JP2023106244A - Visual inspection device - Google Patents

Abstract

To conduct the visual inspection of a test object having a convex mirror surface easily with good accuracy.SOLUTION: A visual inspection device 1 comprises: a base 10 which is configured so that a test object 90 having a convex mirror plane 91 is located on a reference axis 80; a lighting device 20 which is configured so that illumination light including a changeable prescribed pattern is radiated in a direction along the reference axis 80; a perimeter mirror 30 which is configured so that a reflection plane 32 tilted with respect to the reference axis 80 is disposed so as to enclose a space around the reference axis 80, and illumination light radiated from the lighting device 20 and passing through a periphery of the test object 90 is reflected by the reflection plane 32 toward the convex mirror plane 91; an imaging device 40 which is configured to image a direction of the convex mirror plane 91 via the space around the reference axis 80 of the perimeter mirror 30; and an information processing device 50 for conducting analysis regarding a surface of the convex mirror plane 91 on the basis of a pattern of reflection by the convex mirror plane 91, of illumination light including the pattern that is included in the image obtained by the imaging device 40.SELECTED DRAWING: Figure 1

Description

The present invention relates to a visual inspection apparatus.

As a method of visual inspection of an object to be inspected, the object to be inspected is photographed with an imaging device and the obtained image is subjected to predetermined image processing to determine the presence or absence of defects such as scratches on the surface of the object to be inspected. is known. In this method, if the object to be inspected has a defect, the light applied to the object to be inspected at the defective portion is diffusely reflected. Defects can be identified by detecting such changes in image processing. On the other hand, if the object to be inspected has a mirror surface, the environment other than the illumination light may be reflected on the object to be inspected, or the reflected light of the irradiated light may be strong and the diffuse reflection of the defect part may be canceled by the reflected light. Therefore, it is generally difficult to detect defects by the same method.

As an appearance inspection method for an object to be inspected having a mirror surface, a method of projecting a striped light and dark pattern onto the mirror surface and obtaining an image thereof is known, as disclosed in Patent Document 1, for example. . In this method, if there is a defect such as a scratch, the striped light-and-dark pattern is distorted at that portion, so it is easy to detect the defective portion based on the image. It is known that when using such a method, it is necessary to appropriately set the pattern projection method, the imaging method, and the like according to the shape of the object to be inspected.

JP 2017-15647 A

SUMMARY OF THE INVENTION It is an object of the present invention to easily and accurately inspect the appearance of an object having a convex curved mirror surface.

According to one aspect of the present invention, an appearance inspection apparatus includes a base on which an object to be inspected having a convex curved mirror surface on a reference axis is arranged, and a base on the side opposite to the convex side of the convex curved mirror surface. a lighting device disposed and including an electronic display and configured to emit illumination light including a changeable predetermined pattern in a direction along the reference axis; and a side opposite the lighting device with respect to the base. and a reflecting surface inclined with respect to the reference axis is provided so as to surround a space around the reference axis to reflect the illumination light emitted from the illumination device and passing around the object to be inspected. an omnidirectional mirror configured to reflect light toward the convex curved mirror surface on its surface; an imaging device configured to capture an image in the direction of the convex curved mirror surface through an imaging device; and based on the pattern of reflection by the convex curved mirror surface of the illumination light including the pattern included in the image obtained by the imaging device and an information processing device for analyzing the surface of the convex curved mirror surface.

ADVANTAGE OF THE INVENTION According to this invention, the appearance inspection of the to-be-inspected object which has a convex curved mirror surface can be performed easily and accurately.

FIG. 1 is a diagram schematically showing an outline of a configuration example of a visual inspection apparatus according to one embodiment. FIG. 2 is a diagram showing the shape of an object to be inspected used in the example. FIG. 3 is a diagram showing an example of a light-dark pattern presented on the liquid crystal panel in the embodiment. FIG. 4 is an example of an image captured by an imaging device in the example. FIG. 5 is an example of an output image when the image shown in FIG. 4 is input to the trained model.

An embodiment of a visual inspection apparatus will be described with reference to the drawings. The appearance inspection apparatus of this embodiment is an apparatus for inspecting an object having a convex curved mirror surface, and in particular, an apparatus for inspecting whether or not the convex curved mirror surface has defects such as dents. Convex curved surfaces may include various outwardly convex curved surfaces. The convex curved surface may be, for example, a curved surface including a part of the outer surface of a sphere, an ellipsoid, or the like.

[Configuration of Appearance Inspection Device]
FIG. 1 schematically shows an outline of a configuration example of a visual inspection apparatus 1 according to this embodiment. As shown in FIG. 1 , the visual inspection apparatus 1 includes a base 10 , an illumination device 20 , an all-around mirror 30 , an imaging device 40 and an information processing device 50 . FIG. 1 shows, as an object to be inspected, an object 90 to be inspected in which a hemispherical convex curved mirror surface 91 is provided on the top of a cylindrical body.

The base 10 is a structure on which an object 90 to be inspected is arranged. In this example, the mounting surface 12 of the base 10 is provided horizontally. A reference axis 80 is provided vertically in the center of the base 10 . In this example, the visual inspection apparatus 1 is configured such that an object 90 to be inspected is mounted on the mounting surface 12 of the base 10 such that the central axis of the cylindrical body of the object 90 coincides with the reference axis 80 . ing. A transparent portion 14 is provided in the central portion of the base 10 for transmitting illumination light, which will be described later. The transparent portion 14 is made of, for example, a glass plate. As for the base 10, only the central transparent portion 14 may be formed of, for example, a glass plate, or the entire base 10 may be formed of a glass plate.

The configuration of the base 10 shown here is just an example, and the base may have other configurations as long as the base is configured so that the inspected object 90 having the convex curved mirror surface 91 on the reference axis 80 is arranged. You may have For example, the base may have a jig for fixing the object 90 to be inspected. When the base supports the object 90 to be inspected so that the central axis of the cylindrical body of the object 90 is horizontal, the reference axis 80 is horizontal, and the other parts described below are arranged accordingly. will be changed. The base may have any configuration as long as it is configured such that illumination light, which will be described later, can pass around the object 90 to be inspected.

The lighting device 20 is arranged below the base 10 . That is, the illumination device 20 is arranged on the opposite side of the convex curved mirror surface 91 to the convex side. The illumination device 20 has a liquid crystal panel 22 and a backlight 24 . The liquid crystal panel 22 is provided on the base 10 side of the backlight 24 . The liquid crystal panel 22 has a large number of pixels, and is configured such that each pixel can be switched between a state in which at least light is substantially transmitted and a state in which light is not transmitted. The light emitted from the backlight 24 passes through the liquid crystal panel 22 and is irradiated in the direction of the base 10 . The illumination device 20 is arranged such that the projection optical axis of the illumination device 20 coincides with the reference axis 80 . This illumination light is applied to a sufficiently wide area so as to pass around the object 90 to be inspected.

Since the liquid crystal panel 22 presents a pattern, the illumination light emitted from the backlight 24 and transmitted through the liquid crystal panel 22 becomes illumination light having a pattern including bright portions and dark portions. This pattern is, for example, a striped pattern in which bright portions and dark portions are alternately repeated. This pattern may be, for example, a pattern in which bright portions and dark portions radially extending around the reference axis 80 are alternately repeated in the circumferential direction. Also, this pattern may be, for example, a pattern in which concentric bright portions and dark portions are alternately repeated in the radial direction around the reference axis 80 . A plurality of patterns having different widths and numbers of bright portions and dark portions may be prepared.

The configuration of the illumination device 20 shown here is an example, and the illumination device may include various types of electronic displays such that illumination light containing a predetermined changeable pattern is emitted such that it travels along the reference axis 80. may have other configurations. For example, lighting device 20 may include an electronic display such as an organic EL display. Here, "along the reference axis 80" means that the irradiation direction of the illumination light is the direction along the reference axis 80, and the illumination light does not need to be parallel light, and the optical axes need to match. Nor.

The omnidirectional mirror 30 is provided on the side of the base 10 opposite to the illumination device 20 , that is, above the base 10 . The all-around mirror 30 has a reflective surface 32 in the shape of the inner surface of a truncated cone. The omnidirectional mirror 30 has a shape in which the upper and lower bottom surfaces of this truncated cone are open. Here, the omnidirectional mirror 30 is provided with the lower bottom surface of the truncated cone directed toward the base 10 so that the central axis of the truncated cone coincides with the reference axis 80 . That is, the reflecting surface 32 is inclined with respect to the reference axis 80 and provided so as to surround the space around the reference axis 80 . The reflecting surface 32 is provided so as to surround the convex curved mirror surface 91 of the inspected object 90 . The omnidirectional mirror 30 is illuminated by the illumination device 20 , passes through the transparent portion 14 of the base 10 , and passes around the object 90 to be inspected. It is configured to reflect towards 91 .

The imaging device 40 includes a photographing lens and an image area sensor. The imaging device 40 is arranged above the omnidirectional mirror 30 , that is, on the opposite side of the omnidirectional mirror 30 from the base 10 . The imaging device 40 captures the convex curved surface of the inspection object 90 via the upper and lower bottom surfaces of the open truncated cone of the all-around mirror 30 , that is, through the space around the reference axis 80 inside the all-around mirror 30 . It is configured to photograph the mirror surface 91 side. Particularly when the convex curved mirror surface 91 of the object to be inspected 90 is symmetrical with respect to the reference axis 80 , the imaging device 40 is preferably arranged so that its photographing optical axis is aligned with the reference axis 80 . The imaging device 40 is configured to transmit image information obtained by photography to the information processing device 50 .

The information processing device 50 includes a computer having various integrated circuits. The information processing device 50 operates according to a program recorded in a recording device or the like. The information processing device 50 controls the operation of the lighting device 20 . The information processing device 50 records a plurality of patterns of illumination light emitted from the lighting device 20 described above, that is, information of a plurality of patterns presented by the liquid crystal panel 22 . The information processing device 50 controls the operation of the illumination device 20 using the recorded pattern information. The information processing device 50 controls presentation of patterns by the liquid crystal panel 22 . The information processing device 50 also controls the amount of light emitted from the backlight 24 and the like. The information processing device 50 also controls the operation of the imaging device 40 . The information processing device 50 controls shooting conditions such as exposure and focal length of the imaging device 40, shooting timing, and the like.

The information processing device 50 also analyzes the inspection object 90 based on the image information acquired from the imaging device 40 . In particular, the information processing device 50 analyzes the surface of the convex mirror surface 91 based on the reflection pattern of the illumination light including the pattern included in the image obtained by the imaging device 40 from the convex curved mirror surface 91 . The information processing device 50 includes, for example, a program for analysis such as determining whether the object to be inspected 90 is good or bad and detecting defective portions. Artificial intelligence may be used for this analysis. For example, the information processing apparatus 50 may have a trained model that is constructed in advance by machine learning using a technique such as the error backpropagation method and using, for example, non-defective images as teacher data. Using this learned model, the information processing device 50 can determine whether the object to be inspected 90 is good or defective, that is, whether or not there is a defect, based on the image information acquired from the imaging device 40. .

[Operation of Appearance Inspection Device]
The operation of the appearance inspection apparatus 1 will be described. The information processing device 50 controls the operation of the lighting device 20 to cause the lighting device 20 to emit illumination light. More specifically, under the control of the information processing device 50, the liquid crystal panel 22 presents, for example, a pattern in which bright portions and dark portions are alternately repeated. The backlight 24 emits light toward the liquid crystal panel 22 under the control of the information processing device 50 . Light emitted from the backlight 24 passes through the liquid crystal panel 22 and becomes illumination light including the pattern presented by the liquid crystal panel 22 . This illumination light passes through the transparent portion 14 of the base 10 , passes around the object 90 to be inspected, and reaches the reflecting surface 32 of the full-circumference mirror 30 . The reflecting surface 32 reflects this illumination light toward the convex curved mirror surface 91 of the object 90 to be inspected. As a result, the pattern presented on the liquid crystal panel 22 is projected onto the convex curved mirror surface 91 of the object to be inspected 90, which is the projection surface.

Under the control of the information processing device 50, the imaging device 40 captures an image of the inspected object 90 on which the pattern is projected, especially the convex curved mirror surface 91 portion. The imaging device 40 transmits image information obtained by shooting to the information processing device 50 . The information processing device 50 determines whether or not there is a defect on the convex curved mirror surface 91 of the inspection object 90 based on the image information acquired from the imaging device 40 .

Incidentally, in the inspection of one object 90 to be inspected, analysis may be performed based on one image obtained by one shot, or analysis may be performed based on a plurality of images. That is, a plurality of patterns may be projected onto the object 90 to be inspected, a plurality of images may be acquired, and analysis may be performed based on these plurality of images. For example, while the finer the lines of the bright and dark stripe pattern (the narrower the spacing), the higher the resolution, the line width of the projected pattern that is easily detected may differ depending on the size of the scratch or the like. Therefore, analysis may be performed using a plurality of patterns with different line widths. In addition, when there is a flaw or the like that crosses a bright portion and a dark portion, the flaw or the like is likely to be detected, for example, if the flaw or the like is contained in the bright or dark portion, the flaw or the like may not be detected. There is Therefore, by moving the pattern of light and dark, it becomes possible to detect such flaws. In addition, by changing the pattern, such as a radial striped pattern and a concentric striped pattern, it becomes possible to detect such a flaw or the like.

[Example]
An embodiment of the appearance inspection apparatus 1 will be described. FIG. 2 is a diagram showing the shape of an inspection object 90 used in this embodiment. This inspected object 90 has a shape in which a convex curved mirror surface 91 is provided on a cylindrical portion 92 . A top portion 93 of the convex curved mirror surface 91 is horizontally cut, and a hole 94 is provided in the central portion along the central axis. Such an object 90 to be inspected was mounted on the mounting surface 12 of the base 10 of the visual inspection apparatus 1 so that its central axis coincided with the reference axis 80 .

FIG. 3 shows a light-dark pattern presented on the liquid crystal panel 22 . As shown in this figure, this embodiment uses a pattern in which bright portions and dark portions radially extending around a reference axis 80 are alternately repeated in the circumferential direction.

FIG. 4 is an example of an image captured by the imaging device 40 . A pattern in which bright portions and dark portions are alternately repeated in the circumferential direction is projected on the periphery of the convex curved mirror surface 91 of the object 90 to be inspected. A reflection pattern of this pattern can be seen in the resulting image.

A trained model was generated by machine learning using the error backpropagation method and using images of good products as training data. In the information processing device 50, an image acquired by the imaging device 40 is input to this trained model. FIG. 5 is an example of an output image when the image shown in FIG. 4 is input to the trained model. From FIG. 5, it was found that the white portion 82 had a defect. It can be seen from FIG. 4 that the bright and dark striped pattern is disturbed in this portion 81 .

As described above, by using the visual inspection apparatus 1 according to the present embodiment, it is possible to detect defects in the convex curved mirror surface 91, and it is clear that it is possible to determine whether the convex curved mirror surface 91 is a non-defective product or a defective product. Became.

[About visual inspection equipment]
In the appearance inspection apparatus 1 of the above-described embodiment, when inspecting the convex curved mirror surface 91, a bright and dark striped pattern is projected. When obtaining an image of a mirror surface by photographing, it is generally difficult to identify the fine surface shape from the image. becomes easier to identify.

Various methods of projecting the pattern onto the device under test 90 are possible. For example, a method of forming a transparent film printed with a striped pattern into a cylindrical shape and arranging it around the object 90 to be inspected and projecting light from the outside can be considered. On the other hand, in the inspection of the convex curved mirror surface 91 targeted by the present embodiment, it was found that projecting the striped pattern from above the object 90 to be inspected produced a clearer pattern.

In addition, when a pattern is printed on a transparent film, the line width is limited according to the printing technology, and in order to project while changing various patterns, it is necessary to prepare a plurality of transparent films and replace them. In other cases, a moving mechanism for physically moving the transparent film is required to move the pattern. For example, if the light-dark pattern is constant, the size, position, etc. of a flaw that can be detected may be limited. Moreover, it may be necessary to prepare different transmissive films depending on the object to be inspected. On the other hand, by forming patterns of illumination light using the liquid crystal panel 22, various patterns can be formed relatively easily, and the patterns can be easily changed and moved, which facilitates inspection. You can also shorten the time.

A self-luminous panel such as an organic EL display may be used for the lighting device 20 . However, it is relatively difficult to obtain sufficient luminance in an organic EL display or the like. On the other hand, by configuring the illumination device 20 with the liquid crystal panel 22 and the backlight 24 as in the present embodiment, it becomes easy to use a high-brightness light source for the backlight 24 . As a result, a sufficient amount of light can be obtained easily. Therefore, using the liquid crystal panel 22 and the backlight 24 is one preferred mode.

Illumination light formed using a flat liquid crystal panel 22 needs to be projected from above onto the convex curved mirror surface 91 of the object 90 to be inspected. It has been found that this can be satisfactorily achieved by arranging an all-around mirror 30 having a reflective surface 32 with a trapezoidal side surface.

In image analysis, it was found that it is possible to detect pattern distortion caused by scratches or the like with high accuracy by using a trained model created by machine learning.

Although the present invention has been described above with reference to preferred embodiments, it goes without saying that the present invention is not limited to the above-described embodiments, and that various modifications can be made within the scope of the present invention. Nor.

Reference Signs List 1 appearance inspection device 10 base 12 mounting surface 14 transparent part 20 lighting device 22 liquid crystal panel 24 backlight 30 all-around mirror 32 reflecting surface 40 imaging device 50 information processing device 80 reference axis 90 object to be inspected 91 convex curved mirror surface

Claims (5)

a base on which an object to be inspected having a convex curved mirror surface is arranged on a reference axis;
an illumination device disposed opposite the convex side of the convex curved mirror surface, including an electronic display, configured to emit illumination light including a predetermined changeable pattern in a direction along the reference axis;
A reflective surface disposed on the opposite side of the base from the illumination device and inclined with respect to the reference axis is provided so as to surround a space around the reference axis, and radiated from the illumination device to the inspected object. an all-around mirror configured to reflect the illumination light that has passed around the body toward the convex curved mirror surface with the reflecting surface;
an imaging device disposed on the side opposite to the base with respect to the omnidirectional mirror and configured to photograph the direction of the convex curved mirror surface through the space around the reference axis of the omnidirectional mirror;
and an information processing device that analyzes the surface of the convex mirror surface based on the reflection pattern of the illumination light including the pattern included in the image obtained by the imaging device from the convex mirror surface. 3. The illumination device has a liquid crystal panel and a backlight, and is configured such that illumination light including the pattern is emitted when light emitted from the backlight passes through the liquid crystal panel. 2. The visual inspection apparatus according to 1. The base has a transparent portion configured to mount the object to be inspected,
The light emitted from the illumination device is configured to pass through the transparent portion and reach the full-circumference mirror.
The visual inspection apparatus according to claim 1 or 2. The pattern includes a pattern in which bright portions and dark portions radially extending around the reference axis are alternately repeated in the circumferential direction, or
The pattern includes a pattern in which concentric bright portions and dark portions are alternately repeated in the radial direction around the reference axis,
The visual inspection apparatus according to any one of claims 1 to 3. 2. The information processing device is configured to determine whether the object to be inspected is a non-defective product or a defective product using a trained model created by error backpropagation using an image of a non-defective product as teaching data. 5. The visual inspection apparatus according to any one of thru|or 4.

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