Inspection System and Inspection Method

Abstract

To provide an inspection system which can perform inspection using a plurality of images differing in lighting condition, on moving objects.SOLUTION: The inspection system comprises: a plurality of lighting units for lighting an object; a polarization camera in which unit regions including a plurality of polarizers are repeatedly arrayed; and an inspection device. The plurality of lighting units radiate illumination light in mutually different states of polarization. The plurality of polarizers transmit light in mutually different directions of polarization. The polarization camera takes a picture while the plurality of lighting units are simultaneously lighted and thereby outputs a plurality of polarized images corresponding to the plurality of polarizers, respectively. The inspection device inspects the object using the plurality of polarized images.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an inspection system and an inspection method.

Background Art

[0002] In the field of FA (Factory Automation) etc., an object is imaged while being illuminated, and the appearance of the object is inspected using the obtained image. Conventionally, in order to improve inspection performance, a method of changing the illumination conditions and imaging a plurality of times is known.

[0003]

[0004] For example, in the photometric stereo method, the normal of the surface of an object is estimated using a plurality of images obtained by imaging a plurality of times while changing the direction of a light source. Thereby, the unevenness of the surface is inspected without being affected by the dirt on the surface of the object.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] When the object is moving, in the above - described conventional method, the positions of the object in the plurality of images respectively obtained by imaging a plurality of times are different from each other. Therefore, the above - described conventional method cannot be applied to a moving object.

[0007] ​The present disclosure has been made in view of the above problems, and an object thereof is to provide an inspection system and an inspection method capable of inspecting a moving object using a plurality of images with different illumination conditions.

Means for Solving the Problems

[0008] According to an example of the present disclosure, the inspection system includes a plurality of illumination units that illuminate an object, a polarization camera in which a unit region including a plurality of polarizers is repeatedly arranged, and an inspection device. The plurality of illumination units irradiate illumination light with different polarization states. The plurality of polarizers transmit light with different polarization directions. The polarization camera outputs a plurality of polarization images respectively corresponding to the plurality of polarizers by imaging in a state where the plurality of illumination units are simultaneously lit. The inspection device inspects the object using the plurality of polarization images.

[0009] According to the above disclosure, each of the plurality of polarization images corresponds to an image captured under an illumination condition mainly based on the illumination condition of the illumination unit that irradiates the polarization with the smallest angle formed with the polarization direction of the corresponding polarizer. That is, a plurality of polarization images corresponding to a plurality of illumination conditions are acquired by one-shot imaging. Therefore, it is possible to inspect a moving object using a plurality of polarization images with different illumination conditions.

[0010] In the above disclosure, the plurality of illumination units are arranged such that the azimuth angles around the optical axis of the polarization camera are different from each other. The plurality of illumination units include first to Nth illumination units. The plurality of polarizers include first to Nth polarizers. N is an integer of 2 or more. The polarization directions of the illumination lights of the first to Nth illumination units are respectively parallel to the polarization directions of the lights transmitted through the first to Nth polarizers. The inspection device generates a normal image indicating the normal direction of the surface of the object from the plurality of polarization images, and inspects the object based on the normal image.

[0011] According to the above disclosure, for each of the first to Nth polarizers, the polarized light image corresponding to the polarizer is captured such that the light of the illumination unit that irradiates illumination light parallel to the polarization direction of the polarizer is the strongest. That is, among the first to Nth illumination units, the illumination unit that has the greatest influence on the polarized light image is different for each of the plurality of polarized light images. The first to Nth illumination units are arranged such that the azimuth angles around the optical axis of the polarized light camera are different from each other. Therefore, a plurality of polarized light images with different conditions regarding the azimuth angle of the illumination light can be obtained in a single imaging. Then, a normal image is generated from the plurality of polarized light images. By using the normal image, the unevenness of the surface of the object can be accurately inspected.

[0012] In the above disclosure, N is 4. The first illumination unit and the third illumination unit are arranged at positions symmetric with respect to the optical axis of the polarized light camera. The second illumination unit and the fourth illumination unit are arranged at positions symmetric with respect to the optical axis of the polarized light camera. Around the optical axis of the polarized light camera, the difference between the first azimuth angle at which the first illumination unit is arranged and the second azimuth angle at which the second illumination unit is arranged is 90°. The plurality of polarized light images include the first to fourth polarized light images corresponding to the first to fourth polarizers respectively. The inspection device generates a first normal image indicating the magnitude of the component along the direction of the first azimuth angle in the normal vector of the surface of the object based on the first to fourth polarized light images. The inspection device generates a second normal image indicating the magnitude of the component along the direction of the second azimuth angle in the normal vector of the surface of the object based on the first to fourth polarized light images. The inspection device generates a shape image indicating the shape of the surface of the object based on the first normal image and the second normal image, and inspects the object based on the shape image.

[0013] According to the above disclosure, a first normal image indicating the magnitude of the component along the direction of the first azimuth angle and a second normal image indicating the magnitude of the component along the direction of the second azimuth angle are generated. Thereby, even if the formation direction of scratches on the surface of the object is random, for example, a change in shape corresponding to the scratches appears in the shape image. Therefore, the scratches on the surface of the object can be accurately inspected.

[0014] In the above disclosure, the angles formed by the polarization directions of the illumination lights of the second, third, and fourth illumination units and the polarization direction of the illumination light of the first illumination unit are 45°, 90°, and 135°, respectively.

[0015] According to the above disclosure, the first to fourth polarization images respectively correspond to the images captured under the illumination conditions mainly based on the illumination conditions of the first to fourth illumination units. And the influence of the illumination light of the third illumination unit on the first polarization image can be minimized. Similarly, the influence of the illumination lights of the fourth, first, and second illumination units on the second, third, and fourth polarization images can be minimized respectively.

[0016] In the above disclosure, the plurality of illumination units are arranged such that the elevation angles with respect to the object are different from each other.

[0017] According to the above disclosure, a plurality of polarization images with different elevation angles with respect to the object as illumination conditions can be obtained in one imaging.

[0018] In the above disclosure, the plurality of illumination units include a first illumination unit that irradiates illumination light along the optical axis of the polarization camera, and a ring-shaped second illumination unit centered on the optical axis of the polarization camera. The plurality of polarizers include a first polarizer and a second polarizer. The polarization directions of the illumination lights irradiated from the first illumination unit and the second illumination unit respectively coincide with the polarization directions of the lights transmitted through the first polarizer and the second polarizer.

[0019] According to the above disclosure, the first polarization image corresponding to the first polarizer shows the luminance of the light that is irradiated from the first illumination unit and is specularly reflected on the surface of the object. That is, the first polarization image corresponds to the image obtained under the conditions of bright-field illumination. In the image obtained under the conditions of bright-field illumination, the luminance of the part where there are scratches decreases. Therefore, by using the first polarization image, scratches can be inspected with high accuracy.

[0020] The second polarization image corresponding to the second polarizer is irradiated from the second illumination unit and shows the luminance of the light diffusely reflected on the surface of the object. That is, the second polarization image corresponds to an image obtained under the conditions of dark-field illumination. In an image obtained under the conditions of dark-field illumination, the luminance of the portion where dirt exists is different from the luminance of its surroundings. Therefore, by using the second polarization image, dirt can be inspected with high accuracy.

[0021] In this way, the first polarization image suitable for inspection of scratches and the second polarization image suitable for inspection of dirt are acquired by one imaging.

[0022] In the above disclosure, the plurality of illumination units include a plurality of ring-shaped illumination units in a concentric circle centered on the optical axis of the polarization camera. The inspection apparatus generates a phase image showing the angle formed by the normal direction of the surface of the object and the optical axis direction of the polarization camera based on the plurality of polarization images. Based on the phase image, the object is inspected.

[0023] According to the above disclosure, since the polarization states of the illumination lights of the plurality of ring-shaped illumination units are different from each other, the amounts of light irradiated from the plurality of ring-shaped illumination units, specularly reflected on the surface of the object, and transmitted through each polarizer are different from each other. Therefore, stripe patterns with different phases from each other are imaged in the plurality of polarization images. That is, a plurality of polarization images in which stripe patterns with different phases from each other are imaged are obtained by one imaging. And the phase image generated from the plurality of polarization images indicates the normal direction of the surface of the object. Therefore, by using the phase image, the unevenness of the surface of the object is inspected with high accuracy.

[0024] In the above disclosure, the plurality of illumination units further include an illumination unit that irradiates illumination light along the optical axis of the polarization camera.

[0025] According to the above disclosure, it is possible to reduce the loss of the stripe pattern regarding the central portion of the concentric circle and perform a more accurate inspection.

[0026] In the above disclosure, the plurality of illumination units include a first illumination unit that irradiates illumination light along the optical axis of the polarization camera, and a second illumination unit that irradiates illumination light from the back side of the object. The plurality of polarizers include a first polarizer and a second polarizer. The polarization directions of the illumination light irradiated from the first illumination unit and the second illumination unit respectively coincide with the polarization directions of the light transmitted through the first polarizer and the second polarizer.

[0027] According to the above disclosure, the first polarization image corresponding to the first polarizer shows the luminance of the light that is irradiated from the first illumination unit and is specularly reflected on the surface of the object. When light is incident on a portion where there is a scratch, it is diffusely reflected. Therefore, in the first polarization image, the luminance of the portion where there is a scratch decreases. Thus, by using the first polarization image, scratches can be accurately inspected.

[0028] The second polarization image corresponding to the second polarizer shows the luminance of the light that is irradiated from the second illumination unit and is incident on the polarization camera. Therefore, when the object has light-shielding properties, the shape of the outer periphery of the object is clearly recognized in the second polarization image. Thus, by using the second polarization image, burrs or chips on the outer periphery of the object can be accurately inspected.

[0029] In this way, the first polarization image suitable for inspecting scratches and the second polarization image suitable for inspecting burrs or chips on the outer periphery of the object are obtained by a single imaging.

[0030] In the above disclosure, the plurality of illumination units include a first illumination unit that irradiates linearly polarized illumination light and a second illumination unit that irradiates non-polarized light. The plurality of polarizers include a first to a third polarizer. The first polarizer transmits light having the same polarization direction as the polarization direction of the illumination light of the first illumination unit. The second polarizer transmits light having a polarization direction at an angle of 45° with the polarization direction of the light transmitted through the first polarizer. The third polarizer transmits light having a polarization direction at an angle of 90° with the polarization direction of the light transmitted through the first polarizer. The plurality of polarized images include first to third polarized images respectively corresponding to the first to third polarizers. The inspection device synthesizes the first to third polarized images with a high dynamic range to generate a synthesized image, and inspects the object based on the synthesized image.

[0031] According to the above disclosure, the non-polarized light irradiated from the second illumination unit uniformly passes through the first to third polarizers. On the other hand, the linearly polarized light irradiated from the first illumination unit passes through the first polarizer but does not pass through the third polarizer. Also, the intensity of the light irradiated from the first illumination unit and transmitted through the second polarizer is 1 / 2 of the intensity of the light irradiated from the first illumination unit and transmitted through the first polarizer. Therefore, the first to third polarized images correspond to a plurality of images captured under illumination conditions with different illumination intensities. That is, the first to third polarized images with different illumination intensities are obtained in one imaging. Then, the first to third polarized images are synthesized with a high dynamic range to generate a synthesized image. By using the synthesized image, the inspection accuracy of the object is improved.

[0032] According to an example of the present disclosure, the inspection method uses a plurality of illumination units for illuminating an object and a polarization camera in which a unit region including a plurality of polarizers is repeatedly arranged. The plurality of illumination units irradiate illumination light with different polarization states. The plurality of polarizers transmit light with different polarization directions. The inspection method includes the steps of acquiring a plurality of polarized images respectively corresponding to the plurality of polarizers by imaging the object using the polarization camera in a state where the plurality of illumination units are simultaneously lit, and inspecting the object using the plurality of polarized images.

[0033] According to the above disclosure, it is also possible to inspect a moving object using a plurality of images with different lighting conditions.

Advantages of the Invention

[0034] According to the present disclosure, it is possible to inspect a moving object using a plurality of images with different lighting conditions.

Brief Description of the Drawings

[0035]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Figure 25

Figure 26

Figure 27

Figure 28

Figure 29

Figure 30

Figure 31

Figure 32

Figure 33

Figure 34

Figure 35

Embodiments for Carrying Out the Invention

[0036] Embodiments of the present invention will be described in detail with reference to the drawings. For the same or corresponding parts in the drawings, the same reference numerals are given and the description thereof will not be repeated.

[0037] §1 Application Example With reference to FIGS. 1 and 2, an application example of the present invention will be described. FIG. 1 is a schematic diagram showing the overall configuration of an inspection system 1 according to the present embodiment. The inspection system 1 inspects the object W using an image obtained by imaging the object W. The object W has a glossy surface such as metal or glass, that is, a surface on which incident light is mainly specularly reflected. The inspection system 1 is incorporated, for example, in a production line and inspects whether there are defects in the object W moving on the conveyor belt 2.

[0038] Defects include scratches, unevenness, dirt, dust adhesion, burrs, chips, etc. In order to accurately inspect the presence or absence of defects, it is necessary to make the defective parts conspicuous in the image. Depending on the type of defect, the lighting conditions for making the defective parts conspicuous are different. Therefore, when it is desired to inspect multiple types of defects, a plurality of images captured under multiple lighting conditions are required. Alternatively, in an image obtained by synthesizing a plurality of images captured under multiple lighting conditions, the defective parts may be conspicuous. Even in such a case where it is desired to inspect such defects, a plurality of images captured under multiple lighting conditions are required. The inspection system 1 shown in FIG. 1 acquires a plurality of images corresponding to a plurality of lighting conditions for the moving object W by a single imaging (one-shot imaging), and inspects the object W using the acquired plurality of images.

[0039] As shown in FIG. 1, the inspection system 1 includes a plurality of lighting units 10 that illuminate the object W, a polarization camera 20, and an inspection device 30.

[0040] The plurality of lighting units 10 irradiate illumination light with different polarization states. The inspection system 1 shown in FIG. 1 includes lighting units 10a, 10b, 10c, 10d, ···. Hereinafter, when the lighting units 10a, 10b, 10c, 10d, ··· are not particularly distinguished, each of the lighting units 10a, 10b, 10c, 10d, ··· will be referred to as "lighting unit 10".

[0041] Typically, each of the plurality of lighting units 10 includes a light-emitting unit that emits non-polarized light and a linear polarization filter disposed between the light-emitting unit and the object W. The polarization directions of the light transmitted through the linear polarization filters are different from each other in the plurality of lighting units 10. Note that one of the plurality of lighting units 10 may not include a linear polarization filter. In this case, one lighting unit 10 irradiates the object W with non-polarized light.

[0042] The polarization camera 20 has a plurality of light detection sensors arranged in a matrix, and generates image data (hereinafter simply referred to as "image") using the amount of received light (luminance) detected by the light detection sensors as pixel values. The sizes of the plurality of light detection sensors are the same. The light detection sensors are, for example, CCD (Coupled Charged Device) or CMOS (Complementary Metal Oxide Semiconductor) sensors. A polarizer is provided on the light incident side of each light detection sensor.

[0043] FIG. 2 is a diagram showing an example of the arrangement of the polarizers included in the polarization camera 20. As shown in FIG. 2, in the polarization camera 20, unit regions 21 each including a plurality of polarizers 22 are repeatedly arranged. The plurality of unit regions 21 are arranged in a matrix. The sizes of the plurality of polarizers 22 are the same.

[0044] In the polarization camera 20 illustrated in FIG. 2, the unit region 21 includes, as the plurality of polarizers 22, four polarizers 22a to 22d that respectively overlap with four light detection sensors. Hereinafter, when the polarizers 22a to 22d are not particularly distinguished, each of the polarizers 22a to 22d is described as "polarizer 22".

[0045] Each of the polarizers 22a to 22d transmits linearly polarized light in a predetermined polarization direction. Taking the polarization direction of the polarizer 22a as the reference direction and the angle formed by the reference direction and the polarization direction as the polarization angle, the polarization angles of the polarizers 22a to 22d are 0°, 45°, 90°, and 135°, respectively. Note that the polarization angle may include manufacturing errors, mounting errors, etc. For example, when the maximum of the total of manufacturing errors and mounting errors is β°, "polarization angle 45°" includes the range of 45° ± β°.

[0046] The polarization camera 20 outputs a plurality of polarization images 50 (see FIG. 1) corresponding to the plurality of polarizers 22 by imaging while a plurality of illumination units 10 are lit simultaneously. In the inspection system 1 shown in FIG. 1, the plurality of polarization images 50 include polarization images 50a, 50b, 50c, 50d, ···. Hereinafter, when the polarization images 50a, 50b, 50c, 50d, ··· are not particularly distinguished, each of the polarization images 50a, 50b, 50c, 50d, ··· is described as "polarization image 50".

[0047] The pixel value of each of the plurality of polarization images 50 indicates the luminance of the light transmitted through the corresponding polarizer 22 among the plurality of polarizers 22. For example, when the polarization camera 20 has the configuration shown in FIG. 2, polarization images 50a, 50b, 50c, 50d corresponding to the polarizers 22a to 22d are output.

[0048] The inspection device 30 inspects the object W using the plurality of polarization images 50 received from the polarization camera 20.

[0049] Each of the plurality of polarizers 22 transmits more of the illumination light from the illumination unit 10 that irradiates linearly polarized light with the smallest angle formed with the polarization direction of the polarizer 22 among the plurality of illumination units 10.

[0050] For example, the case where the polarization direction of the polarizer 22a and the polarization direction of the illumination unit 10a are parallel, and the polarization direction of the polarizer 22c and the polarization direction of the illumination unit 10c are parallel will be described. As shown in FIG. 2, the polarization directions of the polarizers 22a and 22c are orthogonal to each other. In this case, the light irradiated from the illumination unit 10a and specularly reflected on the surface of the object W passes through the polarizer 22a but does not pass through the polarizer 22c. On the other hand, the light irradiated from the illumination unit 10c and specularly reflected on the surface of the object W does not pass through the polarizer 22a but passes through the polarizer 22c. Therefore, in the polarization image 50a corresponding to the polarizer 22a, imaging is performed so that the light of the illumination unit 10a is the strongest. In the polarization image 50c corresponding to the polarizer 22c, imaging is performed so that the light of the illumination unit 10c is the strongest.

[0051] Thus, each of the plurality of polarized images 50 is imaged such that the light from the illumination unit 10 that irradiates linearly polarized light with the smallest angle with respect to the polarization direction of the corresponding polarizer 22 becomes the strongest. That is, by one-shot imaging, a plurality of polarized images 50 respectively corresponding to a plurality of illumination conditions are acquired. Therefore, it is possible to inspect the moving object W using a plurality of polarized images 50 with different illumination conditions.

[0052] §2 Specific Example <A. Hardware Configuration of the Inspection Device> FIG. 3 is a schematic diagram showing the hardware configuration of the inspection device. As shown in FIG. 3, the inspection device 30 typically has a structure according to a general-purpose computer architecture, and various processes as described later are realized by the processor executing a pre-installed program.

[0053] More specifically, the inspection device 30 includes a processor 310 such as a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit), a RAM (Random Access Memory) 312, a display controller 314, a system controller 316, an I / O (Input Output) controller 318, a hard disk 320, a camera interface 322, an input interface 324, a communication interface 328, and a memory card interface 330. These components are connected to be able to communicate data with each other around the system controller 316.

[0054] The processor 310 exchanges programs (codes) etc. with the system controller 316 and executes them in a predetermined order to realize the target arithmetic processing.

[0055] The system controller 316 is connected to the processor 310, the RAM 312, the display controller 314, and the I / O controller 318 via buses respectively, exchanges data etc. with each component, and controls the processing of the entire inspection device 30.

[0056] The RAM 312 is typically a volatile memory device such as a DRAM (Dynamic Random Access Memory), and holds programs read from the hard disk 320, polarization images 50 acquired by the polarization camera 20, processing results for the polarization images 50, and the like.

[0057] The display controller 314 is connected to the display unit 302, and outputs signals for displaying various information to the display unit 302 according to internal commands from the system controller 316. The display unit 302 includes, for example, a liquid crystal display, an organic EL (Electro Luminescence) display, organic EL, and the like.

[0058] The I / O controller 318 controls data exchange between the recording medium and external devices connected to the inspection apparatus 30. More specifically, the I / O controller 318 is connected to the hard disk 320, the camera interface 322, the input interface 324, the communication interface 328, and the memory card interface 330.

[0059] The hard disk 320 is typically a non-volatile magnetic storage device and stores the inspection program 350 executed by the processor 310. The inspection program 350 installed on this hard disk 320 is distributed in a state stored in a memory card 306 or the like. Further, camera images are stored in the hard disk 320. Note that instead of the hard disk 320, a semiconductor storage device such as a flash memory or an optical storage device such as a DVD-RAM (Digital Versatile Disk Random Access Memory) may be employed.

[0060] The camera interface 322 corresponds to an input unit that receives the polarization image 50 generated by imaging the object W, and mediates data transmission between the processor 310 and the polarization camera 20. More specifically, the camera interface 322 can be connected to the polarization camera 20, and an imaging instruction is output from the processor 310 to the polarization camera 20 via the camera interface 322. Thereby, the polarization camera 20 images the object W and outputs a plurality of generated polarization images 50 to the processor 310 via the camera interface 322.

[0061] The input interface 324 mediates data transmission between the processor 310 and input devices such as the keyboard 304, mouse, touch panel, dedicated console, etc. That is, the input interface 324 receives an operation command given by the user operating the input device.

[0062] The communication interface 328 mediates data transmission between the processor 310 and other personal computers or server devices (not shown). The communication interface 328 typically consists of Ethernet (registered trademark), USB (Universal Serial Bus), etc. Note that, as will be described later, instead of installing the program stored in the memory card 306 in the inspection device 30, a program downloaded from a distribution server or the like may be installed in the inspection device 30 via the communication interface 328.

[0063] The memory card interface 330 mediates data transmission between the processor 310 and the memory card 306 which is a recording medium. That is, the memory card 306 circulates with inspection programs 350 and the like executed by the inspection device 30 stored therein, and the memory card interface 330 reads the inspection program 350 from this memory card 306. Note that the memory card 306 includes general-purpose semiconductor memory devices such as SD (Secure Digital), magnetic recording media such as Flexible Disks, and optical recording media such as CD-ROM (Compact Disk Read Only Memory).

[0064] <B. Inspection Examples> As described above, the optimal illumination conditions differ according to the type of defect to be inspected. Therefore, according to the type of defect to be inspected, the positions, illumination intensities, polarization directions, etc. of the plurality of illumination units 10 are appropriately set. Hereinafter, the first to fifth inspection examples using the inspection system 1 according to the present embodiment will be described. Note that the inspection system 1 is not limited to the following first to fifth inspection examples and may be used in other inspection examples.

[0065] (B-1. First Inspection Example) The first inspection example uses the photometric stereo method (illuminance difference stereo method). The photometric stereo method is a technique for estimating the inclination (normal vector) of the surface of an object using a plurality of images obtained under conditions where the incident directions of illumination light are different.

[0066] FIG. 4 is a diagram showing an example of a conventional illumination device used in the photometric stereo method. As shown in FIG. 4, four arc regions 110a to 110d of the ring-shaped illumination device 110 are sequentially lit and imaged using a non-polarizing camera. The center of the illumination device 110 is located on the optical axis 225 of the non-polarizing camera.

[0067] Specifically, the first imaging is performed with only the arc region 110a lit. Next, the second imaging is performed with only the arc region 110b lit. Next, the third imaging is performed with only the arc region 110c lit. Next, the fourth imaging is performed with only the arc region 110d lit. As a result, four images obtained under conditions where the incident directions of the illumination light are different are obtained. However, since the imaging is performed four times, the illumination device 110 shown in FIG. 4 cannot be applied to the moving object W. Therefore, in the first inspection example, the inspection system 1 according to the present embodiment acquires a plurality of images used in the photometric stereo method by one-shot imaging.

[0068] (Arrangement of illumination units) FIG. 5 is a diagram showing the arrangement of a plurality of illumination units according to the first inspection example. As shown in FIG. 5, the plurality of illumination units 10 include illumination units 10a to 10d.

[0069] The illumination units 10a and 10c are arranged at positions symmetric with respect to the optical axis 25 of the polarization camera 20. The illumination units 10b and 10d are arranged at positions symmetric with respect to the optical axis 25 of the polarization camera 20. Around the optical axis 25 of the polarization camera 20, the difference between the azimuth angle at which the illumination unit 10a is arranged and the azimuth angle at which the illumination unit 10b is arranged is 90°. Hereinafter, with respect to the optical axis 25 of the polarization camera 20, the direction of the azimuth in which the illumination unit 10a is arranged is defined as the X direction, and the direction of the azimuth in which the illumination unit 10b is arranged is defined as the Y direction.

[0070] The illumination units 10a to 10d each have light emitting units 11a to 11d and linear polarization filters 12a to 12d.

[0071] The light emitting parts 11a to 11d emit non-polarized light. Each of the light emitting parts 11a to 11d is in an arc shape with a central angle of 90°. The arc-shaped light emitting parts 11a to 11d are arranged such that their centers coincide and they do not overlap with each other. Specifically, one end of each of the light emitting parts 11a to 11d is in contact with the other ends of the light emitting parts 11b to 11d and 11a, respectively. That is, when the light emitting parts 11a to 11d are combined, one ring-shaped illumination is formed. In other words, the light emitting parts 11a to 11d are four arc regions with a central angle of 90° in one ring-shaped illumination. Note that the centers of the arc-shaped light emitting parts 11a to 11d are located on the optical axis 25 of the polarization camera 20.

[0072] The linear polarization filters 12a to 12d are respectively attached to the light emitting surfaces of the light emitting parts 11a to 11d.

[0073] FIG. 6 is a diagram showing an example of the polarization directions of the linear polarization filters 12a to 12d. Taking the polarization direction of the light transmitted through the linear polarization filter 12a as the reference direction and the angle formed by the reference direction and the polarization direction as the polarization angle, the polarization angles of the linear polarization filters 12a to 12d are 0°, 45°, 90°, and 135°, respectively. Note that the polarization angle may include manufacturing errors, mounting errors, etc. For example, when the maximum of the total of manufacturing errors and mounting errors is β°, "polarization angle 45°" includes the range of 45° ± β°. Thus, the angles formed by the polarization directions of the illumination light of the illumination parts 10b to 10d and the polarization direction of the illumination light of the illumination part 10a are 45°, 90°, and 135°, respectively.

[0074] In the first inspection example, the inspection system 1 includes a polarization camera 20 including polarizers 22a to 22d shown in FIG. 2. The polarization directions of the polarizers 22a to 22d are respectively parallel to the polarization directions of the linear polarization filters 12a to 12d. Therefore, the light irradiated from the illumination units 10a to 10d and specularly reflected by the object W passes through the polarizers 22a to 22d respectively. The light irradiated from the illumination unit 10a has components parallel to the polarization directions of the polarizers 22b and 22d. Therefore, some of the components of the light irradiated from the illumination unit 10a and specularly reflected by the object W pass through the polarizers 22b and 22d. Specifically, the amount of light irradiated from the illumination unit 10a and passing through each of the polarizers 22b and 22d is about 1 / 2 of the amount of light irradiated from the illumination unit 10a and passing through the polarizer 22a. Similarly, some of the components of the light irradiated from the illumination unit 10b and specularly reflected by the object W pass through the polarizers 22a and 22c. Some of the components of the light irradiated from the illumination unit 10c and specularly reflected by the object W pass through the polarizers 22b and 22d. Some of the components of the light irradiated from the illumination unit 10d and specularly reflected by the object W pass through the polarizers 22a and 22c.

[0075] (Flow of inspection process) FIG. 7 is a flowchart showing an example of the flow of the inspection process in the first inspection example. First, the polarization camera 20 images the object W in a state where the illumination units 10a to 10d are simultaneously lit, and outputs polarization images 50a to 50d corresponding to the polarizers 22a to 22d respectively (step S1). After step S1, the inspection system 1 starts steps S2, S3, and S10 in parallel.

[0076] In step S2, the processor 310 of the inspection device 30 generates an X-direction normal image showing the magnitude of the component along the X direction in the normal vector of the surface of the object W using the polarization images 50a to 50d. Similarly, in step S3, the processor 310 generates a Y-direction normal image showing the magnitude of the Y-direction component in the normal vector of the surface of the object W using the polarization images 50a to 50d. Details of the generation method of the X-direction normal image and the X-direction normal image will be described later.

[0077] After steps S2 and S3, steps S4 and S5 are respectively performed. In steps S2 and S3, as will be described later, assuming that the glossiness α of the surface of the object W is 1, an X-direction normal image and a Y-direction normal image are generated. However, the glossiness α of the surface of the object W is not necessarily 1. Depending on the glossiness α, the ratio of the specularly reflected component of the incident light is different. Therefore, in step S4, the processor 310 corrects the X-direction normal image according to the glossiness α of the surface of the object W. In step S5, the processor 310 corrects the Y-direction normal image according to the glossiness α of the surface of the object W. Details of the correction methods for the X-direction normal image and the Y-direction normal image will be described later.

[0078] After steps S4 and S5, the processor 310 starts steps S6 and S8 in parallel.

[0079] In step S6, the processor 310 generates a shape image indicating the shape of the surface of the object W based on the X-direction normal image and the Y-direction normal image. Details of the method for generating the shape image will be described later.

[0080] Next, in step S7, the processor 310 inspects the surface of the object W based on the shape image. For example, the processor 310 inspects the presence or absence of defects with unevenness such as scratches and dents. Note that the processor 310 may generate a binary image by binarizing the shape image in step S7 and inspect the presence or absence of defects based on the binary image.

[0081] In step S8, the processor 310 generates an albedo image indicating the ratio (albedo (reflectance)) of the specularly reflected light in the incident light. The albedo image is generated using the polarization images 50a to 50d and the X-direction normal image and the Y-direction normal image respectively corrected in steps S4 and S5. Details of the method for generating the albedo image will be described later.

[0082] Next, in step S9, the processor 310 inspects the surface of the object W based on the albedo image. For example, the processor 310 inspects the presence or absence of defects that cause changes in the albedo such as dirt. Note that the processor 310 may generate a binary image by binarizing the albedo image in step S9 and inspect the presence or absence of defects based on the binary image.

[0083] In step S10, the processor 310 generates an average image by averaging the polarization images 50a to 50d. The value of each pixel of the average image is the average value of the values of the corresponding pixel of the polarization images 50a to 50d. The average image corresponds to an image obtained by simultaneously lighting the light emitting units 11a to 11d with the linear polarization filters 12a to 12d removed and imaging using a non-polarization camera instead of the polarization camera 20.

[0084] Next, in step S11, the processor 310 performs positioning of the object W and the like using the average image.

[0085] After the completion of steps S7, S9, and S11, the processor 310 causes the inspection result to be displayed on the display unit 302 (step S12). After step S12, the processor 310 ends the inspection process.

[0086] (X-direction normal image and method for generating X-direction normal image) FIG. 8 is a diagram showing the relationship between the lighting units 10a to 10d and the normal vector n at a point P on the surface of the object W. In FIG. 8, the optical axis 25 of the polarization camera 20 coincides with the Z axis. The normal vector n is represented by (nx, ny, nz). nx, ny, and nz are the X component, Y component, and Z component of the normal vector n, respectively.

[0087] FIG. 9 is a diagram showing the relationship between the traveling direction of the light irradiated from the lighting unit 10c and the normal direction of the point P when projected onto the XZ plane. In FIG. 9, the normal direction is represented by the vector (nx, nz). Let the angle formed by the normal direction and the Z axis be φx, then φx is represented by the following equation. φx = arctan(nx / nz) Furthermore, assuming that the incident angle of the light irradiated from each of the illumination units 10a to 10d is θ, nx > 0, and nz > 0, the angle formed by the projection component of the traveling direction (specular reflection direction) of the light irradiated from the illumination unit 10c and specularly reflected at point P onto the XZ plane and the Z-axis is θ + 2φx.

[0088] FIG. 10 is a diagram showing the relationship between the traveling direction of the light irradiated from the illumination unit 10c and the normal direction of point P when projected onto the YZ plane. In FIG. 10, the normal direction is represented by the vector (ny, nz). Assuming that the angle formed by the normal direction and the Z-axis is φy, φy is represented by the following equation. φx = arctan(ny / nz) Furthermore, assuming that the incident angle of the light irradiated from the illumination unit 10c is θ, ny > 0, and nz > 0, the angle formed by the projection component of the traveling direction (specular reflection direction) of the light irradiated from the illumination unit 10c and specularly reflected at point P onto the YZ plane and the Z-axis is 2φy.

[0089] Similarly, the angles formed by the projection components of the traveling directions (specular reflection directions) of the light irradiated from the illumination units 10a, 10b, and 10d and specularly reflected at point P onto the XZ plane and the Z-axis are θ - 2φx, 2φx, and 2φx, respectively. The angles formed by the projection components of the traveling directions (specular reflection directions) of the light irradiated from the illumination units 10a, 10b, and 10d and specularly reflected at point P onto the YZ plane and the Z-axis are 2φy, θ - 2φy, and θ + 2φy, respectively.

[0090] The intensities Ia to Id of the light incident on the polarization camera 20, respectively, among the light irradiated from the illumination units 10a to 10d and specularly reflected at point P are approximated by the following equations using the Phong reflection model. Ia = μ[cos α (θ - 2φx)cos α (2φy)] Ib = μ[cos α (2φx)cos α (θ - 2φy)] Ic = μ[cos α (θ + 2φx)cos α (2φy)] Id = μ[cos α (2φx)cos α (θ + 2φy)] In the above formula, α represents the glossiness. μ represents the albedo (reflectivity) of the surface of the object W.

[0091] As described above, the polarization direction of the polarizer 22a of the polarization camera 20 is parallel to the polarization direction of the illumination unit 10a and perpendicular to the polarization direction of the illumination unit 10c. Further, the angle formed by the polarization direction of the polarizer 22a and the polarization directions of the illumination units 10b and 10d is 45°. Therefore, if the pixel value of the polarization image 50a corresponding to the polarizer 22a is Ja, Ja = Ia + (Ib + Id) / 2 is represented by. Similarly, the pixel values Jb to Jd of the polarization images 50b to 50d are Jb = Ib + (Ia + Ic) / 2 Jc = Ic + (Id + Ib) / 2 Jd = Id + (Ic + Ia) / 2 is represented by.

[0092] When the glossiness α = 1, the following formulas (1) to (3) hold. Ja + Jb + Jc + Jd = 2(Ia + Ib + Ic + Id) = 8μcos(θ)cos(2φx)cos(2φy) ··· Formula (1) Ja - Jc = Ia - Ic = 2μsin(θ)sin(2φx)cos(2φy) ··· Formula (2) Jb - Jd = Ib - Id = 2μsin(θ)cos(2φx)sin(2φy) ··· Formula (3).

[0093] From the above formulas (1) and (2), the following formula (4) is derived. Similarly, from the above formulas (1) and (3), the following formula (5) is derived. tan(2φx) = {4(Ja - Jc)} / {(Ja + Jb + Jc + Jd)tan(θ)} ··· Formula (4) tan(2φy) = {4(Jb - Jd)} / {(Ja + Jb + Jc + Jd)tan(θ)} ··· Formula (5).

[0094] In Equations (4) and (5), the incident angle θ is determined in advance according to the positions of the illumination units 10a to 10d. Therefore, the processor 310 calculates the right side of Equation (4) using the pixel values of the polarization images 50b to 50d and the incident angle θ, and generates an X-direction normal image with the result Nx as the pixel value. Similarly, the processor 310 calculates the right side of Equation (5) using the pixel values of the polarization images 50b to 50d and the incident angle θ, and generates a Y-direction normal image with the result Ny as the pixel value. Tan(2φx) (≡Nx) represented by Equation (4) is a value that depends on nx, which is the x-direction component of the normal vector. Tan(2φy) (≡Ny) represented by Equation (5) is a value that depends on ny, which is the y-direction component of the normal vector. Therefore, the X-direction normal image and the Y-direction normal image represent the normal direction of the surface of the object W.

[0095] (Method for correcting X-direction normal image and Y-direction normal image) The X-direction normal image and the Y-direction normal image are respectively generated according to Equations (4) and (5) assuming that the glossiness α of the surface of the object W is 1. Therefore, correction of the X-direction normal image and the Y-direction normal image is performed according to the glossiness α of the object W. Thereby, a normal image corresponding to the glossiness α is generated with high accuracy.

[0096] The glossiness α of the object W is determined in advance according to the following pre-inspection procedure. In the pre-inspection procedure, a defect-free object W is placed on a two-axis goniometric stage. The two-axis goniometric stage is a stage that can be tilted in the X direction and the Y direction.

[0097] When the tilt angles in the X direction and the Y direction of the two-axis goniometric stage are set to 0°, the object W is placed on the two-axis goniometric stage so as to have a region where the upper surface is horizontal and flat (hereinafter referred to as the "target region"). Therefore, the angle φx formed by the X-direction component of the normal vector of the target region and the Z axis coincides with the tilt angle in the X direction of the two-axis goniometric stage. Similarly, the angle φy formed by the Y-direction component of the normal vector of the target region and the Z axis coincides with the tilt angle in the Y direction of the two-axis goniometric stage.

[0098] While changing the tilt angles in the X and Y directions of the two-axis goniostage, perform M imaging operations using the inspection system 1. For each of the M imaging operations, generate an X-direction normal image and a Y-direction normal image. For any one pixel within the target region in the X-direction normal image and the Y-direction normal image, the processor 310 stores the data set [φxm, φym, Nxm, Nym] in the RAM 312. Here, m indicates the imaging number and is an integer between 1 and M. φxm is the tilt angle in the X direction of the two-axis goniostage in the m-th imaging operation. φym is the tilt angle in the Y direction of the two-axis goniostage in the m-th imaging operation. Nxm is the pixel value of the X-direction normal image. Nym is the pixel value of the Y-direction normal image.

[0099] The processor 310 determines the glossiness α that best fits the data set [φxm, φym, Nxm, Nym] stored in the RAM 312 using the following theoretical formula. <<Theoretical formula>> Ia = cos α (θ - 2φxm)cos α (2φym) Ib = cos α (2φxm)cos α (θ - 2φym) Ic = cos α (θ + 2φxm)cos α (2φym) Id = cos α (2φxm)cos α (θ + 2φym) Nx = {2(Ia - Ic)} / {(Ia + Ib + Ic + Id)tan(θ)} Ny = {2(Ib - Id)} / {(Ia + Ib + Ic + Id)tan(θ)} For example, the processor 310 determines the glossiness α using the non-linear least squares method. By such a pre-inspection procedure, the glossiness α of the object W is determined in advance.

[0100] FIG. 11 is a diagram showing the relationship between Ny, φx, and φy when the glossiness α = 5. FIG. 12 is a diagram showing the relationship between Ny, φx, and φy when the glossiness α = 10. FIG. 13 is a diagram showing the relationship between Ny, φx, and φy when the glossiness α = 20.

[0101] As shown in FIGS. 11 to 13, the relationship between the X and Y direction components of the normal vector and the Z axis, the respective angles φx and φy formed therewith, and Ny, which is the calculation result on the right side of Equation (5), shows a monotonic change. That is, as φy increases, Ny also increases. Further, when φy > 0, as φx increases, Ny decreases. When φy < 0, as φx increases, Ny also increases. However, when the glossiness α is close to 1, the relationship between Ny and φy is linear, whereas when the glossiness α increases, the relationship between Ny and φy becomes non-linear. Therefore, the processor 310 corrects the normal image according to the glossiness α.

[0102] Specifically, the processor 310 inversely calculates (φx, φy) from (Nx, Ny) using the above theoretical formula with the predetermined glossiness α substituted therein. The processor 310 corrects the X-direction normal image by replacing each pixel value Nx in the X-direction normal image with φx. Similarly, the processor 310 corrects the Y-direction normal image by replacing each pixel value Ny in the Y-direction normal image with φy.

[0103] Alternatively, the processor 310 may select one look-up table corresponding to the glossiness α from a group of pre-created look-up tables and convert (Nx, Ny) to (φx, φy) using the selected look-up table. The look-up table is created in advance using the above theoretical formula with the corresponding glossiness α substituted therein. By using the look-up table, the time required for the correction process of the normal image is shortened.

[0104] (Method for generating albedo image) When the glossiness α = 1 of the surface of the object W, the following equation (6) holds. μ = {(Ja + Jb + Jc + Jd) / 2}[{1 + tan 2(2φx)}{1 + tan 2 (2φy)}] 1 / 2 / {4cos(θ)} ··· Equation (6).

[0105] FIG. 14 is a diagram showing the relationship between the albedo μ, φx, and φy when the glossiness α = 5. FIG. 15 is a diagram showing the relationship between the albedo μ, φx, and φy when the glossiness α = 10. FIG. 16 is a diagram showing the relationship between the albedo μ, φx, and φy when the glossiness α = 20.

[0106] As shown in FIGS. 14 to 16, the relationship between the albedo μ, φx, and φy shows a monotonic change. However, when the glossiness α is close to 1, the relationship between the albedo μ, φx, and φy is linear, while when the glossiness α increases, the relationship between the albedo μ, φx, and φy becomes non-linear. Therefore, the processor 310 substitutes φx and φy, which are the pixel values of the X-direction normal image and the Y-direction normal image corrected according to the glossiness α, and the pixel values Ja to Jd of the polarization images 50a to 50d into the above formula to generate an albedo image. Each pixel value of the albedo image indicates the albedo μ.

[0107] (Method for generating a shape image) The shape image is generated based on the X-direction normal image and the Y-direction normal image corrected according to the glossiness α.

[0108] FIG. 17 is a diagram showing the process executed on the X-direction normal image for generating the shape image. The pixel value of the X-direction normal image indicates the magnitude of the X-direction component of the normal vector on the surface of the object W.

[0109] The processor 310 selects a single point surrounded by four pixels in the X-direction normal image as the point of interest Q. The horizontal direction of the X-direction normal image corresponds to the X direction. Therefore, as shown in FIG. 17, the processor 310 sets rectangular regions R1 and R2 on the left and right sides of the point of interest Q, respectively. The height of the rectangular regions R1 and R2 is a predetermined length L, and the width of the rectangular regions R1 and R2 is L / 2.

[0110] The processor 310 calculates the sum Sx1 of the pixel values included in the rectangular region R1. Similarly, the processor 310 calculates the sum Sx2 of the pixel values included in the rectangular region R2. The processor 310 calculates the difference Sx between the sum Sx1 and the sum Sx2. The processor 310 calculates the difference Sx for all the points surrounded by four pixels in the X-direction normal image.

[0111] FIG. 18 is a diagram showing the processing executed on the Y-direction normal image for generating the shape image. The pixel value of the Y-direction normal image indicates the magnitude of the Y-direction component among the normal vectors of the surface of the object W.

[0112] The processor 310 selects one point surrounded by four pixels in the Y-direction normal image as the target point Q. The vertical direction of the Y-direction normal image corresponds to the Y direction. Therefore, as shown in FIG. 18, the processor 310 sets rectangular regions R3 and R4 above and below the target point Q, respectively. The width of the rectangular regions R3 and R4 is L, and the height of the rectangular regions R3 and R4 is L / 2.

[0113] The processor 310 calculates Sy1 of the pixel values included in the rectangular region R3. Similarly, the processor 310 calculates Sy2 of the pixel values included in the rectangular region R4. The processor 310 calculates the difference Sy between the sum Sy1 and the sum Sy2. The processor 310 calculates the difference Sy for all the points surrounded by four pixels in the Y-direction normal image.

[0114] When there are defects such as scratches or dents on the surface of the object W, the normal vector changes greatly at the defects. The difference Sx increases as the X-direction component of the normal vector changes greatly. The difference Sy increases as the Y-direction component of the normal vector changes greatly. That is, the differences Sx and Sy take large values at locations where there are defects with unevenness such as scratches or dents. Therefore, the processor 310 generates a shape image with S obtained by the following equation as the pixel value. S = A(Sx + Sy)+B A is a parameter for determining the contrast of the shape image. B is a parameter for determining the overall pixel value level of the shape image. The processor 310 sets the values of parameters A and B so that the maximum, minimum, and the difference between the maximum and minimum of the pixel values in the shape image fall within a specified range. The specified range is predetermined according to the contrast and level suitable for defect inspection. Thereby, a shape image suitable for inspecting defects with unevenness is generated.

[0115] (Examples of polarization image, normal image, shape image, albedo image, average image) FIG. 19 is a diagram showing a polarization image obtained by imaging a button battery and various images generated from the polarization image. The processor 310 generates an X-direction normal image 51 and a Y-direction normal image 52 from the polarization images 50a to 50d. The processor 310 generates a shape image 53 based on the X-direction normal image 51 and the Y-direction normal image 52. The processor 310 generates a binary image 54 by binarizing the shape image 53. Further, the processor 310 generates an albedo image 55 and an average image 56 from the polarization images 50a to 50d.

[0116] In FIG. 19, there are dents in the region surrounded by the frame line F1 on the surface of the button battery. Further, there is dirt in the region surrounded by the frame line F2 on the surface of the button battery. As shown in FIG. 19, in the shape image 53, a change in pixel value corresponding to the dent portion is observed within the frame line F1. In the binary image 54, the dent portion is represented in white. Thereby, by using the shape image 53 or the binary image 54, defects with unevenness such as scratches or dents can be accurately inspected. Note that also in the X-direction normal image 51 and the Y-direction normal image 52, the pixel values are different between the dent portion and its surroundings. Therefore, even by using the X-direction normal image 51 and the Y-direction normal image 52, defects with unevenness can be inspected.

[0117] In the X-direction normal image 51, Y-direction normal image 52, shape image 53, and binary image 54, no change in pixel values is observed between the soiled portion and its surroundings. This is because the unevenness has not changed due to the soiling. In contrast, in the albedo image 55, a change in pixel values corresponding to the soiling is observed within the frame line F2. This is because the albedo (reflectivity) has changed due to the soiling. Thus, by using the albedo image 55, defects that cause a change in the albedo (reflectivity), such as soiling, can be accurately inspected.

[0118] FIG. 20 is a diagram showing a polarization image obtained by imaging the side surface of a dry battery and various images generated from the polarization image. FIG. 20 shows polarization images 50a to 50d, an X-direction normal image 51, a Y-direction normal image 52, and an average image 56 generated from the polarization images 50a to 50d, and a shape image 53 and a binary image 54 generated from the X-direction normal image 51 and the Y-direction normal image 52. In FIG. 20, there are dents in the area surrounded by the frame line F1 on the side surface of the dry battery. In the shape image 53, a change in pixel values corresponding to the dent portion is observed within the frame line F1. In the binary image 54, the dent portion is represented in white. Thus, by using the shape image 53 or the binary image 54, defects that cause unevenness, such as scratches or dents, can be accurately inspected.

[0119] FIG. 21 is a diagram showing a polarization image obtained by imaging the bottom surface of a dry battery and various images generated from the polarization image. FIG. 21 shows polarization images 50a to 50d, an X-direction normal image 51, a Y-direction normal image 52, and an average image 56 generated from the polarization images 50a to 50d, and a shape image 53 generated from the X-direction normal image 51 and the Y-direction normal image 52. In FIG. 21, there are dents in the area surrounded by the frame line F1 on the bottom surface of the dry battery. In the shape image 53, a change in pixel values corresponding to the dent portion is observed within the frame line F1. Thus, by using the shape image 53, defects that cause unevenness, such as scratches or dents, can be accurately inspected.

[0120] FIG. 22 is a diagram showing a polarization image obtained by imaging a textured resin surface and various images generated from the polarization image. FIG. 22 shows polarization images 50a to 50d, an X-direction normal image 51, a Y-direction normal image 52, and an average image 56 generated from the polarization images 50a to 50d, and a shape image 53 and a binary image 54 generated from the X-direction normal image 51 and the Y-direction normal image 52. In FIG. 22, there are dents in the area surrounded by the frame line F1 on the resin surface. Further, there is dirt in the area surrounded by the frame line F2 on the resin surface.

[0121] As shown in FIG. 22, in the shape image 53, a change in pixel value corresponding to the dent portion is observed within the frame line F1. In the binary image 54, the dent portion is represented in white. Thus, by using the shape image 53 or the binary image 54, defects with unevenness such as scratches or dents can be accurately inspected.

[0122] In the X-direction normal image 51, the Y-direction normal image 52, the shape image 53, and the binary image 54, no change in pixel value is observed between the dirty portion and its surroundings. This is because the dirt has not caused a change in unevenness. On the other hand, in the average image 56, a change in pixel value corresponding to the dirty portion is observed within the frame line F2. This is because the albedo (reflectivity) has increased due to the dirt. Thus, even by using the average image 56, defects that cause a change in albedo (reflectivity) such as dirt can be accurately inspected.

[0123] (B-2. Second inspection example) The second inspection example uses two images obtained respectively under bright-field illumination and dark-field illumination conditions. Bright-field illumination is an illumination method in which the specular reflection light from the surface of the object W enters the polarization camera 20. Dark-field illumination is an illumination method in which the specular reflection light from the surface of the object W does not enter the polarization camera 20, and only the diffuse reflection light enters the polarization camera 20. In the part where there is a scratch, light is less likely to be specularly reflected. Therefore, in the image obtained under bright-field illumination conditions, the brightness of the part where there is a scratch decreases. Thus, by using the image obtained under bright-field illumination conditions, scratches can be inspected accurately. On the other hand, in the part where there is dirt or foreign matter, diffuse reflection is likely to occur. Therefore, in the image obtained under dark-field illumination conditions, the brightness of the part where there is dirt or foreign matter increases. Thus, by using the image obtained under dark-field illumination conditions, dirt or foreign matter can be inspected accurately.

[0124] (Arrangement of the lighting unit) FIG. 23 is a diagram showing the arrangement of a plurality of lighting units according to the second inspection example. As shown in FIG. 23, the plurality of lighting units 10 includes lighting units 10e and 10f. The lighting units 10e and 10f are arranged such that the elevation angles with respect to the object W are different from each other.

[0125] The lighting unit 10f is a ring-shaped lighting unit centered on the optical axis 25 of the polarization camera 20. The lighting unit 10f has a ring-shaped light-emitting part 11f centered on the optical axis 25 of the polarization camera 20 and a linear polarization filter 12f attached to the light-emitting surface of the light-emitting part 11f. The elevation angle of the lighting unit 10f with respect to the object W is set such that the specular reflection light from the object W does not enter the polarization camera 20.

[0126] FIG. 24 is a diagram showing the configuration of the illumination unit 10e. The illumination unit 10e is coaxial illumination that irradiates the object W with illumination light along the optical axis 25 of the polarization camera 20. As shown in FIG. 24, the illumination unit 10e includes a light emitting unit 11e, a linear polarization filter 12e, and a half mirror 13e. The linear polarization filter 12e is disposed between the light emitting surface of the light emitting unit 11e and the half mirror 13e, and transmits linearly polarized light along a predetermined direction among the non-polarized light irradiated from the light emitting unit 11e. The half mirror 13e projects the linearly polarized light transmitted through the linear polarization filter 12e along the optical axis 25 of the polarization camera 20.

[0127] The linear polarization filters 12e and 12f are arranged such that the polarization directions of the linearly polarized light irradiated from the illumination units 10e and 10f to the object W are orthogonal to each other.

[0128] (Inspection method) In the second inspection example, the inspection system 1 includes a polarization camera 20 including the polarizers 22a to 22d shown in FIG. 2. The polarization direction of the polarizer 22a coincides with (is parallel to) the polarization direction of the linearly polarized light irradiated from the illumination unit 10e to the object W. The polarization direction of the polarizer 22c coincides with (is parallel to) the polarization direction of the linearly polarized light irradiated from the illumination unit 10f. Therefore, the light irradiated from the illumination unit 10e and specularly reflected by the object W passes through the polarizer 22a and does not pass through the polarizer 22c. A part of the light irradiated from the illumination unit 10f and diffusely reflected by the object W passes through the polarizer 22c. Note that the light irradiated from the illumination unit 10f and specularly reflected by the object W does not enter the polarization camera 20.

[0129] FIG. 25 is a diagram showing an example of a plurality of polarization images obtained in the second inspection example. The polarization images 50a to 50d respectively correspond to the polarizers 22a to 22d.

[0130] The polarized image 50a shows the luminance of the light irradiated from the illumination unit 10e and regularly reflected by the object W. That is, the polarized image 50a corresponds to an image obtained by imaging under bright-field illumination conditions. Therefore, scratches can be easily confirmed within the frame line F1 of the polarized image 50a. Thus, by using the polarized image 50a, scratches can be accurately inspected.

[0131] The polarized image 50c shows the luminance of the light that has passed through the polarizer 22c among the light diffusely reflected by the object W and irradiated from the illumination unit 10f. That is, the polarized image 50c corresponds to an image obtained by imaging under dark-field illumination conditions. Therefore, dirt can be easily confirmed within the frame line F2 of the polarized image 50c. Thus, by using the polarized image 50c, dirt can be accurately inspected.

[0132] The polarized images 50b and 50d show intermediate luminance between the polarized images 50a and 50c. Therefore, the polarized images 50b and 50d may not be used for inspecting the object W.

[0133] (B-3. Third inspection example) The third inspection example uses the phase-shift method. The phase-shift method is a method for measuring the three-dimensional shape of the object W from a plurality of images captured by irradiating a stripe pattern in which the irradiation intensity is modulated in a sine wave while shifting the phase.

[0134] (Arrangement of illumination units) FIG. 26 is a diagram showing an example of the arrangement of a plurality of illumination units according to the third inspection example. As shown in FIG. 26, the plurality of illumination units 10 include illumination units 10e, 10g to 10i. The illumination unit 10e irradiates the object W with illumination light coaxial with the optical axis 25 of the polarization camera 20 as described in the second inspection example (see FIG. 24).

[0135] Each of the illumination units 10g to 10i is a ring-shaped illumination. The illumination units 10g to 10i each have a ring-shaped light-emitting part 11g to 11i centered on the optical axis 25 of the polarization camera 20 and a linear polarizing filter 12g to 12i attached to the light-emitting surface of the light-emitting part.

[0136] When the polarization direction of the light irradiated from the illumination unit 10e is taken as the reference direction, the linear polarization filters 12e, 12g to 12i are arranged such that the angles formed by the polarization directions of the light irradiated from the illumination units 10e, 10g to 10i and the reference direction are 0°, 45°, 90°, and 135°, respectively.

[0137] The illumination units 10e, 10g to 10i are arranged such that the elevation angles with respect to the object W are different from each other. Specifically, the illumination units 10e, 10g to 10i are arranged such that the elevation angles with respect to the object W decrease in this order. In other words, the incident angles of the illumination light from the illumination units 10e, 10g to 10i to the object W increase in this order. The elevation angle of the illumination unit 10e with respect to the object W is 90°, and the incident angle of the illumination light from the illumination unit 10e to the object W is 0°.

[0138] In the third inspection example, the inspection system 1 includes a polarization camera 20 including polarization elements 22a to 22d shown in FIG. 2. The polarization directions of the polarization elements 22a to 22d are parallel to the polarization directions of the light irradiated from the illumination units 10e, 10g to 10i, respectively. Therefore, the light irradiated from the illumination units 10e, 10g to 10i and specularly reflected by the object W passes through the polarization elements 22a to 22d, respectively. The light irradiated from the illumination unit 10e has components parallel to the polarization directions of the polarization elements 22b and 22d. Therefore, some of the components of the light irradiated from the illumination unit 10e and specularly reflected by the object W pass through the polarization elements 22b and 22d. Specifically, the amount of light passing through each of the polarization elements 22b and 22d among the light irradiated from the illumination unit 10e is about 1 / 2 of the amount of light passing through the polarization element 22a irradiated from the illumination unit 10e. Similarly, some of the components of the light irradiated from the illumination unit 10g and specularly reflected by the object W pass through the polarization elements 22a and 22c. Some of the components of the light irradiated from the illumination unit 10h and specularly reflected by the object W pass through the polarization elements 22b and 22d. Some of the components of the light irradiated from the illumination unit 10i and specularly reflected by the object W pass through the polarization elements 22a and 22c. The light irradiated from the illumination units 10e, 10g to 10i and specularly reflected by the object W does not pass through the polarization elements 22c, 22d, 22a, and 22b, respectively.

[0139] FIG. 27 is a diagram showing the amount of light transmitted through each polarizer among the light irradiated from the illumination units 10e, 10g to 10i and specularly reflected by the object W. As shown in FIG. 27, the amount of light transmitted through each of the polarizers 22a to 22d follows a sine wave. That is, the polarization images 50a to 50d corresponding to the polarizers 22a to 22d respectively correspond to images captured under the condition that the object W is irradiated with concentric stripe pattern light. Further, as shown in FIG. 27, the phases of the stripe patterns corresponding to the polarizers 22a to 22d are shifted by π / 2 each.

[0140] FIG. 28 is a diagram showing another example of the arrangement of a plurality of illumination units according to the third inspection example. The plurality of illumination units 10 shown in FIG. 28 are different from the plurality of illumination units 10 shown in FIG. 26 in that they further include illumination units 10j to 10l.

[0141] Each of the illumination units 10j to 10l is a ring-shaped illumination. Each of the illumination units 10j to 10l has a ring-shaped light emitting part 11j to 11l centered on the optical axis 25 of the polarization camera 20 and a linear polarization filter 12j to 12l attached to the light emitting surface of the light emitting part 11j to 11l.

[0142] When the polarization direction of the light irradiated from the illumination unit 10e is taken as the reference direction, the linear polarization filters 12j to 12l are arranged such that the angles formed by the polarization direction of the light irradiated from the illumination units 10j to 10l and the reference direction are 22.5°, 67.5°, and 110.5° respectively.

[0143] The illumination units 10e, 10j, 10g, 10k, 10h, 10l, 10i are arranged with respect to the object W such that the elevation angle decreases in this order. In other words, the incident angles of the illumination light from the illumination units 10e, 10j, 10g, 10k, 10h, 10l, 10i to the object W increase in this order.

[0144] FIG. 29 is a diagram showing the amount of light transmitted through each polarizer among the light irradiated from the lighting units 10e, 10g to 10l and specularly reflected by the object W. As shown in FIG. 29, the amount of light transmitted through each of the polarizers 22a to 22d follows a sine wave. That is, the polarization images 50a to 50d corresponding to the polarizers 22a to 22d respectively correspond to images captured under the condition that the object W is irradiated with concentric stripe pattern light. Further, as shown in FIG. 29, the phases of the stripe patterns corresponding to the polarizers 22a to 22d are shifted by π / 2 each.

[0145] (Inspection method) The processor 310 inspects the object W based on the polarization images 50a to 50d. The processor 310 generates a phase image and a specular reflection image based on the polarization images 50a to 50d by the phase shift method.

[0146] When the two-dimensional coordinates of the image are represented as (x, y) and the values of the pixels (x, y) in the polarization images 50a to 50d are represented as Ja(x, y), Jb(x, y), Jc(x, y), and Jd(x, y) respectively, the phase of the pixel is Φ(x, y)=arctan[{Jb(x, y)-Jd(x, y)} / {Ja(x, y)-Jc(x, y)}] and is represented as such. The range of the normal angle of the object W where the stripe pattern can be imaged is 0° to 45°. The phase value Φ(x, y) is a value proportional to the angle formed by the normal direction of the object W and the optical axis 25 of the polarization camera 20. The processor 310 generates a phase image in which the value of the pixel (x, y) is Ip(x, y)={2π - Φ(x, y)}×128 / π. At this time, the phase image becomes a white pixel (256) when the angle formed by the normal direction of the object W and the optical axis 25 is 0°, and becomes a black pixel (0) when the angle formed by the normal direction of the object W and the optical axis 25 is 45°. Therefore, by using the phase image, the unevenness of the surface of the object W can be inspected.

[0147] Furthermore, the processor 310 has the value of the pixel (x, y) as A(x, y)=[{Ja(x, y)-Jc(x, y)} 2 +{Jb(x, y)-Jd(x, y)}2 1 / 2 Generate a specular reflection image. The specular reflection image represents the intensity of light specularly reflected on the surface of the object W. If there is a scratch on the object W, light may be diffusely reflected due to the fine shape of the scratch. In this case, the specular reflection component becomes relatively weak at the scratched part. Therefore, the unevenness of the surface of the object W can be inspected using the specular reflection image.

[0148] FIG. 30 is a diagram showing an example of polarization images 50a to 50d obtained using a plurality of illumination units 10 shown in FIG. 26. FIG. 31 is a diagram showing an example of polarization images 50a to 50d obtained using a plurality of illumination units 10 shown in FIG. 28. As shown in FIGS. 30 and 31, a stripe pattern specularly reflected on the surface of the object W is observed, and the phases of the stripe patterns are shifted by π / 2 in the polarization images 50a to 50d. Furthermore, by increasing the number of the illumination units 10, the stripe pattern becomes smoother. Thereby, the resolution in the normal direction of the surface of the object W is improved.

[0149] Note that it is also possible to adopt a configuration in which the coaxial illumination unit 10e is not provided and only the ring-shaped illumination units 10g to 10i (or illumination units 10g to 10l) are provided. In this case, the stripe pattern regarding the concentric circular central portion will be missing. By providing the illumination unit 10e, the missing of the stripe pattern regarding the central portion of the concentric circles can be reduced, and a more accurate inspection can be performed.

[0150] (B-4. Fourth inspection example) ​The fourth inspection example uses two images obtained respectively under the conditions of coaxial illumination and backlight. The image obtained under the illumination condition coaxial with the optical axis 25 of the polarization camera 20 shows the luminance of the specular reflection light on the surface of the object W. As described above, light is less likely to be specularly reflected at the portion where there is a scratch. Therefore, in the image obtained under the condition of coaxial illumination, the luminance of the portion where there is a scratch decreases. Thus, by using the image obtained under the condition of coaxial illumination, scratches can be inspected accurately. On the other hand, when the object W has light-shielding properties, in the image obtained under the condition of backlight, the luminance of the region corresponding to the object W becomes 0. Therefore, the outer periphery of the object W can be easily confirmed. Thus, by using the image obtained under the condition of backlight, burrs or chips on the outer periphery of the object W can be inspected accurately.

[0151] (Arrangement of Illumination Units) FIG. 32 is a diagram showing the arrangement of a plurality of illumination units according to the fourth inspection example. As shown in FIG. 32, the plurality of illumination units 10 include illumination units 10e and 10m. As described in the second inspection example, the illumination unit 10e irradiates the object W with illumination light along the optical axis 25 of the polarization camera 20 (see FIG. 24).

[0152] The illumination unit 10m is arranged on the side opposite to the polarization camera 20 of the object W as a backlight. That is, the illumination unit 10m irradiates illumination light from the back side of the object W. The illumination unit 10m includes a flat light-emitting part 11m and a linear polarization filter 12m attached to the light-emitting surface of the light-emitting part 11f.

[0153] The linear polarization filter 12e (see FIG. 24) of the illumination unit 10e and the linear polarization filter 12m are arranged such that the polarization directions of the linear polarization light irradiated from the illumination units 10e and 10m to the object W are orthogonal to each other.

[0154] (Inspection Method) In the fourth inspection example, the inspection system 1 includes a polarization camera 20 including polarizers 22a to 22d shown in FIG. 2. The polarization direction of the polarizer 22a coincides with (is parallel to) the polarization direction of the linearly polarized light irradiated from the illumination unit 10e to the object W. The polarization direction of the polarizer 22c coincides with (is parallel to) the polarization direction of the linearly polarized light irradiated from the illumination unit 10m. Therefore, the light irradiated from the illumination unit 10e and specularly reflected by the object W passes through the polarizer 22a and does not pass through the polarizer 22c. The light irradiated from the illumination unit 10m and traveling around the object W passes through the polarizer 22c and does not pass through the polarizer 22a.

[0155] FIG. 33 is a diagram showing an example of a plurality of polarization images obtained in the fourth inspection example. The polarization images 50a to 50d respectively correspond to the polarizers 22a to 22d.

[0156] The polarization image 50a shows the luminance of the light irradiated from the illumination unit 10e and specularly reflected by the object W. Therefore, it is easily confirmed that the luminance of the damaged portion is reduced within the frame line F1 of the polarization image 50a. Therefore, the processor 310 can accurately inspect the damage using the polarization image 50a.

[0157] The polarization image 50c shows the luminance of the light irradiated from the illumination unit 10m and traveling around the object W. That is, the polarization image 50c corresponds to an image obtained under the conditions of backlight. Therefore, burrs on the outer periphery of the object W are easily confirmed within the frame line F3 of the polarization image 50c. Therefore, the processor 310 can accurately inspect burrs or chips on the outer periphery of the object W using the polarization image 50c.

[0158] The polarization images 50b and 50d show intermediate luminance between the polarization images 50a and 50c. Therefore, the polarization images 50b and 50d may not be used for inspecting the object W.

[0159] (B-5. Fifth inspection example) The fifth inspection example uses the high dynamic range technique. The high dynamic range technique is a technique for generating an image (high dynamic range image) with a wide dynamic range having less white blooming and black crushing by synthesizing a plurality of images under conditions of different illumination intensities.

[0160] (Arrangement of illumination units) FIG. 34 is a diagram showing the arrangement of a plurality of illumination units according to the fifth inspection example. As shown in FIG. 34, the plurality of illumination units 10 includes illumination units 10n and 10o.

[0161] The illumination unit 10n has a light emitting unit 11n that emits non-polarized light and a linear polarization filter 12n disposed on the object W of the light emitting unit 11n. Therefore, linearly polarized light is irradiated from the illumination unit 10n to the object W.

[0162] The illumination unit 10o has a light emitting unit 11o that emits non-polarized light and does not have a linear polarization filter. Therefore, non-polarized light is irradiated from the illumination unit 10o to the object W.

[0163] Note that the illumination units 10n and 10o are preferably arranged close to each other. Thereby, the irradiation directions from the illumination units 10n and 10o to the object W become substantially the same, and as will be described later, a plurality of polarization images 50 having different illumination intensities and substantially the same illumination direction can be obtained in a single imaging as illumination conditions.

[0164] (Inspection method) In the fifth inspection example, the inspection system 1 includes a polarization camera 20 including polarizers 22a to 22d shown in FIG. 2. The polarization direction of the linearly polarized light irradiated from the illumination unit 10n is parallel to the polarization direction of the polarizer 22a and orthogonal to the polarization direction of the polarizer 22c. Therefore, the light irradiated from the illumination unit 10n and specularly reflected by the object W passes through the polarizer 22a and does not pass through the polarizer 22c. The light irradiated from the illumination unit 10n and specularly reflected by the object W has components parallel to the polarization directions of the polarizers 22b and 22d. Therefore, some components of the light irradiated from the illumination unit 10n and specularly reflected by the object W pass through the polarizers 22b and 22d. Specifically, the amount of light passing through each of the polarizers 22b and 22d irradiated from the illumination unit 10n is about 1 / 2 of the amount of light passing through the polarizer 22a irradiated from the illumination unit 10n.

[0165] The non-polarized light irradiated from the illumination unit 10o has components parallel to the polarization directions of the polarizers 22a to 22d equally. Therefore, the amount of light passing through each of the polarizers 22a to 22d irradiated from the illumination unit 10o is the same.

[0166] Let In and Io be the intensities of the light irradiated from the illumination units 10n and 10o, specularly reflected by the object W, and passing through the polarizer 22a, respectively. At this time, the pixel values Ja to Jd of the polarization images 50a to 50d corresponding to the polarizers 22a to 22d are expressed as follows. Pixel value Ja of polarization image 50a: In + Io Pixel value Jb of polarization image 50b: In / 2 + Io Pixel value Jc of polarization image 50c: Io Pixel value Jd of polarization image 50d: In / 2 + Io From the above, the polarization images 50a to 50c correspond to a plurality of images under conditions of different illumination intensities from each other. Therefore, the processor 310 performs high-dynamic range synthesis on the polarization images 50a to 50c to generate a synthesized image. The processor 310 may generate a synthesized image using a known high-dynamic range synthesis method.

[0167] FIG. 35 is a diagram showing an example of a plurality of polarization images obtained in the fifth inspection example. As shown in FIG. 35, the polarization image 50a has the highest luminance, the polarization image 50c has the lowest luminance, and the polarization images 50b and 50d have intermediate luminance. The processor 310 synthesizes the polarization images 50a to 50c with a high dynamic range to generate a synthesized image 57. In the synthesized image 57, there is little white blooming or black crushing. Therefore, by using the synthesized image 57, the processor 310 can accurately inspect the object W.

[0168] <C. Modification Example> The number of polarizers 22 included in the unit region 21 of the polarization camera 20 is not limited to four, and may be a plurality. As described above, in the second inspection example and the fourth inspection example, the polarization images 50b and 50d may not be used. Therefore, the unit region 21 may include only the polarizers 22a and 22c and may not include the polarizers 22b and 22d. Similarly, in the fifth inspection example, the polarization image 50d is not used. Therefore, the unit region 21 may include only the polarizers 22a to 22c and may not include the polarizer 22d.

[0169] In the first inspection example, the plurality of illumination units 10 may include only the illumination units 10a and 10c and may not include the illumination units 10b and 10d. In this case, the unit region 21 of the polarization camera 20 may include only the polarizers 22a to 22c and may not include the polarizer 22d. The pixel values Ja and Jc of the polarization images 50a and 50c are represented by the following equations. Ja = Ia = μ[cos α (θ - 2φx)cos α (2φy)] Jc = Ic = μ[cos α (θ + 2φx)cos α (2φy)] When the glossiness α = 1 of the surface of the object W, the following equations (7) and (8) hold. Ja + Jc = 2μcos(θ)cos(2φx)cos(2φy) ··· Equation (7) Ja - Jc = 2μsin(θ)sin(2φx)cos(2φy) ··· Equation (8).

[0170] From the above equations (7) and (8), the following equation (9) is derived. tan(2φx) = (Ja - Jc) / {(Ja + Jc)tan(θ)} ··· Equation (9).

[0171] In Equation (9), the incident angle θ is determined in advance according to the positions of the illumination units 10a and 10c. Therefore, the processor 310 may calculate the right side of Equation (9) using the pixel values Ja and Jc of the polarization images 50a and 50c and the incident angle θ, and generate an X-direction normal image with the result Nx as the pixel value. Tan(2φx) (≡ Nx) represented by Equation (9) is a value that depends on the x-direction component nx of the normal vector. Therefore, the X-direction normal image represents the normal direction of the surface of the object W.

[0172] Furthermore, as shown in FIG. 17, the processor 310 sets rectangular regions R1 and R2 on the left and right sides of the point of interest Q, respectively. Then, the processor 310 calculates the difference Sx between the sum Sx1 of the values of the pixels included in the rectangular region R1 and the sum Sx2 of the values of the pixels included in the rectangular region R2. The processor 310 calculates the difference Sx for all the points surrounded by four pixels in the X-direction normal image. The processor 310 may generate a shape image with the difference Sx as the pixel value. As described above, the difference Sx takes a large value at a location where there is a defect with unevenness such as a scratch or a dent. Therefore, the processor 310 can accurately inspect the defect with unevenness by using the shape image.

[0173] In the first inspection example, it is assumed that an X-direction normal image and a Y-direction normal image are generated using the above equations (4) and (5). However, the method for generating the normal image is not limited to this. For example, a learning model for estimating a normal image from a plurality of polarization images is constructed using deep learning image generation technology. The processor 310 may generate a normal image from a plurality of polarization images using the learning model.

[0174] §3 Addendum As described above, the present embodiment includes the following disclosure.

[0175] (Configuration 1) An inspection system (1), comprising: a plurality of illumination units (10, 10a to 10o) for illuminating an object (W); a polarization camera (20) in which a unit area (21) including a plurality of polarizers (22, 22a to 22d) is repeatedly arranged; an inspection device (30); the plurality of illumination units (10, 10a to 10o) irradiate illumination light with different polarization states; the plurality of polarizers (22, 22a to 22d) transmit light with different polarization directions; the polarization camera (20) captures an image in a state where the plurality of illumination units (10, 10a to 10o) are simultaneously lit, and outputs a plurality of polarization images (50, 50a to 50d) respectively corresponding to the plurality of polarizers (22, 22a to 22d); the inspection device (30) inspects the object (W) using the plurality of polarization images (50, 50a to 50d). The inspection system (1).

[0176] (Configuration 2) the plurality of illumination units are arranged such that azimuth angles around the optical axis (25) of the polarization camera (20) are different from each other; the plurality of illumination units include first to Nth illumination units (10a to 10d); the plurality of polarizers include first to Nth polarizers (22a to 22d); N is an integer of 2 or more; polarization directions of illumination light of the first to Nth illumination units (10a to 10d) are respectively parallel to polarization directions of light transmitted through the first to Nth polarizers (22a to 22d); the inspection device (30) generates a normal image (51, 52) indicating a normal direction of a surface of the object (W) from the plurality of polarization images (50a to 50d), and inspects the object (W) based on the normal image (51, 52). The inspection system (1) according to Configuration 1.

[0177] (Configuration 3) N is 4 The first illumination unit (10a) and the third illumination unit (10c) are arranged at positions symmetric with respect to the optical axis (25) of the polarization camera (20). The second illumination unit (10b) and the fourth illumination unit (10d) are arranged at positions symmetric with respect to the optical axis (25) of the polarization camera (20). Around the optical axis (25) of the polarization camera (20), the difference between the first azimuth angle at which the first illumination unit (10a) is arranged and the second azimuth angle at which the second illumination unit (10b) is arranged is 90°. The plurality of polarization images include first to fourth polarization images (50a to 50b) corresponding to the first to fourth polarizers (22a to 22d) respectively. The inspection device (30) is Based on the first to fourth polarization images (50a to 50b), a first normal image (51) indicating the magnitude of the component along the direction of the first azimuth angle in the normal vector of the surface of the object (W) is generated. Based on the first to fourth polarization images, a second normal image (52) indicating the magnitude of the component along the direction of the second azimuth angle in the normal vector of the surface of the object (W) is generated. Based on the first normal image (51) and the second normal image (52), a shape image (53) indicating the shape of the surface of the object (W) is generated. The inspection system (1) according to Configuration 2, which inspects the object (W) based on the shape image (53).

[0178] (Configuration 4) The inspection system (1) according to Configuration 3, wherein the angles formed by the polarization directions of the illumination lights of the second illumination unit (10b), the third illumination unit (10c), and the fourth illumination unit (10d) and the polarization direction of the illumination light of the first illumination unit (10a) are 45°, 90°, and 135° respectively.

[0179] (Configuration 5) The plurality of illumination units (10e to 10l) are arranged such that the elevation angles with respect to the object are different from each other, in the inspection system (1) according to Configuration 1.

[0180] (Configuration 6) The plurality of illumination units include a first illumination unit (10e) that irradiates illumination light along an optical axis of the polarization camera; a ring-shaped second illumination unit (10f) centered on the optical axis of the polarization camera; the plurality of polarizers includes a first polarizer (22a) and a second polarizer (22c); An inspection system (1) as described in configuration 5, wherein the polarization directions of the illumination light irradiated from the first illumination section (10e) and the second illumination section (10f) correspond to the polarization directions of the light transmitted through the first polarizer (22a) and the second polarizer (22c), respectively.

[0181] (Configuration 7) The plurality of illumination units include a plurality of ring-shaped illumination units (10g to 10l) concentrically arranged around the optical axis of the polarization camera, The inspection device (30) generating a phase image indicating an angle between a normal direction of the surface of the object (W) and an optical axis direction of the polarization camera based on the plurality of polarization images (50a to 50d); The inspection system (1) of configuration 5, which inspects the object (W) based on the phase image.

[0182] (Configuration 8) The inspection system (1) according to configuration 7, wherein the plurality of illumination units further includes an illumination unit (10e) that irradiates illumination light along an optical axis (25) of the polarization camera (20).

[0183] (Configuration 9) The plurality of illumination units include a first illumination unit (10e) that irradiates illumination light along an optical axis of the polarization camera; A second illumination unit (10m) that irradiates illumination light from the back side of the object, the plurality of polarizers includes a first polarizer (22a) and a second polarizer (22c); In the inspection system (1) according to Configuration 1, the polarization directions of the illumination light emitted from the first illumination unit (10e) and the second illumination unit (10m) coincide with the polarization directions of the light transmitted through the first polarizer (22a) and the second polarizer (22c), respectively.

[0184] (Configuration 10) The plurality of illumination units include a first illumination unit (10n) that irradiates linearly polarized illumination light and a second illumination unit (10o) that irradiates non-polarized light. The plurality of polarizers include a first polarizer (22a) that transmits light having the same polarization direction as the polarization direction of the illumination light of the first illumination unit (10n), a second polarizer (22b) that transmits light having a polarization direction at an angle of 45° with the polarization direction of the light transmitted through the first polarizer (22a), and a third polarizer (22c) that transmits light having a polarization direction at an angle of 90° with the polarization direction of the light transmitted through the first polarizer (22a). The plurality of polarized images include first to third polarized images (55a to 55c) corresponding to the first to third polarizers (22a to 22c), respectively. The inspection device (30) performs high-dynamic range synthesis on the first to third polarized images (55a to 55c) to generate a synthesized image, and inspects the object (W) based on the synthesized image. The inspection system (1) according to Configuration 1.

[0185] (Configuration 11) An inspection method using a plurality of illumination units (10, 10a to 10o) that illuminate an object (W) and a polarization camera (20) in which a unit region (21) including a plurality of polarizers (22, 22a to 22d) is repeatedly arranged, wherein the plurality of illumination units (10, 10a to 10o) irradiate illumination light having different polarization states, the plurality of polarizers (22, 22a to 22d) transmit light having different polarization directions, and the inspection method In a state where the plurality of illumination units (10, 10a to 10o) are simultaneously lit, by imaging the object (W) using the polarization camera (20), a plurality of polarization images (50, 50a to 50d) respectively corresponding to the plurality of polarizers (22, 22a to 22d) are acquired; A step of inspecting the object (W) using the plurality of polarization images (50, 50a to 50d). The inspection method includes these steps.

[0186] Although the embodiments of the present invention have been described, the embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0187] 1 Inspection system, 2 Conveyor belt, 10, 10a to 10o Illumination unit, 11a to 11o Light emitting unit, 12a to 12n Linear polarizing filter, 13e Half mirror, 20 Polarization camera, 21 Unit area, 22, 22a to 22d Polarizer, 25, 225 Optical axis, 30 Inspection device, 50, 50a to 50d Polarization image, 51 X-direction normal image, 52 Y-direction normal image, 53 Shape image, 54 Binary image, 55 Albedo image, 56 Average image, 57 Composite image, 110 Illumination device, 110a to 110d Arc region, 302 Display unit, 304 Keyboard, 306 Memory card, 310 Processor, 312 RAM, 314 Display controller, 316 System controller, 318 Controller, 320 Hard disk, 322 Camera interface, 324 Input interface, 328 Communication interface, 330 Memory card interface, 350 Inspection program, F1, F2 Frame line, P Point, Q Point of interest, R1 to R4 Rectangular region, W Object, n Normal vector.

Claims

1. An inspection system comprising: a plurality of illumination units for illuminating an object; a polarization camera in which a unit area including a plurality of polarizers is repeatedly arranged; an inspection device, wherein the plurality of illumination units irradiate illumination light having mutually different polarization states; the plurality of polarizers transmit light having mutually different polarization directions; the polarization camera outputs a plurality of polarization images respectively corresponding to the plurality of polarizers by imaging in a state where the plurality of illumination units are simultaneously lit; the inspection device inspects the object using the plurality of polarization images; the plurality of illumination units are arranged such that azimuth angles around the optical axis of the polarization camera are mutually different; the plurality of illumination units include first to Nth illumination units; the plurality of polarizers include first to Nth polarizers; N is an integer of 2 or more; the polarization directions of the illumination light of the first to Nth illumination units are respectively parallel to the polarization directions of the light transmitted through the first to Nth polarizers; the inspection device estimates the normal direction of the surface of the object from the plurality of polarization images using the illuminance difference stereo method; generates a normal image indicating the normal direction; An inspection system that inspects the object based on the normal image.

2. N is 4; the first illumination unit and the third illumination unit are arranged at positions symmetric with respect to the optical axis of the polarization camera; the second illumination unit and the fourth illumination unit are arranged at positions symmetric with respect to the optical axis of the polarization camera; around the optical axis of the polarization camera, the difference between the first azimuth angle at which the first illumination unit is arranged and the second azimuth angle at which the second illumination unit is arranged is 90°; the plurality of polarization images include first to fourth polarization images respectively corresponding to the first to fourth polarizers; the inspection device generates a first normal image indicating the magnitude of the component along the direction of the first azimuth angle in the normal vector of the surface of the object based on the first to fourth polarization images; generates a second normal image indicating the magnitude of the component along the direction of the second azimuth angle in the normal vector of the surface of the object based on the first to fourth polarization images; generates a shape image indicating the shape of the surface of the object based on the first normal image and the second normal image; The inspection system according to claim 1, wherein the object is inspected based on the shape image.

3. The angles formed between the polarization directions of the illumination light of the second illumination unit, the third illumination unit, and the fourth illumination unit and the polarization direction of the illumination light of the first illumination unit are 45°, 90°, and 135°, respectively. The inspection system according to claim 2.

4. An inspection system, A plurality of illumination units for illuminating an object, A polarization camera in which a unit region including a plurality of polarizers is repeatedly arranged, An inspection device, and The plurality of illumination units irradiate illumination light in different polarization states, The plurality of polarizers transmit light in different polarization directions, The polarization camera outputs a plurality of polarization images respectively corresponding to the plurality of polarizers by imaging in a state where the plurality of illumination units are simultaneously lit, The inspection device inspects the object using the plurality of polarization images, The plurality of illumination units are arranged such that the elevation angles with respect to the object are different from each other, The plurality of illumination units, A first illumination unit that irradiates illumination light along the optical axis of the polarization camera, A ring-shaped second illumination unit centered on the optical axis of the polarization camera, and The plurality of polarizers include a first polarizer and a second polarizer, The polarization directions of the illumination light irradiated from the first illumination unit and the second illumination unit coincide with the polarization directions of the light transmitted through the first polarizer and the second polarizer, respectively, The inspection device, Based on the polarization image corresponding to the first polarizer among the plurality of polarization images, defects that are less likely to be specularly reflected than the surrounding normal portions are inspected, Based on the polarization image corresponding to the second polarizer among the plurality of polarization images, defects that are more likely to be diffusely reflected than the surrounding normal portions are inspected. The inspection system.

5. An inspection system, A plurality of illumination units for illuminating an object, A polarization camera in which a unit region including a plurality of polarizers is repeatedly arranged, An inspection device, and The plurality of illumination units irradiate illumination light in different polarization states, The plurality of polarizers transmit light in different polarization directions, The polarization camera outputs a plurality of polarization images respectively corresponding to the plurality of polarizers by imaging in a state where the plurality of illumination units are simultaneously lit, The inspection device inspects the object using the plurality of polarization images, The plurality of illumination units are arranged such that the elevation angles with respect to the object are different from each other, The plurality of illumination units include a plurality of concentric ring-shaped illumination units centered on the optical axis of the polarization camera, The inspection device is regards the plurality of polarization images as a plurality of images in which stripe patterns with different phases are imaged, using the phase shift method, based on the plurality of polarization images, generates a phase image indicating an angle formed by the normal direction of the surface of the object and the optical axis direction of the polarization camera, An inspection system that inspects the object based on the phase image.

6. The inspection system according to claim 5, wherein the plurality of illumination units further include an illumination unit that irradiates illumination light along the optical axis of the polarization camera.

7. An inspection method using a plurality of illumination units for illuminating an object and a polarization camera in which a unit area including a plurality of polarizers is repeatedly arranged, the plurality of illumination units irradiate illumination light with different polarization states, the plurality of polarizers transmit light with different polarization directions, the inspection method is a step of acquiring a plurality of polarization images respectively corresponding to the plurality of polarizers by imaging the object using the polarization camera in a state where the plurality of illumination units are simultaneously lit; a step of inspecting the object using the plurality of polarization images, and the plurality of illumination units are arranged such that azimuth angles around the optical axis of the polarization camera are different from each other, the plurality of illumination units include first to Nth illumination units, the plurality of polarizers include first to Nth polarizers, N is an integer of 2 or more, the polarization directions of the illumination light of the first to Nth illumination units are respectively parallel to the polarization directions of the light transmitted through the first to Nth polarizers, the step of inspecting is estimating the normal direction of the surface of the object from the plurality of polarization images using the illuminance difference stereo method; generating a normal image indicating the normal direction; An inspection method including inspecting the object based on the normal image.

Images