Image acquisition device, inspection device, and image acquisition method

Abstract

An image acquisition device (1) is provided with: an illumination device (2) that emits polarized light to an object (S); an imaging device (7) that detects the polarized light that has been regularly reflected by the object (S), and acquires a plurality of pieces of image data of mutually different polarized light components of the light; and an image processing device (8) that detects, on the basis of the plurality of pieces of image data, a foreign matter through which the polarized light present on the object (S) passes.

Description

Technical Field

[0001] One aspect of the embodiment relates to an image acquisition device, an inspection device, and an image acquisition method. Background Art

[0002] Conventionally, a device for inspecting an object by irradiating the object with light and detecting the light transmitted through the object has been known. For example, the device described in Patent Document 1 below calculates the distribution of the birefringence phase difference of the object based on the intensity signal detected by an image sensor, and determines the quality of the object based on this distribution. With a device having such a configuration, an object having birefringence can be inspected.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2020-190514 Summary of the Invention

[0006] Technical Problem to be Solved by the Invention

[0007] In the conventional device as described above, since the light transmitted through the object is detected, there is a tendency that it is difficult to detect an object having the property of reflected light. Therefore, it is required to detect with high precision an object having the property of reflected light on the object to be inspected.

[0008] Therefore, one aspect of the embodiment has been completed in view of this problem, and the technical problem thereof is to provide an image acquisition device, an inspection device, and an image acquisition method capable of detecting with high precision an object having the property of reflected light on an object.

[0009] Technical Means for Solving the Problem

[0010] The image acquisition device according to the first aspect of the embodiment includes: a light irradiation device that irradiates polarized light onto an object; an imaging device that detects the light that is specularly reflected by the object from the polarized light, and acquires image data including mutually different polarization components of the light; and an image processing unit that detects an object through which the polarized light passes and exists on the object based on a plurality of images.

[0011] Alternatively, the image acquisition method according to the second aspect of the embodiment includes: a light irradiation step of irradiating polarized light onto an object; an imaging step of detecting the light that is specularly reflected by the object from the polarized light, and acquiring image data including mutually different polarization components of the light; and an image processing step of detecting an object through which the polarized light passes and exists on the object based on a plurality of images.

[0012] According to the first aspect or the second aspect described above, it is possible to evaluate the distribution of the polarization state of the light that is specularly reflected from the light polarized by the object based on the detected image data. As a result, it is possible to detect with high accuracy an object on the object that has the property of transmitting and reflecting polarized light.

[0013] Alternatively, the inspection apparatus according to the third aspect of the embodiment includes: the image acquisition apparatus according to the first aspect; a conveyance apparatus that conveys the object in a predetermined direction; and an inspection processing unit that inspects the object based on data output from the image acquisition apparatus.

[0014] According to the third aspect described above, it is possible to efficiently detect an object having the property of transmitting and reflecting polarized light on a plurality of objects while conveying the plurality of objects.

[0015] Effects of the Invention

[0016] According to any aspect of the present invention, it is possible to detect with high accuracy an object having the property of reflecting light on the object. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic configuration diagram of the image acquisition apparatus 1 of the embodiment.

[0018] Figure 2 is a diagram showing Figure 1 the image of the reflected light generated in the object S when the image acquisition apparatus 1 is used.

[0019] Figure 3 is a diagram showing a plurality of image data obtained by the image processing apparatus 8 for the same object S.

[0020] Figure 4 is a diagram showing Figure 3 the graph of the luminance change in one pixel with respect to the rotation angle of the rotating wavelength plate 4 in the image data shown.

[0021] Figure 5 is a schematic configuration diagram of the inspection system 100 of the embodiment.

[0022] Figure 6 is a flowchart showing the sequence of the inspection method of the object S using the inspection system 100.

[0023] Figure 7 is a diagram showing the original image of the reflected light acquired by the camera 6 of the inspection system 100.

[0024] Figure 8 is a diagram showing the specular reflection light distribution, that is, the inspection result image, acquired by the computer 12 of the inspection system 100.

[0025] Figure 9 This is a diagram showing the linearly polarized light distribution, i.e., the inspection result image, obtained by the computer 12 of the inspection system 100.

[0026] Figure 10 It shows Figures 7 - 9 a graph showing the luminance distribution at the position of the line P2 on the three images shown.

[0027] Figure 11 This is a schematic structural diagram of the image acquisition device 1A of the first modified example.

[0028] Figure 12 This is a diagram showing the original image of the reflected light obtained by the inspection system 100.

[0029] Figure 13 This is a diagram showing the circularly polarized light distribution, i.e., the inspection result image, obtained by the inspection system 100.

[0030] Figure 14 It shows Figures 12 - 13 a graph showing the luminance distribution at the position of the line P3 on the two images shown.

[0031] Figure 15 This is a schematic structural diagram of the image acquisition device 1B of the second modified example.

[0032] Figure 16 This is a diagram showing the original image of the reflected light obtained by the inspection system 100.

[0033] Figure 17 This is a diagram showing the inspection result image obtained by the inspection system 100.

[0034] Figure 18 It shows Figures 16 - 17 a graph showing the luminance distribution at the position of the line P4 on the two images shown.

[0035] Figure 19 This is a diagram showing the structure of the imaging device 201 of the modified example. Detailed Embodiments

[0036] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used for the same elements or elements having the same functions, and repeated descriptions are omitted.

[0037] Figure 1 This is a schematic structural diagram of the image acquisition device 1 of the embodiment. The image acquisition device 1 is a device that acquires image data of an object for the purpose of inspecting for foreign substances on an object such as food. However, the object to be inspected by the image acquisition device 1 may be other items such as electronic components in addition to foods represented by beef, pork, chicken, mutton, processed foods, etc. InFigure 1 In this figure, the propagation path of light is indicated by a dashed line, and the transmission path of data such as image data is indicated by a solid line.

[0038] The image acquisition device 1 includes an illumination device (light irradiation device) 2, a right-angle prism mirror 3, an imaging device 7 including a rotating wavelength plate 4, a polarizing plate 5, and a camera 6, and an image processing device (image processing unit) 8. Hereinafter, the details of each component of the image acquisition device 1 will be described.

[0039] The illumination device 2 is composed of a main body portion 2a that diffuses and irradiates unpolarized light and a polarizing plate 2b that is mounted close to the light irradiation surface of the main body portion 2a, and irradiates light in a specified polarization state (light polarized into a specified polarization state) onto the object S. As the light emitting device built in the main body portion 2a, an LED, an SLD (Super luminescent diode), a laser, a halogen lamp, etc. can be cited. The shape of the light irradiation surface of the main body portion 2a can be planar or a curved surface such as a spherical surface. In the present embodiment, the illumination device 2 irradiates circularly polarized light (light whose polarization is circularly polarized).

[0040] The right-angle prism mirror 3 is provided adjacent to the light irradiation surface side of the illumination device 2. The right-angle prism mirror 3 is an optical element having a function of reflecting the light generated by reflecting the polarized light from the illumination device 2 by the object S to the camera 6. In addition, a mirror arranged at an angle of 45 degrees can also be used instead of the right-angle prism mirror 3.

[0041] The camera 6 included in the imaging device 7 is an imaging element that is arranged to be able to detect the position of the light from the object S reflected by the right-angle prism mirror 3 via the rotating wavelength plate 4 and the polarizing plate 5, and detect a two-dimensional image of the light reflected by the object S to acquire image data. As the camera 6, a CMOS (Complementary Metal Oxide Semiconductor) camera, a CCD (Charge Coupled Device) camera, etc. are used. In the case where the object S is conveyed in a specified direction by a conveying device, as the camera 6, a line sensor camera or a TDI (Time Delay Integration) sensor camera can also be used. In addition, the rotating wavelength plate 4, the polarizing plate 5, and the camera 6 can also be constituted by a polarizing camera having a polarizing plate that is different for each pixel and capable of acquiring an image including a plurality of polarization components.

[0042] The rotatable retardation plate 4 included in the imaging device 7 is an optical element disposed between the right-angle prism mirror 3 and the camera 6 that retards the phase of the polarization component in one direction of the light reflected by the right-angle prism mirror 3. The rotatable retardation plate 4 is disposed, for example, at an angle that retards the phase of the polarization component in one direction of the light by 90 degrees, but the retarded phase value is not limited to this. The rotatable retardation plate 4 is supported so as to be rotatable about an axis along the incident direction of the light from the right-angle prism mirror 3 to change the polarization direction of the retarded phase.

[0043] The polarizing plate 5 included in the imaging device 7 is disposed between the rotatable retardation plate 4 and the camera 6. The polarizing plate 5 is an optical element that allows the component of linearly polarized light in a certain fixed direction of the light reflected by the right-angle prism mirror 3 and transmitted through the rotatable retardation plate 4 to pass through.

[0044] The image processing device 8 is a device that detects foreign matter on the object S by receiving the image data acquired by the camera 6. Physically, the image processing device 8 is an arithmetic device (such as a computer) incorporating a CPU (Central Processing Unit) or GPU (Graphics Processing Unit) as a processor, a RAM (Random Access Memory) or ROM (Read Only Memory) as a recording medium, a communication module, and an input / output module. In addition, the image processing device 8 may be composed of an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). The image processing device 8 can acquire the image data from the camera 6 via a cable or by wireless communication. The detection function of the image processing device 8 will be described later.

[0045] Here, with reference to Figure 2 , the detection mechanism of the reflected light from the object S in the image acquisition device 1 will be described. Figure 2 is a diagram showing an image of the reflected light generated in the object S when the image acquisition device 1 is used.

[0046] Each polarized light ray L0 diffused and irradiated by the lighting device 2 reaches the surface of the object S widely. The object S such as food has the property of generating specularly reflected light L1 and diffusely reflected light L2 when light is incident. In particular, when the polarized light ray L0 is incident on the object S, the degree of polarization of the specularly reflected light L1 generated on this basis becomes higher, and the degree of polarization of the diffusely reflected light L2 generated on this basis becomes lower. In addition, when a foreign object FS such as a plastic film, which is an object having the property of transmitting polarized light, exists on the surface of the object S, the polarized light ray L0 incident on the foreign object FS generates specularly reflected light L3 specularly reflected on the surface of the foreign object FS, specularly reflected light L4 specularly reflected on the back surface of the foreign object FS after passing through the foreign object FS, and diffusely reflected light L5 diffusely reflected by the foreign object FS. In this case, the intensities of the specularly reflected lights L3 and L4 are higher than that of the specularly reflected light L1, and their degrees of polarization are higher than those of the diffusely reflected lights L2 and L5, just like the specularly reflected light L1. In addition, when the material of the foreign object FS has birefringence, the polarization state of the specularly reflected light L4 changes from the polarization state of the incident light ray L0.

[0047] In order to two-dimensionally detect the reflectance or polarization state of the reflected light from the object S by using the properties of the above-mentioned reflected light, the image processing device 8 of the image acquisition device 1 acquires and stores image data including a plurality of different polarization components, or a plurality of pieces of image data corresponding to a plurality of different polarization components, with the same object S as the object from the camera 6. Specifically, while rotating the rotating wave plate 4 at a prescribed angular interval with the same object S as the object, 4 or more pieces of image data for calculating Stokes parameters for each pixel by using the rotation compensation method are acquired. In this way, the image processing device 8 acquires image data representing mutually different polarization components by detecting the light including the specularly reflected light specularly reflected by the object S while rotating the rotating wave plate 4.

[0048] Figure 3 An example showing a plurality of pieces of image data acquired by the image processing device 8 with the same object S as the object Figure 4 Showing the luminance change in one pixel with respect to the rotation angle of the rotating wave plate 4. In the example shown here, while rotating the rotating wave plate 4 in the range from 0 degrees to 170 degrees at 10-degree intervals, 18 pieces of image data are acquired. Figure 4 The shown graph represents Figure 3 The luminance change in the pixel at the position P1 on the shown image data. As shown in this graph, by rotating the rotating wave plate 4, the luminance of the polarization component detected by the pixel changes periodically.

[0049] Next, the structure of the inspection system 100 of the inspection device as an embodiment will be described. Figure 5This is the schematic structure of the inspection system 100 of the embodiment.

[0050] The inspection system 100 includes the image acquisition device 1 having the above structure, a conveying device 11 such as a belt conveyor that conveys the object S in a specified direction, and a computer (inspection processing unit) 12 that performs operations on the image data output from the image acquisition device 1. The image acquisition device 1 acquires image data with the object S conveyed by the conveying device 11 as the object, and outputs the acquired image data to the computer 12.

[0051] The computer 12 has the same hardware structure as the image processing device 8. That is, the computer 12 is an arithmetic device that physically incorporates a CPU or GPU as a processor, a RAM or ROM as a recording medium, a communication module, and an input / output module, etc. The computer 12 can acquire image data from the image processing device 8 via a cable, or can acquire image data from the image processing device 8 through wireless communication.

[0052] Functionally, the computer 12 performs inspection processing on the object S based on multiple image data using, for example, the rotation compensator method. That is, the computer 12 first takes multiple image data obtained with the same object S as the object, and obtains the brightness of one pixel.

[0053] Here, the brightness I of the pixel of each image data is theoretically represented by the following formula (1).

[0054] I = I 0 (2 + S 1 - 2S 3 sin2C + S 1 cos4C + S 2 sin4C) (1)

[0055] In the above formula (1), I 0 represents the average brightness of all the reflected light incident on the imaging device 7, S 1 , S 2 , S 3 represent Stokes parameters, and C represents the rotation angle of the rotation wavelength plate 4. The Stokes parameter S 1 is a parameter representing the intensity difference between orthogonal polarization components, the Stokes parameter S 2 is a parameter representing the intensity difference between the +π / 4 polarization component and the -π / 4 polarization component, and the Stokes parameter S 3 is a parameter representing the intensity difference between the right-handed circular polarization component and the left-handed circular polarization component. In addition, the degree of polarization p in this pixel is given by the following formula (2)

[0056] p = S 1 2 + S 22 +S 3 2 (2)

[0057] representation

[0058] The computer 12 processes the luminance in one pixel of a plurality of image data by using the relationship of the above formula (1), and calculates the Stokes parameter S in this pixel through an operation 1 , S 2 , S 3 and luminance I 0 . For example, the computer 12 calculates the Stokes parameters S 1 , S 2 , S 3 as Fourier series. In addition, the computer 12 repeats the same operation for all pixels of the image data to obtain the Stokes parameters S 1 , S 2 , S 3 and luminance I 0 .

[0059] In addition, the computer 12 can also perform any of the following operations based on the Stokes parameters S 1 , S 2 , S 3 and luminance I 0 for each pixel obtained with an object S as the object, thereby obtaining an inspection result image representing the distribution related to the polarization in the reflected light from the object S.

[0060] (Normal reflected light distribution) p × I 0

[0061] (Linear polarization distribution) S 1 × I 0

[0062] (Linear polarization distribution) S 2 × I 0

[0063] (Circular polarization distribution) S 3 × I 0

[0064] Then, the computer 12 outputs one or more inspection result images obtained with an object S as the object to an output device such as a display. In addition, the computer 12 can also output the inspection result image to an external device via a network, a recording medium, etc.

[0065] Next, a method for inspecting the object S using the inspection system 100 will be described, and the image acquisition method of the present embodiment will be described in detail. Figure 6It is a flowchart showing the order of the inspection method for the object S.

[0066] First, when the inspection process of the object S starts, the conveyance of the object S by the conveyance device 11 is started (step S1). After that, when the object S is conveyed by the conveyance device 11 into the range of the polarized light irradiation of the illumination device 2, polarized light is irradiated from the illumination device 2 to the object S (step S2).

[0067] Correspondingly, the reflected light generated on the surface of the object S is incident on the camera 6 via the rotating wavelength plate 4 and the polarizing plate 5, and the two-dimensional image of the reflected light is detected by the camera 6, thereby outputting image data (S3). At this time, by rotating the rotating wavelength plate 4 while repeatedly detecting the two-dimensional image of the reflected light, a plurality of image data reflecting the detection results of a plurality of polarization components of the reflected light are output.

[0068] The image data acquired by the camera 6 is acquired and stored by the image processing device 8 and then output to the computer 12, where it is processed. That is, the computer 12 calculates the Stokes parameters, etc. for each pixel based on the brightness of each pixel of the image data (step S4). Next, the computer 12 obtains one or more inspection result images representing the distribution related to the polarization in the reflected light from the object S by calculating the Stokes parameters, etc. for each pixel (step S5). The inspection result image is at least one of a specular reflection light distribution, a linearly polarized light distribution, and a circularly polarized light distribution. Finally, the computer 12 outputs one or more inspection result images of the object S as images for detecting foreign substances FS present on the object S to the output device (step S6), and ends the inspection process of the object S.

[0069] In Figures 7 - 9 shows an example of an image obtained by the inspection process of the inspection system 100. Figure 7 is the original image of the reflected light acquired by the camera 6 in the state where the rotating wavelength plate 4 and the polarizing plate 5 are removed. Figure 8 is the inspection result image of the specular reflection light distribution acquired by the computer 12. Figure 9 is the inspection result image of the linearly polarized light distribution acquired by the computer 12. In addition, since the illumination light is circularly polarized light, the linearly polarized light distribution means an image representing the degree of change in the polarization state. In addition, Figure 10 is shown Figures 7 - 9 is a graph showing the brightness distribution at the position of the line P2 on the three images shown. When calculating the evaluation value C obtained by dividing the average brightness at the position where the foreign substance FS exists in this brightness distribution by the average brightness at the position where the foreign substance FS does not exist, in Figure 7 the case of C = 1.5, in Figure 8 the case of C = 3.3, in Figure 9In the case of C = 7.4. From this result, it can be seen that in the inspection result image obtained by the inspection system 100, the image of the foreign object FS is embossed, and the foreign object FS can be effectively detected by the inspection system 100.

[0070] According to the present embodiment, it is possible to evaluate the distribution of the polarization state of the light that is specularly reflected from the light polarized by the object S based on the image data detected by the image acquisition device 1. As a result, it is possible to highly accurately detect the foreign object FS having the property of transmitting and reflecting polarized light on the object S.

[0071] In the image acquisition device 1, the illumination device 2 is configured to irradiate the object S with diffused polarized light. Thus, in the case of a three-dimensional object S such as food, it is possible to detect the foreign object FS having the property of transmitting and reflecting polarized light in a wide range.

[0072] In addition, in the image acquisition device 1, the illumination device 2 is configured to irradiate light with circular polarization. In this case, even when the foreign object FS has birefringence, it is possible to highly accurately detect the foreign object FS.

[0073] In addition, in the image acquisition device 1, the imaging device 7 includes a polarizing plate 5 and is configured to detect the reflected light via the polarizing plate 5. In this way, it is possible to evaluate the distribution of the polarization state of the light that is specularly reflected from the light polarized by the object S with a simple structure.

[0074] In addition, in the image acquisition device 1, the imaging device 7 further includes a rotating wave plate 4 and is configured to detect the reflected light via the rotating wave plate 4. In this case, it is possible to highly accurately evaluate the distribution of the polarization state of the light that is specularly reflected from the light polarized by the object S by using operations such as Stokes parameters.

[0075] Alternatively, according to the inspection system 100 of the present embodiment, it is possible to efficiently detect the objects having the property of transmitting and reflecting polarized light on a plurality of objects S while conveying the plurality of objects S.

[0076] As described above, various embodiments of the present invention have been described, but the present invention is not limited to the above embodiments, and can be modified within the scope of the gist described in the claims, or applied to other embodiments.

[0077] Figure 11 It is a schematic structural diagram of the image acquisition device 1A which is a modification example. The image acquisition device 1A has a structure in which the illumination device 2 in the image acquisition device 1 is replaced with an illumination device 2A. The illumination device 2A is composed of a main body portion 2a and a polarizing plate 2c mounted close to the light irradiation surface of the main body portion 2a, and irradiates the object S with diffused linearly polarized light in a specified polarization state.

[0078] Figures 12 - 13 An example of an image obtained through the inspection process of the inspection system 100 including the image acquisition device 1A is shown. Figure 12 It is the original image of the reflected light obtained by the camera 6 in a state where the rotating wavelength plate 4 and the polarizing plate 5 are removed. Figure 13 It is the circular polarization distribution obtained by the computer 12, that is, the inspection result image. In addition, since the illumination light is linearly polarized light, the circular polarization distribution refers to an image indicating the degree of change in the polarization state. In addition, Figure 14 It represents Figures 12 - 13 a graph showing the luminance distribution at the position of the line P3 on the two images shown. When calculating the evaluation value C corresponding to the two foreign substances FS in this luminance distribution, in the case of Figure 12 , C = 1.1, 1, 3, and in the case of Figure 13 , C = 5.9, 7.1. From this result, it can be seen that in the inspection result image obtained by the inspection system 100, the image of the foreign substance FS is embossed, and the foreign substance FS can be effectively detected by the inspection system 100.

[0079] Figure 15 It is a schematic structural diagram of the image acquisition device 1B of the second modified example. The image acquisition device 1B has a structure in which the rotating wavelength plate 4 and the polarizing plate 5 in the image acquisition device 1 are replaced with a rotating polarizing plate 5B. The rotating polarizing plate 5B is supported so as to be able to rotate about an axis along the incident direction of the light from the right-angle prism mirror 3, so as to change the polarization direction of the transmitted linearly polarized light. The image processing device 8 of the image acquisition device 1B repeatedly captures a two-dimensional image of the object S by the camera 6 while changing the rotation angle of the rotating polarizing plate 5B with respect to one object S, and acquires and stores a plurality of image data output as a result. The computer 12 acquires the plurality of image data obtained by the image processing device 8 as the inspection result image.

[0080] Figures 16 - 17 An example of an image obtained through the inspection process of the inspection system 100 including the image acquisition device 1B is shown. Figure 16 It is the original image of the reflected light obtained by the camera 6 in a state where the rotating polarizing plate 5B is removed. Figure 17 It is an arithmetic image based on the inspection result image obtained by the computer 12. For example, for the first inspection result image and the second inspection result image obtained with the rotating polarizing plate 5B at different rotation angles, their respective averages are subtracted, and the absolute value of the difference between the first inspection result image and the second inspection result image after subtracting the average is obtained, thereby enabling the acquisition of the arithmetic image. In addition, Figure 18 It represents Figures 16 - 17A graph of the luminance distribution at the position of line P4 on the two images shown. When calculating the evaluation value C corresponding to the two foreign substances FS in this luminance distribution, in Figure 16 the case of, C = 1.2, 1.3, and in Figure 17 the case of, C = 9.2, 11.4. From this result, it can be seen that in the inspection result image obtained by the inspection system 100, the image of the foreign substance FS is embossed, and the foreign substance FS can be effectively detected by the inspection system 100.

[0081] In addition, in the image acquisition device 1B of the second modification example, instead of the imaging device 7, a Figure 19 imaging device 201 having the structure shown can also be used. The imaging device 201 is configured to divide the reflected light of the object S incident from the right-angle prism mirror 3 into a plurality of polarized light components, and form a two-dimensional image of the two divided polarized light components on the light-receiving surface of the internal imaging element. Hereinafter, the structure of the imaging device 201 will be described.

[0082] As Figure 19 shown, the imaging device 201 is configured to incorporate a collimating lens 203, an imaging lens 204, a pre-stage polarization beam splitter 205a, a post-stage polarization beam splitter 205b, a pre-stage mirror 206a, a post-stage mirror 206b, and an imaging lens moving mechanism 208 inside a housing 202.

[0083] A circular field stop 209 is provided at the center of one end side end surface of a cylindrical portion 202a that forms a part of the housing 202. The field stop 209 has an aperture adjustment mechanism 214 that can variably set its inner diameter (width). Then, the collimating lens 203 is fixed inside the other end side of the cylindrical portion 202a in such a manner that its optical axis A 1 coincides with the central axis of the cylindrical portion 202a, that is, the central axis of the field stop 209. With such a structure, the field stop 209 can variably set the width in the direction perpendicular to the optical axis A 1 . Then, the end surface of the cylindrical portion 202a of the housing 202 faces the right-angle prism mirror 3 and is fixed, and the reflected light from the right-angle prism mirror 3 is input into the housing 202 along the optical axis A 1 . Then, the collimating lens 203 receives the reflected light that has passed through the field stop 209, converts the reflected light into parallel light, and outputs it along the optical axis A 1 to the inside of the housing 202. By adjusting the opening of the field stop 209, the field of view range on the imaging surface of the reflected light from the object can be restricted.

[0084] On the opposite side of the cylindrical portion 202a of the housing 202, a cylindrical portion 202b coaxial with the cylindrical portion 202a is integrally formed. At the center of the end face of the cylindrical portion 202b, a circular window portion 210 is provided for allowing the optical image formed based on the reflected light input from the cylindrical portion 202a side to pass to the outside. Then, a camera 6 is mounted on the end face of the cylindrical portion 202b of the housing 202. The camera 6 incorporates an imaging element 6a, and the light receiving surface 6b of the imaging element 6a faces the window portion 210, and the center of the light receiving surface 6b is located on the optical axis A of the collimating lens 203 1 and is mounted in such a manner that the light receiving surface 6b coincides with the imaging position of the optical image output from the window portion 210. With such a mounting structure, in a state where the imaging device 201 is arranged coaxially with respect to the right-angle prism mirror 3, the optical image imaged by the imaging device 201 can be photographed by the camera 6.

[0085] Furthermore, on the optical axis A inside the housing 202 between the cylindrical portions 202a and 202b 1 a pre-stage polarization beam splitter 205a and a post-stage polarization beam splitter 205b, which are optical separation elements, are detachably arranged. These polarization beam splitters 205a and 205b are configured to be integrated and can be detached from the optical axis A inside the housing 202 1 . In addition, the polarization beam splitters 205a and 205b may also be integrated with the following pre-stage mirror 206a and post-stage mirror 206b and be detachable.

[0086] The pre-stage polarization beam splitter 205a is arranged at a position adjacent to the collimating lens 203, its center is located on the optical axis A 1 and its light receiving surface is inclined 45 degrees with respect to the orthogonal plane of the optical axis A 1 . The pre-stage polarization beam splitter 205a splits and transmits the linearly polarized light at a specified angle θ1 (hereinafter referred to as "first split light") in the parallel light output from the collimating lens 203 and outputs the first split light along the optical axis A 1 . At the same time, the pre-stage polarization beam splitter 205a splits and reflects the linearly polarized light at a specified angle θ2 different from the specified angle θ1 (hereinafter referred to as "second split light") in the parallel light and outputs the second split light in a direction perpendicular to the optical axis A 1 (the downward direction in Figure 19 ).

[0087] The post-stage polarization beam splitter 205b is arranged at a position away from the pre-stage polarization beam splitter 205a toward the window portion 210 side, its center is offset by a specified distance from the optical axis A 1 toward the post-stage mirror 206b side, and its light receiving surface is relative to the optical axis A 1The orthogonal plane is inclined by 45 degrees. The post-stage polarization beam splitter 205b is composed of an optical component having the same transmission characteristics and reflection characteristics as those of the pre-stage polarization beam splitter 205a. By further transmitting the first split light that has passed through the pre-stage polarization beam splitter 205a, the first split light is directed along the optical axis A 1 towards the window portion 210 for output. At the same time, the post-stage polarization beam splitter 205b reflects the second split light that has been reflected by the pre-stage polarization beam splitter 205a and passed through the pre-stage mirror 206a and the post-stage mirror 206b, and outputs the second split light towards the window portion 210 along a direction inclined with respect to the optical axis A 1 .

[0088] That is, these polarization beam splitters 205a and 205b are optical separation elements that separate the parallel light from the collimating lens 203 into two polarization components of the first and second split lights.

[0089] The pre-stage mirror 206a is separately provided with respect to the pre-stage polarization beam splitter 205a in the reflection direction of the second split light, and the angle of the light-receiving surface of the pre-stage mirror 206a is set to be inclined by 45 degrees with respect to the orthogonal plane of the optical axis A 1 . The pre-stage mirror 206a reflects the second split light output from the pre-stage polarization beam splitter 205a in a direction parallel to the optical axis A 1 . The post-stage mirror 206b is provided to be separated from the pre-stage mirror 206a in the reflection direction of the second split light and faces the light-receiving surface of the post-stage polarization beam splitter 205b. The angle of the light-receiving surface of the post-stage mirror 206b is set to be inclined by 45 + α degrees (α is a preset angle) with respect to the orthogonal plane of the optical axis A 1 . The post-stage mirror 206b reflects the second split light that has passed through the pre-stage mirror 206a in a direction crossing the optical axis A 1 towards the light-receiving surface of the post-stage polarization beam splitter 205b.

[0090] Furthermore, on the optical axis A 1 between the post-stage polarization beam splitter 205b and the window portion 210, an imaging lens 204 is provided which is supported by the imaging lens moving mechanism 208 so as to be position-adjustable. The imaging lens 204 is supported in such a manner that its optical axis A 2 is parallel to the optical axis A 1 , and is configured to be able to move in a direction perpendicular to the optical axis A 2 while maintaining the state where the optical axis A 1 is parallel to the optical axis A 1 by the imaging lens moving mechanism 208. Specifically, the imaging lens 204 can be set by the imaging lens moving mechanism 208 to a first state where the optical axis A 2 is coincident with the optical axis A 1 and a state where the optical axis A 2 is separated from the optical axis A 1The second state deviated from the specified distance. At this time, the center of the subsequent polarization beam splitter 205b is located on the optical axis of the imaging lens 204. Thereby, vignetting can be reduced. As such an imaging lens moving mechanism 208, it may be a sliding mechanism capable of continuously adjusting the position of the imaging lens 204, or a switching mechanism that switches to positions corresponding to the first and second states in two stages. When the imaging lens 204 is set to the second state by the imaging lens moving mechanism 208, it receives the first and second split lights split from the reflected light via the polarization beam splitters 205a and 205b, and forms images of these split lights as the first and second light images separated on the light receiving surface 6b in the camera 6 installed outside the window portion 210. On the other hand, when the imaging lens 204 is set to the first state by the imaging lens moving mechanism 208 and the polarization beam splitters 205a and 205b are removed, it receives only the reflected light via the collimating lens 203, and forms an image of this reflected light as a single light image on the light receiving surface 6b in the camera 6 installed outside the window portion 210.

[0091] The imaging device 201 with such a structure can be used for both an observation mode (hereinafter referred to as "single view mode") of observing the reflected light as a single light image by the camera 6 and an observation mode (hereinafter referred to as "dual view mode") of separating the reflected light into two light images by the camera 6 for observation. According to the image acquisition device 1B employing the imaging device 201, images of multiple polarization components of the reflected light can be obtained simultaneously, and the distribution of the polarization state of the light polarized by the object S after being specularly reflected can be immediately evaluated.

[0092] In the above embodiment, it is preferable that the light irradiation device irradiates the polarized light toward the object in a diffused manner. Thereby, in the case of a three-dimensional object as the object, an object having the property of transmitting and reflecting polarized light in a wide range can be detected.

[0093] In addition, in the above embodiment, it is preferable that the light irradiation device irradiates circularly polarized light. In this case, even when the object has birefringence, the object can be detected with high accuracy.

[0094] Furthermore, in the above embodiment, it is preferable that the light irradiation device irradiates linearly polarized light. In this way, the distribution of changes in the polarization state can be easily evaluated based on the detected image, and an object that transmits and reflects polarized light can be easily detected.

[0095] In addition, in the above embodiment, it is preferable that the imaging device includes a polarizing plate and detects the light specularly reflected via the polarizing plate. In this way, the distribution of the polarization state of the light polarized by the object after being specularly reflected can be evaluated with a simple structure.

[0096] In addition, in the above-described embodiment, it is preferable that the imaging device further includes a wavelength plate and detects the light that is specularly reflected via the wavelength plate. In this case, it is possible to highly accurately evaluate, through calculation, the distribution of the polarization state of the light that is specularly reflected after the light polarized by the object.

[0097] Furthermore, in the above-described embodiment, it is preferable that the imaging device includes a light separation element that separates the specularly reflected light into a plurality of light components, and images the plurality of light components to obtain image data including a plurality of images. In this case, it is possible to simultaneously obtain a plurality of images and immediately evaluate the distribution of the polarization state of the light that is specularly reflected after the light polarized by the object.

[0098] The image acquisition device according to the embodiment is [1] "An image acquisition device, comprising: a light irradiation device that irradiates polarized light onto an object; an imaging device that detects the light that is specularly reflected by the object after the polarized light is reflected, and obtains image data including mutually different polarization components of the light; and an image processing unit that detects, based on a plurality of images, an object through which the polarized light existing on the object passes".

[0099] The image acquisition device according to the embodiment may also be [2] "The image acquisition device according to the above [1], wherein the light irradiation device irradiates the polarized light so as to be diffused toward the object".

[0100] The image acquisition device according to the embodiment may also be [3] "The image acquisition device according to the above [1] or [2], wherein the light irradiation device irradiates circularly polarized light".

[0101] The image acquisition device according to the embodiment may also be [4] "The image acquisition device according to the above [1] or [2], wherein the light irradiation device irradiates linearly polarized light".

[0102] The image acquisition device according to the embodiment may also be [5] "The image acquisition device according to any one of the above [1] to [4], wherein the imaging device includes a polarizing plate and detects the light that is specularly reflected via the polarizing plate".

[0103] The image acquisition device according to the embodiment may also be [6] "The image acquisition device according to the above [5], wherein the imaging device further includes a wavelength plate and detects the light that is specularly reflected via the wavelength plate".

[0104] The image acquisition device according to the embodiment may also be [7] "The image acquisition device according to any one of the above [1] to [4], wherein the imaging device includes a light separation element that separates the specularly reflected light into a plurality of light components, and images the plurality of light components to obtain image data including a plurality of images".

[0105] The inspection device of the embodiment is [8] "an inspection device including: the image acquisition device according to any one of [1] to [7] above; a conveying device that conveys an object in a specified direction; and an inspection processing unit that inspects the object based on data output from the image acquisition device".

[0106] The image acquisition method of the embodiment is [9] "an image acquisition method including: a light irradiation step of irradiating polarized light onto an object; a photographing step of detecting light that is specularly reflected by the object from the polarized light and acquiring image data including mutually different polarization components of the light; and an image processing step of detecting an object through which the polarized light existing on the object passes based on a plurality of images".

[0107] Explanation of symbols

[0108] 1, 1A, 1B... Image acquisition device, 2... Lighting device (light irradiation device), 4... Rotating wavelength plate, 5... Polarizing plate, 5B... Rotating polarizing plate, 7, 201... Photographing device, 205a, 205b... Polarizing beam splitter (light separation element), 8... Image processing device (image processing unit), 11... Conveying device, 12... Computer (inspection processing unit), 100... Inspection system (inspection device), S... Object, FS... Foreign matter.

Claims

1. An image acquisition device, characterized in that, comprising: a light irradiation device that irradiates polarized light onto an object; an imaging device that detects the light after the polarized light is specularly reflected by the object and acquires image data including mutually different polarization components of the light; and an image processing unit that detects an object through which the polarized light existing on the object passes based on the image data.

2. The image acquisition device according to claim 1, characterized in that, the light irradiation device irradiates the polarized light toward the object while diffusing it.

3. The image acquisition device according to claim 1 or 2, characterized in that, the light irradiation device irradiates the polarized light as circularly polarized light.

4. The image acquisition device according to claim 1 or 2, characterized in that, the light irradiation device irradiates the polarized light as linearly polarized light.

5. The image acquisition device according to any one of claims 1 to 4, characterized in that, the imaging device includes a polarizing plate and detects the light specularly reflected through the polarizing plate.

6. The image acquisition device according to claim 5, characterized in that, the imaging device further includes a retardation plate and detects the light specularly reflected through the retardation plate.

7. The image acquisition device according to any one of claims 1 to 4, characterized in that, the imaging device includes a light separation element that separates the specularly reflected light into a plurality of light components, and images the plurality of light components to acquire the image data including a plurality of images.

8. An inspection device, characterized in that, comprising: the image acquisition device according to any one of claims 1 to 7; a conveying device that conveys the object in a predetermined direction; and an inspection processing unit that inspects the object based on data output from the image acquisition device.

9. An image acquisition method, characterized in that, comprising: a light irradiation step of irradiating polarized light onto an object; an imaging step of detecting the light after the polarized light is specularly reflected by the object and acquiring image data including mutually different polarization components of the light; and an image processing step of detecting an object through which the polarized light existing on the object passes based on the image data.

10. The image acquisition method according to claim 9, characterized in that, in the light irradiation step, the polarized light is irradiated toward the object while diffusing it.

11. The image acquisition method according to claim 9 or 10, characterized in that, in the light irradiation step, the polarized light is irradiated as circularly polarized light.

12. The image acquisition method according to claim 9 or 10, characterized in that, in the light irradiation step, the polarized light is irradiated as linearly polarized light.

13. The image acquisition method according to any one of claims 9 to 12, characterized in that, in the imaging step, the light specularly reflected through a polarizing plate is detected.

14. The image acquisition method according to claim 13, characterized in that, in the imaging step, the light specularly reflected through a retardation plate is detected.

15. The image acquisition method according to any one of claims 9 to 12, characterized in that, in the imaging step, the light after regular reflection is separated into a plurality of light components, and the plurality of light components are imaged to obtain the image data including a plurality of images.

Images