further resetting processing and does not notify the user of the error. You may perform notification processing to notify.

(4-2) Change example 2
In the embodiment described above, when it is determined in the determination process that the high-focus image selected in the selection process is an image taken at the focus position of the boundary area, the resetting process, the reshooting process, and the reselection process are performed. The high-focus image selected in the re-selection process was used for the visual inspection of the workpiece W as the optimally focused image. Among the images, a highly focused image with the highest degree of focus may be set as the optimally focused image.

(4-3) Change example 3
In the embodiment described above, the processing device 51 may set the focus adjustment range for subsequent imaging processing based on the focus position where the optimally focused image was captured.

For example, when the determination processing unit 57 determines the optimally focused image, the processing device 51 stores in the storage device 52 the focus position at which the optimally focused image was captured (hereinafter, this position will be referred to as the "optimal focus position"). The focus adjustment range may be set based on the stored optimal focus position when executing the next imaging process.

As a method of setting the focus adjustment range based on the optimum focus position, for example, the focus adjustment range can be set such that the optimum focus position is the center of the focus adjustment range. In addition, the optimal focus position used for setting the focus adjustment range may be the optimal focus position obtained in the most recent inspection, or the average value of the optimal focus positions obtained in the most recent multiple inspections. may be set.

(4-4) Change example 4
In the embodiment described above, if the degree of focus of the highly focused image selected in the selection process is lower than the threshold value, the processing device 51 may perform a notification process to notify the user of an error without performing the determination process.

1... Visual inspection device 2... Stage 3... Imaging device 5... Control device 31... Imaging sensor 32... Housing 33... Inspection lens 34... Lens barrel 35... Optical system drive section 51... Processing device 52... Storage device 53... Imaging Processing unit 54...Data acquisition unit 55...Selection processing unit 56...Determination processing unit 57...Determination processing unit 58...Resetting processing unit 59...Reimaging processing unit 60...Reselection processing unit 61...Evaluation unit

Claims (6)

A visual inspection device that includes an imaging device that images a workpiece and a control unit that controls the imaging device , and that performs a visual inspection of the workpiece based on an optimally focused image ,
The control unit includes:
Imaging processing that changes the focus position of the imaging device within a focus adjustment range and causes the imaging device to image the workpiece at each focus position to generate a plurality of captured images;
a selection process of calculating a degree of focus for the plurality of captured images generated in the image capturing process and selecting a highly focused image with the highest degree of focus;
If an area within a predetermined range from the boundary of the focus adjustment range is defined as a boundary area, and an area other than the boundary area of the focus adjustment range is defined as an intermediate area, the highly in-focus image selected in the selection process is an area within the intermediate area. determination processing for determining whether the image is an image taken at a focus position or an image taken at a focus position of the boundary area;
a determination process of determining the highly focused image as the optimally focused image on the condition that the highly focused image is determined to be an image captured at a focus position in the intermediate region in the determination process;
Resetting to set a new focus adjustment range outside the boundary area, on the condition that the highly focused image is determined to be an image taken at a focus position in the boundary area in the determination process. processing and
re-imaging processing of changing the focus position of the imaging device within the new focus adjustment range and causing the imaging device to image the workpiece at each focus position to generate a plurality of re-imaging images;
Calculating the degree of focus for the plurality of re-imaging images generated in the re-imaging process, and performing a re-selection process of selecting a highly focused image with the highest degree of focus ;
An appearance inspection device that sets the focus adjustment range in the image capturing process from next time onwards based on the focus position at which the optimally focused image was captured . 2. The control unit executes the determination process, the determination process, the reset process, the re-imaging process, and the re-selection process on the high-focus image selected in the re-selection process. The appearance inspection device described in . The control unit brings the high-focus image with the highest degree of focus out of the high-focus image selected in the selection process and the high-focus image selected in the re-selection process into the optimal focus. The appearance inspection device according to claim 1, wherein the appearance inspection device is determined to be an image. The external appearance inspection apparatus according to claim 1, wherein a pitch at which the focus position of the imaging device is changed in the reimaging process is smaller than a pitch at which the focus position of the imaging device is changed in the imaging process. The external appearance inspection apparatus according to claim 2, wherein the control unit executes a notification process of canceling the re-imaging process and notifying an error when the resetting process continues a threshold number of times. The control unit executes a notification process of notifying an error without executing the determination process when the degree of focus of the highly focused image selected in the selection process is lower than a threshold value. Appearance inspection equipment.

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