WO2022137579A1 - Inspection system and inspection method - Google Patents

Abstract

This inspection system comprises: a plurality of illumination parts that illuminate a subject; a polarization camera in which unit regions including a plurality of polarizers are repeatedly aligned; and an inspection device. The plurality of illumination parts emit illumination light of different polarization states. The plurality of polarizers allow the light of the different polarization directions to pass therethrough. The polarization cameras capture images while the plurality of illumination parts are lighted at the same time, thereby outputting a plurality of polarization images corresponding to each of the plurality of polarizers. The inspection device inspects the subject using the plurality of polarization images. As a result, inspection can be performed on the moving subject using a plurality of images having different illumination conditions.

Description

Inspection system and inspection method

This disclosure relates to an inspection system and an inspection method.

In the FA (Factory Automation) field, an image is taken while illuminating an object, and the appearance of the object is inspected using the obtained image. Conventionally, in order to improve inspection performance, a method of changing lighting conditions and taking multiple images has been known.

For example, in the photometric stereo method, the normal of the surface of an object is estimated using a plurality of images obtained by taking multiple images while changing the direction of the light source. As a result, the unevenness of the surface is inspected without being affected by the dirt on the surface of the object.

Further, Japanese Patent Application Laid-Open No. 2016-105044 (Patent Document 1) discloses an image processing device that acquires an image of return light from an object each time the object is sequentially irradiated with P-type illumination light. ing.

Japanese Unexamined Patent Publication No. 2016-105044

When the object is moving, in the above-mentioned conventional method, the positions of the objects in the plurality of images obtained by multiple imaging are different from each other. Therefore, the above-mentioned conventional method cannot be applied to a moving object.

The present disclosure has been made in view of the above problems, and an object thereof is an inspection system and an inspection method capable of inspecting a moving object using a plurality of images having different lighting conditions. To provide.

According to an example of the present disclosure, the inspection system includes a plurality of lighting units for illuminating an object, a polarizing camera in which unit regions including a plurality of polarizing elements are repeatedly arranged, and an inspection device. The plurality of lighting units irradiate illumination light having different polarization states from each other. The plurality of splitters transmit light in different polarization directions from each other. The polarizing camera outputs a plurality of polarized images corresponding to the plurality of polarizing elements by taking an image in a state where the plurality of lighting units are lit at the same time. The inspection device inspects the object using a plurality of polarized images.

According to the above disclosure, each of the plurality of polarized images is an image captured under illumination conditions mainly including the illumination condition of the illumination unit that irradiates the polarized light having the smallest angle with the polarization direction of the corresponding polarizing element. Corresponds to. That is, by one-shot imaging, a plurality of polarized images corresponding to a plurality of lighting conditions are acquired. Therefore, it is possible to inspect a moving object using a plurality of polarized images having different illumination conditions.

In the above disclosure, the plurality of lighting units are arranged so that the azimuth angles around the optical axis of the polarizing camera are different from each other. The plurality of lighting units include the first to Nth lighting units. The plurality of modulators include the first to Nth substituents. N is an integer of 2 or more. The polarization direction of the illumination light of the first to Nth illumination units is parallel to the polarization direction of the light transmitted through the first to Nth polarizing elements. The inspection device generates a normal image showing the normal direction of the surface of the object from a plurality of polarized images, and inspects the object based on the normal image.

According to the above disclosure, the polarized image corresponding to each of the first to Nth polarizing elements is imaged so that the light of the illuminating unit that irradiates the illumination light parallel to the polarization direction of the polarizing element is the strongest. To. That is, among the first to Nth illumination units, the illumination units having the greatest influence on the polarized image are different from each other in the plurality of polarized images. The first to Nth illumination units are arranged so that the azimuth angles around the optical axis of the polarizing camera are different from each other. Therefore, a plurality of polarized images having different conditions regarding the azimuth angle of the illumination light can be obtained by one imaging. Then, a normal image is generated from the plurality of polarized images. By using the normal image, the unevenness of the surface of the object is inspected with high accuracy.

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

According to the above disclosure, a first normal image showing the size of the component along the direction of the first azimuth and a second normal image showing the size of the component along the direction of the second azimuth. A normal image is generated. As a result, for example, even if the formation direction of scratches on the surface of the object is random, the shape change according to the scratches appears in the shape image. Therefore, scratches on the surface of the object are inspected with high accuracy.

In the above disclosure, the angle formed by the polarization direction 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 is 45 °, respectively. 90 ° and 135 °.

According to the above disclosure, the first to fourth polarized images correspond to the images captured under the illumination conditions mainly the illumination conditions of the first to fourth illumination units, respectively. Then, the influence of the illumination light of the third illumination unit on the first polarized image can be minimized. Similarly, the influence of the illumination light of the fourth, first and second illumination units on the second, third and fourth polarized images can be minimized as much as possible.

In the above disclosure, the plurality of lighting units are arranged so that the elevation angles with respect to the object are different from each other.

According to the above disclosure, as a lighting condition, a plurality of polarized images having different elevation angles with respect to an object can be obtained by one imaging.

In the above disclosure, the plurality of illumination units include a first illumination unit that irradiates the illumination light along the optical axis of the polarized camera, and a ring-shaped second illumination unit centered on the optical axis of the polarized camera. including. The plurality of splitters include a first modulator and a second modulator. The polarization directions of the illumination light emitted from the first illumination unit and the second illumination unit coincide with the polarization directions of the light transmitted through the first and second polarizing elements, respectively.

According to the above disclosure, the first polarized image corresponding to the first polarizing element shows the brightness of the light that is radiated from the first illumination unit and is specularly reflected on the surface of the object. That is, the first polarized image corresponds to an image obtained under brightfield illumination conditions. In an image obtained under bright-field illumination conditions, the brightness of the scratched portion is reduced. Therefore, by using the first polarized image, scratches can be inspected with high accuracy.

The second polarized image corresponding to the second polarizing element shows the brightness of the light emitted from the second illumination unit and diffusely reflected on the surface of the object. That is, the second polarized image corresponds to the image obtained under the conditions of dark field illumination. In the image obtained under the condition of dark field illumination, the brightness of the portion where the stain is present is different from the brightness of the surrounding portion. Therefore, by using the second polarized image, dirt can be inspected with high accuracy.

As described above, the first polarized image suitable for the inspection of scratches and the second polarized image suitable for the inspection of stains are acquired by one imaging.

In the above disclosure, the plurality of illumination units include a plurality of concentric ring-shaped illumination units centered on the optical axis of the polarizing camera. The inspection device generates a phase image showing an angle formed by the normal direction of the surface of the object and the optical axis direction of the polarized camera based on a plurality of polarized images. Inspect the object based on the phase image.

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 amount of light emitted from the plurality of ring-type illumination units, specularly reflected on the surface of the object, and transmitted through each polarizing element. Are different from each other. Therefore, a plurality of polarized images show fringe patterns having different phases from each other. That is, a plurality of polarized images in which fringe patterns having different phases are captured can be obtained by one imaging. The phase image generated from the plurality of polarized 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 can be inspected with high accuracy.

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

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

In the above disclosure, the plurality of illumination units include a first illumination unit that irradiates the illumination light along the optical axis of the polarizing camera, and a second illumination unit that irradiates the illumination light from the back side of the object. include. The plurality of splitters include a first modulator and a second modulator. The polarization directions of the illumination light emitted from the first illumination unit and the second illumination unit coincide with the polarization directions of the light transmitted through the first and second polarizing elements, respectively.

According to the above disclosure, the first polarized image corresponding to the first polarizing element shows the brightness of the light that is radiated from the first illumination unit and is specularly reflected on the surface of the object. When light is incident on the part where the scratch is present, it is diffusely reflected. Therefore, in the first polarized image, the brightness of the portion where the scratch is present is reduced. Therefore, by using the first polarized image, scratches can be inspected with high accuracy.

The second polarized image corresponding to the second polarizing element shows the brightness of the light emitted from the second illumination unit and incident on the polarizing camera. Therefore, when the object has a light-shielding property, the shape of the outer periphery of the object is clearly recognized in the second polarized image. Therefore, by using the second polarized image, burrs or chips on the outer periphery of the object can be inspected with high accuracy.

As described above, the first polarized image suitable for the inspection of scratches and the second polarized image suitable for the inspection of burrs or chips on the outer periphery of the object are acquired by one imaging.

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 illumination light. The plurality of splitters include the first to third substituents, and the first substituent transmits light in the same polarization direction as the polarization direction of the illumination light of the first illumination unit. The second polarizing element transmits light in the polarization direction having an angle of 45 ° with the polarization direction of the light transmitted through the first polarizing element. The third polarizing element transmits light in the polarization direction having an angle of 90 ° with the polarization direction of the light transmitted through the first polarizing element. The plurality of polarized images include the first to third polarized images corresponding to the first to third modulators, respectively. The inspection device synthesizes the first to third polarized images in a high dynamic range to generate a composite image, and inspects the object based on the composite image.

According to the above disclosure, the non-polarized light emitted from the second illumination unit uniformly transmits the first to third polarizing elements. On the other hand, the linearly polarized light emitted from the first illumination unit transmits the first polarizing element, but does not transmit the third polarizing element. Further, the intensity of the light emitted from the first illumination unit and transmitted through the second polarizing element is ½ of the intensity of the light emitted from the first illumination unit and transmitted through the first polarizing element. .. Therefore, the first to third polarized images correspond to a plurality of images captured under illumination conditions in which the illumination intensities are different from each other. That is, first to third polarized images having different illumination intensities can be obtained by one imaging. Then, the first to third polarized images are combined in a high dynamic range, and a combined image is generated. By using the composite image, the inspection accuracy of the object is improved.

According to an example of the present disclosure, the inspection method uses a plurality of lighting units for illuminating an object and a polarizing camera in which unit regions including a plurality of polarizing elements are repeatedly arranged. The plurality of lighting units irradiate illumination light having different polarization states from each other. The plurality of splitters transmit light in different polarization directions from each other. The inspection method includes a step of acquiring a plurality of polarized images corresponding to a plurality of polarizing elements by imaging an object using a polarizing camera in a state where a plurality of lighting units are lit at the same time, and a plurality of inspection methods. It comprises a step of inspecting an object using a polarized image.

Even with the above disclosure, it is possible to inspect a moving object using a plurality of images with different lighting conditions.

According to the present disclosure, a moving object can be inspected using a plurality of images having different lighting conditions.

It is a schematic diagram which shows the whole structure of the inspection system which concerns on this embodiment. It is a figure which shows an example of the arrangement of the polarizing element which a polarizing camera has. It is a schematic diagram which shows the hardware composition of an inspection apparatus. It is a figure which shows an example of the conventional lighting apparatus used in the photometric stereo method. It is a figure which shows the arrangement of the plurality of lighting parts which concerns on the 1st inspection example. It is a figure which shows an example of the polarization direction of a linear polarization filter 12a to 12d. It is a flowchart which shows an example of the flow of the inspection process in the 1st inspection example. It is a figure which shows the relationship between the illumination part 10a to 10d, and the normal vector n at the point P on the surface of an object W. It is a figure which shows the relationship between the traveling direction and the normal direction when the traveling direction of the light radiated from the illumination unit 10c and the normal direction of a point P are projected on the XZ plane. It is a figure which shows the relationship between the traveling direction and the normal direction when the traveling direction of the light radiated from the illumination unit 10c and the normal direction of a point P are projected on the YZ plane. It is a figure which shows the relationship between Ny, φx, and φy when the glossiness α = 5. It is a figure which shows the relationship between Ny, φx, and φy when the glossiness α = 10. It is a figure which shows the relationship between Ny, φx, and φy when the glossiness α = 20. It is a figure which shows the relationship between the albedo μ, φx, and φy when the glossiness α = 5. It is a figure which shows the relationship between the albedo μ, φx, and φy when the glossiness α = 10. It is a figure which shows the relationship between the albedo μ, φx, and φy when the glossiness α = 20. It is a figure which shows the process performed with respect to the X-direction normal image for generating a shape image. It is a figure which shows the process performed with respect to the Y direction normal image for generating a shape image. It is a figure which shows the polarized image obtained by taking an image of a button battery, and various images generated from a polarized image. It is a figure which shows the polarized image obtained by photographing the side surface of the dry cell, and various images generated from the polarized image. It is a figure which shows the polarized image obtained by imaging the bottom surface of a dry cell, and various images generated from the polarized image. It is a figure which shows the polarized image obtained by image | imaging the textured resin surface, and various images generated from the polarized image. It is a figure which shows the arrangement of the plurality of lighting parts which concerns on the 2nd inspection example. It is a figure which shows the structure of the illumination part 10e. It is a figure which shows an example of the plurality of polarized images obtained in the 2nd inspection example. It is a figure which shows an example of the arrangement of the plurality of lighting parts which concerns on 3rd inspection example. It is a figure which shows the amount of the light which is irradiated from the illumination part 10e, 10g-10i and is specularly reflected by the object W, and is transmitted through each polarizing element. It is a figure which shows another example of arrangement of the plurality of lighting parts which concerns on 3rd inspection example. It is a figure which shows the amount of the light which is irradiated from the illuminating part 10e, 10g-10l and is specularly reflected by the object W, and is transmitted through each polarizing element. It is a figure which shows an example of the polarized image 50a to 50d obtained by using the plurality of illumination units shown in FIG. 26. FIG. 28 is a diagram showing an example of polarized images 50a to 50d obtained by using a plurality of illumination units shown in FIG. 28. It is a figure which shows the arrangement of the plurality of lighting parts which concerns on 4th inspection example. It is a figure which shows an example of the plurality of polarized images obtained in the 4th inspection example. It is a figure which shows the arrangement of the plurality of lighting parts which concerns on 5th inspection example. It is a figure which shows an example of the plurality of polarized images obtained in the 5th inspection example.

An embodiment of the present invention will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals and the description thereof will not be repeated.

§1 Application example An application example of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic view showing the overall configuration of the inspection system 1 according to the present embodiment. The inspection system 1 inspects the object W by 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 in, for example, a production line, and inspects the moving object W for defects by a transport belt 2.

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 stand out in the image. The lighting conditions that make the defective part stand out differ depending on the type of defect. Therefore, when it is desired to inspect a plurality of types of defects, a plurality of images captured under a plurality of lighting conditions are required. Alternatively, a defective portion may be conspicuous in an image obtained by synthesizing a plurality of images captured under a plurality of illumination conditions. Even when it is desired to inspect such a defect, a plurality of images captured under a plurality of illumination conditions are required. The inspection system 1 shown in FIG. 1 acquires a plurality of images corresponding to a plurality of lighting conditions for a moving object W by one imaging (one-shot imaging), and acquires a plurality of acquired images. Inspect the object W using.

As shown in FIG. 1, the inspection system 1 includes a plurality of lighting units 10 for illuminating the object W, a polarizing camera 20, and an inspection device 30.

The plurality of lighting units 10 irradiate illumination light having different polarization states from each other. The inspection system 1 shown in FIG. 1 includes lighting units 10a, 10b, 10c, 10d, .... Hereinafter, when the illumination units 10a, 10b, 10c, 10d, ... Are not particularly distinguished, each of the illumination units 10a, 10b, 10c, 10d, ... Is described as "illumination unit 10".

Typically, each of the plurality of illumination units 10 includes a light emitting unit that emits non-polarized light and a linear polarization filter arranged between the light emitting unit and the object W. The polarization directions of the light transmitted through the linear polarization filter are different from each other in the plurality of illumination units 10. It should be noted that one of the plurality of illumination units 10 does not have to include a linear polarization filter. In this case, one lighting unit 10 irradiates the object W with non-polarized light.

The polarizing camera 20 has a plurality of light detection sensors arranged in a matrix, and image data having a light receiving amount (luminance) detected by the light detection sensor as a pixel value (hereinafter, simply referred to as “image”). To generate. The size of multiple photodetectors is the same. The photodetection sensor is, for example, a CCD (Coupled Charged Device) or CMOS (Complementary Metal Oxide Semiconductor) sensor. A polarizing element is provided on the light incident side of each photodetector sensor.

FIG. 2 is a diagram showing an example of the arrangement of the polarizing elements of the polarizing camera 20. As shown in FIG. 2, in the polarizing camera 20, the unit region 21 including the plurality of polarizing elements 22 is repeatedly arranged. The plurality of unit regions 21 are arranged in a matrix. The sizes of the plurality of polarizing elements 22 are the same.

In the polarizing camera 20 exemplified in FIG. 2, the unit region 21 includes four polarizing elements 22a to 22d overlapping with four photodetector sensors as a plurality of polarizing elements 22. Hereinafter, when the splitters 22a to 22d are not particularly distinguished, each of the splitters 22a to 22d is referred to as a "polarizer 22".

Each of the stators 22a to 22d transmits linearly polarized light in a predetermined polarization direction. Assuming that the polarization direction of the splitter 22a is the reference direction and the angle formed by the reference direction and the polarization direction is the polarization angle, the polarization angles of the splitters 22a to 22d are 0 °, 45 °, 90 °, and 135 °, respectively. .. The polarization angle may include manufacturing errors, mounting errors, and the like. For example, if the maximum sum of manufacturing and mounting errors is β °, the “polarization angle 45 °” includes the range 45 ° ± β °.

The polarizing camera 20 outputs a plurality of polarized images 50 (see FIG. 1) corresponding to the plurality of polarizing elements 22 by taking an image in a state where the plurality of lighting units 10 are lit at the same time. In the inspection system 1 shown in FIG. 1, the plurality of polarized images 50 include polarized images 50a, 50b, 50c, 50d, .... Hereinafter, when the polarized images 50a, 50b, 50c, 50d, ... Are not particularly distinguished, each of the polarized images 50a, 50b, 50c, 50d, ... Is described as "polarized image 50".

Each pixel value of the plurality of polarized images 50 indicates the brightness of the light transmitted through the corresponding polarizing element 22 among the plurality of polarizing elements 22. For example, when the polarizing camera 20 has the configuration shown in FIG. 2, the polarized images 50a, 50b, 50c, and 50d corresponding to the splitters 22a to 22d are output.

The inspection device 30 inspects the object W using a plurality of polarized images 50 received from the polarizing camera 20.

Each of the plurality of polarizing elements 22 transmits more illumination light from the illumination unit 10 that irradiates linearly polarized light having the smallest angle with the polarization direction of the polarizing element 22 among the plurality of illumination units 10.

For example, a case where the polarization direction of the splitter 22a and the polarization direction of the illumination unit 10a are parallel, and the polarization direction of the splitter 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 transducers 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 polarizing element 22a but does not pass through the polarizing element 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 polarizing element 22a, but passes through the polarizing element 22c. Therefore, in the polarized image 50a corresponding to the polarizing element 22a, the light of the illumination unit 10a is imaged so as to be the strongest. In the polarized image 50c corresponding to the polarizing element 22c, the light of the illumination unit 10c is imaged so as to be the strongest.

In this way, each of the plurality of polarized images 50 is imaged so that the light of the illumination unit 10 that irradiates the linearly polarized light having the smallest angle with the polarization direction of the corresponding polarizing element 22 becomes the strongest. That is, a plurality of polarized images 50 corresponding to a plurality of lighting conditions are acquired by one-shot imaging. Therefore, the moving object W can be inspected by using a plurality of polarized images 50 having different illumination conditions.

§2 Specific example <A. Hardware configuration of inspection equipment>
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 that follows a general-purpose computer architecture, and a processor executes a pre-installed program to perform various processes as described later. To realize.

More specifically, the inspection device 30 includes a processor 310 such as a CPU (Central Processing Unit) and an MPU (Micro-Processing Unit), a RAM (Random Access Memory) 312, a display controller 314, and a system controller 316. It includes 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. Each of these parts is connected to each other so as to be capable of data communication, centering on the system controller 316.

The processor 310 realizes the target arithmetic processing by exchanging programs (codes) and the like with the system controller 316 and executing them in a predetermined order.

The system controller 316 is connected to the processor 310, RAM 312, display controller 314, and I / O controller 318 via a bus, and exchanges data with each part and processes the entire inspection device 30. Control.

The RAM 312 is typically a volatile storage device such as a DRAM (Dynamic Random Access Memory), with respect to a program read from a hard disk 320, a polarized image 50 acquired by a polarized camera 20, and a polarized image 50. Holds processing results and so on.

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 an internal command from the system controller 316. The display unit 302 includes, for example, a liquid crystal display, an organic EL (Electro Luminescence) display, an organic EL, and the like.

The I / O controller 318 controls data exchange with a recording medium or an external device connected to the inspection device 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.

The hard disk 320 is typically a non-volatile magnetic storage device that stores the inspection program 350 executed by the processor 310. The inspection program 350 installed on the hard disk 320 is distributed in a state of being stored in a memory card 306 or the like. Further, a camera image is stored in the hard disk 320. 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 adopted.

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

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

The communication interface 328 mediates data transmission between the processor 310 and another personal computer, server device, or the like (not shown). The communication interface 328 typically comprises Ethernet (registered trademark), USB (Universal Serial Bus), or the like. As will be described later, instead of installing the program stored in the memory card 306 in the inspection device 30, the program downloaded from the distribution server or the like may be installed in the inspection device 30 via the communication interface 328. good.

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 is distributed in a state in which the inspection program 350 or the like executed by the inspection device 30 is stored, and the memory card interface 330 reads the inspection program 350 from the memory card 306. The memory card 306 is a general-purpose semiconductor storage device such as SD (Secure Digital), a magnetic recording medium such as a flexible disk (Flexible Disk), or an optical recording medium such as a CD-ROM (Compact Disk Read Only Memory). Etc.

<B. Inspection example>
As described above, the optimum lighting conditions differ depending on the type of defect to be inspected. Therefore, the positions, illumination intensities, polarization directions, and the like of the plurality of illumination units 10 are appropriately set according to the type of defect to be inspected. The first to fifth inspection examples using the inspection system 1 according to the present embodiment will be described below. The inspection system 1 is not limited to the following first to fifth inspection examples, and may be used for other inspection examples.

(B-1. First inspection example)
In the first inspection example, a photometric stereo method (illuminance difference stereo method) is used. The photometric stereo method is a method of estimating the inclination (normal vector) of the surface of an object by using a plurality of images obtained under conditions where the incident direction of the illumination light is different.

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

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 can be obtained. However, since the imaging is performed four times, the lighting device 110 shown in FIG. 4 cannot be applied to the moving object W. Therefore, the inspection system 1 according to the present embodiment acquires a plurality of images used in the photometric stereo method by one-shot imaging in the first inspection example.

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

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

The illumination units 10a to 10d have light emitting units 11a to 11d and linear polarizing filters 12a to 12d, respectively.

The light emitting units 11a to 11d emit unpolarized light. Each of the light emitting portions 11a to 11d has an arc shape with a central angle of 90 °. The arc-shaped light emitting portions 11a to 11d are arranged so that their centers coincide with each other and do not overlap with each other. Specifically, one end of the light emitting portions 11a to 11d is in contact with the other ends of the light emitting portions 11b to 11d and 11a, respectively. That is, one ring-shaped illumination is configured by combining the light emitting units 11a to 11d. In other words, the light emitting units 11a to 11d are four arc regions having a central angle of 90 ° in one ring-shaped illumination. The center of the arc-shaped light emitting portions 11a to 11d is located on the optical axis 25 of the polarizing camera 20.

The linear polarizing filters 12a to 12d are attached to the light emitting surfaces of the light emitting units 11a to 11d, respectively.

FIG. 6 is a diagram showing an example of the polarization direction of the linear polarization filters 12a to 12d. Assuming that the polarization direction of the light transmitted through the linear polarization filter 12a is the reference direction and the angle formed by the reference direction and the polarization direction is the polarization angle, the polarization angles of the linear polarization filters 12a to 12d are 0 °, 45 °, and 90, respectively. °, 135 °. The polarization angle may include manufacturing errors, mounting errors, and the like. For example, if the maximum sum of manufacturing and mounting errors is β °, the “polarization angle 45 °” includes the range 45 ° ± β °. As described above, the angles formed by the polarization direction of the illumination light of the illumination units 10b to 10d and the polarization direction of the illumination light of the illumination unit 10a are 45 °, 90 °, and 135 °, respectively.

In the first inspection example, the inspection system 1 includes a polarizing camera 20 including the polarizing elements 22a to 22d shown in FIG. The polarization directions of the splitters 22a to 22d are parallel to the polarization directions of the linear polarization filters 12a to 12d, respectively. Therefore, the light emitted from the illumination units 10a to 10d and specularly reflected by the object W passes through the polarizing elements 22a to 22d, respectively. The light emitted from the illumination unit 10a has components parallel to the polarization directions of the splitters 22b and 22d. Therefore, some of the components of the light that is irradiated from the illumination unit 10a and specularly reflected by the object W pass through the splitters 22b and 22d. Specifically, the amount of light emitted from the illumination unit 10a and transmitted through each of the polarizing elements 22b and 22d is about ½ of the amount of light emitted from the illumination unit 10a and transmitted through the splitter 22a. Similarly, some of the components of the light emitted from the illumination unit 10b and specularly reflected by the object W pass through the stators 22a and 22c. Some of the components of the light emitted from the illumination unit 10c and specularly reflected by the object W pass through the transducers 22b and 22d. Some of the components of the light emitted from the illumination unit 10d and specularly reflected by the object W pass through the stators 22a and 22c.

(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 polarizing camera 20 takes an image of the object W in a state where the illumination units 10a to 10d are lit at the same time, and outputs polarized images 50a to 50d corresponding to the polarizing elements 22a to 22d (step S1). After step S1, the inspection system 1 starts steps S2, S3, S10 in parallel.

In step S2, the processor 310 of the inspection device 30 uses the polarized images 50a to 50d to generate 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. .. Similarly, in step S3, the processor 310 uses the polarized images 50a to 50d to generate a Y-direction normal image showing the magnitude of the Y-direction component in the normal vector of the surface of the object W. Details of the X-direction normal image and the method of generating the X-direction normal image will be described later.

After step S2 and step S3, steps S4 and S5 are carried out, respectively. In steps S2 and S3, as will be described later, an X-direction normal image and a Y-direction normal image are generated on the assumption that the glossiness α on the surface of the object W is 1. However, the glossiness α on the surface of the object W is not always 1. The ratio of the specularly reflected component of the incident light differs depending on the glossiness α. 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 method for the X-direction normal image and the Y-direction normal image will be described later.

After step S4 and step S5, the processor 310 starts steps S6 and S8 in parallel.

In step S6, the processor 310 generates a shape image showing 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 shape image generation method will be described later.

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 for uneven defects such as scratches and dents. In step S7, the processor 310 may generate a binary image by binarizing the shape image and inspect the presence or absence of defects based on the binary image.

In step S8, the processor 310 generates an albedo image showing the ratio of specularly reflected light (albedo (reflectance)) to the incident light. The albedo image is generated using the polarized images 50a to 50d, and the X-direction normal image and the Y-direction normal image corrected by steps S4 and S5, respectively. Details of the albedo image generation method will be described later.

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

In step S10, the processor 310 generates an average image by averaging the polarized images 50a to 50d. The value of each pixel of the average image is the average value of the values of the pixels of the polarized 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 taking an image using a non-polarized camera instead of the polarized camera 20.

Next, in step S11, the processor 310 positions the object W using the average image.

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

(How to generate an X-direction normal image and an X-direction normal image)
FIG. 8 is a diagram showing the relationship between the illumination units 10a to 10d and the normal vector n at the point P on the surface of the object W. In FIG. 8, the optical axis 25 of the polarizing 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, the Y component, and the Z component of the normal vector n, respectively.

FIG. 9 is a diagram showing the relationship between the traveling direction and the normal direction when the traveling direction of the light emitted from the illumination unit 10c and the normal direction of the point P are projected onto the XZ plane. In FIG. 9, the normal direction is represented by a vector (nx, nz). Assuming that the angle formed by the normal direction and the Z axis is φx, φx is expressed by the following equation. φx = arctan (nx / nz)
Further, assuming that the incident angles of the light emitted from each of the illumination units 10a to 10d are θ, nx> 0 and nz> 0, the traveling direction (specular reflection) of the light emitted from the illumination unit 10c and specularly reflected at the point P. The angle formed by the projection component of the direction) on the XZ plane and the Z axis is θ + 2φx.

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

Similarly, the angles formed by the projection component on the XZ plane and the Z axis in the traveling direction (specular reflection direction) of the light irradiated from the illumination units 10a, 10b, 10d and specularly reflected at the point P are θ-2φx, respectively. , 2φx, 2φx. The angles formed by the projection component on the YZ plane and the Z axis in the traveling direction (specular reflection direction) of the light emitted from the illumination units 10a, 10b, and 10d and specularly reflected at the point P are 2φy, θ-2φy, and θ + 2φy, respectively. It becomes.

Of the light emitted from the illumination units 10a to 10d and specularly reflected at the point P, the intensities Ia to Id of the light incident on the polarizing camera 20 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 glossiness. μ represents an albedo (reflectance) on the surface of the object W.

As described above, the polarization direction of the polarizing element 22a of the polarizing camera 20 is parallel to the polarization direction of the illumination unit 10a and orthogonal to the polarization direction of the illumination unit 10c. Further, the angle formed by the polarization direction of the polarizing element 22a and the polarization direction of the illumination units 10b and 10d is 45 °. Therefore, assuming that the pixel value of the polarized image 50a corresponding to the polarizing element 22a is Ja,
Ja = Ia + (Ib + Id) / 2
It is represented by. Similarly, the respective pixel values Jb to Jd of the polarized images 50b to 50d are
Jb = Ib + (Ia + Ic) / 2
Jc = Ic + (Id + Ib) / 2
Jd = Id + (Ic + Ia) / 2
It is represented by.

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

The following equation (4) is derived from the above equations (1) and (2). Similarly, the following equation (5) is derived from the above equations (1) and (3).
tan (2φx) = {4 (Ja-Jc)} / {(Ja + Jb + Jc + Jd) tan (θ)}
... Equation (4)
tan (2φy) = {4 (Jb-Jd)} / {(Ja + Jb + Jc + Jd) tan (θ)}
... Equation (5).

In the formulas (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 the equation (4) using the pixel values of the polarized images 50b to 50d and the incident angle θ, and generates an X-direction normal image having Nx as the pixel value as the result. .. Similarly, the processor 310 calculates the right side of the equation (5) using the pixel values of the polarized images 50b to 50d and the incident angle θ, and generates a Y-direction normal image having Ny as the pixel value as a result. do. Tan (2φx) (≡Nx) represented by the equation (4) is a value depending on nx, which is a component in the x direction of the normal vector. Tan (2φx) (≡Ny) represented by the equation (5) is a value depending on ny, which is a component in the y direction 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.

(Correction method for X-direction normal image and Y-direction normal image)
The X-direction normal image and the Y-direction normal image are generated according to the equations (4) and (5), respectively, assuming that the glossiness α of the surface of the object W is 1. Therefore, the correction of the X-direction normal image and the Y-direction normal image is executed according to the glossiness α of the object W. As a result, a normal image corresponding to the glossiness α is generated with high accuracy.

The glossiness α of the object W is determined in advance according to the following pre-inspection procedure. In the pre-inspection procedure, the defect-free object W is placed on the 2-axis goniometer stage. The biaxial goniometer stage is a stage that can be tilted in the X and Y directions.

When the inclination angles of the biaxial goniometer stage in the X and Y directions are set to 0 °, the object W has a horizontal and flat upper surface (hereinafter referred to as “target area”). It will be placed on the 2-axis goniometer stage. 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 inclination angle of the biaxial goniometer stage in the X-direction. 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 of the biaxial goniometer stage in the Y-direction.

While changing the tilt angle of the 2-axis goniometer stage in the X and Y directions, image is taken M times using the inspection system 1. An X-direction normal image and a Y-direction normal image are generated for each of the M times of imaging. The processor 310 stores the data set [φxm, φym, Nxm, Nym] in the RAM 312 for any one pixel in the target area in the X-direction normal image and the Y-direction normal image. m indicates an imaging number and is an integer of 1 to M. φxm is the tilt angle of the biaxial goniometer stage in the X direction in the mth imaging. φym is the tilt angle of the biaxial goniometer stage in the Y direction in the mth imaging. Nxm is a pixel value of an X-direction normal image. Nym is a pixel value of a Y-direction normal image.

The processor 310 uses the following theoretical formula to determine the gloss α that best fits the data set [φxm, φym, Nxm, Nym] stored in the RAM 312.
≪Theoretical formula≫
Ia = cos ^α (θ-2φxm) cos ^α (2φym)
Ib = cos ^α (2φxm) ^cosα (θ-2φym)
Ic = cos ^α (θ + 2φxm) cos ^α (2φym)
Id = cos ^α (2φxm) ^cosα (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 uses a nonlinear least squares method to determine the gloss α. By such a pre-inspection procedure, the glossiness α of the object W is predetermined.

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.

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

Specifically, the processor 310 back-calculates (φx, φy) from (Nx, Ny) using the above theoretical formula to which the predetermined glossiness α is substituted. 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.

Alternatively, the processor 310 selects one look-up table corresponding to the glossiness α from the look-up table group created in advance, and uses the selected look-up table to set (Nx, Ny) to (φx, Ny). It may be converted to φy). The look-up table is pre-created using the above theoretical formula to which the corresponding gloss α is substituted. By using the look-up table, the time required for the correction process of the normal image is shortened.

(How to generate an albedo image)
When the glossiness α = 1 on 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).

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

As shown in FIGS. 14 to 16, the relationship between albedo μ and φx and φy shows a monotonous change. However, when the glossiness α is close to 1, the relationship between the albedo μ and φx and φy is linear, whereas when the glossiness α is large, the relationship between the albedo μ and φx and φy becomes non-linear. Therefore, the processor 310 has the pixel values φx and φy of the X-direction normal image and the Y-direction normal image corrected according to the gloss α, and the pixel values Ja of each of the polarized images 50a to 50d. By substituting ~ Jd into the above equation, an albed image is generated. Each pixel value of the albedo image indicates albedo μ.

(Method of generating 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.

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

The processor 310 selects one point surrounded by four pixels in the X-direction normal image as the point of interest Q. The lateral 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 side and the right side 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.

The processor 310 calculates the sum Sx1 of the values of the pixels included in the rectangular area R1. Similarly, the processor 310 calculates the sum Sx2 of the values of the pixels 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 the four pixels in the X-direction normal image.

FIG. 18 is a diagram showing a process executed for a Y-direction normal image for generating a shape image. The pixel value of the Y-direction normal image indicates the magnitude of the Y-direction component of the normal vector on the surface of the object W.

The processor 310 selects one point surrounded by four pixels in the Y-direction normal image as the point of interest 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 on the upper side and the lower side of the point of interest 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.

The processor 310 calculates Sy1 of the value of the pixel included in the rectangular area R3. Similarly, the processor 310 calculates Sy2, which is the value of the pixel 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 the four pixels in the Y-direction normal image.

When a defect such as a scratch or a dent is present on the surface of the object W, the normal vector changes significantly in the defect. The difference Sx increases as the X-direction component of the normal vector changes significantly. The difference Sy increases as the Y-direction component of the normal vector changes significantly. That is, the difference Sx and Sy take a large value in a place where a defect having unevenness such as a scratch or a dent is present. Therefore, the processor 310 generates a shape image having S as a pixel value obtained by the following equation.
S = A (Sx + Sy) + B
A is a parameter for determining the contrast of the shape image. B is a parameter for determining the level of the overall pixel value of the shape image. The processor 310 sets the values of the parameters A and B so that the maximum and minimum of the pixel values in the shape image and the difference between the maximum and the minimum are within the specified range. The defined range is predetermined according to the contrast and level suitable for defect inspection. As a result, a shape image suitable for inspection of defects having irregularities is generated.

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

In FIG. 19, there are dents in the area surrounded by the frame line F1 on the surface of the button battery. Further, there is dirt in the area 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 the pixel value according to the dented portion is observed in the frame line F1. In the binary image 54, the dented portion is represented by white. Thereby, by using the shape image 53 or the binary image 54, defects having irregularities such as scratches or dents are inspected with high accuracy. Also in the X-direction normal image 51 and the Y-direction normal image 52, the pixel values are different between the dented portion and its surroundings. Therefore, even if the X-direction normal image 51 and the Y-direction normal image 52 are used, defects having irregularities can be inspected.

In the X-direction normal image 51, the Y-direction normal image 52, the shape image 53, and the binary image 54, there is no change in the pixel value between the dirty portion and its surroundings. This is because the unevenness does not change due to dirt. On the other hand, in the albedo image 55, a change in the pixel value according to the stain is observed in the frame line F2. This is because the albedo (reflectance) has changed due to dirt. In this way, by using the albedo image 55, defects that cause changes in the albedo (reflectance), such as stains, are accurately inspected.

FIG. 20 is a diagram showing a polarized image obtained by imaging the side surface of a dry cell and various images generated from the polarized image. 20 shows the polarized images 50a to 50d, the X-direction normal image 51, the Y-direction normal image 52, and the average image 56 generated from the polarized images 50a to 50d, and the X-direction normal image 51 and the Y-direction method. The shape image 53 and the binary image 54 generated from the line image 52 are shown. In FIG. 20, there are dents in the region surrounded by the frame line F1 on the side surface of the dry cell. In the shape image 53, a change in the pixel value according to the dented portion is observed in the frame line F1. In the binary image 54, the dented portion is represented by white. Thereby, by using the shape image 53 or the binary image 54, defects having irregularities such as scratches or dents are inspected with high accuracy.

FIG. 21 is a diagram showing a polarized image obtained by imaging the bottom surface of a dry cell and various images generated from the polarized image. In FIG. 21, the polarized images 50a to 50d, the X-direction normal image 51, the Y-direction normal image 52, and the average image 56 generated from the polarized images 50a to 50d, the X-direction normal image 51, and the Y-direction method are shown. The shape image 53 generated from the line image 52 is shown. In FIG. 21, there are dents in the region surrounded by the frame line F1 on the bottom surface of the dry cell. In the shape image 53, a change in the pixel value according to the dented portion is observed in the frame line F1. As a result, by using the shape image 53, defects with irregularities such as scratches or dents can be inspected with high accuracy.

FIG. 22 is a diagram showing a polarized image obtained by imaging the textured resin surface and various images generated from the polarized image. In FIG. 22, the polarized images 50a to 50d, the X-direction normal image 51, the Y-direction normal image 52, and the average image 56 generated from the polarized images 50a to 50d, the X-direction normal image 51, and the Y-direction method are shown. The shape image 53 and the binary image 54 generated from the line image 52 are shown. In FIG. 22, dents are present in the region surrounded by the frame line F1 on the resin surface. Further, there is dirt in the region surrounded by the frame line F2 on the resin surface.

As shown in FIG. 22, in the shape image 53, a change in the pixel value according to the dented portion is observed in the frame line F1. In the binary image 54, the dented portion is represented by white. Thereby, by using the shape image 53 or the binary image 54, defects having irregularities such as scratches or dents are inspected with high accuracy.

In the X-direction normal image 51, the Y-direction normal image 52, the shape image 53, and the binary image 54, there is no change in the pixel value between the dirty portion and its surroundings. This is because the unevenness does not change due to dirt. On the other hand, in the average image 56, a change in the pixel value according to the dirty portion is observed in the frame line F2. This is because the albedo (reflectance) has increased due to dirt. As described above, even if the average image 56 is used, defects such as stains that cause changes in the albedo (reflectance) are accurately inspected.

(B-2. Second inspection example)
In the second inspection example, two images obtained under the conditions of bright-field illumination and dark-field illumination are used. Bright-field illumination is an illumination method in which specularly reflected light on the surface of the object W is incident on the polarizing camera 20. The dark field illumination is an illumination method in which the specularly reflected light on the surface of the object W does not enter the polarized camera 20 and only the diffuse reflected light is incident on the polarized camera 20. Light is difficult to specularly reflect in areas with scratches. Therefore, in the image obtained under the condition of bright field illumination, the brightness of the portion where the scratch is present is lowered. As a result, scratches can be inspected with high accuracy by using the image obtained under the condition of bright field illumination. On the other hand, it is easy to diffuse and reflect in the part where dirt or foreign matter is present. Therefore, in the image obtained under the condition of dark field illumination, the brightness of the portion where dirt or foreign matter is present becomes high. Thereby, by using the image obtained under the condition of dark field illumination, dirt or foreign matter can be inspected with high accuracy.

(Arrangement of 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 include the lighting units 10e and 10f. The illumination units 10e and 10f are arranged so that the elevation angles with respect to the object W are different from each other.

The lighting unit 10f is a ring-shaped lighting unit centered on the optical axis 25 of the polarizing camera 20. The illumination unit 10f has a ring-shaped light emitting unit 11f centered on the optical axis 25 of the polarizing camera 20, and a linear polarizing filter 12f attached to the light emitting surface of the light emitting unit 11f. The elevation angle of the illumination unit 10f with respect to the object W is set so that the specularly reflected light of the object W does not enter the polarizing camera 20.

FIG. 24 is a diagram showing the configuration of the lighting unit 10e. The illumination unit 10e is coaxial illumination that irradiates the object W with illumination light along the optical axis 25 of the polarizing 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 arranged between the light emitting surface of the light emitting unit 11e and the half mirror 13e, and transmits linear polarization along a predetermined direction among the unpolarized light emitted from the light emitting unit 11e. The half mirror 13e shoots linearly polarized light transmitted through the linear polarization filter 12e along the optical axis 25 of the polarizing camera 20.

The linear polarization filters 12e and 12f are arranged so that the polarization directions of the linear polarizations irradiated to the object W from the illumination units 10e and 10f are orthogonal to each other.

(Inspection methods)
In the second inspection example, the inspection system 1 includes a polarizing camera 20 including the splitters 22a to 22d shown in FIG. The polarization direction of the polarizing element 22a coincides with (parallel to) the polarization direction of the linearly polarized light radiated to the object W from the illumination unit 10e. The polarization direction of the polarizing element 22c coincides with (parallel to) the polarization direction of the linearly polarized light emitted from the illumination unit 10f. Therefore, the light irradiated from the illumination unit 10e and specularly reflected by the object W passes through the polarizing element 22a and does not pass through the polarizing element 22c. A part of the light emitted from the illumination unit 10f and diffusely reflected by the object W passes through the polarizing element 22c. The light emitted from the illumination unit 10f and specularly reflected by the object W does not enter the polarizing camera 20.

FIG. 25 is a diagram showing an example of a plurality of polarized images obtained in the second inspection example. The polarized images 50a to 50d correspond to the polarizing elements 22a to 22d, respectively.

The polarized image 50a shows the brightness of the light emitted from the illumination unit 10e and specularly 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 are easily confirmed in the frame line F1 of the polarized image 50a. In this way, by using the polarized image 50a, scratches can be inspected with high accuracy.

The polarized image 50c shows the brightness of the light transmitted from the polarizing element 22c among the light diffusely reflected by the object W, which is irradiated from the illumination unit 10f. That is, the polarized image 50c corresponds to an image obtained by imaging under the condition of dark field illumination. Therefore, dirt is easily confirmed in the frame line F2 of the polarized image 50c. In this way, by using the polarized image 50c, stains are inspected with high accuracy.

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

(B-3. Third inspection example)
The third inspection example uses a phase shift method. The phase shift method is a method of measuring the three-dimensional shape of an object W from a plurality of images captured by irradiating a striped pattern whose irradiation intensity is modulated into a sine wave while shifting the phase.

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

Each of the lighting units 10g to 10i is a ring type lighting. The illumination units 10g to 10i have a ring-shaped light emitting unit 11g to 11i centered on the optical axis 25 of the polarizing camera 20, and a linear polarizing filter 12g to 12i attached to the light emitting surface of the light emitting unit, respectively.

When the polarization direction of the light emitted from the illumination unit 10e is set as the reference direction, the linear polarization filters 12e, 12g to 12i form an angle between the polarization direction of the light emitted from the illumination unit 10e, 10g to 10i and the reference direction. Are arranged so as to be 0 °, 45 °, 90 °, and 135 °, respectively.

The lighting units 10e and 10g to 10i are arranged so that the elevation angles with respect to the object W are different from each other. Specifically, the illumination units 10e and 10g to 10i are arranged so that the elevation angle becomes smaller in this order with respect to the object W. In other words, the incident angle of the illumination light from the illumination unit 10e, 10g to 10i to the object W increases 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 °.

In the third inspection example, the inspection system 1 includes a polarizing camera 20 including the polarizing elements 22a to 22d shown in FIG. The polarization directions of the extruders 22a to 22d are parallel to the polarization directions of the light emitted from the illumination units 10e and 10g to 10i, respectively. Therefore, the light emitted from the illumination units 10e and 10g to 10i and specularly reflected by the object W passes through the polarizing elements 22a to 22d, respectively. The light emitted from the illumination unit 10e has components parallel to the polarization directions of the splitters 22b and 22d. Therefore, some of the components of the light that is irradiated from the illumination unit 10e and specularly reflected by the object W pass through the splitters 22b and 22d. Specifically, the amount of light emitted from the illumination unit 10e and transmitted through each of the splitters 22b and 22d is about ½ of the amount of light emitted from the illumination unit 10e and transmitted through the splitter 22a. Similarly, a part of the light that is irradiated from the illumination unit 10g and is specularly reflected by the object W passes through the polarizing elements 22a and 22c. Some of the components of the light that is radiated from the illumination unit 10h and specularly reflected by the object W pass through the substituents 22b and 22d. Some of the components of the light emitted from the illumination unit 10i and specularly reflected by the object W pass through the stators 22a and 22c. The light emitted from the illumination units 10e, 10g to 10i and specularly reflected by the object W does not pass through the polarizing elements 22c, 22d, 22a, and 22b, respectively.

FIG. 27 is a diagram showing the amount of light that is radiated from the illumination units 10e, 10g to 10i and is specularly reflected by the object W and that passes through each polarizing element. As shown in FIG. 27, the amount of light transmitted through each of the transducers 22a to 22d follows a sine wave. That is, the polarized images 50a to 50d corresponding to the splitters 22a to 22d correspond to the images captured under the condition that the object W is irradiated with the light of the concentric striped pattern. Further, as shown in FIG. 27, the phases of the fringe patterns corresponding to the stators 22a to 22d are shifted by π / 2.

FIG. 28 is a diagram showing another example of the arrangement of the plurality of lighting 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 the illumination units 10j to 10l.

Each of the lighting units 10j to 10l is a ring type lighting. The illumination units 10j to 10l have ring-shaped light emitting units 11j to 11l centered on the optical axis 25 of the polarizing camera 20, and linear polarizing filters 12j to 12l attached to the light emitting surfaces of the light emitting units 11j to 11l, respectively.

When the polarization direction of the light emitted from the illumination unit 10e is set as the reference direction, the linear polarization filters 12j to 12l have an angle formed by the polarization direction and the reference direction of the light emitted from the illumination units 10j to 10l of 22. It is arranged so as to be 5 °, 67.5 °, and 110.5 °.

The lighting units 10e, 10j, 10g, 10k, 10h, 10l, and 10i are arranged so that the elevation angle becomes smaller in this order with respect to the object W. In other words, the incident angle of the illumination light from the illumination unit 10e, 10j, 10g, 10k, 10h, 10l, 10i to the object W increases in this order.

FIG. 29 is a diagram showing the amount of light that is radiated from the illumination unit 10e, 10g to 10l and is specularly reflected by the object W and that passes through each polarizing element. As shown in FIG. 29, the amount of light transmitted through each of the substituents 22a to 22d follows a sine wave. That is, the polarized images 50a to 50d corresponding to the splitters 22a to 22d correspond to the images captured under the condition that the object W is irradiated with the light of the concentric striped pattern. Further, as shown in FIG. 29, the phases of the fringe patterns corresponding to the stators 22a to 22d are shifted by π / 2.

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

The two-dimensional coordinates of the image are represented as (x, y), and the values of the pixels (x, y) in the polarized images 50a to 50d are Ja (x, y), Jb (x, y), Jc (x, y), When expressed as Jd (x, y), the phase of the pixel is
Φ (x, y) = arctan [{Jb (x, y) -Jd (x, y)} / {Ja (x, y) -Jc (x, y)}]
It is expressed as. The range of the normal angle of the object W on which the fringe 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 polarizing 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 white pixels (256) when the angle formed by the normal direction of the object W and the optical axis 25 is 0 °, and the angle formed by the normal direction of the object W and the optical axis 25. When is 45 °, it becomes a black pixel (0). Therefore, by using the phase image, the unevenness of the surface of the object W can be inspected.

Further, in the processor 310, the value of the pixel (x, y) is A (x, y) = [{Ja (x, y) -Jc (x, y)} ² + {Jb (x, y) -Jd ( x, y)} ² ] ^1/2
Generates a specular reflection image. The specular reflection image represents the intensity of light that is specularly reflected on the surface of the object W. When the object W has scratches, light may be diffusely reflected due to the fine shape of the scratches. In this case, the specular reflection component becomes relatively weak at the scratched portion. Therefore, the specular reflection image can be used to inspect the unevenness of the surface of the object W.

FIG. 30 is a diagram showing an example of polarized images 50a to 50d obtained by using the plurality of illumination units 10 shown in FIG. 26. FIG. 31 is a diagram showing an example of polarized images 50a to 50d obtained by using the plurality of illumination units 10 shown in FIG. 28. As shown in FIGS. 30 and 31, a specularly reflected fringe pattern is observed on the surface of the object W, and the phase of the fringe pattern is shifted by π / 2 in the polarized images 50a to 50d. Further, by increasing the number of the illumination units 10, the striped pattern becomes smooth. This improves the resolution in the normal direction of the surface of the object W.

It is also possible to provide only the ring-shaped illumination unit 10g to 10i (or the illumination unit 10g to 10l) without providing the illumination unit 10e which is coaxial illumination. In this case, the striped pattern relating to the central portion of the concentric circle is lost. By providing the illumination unit 10e, it is possible to reduce the loss of the stripe pattern with respect to the central portion of the concentric circles, and it is possible to perform a more accurate inspection.

(B-4. Fourth inspection example)
In the fourth inspection example, two images obtained under the conditions of coaxial illumination and backlight are used. The image obtained under the illumination condition coaxial with the optical axis 25 of the polarizing camera 20 shows the brightness of the specularly reflected light on the surface of the object W. As described above, it is difficult for light to be specularly reflected in a portion where a scratch is present. Therefore, in the image obtained under the condition of coaxial illumination, the brightness of the portion where the scratch is present is lowered. As a result, scratches can be inspected with high accuracy by using the image obtained under the condition of coaxial illumination. On the other hand, when the object W has a light-shielding property, the brightness of the region corresponding to the object W becomes 0 in the image obtained under the condition of the backlight. Therefore, the outer circumference of the object W can be easily confirmed. Thereby, by using the image obtained under the condition of the backlight, burrs or chips on the outer periphery of the object W can be inspected with high accuracy.

(Arrangement of lighting unit)
FIG. 32 is a diagram showing the arrangement of a plurality of lighting units according to the fourth inspection example. As shown in FIG. 32, the plurality of lighting units 10 include the lighting 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 polarizing camera 20 (see FIG. 24).

The lighting unit 10m is arranged as a backlight on the opposite side of the object W from the polarizing camera 20. That is, the illumination unit 10m irradiates the illumination light from the back surface side of the object W. The illumination unit 10m has a flat light emitting unit 11m and a linear polarizing filter 12m attached to the light emitting surface of the light emitting unit 11f.

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

(Inspection methods)
In the fourth inspection example, the inspection system 1 includes a polarizing camera 20 including the splitters 22a to 22d shown in FIG. The polarization direction of the polarizing element 22a coincides with (parallel to) the polarization direction of the linearly polarized light radiated to the object W from the illumination unit 10e. The polarization direction of the polarizing element 22c coincides with (parallel to) the polarization direction of the linearly polarized light emitted from the illumination unit 10m. Therefore, the light irradiated from the illumination unit 10e and specularly reflected by the object W passes through the polarizing element 22a and does not pass through the polarizing element 22c. The light emitted from the illumination unit 10m and traveling around the object W passes through the polarizing element 22c and does not pass through the polarizing element 22a.

FIG. 33 is a diagram showing an example of a plurality of polarized images obtained in the fourth inspection example. The polarized images 50a to 50d correspond to the polarizing elements 22a to 22d, respectively.

The polarized image 50a shows the brightness of the light emitted from the illumination unit 10e and specularly reflected by the object W. Therefore, it is easily confirmed that the brightness of the scratched portion is reduced in the frame line F1 of the polarized image 50a. Therefore, the processor 310 can accurately inspect scratches by using the polarized image 50a.

The polarized image 50c shows the brightness of the light emitted from the illumination unit 10m and traveling around the object W. That is, the polarized image 50c corresponds to an image obtained under backlight conditions. Therefore, burrs on the outer periphery of the object W can be easily confirmed in the frame line F3 of the polarized image 50c. Therefore, the processor 310 can accurately inspect burrs or chips on the outer periphery of the object W by using the polarized image 50c.

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

(B-5. Fifth inspection example)
The fifth inspection example uses a high dynamic range technique. The high dynamic range technique is a technique for generating an image (high dynamic range image) having a wide dynamic range with less overexposure and underexposure by synthesizing a plurality of images under different lighting intensity conditions.

(Arrangement of lighting unit)
FIG. 34 is a diagram showing the arrangement of a plurality of lighting units according to the fifth inspection example. As shown in FIG. 34, the plurality of lighting units 10 include the lighting units 10n and 10o.

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

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

It is preferable that the lighting units 10n and 10o are arranged close to each other. As a result, the irradiation directions from the illumination units 10n and 10o to the object W are substantially the same, and as will be described later, a plurality of polarized images 50 having different illumination intensities and substantially the same illumination direction are captured once. Obtained at.

(Inspection methods)
In the fifth inspection example, the inspection system 1 includes a polarizing camera 20 including the splitters 22a to 22d shown in FIG. The polarization direction of the linearly polarized light emitted from the illumination unit 10n is parallel to the polarization direction of the splitter 22a and orthogonal to the polarization direction of the polarizing element 22c. Therefore, the light irradiated from the illumination unit 10n and specularly reflected by the object W passes through the polarizing element 22a and does not pass through the polarizing element 22c. The light emitted from the illumination unit 10n and specularly reflected by the object W has components parallel to the polarization directions of the splitters 22b and 22d. Therefore, some of the components of the light that is irradiated from the illumination unit 10n and specularly reflected by the object W pass through the polarizing elements 22b and 22d. Specifically, the amount of light emitted from the illumination unit 10n and transmitted through each of the splitters 22b and 22d is about ½ of the amount of light emitted from the illumination unit 10n and transmitted through the splitter 22a.

The non-polarized light emitted from the illumination unit 10o evenly has components parallel to the polarization direction of the splitters 22a to 22d. Therefore, the amount of light emitted from the illumination unit 10o and transmitted through each of the polarizing elements 22a to 22d is the same.

The intensities of the light emitted from the illumination units 10n and 10o, specularly reflected by the object W, and transmitted through the polarizing element 22a are defined as In and Io, respectively. At this time, the pixel values Ja to Jd of the polarized images 50a to 50d corresponding to the polarizing elements 22a to 22d are represented as follows.
Pixel value Ja: In + Io of polarized image 50a
Pixel value Jb of polarized image 50b: In / 2 + Io
Pixel value of polarized image 50c Jc: Io
Pixel value of polarized image 50d Jd: In / 2 + Io
From the above, the polarized images 50a to 50c correspond to a plurality of images under conditions where the illumination intensities are different from each other. Therefore, the processor 310 synthesizes the polarized images 50a to 50c in a high dynamic range to generate a composite image. The processor 310 may generate a composite image using a known high dynamic range synthesis technique.

FIG. 35 is a diagram showing an example of a plurality of polarized images obtained in the fifth inspection example. As shown in FIG. 35, the luminance of the polarized image 50a is the highest, the luminance of the polarized image 50c is the lowest, and the luminance of the polarized images 50b and 50d is intermediate. The processor 310 synthesizes the polarized images 50a to 50c in a high dynamic range to generate the composite image 57. In the composite image 57, there are few overexposure and underexposure. Therefore, the processor 310 can inspect the object W with high accuracy by using the composite image 57.

<C. Modification example>
The number of the polarizing elements 22 included in the unit region 21 of the polarizing camera 20 is not limited to four, and may be a plurality. As described above, the polarized images 50b and 50d may not be used in the second inspection example and the fourth inspection example. Therefore, the unit region 21 may include only the splitters 22a and 22c and may not include the splitters 22b and 22d. Similarly, in the fifth inspection example, the polarized image 50d is not used. Therefore, the unit region 21 may include only the splitters 22a to 22c and may not include the splitter 22d.

In the first inspection example, the plurality of lighting units 10 may include only the lighting units 10a and 10c and may not include the lighting units 10b and 10d. In this case, the unit region 21 of the polarizing camera 20 may include only the polarizing elements 22a to 22c and may not include the polarizing elements 22d. The pixel values Ja and Jc of the polarized images 50a and 50c, respectively, are expressed 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 on 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).

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

In the 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 calculates the right side of the equation (9) using the pixel values Ja and Jc of the polarized images 50a and 50c and the incident angle θ, and the X-direction normal image having Nx as the pixel value as the result. Should be generated. Tan (2φx) (≡Nx) represented by the equation (9) is a value depending on nx, which is a component in the x direction of the normal vector. Therefore, the X-direction normal image represents the normal direction of the surface of the object W.

Further, as shown in FIG. 17, the processor 310 sets rectangular areas R1 and R2 on the left side and the right side 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 the four pixels in the X-direction normal image. The processor 310 may generate a shape image having a difference Sx as a pixel value. As described above, the difference Sx takes a large value in a place where a defect having unevenness such as a scratch or a dent is present. Therefore, the processor 310 can accurately inspect defects having irregularities by using the shape image.

In the first inspection example, it was assumed that the X-direction normal image and the Y-direction normal image were generated by using the above equations (4) and (5), respectively. However, the method of generating a normal image is not limited to this. For example, a learning model for estimating a normal image from a plurality of polarized images is constructed using a deep learning image generation technique. The processor 310 may generate a normal image from a plurality of polarized images using the learning model.

§3 Addendum As described above, this embodiment includes the following disclosures.

(Structure 1)
Inspection system (1)
A plurality of lighting units (10, 10a to 10o) that illuminate the object (W), and
A polarizing camera (20) in which a unit region (21) including a plurality of polarizing elements (22, 22a to 22d) is repeatedly arranged, and a polarizing camera (20).
Equipped with an inspection device (30)
The plurality of lighting units (10, 10a to 10o) irradiate illumination light having different polarization states from each other.
The plurality of polarizing elements (22, 22a to 22d) transmit light in different polarization directions from each other.
The polarizing camera (20) corresponds to each of the plurality of polarizing elements (22, 22a to 22d) by taking an image in a state where the plurality of lighting units (10, 10a to 10o) are lit at the same time. The polarized image (50, 50a to 50d) of
The inspection system (1) inspects the object (W) using the plurality of polarized images (50, 50a to 50d).

(Structure 2)
The plurality of lighting units are arranged so that the azimuth angles around the optical axis (25) of the polarizing camera (20) are different from each other.
The plurality of lighting units include first to Nth lighting units (10a to 10d).
The plurality of splitters include first to Nth substituents (22a to 22d).
N is an integer greater than or equal to 2 and
The polarization directions of the illumination light of the first to Nth illumination units (10a to 10d) are parallel to the polarization directions of the light transmitted through the first to Nth modulators (22a to 22d), respectively.
The inspection device (30) generates a normal image (51, 52) showing the normal direction of the surface of the object (W) from the plurality of polarized images (50a to 50d), and the normal image (51, 52). 51, 52) The inspection system (1) according to configuration 1, which inspects the object (W) based on the object (W).

(Structure 3)
N is 4
The first lighting unit (10a) and the third lighting unit (10c) are arranged at positions symmetrical with respect to the optical axis (25) of the polarizing camera (20).
The second lighting unit (10b) and the fourth lighting unit (10d) are arranged at positions symmetrical with respect to the optical axis (25) of the polarizing camera (20).
Around the optical axis (25) of the polarizing camera (20), a first azimuth angle in which the first illumination unit (10a) is arranged and a second azimuth in which the second illumination unit (10b) is arranged are arranged. The difference from the azimuth of is 90 °,
The plurality of polarized images include first to fourth polarized images (50a to 50b) corresponding to the first to fourth polarizing elements (22a to 22d), respectively.
The inspection device (30) is
A first indicating the size of a component along the direction of the first azimuth in the normal vector of the surface of the object (W) based on the first to fourth polarized images (50a to 50b). Generated a normal image (51) of
A second normal image showing the magnitude of a component along the direction of the second azimuth in the normal vector of the surface of the object (W) based on the first to fourth polarized images ( 52) is generated,
Based on the first normal image (51) and the second normal image (52), a shape image (53) showing 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).

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

(Structure 5)
The inspection system (1) according to the configuration 1, wherein the plurality of lighting units (10e to 10l) are arranged so that the elevation angles with respect to the object are different from each other.

(Structure 6)
The plurality of lighting units are
A first illumination unit (10e) that irradiates illumination light along the optical axis of the polarizing camera, and
A ring-shaped second illumination unit (10f) centered on the optical axis of the polarizing camera is included.
The plurality of polarizing elements include a first polarizing element (22a) and a second polarizing element (22c).
The polarization direction of the illumination light emitted from the first illuminating unit (10e) and the second illuminating unit (10f) is the same as that of the first polarizing element (22a) and the second polarizing element (22c). The inspection system (1) according to the configuration 5, which coincides with the polarization direction of the transmitted light.

(Structure 7)
The plurality of illumination units include a plurality of concentric ring-shaped illumination units (10 g to 10 l) centered on the optical axis of the polarizing camera.
The inspection device (30) is
Based on the plurality of polarized images (50a to 50d), a phase image showing an angle formed by the normal direction of the surface of the object (W) and the optical axis direction of the polarized camera is generated.
The inspection system (1) according to configuration 5, which inspects the object (W) based on the phase image.

(Structure 8)
The inspection system (1) according to configuration 7, wherein the plurality of illumination units further include an illumination unit (10e) that irradiates illumination light along the optical axis (25) of the polarizing camera (20).

(Structure 9)
The plurality of lighting units are
A first illumination unit (10e) that irradiates illumination light along the optical axis of the polarizing camera, and
A second illumination unit (10 m) that irradiates illumination light from the back surface side of the object is included.
The plurality of polarizing elements include a first polarizing element (22a) and a second polarizing element (22c).
The polarization direction of the illumination light emitted from the first illuminating unit (10e) and the second illuminating unit (10 m) is the same as that of the first polarizing element (22a) and the second polarizing element (22c). The inspection system (1) according to configuration 1, which coincides with the polarization direction of the transmitted light.

(Structure 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 illumination.
The plurality of substituents are
A first polarizing element (22a) that transmits light in the same polarization direction as the polarization direction of the illumination light of the first illumination unit (10n).
A second polarizing element (22b) that transmits light in a polarization direction having an angle of 45 ° with the polarization direction of the light transmitted through the first polarizing element (22a).
A third polarizing element (22c) that transmits light in a polarization direction having an angle of 90 ° with respect to the polarization direction of the light transmitted through the first polarizing element (22a) is included.
The plurality of polarized images include first to third polarized images (55a to 55c) corresponding to the first to third polarizing elements (22a to 22c), respectively.
The inspection device (30) is
The first to third polarized images (55a to 55c) are synthesized in a high dynamic range to generate a composite image.
The inspection system (1) according to configuration 1, which inspects the object (W) based on the composite image.

(Structure 11)
A polarizing camera (20) in which a plurality of lighting units (10, 10a to 10o) for illuminating an object (W) and a unit region (21) including a plurality of polarizing elements (22, 22a to 22d) are repeatedly arranged. It is an inspection method using
The plurality of lighting units (10, 10a to 10o) irradiate illumination light having different polarization states from each other.
The plurality of polarizing elements (22, 22a to 22d) transmit light in different polarization directions from each other.
The inspection method is
In a state where the plurality of lighting units (10, 10a to 10o) are lit at the same time, the object (W) is imaged by the polarizing camera (20), whereby the plurality of polarizing elements (22, A step of acquiring a plurality of polarized images (50, 50a to 50d) corresponding to 22a to 22d), respectively.
An inspection method comprising a step of inspecting the object (W) using the plurality of polarized images (50, 50a to 50d).

Although the embodiments of the present invention have been described, the embodiments disclosed this time should be considered to be exemplary in all respects and not restrictive. The scope of the present invention is indicated by the scope of claims and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 Inspection system, 2 Conveyance belt, 10, 10a to 10o Lighting unit, 11a to 11o light emitting unit, 12a to 12n linear polarization filter, 13e half mirror, 20 polarization camera, 21 unit area, 22, 22a to 22d polarizing element, 25 , 225 optical axis, 30 inspection device, 50, 50a-50d polarized image, 51 X direction normal image, 52 Y direction normal image, 53 shape image, 54 binary image, 55 albed image, 56 average image, 57 composite Image, 110 lighting device, 110a-110d arc area, 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 border, P point, Q attention point, R1 to R4 rectangular area, W object, n normal vector.

Claims (11)

1. It ’s an inspection system,
   Multiple lighting units that illuminate the object,
   A polarized camera in which unit regions containing multiple modulators are repeatedly arranged, and
   Equipped with inspection equipment,
   The plurality of lighting units irradiate illumination light having different polarization states from each other.
   The plurality of polarizing elements transmit light in different polarization directions from each other.
   The polarizing camera outputs a plurality of polarized images corresponding to the plurality of polarizing elements by taking an image in a state where the plurality of lighting units are lit at the same time.
   The inspection device is an inspection system that inspects the object using the plurality of polarized images.
2. The plurality of illumination units are arranged so that the azimuth angles around the optical axis of the polarizing camera are different from each other.
   The plurality of lighting units include the first to Nth lighting units.
   The plurality of modulators include the first to Nth substituents, and the plurality of substituents include.
   N is an integer greater than or equal to 2 and
   The polarization direction of the illumination light of the first to Nth illumination units is parallel to the polarization direction of the light transmitted through the first to Nth polarizing elements.
   The inspection according to claim 1, wherein the inspection device generates a normal image showing the normal direction of the surface of the object from the plurality of polarized images, and inspects the object based on the normal image. system.
3. N is 4
   The first lighting unit and the third lighting unit are arranged at positions symmetrical with respect to the optical axis of the polarizing camera.
   The second lighting unit and the fourth lighting unit are arranged at positions symmetrical with respect to the optical axis of the polarizing camera.
   Around the optical axis of the polarizing camera, the difference between the first azimuth in which the first illumination unit is arranged and the second azimuth in which the second illumination unit is arranged is 90 °.
   The plurality of polarized images include first to fourth polarized images corresponding to the first to fourth modulators, respectively.
   The inspection device is
   Based on the first to fourth polarized images, a first normal image showing the magnitude of a component along the direction of the first azimuth in the normal vector of the surface of the object is generated.
   Based on the first to fourth polarized images, a second normal image showing the magnitude of the component along the direction of the second azimuth in the normal vector of the surface of the object is generated.
   Based on the first normal image and the second normal image, a shape image showing the shape of the surface of the object is generated.
   The inspection system according to claim 2, wherein the object is inspected based on the shape image.
4. The angles formed by the polarization direction 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 ° and 90, respectively. The inspection system of claim 3, wherein ° and 135 °.
5. The inspection system according to claim 1, wherein the plurality of lighting units are arranged so that the elevation angles with respect to the object are different from each other.
6. The plurality of lighting units are
   A first illumination unit that irradiates illumination light along the optical axis of the polarizing camera, and
   Includes a ring-shaped second illumination unit centered on the optical axis of the polarizing camera.
   The plurality of splitters include a first modulator and a second substituent.
   The polarization direction of the illumination light emitted from the first illumination unit and the second illumination unit coincides with the polarization direction of the light transmitted through the first polarizing element and the second polarizing element, respectively. Item 5. The inspection system according to Item 5.
7. The plurality of illumination units include a plurality of concentric ring-shaped illumination units centered on the optical axis of the polarizing camera.
   The inspection device is
   Based on the plurality of polarized images, a phase image showing an angle formed by the normal direction of the surface of the object and the optical axis direction of the polarized camera is generated.
   The inspection system according to claim 5, wherein the object is inspected based on the phase image.
8. The inspection system according to claim 7, wherein the plurality of lighting units further include a lighting unit that irradiates illumination light along the optical axis of the polarizing camera.
9. The plurality of lighting units are
   A first illumination unit that irradiates illumination light along the optical axis of the polarizing camera, and
   A second illumination unit that irradiates illumination light from the back surface side of the object, and the like.
   The plurality of splitters include a first modulator and a second substituent.
   The polarization direction of the illumination light emitted from the first illumination unit and the second illumination unit coincides with the polarization direction of the light transmitted through the first polarizing element and the second polarizing element, respectively. Item 1. The inspection system according to Item 1.
10. 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 illumination.
    The plurality of substituents are
    A first polarizing element that transmits light in the same polarization direction as the polarization direction of the illumination light of the first illumination unit,
    A second polarizing element that transmits light in a polarization direction having an angle of 45 ° with the polarization direction of the light transmitted through the first polarizing element.
    A third polarizing element that transmits light in a polarization direction having an angle of 90 ° with respect to the polarization direction of the light transmitted through the first polarizing element is included.
    The plurality of polarized images include the first to third polarized images corresponding to the first to third modulators, respectively.
    The inspection device is
    The first to third polarized images are synthesized in a high dynamic range to generate a composite image.
    The inspection system according to claim 1, wherein the object is inspected based on the composite image.
11. It is an inspection method using a plurality of lighting units for illuminating an object and a polarizing camera in which unit regions including a plurality of polarizing elements are repeatedly arranged.
    The plurality of lighting units irradiate illumination light having different polarization states from each other.
    The plurality of polarizing elements transmit light in different polarization directions from each other.
    The inspection method is
    A step of acquiring a plurality of polarized images corresponding to the plurality of polarizing elements by photographing the object with the polarized camera in a state where the plurality of lighting units are lit at the same time.
    An inspection method comprising the step of inspecting the object using the plurality of polarized images.

Images