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

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 tilt angle of object surface using the same, and method for enhancing feature of object image

[0001] The present disclosure relates to an inspection system used for visual inspection of an article, a method for correcting the tilt angle of the surface of an article using the same, and a method for enhancing features of an image of an article.

[0002] Conventionally, as lighting devices used for visual inspection of articles, the configurations disclosed in Patent Documents 1 to 3 are known.

[0003] In the conventional configuration disclosed in Patent Document 1, a filter member is disposed between a surface light source and an objective lens. This filter member is disposed 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.

[0004] By configuring the illumination device in this way, inspection light having the same illumination solid angle is irradiated at each point on the surface of the article, thereby making it possible to make the illumination conditions the same at each point on the surface of the article.Furthermore, it is possible to observe the article with high resolution and to recognize the inclination angle of the surface of the article over a wide range.

[0005] 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 lens of the camera.

[0006] 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 article. The wavelengths and illumination solid angles of the inspection light emitted from the first to nth optical members toward the article are different from one another. In this way, the reflected light from the article has a wavelength corresponding to the degree of inclination of the surface of the article. The degree of inclination of the local surface of the article can be determined by checking the image captured by the camera.

[0007] The configuration disclosed in Patent Document 3 further includes emitting inspection light from a portion of the surface light source and irradiating the object with the inspection light while sequentially scanning the inspection light emission position in a first direction. Subsequently, the inspection light is irradiated onto the object while sequentially scanning the inspection light emission position in a second direction different from the first direction. The control unit identifies the inspection light emission position 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, the first direction, and the second direction.

[0008] In this way, the control unit can acquire information about 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 of the camera. Therefore, it is possible to inspect an object without the need for calibration between the camera and the lighting device.

[0009] Japanese Patent No. 7206020 JP 2019-138682 A JP 2021-183989 A

[0010] However, in the conventional configuration disclosed in Patent Document 1, a half mirror is disposed 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 is approximately halved before and after passing through the half mirror. Also, when the light reflected from the object passes through the half mirror and enters the camera, the amount of reflected light is approximately halved before and after passing through the half mirror. In other words, the amount of reflected light actually used for visual inspection of the object is approximately ¼ of the amount of the original inspection light.

[0011] The present disclosure has been made in consideration of these points, and its purpose is to provide an inspection system that can improve the utilization efficiency of inspection light and reflected light used in the visual inspection of an article, a method for correcting the inclination angle of the surface of an article using the same, and a method for emphasizing the features of an image of an article.

[0012] To achieve the above object, the present disclosure provides an inspection system including an illumination device that irradiates an object with inspection light and an imaging device that images the object illuminated 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 imparted within a plane intersecting the direction of travel. The imaging device is disposed on the optical path of the reflected light of the inspection light reflected by the object, on the opposite side of the surface light source from the objective lens. The surface light source is disposed at or near the focal position on 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 enters. The optical axis of the inspection light and the optical axis of the reflected light are disposed coaxially.

[0013] According to the present disclosure, since a half mirror is not used, the utilization efficiency of the inspection light and the reflected light used in the visual inspection of an article can be improved. In addition, the number of parts in the inspection system can be reduced, and the inspection system can be made smaller.

[0014] 1 is a schematic diagram illustrating the configuration of an inspection system according to a first embodiment. FIG. 1 is a schematic plan view of a surface light source included in the inspection system shown in FIG. 1. FIG. 1 is a schematic diagram illustrating the illumination solid angle of inspection light irradiated onto an article. FIG. 2 is a diagram illustrating an example of an article placed on a support stand. FIG. 3 is a schematic diagram illustrating the state of reflected light when the surface of the article is inclined. FIG. 4 is a schematic diagram illustrating the state of reflected light when the surface of the article is inclined in another way. FIG. 5 is a diagram illustrating an example of the wavelength dependence of the reflectance of a metal. FIG. 6 is a diagram illustrating the color distribution within the light emission surface of a surface light source. FIG. 7 is a diagram illustrating the rotation angle dependence of light brightness at the outermost periphery of a surface light source. FIG. 7 is a schematic diagram illustrating the configuration of an inspection system when an article is not properly placed on the support stand. FIG. 8 is a schematic diagram illustrating an image of an article when an article is not properly placed on the support stand. FIG. 9 is a schematic diagram illustrating the color distribution of inspection light according to a first modification. FIG. 10 is a schematic diagram illustrating the color distribution of red light in the inspection light. FIG. 11 is a schematic diagram illustrating the color distribution of blue light in the inspection light. FIG. 12 is a schematic diagram illustrating the color distribution within the light emission surface of a surface light source according to a second modification. FIG. 13 is a schematic diagram illustrating another color distribution within the light emission surface of a surface light source according to a second modification. 14 is a schematic diagram showing yet another color distribution in the light emission surface of a surface light source according to Modification 2. FIG. 15 is a schematic configuration diagram of a surface light source according to embodiment 2. FIG. 16 is a schematic configuration diagram of a white surface light source included in the surface light source shown in FIG. 13. FIG. 17 is a schematic plan view of a color filter included in the surface light source shown in FIG. 13. FIG. 18 is a schematic diagram showing how the light-emitting region of a surface light source according to embodiment 3 is switched. FIG. 19 is a schematic plan view of a surface light source according to embodiment 4. FIG. 20 is a schematic cross-sectional view of a surface light source according to Modification 3. FIG. 21 is a schematic cross-sectional view of another surface light source according to Modification 3.

[0015] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the present disclosure, its applications, or its uses.

[0016] [Configuration and Operation of Inspection System] Fig. 1 is a schematic configuration diagram of an inspection system 100 according to this embodiment, and Fig. 2 is a plan view schematic diagram of a surface light source 10 included in the inspection system 100. In the following description, the optical axis direction of the inspection light may be referred to as the Z direction, the direction perpendicular to the Z axis may be referred to as the X direction, and the directions perpendicular to both the X and Z directions may be referred to as the Y direction. Furthermore, a plane or virtual plane that includes the X and Y directions may be referred to as an XY plane.

[0017] In this specification, "orthogonal," "parallel," or "matching (being the same)" means being orthogonal, parallel, or matching or the same, taking into account the manufacturing tolerances of each component that makes up 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.

[0018] 1 , the inspection system 100 includes an illumination device 50, a camera (imaging device) 70, and a support base 90. The illumination device 50 is disposed inside a housing 40. The inspection system also includes an aperture mechanism 60 and a control device 80.

[0019] As will be described in detail later, in the inspection system 100, an illumination device 50 irradiates an object 200 placed on a support table 90 with inspection light, and a camera 70 captures an image of the inspection light reflected by the object 200 (hereinafter simply referred to as reflected light). Based on the image captured by the camera 70, the appearance of the object 200 is inspected.

[0020] Illumination device 50 is composed of a surface light source 10 and an objective lens 30. Surface light source 10 is composed of red light source 10R, green light source 10G, blue light source 10B, and a light diffusion plate 12. Surface light source 10 is disposed at the focal position of objective lens 30, in this case, at focal position P1 on the incident side.

[0021] 2, red light sources 10R, green light sources 10G, and blue light sources 10B are periodically arranged on transparent plate 11. Note that the arrangement shown in FIG. 2 is merely an example, and is not particularly limited to this.

[0022] The light diffusion plate 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 diffusion plate 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 approximately several tens of nm to 100 nm. The green light includes a wavelength of 500 nm and has a wavelength range of approximately several tens of nm to 100 nm. The blue light includes a wavelength of 450 nm and has a wavelength range of approximately several tens of nm to 100 nm.

[0023] 2 , when red light source 10R, green light source 10G, and blue light source 10B are turned on simultaneously, the light emitted from these light sources is diffused by light diffusion plate 12, and the inspection light emitted from surface light source 10 becomes white planar light. The positions and regions in surface light source 10 where red light source 10R, green light source 10G, and blue light source 10B emit light are controlled by light source control unit 82 of control device 80. The light source control unit 82 can also change the luminance ratio of red light source 10R, green light source 10G, and blue light source 10B in the light-emitting region of surface light source 10. To change the luminance ratio, the ratio of the number of light-emitting light sources 10R, green light source 10G, and blue light source 10B in the light-emitting region may be changed, or the light-emitting intensity of each of red light source 10R, green light source 10G, and blue light source 10B may be changed.

[0024] 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 further finely changed within the light-emitting region of the surface light source 10. This imparts a predetermined color distribution to the inspection light 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.

[0025] Furthermore, red light source 10R, green light source 10G, and blue light source 10B are each arranged on transparent plate 11 at a predetermined interval. Therefore, the light reflected by article 200 passes through light diffusion plate 12 of surface light source 10 and transparent plate 11 and proceeds toward camera 70. Furthermore, as shown in Fig. 1, the components of 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. That is, in 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.

[0026] In the example shown in FIG. 1 , red light source 10R, green light source 10G, and blue light source 10B are each organic EL (Electro Luminescence) light-emitting elements, and transparent plate 11 is a bendable flexible substrate. However, this is not particularly limited, and red light source 10R, green light source 10G, and blue light source 10B may each be configured with LEDs (Light Emitting Diodes). In that case, transparent plate 11 is a glass substrate. Although not shown, wiring connecting the light-emitting elements is formed on the surface of transparent plate 11 on which the organic EL light-emitting elements, LEDs, and other light-emitting elements are installed.

[0027] 2, adjacent light sources within the plane of the transparent plate 11 are arranged at a predetermined distance d. The distance d is an area through which reflected light passes toward the camera 70, and its value is set appropriately depending on the amount of light required for the camera 70 to capture an image of the article 200.

[0028] The objective lens 30 focuses the inspection light emitted from the surface light source 10 toward the object 200. Furthermore, 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.

[0029] The diaphragm mechanism 60 is disposed between the camera (imaging device) 70 and the surface light source 10, more specifically, between the imaging element 73 provided in the camera 70 and the surface light source 10. The diaphragm mechanism 60 limits the optical path of the reflected light that is inspection light reflected by the article 200 and travels toward the camera 70. In the example shown in FIG. 1 , the operation of the diaphragm mechanism 60 is controlled by the diaphragm control unit 83 of the control device 80. However, this is not limiting, and the diaphragm mechanism 60 may be operated manually. Furthermore, the diaphragm mechanism 60 may be disposed at the focal position P1 described above or in the vicinity of the focal position P1.

[0030] The support table 90 has a flat surface on which the article 200 is placed.

[0031] The camera 70 has a lens 72 and an image pickup element 73 inside a housing 71. Although not shown, other optical components and electrical components are also arranged inside the housing 71.

[0032] The light reflected by the article 200 passes through the surface light source 10 and the diaphragm mechanism 60, is collected by the lens 72, and is incident on the imaging surface of the imaging element 73. The imaging element 73 outputs an image signal of the article 200 based on the incident reflected light. In other words, the camera 70 captures an image of the article 200 irradiated with the inspection light. In reality, the image signal output from the imaging element 73 is processed in a signal processing unit of the control device 80, and an image of the article 200 is generated.

[0033] The image captured by the camera 70 is a color image, and the image capturing element 73 is a CMOS (Complementary Metal Oxide Semiconductor) image sensor equipped with a color filter.

[0034] The camera 70 may include a processor (not shown) that processes the output signal of the CMOS image sensor to generate an image, in which case the signal processing unit 81 may be omitted.

[0035] It should be noted that the camera 70 may be provided with an aperture mechanism (not shown). In this case, the aperture mechanism 60 can be omitted. Even when 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.

[0036] 1 shows a single lens 72, but in reality, the lens 72 is configured as a lens group having multiple lenses. For example, the lens group 72 includes, in order of proximity to the image sensor 73, an imaging lens, an eyepiece, and an objective lens. In this case, the objective lens 30 and the lens group 72 form an object-side telecentric optical system for reflected light. If an aperture mechanism is provided in the camera 70, the aperture mechanism is provided between the eyepiece and the objective lens.

[0037] The control device 80 has a signal processing unit 81, a light source control unit 82, an aperture control unit 83, a calculation unit 84, a storage unit 85, an input unit 86, and a display unit 87 as a plurality of functional blocks.

[0038] The signal processing unit 81 is composed of one or more signal processing LSIs (Large Scale Integrated Circuits) including a GPU (Graphics Processing Unit) etc., and as described above, performs signal processing of the image signal output from the imaging element 73 and generates an image of the item 200 illuminated with the inspection light.

[0039] 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.

[0040] 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 operations of red light source 10R, green light source 10G, and blue light source 10B.

[0041] The calculation unit 84 is composed of one or more CPUs, and performs calculations related to feature enhancement of the image of the article 200, which will be described later. It also performs calculations to correct the tilt angle of the article 200. These calculations are performed based on the signal processing results in the signal processing unit 81.

[0042] The storage unit 85 is configured with one or more semiconductor memories, such as a random access memory (RAM) or a read-only memory (ROM). The storage unit 85 may also be configured with a hard disk drive (HDD) or a solid state drive (SSD). The storage 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 calculation unit 84, and the results of the arithmetic processing. The storage unit 85 also stores images of the item 200 that have undergone signal processing by the signal processing unit 81. The inspection program is configured to allow multiple color distribution patterns to be set when performing an appearance inspection. The light source control unit 82 controls the light emission operations of the red light source 10R, the green light source 10G, and the blue light source 10B in the surface light source 10 according to these color distribution patterns.

[0043] The input unit 86 is configured with an input device such as a keyboard or a touch panel. By operating the input unit 86, images stored in the storage unit 85 are called up. The type of the item 200 to be inspected is also input, and the corresponding inspection program is called up. Images of the item 200 after the visual inspection are also called up.

[0044] Furthermore, by operating the input unit 86, parameters necessary for enhancing the features of the image of the article 200 and correcting the tilt angle may be input.

[0045] The display unit 87 is configured with a display device such as a liquid crystal display, an organic EL display, etc. The display unit 87 displays an image of the article 200 after the visual inspection, an input screen for the inspection program, etc.

[0046] 1, the signal processing unit 81 to the display unit 87 are integrated, but this is not limiting. 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 as a single PC (Personal Computer). It is sufficient that the control device 80 is configured so that necessary signals can be exchanged between the multiple functional blocks.

[0047] [Operation of the Inspection System] Fig. 3 is a schematic diagram showing the solid angle of irradiation of the inspection light irradiated onto the article. Fig. 4 is an example showing the article 200 placed on a support table. Fig. 5A is a schematic diagram showing the state of reflected light when the surface of the article 200 is tilted, and Fig. 5B is a schematic diagram showing the state of reflected light when the surface of the article 200 is tilted in a different way.

[0048] First, the operating principle of the inspection system 100 will be described.

[0049] When the surface light source 10 and the 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 whose vertex is a predetermined point on the optical path of the inspection light and indicates the range over which light is irradiated at that predetermined point (see, for example, Figure 3). 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 Equation (1).

[0050] θ1=tan−1(r1 / 2f) (1) Furthermore, even at a position away from the optical axis OAi of the inspection light, the illumination solid angle IS at a position the same distance from the center of the objective lens 30 as the exit-side focal position of the objective lens 30 also has the same shape and size as the illumination solid angle IS at point P2. Furthermore, the illumination solid angle IS at a position farther away than the exit-side focal position of the objective lens 30 also has the same shape and size as the illumination solid angle IS at point P2.

[0051] 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.

[0052] Next, the actual visual inspection of the article 200 will be described.

[0053] When the surface of the article 200 is flat and parallel to the surface of the support table 90, the optical axis OAi of the inspection light is parallel to the normal to the surface of the article 200, as shown in Fig. 1. If the inspection light emitted from the surface light source 10 is white light, the light reflected by the surface of the article 200 is also white light. For example, the light reflected from an area S1 on the surface of the article 200 shown in Fig. 4 is incident on the camera 70 as white light.

[0054] On the other hand, as described 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 is in a different direction from the optical axis of the inspection light emitted from blue light source 10B. Also, as described 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 tilted, the color of the reflected light changes corresponding to the change in the direction of the optical axis of the inspection light.

[0055] As shown in Fig. 5A , when the surface of article 200 is tilted to the left side of the paper, the inspection light emitted from blue light source 10B is reflected toward the imaging surface of camera 70. On the other hand, a portion of the inspection light emitted from red light source 10R is reflected away from the imaging surface of camera 70. As a result, the image of article 200 captured by camera 70 appears bluish. For example, area S2 on the surface of article 200 shown in Fig. 4 is captured by camera 70 as a bluish area.

[0056] 5B , when the surface of the article 200 is tilted to the right of the paper, the inspection light emitted from the red light source 10R is reflected toward the imaging surface of the camera 70. On the other hand, 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 appears reddish. 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.

[0057] As described above, according to 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 orientation (tilt) of the surface of the article 200 can be estimated from the intensities of each color, for example, red light, green light, and blue light (hereinafter, these may be collectively referred to as RGB), in the image captured by the camera 70. In other words, if the surface of the article 200 is composed of multiple surfaces whose relative orientations can be determined, the orientation of each surface can be estimated. This can be utilized to perform an appearance inspection of the article 200. For example, it is possible to inspect the surface irregularities and the presence or absence of scratches on the article 200, which are difficult to identify using only white light irradiation.

[0058] [Setting Color Distribution in Surface Light Sources] Fig. 6 is a diagram showing an example of wavelength dependency of reflectance of metals. Fig. 7 is a diagram showing color distribution in the light emission surface of a surface light source. Fig. 8 is a diagram showing rotation angle dependency of light luminance at the outermost periphery of a surface light source.

[0059] When estimating the surface direction of the article 200 described above, it is necessary to appropriately adjust the color balance in the image of the captured article 200. In general, a white article 200 is imaged for each lighting environment, and the RGB intensities are adjusted.

[0060] 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 approximately 1 in the visible light range (400 nm to 700 nm). On the other hand, the reflectance of gold (Au) decreases from 1 to approximately 0.4 at wavelengths from 650 nm to 500 nm. Furthermore, in the wavelength range of 500 nm or less, the reflectance remains approximately constant at approximately 0.4. The reflectance of copper (Cu) decreases from 1 to approximately 0.5 at wavelengths from 650 nm to 400 nm. In light of this, color balance adjustment is necessary even when the material of the object 200 to be inspected is different.

[0061] 1, however, the color of the inspection light irradiated onto the article 200 varies depending on the direction of irradiation of the article 200, corresponding to the color distribution of the inspection light. Therefore, if the surface of the article 200 has multiple faces with different directions (inclinations), the reflected light from the article 200 will also have a different color on each face.

[0062] In such a case, the color balance in the image of the article 200 can be adjusted appropriately by setting the color distribution of the inspection light as shown below.

[0063] A method for setting the color distribution of the inspection light in this embodiment will be described below.

[0064] 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 provided 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 provided 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.

[0065] On the other hand, the inspection light emitted from different positions on the light emitting surface satisfies the relationship shown in formula (2).

[0066] IR+αIG+βIB=S (2) where IR, IG, and IB are the luminances of red, green, and blue light, respectively. α and β are coefficients greater than zero, and in the example shown in this embodiment, α=β=1. S is a constant.

[0067] That is, the inspection light is set so that the sum of the luminances of the red light, green light, and blue light is constant regardless of the position within the light exit surface.

[0068] In addition, the inspection light is 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 circumference of the surface light source 10) changes.

[0069] 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 depending on the rotation angle θ. At the same time, the brightness of each of the red light, green light, and blue light also changes depending on the distance r. As the distance r decreases, that is, as the distance approaches the center O, the saturation of the inspection light decreases. For example, when θ is 120°, the brightness IG of the green light is at its maximum (=S), while the brightness IR of the red light and the blue light IB are both zero. However, as the distance r decreases and the area approaches the center O, the brightness of the red light and the blue light each increases above zero.

[0070] These are expressed as the relationships shown in the following equations (3) to (9).

[0071] First, the distance r is normalized, and the normalized amplitude m of the inspection light at the distance r is set as shown in equation (3).

[0072] m=min(R, G, B) (3) Here, R, G, and B are the normalized intensities IR, IG, and IB of red light, green light, and blue light, respectively.

[0073] 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.

[0074] r=VR / (VR+m)=(S-3m) / (S-2m) (4) Here, the fluctuation range VR satisfies the relationship shown in equation (5).

[0075] VR=S-3m (5) Furthermore, S, r, and m satisfy the relationships shown in equations (6) to (8), respectively.

[0076] 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.

[0077] 8, at any position on the light exit surface of the inspection light, the ratios of the luminance of the red light, the luminance of the green light, and the luminance of the blue light are determined according to the distance r and the rotation angle θ. However, as described above, even when the rotation angle θ or the distance r changes, the sum of the luminances of the red light, the green light, and the blue light remains constant.

[0078] 7 and 8, when the color distribution is imparted to the inspection light, the number of light emitted from the red light source 10R, the green light source 10G, and the 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, the green light source 10G, and the blue light source 10B is changed at each position.

[0079] 7 and 8, by adding a color distribution to the inspection light, the inclination of the surface of the article 200 can be quantitatively evaluated. This inclination is expressed as an inclination angle based on an image of the article 200 captured by the camera 70, with the surface of the article 200 being a flat surface perpendicular to the optical axis of the inspection light. The inclination angle of the surface of the article 200 (hereinafter sometimes simply referred to as the inclination angle) is calculated by the calculation unit 84 of the control device 80.

[0080] [Regarding correction of the inclination angle of an object] Figure 9A shows a schematic diagram of the inspection system when an object is not properly placed on the support table, and Figure 9B shows a schematic diagram of an image of an object when an object is not properly placed on the support table.

[0081] If the article 200 is not properly installed on the support base 90, an offset may be added to the tilt angle calculated by the calculation unit 84 of the control device 80, and the correct value may not be obtained. Also, there may be cases where it is desired to remove the tilt of the article 200 as an offset.

[0082] In such a case, the tilt angle can be calculated accurately by removing the offset using the procedure described below.

[0083] As shown in Fig. 9A, when the article 200 is placed at an angle relative to the support table 90, even if the surface of the article 200 is flat or has a certain degree of flatness with some unevenness, the image of the article 200 is colored in a color corresponding to the angle relative to the support table 90. When an image of the article 200 is acquired in the placement state shown in Fig. 9A, the image of the article 200 shown in Fig. 9B has a bluish tint.

[0084] Here, a reference point (hereinafter referred to as a 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 known in advance to be flat. Furthermore, in order to extract the reference plane from the image of the article 200, it is preferable that the reference plane include a characteristic shape, as shown in FIG. 9B . It goes without saying that the characteristic shape is not limited to the cross mark 201.

[0085] Next, an offset is calculated based on the image of the reference plane, specifically, the color of the image and the intensity of its brightness.

[0086] Furthermore, the offset obtained above is uniformly subtracted from the tilt angle at each part of the article 200 calculated based on the image of the article 200 .

[0087] In this manner, the offset superimposed on the tilt angle calculated by the calculation unit 84 can be appropriately removed, and the tilt angle of the surface of the article 200 can be accurately determined. The offset described using Figures 9A and 9B corresponds to the tilt of the article 200 relative to the support table 90. Including the tilt of the article 200 itself, the offset in this specification is defined as the tilt of the article 200 relative to the inspection system 100. Note that if the surface of the article 200 has multiple directions, the tilt of the article 200 itself includes the tilt of any location within the article 200, the average of the tilts at multiple locations within the article 200, etc.

[0088] [Effects, etc.] As described above, the inspection system 100 according to this embodiment includes an illumination device 50 that irradiates the item 200 with inspection light, and a camera (imaging device) 70 that captures an image of the item 200 irradiated with the inspection light.

[0089] The illumination 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 .

[0090] The inspection light is incident on the objective lens 30 with a predetermined color distribution given to it in a plane intersecting the traveling direction.

[0091] The camera 70 is disposed on the optical path of the inspection light reflected by the article 200, and on the opposite side of the surface light source 10 from the objective lens 30.

[0092] The surface light source 10 is disposed at or near a focal position P1 on the incident side of the objective lens 30, and is configured to transmit reflected light. The optical axis OAi of the inspection light and the optical axis OAr of the reflected light are arranged coaxially.

[0093] As described above, in the conventional configuration disclosed in Patent Document 1, the ratio of the amount of reflected light incident on the camera 70 to the amount of original inspection light is about 1 / 4.

[0094] On the other hand, according to the present embodiment, since a half mirror is not used, the utilization efficiency of the inspection light and reflected light used in the visual inspection of the article 200 can be significantly improved compared to the conventional configuration disclosed in Patent Document 1. Furthermore, the improved utilization efficiency of the inspection light and reflected light can shorten the exposure time when capturing an image of the article 200. This can shorten the visual inspection time.

[0095] Furthermore, by not using a half mirror, the number of components in the inspection system 100 can be reduced, and the distance between components of the optical system in the illumination device 50 can be shortened. This allows the inspection system 100 to be made more compact.

[0096] The camera 70 has an image sensor 73 that receives reflected light. It is preferable that an aperture mechanism 60 that limits the optical path of the reflected light directed toward the image sensor 73 is provided between the image sensor 73 and the surface light source 10.

[0097] It is to be noted that the calculation of the tilt angle is facilitated when the color image generated by the image sensor 73 is a digital image. The signal output from the image sensor 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 image sensor 73, or by both.

[0098] Furthermore, by providing the diaphragm mechanism 60, it is possible to suppress the incidence of unnecessary light other than the light reflected from the article 200 on the camera 70. This improves the S / N ratio in the image of the article 200, and in turn the color contrast, allowing the tilt angle to be calculated accurately. Furthermore, the shape of the surface of the article 200 can be grasped with good contrast in the image of the article 200. The aperture diameter of the diaphragm mechanism 60 is dynamically controlled by the diaphragm control unit 83 of the control device 80.

[0099] The surface light source 10 is configured by arranging 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 in a plane.

[0100] Red light source 10R, green light source 10G, and blue light source 10B are each a self-luminous light source such as an organic EL light-emitting element or an LED.

[0101] A color distribution is imparted to the inspection light by changing the ratio of the number of light emitted by the red light source 10R, the green light source 10G, and the blue light source 10B, or by changing the respective luminance ratios 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. The luminance ratios and luminance ratios are dynamically changed by the light source control unit 82 of the control device 80.

[0102] In this manner, the ratio of the number of light emitters 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 light emitters or the brightness ratio. This will be described later.

[0103] Furthermore, at any position within the light irradiation surface of the inspection light, when the luminances of the red light, green light, and blue light are IR, IG, and IB, respectively, the following relationship is satisfied: IR+αIG+βIB=S (2) where α and β are coefficients greater than zero, and S is a constant.

[0104] In this way, it is possible to appropriately adjust the color balance of the image captured by the camera 70 even when the surface of the article 200 has multiple directions or when the article 200 is made of different materials. It is also possible to quantitatively and accurately calculate the direction of the surface of the article 200, specifically the inclination angle of the surface.

[0105] When the surface light source 10 has a circular shape in a plan view, it is preferable that the saturation of the inspection light changes so as to decrease from the outer periphery toward the center O of the surface light source 10 .

[0106] 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.

[0107] Furthermore, the sum of the luminances of the red light, green light, and 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, it is preferable to satisfy the relationship shown below: m=S×((1−r) / (3−2r)) (9) where S≧3m, 0≦r≦1, and 0≦m≦1.

[0108] In this way, it is possible to impart a color distribution that satisfies the relationship shown in formula (2) to the inspection light at any position within the light irradiation surface of the inspection light.

[0109] The ratio of the number of light-emitting elements or the brightness ratio is preferably determined so as to satisfy the relationships shown in formulas (2) and (9), respectively.

[0110] In this way, the color balance of the image captured by the camera 70 can be appropriately adjusted even when the surface of the article 200 has multiple directions or when the article 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.

[0111] Furthermore, it becomes possible to quantitatively and accurately calculate the direction of the surface of the article 200, specifically the inclination angle of the surface.

[0112] 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 these are mounted is a flexible substrate.

[0113] If the transparent plate 11 is a flexible substrate, it can be appropriately curved to suppress a decrease in the amount of peripheral light in the inspection light. Also, chromatic aberration, mainly in the peripheral area, can be easily corrected.

[0114] 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.

[0115] As described above, the provision of the light source control unit 82 makes it 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.

[0116] 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, based on the image of the article 200 captured by the camera 70, 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 a set direction.

[0117] The method for correcting the inclination angle of the surface of the article 200 according to this embodiment includes the following first to fourth steps.

[0118] In the first step, inspection light is irradiated onto the article 200 and an image of the article 200 is captured by the camera 70 .

[0119] In the second step, a reference plane is set on the surface of the article 200 .

[0120] In a third step, an offset is calculated based on the image of the reference surface, which offset corresponds to the tilt of the article 200 relative to the inspection system 100.

[0121] In the fourth step, the tilt angle is corrected by subtracting the offset calculated in the third step from the tilt angle at each part of the surface of the article 200 obtained in the first step.

[0122] During an actual visual inspection 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 conveying system or vibrations being applied to the item 200 during transportation and placement.

[0123] According to this embodiment, even if the article 200 is not correctly installed on the support base 90, the influence of this can be removed, the direction of the surface of the article 200 can be correctly estimated, and the tilt angle can be accurately calculated. Furthermore, the tilt of the article 200 itself can be removed to make the surface of the article 200 easier to observe. For example, if the surface of the article 200 has multiple directions, removing the tilt at a desired location within the article 200 can make it easier to inspect the appearance of the article 200. Furthermore, the tilt of the article 200 itself can be determined by selecting an average value of the tilts at multiple locations within the article 200, and subtracting this average value from the tilt angle at each location on the surface of the article 200.

[0124] The method for correcting the inclination angle of the surface of the article 200 is not particularly limited to this. For example, monochromatic inspection light is irradiated onto the article 200, and an image of the object 200 is acquired. Furthermore, the color distribution of the inspection light is changed, for example, to the pattern shown in FIG. 7 , and the object 200 is irradiated with the monochromatic inspection light, and an image of the object 200 is acquired. The former image acquired by irradiating the monochromatic inspection light is used to perform color calibration on the latter image. The inclination angle of the surface of the article 200 is calculated based on the color-calibrated image. In the following description, the monochromatic inspection light may be referred to as the first inspection light, and the inspection light to which the color distribution has been applied 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. This allows the inclination angle of the surface of the article 200 to be accurately calculated.

[0125] In addition, 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.

[0126] Furthermore, in this embodiment, the inspection light is given the above-described 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, no half mirror is used, so the utilization efficiency of the inspection light and reflected light used in the visual inspection of the article 200 is significantly improved compared to the conventional configuration disclosed in Patent Document 1. Furthermore, by improving the utilization efficiency of the inspection light and reflected light, the exposure time when capturing an image of the article 200 can be shortened. This shortens the visual inspection time.

[0127] Furthermore, by not using a half mirror, the number of components in the inspection system 100 can be reduced, and the distance between components of the optical system in the illumination device 50 can be shortened. This allows the inspection system 100 to be made more compact.

[0128] <Modification 1> Fig. 10 is a schematic diagram illustrating the color distribution of the inspection light according to 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.

[0129] For the sake of convenience, in FIGS. 10, 11A, 11B and the following drawings, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0130] The shape of the surface light source 10 is not limited to that shown in FIG. 2, and may be, for example, a square in plan view as shown in FIG.

[0131] In this case as well, the inspection light is 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.

[0132] IR + 2IG + IB = 2 ... (2A) In addition, a color distribution is imparted to the inspection light so that the brightness IB of the blue light changes continuously or stepwise along one side of the surface light source 10, and the brightness IR of the red light changes continuously or stepwise along another side perpendicular to the one side.

[0133] 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 FIGS. 11A and 11B, respectively.

[0134] The luminance I of the green light is changed within the surface of the surface light source 10 so as to satisfy the formula (2A). For example, the luminance I of the green light is set so that IR:IG:IB = 0.5:0.5:0.5 at the center of the surface light source 10, IR:IG:IB = 1:0:1 at the tip (arrow portion) of the imaginary line shown by the dashed line, and IR:IG:IB = 0:1:0 at the base end.

[0135] That is, in the surface light source 10 shown in this modification, 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.

[0136] The luminance of the second color, excluding the first color, of the red, green, and blue lights varies continuously or stepwise along the other side intersecting with the one side.

[0137] According to this modification, 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 that achieved by the configuration shown in the first embodiment. That is, even if the surface of the article 200 has multiple directions or the article 200 is made of a different material, it is possible to appropriately adjust the color balance of the image captured by the camera 70. Furthermore, it is possible to quantitatively and accurately calculate the direction of the surface of the article 200, specifically the inclination angle of the surface.

[0138] <Modification 2> Fig. 12A is a schematic diagram showing a color distribution within the light emission surface of a surface light source according to Modification 2. Fig. 12B is a schematic diagram showing another color distribution within the light emission surface of a surface light source according to Modification 2. Fig. 12C is a schematic diagram showing yet another color distribution within the light emission surface of a surface light source according to Modification 2.

[0139] 12A , the color distribution on the light exit surface of the surface light source 10 may be divided into three regions along the circumferential direction from the center O. In the example shown in FIG. 12A , the inspection light is emitted so that a red region RA, a green region GA, and a blue region BA are arranged side by side in the clockwise direction. The red region RA, the blue region BA, and the green region GA are set to have the same area.

[0140] 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 region BA is arranged at the innermost radial position, and a green region GA and a red region RA are arranged concentrically in this order outside the circular blue region BA.

[0141] 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 direction and the circumferential direction of the surface light source 10. This makes it possible to accurately calculate the inclination angle of each surface even when the surface of the article 200 has multiple surfaces with different directions.

[0142] On the other hand, if the surface of the article 200 has multiple faces with different directions, 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.

[0143] Furthermore, as shown in FIG. 12C , a red region RA may be provided only at a specific position on the surface light source. Note that white light, a mixture of red, green, and blue light, is emitted from areas other than the red region RA. By providing a color distribution to the inspection light as shown in FIG. 12C , the image of the article 200 captured by the camera 70 appears reddish only when the surface of the article 200 is tilted in a specific direction. In other words, it is possible to evaluate only whether the surface of the article 200 is tilted in a specific direction. Note that the position of the red region RA in FIG. 12C may be changed as appropriate. Alternatively, a green region GA or a blue region BA may be disposed instead of the red region RA.

[0144] As described above, within the light emission surface of surface light source 10, the ratio of the number of emitted light sources and the brightness ratio of red light source 10R, green light source 10G, and blue light source 10B may be changed as appropriate depending on the required specifications for visual inspection of article 200. In other words, the color distribution is not particularly limited to the patterns shown in Fig. 7 and Figs. 12A to 12C. The ratio of the number of emitted light sources and the brightness ratio are dynamically changed by light source control unit 82 of control device 80.

[0145] (Embodiment 2) Fig. 13 is a schematic configuration diagram of a surface light source 10 according to embodiment 2. Fig. 14 is a schematic configuration 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 diagram of a color filter 20 included in the surface light source 10 shown in Fig. 13.

[0146] The surface light source 10 shown in Fig. 13 differs from the surface light source 10 of the first embodiment shown in Fig. 1 and Fig. 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 also 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 formed by arranging a plurality of white LEDs in a row.

[0147] 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.

[0148] The red filter 20R transmits red light from the incident white light, the green filter 20G transmits green light from the incident white light, and the blue filter 20B transmits blue light from the incident white light. Note that the arrangement shown in Figure 13 is merely an example and is not particularly limited to this. The wavelength ranges of the red light, green light, and blue light are the same as those shown in embodiment 1.

[0149] 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.

[0150] That is, the white light emitted from the white linear 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 to which a color distribution has been imparted.

[0151] 14, the light guide plate 15 is rectangular when viewed from the Z direction, and four white linear light sources 16 are provided so as to contact each of its four side surfaces. However, the shape of the light guide plate 15 and the number and arrangement of the white linear light sources 16 are not particularly limited to those shown in FIG. 14. For example, the white linear light sources 16 may be arranged so as to contact 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.

[0152] 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 the first embodiment.

[0153] 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 dynamically changed. 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 dynamically changed.

[0154] In other words, in this embodiment, the arrangement ratio of the red filter 20R, the green filter 20G, and the blue filter 20B, which transmit red light, green light, and blue light, respectively, corresponds to the ratio of the number of light-emitting elements of the red light source 10R, the green light source 10G, and the blue light source 10B described in embodiment 1.

[0155] In light of this, in this specification, the arrangement ratio and the aforementioned light-emitting element number ratio may be collectively referred to as the arrangement area ratio. Note that the arrangement area ratio may also change depending on the position within the light-emitting surface of the surface light source 10. Furthermore, the aforementioned brightness ratio and transmittance ratio may also change depending on the position within the light-emitting surface of the surface light source 10.

[0156] The transmittance of each of the red filter 20R, the green filter 20G, and the blue filter 20B is also dynamically changed by the light source control unit 82 of the control device 80.

[0157] That is, 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 the first embodiment.

[0158] In other words, the layout area ratio or transmittance ratio of the red filter 20R, the green filter 20G, and the blue filter 20B in this embodiment can be dynamically changed, so that the color distribution of the inspection light can be set to a desired distribution depending on the material and shape of the article 200, just as in the configuration shown in embodiment 1.

[0159] Furthermore, 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 the color filter 20, it is possible to impart the color distribution shown in embodiment 1 and variant example 1 to the inspection light.

[0160] This makes it possible to appropriately adjust the color balance of the image captured by the camera 70 even when the surface of the article 200 has multiple directions or when the article 200 is made of different materials. Also, 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.

[0161] Furthermore, it becomes possible to quantitatively and accurately calculate the direction of the surface of the article 200, specifically the inclination angle of the surface.

[0162] Note that, if the material or shape of the object 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 object 200, the red filter 20R, the green filter 20G, and the 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, similarly, the transmittance ratios of the red filter 20R, the green filter 20G, and the blue filter 20B may be built into the surface of the transparent plate 21 with their respective filter arrangement positions fixed.

[0163] In view of this, in the first embodiment, red light source 10R, green light source 10G, and blue light source 10B may be built into the surface of transparent plate 21 with their layout area ratios, i.e., their respective positions and areas, fixed. Similarly, in the first embodiment, red light source 10R, green light source 10G, and blue light source 10B may be built into the surface of transparent plate 21 with their luminance ratios fixed according to their respective positions.

[0164] 12A to 12C may be realized by the color filter 20. In this case, the arrangement area ratio or transmittance ratio of the red filter 20R, the green filter 20G, and the blue filter 20B may be dynamically changed, or may be realized by being built into the surface of the transparent plate 21 in advance.

[0165] When the layout area ratio or transmittance ratio of the red filter 20R, the green filter 20G, and the blue filter 20B is dynamically changed, the color distribution of the inspection light is not particularly limited to the patterns shown in FIG. 7 and FIGS. 12A to 12C.

[0166] Furthermore, when the surface light source 10 of this embodiment is used to correct the tilt angle of the surface of the article 200, the same method as that shown in the first embodiment can be adopted.

[0167] That is, 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, to which a predetermined color distribution has been imparted, 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 tilt angle of the surface of the article 200 is calculated based on the image after color calibration.

[0168] In this way, the inclination angle of the surface of the article 200 can be calculated accurately.

[0169] In addition, 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.

[0170] To generate 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 employed. For example, a monochromatic color filter 20 may be prepared, and the color filter 20 may be replaced as needed, and an image of the article 200 may be acquired each time the color filter 20 is replaced.

[0171] In other words, when changing 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.

[0172] 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 utilization efficiency of the inspection light and reflected light used in the visual inspection of the article 200 can be significantly improved compared to the conventional configuration disclosed in Patent Document 1. Furthermore, by improving the utilization efficiency of the inspection light and reflected light, the exposure time when capturing an image of the article 200 can be shortened. This shortens the visual inspection time.

[0173] Furthermore, by not using a half mirror, the number of components in the inspection system 100 can be reduced, and the distance between components of the optical system in the illumination device 50 can be shortened. This allows the inspection system 100 to be made more compact.

[0174] Third Embodiment FIG. 16 is a schematic diagram showing how the light-emitting regions of the surface light source 10 according to the third embodiment are switched.

[0175] The surface light source 10 in this embodiment is configured to be driven by switching between a first mode in which the entire surface emits light and a second mode in which only a portion of the surface emits light. Fig. 16 shows how the light-emitting region of the surface light source 10 is switched in the second mode.

[0176] In the example shown in Fig. 16 , the black areas of the white area in 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 the non-light-emitting area are switched with respect to a center line that passes through the center O and extends in the Y direction, but this is not particularly limited. 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.

[0177] In this embodiment, images of the article 200 are acquired in both the first mode and the second mode. Furthermore, a difference between the images of the article 200 acquired in both the first mode and the second mode is calculated, and characteristic portions of the article 200, particularly characteristic portions of the surface of the article 200, are extracted and emphasized based on the image after the difference.

[0178] In this way, it is possible to emphasize and observe the unevenness, etc., of the surface of the article 200. For example, if there are scratches or stains on the surface of the article 200, it is possible to reliably grasp the position and size of these. Furthermore, if there are minute unevennesses on the surface of the article 200, it is possible to detect these unevennesses and estimate the direction of the surface.

[0179] In the second mode, the position and / or area of ​​the light-emitting region in the surface light source 10 may be changed as appropriate, and an image of the article 200 may be acquired each time. In this case, the differences between the images of the article 200 acquired in the first mode and the images of the article 200 acquired by changing the position, area, etc. of the light-emitting region are calculated.

[0180] By doing so, the position and size of irregularities on the surface of the article 200 can be observed in detail.

[0181] 17A shows a schematic plan view of a surface light source 10 according to a 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 from the illustration in FIGS. 17A and 17B.

[0182] 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.

[0183] For example, the surface light source 10 shown in Fig. 17A has a transparent area TA in the center that transmits reflected light. The transparent area TA is made of the same material as the transparent plate 11 or 21. However, the light sources of the respective colors (red light source 10R, green light source 10G, blue light source 10B) and the filters of the respective colors (red filter 20R, green filter 20G, blue filter 20B) are not provided. The transparent area TA may be integral with the transparent plate 11 or 21.

[0184] 17B is an opening area EA where no member is disposed. In other words, the central portion of the surface light source 10 is a through opening.

[0185] In the surface light source 10 shown in the first embodiment, one of the light sources of each color (red light source 10R, green light source 10G, blue light source 10B) is disposed in the central portion of the surface light source 10 where the reflected light is incident. In the surface light source 10 shown in the second embodiment, one of the filters of each color (red filter 20R, green filter 20G, blue filter 20B) is disposed in the central portion of the surface light source 10 where the reflected light is incident.

[0186] 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 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 camera 70 may be reduced, or the image of article 200 may be distorted.

[0187] 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 article 200 from being reflected or scattered by the surface light source 10 when it enters the camera 70. This significantly improves the utilization efficiency of the reflected light used in the visual inspection of the article 200. Furthermore, by improving the utilization efficiency of the reflected light, it is possible to shorten the exposure time when capturing an image of the article 200. This reduces the visual inspection time. Furthermore, it is possible to suppress distortion in the image of the article 200, allowing the surface shape of the article 200 to be observed with high accuracy. Furthermore, it is possible to accurately calculate the inclination angle of the surface of the article 200.

[0188] 17A , when the central portion of the surface light source 10 is a transparent region TA, it is preferable to provide an anti-reflection layer (not shown) on both surfaces of the transparent region TA, i.e., on the incident surface of the reflected light and the surface opposite to the incident surface. This prevents the reflected light from being reflected on the surface of the transparent region TA, further improving the utilization efficiency of the reflected light when generating an image of the article 200.

[0189] <Modification 3> Fig. 18A shows a schematic cross-sectional view of surface light source 10 according to Modification 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 from Figs. 18A and 18B.

[0190] The inspection system 100 shown in this modification is different from the inspection system 100 shown in the fourth embodiment in that the area light source 10 is configured so that the reflected light is not transmitted through the areas other than the central area.

[0191] 18A and 18B, a light source 10 is provided with a transmission preventing member 17 on the light exit surface, in other words, the surface facing the incident surface of reflected light, except for the transparent area TA or the opening area EA. The transmission preventing member 17 is made of a material that absorbs reflected light. The transparent plate 11 and the transmission preventing member 17 may be in contact with each other or may be spaced apart from each other.

[0192] According to this modification, it is possible to prevent unnecessary light other than the light reflected from the article 200 from being incident on the camera 70. This improves the S / N ratio in the image of the article 200, and in turn the color contrast, allowing the tilt angle to be calculated accurately. Furthermore, the shape of the surface of the article 200 can be grasped with good contrast in the image of the article 200. Furthermore, according to this modification, it is possible to omit the aperture mechanism 60, thereby reducing the number of parts and costs of the inspection system 100.

[0193] 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 article 200.

[0194] On the other hand, with the surface light source 10 shown in Figure 18B, inspection light is not emitted from the opening area EA, so the central portion of the image of the article 200 captured by the camera 70 appears black, making it impossible to recognize the surface condition. However, in the peripheral portion of the image, the surface condition of the article 200 can be recognized based on reflected light. In other words, when the surface light source 10 shown in Figure 18B is used, although it is not possible to perform an appearance inspection of the central portion of the article 200, it is possible to reliably perform an appearance inspection of the peripheral portion. In light of this, it can be determined whether to use the surface light source 10 shown in Figure 18A or the surface light source 10 shown in Figure 18B depending on the required specifications for the appearance inspection of the article 200, etc.

[0195] In the surface light source 10 shown in FIG. 18A, the transparent area TA and the other portion, that is, the portion where the transmission preventing member 17 is provided, may be separate bodies.

[0196] For example, the transparent area TA may be a glass substrate having an anti-reflection layer on its surface, and the area where the transmission preventing member 17 is provided may be the surface light source 10 shown in Fig. 18B. These may be combined to form the surface light source 10 shown in Fig. 18A.

[0197] 18B may be configured as a component having the configuration shown in embodiment 2, that is, a component having a transmission preventing member 17 added to the surface light source 10 consisting of a white surface light source 13 and a color filter 20. Similarly, in the surface light source 10 shown in FIG. 18A , the portion where the transmission preventing member 17 is provided may be configured as a component having a transmission preventing member 17 added to the surface light source 10 consisting of a white surface light source 13 and a color filter 20.

[0198] 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. Also, in the surface light source 10 shown in Fig. 18A, the portion where the transmission preventing member 17 is provided may be made into 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.

[0199] In this case, the reflected light may be absorbed or scattered when passing through the transparent area TA. However, by providing the transmission prevention member 17, it is possible to prevent unnecessary light other than the reflected light from the article 200 from entering the camera 70. This improves the S / N ratio and therefore the color contrast in the image of the article 200, allowing the tilt angle to be calculated accurately. Furthermore, the surface shape of the article 200 can be grasped with good contrast in the image of the article 200.

[0200] The transmission preventing 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 article 200 from entering the camera 70.

[0201] Other Embodiments New embodiments can be created by appropriately combining the components shown in Embodiments 1 to 4 and Modifications 1 to 3. For example, the light guide plate 15 and the color filter 20 shown in Embodiment 2 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 Modification 1 by appropriately setting the layout area ratio or transmittance ratio of the red filter 20R, the green filter 20G, and the blue filter 20B.

[0202] Furthermore, in the surface light source 10 of the second modification shown in FIGS. 12A to 12C, a transparent area TA or an opening area EA may be provided as in the fourth embodiment.

[0203] The inspection system of the present disclosure is useful because it can increase the utilization efficiency of inspection light and reflected light used in visual inspection of articles.

[0204] REFERENCE SIGNS LIST 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

1. An inspection system comprising an illumination device which irradiates an object with inspection light, and an imaging device which images the object irradiated with the inspection light, wherein the illumination device comprises: a surface light source which emits the inspection light; and an objective lens which focuses the inspection light emitted from the surface light source towards the object, wherein the inspection light is incident on the objective lens with a predetermined color distribution imparted within a plane intersecting the direction of travel, and 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, wherein 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 towards the imaging device is incident, and wherein the optical axis of the inspection light and the optical axis of the reflected light are arranged coaxially.

2. An inspection system according to claim 1, wherein 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 planar manner, and the inspection system imparts the color distribution to the inspection light by setting a desired ratio for the layout area ratio of the red light source, the green light source, and the blue light source, or a desired ratio for the luminance ratio of the red light source, the green light source, and the blue light source, or both the layout area ratio and the luminance ratio.

3. An inspection system according to claim 1, 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. An inspection system according to claim 3, wherein the color filters are 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, and the inspection system imparts the color distribution to the inspection light by setting the arrangement area ratio of the red filters, the green filters, and the blue filters, or the transmittance ratio of the red filters, the green filters, and the blue filters, or both the arrangement area ratio and the transmittance ratio, to a desired ratio.

5. An inspection system as claimed in claim 2 or 4, wherein, at any position within the light irradiation plane of the inspection light, the luminance of the red light, the green light and the blue light are IR, IG and IB, respectively, and the inspection system satisfies the relationship given by: IR + αIG + βIB = S ... (2), where α and β are coefficients greater than zero, and S is a constant.

6. An inspection system as described in claim 5, wherein, when the surface light source is circular in a planar view, the saturation of the inspection light changes so as to decrease from the outer periphery of the surface light source toward the center, and the luminance of each of the red light, green light, and blue light changes according to the rotation angle along the outer periphery of the surface light source.

7. An inspection system as claimed in claim 6, which satisfies the relationship given by: m = S × ((1 - r) / (3 - 2r)) ... (9) where S is the sum of the luminances of the red light, the green light and the blue light, r is the normalized distance from the center of the surface light source, and m is the normalized amplitude of the inspection light at the distance r, where S≧3m, 0≦r≦1, and 0≦m≦1.

8. An inspection system as described in claim 5, wherein, when the surface light source is rectangular in a planar view, among the luminance of each 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, and the luminance of a second color, excluding the first color, among the red light, the green light, and the blue light changes continuously or stepwise along another side intersecting with the one side.

9. An inspection system according to claim 1, wherein the surface light source has a central portion that is transparent or has an opening, and the reflected light passes through the central portion and enters the imaging device.

10. An inspection system according to claim 8, wherein the area light source is configured so that the reflected light is not transmitted through the area other than the central portion.

11. An inspection system as described in claim 1, wherein the surface light source is configured to be operable by switching between a first mode in which the entire surface emits light and a second mode in which the surface emits light partially, and wherein the light-emitting position and light-emitting area are configured to be variable in the second mode.

12. An inspection system according to claim 1, wherein the inspection light is given a predetermined color only at specific positions on the light emission surface of the surface light source, and the inspection light emitted from other positions is white light.

13. An inspection system according to claim 1, wherein the imaging device has an imaging element that receives the reflected light, and an aperture mechanism is provided between the imaging element and the surface light source that limits the optical path of the reflected light directed toward the imaging element.

14. An inspection system as claimed in claim 2 or 4, which quantitatively calculates at least one of the angle and direction of the surface of the object relative 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.

15. A method for correcting the inclination angle of the surface of an object using the inspection system described in claim 1, comprising the steps of: irradiating the object with the inspection light and acquiring an image of the object with the imaging device; irradiating the object with a first inspection light which is monochromatic light and acquiring an image of the object with the imaging device; further irradiating the object with a second inspection light to which the color distribution has been imparted and acquiring an image of the object with the imaging device; color calibrating the image acquired by irradiating the object with the second inspection light using the image acquired by irradiating the object with the first inspection light; and calculating the inclination angle of the surface of the object based on the image after color calibration, 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.

16. A method for correcting the inclination angle of the surface of an object using the inspection system described in claim 1, comprising: 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 setting a reference plane on the surface of the object; a third step of calculating an offset based on the image of the reference plane; and a fourth step of correcting the inclination angle by subtracting the offset calculated in the third step from the inclination angle at each part of the surface of the object obtained in the first step, wherein the offset corresponds to the inclination of the object relative to the inspection system.

17. A method for highlighting features of an image of an object obtained using the inspection system described in claim 11, comprising at least the following steps: 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; and a third step of determining a difference between the image of the object obtained in the first step and the image of the object obtained in the second step, and highlighting a characteristic portion of the object based on the image after the difference.

18. A method for highlighting a feature of an image of an object as described in claim 17, wherein in the second step, a position or area or both the position and area of ​​the light-emitting region of the surface light source is changed to obtain a plurality of images of the object, and in the third step, a difference is calculated between the image of the object obtained in the first step and the plurality of images of the object obtained in the second step, and a feature portion of the object is highlighted based on the images after the difference.

Images