JP7426297B2 - Inspection equipment - Google Patents

Description

The present invention relates to a lighting device and an inspection device, and relates to a technique that is effective when applied to inspecting the inner wall of a container such as a nuclear reactor, for example.

Japanese Unexamined Patent Publication No. 2003-185783 (Patent Document 1) describes an inspection device that images the inside of a nuclear reactor pressure vessel with a camera and performs a visual inspection using the image. Japanese Unexamined Patent Application Publication No. 2011-317788 (Patent Document 2) describes a method for visually recognizing defects such as cracks in concrete from differences in images taken by selectively lighting a plurality of lights. PCT Publication No. 2019-517003 (Patent Document 3) is not an inspection device for the inner wall of a container, but it describes a difference between a line image captured under dark field illumination and a line image captured under bright field illumination. describes a method for identifying areas of high reflectance on the surface of a sheet element such as paper.
The configuration is described.

Japanese Patent Application Publication No. 2003-185783 Japanese Patent Application Publication No. 2011-317788 Special table 2019-517003 publication

One method of inspecting defects such as cracks on the inner wall of a container such as a nuclear reactor is to place a camera inside the container and illuminate the inner wall, which is the surface to be inspected, to take an image. If the container is made of a metal, such as stainless steel, the inner wall surface is generally a reflective surface, but with some regions having a diffuse texture. As described above, when inspecting for cracks on an inner wall surface where reflective surfaces and diffusive surfaces coexist, it is difficult to distinguish between cracks and diffusive texture in the obtained image.

An object of the present invention is to provide a technique that makes it easier to detect defects such as cracks when inspecting a surface to be inspected that includes a mixture of reflective surfaces and diffusive surfaces.

An illumination device according to an embodiment includes a reflected light illumination unit that irradiates light that is reflected by the test surface and enters the camera, and a diffuser that irradiates light that is diffused by the test surface and enters the camera. A light illumination section. Within the field of view of the camera, there is a virtual image of the light source of the reflected light illumination unit with the test surface as a virtual mirror surface, and a virtual image of the light source of the diffused light illumination unit with the test surface as a virtual mirror surface. There is no virtual image of the light source.

An inspection apparatus according to another embodiment includes a camera that captures an image of a surface to be inspected, a reflected light illumination unit that irradiates light that is reflected by the surface to be inspected and enters the camera, and a light that is diffused by the surface to be inspected. and a diffused light illumination unit that irradiates light that enters the camera. Within the field of view of the camera, there is a virtual image of the light source of the reflected light illumination unit with the test surface as a virtual mirror surface, and a virtual image of the light source of the diffused light illumination unit with the test surface as a virtual mirror surface. There is no virtual image of the light source.

According to the invention disclosed in this application, defects such as cracks can be easily detected when inspecting a surface to be inspected in which a reflective surface and a diffusive surface coexist.

Problems, configurations, and effects other than those described above will be made clear by the following description of the embodiments.

FIG. 1 is an explanatory diagram schematically showing a configuration example of an inspection device according to an embodiment. FIG. 2 is a plan view of the illumination device shown in FIG. 1 viewed from the direction of the optical axis of the camera. FIG. 2 is an explanatory diagram schematically showing a connection relationship of brightness control units included in the lighting device shown in FIG. 1. FIG. 2 is an explanatory diagram schematically showing a path of light emitted from the reflected light illumination section shown in FIG. 1. FIG. FIG. 2 is an explanatory diagram schematically showing the path of light emitted from the diffused light illumination section shown in FIG. 1. FIG. FIG. 2 is a plan view showing a portion of the surface to be inspected shown in FIG. 1; 7 is an enlarged sectional view taken along line AA shown in FIG. 6. FIG. FIG. 7 is a diagram illustrating a difference in how an image appears depending on the balance of brightness between bright field illumination (reflected light illumination) and dark field illumination (diffuse light illumination) on the test surface shown in FIG. 6; FIG. 2 is an explanatory diagram showing a processing flow of a system that automatically adjusts the brightness of bright field illumination and dark field illumination. 10 is an explanatory diagram showing a configuration example of a computer that implements each step of balance adjustment shown in FIG. 9. FIG. FIG. 2 is a cross-sectional view of main parts schematically showing a configuration example of an inspection device that is a modification of FIG. 1; FIG. 2 is a cross-sectional view of main parts schematically showing a configuration example of an inspection device that is another modification to FIG. 1; 13 is an explanatory diagram schematically showing a path of light emitted from the reflected light illumination section shown in FIG. 12. FIG. 13 is an explanatory diagram schematically showing a path of light emitted from the diffused light illumination section shown in FIG. 12. FIG.

In each of the drawings for explaining the embodiments below, the same members are designated by the same reference numerals in principle, and repeated explanations thereof will be omitted. Additionally, functionally similar elements may be labeled with the same or corresponding numbers. Further, in the following description, hatching may be added even to plan views to make the drawings easier to understand. Although the attached drawings show embodiments and implementation examples in accordance with the principles of the present disclosure, they are for the purpose of understanding the present disclosure, and should not be used to limit the present disclosure in any way. isn't it. The description herein is exemplary.

Although the embodiments are described in sufficient detail for those skilled in the art to implement the present disclosure, other implementations and forms are possible without departing from the scope and spirit of the technical idea of the present disclosure. It is necessary to understand that it is possible to change the composition and structure and replace various elements.

In the following description of the embodiment, an inspection device for detecting cracks (defects) occurring in the inner wall of a pressure vessel of a nuclear reactor will be explained as an example of the inspection device (and a lighting device that is a part of the inspection device). . However, the techniques described below are applicable to various modifications.

<Example of configuration of inspection device>
FIG. 1 is a sectional view of main parts schematically showing an example of the configuration of an inspection apparatus according to the present embodiment. In FIG. 1, the viewing range 105 of the camera 110 through the lens 112, which is an imaging lens, is shown by a two-dot chain line, and the optical axis 113 of the camera 110 is shown by a one-dot chain line. FIG. 2 is a plan view of the illumination device shown in FIG. 1 viewed from the direction of the optical axis of the camera. FIG. 3 is an explanatory diagram schematically showing the connection relationship of the brightness control units included in the lighting device shown in FIG. 1. 4 is an explanatory diagram schematically showing the path of light emitted from the illumination section for reflected light shown in FIG. 1, and FIG. 5 is an explanatory diagram schematically showing the path of light emitted from the illumination section for diffused light shown in FIG. FIG. An inspection apparatus 100 shown in FIG. 1 is an apparatus that images an inner wall surface, which is a surface to be inspected (surface to be inspected) 102, of a nuclear reactor (vessel) 101 with a camera 110, and detects cracks 104, which are defects. A method for inspecting the surface to be inspected 102 of the nuclear reactor 101 using the inspection apparatus 100 will be described below.

The inspection apparatus 100 includes a camera 110 that captures an image of the surface to be inspected 102, and an illumination device (illumination section) 200 that illuminates the surface to be inspected 102. The illumination device 200 includes a reflected light illumination unit (bright field illumination unit) 210 that irradiates light that is reflected by the test surface 102 and enters the camera 110, and a reflected light illumination unit (bright field illumination unit) 210 that irradiates light that is reflected by the test surface 102 and enters the camera 110. It has a diffused light illumination unit (dark field illumination unit) 220 that irradiates the light. Furthermore, within the field of view 105 of the camera 110, there is a virtual image 211 of the light source of the reflected light illumination unit 210 that uses the surface to be inspected 102 as a virtual mirror surface, and a diffused light that uses the surface to be examined 102 as a virtual mirror surface. There is no virtual image 221 of the light source of the illumination unit 220. In other words, the virtual image 211 is within the viewing range 105 of the camera 110 and the virtual image 221 is outside the viewing range 105 of the viewing range 105.

The camera 110 includes an image sensor 111 and a lens (imaging lens) 112 arranged between the image sensor 111 and the test surface 102. The surface to be measured 102 exists on an extension of the optical axis 113 that connects the image sensor 111 and the lens 112. The lens 112 has a viewing angle range that is restricted by conditions such as the range in which an image can be formed on the image sensor 111. This angle of view range corresponds to the viewing range 105 of the camera 110.

Camera 110 is electrically connected to transmission circuit 120. The transmission circuit 120 is electrically connected to the display device 123 via a cable 121 and an image processing circuit 122. The image captured by the camera 110 is converted by the transmission circuit 120 into a video signal of a digital video signal standard such as SDI, HDMI, or GigE, and is transmitted to the image processing circuit 122. The video signal is processed in the image processing circuit 122 and transmitted to the display device 123. The display device 123 can display the video imaged by the camera 110 in real time. Therefore, for example, when an operator is present in front of the display device 123, the operator can observe the state of photography by the camera 110 or the state of the test surface 102 based on the displayed image on the display device 123. .

Camera 110 and transmission circuit 120 are housed within a housing 106 made of a metal such as tungsten or lead that attenuates radiation. When inspecting the surface to be inspected 102, the casing 106 is carried into the nuclear reactor 101. The cable 121 is provided so as to penetrate the housing 106 and is led out to the outside of the nuclear reactor 101. As described above, since the parts (camera 110 and transmission circuit 120) carried into the reactor 101 are covered by the housing 106, the camera 110 and the transmission circuit 120 may malfunction due to the influence of radiation inside the reactor 101. can be restrained from doing so.

As shown in FIG. 2, each of the reflected light illumination unit 210 and the diffused light illumination unit 220 is a ring illumination formed in an annular shape, and is arranged around the optical axis 113 of the camera 110 (see FIG. 1) and the lens 112. will be placed in In the example shown in FIG. 2, a ring-shaped reflected light illumination section 210 is arranged around the optical axis, and a ring-shaped diffused light illumination section 220 is arranged around the outer periphery. Each of the reflected light illumination unit 210 and the diffused light illumination unit 220 includes a light source such as an LED (Light Emitting Diode) (not shown), and a diffusive light guide plate (not shown) that converts the light output from the light source into a surface light source. Equipped with.

As shown in FIG. 3, the lighting device 200 controls the brightness (light amount) of the light emitted from the reflected light illumination section 210 and the brightness (light amount) of the light emitted from the diffused light illumination section 220. It has a brightness control section (light amount control section) 230 that controls the brightness. The reflected light illumination section 210 is electrically connected to the brightness control section 230 via a cable 212. The diffused light illumination section 220 is electrically connected to the brightness control section 230 via a cable 222. The brightness control unit 230 can control the brightness of each of the reflected light illumination unit 210 and the diffused light illumination unit 220 independently of each other. For example, the brightness of either one of the reflected light illumination section 210 and the diffused light illumination section 220 can be set to zero (unlit state). The brightness control unit 230 is built into the camera 110 in FIG. 1, for example. Alternatively, the cables 212 and 222 may be placed outside the nuclear reactor 101 and extended to the outside of the reactor 101.

As described using FIG. 1, within the viewing range 105 of the camera 110 included in the inspection apparatus 100 of this embodiment, there is a light source of the reflected light illumination unit 210 that uses the inspection surface 102 as a virtual mirror surface. There is a virtual image 211, but there is no virtual image 221 of the light source of the diffused light illumination unit 220 that uses the surface to be inspected 102 as a virtual mirror surface. In this case, as schematically shown by the dotted line in FIG. 4, the light 213 emitted from the reflected light illumination section 210 is reflected by the test surface 102 and received by the camera 110. Specifically, light 213 reflected by the surface to be measured 102 is received by the image sensor 111 via the lens 112. Further, as shown in FIG. 5, the light 223 emitted from the diffused light illumination section 220 is reflected by the test surface 102 and is not received by the camera 110. Specifically, since the light 223 reflected by the surface to be inspected 102 is reflected toward a position other than the lens 112, the reflected light is not received as a result. On the other hand, a part of the light diffused by the test surface 102 enters the lens 112 shown in FIGS. 4 and 5, and is received by the image sensor 111 via the lens 112.

In the case of an inspection method using the inspection apparatus 100, a reflected light illumination section 210 and a diffused light illumination section 220 are used, respectively. By adjusting the relationship between the virtual images 211 and 221 and the viewing range 105 of the camera 110, the light 213 (see FIG. 4) emitted from the reflected light illumination unit 210 is mainly reflected light, which is received by the camera 110. Of the light 223 emitted from the diffused light illumination unit 220, only the diffused light is received by the camera 110.

As described using FIG. 2, the reflected light illumination section 210 and the diffused light illumination section 220 are ring illuminations, and have an opening in the center for arranging the lens 112. Further, as shown in FIG. 1, the virtual image 211 of the light source of the reflected light illumination unit 210 does not exist on the optical axis 113 of the camera 110, and there is a hole. For this reason, there is a concern that the area (central area) near the point overlapping the optical axis 113 on the surface to be inspected 102 is difficult to observe compared to the surrounding area. However, as described below, when inspecting the surface to be inspected 102, the virtual image 211 is photographed in a blurred state. That is, when inspecting the surface to be inspected 102, the lens 112 is arranged so as to focus on the surface to be inspected 102. Therefore, the virtual image 211 of the light source of the reflected light illumination unit 210 is out of focus, and the virtual image 211 is photographed in a blurred state. Therefore, the boundary between the hole caused by the opening in which the lens 112 is placed and its surroundings becomes blurred, and light spreads. As a result, the hole is relaxed in the direction in which this light is filled. Furthermore, since the blurred image is corrected in the image processing circuit 122, the corrected image can be confirmed when viewed on the display device 123.

<Control of two types of lighting>
Next, a method of controlling and inspecting the brightness of the reflected light illumination section 210 and the diffused light illumination section 220 will be described. FIG. 6 is a plan view showing a portion of the test surface shown in FIG. 1. FIG. FIG. 7 is an enlarged sectional view taken along line AA shown in FIG.

In the case of a metal container wall as in this embodiment, the wall surface is considered to be composed only of surfaces that can be regarded as almost mirror surfaces that reflect most of the incident light specularly. However, upon investigation by the inventor of the present application, it was found that regions having mutually different optical properties were distributed. That is, as shown in FIGS. 6 and 7, the test surface 102 has a region 131 with a diffusive characteristic in which more diffused light is scattered than specularly reflected light, and a region 131 that has a diffusive characteristic where more specularly reflected light is scattered than specularly reflected light. a region 132 with more reflective properties. The region 132 having reflective characteristics has optical characteristics that can be regarded as a substantially mirror surface. Diffuse regions 131 are distributed between reflective regions 132. It is necessary to detect the crack 104 in such a state that the optical characteristics of the base surface are not constant.

As shown in FIG. 7, the crack 104 has a V-shaped valley-like shape in cross-sectional view. Due to the nature of the crack 104, the depth 104D tends to be longer (deeper) than the width 104W of the crack 104. For example, if the width 104W is about 10 μm, the depth 104D is about 10 mm. When light enters when the V-shaped valley has a narrow width 104W and a deep depth 104D like the crack 104, it is absorbed while being reflected many times on both sides of the V-shaped valley. As a result, it is assumed that most of the light is not emitted to the outside of the test surface 102 and is not apparently reflected or scattered. However, when imaging a narrow crack 104 with a width of 104W using the camera 110 (see FIG. 1), it is assumed that the width of the geometric image of the crack 104 is smaller than the pixel size of the image sensor 111. In this case, the image of the crack 104 that is output as an image is brighter than originally because the contrast is reduced by the ratio of the area of the image of the geometric crack 104 within that pixel to the area of the pixel. Identified from the surroundings. Therefore, the crack 104 is also not completely dark, but is recognized as a decrease in brightness from the brightness around the crack 104.

FIG. 8 is a diagram showing the difference in how an image appears depending on the brightness balance between bright field illumination (reflected light illumination) and dark field illumination (diffuse light illumination) on the surface to be inspected shown in FIG. 6. In FIG. 8, image 240A shows a condition where the bright field illumination brightness is too strong relative to the dark field illumination brightness. Image 240B shows a state in which the brightness of bright field illumination and dark field illumination are well balanced and the crack 104 is easily visible. Image 240C shows a condition where the brightness of the darkfield illumination is too strong relative to the brightness of the brightfield illumination.

When the bright field illumination has high brightness, as in image 240A, the reflective region 131 appears bright and the diffuse region 131 appears dark. In this case, it is difficult to distinguish between the crack 104 and the region 131, and the visibility of the crack 104 is reduced. On the other hand, when the dark field illumination is strong, as in the image 240C, the region 131 appears dark and the region 132 appears bright. In this case, it is difficult to distinguish between the crack 104 and the region 131, and the visibility of the crack 104 is reduced. In the case of image 240B, visibility of crack 104 is improved by controlling the brightness of each of the bright field and dark field illumination independently of each other. In the example of the image 240B, the brightness is adjusted so that the areas 131 and 132 that are visible in the images 240A and 240C have the same brightness. In other words, the brightness difference between the region 131 and the region 132 is adjusted to be small. As a result, the difference between the image of the crack 104 and the images of other parts becomes clear, and the visibility of the crack 104 improves. Practically speaking, the probability of the existence of the crack 104 is considered to be smaller than the probability of the existence of the smaller area of the region 131 and the region 132. Therefore, in adjusting the luminance balance described above, the adjustment is not made so that the crack 104 is not visible.

Note that the image 240B in FIG. 8 shows an ideal state in which the brightness of the area 131 and the area 132 are exactly the same. However, even if there is a slight difference in brightness between the regions 131 and 132, as long as the crack 104 can be detected visually or by circuit-based detection processing, and within a range that can prevent or suppress false detection, good.

Adjustment of the brightness of each of the bright field illumination and dark field illumination described above, in other words, adjustment of the brightness of the reflected light illumination section (bright field illumination) 210 and the diffused light illumination section (dark field illumination) 220 shown in FIG. This can be done manually, for example, by an operator. The operator, who is an inspection worker, makes full use of the images displayed on the display device 123 in real time to adjust the contrast of images other than the crack 104 shown in FIG. 8 to be reduced. The condition of the surface to be inspected 102 is unlikely to be uniform, and it is expected that the condition of the surface to be inspected 102 will vary if the object to be inspected changes. For example, if there is a viewing range in the entire test surface 102 in which there are few reflective regions 132 and mostly diffuse regions 131 as shown in FIGS. 6 and 7, or vice versa, A case may be considered in which the region 132 is reflective. Furthermore, when inspecting one surface to be inspected 102 by imaging it in a plurality of visual field ranges, it is conceivable that the state of the surface to be inspected 102 differs depending on the visual field range. In this way, when the distribution of the reflective region 132 and the diffusive region 131 is uneven on the surface to be inspected 102, as one aspect of balance adjustment, the illumination section 220 for diffused light and the illumination section 210 for reflected light Adjustments may be made in which one of the lights is turned on and the other is turned off.

<Automatic control of balance adjustment>
Next, a system that automatically performs the above-mentioned brightness balance adjustment using the image processing circuit shown in FIG. 1 will be described. FIG. 9 is an explanatory diagram showing a processing flow of a system that automatically adjusts the brightness of bright field illumination and dark field illumination. FIG. 10 is an explanatory diagram showing an example of the configuration of a computer that implements each step of the balance adjustment shown in FIG. 9. The computer 125 shown in FIG. 10 is a device that constitutes a part of the inspection apparatus 100 shown in FIG. 1, and includes the image processing circuit 122 shown in FIG. 230, and a determination processing unit 126 that determines whether or not the brightness needs to be changed in step S13 shown in FIG. Each step will be described as a process executed by the computer 125 shown in FIG.

The brightness balance adjustment system shown in FIG. 9 includes steps S11, S12, S13, S14, and S15. In step S11, first, the brightness control section 230 (see FIG. 10) of the computer 125 (see FIG. 10) turns on the diffused light illumination section 220 (see FIG. 10), which is dark field illumination. In this state, the camera 110 shown in FIG. 1 captures an image within the field of view of the surface to be inspected 102. In step S12 following step S11, the image processing circuit 122 of the computer 125 performs a two-dimensional Fourier transform (FFT: Fast Fourier Transform) on the image data acquired from the image sensor 111, and converts the direct current (DC) component into The brightness of the AC (Alternating Current) component other than the DC component normalized by the brightness of the DC component is calculated.

In step S13, the determination processing unit 126 (see FIG. 10) of the computer 125 calculates a value obtained by dividing the brightness of the AC component by the brightness of the DC component (hereinafter referred to as AC/DC) and a preset reference value. Compare and determine whether the calculation result is less than the reference value. The determination processing section 126 determines the brightness of the light emitted from the reflected light illumination section 210 (see FIG. 10) and the diffused light illumination section 220 (see FIG. 10) based on the image data captured by the camera 110 (see FIG. 1). 10)) is provided with a function of determining whether or not it is necessary to change the brightness of at least one of the brightnesses of the light emitted from the light source. In the example of the system shown in FIG. 9, the determination processing unit 126 determines whether the brightness of the light emitted from the reflected light illumination unit 210 needs to be changed. In the FFT image calculation in step S12, the spatial spectrum of the image is calculated. As illustrated in FIG. 6, when the surface to be inspected 102 includes a diffusive region 131 and a reflective region 132, the reference value is set so that AC/DC is equal to or greater than the reference value.

In step S13, when it is determined that AC/DC is equal to or higher than the reference value, the determination processing unit 126 of the computer 125 shown in FIG. data) is output to the brightness control section 230. In step S14, the brightness control section 230 of the computer 125 shown in FIG. 2 turns on the reflected light illumination section 210, which is bright field illumination, based on the determination data transmitted from the determination processing section 126. Alternatively, if the reflected light illumination section 210 is already turned on, the brightness of the reflected light illumination section 210 is increased. Thereafter, in step S13, the computer 125 repeatedly executes steps S12 to S14 until AC/DC becomes less than the reference value.

In step S13, if it is determined that AC/DC is less than the reference value, the brightness balance is adjusted. At this time, the determination processing unit 126 of the computer 125 shown in FIG. 10 outputs the above-described determination processing data indicating that the brightness does not need to be changed to the brightness control unit 230. Further, the determination processing unit 126 outputs adjustment completion data to the image processing circuit 122. In step S15, the image processing circuit 122 of the computer 125 shown in FIG. 10 outputs image data to the display device 123 shown in FIG. 1 based on the adjustment completion data received from the determination processing section 126.

In addition, in FIG. 9, the method of first turning on the dark-field illumination and then adjusting the brightness of the bright-field illumination was exemplified, but as a modified example, after turning on the bright-field illumination first, This may be a method of adjusting the brightness of field illumination. Further, the brightness of the illumination turned on in step S11 may be the maximum value, but may be about half to 70% of the maximum brightness. In this case, the determination processing unit 126 of the computer 125 uses a feedback loop to change the brightness of one or both of the dark field illumination and the bright field illumination according to the AC/DC value used for the determination process. In some cases, a method of configuring the

As described above, by automating the balance adjustment of the brightness of bright field illumination and dark field illumination, it is possible to reduce the work burden on the operator who is an inspection worker and to stabilize the standard for balance adjustment.

<Modification 1>
Next, a modification of the inspection apparatus 100 shown in FIG. 1 will be described. FIG. 11 is a cross-sectional view of essential parts schematically showing a configuration example of an inspection device that is a modification of FIG. 1. In FIG. The inspection apparatus 100A shown in FIG. 11 differs from the inspection apparatus 100 shown in FIG. Furthermore, the inspection apparatus 100A is different from the inspection apparatus 100 shown in FIG.

Specifically, the camera 110 of the inspection device 100A includes a lens 112 that is an imaging lens, and an image sensor 111 that receives light (detection light) via the lens 112. A reflective mirror 114 is arranged in the optical path between the lens 112 and the image sensor 111. The image sensor 111 and the reflection mirror 114 are housed in a metal housing 106. The housing 106 is formed with an opening 106H into which the lens 112 is attached. The image sensor 111 is arranged at a position away from an extension line VL1 of a virtual line that linearly connects the opening 106H and the reflecting mirror. The housing 106 has a bent shape, and the image sensor 111 is disposed at a position different from the extension of the opening. In this case, even if radiation within the nuclear reactor 101 enters the housing 106 through the opening 106H, direct irradiation of the image sensor 111 can be suppressed. Therefore, failure or malfunction of the image sensor 111 due to the influence of radiation can be suppressed.

The inspection apparatus 100A is the same as the inspection apparatus 100 shown in FIG. 1 except for the above-mentioned differences. Therefore, duplicate explanations will be omitted. Although the reference numerals are omitted in FIG. 1, the housing 106 shown in FIG. 1 also includes an opening 106H to which the lens 112 is attached, similar to the housing 106 shown in FIG. However, in the case of the inspection apparatus 100, since there is no reflection mirror 114, the image sensor 111 is arranged on an extension of the opening 106H. Therefore, there is a possibility that the image sensor 111 is irradiated with radiation that has entered through the opening 106H.

<Modification 2>
FIG. 12 is a cross-sectional view of a main part schematically showing a configuration example of an inspection device that is another modification of FIG. 1. In FIG. 13 is an explanatory diagram schematically showing the path of light emitted from the illumination section for reflected light shown in FIG. 12, and FIG. 14 is an explanatory diagram schematically showing the path of light emitted from the illumination section for diffused light shown in FIG. FIG. In this modification, an embodiment will be described in which the optical axis 113 of the camera 110 is inclined with respect to the normal direction of the test surface 102.

The inspection apparatus 100B shown in FIG. 12 is different from the inspection apparatus 100 shown in FIG. 1 and the inspection apparatus 100A shown in FIG. It differs from In addition, the inspection apparatus 100B has a virtual image 254 of the light source (diffusion plate 253 regarded as a light source) of the reflected light illumination unit 250 with the surface to be inspected 102 as a virtual mirror surface on the extension line of the optical axis 113 of the camera 110. The present invention differs from the inspection apparatus 100 shown in FIG. 1 and the inspection apparatus 100A shown in FIG. 11 in this respect. In this way, the virtual image 254 of the diffuser plate 253, which is regarded as the light source of the reflected light illumination section 250, which is bright field illumination, is arranged on the extension of the optical axis 113, so that the optical axis 113 and the surface to be inspected 102 are connected. The vicinity of the point where the two intersect can be observed with high precision, just like other areas.

Specifically, the reflected light illumination unit 250 of the inspection device 100B includes an LED array 251, a cylindrical lens 252, and a diffuser plate 253. The LED array 251 is a light source that generates light, and is a semiconductor component in which a plurality of LED (Light Emitting Diode) elements are arranged. The plurality of LED elements are arranged in a direction perpendicular to the paper surface of FIG. The cylindrical lens 252 is an optical element that converts the light received from the LED array 251 into a sheet beam. The cylindrical lens 252 has a longitudinal direction perpendicular to the plane of the paper in FIG. 12, and can convert the light received from the LED array 251 into a sheet beam parallel to the direction in the plane of the paper. The diffuser plate 253 is a surface light source that receives the sheet beam emitted from the cylindrical lens 252 and irradiates a wide range of light. Since the surface to be inspected 102 is irradiated with light from the diffuser plate 253, the light source of the reflected light illumination unit 250 for inspecting the surface to be inspected 102 can be regarded as the diffuser plate 253. .

As shown in FIG. 13, the light emitted from the LED array 251 is irradiated onto the diffuser plate 253 via the cylindrical lens 252, and the light emitted from the diffuser plate 253 is irradiated onto the surface to be detected 102. At least a portion of the light specularly reflected by the test surface 102 is received by the image sensor 111 via the lens 112 and the reflecting mirror 114. Note that a phase plate 115 for WFC (Wave Front Coding), which will be described later, is arranged between the lens 112 and the reflection mirror 114. Similarly to the case of the inspection apparatus 100 shown in FIG. within the field of view 105 (see FIG. 12). Therefore, at least a portion of the light specularly reflected by the test surface 102 is received by the lens 112.

Further, the diffused light illumination section 260 includes an LED array 261 and a cylindrical lens 262. The plurality of LED elements included in the LED array 261 are arranged in a direction perpendicular to the paper surface of FIG. The cylindrical lens 262 is an optical element that converts the light received from the LED array 261 into a sheet beam. The cylindrical lens 262 has a longitudinal direction perpendicular to the plane of the paper in FIG. 12, and can convert the light received from the LED array 261 into a sheet beam parallel to the direction in the plane of the paper. In the case of diffused light, which is dark-field illumination, the surface to be inspected 102 is irradiated with light emitted from the cylindrical lens 262, as shown in FIG. Therefore, the cylindrical lens 262 can be regarded as a light source of the diffused light illumination section 260. Similarly to the case of the inspection apparatus 100 shown in FIG. does not exist within the viewing range 105 (see FIG. 12), but is outside the viewing range 105. Therefore, regarding the light emitted from the diffused light illumination section 260, the light that is specularly reflected by the test surface 102 is not received by the lens 112, and part of the light diffused by the test surface 102 is reflected by the lens 112. The light is received by the image sensor 111 via the lens 112 and the reflecting mirror 114 .

As described above, in the case of this modification, the optical axis 113 of the camera 110 is arranged so as to be inclined with respect to the normal direction of the test surface 102, so that the virtual image 254 of the diffuser plate 253 is It becomes possible to arrange it on the extension line of 113. As a result, the central region near the point where the optical axis 113 of the camera 110 and the surface to be inspected 102 intersect can be observed with high precision. However, in the case of this modification, since the optical axis 113 is inclined with respect to the normal direction of the test surface 102, a problem arises in that the range in which the test surface 102 can be focused becomes narrow. . Although it is not impossible to focus even if the focusing range becomes narrower, it is preferable to apply an imaging system technology called WFC, which will be described below.

In an imaging system using WFC, the blurring of point images due to defocus is made uniform by giving a phase distribution given by a cubic function to the coordinates in the pupil plane, and the uniform blurring is achieved by image processing called deconvolution. The depth of field and depth of focus of the optical system are expanded. In order to apply this technique, the inspection apparatus 100B of this modification includes a phase plate 115 disposed between the lens 112 and the reflection mirror 114. The phase plate 115 is arranged at the aperture position of the imaging optical system. Note that the phase plate 115 may be located near the diaphragm position. The phase plate 115 is a phase filter having a surface expressed by a cubic function. In the example shown in FIG. 12, the phase plate 115 has a shape in which a plurality of concave surfaces are arranged concentrically around the optical axis 113. The phase plate 115 has a shape that is rotationally symmetrical about the optical axis 113. Each of the plurality of concave surfaces has a parabolic cross-sectional shape. A structure in which a plurality of concave surfaces having a parabolic cross-sectional shape are arranged in this way is called an annular structure. A portion corresponding to one of the plurality of concave surfaces is called an annular zone.

Although FIG. 12 illustrates the phase plate 115 having an annular structure as described above, there are various modifications of the phase plate 115 that can be applied to WFC. Any structure other than the annular structure may be used as long as it is a curved surface that can be expressed by a cubic function. Alternatively, any structure other than the annular structure may be used as long as it is a curved surface that causes spherical aberration.

When the light reflected or diffused by the test surface 102 is received by the image sensor 111 via the phase plate 115, the image on the image sensor 111 becomes blurred. In other words, the image data output by the image sensor 111 is a defocused optical image. However, the phase plate 115 is designed so that the blurring of the image on the image sensor 111 is insensitive to defocus. By designing the phase plate 115 so as to be insensitive to defocusing, it is possible to solve the above-mentioned problem that the focusing range becomes narrow. That is, by interposing the phase plate 115 in the path of light within the camera 110, the blurring of the image in the image sensor 111 becomes uniform regardless of the degree of defocus. In this case, by executing deconvolution processing, which will be described later, it is possible to obtain an image without blur (with less blur to the extent that the crack 104 shown in FIG. 8 can be identified).

The image processing circuit 122 shown in FIG. 12 performs deconvolution processing on the image data (blurred image data) received from the image sensor 111 to obtain a focused image from a blurred optical image. The deconvolution process is an arithmetic process that calculates a geometric mapping (ideal optical image) of the light intensity distribution on the object plane on the image plane from the spatial frequency spectrum (optical transfer function OTF) of the point spread distribution. Although the details are omitted, deconvolution processing and WFC processing using the same are described in detail as deconvolution image processing in the patent document (Japanese Patent Laid-Open Publication No. 2014-197115) by the inventors of the present application. There is. Image processing circuit 122 performs deconvolution image processing described in this patent document.

After the deconvolution process is completed, the image processing circuit 122 outputs the image data after the deconvolution process (image data from which blur has been removed) to the display device 123. As a result, the display device 123 displays an image with the blur removed, so that the crack 104 shown in FIG. 8 can be detected based on this image. The inspection apparatus 100B is the same as the inspection apparatus 100 shown in FIG. 1 except for the above-mentioned differences. Therefore, duplicate explanations will be omitted. Note that although not shown in the drawings, the brightness of each of the reflected light illumination section 250 and the diffused light illumination section 260 can be controlled independently from each other by the brightness control section 230 shown in FIG. This is similar to the inspection device 100 shown in FIG.

Although various modified examples have been described above, each modified example can be appropriately combined and applied.

Although typical modifications of the present embodiment have been described above, the present invention is not limited to the above-described embodiments and typical modifications, and various modifications can be made without departing from the spirit of the invention. Applicable.

INDUSTRIAL APPLICATION This invention can be utilized for a lighting device and an inspection device using the same.

100, 100A, 100B Inspection device 101 Reactor (container)
102 Test surface (inspection target surface)
104 Crack 104W Width 104D Depth 105 Viewing range 106 Housing 106H Opening 110 Camera 111 Image sensor 112 Lens (imaging lens)
113 Optical axis 114 Reflection mirror 115 Phase plate 120 Transmission circuit 121 Cable 122 Image processing circuit 123 Display device 125 Computer 126 Judgment processing section 131, 132 Region 200 Illumination device (illumination section)
210, 250 Reflected light illumination section (bright field illumination, bright field illumination section)
211, 221, 254, 264 Virtual image 212, 222 Cable 213, 223 Light 220, 260 Illumination unit for diffused light (dark field illumination, dark field illumination unit)
230 Brightness control unit (light amount control unit)
240A, 240B, 240C Image 251, 261 LED array 252, 262 Cylindrical lens 253 Diffusion plate S11, S12, S13, S14, S15 Step VL1 Extension line

Claims (4)

A camera that images the surface to be inspected;
a reflected light illumination unit that irradiates light reflected by the test surface and incident on the camera;
a diffused light illumination unit that irradiates light that is diffused on the test surface and enters the camera;
an image processing circuit that processes image data captured by the camera;
has
A virtual image of the light source of the reflected light illumination unit with the test surface as a virtual mirror surface is within the field of view of the camera,
A virtual image of the light source of the diffused light illumination unit that makes the test surface a virtual mirror surface is not within the viewing range of the camera,
The optical axis of the camera is inclined with respect to the normal direction of the test surface,
A virtual image of the light source of the reflected light illumination unit with the test surface as a virtual mirror surface is on an extension of the optical axis of the camera,
The camera is
an imaging lens;
an image sensor that receives light through the imaging lens;
Equipped with
A reflecting mirror is disposed in a light path between the imaging lens and the image sensor,
A phase plate is arranged between the reflecting mirror and the imaging lens,
The image data output by the image sensor is a defocused optical image,
The image processing circuit performs a deconvolution process on the image data received from the image sensor to obtain a focused image from the blurred optical image, and outputs the image data after the deconvolution process. Inspection equipment. The inspection device according to claim 1 ,
An inspection device further comprising a brightness control unit that controls each of the brightness of the light emitted from the reflected light illumination unit and the brightness of the light emitted from the diffused light illumination unit. The inspection device according to claim 2 ,
Based on image data captured by the camera, whether or not it is necessary to change the brightness of at least one of the brightness of the light emitted from the reflected light illumination section and the brightness of the light emitted from the diffused light illumination section. further comprising a determination processing unit that determines
The determination processing unit is an inspection device that outputs the determination processing data regarding the necessity of the change to the brightness control unit. In the inspection device according to claim 3 ,
The image sensor and the reflection mirror are housed in a metal housing,
The housing is formed with an opening for attaching the imaging lens,
The image sensor is an inspection device arranged at a position away from an extension of an imaginary line linearly connecting the opening and the reflecting mirror.

Images