JP2019200525A - Image processing system for visual inspection, and image processing method - Google Patents

Abstract

To improve the efficiency of a visual inspection process of a structure by correcting the color tone of a picked-up image to color tone which easily undergoes visual inspection.SOLUTION: An image processing system for visual inspection for performing color tone correction of a picked-up image of an imaging machine includes: an imaging machine for outputting a picked-up image obtained by imaging an inspection object; a light source for applying light to an imaging range of the imaging machine; an attenuation factor calculation unit for calculating a light attenuation factor in the vicinity of the inspection object on the basis of the picked-up image when the imaging machine and the light source are arranged substantially to face each other in the vicinity of the inspection object; a color tone attenuation factor calculation unit for calculating the color tone attenuation amount of each pixel of the inspection object in the picked-up image on the basis of the light attenuation factor, a distance between the imaging machine and the inspection object, a distance between the light source and the inspection object, a light source intensity, and a light reception intensity in the picked-up image in imaging the inspection object; and a color tone correction unit for correcting the color tone of each pixel of the inspection object in the picked-up image on the basis of the color tone attenuation amount of each pixel calculated by the color tone attenuation amount calculation unit.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image processing apparatus that processes an image used when a structure is visually inspected, and an image processing method used in the image processing apparatus.

  Visual inspection is one of the methods for inspecting the soundness of social infrastructure structures such as tunnels and bridges and buildings such as power plants. In visual inspection, an inspector directly views an inspection target area or indirectly visually recognizes an image captured by an imaging device such as a camera to determine the presence or absence of a defect. When the inspection target area is in a high place or narrow area, or in a harsh environment such as in liquid, high temperature, or high radiation environment, it is difficult to see the inspection target directly. In many cases, a visual inspection is performed by an inspector at a distant place indirectly viewing an image captured by the image pickup device through a liquid crystal display or the like.

  Thus, when an inspector performs an indirect visual inspection, it is necessary to provide the inspector with a high-visibility image that is easy to determine defects, and in particular, an image that accurately reproduces the color tone of the inspection target area. Providing it is important in properly determining the presence or absence of defects. For example, when light of a specific wavelength is attenuated and enters the imaging device with respect to the original color tone of the inspection target area, the light intensity of the specific wavelength is recorded weakly in the image, and the inspection target area has the original color tone. Since it is displayed on the liquid crystal display or the like in a different manner, there is a possibility that the inspector may mistakenly determine whether there is a defect.

  As a technique for solving such a problem, for example, there is a proposal of Patent Document 1. In the abstract of this document, as a means for “providing a surface inspection apparatus that does not require much knowledge about color, corrects color without much trouble, and can accurately inspect defects”, A surface inspection apparatus for irradiating light on the surface of an object to be inspected (semiconductor wafer W) and observing an image to be imaged, comprising a display unit that displays the color tone characteristics of the image to be imaged in accordance with the color tone characteristics of a standard image A device that corrects the color tone of an acquired image using a color tone characteristic of a standard image captured in advance as a reference value.

JP 2008-89424 A

  In an environment in which social infrastructure structures and buildings are visually inspected, the conditions of the spatial medium in the environment and the conditions such as the illumination device and the arrangement of the imaging device during imaging vary greatly, so the color tone of the captured image can vary greatly. There is sex. However, Patent Document 1 is to inspect the surface of a semiconductor wafer under an environment such as a factory where the arrangement of lighting, cameras, etc. is fixed, as is apparent from the drawings of the abstract of the same document, Although a color tone correction method under a certain condition in which a standard image is acquired is considered, a significant color tone correction corresponding to a change in conditions is not considered.

  The present invention has been made in view of such circumstances, and an object of the present invention is to allow an inspector to easily determine a defect by visual inspection of an image of a region to be inspected under an environment in which imaging conditions can vary greatly. An object of the present invention is to provide an image processing apparatus and an image processing method for correcting color tone.

  In order to solve the above problems, an image processing system for visual inspection according to the present invention corrects a color tone of an image captured by an image capturing device, and outputs an image captured by capturing an inspection object; A light source that irradiates light to an imaging range of an imaging device, and an optical attenuation factor in the vicinity of the inspection object based on a captured image when the imaging device and the light source are disposed substantially opposite to each other in the vicinity of the inspection object An attenuation rate calculation unit for obtaining the light attenuation rate, the distance between the imaging device and the inspection object, the distance between the light source and the inspection object, the light source intensity, and the image of the inspection object Based on the received light intensity in the captured image, a hue attenuation amount calculation unit that calculates the color tone attenuation amount of each pixel of the inspection object in the captured image, and for each pixel calculated by the color tone attenuation amount calculation unit The inspection object in the captured image based on a color tone attenuation amount A color correction unit for correcting the color tone of each pixel of and intended to comprise a.

  According to the present invention, even when an image of a region to be inspected is imaged in an environment in which the imaging conditions can vary greatly, it is possible to correct the color tone so that an inspector can easily determine a defect by visual inspection. .

1 is a schematic diagram of an image processing system according to Embodiment 1. FIG. 3 is a flowchart illustrating an image processing method according to the first exemplary embodiment. The flowchart which shows the detail of the attenuation factor calculation process of FIG. FIG. 3 is a perspective view illustrating an arrangement of devices when calculating an attenuation factor according to the first embodiment. FIG. 3 is a side view showing device arrangement when calculating an attenuation factor according to the first embodiment. FIG. 4 is a diagram illustrating an example of a captured image when calculating an attenuation rate according to the first embodiment. FIG. 3 is a perspective view illustrating a device arrangement when calculating a color tone attenuation amount according to the first exemplary embodiment. FIG. 3 is a schematic diagram of an image processing system according to a second embodiment. 9 is a flowchart illustrating an image processing method according to the second embodiment. The perspective view which shows the apparatus arrangement | positioning at the time of the light source distance calculation of Example 2. FIG. FIG. 10 is a top view illustrating an arrangement of devices when calculating a light source distance according to the second embodiment. FIG. 10 is a diagram illustrating an example of a captured image when calculating a light source distance according to the second embodiment. FIG. 10 is a diagram illustrating an example of a captured image when calculating a light source distance according to the second embodiment. FIG. 6 is a top view illustrating an apparatus arrangement when calculating an imager distance according to the second embodiment. FIG. 6 is a diagram illustrating an example of a captured image when calculating an imager distance according to the second embodiment. FIG. 6 is a top view illustrating an apparatus arrangement when calculating an imager distance according to the second embodiment. FIG. 6 is a diagram illustrating an example of a captured image when calculating an imager distance according to the second embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

  The image processing system and the image processing method according to the first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a schematic diagram illustrating an image processing system according to a first embodiment together with an inspection target region 1. The inspection target area 1 shown here is a surface of a social infrastructure structure or building where an inspector performs a visual inspection, and the image processing system of the present embodiment mainly has the inspection target area 1 of the inspection target. An image pickup device 2 having a part of the image pickup range 2a, a light source 3 having a part of the inspection target region 1 as an irradiation range 3a, and an image processing device 4 for correcting the picked-up image 2c of the image pickup device 2 to a color tone that is easy to visually inspect. And the display device 5 that provides the inspector with the corrected image 2d subjected to the color tone correction. In addition, an image pickup device position measuring device 2b for measuring the distance to the front obstacle is attached to the image pickup device 2, and a light source position measuring device 3b for measuring the distance to the front obstacle is also attached to the light source 3. Yes. These position measuring devices are, for example, laser distance meters, but other types of sensors may be used as long as they can measure the distance to the front obstacle.

  The imaging device 2 and the light source 3 are mounted on a remote control moving body that freely moves in the vicinity of the inspection target region 1 in accordance with a command from the image processing device 4. The remote control moving body is, for example, a drone if the inspection target area 1 is at a high place, and a submersible craft if the inspection target area 1 is underwater. In the following, a configuration in which the image pickup device 2 and the light source 3 are separately mounted on separate moving bodies will be described as an example. However, the image pickup device 2 and the light source 3 are installed on each of two movable arms provided in one moving body. However, the arrangement of both the movable arms may be individually controlled by individually controlling both the movable arms.

  The image processing apparatus 4 receives the output signals of the image pickup device 2, the image pickup device position measuring device 2b, and the light source position measuring device 3b, and applies the image processing of the present embodiment to the picked-up image 2c of the image pickup device 2 based on them. In order to realize this, an attenuation rate calculation unit 4a, a storage unit 4b, a color tone calculation image acquisition unit 4c, a color tone attenuation amount calculation unit 4d, a color tone calculation unit 4e, and an image color tone correction unit 4f are included. Specifically, the image processing apparatus 4 includes hardware such as an arithmetic device such as a CPU, a main storage device such as a semiconductor memory, an auxiliary storage device (storage unit 4b) such as a hard disk, and a communication device. A computer, such as a personal computer, that implements each of the functions described above by executing a program loaded in the main storage device. The following description will be made while omitting such well-known techniques as appropriate. To do.

Next, the details of the image processing executed by the image processing apparatus 4 will be described with reference to FIGS. 2 to 7 while clarifying the execution subject of each processing.
<Processing of Step S2 by Decay Rate Calculation Unit 4a>
FIG. 2 is a flowchart of an image processing method performed by the image processing apparatus 4 of the present embodiment. When image processing for visual inspection is started (step S1), the attenuation rate calculation unit 4a first calculates the attenuation amount (attenuation rate A) of light per distance, which is basic data for performing color tone correction, The calculated attenuation rate A and light source intensity are stored in the storage unit 4b (step S2).

  FIG. 3 is a flowchart for explaining details of step S2. When the attenuation factor calculation unit 4a starts the attenuation factor calculation process (step S2), first, the moving object equipped with the image pickup device 2 and the moving object equipped with the light source 3 are moved to a reference position for calculating the attenuation factor A. (Step S21). When both moving bodies reach the reference position (step S22), the captured image 2c of the image pickup device 2 at that position is acquired (step S23), and the light source intensity (light source emission amount L) of the light source 3 is also acquired. (Step S24). Then, based on the acquired light source intensity (light source emission amount L), brightness of the light source 3 in the captured image 2c (image pickup light reception amount B), and the distance D between the image pickup device 2 and the light source 3 at the reference position. The amount of light attenuation (attenuation rate A) is calculated.

  Next, the calculation method of the attenuation factor A in step S2 will be described in more detail with reference to FIGS. FIG. 4 is a perspective view showing a state at step S22 in which the image pickup device 2 and the light source 3 that have reached the attenuation rate calculation position (reference position) are substantially opposed to each other, and the distance between the image pickup device 2 and the light source 3 at this time. Is the distance D. Note that step S2 for calculating the attenuation rate A is a process of acquiring basic data for correcting the captured image 2c of the inspection target region 1 to a color tone that is easy to visually inspect, and therefore the attenuation rate calculation position (reference) in step S22. The position) needs to be in the same quality environment as the vicinity of the inspection target region 1. Here, the “homogeneous environment” means, for example, various conditions such as the type (air, fresh water, seawater), pressure, temperature, medium density, particle density, particle diameter, etc. of the spatial medium in the vicinity of the inspection target region 1. Specifically, when the inspection target region 1 is in turbid water, it is an environment in the same amount of turbid water, and more preferably in the vicinity of the inspection target region 1.

  When the image pickup device 2 and the light source 3 reach the reference position, the attenuation rate calculation unit 4a measures the distance D between them. In this measurement, the distance to the other side may be set to the distance D by the image pickup device position measuring device 2b or the light source position measuring device 3b, or the image pickup device 2 may be separated from the image pickup device 2 so that the attenuation rate calculating unit 4a is separated from the specified distance. When a command is issued to each moving body on which the light source 3 is mounted, the specified distance may be the distance D. Further, the distance D may be calculated based on the captured image 2c of the imaging device 2.

  Here, a method for calculating the distance D from the captured image 2c of the imaging device 2 will be described with reference to FIGS. FIG. 5 is a side view of the image pickup device 2 and the light source 3 that have reached the reference position, where f is a light beam width at the light source exit end, and θ is a light source spread angle. FIG. 6 is a diagram showing a captured image 2c of the image pickup device 2 at the reference position and a light source incident area 3c in the captured image 2c, where R in the figure is an incident area width in real space of the light source incident area 3c. It is. In the examples of FIGS. 5 and 6, the light beam shape of the light source 3 is circular. However, other light beam shapes may be used as long as the light beam width f, the spread angle θ, and the incident region width R are obtained. For example, it may be a rectangle.

  At this time, the distance D is expressed by (Expression 1).

  In addition, the attenuation rate calculation unit 4a calculates the image sensor received light amount B based on the luminance value of the pixel region corresponding to the light source incident region 3c in the captured image 2c. Then, based on the distance D, the light source emission amount L, and the imaging device received light amount B acquired by the above processing, the light attenuation rate A at the reference position, which is an environment substantially the same as the vicinity of the inspection target region 1, is obtained. The attenuation rate A is expressed by (Expression 2).

As described above, the attenuation rate A is obtained and stored as attenuation rate data in the storage unit 4b.
<Processing of Steps S3 to S6 by Color Tone Calculation Image Acquisition Unit 4c>
When the attenuation rate A and the light source intensity (the light source emission amount L) are acquired in step S2, the color tone calculation image acquisition unit 4c moves the moving object in which the imaging device 2 and the light source 3 are mounted to the vicinity of the inspection target region 1. Command. Then, when the image pickup device 2 moves to a position where the inspection target area 1 can be imaged and the light source 3 moves to a position where the image pickup range 2a can be irradiated with light (step S4), the image pickup device position measuring device 2b and the light source position measurement are performed. with vessel 3b, the distance D ₁ of the from the imaging device 2 to the inspection area 1, (step S5) while measuring a distance D ₂ from the light source 3 to the inspection object area 1, controls the imaging unit 2 and the light source 3 Then, an image of the inspection target region 1 irradiated with light is taken (step S6).
<Processes of Steps S7 to S9 by Color Tone Attenuation Calculation Unit 4d>
Thereafter, the color tone attenuation amount calculation unit 4d acquires the attenuation rate data (attenuation rate A), light source intensity data (light source emission amount L), distance data (distance D ₁ , distance D ₂ ), and captured image acquired by the above-described processing. Using the data (captured image 2c), a color tone attenuation amount is calculated (step S7), and the color tone calculation unit 4e calculates color tone information based on the color tone attenuation rate (step S8). Further, the image tone correction unit 4f corrects the tone of the captured image 2c using the tone information, and generates a corrected image 2d (step S9).

Next, details of the processing of steps S7 to S9 will be described by taking the situation shown in FIG. 7 as an example. When step S6 is completed, the image processing apparatus 4 according to the present exemplary embodiment has the attenuation rate data (attenuation rate A), light source intensity data (light source emission amount L), distance data (distance D ₁ , distance D ₂ ), and imaging. Image data (captured image 2c) has been acquired. In this case, the color tone of the surface to be inspected based on the current imaging device received light amount B ′ obtained from the current captured image data 2c, and the known light source emission light amount L, distances D ₁ and D ₂ , and attenuation factor A. It is possible to calculate the light amount attenuation amount LD determined by the spectral reflectance characteristic. The light amount attenuation amount LD due to the color tone of the surface to be inspected is calculated for each pixel of the captured image 2c and is expressed by (Equation 3).

That is, the light amount attenuation amount LD is further calculated from the difference between the light source intensity (light source light emission amount L) and the image pickup device received light amount (current image pickup device received light amount B ′), and the attenuation amount derived from the distance (A · (D ₁ + D _2). )) Is subtracted. The light amount attenuation amount LD due to the color tone of the surface to be inspected is uniquely determined by the spectral reflection characteristic determined by the color tone information of the surface to be inspected, and the color tone information of the surface of the area to be inspected is calculated from this value. By the above method, the original color tone is calculated for each pixel on the surface of the inspection target area in the captured image 2c. Here, the method for obtaining the attenuation rate due to light of one specific wavelength is described. However, the respective attenuation factors are obtained by switching light of a plurality of wavelengths and synthesized in the captured image color tone correction step S13 shown below. May be corrected. For example, the light source 3 that switches light of three wavelengths corresponding to the three primary colors of light, red, green, and blue, is provided, and the color tone is adjusted by obtaining and combining the respective attenuation factors A _R , A _G , and A _B. A corrected image 2d may be obtained. At this time, the wavelength selection of light can be freely selected at a plurality of wavelengths so as to obtain a target image, and is not limited to the visible wavelength range. The light source switching method may be any means capable of switching a plurality of wavelengths. For example, a plurality of light sources may be used, or any means capable of switching a target wavelength, such as switching using a wavelength filter. Not limited to this.

  When Step S7 to Step S9 are completed and the imaging of a part of the inspection target region and the correction processing of the captured image 2c are completed, whether or not the imaging of all planned inspection regions is completed in the all region inspection completion determination step S14. Determine. If there are other areas to be inspected, the process returns to step S3 again, and after moving the image pickup device 2 and the light source 3 to the vicinity of the next area to be inspected 1 (steps S3 and S4), Processing from image acquisition to tone correction in the inspection target area 1 is executed. When imaging of all the inspection target areas 1 is completed, the process proceeds to step S11, and the image processing for visual inspection is ended.

  The corrected image 2d obtained by the above image processing method is sent from the image processing device 4 to the display device 5 and displayed as an inspection image used for defect determination. In this way, the corrected image 2d displayed on the display device 5 is corrected to a color tone that is easy to visually inspect regardless of the difference in the imaging environment of the inspection target region 1. Even when the region 1 is visually inspected, stable defect determination can be realized.

  Next, an image processing system and an image processing method according to the second embodiment of the present invention will be described with reference to FIGS. Note that common explanation with the first embodiment is omitted.

In the image processing system according to the first embodiment, the distances D ₁ and D ₂ are measured using the imaging device position measuring device 2b and the light source position measuring device 3b. However, in this embodiment, these position measuring devices are omitted. Further, a step of calculating a distance corresponding to the distances D ₁ and D ₂ using the captured image 2c is provided.

  FIG. 8 is a schematic view showing the image processing system of this embodiment together with the structure to be inspected. As shown here, the image processing apparatus 4 according to the present embodiment includes a distance calculation image acquisition unit 4g, an illumination distance calculation unit 4h, an imaging distance calculation unit 4i, and a light source switching unit 4j, as compared with FIG. 1 of the first embodiment. It is added.

FIG. 9 is a flowchart of the image processing method of this embodiment. Compared with FIG. 2 of the first embodiment, this image processing method replaces the step S5 of measuring the distance using the position measuring device, and the distance calculation image acquisition step S5a for detecting the distance based on the captured image 2c. , Distance calculation step S5b, and light source switching step S5c are provided. Hereinafter, the details of Steps 5a to 5c will be described with reference to FIGS.
<Step S5a>
In step S5a, first, a structured illumination pattern 3d composed of two light beams as shown in the perspective view of FIG. The structured illumination pattern 3d, as shown in the top view of FIG. 11, one is collimated light beam width LW ₁ in the horizontal direction, beam width LW 2 of the other horizontal _spread angle theta ₂ of the spread light It is. Here, for simplicity of explanation, one of the structured illumination patterns 3d is parallel light, but both may be spread light having different divergence angles.

When such a structured illumination pattern 3d is used, a structured illumination pattern 3d whose appearance changes according to the distance between the light source 3 and the inspection target region 1 is recorded in the captured image 2c of the imaging device 2. For example, the inspection when the target region 1 is in the position of the inspection area 1 _A of FIG. 11, the captured image 2c of the imaging device 2 structured illumination pattern 3d shown in FIG. 12 is captured, the inspection target region 1 is 11 If there in the position of the inspection area 1 _B, the captured image 2c of the imaging device 2 structured illumination pattern 3d shown in FIG. 13 is captured. That is, one beam width W ₁ is constant regardless of the distance, the other beam width W ₂ is proportional to the distance.
<Step S5b>
By utilizing such properties, in step 5b, the illumination distance calculating section 4h, based upon the pickup image 2c, shown in Figure 11, the distance D ₃ from the light source 3 to the center position of the inspection area 1, ( Calculated by equation 4). W ₁ and W ₂ are actual widths of the respective light beams irradiated on the inspection target region 1.

Thus, to calculate the distance D ₃ from the light source 3 to the inspection object area 1. Also, when the spread angle in the height direction of the structured illumination pattern 3d in this case the theta _3, the arrangement angle phi ₂ of the light source 3 shown in Figure 11 is calculated by (Equation 5).

Then, according to the imaging distance calculation unit 4i, a method of calculating the distance D ₄ from the imaging device 2 to the inspection area 1 will be described with reference to FIGS. 14 to 17.

As shown in the top view of FIG. 14, when the imaging device 2 faces the inspection target region 1, a captured image 2 c shown in FIG. 15 is obtained from the imaging device 2. At this time, the imaging distance D _4, by using the imager focal length F, is calculated by (Equation 6).

As shown in the top view of FIG. 16, when the imaging device 2 has an angle of φ ₃ with respect to the inspection target region 1, a captured image 2 c shown in FIG. 17 is obtained from the imaging device 2. At this time, the imaging distance D ₄ is calculated by (Expression 7), and φ ₃ is calculated by (Expression 8).

Thus, even in a configuration in which omit the position measuring device, based on the captured image 2c, the distance D ₄ from the imaging device 2 to the inspection area _1, and a distance D ₃ from the light source 3 to the inspection object area 1 Can be requested.
<Step S5c>
Next, step S5c will be described. The structured illumination pattern 3d irradiated by the light source 3 after step S5a does not irradiate the entire imaging range 2a, and is not suitable for capturing an image for inspection. Therefore, in accordance with a command from the light source switching unit 4j, the irradiation pattern of the light source 3 is switched to one that can irradiate the entire imaging range 2a before step S6 of acquiring the captured image 2c for inspection. The illumination pattern to be switched may be switched between a plurality of patterns so as to illuminate the entire imaging range. For example, a pattern that interpolates a region that is not illuminated in the structured illumination pattern 3d may be projected. In that case, the captured image 2c may be generated by combining the image captured when the structured illumination pattern 3d is irradiated and the image captured after the light source is switched.

According to the configuration of the present embodiment described above, even if the position measuring device is omitted, the distance D ₄ from the imaging device 2 to the inspection target region 1 and the light source 3 based on the captured image 2c. from it is possible to obtain the distance D ₃ to the inspection object area 1, using these in the same manner as in example 1, it is possible to generate a corrected image 2d subjected to color correction suitable for the defect detection by visual inspection The inspector can perform a stable defect determination via the display device.

1 inspection area,
2 imaging machine,
2a imaging range,
2b Imager position measuring device,
2c captured image,
2d corrected image,
3 Light source,
3a Irradiation range,
3b Light source position measuring device,
3c light source incident area,
3d structured lighting pattern,
4 image processing device,
4a Attenuation rate calculation unit,
4b storage unit,
4c color tone calculation image acquisition unit,
4d tone attenuation calculation unit,
4e color tone calculation unit,
4f Image color tone correction unit,
4g distance calculation image acquisition unit,
4h Illumination distance calculation unit,
4i imaging distance calculation unit,
4j light source switching unit,
5 display devices

Claims (6)

An image processing system for visual inspection that corrects a color tone of a captured image of an imager,
An imaging device that outputs a captured image obtained by imaging the inspection object;
A light source that irradiates light to an imaging range of the imaging device;
An attenuation rate calculation unit for obtaining a light attenuation rate in the vicinity of the inspection object based on a captured image when the imaging device and the light source are disposed substantially opposite to each other in the vicinity of the inspection object;
The light attenuation rate, the distance between the imaging device and the inspection object, the distance between the light source and the inspection object, the light source intensity, and the received light intensity in the captured image when the inspection object is imaged, A color tone attenuation amount calculating unit that calculates a color tone attenuation amount of each pixel of the inspection object in the captured image;
A color tone correction unit that corrects the color tone of each pixel of the inspection object in the captured image based on the color tone attenuation amount of each pixel calculated by the color tone attenuation amount calculation unit;
An image processing system for visual inspection, comprising: An imager position measuring device for measuring a distance between the imager and the inspection object;
A light source position measuring device for measuring a distance between the light source and the inspection object;
The image processing system for visual inspection according to claim 1, comprising:   It further comprises a distance calculation processing unit that calculates a distance between the imaging device and the inspection object and a distance between the light source and the inspection object based on a captured image obtained by imaging the inspection object. The image processing system for visual inspection according to claim 1.   The light source emits a light distribution pattern having two or more different light divergence angles when the image pickup device picks up a picked-up image provided for distance calculation by the distance calculation processing unit. Item 4. The image processing system for visual inspection according to Item 3. The light source switches and irradiates light of two or more wavelengths,
The image processing system for visual inspection according to any one of claims 1 to 4, wherein the color correction unit synthesizes a color correction image for each wavelength. An image processing method for visual inspection for correcting a color tone of a captured image,
Obtaining the light attenuation factor in the vicinity of the inspection object based on the captured image when the imaging device and the light source are arranged substantially opposite each other in the vicinity of the inspection object,
Irradiating the inspection object with light,
Imaging the inspection object,
The light attenuation rate, the distance between the imaging device and the inspection object, the distance between the light source and the inspection object, the light source intensity, and the received light intensity in the captured image when the inspection object is imaged, On the basis of the color tone attenuation amount of each pixel of the inspection object in the captured image,
Correcting the color tone of each pixel of the inspection object in the captured image based on the calculated color tone attenuation amount of each pixel;
An image processing method for visual inspection characterized by the above.

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