WO2025004644A1 - Inspection system, method of correcting inclination angle of surface of article using same, and method of enhancing features of image of article - Google Patents

Abstract

The present invention provides an inspection system that can increase the usage efficiency of inspection light and reflected light used for visual inspection of articles. An inspection system (100) comprises an illumination device (50) that irradiates an article (200) with inspection light and a camera (70) that captures an image of the article (200) irradiated with inspection light. The illumination device (50) comprises an area light source (10) that emits inspection light and an objective lens (30) that condenses the inspection light toward the article (200). The inspection light is incident on the objective lens (30) with a predetermined color distribution. The camera (70) is disposed on the light path of reflected light from the article (200) and on the side of the area light source (10) opposite to the objective lens (30). The area light source (10) is disposed at the focal point (P1) on the incident side of the objective lens (30) and transmits reflected light. The optical axis (OAi) of the inspection light and the optical axis (OAr) of the reflected light are coaxial.

Description

Inspection system, and method for correcting inclination angle of surface of article using same, and method for enhancing features of image of article

This disclosure relates to an inspection system used for visual inspection of an object, a method for correcting the inclination angle of the surface of an object using the inspection system, and a method for highlighting features of an image of an object.

　Conventionally, the configurations disclosed in Patent Documents 1 to 3 are known as lighting devices used for visual inspection of objects.

In the conventional configuration disclosed in Patent Document 1, a filter member is placed between the surface light source and the objective lens. This filter member is placed on the opposite side of the objective lens from the object to be inspected, near the focal position of the objective lens on the illumination optical axis. Furthermore, this filter member divides the wavelength range, which is an optical attribute of the inspection light emitted from the surface light source, into multiple solid angle regions.

By configuring the lighting device in this way, inspection light having the same illumination solid angle is irradiated at each point on the surface of the object. This makes it possible to make the lighting conditions the same at each point on the surface of the object. It also makes it possible to observe the object with high resolution and to recognize the inclination angle of the object's surface over a wide range.

In addition, in the conventional configurations disclosed in Patent Documents 2 and 3, a camera that receives reflected light from the object is disposed on the opposite side of the surface light source from the objective lens and the object. The reflected light passes through the surface light source and enters the camera lens.

The configuration disclosed in Patent Document 2 further includes a plurality of sets consisting of first to nth optical members arranged opposite the light emission surface of the surface light source. The first to nth optical members transmit the inspection light emitted from the light emission surface toward the object. The wavelengths and irradiation solid angles of the inspection light emitted from the first to nth optical members toward the object are different from one another. In this way, the reflected light from the object has a wavelength that corresponds to the degree of inclination of the object's surface. The degree of local inclination of the object's surface can be ascertained by checking the image captured by the camera.

In the configuration disclosed in Patent Document 3, furthermore, inspection light is emitted from one portion of the surface light source, and the object is irradiated with the inspection light while the emission position of the inspection light is sequentially scanned in a first direction. Next, the object is irradiated with the inspection light while the emission position of the inspection light is sequentially scanned in a second direction different from the first direction. The control unit identifies the emission position of the inspection light when a measurement point on the surface of the image is illuminated from the image of the object captured during both scans, and calculates the distance to the measurement point based on the identified emission position and the first and second directions.

In this way, the control unit can obtain information regarding the emission position of the inspection light. This emission position does not depend on the relative position between the camera and the surface light source. In other words, it is not necessary to place the surface light source at a specific position relative to the incident optical axis to the camera. Therefore, it is possible to inspect an item without the need for calibration between the camera and the lighting device.

Japanese Patent No. 7206020 JP 2019-138682 A JP 2021-183989 A

However, in the conventional configuration disclosed in Patent Document 1, a half mirror is placed on the optical path of the inspection light to separate the optical paths of the inspection light and the light reflected from the object. When the inspection light is reflected by the half mirror and irradiated onto the object, the amount of inspection light before and after passing through the half mirror is approximately halved. Also, when the light reflected from the object passes through the half mirror and enters the camera, the amount of reflected light before and after passing through the half mirror is approximately halved. In other words, the reflected light actually used for visual inspection of the object is approximately 1/4 of the amount of the original inspection light.

This disclosure has been made in consideration of these points, and its purpose is to provide an inspection system that can improve the efficiency of using inspection light and reflected light used in visual inspection of an object, as well as a method for correcting the inclination angle of the surface of an object using the same, and a method for highlighting features in an image of an object.

In order to achieve the above object, the inspection system according to the present disclosure is an inspection system including an illumination device that irradiates an object with inspection light, and an imaging device that images the object irradiated with the inspection light. The illumination device includes a surface light source that emits the inspection light, and an objective lens that focuses the inspection light emitted from the surface light source toward the object. The inspection light is incident on the objective lens with a predetermined color distribution in a plane intersecting the traveling direction. The imaging device is disposed on the optical path of the reflected light of the inspection light reflected by the object, and on the opposite side of the objective lens across the surface light source. The surface light source is disposed at or near the focal position of the incident side of the objective lens, and is configured to transmit the reflected light at least in the portion where the reflected light toward the imaging device is incident. The optical axis of the inspection light and the optical axis of the reflected light are disposed coaxially.

According to the present disclosure, since a half mirror is not used, the efficiency of use of the inspection light and reflected light used in the visual inspection of an object can be improved. In addition, the number of parts in the inspection system can be reduced, allowing the inspection system to be made more compact.

1 is a schematic configuration diagram of an inspection system according to a first embodiment. 2 is a schematic plan view of a surface light source provided in the inspection system shown in FIG. 1 . 3 is a schematic diagram showing an illumination solid angle of inspection light irradiated onto an article. FIG. FIG. 1 is a diagram showing an example of an article placed on a support table. 1A and 1B are schematic diagrams showing the state of reflected light when the surface of an article is inclined. 10A to 10C are schematic diagrams showing the state of reflected light when the surface of an article has a different inclination. FIG. 1 is a diagram showing an example of wavelength dependence of reflectance of a metal. FIG. 2 is a diagram showing color distribution within a light emission surface of a surface light source. 11 is a diagram showing the rotation angle dependency of light luminance at the outermost periphery of a surface light source. 13 is a schematic diagram of an inspection system when an object is not properly placed on a support table. FIG. 13 is a schematic diagram of an image of an object when the object is not properly placed on the support base. FIG. 11A and 11B are schematic diagrams illustrating a color distribution of an inspection light according to Modification 1. FIG. 4 is a schematic diagram showing a color distribution of red light in the inspection light. FIG. 4 is a schematic diagram showing a color distribution of blue light in the inspection light. 11 is a schematic diagram showing a color distribution within a light emission surface of a surface light source according to Modification 2. FIG. 13 is a schematic diagram showing another color distribution within the light emission surface of the surface light source according to the second modification. FIG. 13 is a schematic diagram showing yet another color distribution within the light emission surface of the surface light source according to the second modification. FIG. FIG. 11 is a schematic configuration diagram of a surface light source according to a second embodiment. 14 is a schematic diagram of a white surface light source included in the surface light source shown in FIG. 13. 14 is a schematic plan view of a color filter included in the surface light source shown in FIG. 13. 13A and 13B are schematic diagrams showing switching of light emitting regions of a surface light source according to a third embodiment. FIG. 11 is a schematic plan view of a surface light source according to a fourth embodiment. FIG. 13 is a plan view schematic diagram of another surface light source according to the fourth embodiment. FIG. 11 is a schematic cross-sectional view of a surface light source according to Modification 3. FIG. 13 is a schematic cross-sectional view of another surface light source according to Modification 3.

Below, an embodiment of the present disclosure will be described with reference to the drawings. Note that the following description of the preferred embodiment is essentially merely exemplary and is not intended to limit the present disclosure, its applications, or its uses.

[Configuration and operation of inspection system]
Fig. 1 is a schematic diagram of an inspection system 100 according to this embodiment, and Fig. 2 is a schematic plan view of a surface light source 10 included in the inspection system 100. In the following description, the optical axis direction of the inspection light is sometimes referred to as the Z direction, the direction perpendicular to the Z axis is sometimes referred to as the X direction, and the directions perpendicular to the X direction and the Z direction are sometimes referred to as the Y direction. Also, a plane or virtual plane that includes the X direction and the Y direction within its surface is sometimes referred to as an XY plane.

In this specification, "orthogonal," "parallel," or "matching (the same)" means orthogonal, parallel, or matching or the same, taking into account the manufacturing tolerances of the components constituting the inspection system 100 and the assembly tolerances between the components, and does not mean that the objects being compared are strictly orthogonal, parallel, or matching or the same.

As shown in FIG. 1, the inspection system 100 includes a lighting device 50, a camera (imaging device) 70, and a support stand 90. The lighting device 50 is disposed inside a housing 40. The inspection system also includes a diaphragm mechanism 60 and a control device 80.

As will be described in detail later, in the inspection system 100, inspection light is irradiated from the lighting device 50 onto the object 200 placed on the support table 90, and the reflected light of the inspection light reflected by the object 200 (hereinafter simply referred to as reflected light) is captured by the camera 70. The appearance of the object 200 is inspected based on the image captured by the camera 70.

The illumination device 50 is composed of a surface light source 10 and an objective lens 30. The surface light source 10 is composed of a red light source 10R, a green light source 10G, a blue light source 10B, and a light diffusion plate 12. The surface light source 10 is also disposed at the focal position of the objective lens 30, in this case, the focal position P1 on the incident side.

As shown in FIG. 2, the red light sources 10R, the green light sources 10G, and the blue light sources 10B are each periodically arranged on the transparent plate 11. Note that the arrangement shown in FIG. 2 is merely an example, and is not particularly limited to this.

The light diffuser 12 diffuses the red light emitted from the red light source 10R, the green light emitted from the green light source 10G, and the blue light emitted from the blue light source 10B within the plane of the light diffuser 12, in this case in a direction parallel to the XY plane. Note that the red light, green light, and blue light each have a predetermined wavelength range. For example, the red light includes a wavelength of 650 nm and has a wavelength range of several tens of nm to 100 nm. The green light includes a wavelength of 500 nm and has a wavelength range of several tens of nm to 100 nm. The blue light includes a wavelength of 450 nm and has a wavelength range of several tens of nm to 100 nm.

In the example shown in FIG. 2, when the red light source 10R, the green light source 10G, and the blue light source 10B are turned on at the same time, the light emitted from these light sources is diffused by the light diffusion plate 12, and the inspection light emitted from the surface light source 10 becomes a white planar light. In the surface light source 10, the positions and areas where the red light source 10R, the green light source 10G, and the blue light source 10B are made to emit light are controlled by the light source control unit 82 of the control device 80. In addition, the light source control unit 82 can also change the luminance ratio of the red light source 10R, the green light source 10G, and the blue light source 10B in the light-emitting area of the surface light source 10. When changing the luminance ratio, the ratio of the number of emitted light sources of the red light source 10R, the green light source 10G, and the blue light source 10B in the light-emitting area may be changed, or the light emission intensity of each of the red light source 10R, the green light source 10G, and the blue light source 10B may be changed.

When the inspection system 100 is actually operated, the luminance ratio between the red light source 10R, the green light source 10G, and the blue light source 10B is changed more finely within the light-emitting area of the surface light source 10. This gives the inspection light a predetermined color distribution within a plane perpendicular to the optical axis OAi of the inspection light, in this case, within a plane parallel to the XY plane. This color distribution will be described later.

Furthermore, the red light source 10R, the green light source 10G, and the blue light source 10B are each arranged on the transparent plate 11 with a predetermined distance between them. Therefore, the reflected light reflected by the object 200 passes through the light diffusion plate 12 of the surface light source 10 and the transparent plate 11, and heads toward the camera 70. Furthermore, as shown in FIG. 1, the components of the inspection system 100 are arranged so that the optical axis OAi of the inspection light and the optical axis OAr of the reflected light coincide with each other. In other words, in the inspection system 100 shown in FIG. 1, the optical axis OAi of the inspection light and the optical axis OAr of the reflected light are arranged coaxially.

In the example shown in FIG. 1, the red light source 10R, the green light source 10G, and the blue light source 10B are each organic EL (Electro Luminescence) light-emitting elements, and the transparent plate 11 is a bendable flexible substrate. However, this is not particularly limited, and the red light source 10R, the green light source 10G, and the blue light source 10B may each be configured as an LED (Light Emitting Diode). In that case, the transparent plate 11 is a glass substrate. Although not shown, wiring that connects the light-emitting elements is formed on the installation surface of the transparent plate 11 on which the organic EL light-emitting elements and LEDs and other light-emitting elements are installed.

Also, as shown in FIG. 2, adjacent light sources within the plane of the transparent plate 11 are arranged at a predetermined distance d. The distance d is the area through which reflected light passes toward the camera 70, and its value is set appropriately according to the amount of light required for the camera 70 to capture an image of the object 200.

The objective lens 30 focuses the inspection light emitted from the surface light source 10 toward the object 200. In addition, the inspection light is given a predetermined illumination solid angle IS (see FIG. 3) by passing through the objective lens 30. This will be described later.

The aperture mechanism 60 is disposed between the camera (imaging device) 70 and the surface light source 10, more specifically, between the imaging element 73 provided on the camera 70 and the surface light source 10. The aperture mechanism 60 restricts the optical path of the reflected light that is reflected by the object 200 and travels toward the camera 70 when the inspection light is reflected. In the example shown in FIG. 1, the operation of the aperture mechanism 60 is controlled by the aperture control unit 83 of the control device 80. However, this is not limited to the above, and the aperture mechanism 60 may be operated manually. The aperture mechanism 60 may also be disposed at the aforementioned focal position P1 or in the vicinity of the focal position P1.

The support base 90 has a flat surface on which the item 200 is placed.

Camera 70 has a lens 72 and an image sensor 73 inside a housing 71. Although not shown, other optical and electrical components are also arranged inside housing 71.

The light reflected by the object 200 passes through the surface light source 10 and the aperture mechanism 60, is collected by the lens 72, and is incident on the imaging surface of the image sensor 73. The image sensor 73 outputs an image signal of the object 200 based on the incident reflected light. In other words, the camera 70 captures an image of the object 200 illuminated with the inspection light. Note that in reality, the image signal output from the image sensor 73 is processed in the signal processing unit of the control device 80 to generate an image of the object 200.

In addition, the images captured by the camera 70 are color images, and the image sensor 73 is a CMOS (Complementary Metal Oxide Semiconductor) image sensor equipped with a color filter.

The camera 70 may also include a processor (not shown) that processes the output signal of the CMOS image sensor to generate an image. In this case, the signal processing unit 81 may be omitted.

The camera 70 may be provided with an aperture mechanism (not shown). In this case, the aperture mechanism 60 can be omitted. Even if the camera 70 is provided with an aperture mechanism, the aperture mechanism is disposed between the image sensor 73 and the surface light source 10.

For ease of explanation, FIG. 1 shows a single lens 72, but in reality, lens 72 is configured as a lens group having multiple lenses. For example, lens 72, which is a lens group, has, in order of proximity to image sensor 73, an imaging lens, an eyepiece lens, and an objective lens. In this case, objective lens 30 and lens 72, which is a lens group, configure an object-side telecentric optical system for reflected light. In addition, if an aperture mechanism is provided in camera 70, the aperture mechanism is provided between the eyepiece lens and the objective lens.

The control device 80 has multiple functional blocks, including a signal processing unit 81, a light source control unit 82, an aperture control unit 83, a calculation unit 84, a memory unit 85, an input unit 86, and a display unit 87.

The signal processing unit 81 is composed of one or more signal processing LSIs (Large Scale Integrated Circuits) including a GPU (Graphics processing Unit) and performs signal processing of the image signal output from the imaging element 73 as described above, and generates an image of the object 200 illuminated with the inspection light.

The aperture control unit 83 is composed of one or more LSIs and one or more driving ICs (Integrated Circuits), and controls the operation of the aperture mechanism 60 as described above.

The light source control unit 82 is composed of one or more central processing units (CPUs) and one or more driver ICs, and as described above, controls the light emission operation of each of the red light source 10R, green light source 10G, and blue light source 10B.

The calculation unit 84 is composed of one or more CPUs, and performs calculations related to highlighting the features of the image of the item 200, which will be described later. It also performs calculations to correct the inclination angle of the item 200. These calculations are performed based on the results of signal processing in the signal processing unit 81.

The memory unit 85 is composed of one or more semiconductor memories, such as a RAM (Random Access Memory) or a ROM (Read Only Memory). The memory unit 85 may be composed of a HDD (Hard Disk Drive) or an SSD (Solid State Drive). The memory unit 85 stores an inspection program for performing a visual inspection of the item 200, a program related to the arithmetic processing executed by the arithmetic unit 84, and the results after the arithmetic processing. The memory unit 85 also stores an image of the item 200 that has been signal-processed by the signal processing unit 81. The inspection program is also configured to be able to set multiple color distribution patterns when performing an appearance inspection. According to this color distribution pattern, the light source control unit 82 controls the light emission operation of each of the red light source 10R, green light source 10G, and blue light source 10B in the surface light source 10.

The input unit 86 is composed of input devices such as a keyboard or a touch panel. By operating the input unit 86, images stored in the memory unit 85 are called up. In addition, the type of item 200 to be inspected is input, and the corresponding inspection program is called up. In addition, images of the item 200 after visual inspection are called up.

In addition, by operating the input unit 86, parameters required for highlighting features of the image of the item 200 and correcting the tilt angle described above may be input.

The display unit 87 is composed of a display device such as a liquid crystal display or an organic EL display. The display unit 87 displays an image of the item 200 after visual inspection, an input screen for the inspection program, etc.

In the example shown in FIG. 1, the signal processing unit 81 to the display unit 87 are integrated, but this is not particularly limited. For example, the aperture control unit 83 and the light source control unit 82 may be provided independently of the signal processing unit 81 and the calculation unit 84, or each functional block may be provided independently. Furthermore, the calculation unit 84 to the display unit 87 may be configured in a single PC (Personal Computer). It is sufficient that the control device 80 is constructed so that the necessary signals can be sent and received between multiple functional blocks.

[Operation of the inspection system]
Fig. 3 is a schematic diagram showing the irradiation solid angle of the inspection light irradiated on the object. Fig. 4 is an example showing the object 200 placed on a support table. Fig. 5A is a schematic diagram showing the state of reflected light when the surface of the object 200 is inclined, and Fig. 5B is a schematic diagram showing the state of reflected light when the surface of the object 200 is inclined in another way.

First, we will explain the operating principle of the inspection system 100.

When the surface light source 10 and objective lens 30 are arranged as shown in Figure 1, the illumination solid angle IS at point P2, which is on the optical axis OAi of the inspection light and is the output focal position of the objective lens 30, is uniquely determined by the diameter of the optical path of the inspection light in the surface light source 10 and the focal length f of the objective lens 30. Note that the "illumination solid angle" referred to here refers to a cone of any shape that has a vertex at a specific point on the optical path of the inspection light and indicates the range over which light is irradiated to the specific point (see Figure 3, for example). If the diameter of the aforementioned optical path is r1, the planar half angle θ1 of the illumination solid angle IS satisfies the relationship shown in formula (1).

θ1=tan-1(r1/2f)...(1)
In addition, even if the position is far from the optical axis OAi of the inspection light, the illumination solid angle IS at a position that is the same distance from the center of the objective lens 30 as the exit focal position of the objective lens 30 is also the illumination solid angle IS at point P2. The illumination solid angle IS at a position farther than the exit focal position of the objective lens 30 also has the same shape and size as the illumination solid angle IS at point P2.

Therefore, as shown in FIG. 3, the inspection light is irradiated so as to have the same illumination solid angle IS at each point on the surface of the article 200. In other words, the illumination conditions are the same at any point on the surface of the article 200, regardless of the distance from the surface light source 10.

Next, we will explain how to actually perform a visual inspection of item 200.

When the surface of the object 200 is flat and parallel to the surface of the support table 90, as shown in FIG. 1, the optical axis OAi of the inspection light is parallel to the normal to the surface of the object 200. When the inspection light emitted from the surface light source 10 is white light, the reflected light reflected by the surface of the object 200 is also white light. For example, the reflected light from area S1 on the surface of the object 200 shown in FIG. 4 is incident on the camera 70 as white light.

On the other hand, as mentioned above, the inspection light has a color distribution in a plane perpendicular to the optical axis OAi of the inspection light. As a result, in the example shown in FIG. 1, the optical axis of the inspection light emitted from red light source 10R differs in direction from the optical axis of the inspection light emitted from blue light source 10B. Also, as mentioned above, the illumination solid angle IS is the same at each point on the surface of article 200. Therefore, if the surface of article 200 is inclined, the color of the reflected light changes in response to the difference in the direction of the optical axis of the inspection light.

As shown in FIG. 5A, when the surface of the object 200 is tilted to the left of the page, the inspection light emitted from the blue light source 10B is reflected toward the imaging surface of the camera 70. Meanwhile, part of the inspection light emitted from the red light source 10R is reflected away from the imaging surface of the camera 70. As a result, the image of the object 200 captured by the camera 70 has a bluish color. For example, the area S2 on the surface of the object 200 shown in FIG. 4 is captured by the camera 70 as a bluish area.

Also, as shown in FIG. 5B, when the surface of the article 200 is tilted to the right of the page, the inspection light emitted from the red light source 10R is reflected toward the imaging surface of the camera 70. Meanwhile, part of the inspection light emitted from the blue light source 10B is reflected away from the imaging surface of the camera 70. As a result, the image of the article 200 captured by the camera 70 has a reddish color. For example, the area S3 on the surface of the article 200 shown in FIG. 4 is captured by the camera 70 as a reddish area.

As described above, with the inspection system 100 shown in FIG. 1, by appropriately setting the color distribution of the inspection light emitted from the surface light source 10, the direction (tilt) of the surface of the object 200 can be estimated from the intensities of each color in the image captured by the camera 70, for example, red light, green light, and blue light (hereinafter, these may be collectively referred to as RGB). In other words, when the surface of the object 200 is composed of multiple surfaces whose mutual orientations can be determined, the orientation of each surface can be estimated. This can be used to perform an appearance inspection of the object 200. For example, it is possible to inspect the surface unevenness and the presence or absence of scratches on the object 200, which are difficult to identify by irradiating it with white light alone.

[Setting color distribution for surface light sources]
Fig. 6 is a diagram showing an example of wavelength dependency of metal reflectance, Fig. 7 is a diagram showing color distribution in the light emission surface of a surface light source, and Fig. 8 is a diagram showing rotation angle dependency of light luminance at the outermost periphery of a surface light source.

When estimating the surface direction of the object 200 described above, it is necessary that the color balance in the captured image of the object 200 is appropriately adjusted. In general, a white object 200 is captured for each lighting environment, and the RGB intensities are adjusted.

Furthermore, when the material of the object 200 is different, the wavelength dependency of the reflectance also differs, as shown in FIG. 6. For example, silver (Ag) has a constant reflectance of about 1 in the visible light range (400 nm to 700 nm). On the other hand, the reflectance of gold (Au) decreases from 1 to about 0.4 when the wavelength is from 650 nm to 500 nm. Furthermore, in the wavelength range of 500 nm or less, the reflectance is approximately constant at about 0.4. When the wavelength is from 650 nm to 400 nm, the reflectance of copper (Cu) decreases from 1 to about 0.5. In view of this, it is necessary to adjust the color balance even when the material of the object 200 to be inspected is different.

However, in the inspection system 100 shown in FIG. 1, the inspection light irradiated onto the object 200 has a different color for each irradiation direction onto the object 200, corresponding to the color distribution of the inspection light. Therefore, if the surface of the object 200 has multiple faces with different directions (inclinations), the reflected light from the object 200 will also have a different color for each face.

In such a case, the color balance in the image of the item 200 can be appropriately adjusted by setting the color distribution of the inspection light as shown below.

The following describes the method for setting the color distribution of the inspection light in this embodiment.

Specifically, as shown in FIG. 7, the color distribution on the light emission surface of the surface light source 10 is changed continuously or stepwise in a clockwise direction around the center O of the surface light source 10. The color distribution is also imparted so that the saturation of the inspection light decreases continuously or stepwise from the outer periphery toward the center O. In other words, the color distribution is imparted so that the saturation of the inspection light changes continuously or stepwise with respect to the distance r from the center O. For ease of explanation, FIG. 7 illustrates a red region RA that mainly emits red light, a green region GA that mainly emits green light, and a blue region BA that mainly emits blue light.

On the other hand, the inspection light emitted from different positions on the light emission surface satisfies the relationship shown in formula (2).

IR+αIG+βIB=S...(2)
Here, IR, IG, and IB are the luminances of red light, green light, and blue light, respectively. Also, α and β are coefficients greater than zero. In the example shown in this embodiment, α= β=1, and S is a constant.

In other words, the inspection light is set so that the sum of the brightness of the red light, green light, and blue light is constant regardless of the position on the light emission surface.

The inspection light is also set so that the ratio of the brightness of the red light, green light, and blue light changes when the angle θ rotated clockwise from a predetermined position around the center O (the angle θ of rotation along the outer periphery of the surface light source 10) changes.

For example, as shown in Figures 7 and 8, the brightness of the red light, green light, and blue light at the outermost periphery of the surface light source 10 changes according to the rotation angle θ. At the same time, the brightness of each of the red light, green light, and blue light also changes according to the distance r. The smaller the distance r is, that is, the closer to the center O, the lower the saturation of the inspection light. For example, when θ is 120°, the brightness IG of the green light is maximum (=S), while the brightness IR and IB of the red light and blue light are both zero. However, as the distance r becomes smaller and the area closer to the center O becomes larger, the brightness of the red light and blue light each increases above zero.

These are described as the relationships shown in the following equations (3) to (9).

First, the distance r is normalized. The normalized amplitude m of the inspection light at the distance r is set as shown in equation (3).

m=min(R,G,B)...(3)
Here, R, G, and B are the standardized intensities IR, IG, and IB of red light, green light, and blue light, respectively.

At this time, the color distribution of the surface light source 10 is set so that the relationship shown in equation (4) holds between the distance r and the amplitude m.

r=VR/(VR+m)=(S-3m)/(S-2m)...(4)
Here, the fluctuation range VR satisfies the relationship shown in equation (5).

VR=S-3m...(5)
Furthermore, S, r, and m satisfy the relationships shown in expressions (6) to (8).

S≧3m...(6)
0≦r≦1...(7)
0≦m≦1...(8)
Furthermore, from equations (4) and (5), the relationship shown in equation (9) holds for the amplitude m.

m=S×((1-r)/(3-2r))...(9)
In the example shown in FIG. 8, at any position on the light exit surface of the inspection light, the ratio of the luminance of the red light, the luminance of the green light, and the luminance of the blue light is determined according to the distance r and the rotation angle θ. However, as described above, even if the rotation angle θ or the distance r changes, the sum of the luminance of the red light, the green light, and the blue light remains constant.

When providing a color distribution to the inspection light as shown in Figures 7 and 8, the number of light emitted from the red light source 10R, green light source 10G, and blue light source 10B is changed at each position of the surface light source 10. Alternatively, the intensity of the light emitted from the red light source 10R, green light source 10G, and blue light source 10B is changed at each position.

Also, by adding a color distribution to the inspection light as shown in Figures 7 and 8, the inclination of the surface of the object 200 can be quantitatively evaluated. This inclination is expressed as an inclination angle based on the image of the object 200 captured by the camera 70, with the surface of the object 200 being a flat surface that intersects perpendicularly with the optical axis of the inspection light. The inclination angle of the surface of the object 200 (hereinafter sometimes simply referred to as the inclination angle) is calculated by the calculation unit 84 of the control device 80.

[Correction of the inclination angle of the object]
FIG. 9A shows a schematic diagram of an inspection system when an object is not properly placed on a support table, and FIG. 9B shows a schematic diagram of an image of an object when an object is not properly placed on a support table.

If the item 200 is not correctly placed on the support base 90, an offset is added to the inclination angle calculated by the calculation unit 84 of the control device 80, and the correct value may not be obtained. There may also be cases where it is desired to remove the inclination of the item 200 as an offset.

In such cases, the tilt angle can be calculated accurately by removing the offset using the steps below.

As shown in FIG. 9A, when the object 200 is tilted relative to the support table 90, even if the surface of the object 200 is flat or has a certain degree of flatness with some bumps, the image of the object 200 is colored in a color that corresponds to the tilt relative to the support table 90. When an image of the object 200 is captured in the installation state shown in FIG. 9A, the image of the object 200 shown in FIG. 9B has a bluish tint.

Now, a reference point (hereinafter referred to as the reference plane) is set on the surface of the article 200. In the example shown in FIG. 9B, the surface including the cross mark 201 is set as the reference plane. This reference plane is preferably a point that is known in advance to be flat. Also, in order to extract the reference plane from the image of the article 200, it is preferable that the reference plane includes a characteristic shape, as shown in FIG. 9B. It goes without saying that the characteristic shape is not limited to the cross mark 201.

Next, the offset is calculated based on the image of the reference surface, specifically, the color of the image and its brightness intensity, etc.

Furthermore, the offset determined earlier is uniformly subtracted from the inclination angle of each part of the article 200 calculated based on the image of the article 200.

In this way, the offset superimposed on the inclination angle calculated by the calculation unit 84 can be appropriately removed, and the inclination angle of the surface of the object 200 can be accurately determined. Note that the offset described using Figures 9A and 9B corresponds to the inclination of the object 200 relative to the support table 90. Including the inclination of the object 200 itself, the offset in this specification is defined as the inclination of the object 200 relative to the inspection system 100. Note that when the surface of the object 200 has multiple directions, the inclination of the object 200 itself includes the inclination of any location within the object 200, the average of the inclinations of multiple locations within the object 200, etc.

[Effects, etc.]
As described above, the inspection system 100 according to this embodiment includes an illumination device 50 that irradiates inspection light onto the item 200, and a camera (imaging device) 70 that images the item 200 irradiated with the inspection light.

The lighting device 50 includes a surface light source 10 that emits inspection light, and an objective lens 30 that focuses the inspection light emitted from the surface light source 10 toward the object 200.

The inspection light is incident on the objective lens 30 with a predetermined color distribution in a plane that intersects with the direction of travel.

The camera 70 is disposed on the optical path of the inspection light reflected by the object 200, and on the opposite side of the surface light source 10 from the objective lens 30.

The surface light source 10 is arranged at or near the focal position P1 on the incident side of the objective lens 30, and is configured to transmit reflected light. In addition, the optical axis OAi of the inspection light and the optical axis OAr of the reflected light are arranged coaxially.

As mentioned above, in the conventional configuration disclosed in Patent Document 1, the amount of reflected light entering the camera 70 is approximately 1/4 of the amount of the original inspection light.

On the other hand, according to this embodiment, since a half mirror is not used, the efficiency of use of the inspection light and reflected light used in the visual inspection of the item 200 can be significantly improved compared to the conventional configuration disclosed in Patent Document 1. Furthermore, by improving the efficiency of use of the inspection light and reflected light, the exposure time when capturing an image of the item 200 can be shortened. This allows the visual inspection time to be shortened.

In addition, by not using a half mirror, the number of parts in the inspection system 100 can be reduced, and the distance between the optical components in the illumination device 50 can be shortened. This allows the inspection system 100 to be made more compact.

The camera 70 has an image sensor 73 that receives reflected light. In addition, it is preferable that an aperture mechanism 60 that limits the optical path of the reflected light toward the image sensor 73 is provided between the image sensor 73 and the surface light source 10.

If the color image generated by the imaging element 73 is a digital image, the inclination angle can be easily calculated. The signal output from the imaging element 73 is digitized by the signal processing unit 81 of the control device 80, or by a signal processing circuit (not shown) built into the imaging element 73, or by both.

In addition, by providing the aperture mechanism 60, it is possible to prevent unnecessary light other than the reflected light from the object 200 from entering the camera 70. This improves the S/N ratio in the image of the object 200, and therefore the color contrast, allowing the tilt angle to be calculated accurately. In addition, in the image of the object 200, the shape of the surface of the object 200 can be grasped with good contrast. The aperture diameter in the aperture mechanism 60 is dynamically controlled by the aperture control unit 83 of the control device 80.

The surface light source 10 is composed of a red light source 10R that emits red light, a green light source 10G that emits green light, and a blue light source 10B that emits blue light, arranged in a plane.

The red light source 10R, the green light source 10G, and the blue light source 10B are each a self-luminous light source such as an organic EL light-emitting element or an LED.

A color distribution is imparted to the inspection light by changing the ratio of the number of emitted light beams among the red light source 10R, the green light source 10G, and the blue light source 10B within the light emission surface of the surface light source 10, or by changing the respective brightness ratios among the red light source 10R, the green light source 10G, and the blue light source 10B. The ratio of the number of emitted light beams and the brightness ratios are dynamically changed by the light source control unit 82 of the control device 80.

In this way, the ratio of the number of emitted light or the brightness ratio of red light source 10R, green light source 10G, and blue light source 10B in this embodiment can be dynamically changed, and the color distribution of the inspection light can be set to a desired distribution depending on the material and shape of article 200. Note that if the material or shape of article 200 to be inspected does not change significantly, it is not necessary to dynamically change the ratio of the number of emitted light or the brightness ratio. This will be described later.

In addition, when the luminances of the red light, green light, and blue light at an arbitrary position within the light irradiation surface of the inspection light are IR, IG, and IB, respectively,
IR+αIG+βIB=S...(2)
Here, α and β are coefficients greater than zero, and S is a constant.

In this way, the color balance of the image captured by the camera 70 can be appropriately adjusted even when the surface of the object 200 has multiple directions or when the object 200 is made of a different material. It also becomes possible to quantitatively and accurately calculate the direction of the surface of the object 200, specifically the inclination angle of the surface.

When the surface light source 10 is circular in a planar view, it is preferable that the saturation of the inspection light changes so that the saturation decreases from the outer periphery of the surface light source 10 toward the center O.

Furthermore, it is preferable that the luminances IR, IG, and IB of the red, green, and blue light respectively change according to the rotation angle θ around the outer periphery of the surface light source 10.

Furthermore, the sum of the luminance of the red light, the green light, and the blue light is S, the normalized distance from the center O of the surface light source 10 is r, and the normalized amplitude of the inspection light at the distance r is m. In this case,
m=S×((1-r)/(3-2r))...(9)
It is preferable that the following relationship is satisfied: where S≧3m, 0≦r≦1, and 0≦m≦1.

In this way, it is possible to impart a color distribution to the inspection light that satisfies the relationship shown in equation (2) at any position within the light irradiation surface of the inspection light.

It is preferable that the ratio of the number of emitted light or the brightness ratio is determined so as to satisfy the relationship shown in formula (2) and formula (9), respectively.

In this way, the color balance of the image captured by the camera 70 can be appropriately adjusted even when the surface of the object 200 has multiple directions or when the object 200 is made of different materials. In addition, the color distribution of the inspection light, specifically the RGB luminance ratio, can be continuously changed within the light exit surface of the inspection light.

In addition, it becomes possible to quantitatively and accurately calculate the surface direction of the article 200, specifically the inclination angle of the surface.

In addition, in this embodiment, the red light source 10R, the green light source 10G, and the blue light source 10B in the surface light source 10 are each an organic EL light-emitting element, and the transparent plate 11 on which they are mounted is a flexible substrate.

If the transparent plate 11 is a flexible substrate, it can be curved appropriately to suppress the reduction in the amount of peripheral light in the inspection light. In addition, chromatic aberration, mainly in the peripheral areas, can be easily corrected.

The inspection system 100 also includes a control device 80. The control device 80 includes a light source control unit 82, a calculation unit 84, and a display unit 87.

As mentioned above, by providing the light source control unit 82, it is possible to dynamically change the ratio of the number of emitted light or the brightness ratio of the red light source 10R, the green light source 10G, and the blue light source 10B within the light emission surface of the surface light source 10. This makes it possible to impart a desired color distribution to the inspection light.

Furthermore, by providing the calculation unit 84, it is possible to calculate the inclination angle of the surface of the article 200 based on the image of the article 200 captured by the camera 70. Furthermore, by providing the display unit 87, it is possible to easily check whether there are scratches or stains on the surface of the article 200 and whether the direction of the surface of the article 200 is in the set direction based on the image of the article 200 captured by the camera 70.

The method for correcting the inclination angle of the surface of the object 200 according to this embodiment includes the following first to fourth steps.

In the first step, inspection light is irradiated onto the item 200, and an image of the item 200 is captured by the camera 70.

In the second step, a reference plane is set on the surface of the article 200.

In the third step, an offset is calculated based on the image of the reference surface. This offset corresponds to the inclination of the item 200 relative to the inspection system 100.

In the fourth step, the aforementioned inclination angle is corrected by subtracting the offset calculated in the third step from the inclination angle at each part of the surface of the article 200 obtained in the first step.

When actually inspecting the appearance of the item 200, the item 200 may not be placed correctly on the support table 90 due to reasons such as a slight misalignment in the transport system or vibrations being applied to the item 200 during transport and installation.

According to this embodiment, even if the item 200 is not correctly placed on the support base 90, the influence of this can be removed, the direction of the surface of the item 200 can be correctly estimated, and the inclination angle can be accurately calculated. In addition, the inclination of the item 200 itself can be removed to make the surface of the item 200 easier to observe. For example, if the surface of the item 200 has multiple directions, the appearance of the item 200 can be easily inspected by removing the inclination of a desired location within the item 200. In addition, the average value of the inclinations at multiple locations within the item 200 can be selected as the inclination of the item 200 itself, and the average value can be subtracted from the inclination angle at each part of the surface of the item 200.

The method of correcting the inclination angle of the surface of the article 200 is not particularly limited to this. For example, the inspection light is made monochromatic and irradiated onto the article 200, and an image of the object is obtained. Furthermore, the color distribution of the inspection light is changed to, for example, the pattern shown in FIG. 7, and the inspection light is irradiated onto the article 200, and an image of the object is obtained. The former image obtained by irradiating the monochromatic inspection light is used to perform color calibration of the latter image. The inclination angle of the surface of the article 200 is calculated based on the image after color calibration. In the following description, the monochromatic inspection light may be referred to as the first inspection light, and the inspection light to which a color distribution has been added may be referred to as the second inspection light. The second inspection light includes at least light in the same wavelength band as the monochromatic light and light in a wavelength band different from the monochromatic light. In this way, the inclination angle of the surface of the article 200 can be accurately calculated.

When color calibrating the test light, it is preferable to use images obtained by irradiating three types of monochromatic test light, namely red light, green light, and blue light.

In addition, in this embodiment, the inspection light is given the above-mentioned color distribution, but the surface light source 10 may be a white light source that emits white light. In this case, the red light source 10R, the green light source 10G, and the blue light source 10B do not need to be controlled independently. Even when the surface light source 10 is a white light source, since a half mirror is not used, the efficiency of use of the inspection light and reflected light used in the visual inspection of the item 200 can be significantly improved compared to the conventional configuration disclosed in Patent Document 1. Furthermore, by improving the efficiency of use of the inspection light and reflected light, the exposure time when capturing an image of the item 200 can be shortened. This allows the visual inspection time to be shortened.

In addition, by not using a half mirror, the number of parts in the inspection system 100 can be reduced, and the distance between the optical components in the illumination device 50 can be shortened. This allows the inspection system 100 to be made more compact.

<Modification 1>
Fig. 10 is a schematic diagram illustrating the color distribution of the inspection light according to the modification 1. Fig. 11A is a schematic diagram illustrating the color distribution of blue light in the inspection light. Fig. 11B is a schematic diagram illustrating the color distribution of red light in the inspection light.

For ease of explanation, in Figures 10, 11A, 11B, and the following figures, the same parts as those in embodiment 1 are designated by the same reference numerals, and detailed explanations are omitted.

The shape of the surface light source 10 is not limited to that shown in FIG. 2, and may be, for example, a rectangle in plan view, as shown in FIG. 10.

In this case, the inspection light is also given a color distribution that satisfies the relationship shown in equation (2). However, in this modified example, α=2, β=1, and S=2 are set.

IR+2IG+IB=2...(2A)
In addition, the luminance IB of the blue light changes continuously or stepwise along one side of the surface light source 10, and the luminance IR of the red light changes continuously or stepwise along another side perpendicular to the one side. Alternatively, a color distribution is imparted to the inspection light so as to change in stages.

In the example shown in FIG. 10, the luminance IB of blue light increases continuously or stepwise along the X direction, and the luminance IR of red light increases continuously or stepwise along the Y direction. Specifically, the luminance distributions of red light and blue light are set as shown in FIG. 11A and FIG. 11B, respectively.

The luminance IG of the green light is changed within the surface of the surface light source 10 so as to satisfy formula (2A). For example, the luminance IG of the green light is set so that at the center of the surface light source 10, IR:IG:IB = 0.5:0.5:0.5, at the tip of the imaginary line shown by the dashed line (arrow portion), IR:IG:IB = 1:0:1, and at the base end, IR:IG:IB = 0:1:0.

In other words, in the surface light source 10 shown in this modified example, one of red light, green light, and blue light is selected as the first color. Of the brightness of each of the red light, green light, and blue light, the brightness of the first color changes continuously or stepwise along one side of the surface light source 10.

The brightness of the second color, excluding the first color, among the red, green, and blue lights, changes continuously or stepwise along one side that intersects with the other side.

According to this modified example, even if the shape of the surface light source 10 is rectangular, unlike in the first embodiment, it is possible to achieve the same effect as the configuration shown in the first embodiment. That is, even if the surface of the object 200 has multiple directions or the object 200 is made of a different material, it is possible to appropriately adjust the color balance of the image captured by the camera 70. In addition, it is possible to quantitatively and accurately calculate the direction of the surface of the object 200, specifically the inclination angle of the surface.

<Modification 2>
Fig. 12A is a schematic diagram showing a color distribution in a light emission surface of a surface light source according to Modification 2. Fig. 12B is a schematic diagram showing another color distribution in a light emission surface of a surface light source according to Modification 2. Fig. 12C is a schematic diagram showing yet another color distribution in a light emission surface of a surface light source according to Modification 2.

As shown in FIG. 12A, the color distribution on the light exit surface of the surface light source 10 may be divided into three along the outer circumferential direction from the center O. In the example shown in FIG. 12A, the inspection light is emitted so that the red area RA, the green area GA, and the blue area BA are arranged side by side in the clockwise direction. The areas of the red area RA, the blue area BA, and the green area GA are set to be the same.

Also, as shown in FIG. 12B, the color distribution on the light exit surface of the surface light source 10 may be divided into three concentric circles along the radial direction from the center O. In the example shown in FIG. 12B, the inspection light is emitted so that a circular blue area BA is arranged at the innermost radial position, and a green area GA and a red area RA are arranged concentrically outside of that, in that order.

As shown in FIG. 7, by setting the color distribution within the emission surface of the surface light source 10, it is possible to continuously change the intensity ratio of RGB in both the radial and circumferential directions of the surface light source 10. This makes it possible to accurately calculate the inclination angle of each surface even when there are multiple surfaces with different directions on the surface of the article 200.

On the other hand, if the surface of the article 200 has multiple faces with different orientations, and it is only necessary to roughly determine the direction of inclination of each face, a color distribution may be imparted to the inspection light, as shown in Figures 12A and 12B.

Also, as shown in FIG. 12C, a red area RA may be provided only at a specific position in the surface light source. Note that white light, which is a mixture of red light, green light, and blue light, is emitted from areas other than the red area RA. By imparting a color distribution to the inspection light as shown in FIG. 12C, the image of the item 200 captured by the camera 70 appears reddish only when the surface of the item 200 is tilted in a specific direction. In other words, it is possible to evaluate only the presence or absence of tilt in a specific direction on the surface of the item 200. Note that in FIG. 12C, the position of the red area RA may be changed as appropriate. Also, a green area GA or a blue area BA may be arranged instead of the red area RA.

As described above, within the light emission surface of the surface light source 10, the ratio of the number of emitted light and the brightness ratio of the red light source 10R, the green light source 10G, and the blue light source 10B may be changed as appropriate according to the required specifications for the appearance inspection of the item 200. In other words, the color distribution is not particularly limited to the patterns shown in Figure 7 and Figures 12A to 12C. The ratio of the number of emitted light and the brightness ratio are dynamically changed by the light source control unit 82 of the control device 80.

(Embodiment 2)
Fig. 13 is a schematic diagram of a surface light source 10 according to embodiment 2. Fig. 14 is a schematic diagram of a white surface light source 13 included in the surface light source 10 shown in Fig. 13. Fig. 15 is a plan view schematic of a color filter 20 included in the surface light source 10 shown in Fig. 13.

The surface light source 10 shown in Fig. 13 differs from the surface light source 10 of embodiment 1 shown in Figs. 1 and 2 in that it is composed of a white surface light source 13, a light diffusion plate 12, and a color filter 20. As shown in Fig. 14, the white surface light source 13 has a holding frame 14, a light guide plate 15, and a white linear light source 16. The white linear light source 16 is a linear light source consisting of multiple white LEDs arranged in a row.

As shown in FIG. 15, the color filter 20 is composed of red filters 20R, green filters 20G, and blue filters 20B, each of which is periodically arranged on a transparent plate 21. In this case, the transparent plate 21 is made of a glass substrate, and is provided with a driving transistor (not shown). Each filter is arranged with a distance d between adjacent filters, and reflected light from the area between the filters travels toward the camera 70.

The red filter 20R transmits the red light of the incident white light, the green filter 20G transmits the green light of the incident white light, and the blue filter 20B transmits the blue light of the incident white light. Note that the arrangement shown in FIG. 13 is merely an example and is not particularly limited to this. Also, the wavelength ranges of the red light, green light, and blue light are the same as those shown in embodiment 1.

The function of the light diffusion plate 12 is the same as that described in the first embodiment. That is, the light diffusion plate 12 diffuses white light in a direction parallel to the XY plane.

In other words, the white light emitted from the white line light source 16 propagates inside the light guide plate 15, is further diffused by the light diffusion plate 12, and is emitted as planar light toward the color filter 20. The white planar light that has passed through the color filter 20 is irradiated onto the object 200 as inspection light with a color distribution.

Also, as shown in FIG. 14, the light guide plate 15 is rectangular when viewed from the Z direction, and four white line light sources 16 are provided so as to be in contact with each of its four side surfaces. However, the shape of the light guide plate 15 and the number and arrangement of the white line light sources 16 are not particularly limited to those shown in FIG. 14. For example, the white line light sources 16 may be arranged so as to be in contact with one or two side surfaces of the light guide plate 15. Furthermore, the shape of the light guide plate 15 does not have to be rectangular.

In this embodiment, the color distribution imparted to the inspection light by the color filter 20 is the same as the color distribution shown in embodiment 1.

When the color filter 20 is a liquid crystal color filter and the operation of the color filter 20 is controlled by the light source control unit 82, the position and number of the red filters 20R that transmit red light can be changed dynamically. Similarly, the positions and numbers of the green filters 20G and blue filters 20B that transmit green light and blue light, respectively, can also be changed dynamically.

In other words, in this embodiment, the arrangement ratio of the red filters 20R, green filters 20G, and blue filters 20B that transmit red light, green light, and blue light, respectively, corresponds to the ratio of the number of emitted light of the red light source 10R, green light source 10G, and blue light source 10B described in embodiment 1.

In light of this, in this specification, the arrangement ratio and the aforementioned light-emitting number ratio are sometimes collectively referred to as the arrangement area ratio. Note that the arrangement area ratio may also change depending on the position within the light emission surface of the surface light source 10. In addition, the aforementioned brightness ratio and transmittance ratio may also change depending on the position within the light emission surface of the surface light source 10.

The transmittance of each of the red filter 20R, green filter 20G, and blue filter 20B is also dynamically changed by the light source control unit 82 of the control device 80.

In other words, the transmittance ratios of the red filter 20R, the green filter 20G, and the blue filter 20B in this embodiment correspond to the luminance ratios of the red light source 10R, the green light source 10G, and the blue light source 10B described in embodiment 1.

In other words, the layout area ratio or transmittance ratio of the red filter 20R, green filter 20G, and blue filter 20B in this embodiment can be dynamically changed. Therefore, similar to the effect of the configuration shown in embodiment 1, the color distribution of the inspection light can be set to a desired distribution depending on the material and shape of the article 200.

In addition, by appropriately setting the layout area ratio or transmittance ratio of the red filter 20R, green filter 20G, and blue filter 20B in the color filter 20, it is possible to impart the color distribution shown in embodiment 1 and modification example 1 to the inspection light.

This allows the color balance of the image captured by the camera 70 to be appropriately adjusted even when the surface of the object 200 has multiple directions or the object 200 is made of a different material. In addition, the color distribution of the inspection light, specifically the RGB luminance ratio, can be continuously changed within the light exit surface of the inspection light.

In addition, it becomes possible to quantitatively and accurately calculate the surface direction of the article 200, specifically the inclination angle of the surface.

If the material or shape of the item 200 to be inspected does not change significantly, the arrangement area ratio or transmittance ratio does not need to be dynamically changed. Depending on the material or shape of the item 200, the red filter 20R, green filter 20G, and blue filter 20B may be built into the surface of the transparent plate 21 with the arrangement area ratio, i.e., their respective positions and areas, fixed. In this case, the transmittance ratios of the red filter 20R, green filter 20G, and blue filter 20B may be similarly built into the surface of the transparent plate 21 with the ratios fixed according to the positions at which the respective filters are arranged.

In view of this, in embodiment 1, red light source 10R, green light source 10G, and blue light source 10B may be built into the surface of transparent plate 21 with the layout area ratio, i.e., their respective positions and areas, being fixed. Similarly, in embodiment 1, red light source 10R, green light source 10G, and blue light source 10B may be built into the surface of transparent plate 21 with the luminance ratio being fixed according to their respective positions.

The color distribution shown in Figures 12A to 12C may also be realized by the color filter 20. In that case, the layout area ratio or transmittance ratio of the red filter 20R, green filter 20G, and blue filter 20B may be changed dynamically, or may be built into the surface of the transparent plate 21 in advance.

Note that when the layout area ratio or transmittance ratio of the red filter 20R, green filter 20G, and blue filter 20B is dynamically changed, the color distribution of the inspection light is not particularly limited to the patterns shown in Figure 7 and Figures 12A to 12C.

Furthermore, when using the surface light source 10 in this embodiment to correct the inclination angle of the surface of the article 200, a method similar to that shown in embodiment 1 can be adopted.

In other words, the first inspection light, which is monochromatic light, is irradiated onto the article 200, and an image of the article is acquired. Furthermore, the second inspection light, which has a predetermined color distribution, is irradiated onto the article 200, and an image of the article is acquired. This color distribution may be, for example, the pattern shown in FIG. 7. The image acquired by irradiating the article with the first inspection light is used to perform color calibration of the image acquired by irradiating the article with the second inspection light. The inclination angle of the surface of the article 200 is calculated based on the image after color calibration.

In this way, the inclination angle of the surface of the item 200 can be accurately calculated.

When color calibrating the test light, it is preferable to use images obtained by irradiating three types of monochromatic test light, namely red light, green light, and blue light.

When generating such a monochromatic first inspection light, the color filters 20 may be liquid crystal color filters and each filter may be dynamically controlled, or other methods may be used. For example, a monochromatic color filter 20 may be prepared, and the color filter 20 may be replaced as appropriate, and an image of the object 200 may be acquired each time.

In other words, to change the color distribution of the inspection light, multiple color filters 20 that impart different color distributions may be prepared, and the color filters 20 may be replaced depending on the shape and material of the item 200, and the required specifications for the appearance inspection of the item 200, as described above.

Furthermore, in this embodiment, the color filter 20 may be omitted from the surface light source 10, and the surface light source 10 may be configured with a white surface light source 13 and a light diffusion plate 12. In this case, too, since a half mirror is not used, the efficiency of use of the inspection light and reflected light used in the visual inspection of the item 200 can be significantly improved compared to the conventional configuration disclosed in Patent Document 1. Furthermore, by improving the efficiency of use of the inspection light and reflected light, the exposure time when capturing an image of the item 200 can be shortened. This allows the visual inspection time to be shortened.

In addition, by not using a half mirror, the number of parts in the inspection system 100 can be reduced, and the distance between the optical components in the illumination device 50 can be shortened. This allows the inspection system 100 to be made more compact.

(Embodiment 3)
FIG. 16 is a schematic diagram showing how the light emitting region of the surface light source 10 according to the third embodiment is switched.

The surface light source 10 in this embodiment is configured to be capable of being driven by switching between a first mode in which the entire surface emits light and a second mode in which the surface emits light partially. Figure 16 shows how the light-emitting area of the surface light source 10 is switched in the second mode.

In the example shown in FIG. 16, the white and black areas of the surface light source 10 are non-light-emitting areas. In other words, the surface light source 10 of this embodiment shown in FIG. 16 differs from the surface light source 10 shown in embodiment 1 in that the light-emitting area is dynamically changed. Note that in the example shown in FIG. 16, the surface light source 10 is configured so that the light-emitting area and non-light-emitting area switch with respect to a center line that passes through the center O and extends in the Y direction, but is not particularly limited to this. It is sufficient that the surface light source 10 is configured so that the position and light-emitting area of the light-emitting area are variable in the second mode.

In addition, in this embodiment, images of the article 200 are acquired in both the first mode and the second mode. Furthermore, the difference between the images of the article 200 acquired in both the first mode and the second mode is calculated, and the characteristic parts of the article 200, particularly the characteristic parts of the surface of the article 200, are extracted and emphasized based on the images after the difference.

In this way, it is possible to emphasize and observe unevenness on the surface of the item 200. For example, if there are scratches or stains on the surface of the item 200, it is possible to accurately grasp the position and size of these. Furthermore, if there are minute unevenness on the surface of the item 200, it is possible to detect the unevenness and estimate the direction of the surface.

In the second mode, the position or area or both of the light-emitting region in the surface light source 10 may be changed as appropriate, and an image of the object 200 may be acquired each time. In this case, the difference between the images of the multiple objects 200 acquired by changing the position or area of the light-emitting region and the image of the object 200 acquired in the first mode is calculated.

In this way, the position and size of irregularities on the surface of the item 200 can be observed in detail.

(Embodiment 4)
Fig. 17A shows a schematic plan view of the surface light source 10 according to the fourth embodiment, and Fig. 17B shows a schematic plan view of another surface light source 10. For ease of explanation, the light sources of each color (red light source 10R, green light source 10G, blue light source 10B) and the filters of each color (red filter 20R, green filter 20G, blue filter 20B) are omitted in Fig. 17A and Fig. 17B.

The inspection system 100 shown in this embodiment differs from the inspection system 100 shown in embodiment 1 in that the central portion of the surface light source 10, in other words the area through which the optical axis OAi of the inspection light and the optical axis OAr of the reflected light pass, is transparent or has an opening. Furthermore, the inspection system 100 shown in this embodiment is configured so that the reflected light passes through the central portion of the surface light source 10 and enters the camera 70.

For example, the surface light source 10 shown in FIG. 17A has a central portion that is a transparent area TA that transmits reflected light. The transparent area TA is a member made of the same material as the transparent plate 11 or the transparent plate 21. However, the light sources of each color (red light source 10R, green light source 10G, blue light source 10B) and the filters of each color (red filter 20R, green filter 20G, blue filter 20B) are not provided. The transparent area TA may be integrated with the transparent plate 11 or the transparent plate 21.

The central portion of the surface light source 10 shown in FIG. 17B is an opening area EA where no components are arranged. In other words, the central portion of the surface light source 10 is a through opening.

In the surface light source 10 shown in embodiment 1, one of the light sources of each color (red light source 10R, green light source 10G, blue light source 10B) is arranged in the central portion of the surface light source 10 where the reflected light is incident. In the surface light source 10 shown in embodiment 2, one of the filters of each color (red filter 20R, green filter 20G, blue filter 20B) is arranged in the central portion of the surface light source 10 where the reflected light is incident.

In this way, when light sources of each color (red light source 10R, green light source 10G, blue light source 10B) or filters of each color (red filter 20R, green filter 20G, blue filter 20B) are arranged in the central portion of the surface light source 10 where the reflected light is incident, these light sources and filters may absorb or scatter part of the reflected light. In this case, the amount of light received by the camera 70 may be reduced, or the image of the object 200 may be distorted.

On the other hand, according to this embodiment, by making the central portion of the surface light source 10 a transparent area TA or an opening area EA, it is possible to prevent the reflected light from the object 200 from being reflected or scattered by the surface light source 10 when it enters the camera 70. This significantly improves the efficiency of using the reflected light used in visual inspection of the object 200. Furthermore, by improving the efficiency of using the reflected light, it is possible to shorten the exposure time when capturing an image of the object 200. This makes it possible to shorten the visual inspection time. Furthermore, it is possible to suppress distortion of the image of the object 200, and it is possible to observe the surface shape of the object 200 with high accuracy. Furthermore, it is possible to calculate the inclination angle of the surface of the object 200 with high accuracy.

When the central portion of the surface light source 10 is a transparent area TA as shown in FIG. 17A, it is preferable to provide an anti-reflection layer (not shown) on both sides of the transparent area TA, i.e., on the surface on which the reflected light is incident and on the surface opposite thereto. This can prevent the reflected light from being reflected on the surface of the transparent area TA, and further improve the efficiency of use of the reflected light when generating an image of the article 200.

<Modification 3>
Fig. 18A shows a schematic cross-sectional view of a surface light source 10 according to Modification Example 3, and Fig. 18B shows a schematic cross-sectional view of another surface light source. For ease of explanation, the light sources of each color (red light source 10R, green light source 10G, and blue light source 10B) are omitted in Fig. 18A and Fig. 18B.

The inspection system 100 shown in this modified example differs from the inspection system 100 shown in embodiment 4 in that the surface light source 10 is configured so that parts other than the central part do not transmit reflected light.

Specifically, the surface light source 10 shown in Figures 18A and 18B has an anti-transmission member 17 provided on the light exit surface, in other words, the surface facing the reflected light incidence surface, except for the transparent area TA or the opening area EA. The anti-transmission member 17 is a member made of a material that absorbs reflected light. The transparent plate 11 and the anti-transmission member 17 may be in contact with each other, or may be spaced apart from each other.

According to this modified example, it is possible to prevent unnecessary light other than the reflected light from the object 200 from being incident on the camera 70. This improves the S/N ratio in the image of the object 200, and therefore the color contrast, allowing the tilt angle to be calculated accurately. Also, in the image of the object 200, the shape of the surface of the object 200 can be grasped with good contrast. Furthermore, according to this modified example, it is possible to omit the aperture mechanism 60, thereby reducing the number of parts and the cost of the inspection system 100.

In addition, in the surface light source 10 shown in FIG. 18A, inspection light leaks into the transparent area TA from the surroundings, so some light is also irradiated from the transparent area TA toward the item 200.

On the other hand, with the surface light source 10 shown in FIG. 18B, inspection light is not emitted from the opening area EA, so the center of the image of the item 200 captured by the camera 70 appears black, and the surface condition cannot be recognized. However, in the peripheral parts of the image, the surface condition of the item 200 can be recognized based on the reflected light. In other words, when the surface light source 10 shown in FIG. 18B is used, although it is not possible to perform an appearance inspection of the central part of the item 200, it is possible to reliably perform an appearance inspection of the peripheral part. Based on this, it is possible to determine whether to use the surface light source 10 shown in FIG. 18A or the surface light source 10 shown in FIG. 18B, depending on the required specifications for the appearance inspection of the item 200.

In addition, in the surface light source 10 shown in FIG. 18A, the transparent area TA and the other portion, i.e., the portion where the anti-transmission member 17 is provided, may be separate entities.

For example, the transparent area TA is a glass substrate with an anti-reflection layer on its surface, and the portion where the anti-transmission member 17 is provided is the surface light source 10 shown in FIG. 18B. These may be combined to form the surface light source 10 shown in FIG. 18A.

The surface light source 10 shown in FIG. 18B may be a component having the configuration shown in embodiment 2, that is, a surface light source 10 consisting of a white surface light source 13 and a color filter 20, with a transmission prevention member 17 added. Similarly, in the surface light source 10 shown in FIG. 18A, the portion where the transmission prevention member 17 is provided may be a component having a transmission prevention member 17 added to a surface light source 10 consisting of a white surface light source 13 and a color filter 20.

In addition, in the surface light source 10 shown in FIG. 18A, light sources of each color (red light source 10R, green light source 10G, blue light source 10B) may be arranged in the transparent area TA. In addition, in the surface light source 10 shown in FIG. 18A, the portion where the transmission prevention member 17 is provided may be a surface light source 10 consisting of a white surface light source 13 and a color filter 20, and filters of each color (red filter 20R, green filter 20G, blue filter 20B) may be arranged in the transparent area TA.

In this case, the reflected light may be absorbed or scattered when passing through the transparent area TA. However, by providing the anti-transmission member 17, it is possible to prevent unnecessary light other than the reflected light from the object 200 from entering the camera 70. This improves the S/N ratio in the image of the object 200, and therefore the color contrast, allowing the inclination angle to be calculated accurately. Furthermore, the shape of the surface of the object 200 can be seen with good contrast in the image of the object 200.

The transmission prevention member 17 may be made of a material that reflects reflected light. In this case, it is also possible to prevent unnecessary light other than the reflected light from the object 200 from being incident on the camera 70.

Other Embodiments
New embodiments can be created by appropriately combining the components shown in the first to fourth embodiments and the first to third modifications. For example, the light guide plate 15 and the color filter 20 shown in the second embodiment may have a rectangular shape in a plan view. In this case, the color distribution imparted to the inspection light by the color filter 20 can be made the same as the color distribution shown in the first modification by appropriately setting the layout area ratio or transmittance ratio of the red filter 20R, the green filter 20G, and the blue filter 20B.

In addition, in the surface light source 10 of the second modified example shown in Figures 12A to 12C, a transparent area TA or an opening area EA may be provided as shown in the fourth embodiment.

The inspection system disclosed herein is useful because it improves the efficiency of use of the inspection light and reflected light used in visual inspection of objects.

10 Surface light source 10R Red light source 10G Green light source 10B Blue light source 11 Transparent plate 12 Light diffusion plate 13 White surface light source 14 Holding frame 15 Light guide plate 16 White line light source 17 Transmission prevention member 20 Color filter 20R Red filter 20G Green filter 20B Blue filter 21 Transparent plate 30 Objective lens 40 Housing 50 Illumination device 60 Aperture mechanism 70 Camera (imaging device)
71 Housing 72 Lens 73 Imaging element 80 Control device 81 Signal processing unit 82 Light source control unit 83 Aperture control unit 84 Calculation unit 85 Memory unit 86 Input unit 87 Display unit 90 Support base 100 Inspection system 200 Article 201 Cross mark OAi Optical axis of inspection light OAr Optical axis of reflected light RA Red area GA Green area BA Blue area

Claims (18)

An inspection system comprising: an illumination device that irradiates an object with inspection light; and an imaging device that images the object irradiated with the inspection light,
The lighting device includes:
a surface light source that emits the inspection light;
an objective lens that focuses the inspection light emitted from the surface light source toward the object,
The inspection light is incident on the objective lens in a state in which a predetermined color distribution is imparted to the inspection light in a plane intersecting a traveling direction thereof,
the imaging device is disposed on an optical path of the reflected light of the inspection light reflected by the article and on an opposite side of the objective lens across the surface light source,
the surface light source is disposed at or near a focal position on an incident side of the objective lens, and is configured to transmit the reflected light at least in a portion where the reflected light toward the imaging device is incident;
An inspection system in which the optical axis of the inspection light and the optical axis of the reflected light are arranged coaxially. 2. The inspection system according to claim 1,
the surface light source is configured by arranging a red light source that emits red light, a green light source that emits green light, and a blue light source that emits blue light in a plane;
An inspection system that imparts the color distribution to the inspection light by setting a layout area ratio between the red light source, the green light source, and the blue light source, or a luminance ratio between the red light source, the green light source, and the blue light source, or both the layout area ratio and the luminance ratio to desired ratios. 2. The inspection system according to claim 1,
The inspection system, wherein the surface light source includes at least a white surface light source that emits white light, and a color filter that imparts the color distribution to the white light. 4. The inspection system according to claim 3,
the color filter is configured by arranging a red filter that transmits red light, a green filter that transmits green light, and a blue filter that transmits blue light in a planar manner;
An inspection system that imparts the color distribution to the inspection light by setting a layout area ratio between the red filter, the green filter, and the blue filter, or a transmittance ratio between the red filter, the green filter, and the blue filter, or both the layout area ratio and the transmittance ratio to a desired ratio. 5. The inspection system according to claim 2,
At an arbitrary position within the light irradiation surface of the inspection light, the luminances of the red light, the green light, and the blue light are IR, IG, and IB, respectively.
IR+αIG+βIB=S...(2)
An inspection system that satisfies the relationship shown in
Here, α and β are coefficients greater than zero, and S is a constant. 6. The inspection system according to claim 5,
When the surface light source is circular in a plan view,
the saturation of the inspection light changes so as to decrease from the outer periphery toward the center of the surface light source,
An inspection system in which the brightness of each of the red light, the green light, and the blue light varies according to a rotation angle along the outer periphery of the surface light source. 7. The inspection system according to claim 6,
The sum of the luminance of the red light, the green light, and the blue light is S,
The normalized distance from the center of the surface light source is r,
When the normalized amplitude of the inspection light at the distance r is m,
m=S×((1-r)/(3-2r))...(9)
An inspection system that satisfies the relationship shown in
Here, S≧3m, 0≦r≦1, and 0≦m≦1. 6. The inspection system according to claim 5,
When the surface light source is rectangular in a plan view,
Among the luminances of the red light, the green light, and the blue light, the luminance of a first color changes continuously or stepwise along one side of the surface light source;
An inspection system in which the brightness of a second color, excluding the first color, among the red light, the green light, and the blue light varies continuously or stepwise along another side intersecting the one side. 2. The inspection system according to claim 1,
An inspection system in which the surface light source has a central portion that is transparent or has an opening through which the reflected light passes to the imaging device. 9. The inspection system according to claim 8,
An inspection system configured such that the reflected light is not transmitted through any portion of the surface light source other than a central portion. 2. The inspection system according to claim 1,
The surface light source is configured to be drivable by switching between a first mode in which the entire surface emits light and a second mode in which the surface emits light partially;
In the second mode, the inspection system is configured so that a light emitting position and a light emitting area are variable. 2. The inspection system according to claim 1,
A predetermined color is imparted to the inspection light only at a specific position on the light emission surface of the surface light source,
The inspection system wherein the inspection light emitted from any other position is white light. 2. The inspection system according to claim 1,
the imaging device includes an imaging element that receives the reflected light,
An inspection system in which an aperture mechanism is provided between the imaging element and the surface light source to limit the optical path of the reflected light directed toward the imaging element. 5. The inspection system according to claim 2,
An inspection system that quantitatively calculates at least one of the angle and direction of the surface of the object with respect to the image of the object captured by the imaging device, depending on each of the red light, green light, and blue light components contained in the inspection light. A method for correcting a tilt angle of a surface of an article using the inspection system according to claim 1, comprising the steps of:
irradiating the article with the inspection light and acquiring an image of the article with the imaging device;
irradiating the article with a first inspection light, which is a monochromatic light, and acquiring an image of the article with the imaging device;
Further, the method includes irradiating the object with the second inspection light having the color distribution and acquiring an image of the object with the imaging device.
performing color calibration of the image acquired by irradiating the second inspection light using the image acquired by irradiating the first inspection light;
and calculating a tilt angle of the surface of the article based on the color-calibrated image,
The method for correcting a tilt angle of a surface of an article, wherein the second inspection light includes light in the same wavelength band as the first inspection light and light in a different wavelength band from the first inspection light. A method for correcting a tilt angle of a surface of an article using the inspection system according to claim 1, comprising the steps of:
a first step of irradiating the object with the inspection light and acquiring an image of the object with the imaging device;
A second step of establishing a reference plane on a surface of the article;
a third step of calculating an offset based on the image of the reference surface;
and a fourth step of correcting the inclination angle by subtracting the offset calculated in the third step from the inclination angle at each portion of the surface of the article obtained in the first step,
A method for correcting for tilt of a surface of an article, wherein the offset corresponds to a tilt of the article relative to the inspection system. 12. A method for enhancing features of an image of an article obtained using the inspection system of claim 11, comprising the steps of:
a first step of acquiring an image of the object when the surface light source is driven in the first mode;
a second step of acquiring an image of the object when the surface light source is driven in the second mode;
a third step of determining a difference between the image of the article obtained in the first step and the image of the article obtained in the second step, and emphasizing a characteristic portion of the article based on the image after the difference. 20. The method for enhancing features of an image of an article according to claim 17, further comprising:
In the second step, a position or an area, or both the position and the area, of a light emitting region of the surface light source are changed to acquire images of a plurality of the articles;
In the third step, a difference is calculated between the image of the object obtained in the first step and the images of the multiple objects obtained in the second step, and a characteristic portion of the object is emphasized based on the images after subtraction.

Images