Image acquisition device, detection device, and image acquisition method

Abstract

An image acquisition device 1 comprises: an illumination device 2 for irradiating an object S with polarized light; an image capture device 7 for detecting light that is the polarized light directly reflected by the object S and acquiring a plurality of pieces of image data on mutually different polarization components of the light; and an image processing device 8 for detecting, on the basis of the plurality of pieces of image data, foreign matter that is present on the object S and through which the polarized light passes.

Description

Image acquisition device, inspection device, and image acquisition method

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

[0002] Conventionally, there have been known devices that inspect an object by irradiating the object with light and detecting the light transmitted through the object. For example, the device described in Patent Document 1 below calculates the distribution of birefringence phase difference of the object from an intensity signal detected by an image sensor, and judges the quality of the object based on the distribution. A device configured in this way can inspect an object having birefringence.

[0003] Japanese Patent Application Laid-Open No. 2020-190514

[0004] In the conventional devices described above, since light transmitted through the object to be inspected is detected, it tends to be difficult to detect objects that have the property of reflecting light. Therefore, there is a need to detect objects on the object to be inspected that have the property of reflecting light with high accuracy.

[0005] Therefore, one aspect of the embodiment has been made in consideration of such problems, and aims to provide an image acquisition device, an inspection device, and an image acquisition method that are capable of detecting objects on a target object that have the property of reflecting light with high accuracy.

[0006] An image acquisition device according to a first aspect of the embodiment includes a light irradiation device that irradiates an object with polarized light, an imaging device that detects the polarized light that is specularly reflected by the object and acquires image data containing different polarization components of the light, and an image processing unit that detects objects present on the object through which the polarized light passes, based on multiple images.

[0007] Alternatively, an image acquisition method according to a second aspect of the embodiment includes a light irradiation step of irradiating an object with polarized light, an imaging step of detecting the polarized light specularly reflected by the object and acquiring image data containing different polarization components of the light, and an image processing step of detecting objects present on the object through which the polarized light passes, based on multiple images.

[0008] According to the first or second aspect, it is possible to evaluate the distribution of polarization states of light that is polarized light specularly reflected by an object based on detected image data, and 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.

[0009] Alternatively, an inspection device according to a third aspect of the embodiment includes an image acquisition device according to the first aspect, a conveying device that conveys an object in a predetermined direction, and an inspection processing unit that inspects the object based on data output from the image acquisition device.

[0010] According to the third aspect, it is possible to efficiently detect objects that have the property of transmitting and reflecting polarized light on a plurality of objects while transporting the plurality of objects.

[0011] According to any one of the aspects of the present invention, an object on a target object that has the property of reflecting light can be detected with high accuracy.

[0012] 10 is a schematic diagram of an image acquisition device 1 according to an embodiment. FIG. 1 is a diagram showing an image of reflected light occurring at an object S when the image acquisition device 1 of FIG. 1 is used. FIG. 2 is a diagram showing a plurality of image data acquired of the same object S by an image processing device 8. FIG. 3 is a graph showing the change in luminance at one pixel with respect to the rotation angle of the rotary wavelength plate 4 in the image data shown in FIG. 3. FIG. 10 is a schematic diagram of an inspection system 100 according to an embodiment. FIG. 11 is a flowchart showing the procedure of an inspection method for an object S using the inspection system 100. FIG. 12 is a diagram showing an original image of reflected light acquired by a camera 6 of the inspection system 100. FIG. 13 is a diagram showing an inspection result image which is a specular reflection light distribution acquired by a computer 12 of the inspection system 100. FIG. 14 is a diagram showing an inspection result image which is a linear polarization distribution acquired by a computer 12 of the inspection system 100. FIG. 15 is a graph showing the luminance distribution at the position of a line P2 on the three images shown in FIGS. 7 to 9. FIG. 16 is a schematic diagram of an image acquisition device 1A according to a first modified example. FIG. 17 is a diagram showing an original image of reflected light acquired by the inspection system 100. FIG. 18 is a diagram showing an inspection result image which is a circular polarization light distribution acquired by the inspection system 100. 14 is a graph showing the luminance distribution at the position of line P3 on the two images shown in Figures 12 and 13. It is a schematic configuration diagram of an image acquisition device 1B according to a second modified example. It is a diagram showing an original image of reflected light acquired by an inspection system 100. It is a diagram showing an inspection result image acquired by an inspection system 100. It is a graph showing the luminance distribution at the position of line P4 on the two images shown in Figures 16 and 17. It is a diagram showing the configuration of an imaging device 201 according to a modified example.

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same elements or elements having the same functions will be denoted by the same reference numerals, and redundant description will be omitted.

[0014] FIG. 1 is a schematic diagram of an image acquisition device 1 according to an embodiment. The image acquisition device 1 is a device that acquires image data of an object, such as food, for the purpose of inspecting the object for the presence or absence of foreign matter thereon. However, the object inspected by the image acquisition device 1 may be other items such as electronic components in addition to food, such as beef, pork, chicken, lamb, and processed foods. In FIG. 1, the propagation path of light is indicated by a dotted line, and the transmission path of data, such as image data, is indicated by a solid line.

[0015] 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. Each component of the image acquisition device 1 will be described in detail below.

[0016] The lighting device 2 is composed of a main body 2a that irradiates diffused unpolarized light and a polarizing sheet 2b attached close to the light irradiation surface of the main body 2a, and irradiates diffused light of a predetermined polarization state (light polarized in a predetermined polarization state) toward the target S. Examples of light-emitting devices built into the main body 2a include an LED, an SLD (Superluminescent Diode), a laser, and a halogen lamp. The shape of the light irradiation surface of the main body 2a may be flat or may be curved, such as spherical. In this embodiment, the lighting device 2 irradiates circularly polarized light (light polarized to circular polarization).

[0017] The right-angle prism mirror 3 is provided adjacent to the light irradiation surface side of the lighting device 2. This right-angle prism mirror 3 is an optical element that has the function of reflecting light generated when polarized light from the lighting device 2 is reflected by the object S, toward the camera 6. Note that instead of the right-angle prism mirror 3, a mirror disposed at an angle of 45 degrees may be used.

[0018] The camera 6 provided in the imaging device 7 is an imaging element that is positioned at a position where it can detect 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 that detects a two-dimensional image of the light reflected by the object S to obtain image data. The camera 6 may be a CMOS (Complementary Metal Oxide Semiconductor) camera, a CCD (Charge Coupled Device) camera, or the like. When the object S is transported in a predetermined direction by a transport device, the camera 6 may be a line sensor camera or a TDI (Time Delay Integration) sensor camera. The rotating wavelength plate 4, the polarizing plate 5, and the camera 6 may also be configured by a polarization camera that has a different polarizer plate for each pixel and can obtain an image containing multiple polarization components.

[0019] The rotatable wave plate 4 provided in the imaging device 7 is an optical element that is disposed between the right-angle prism mirror 3 and the camera 6 and that delays the phase of the polarized component of light in one direction reflected by the right-angle prism mirror 3. The rotatable wave plate 4 is disposed at an angle that delays the phase of the polarized component of light in one direction by 90 degrees, for example, but the amount of phase delay is not limited to this. The rotatable wave plate 4 is supported so as to be rotatable about a rotation axis that is aligned with the direction of incidence of the light from the right-angle prism mirror 3, so as to change the polarization direction in which the phase is delayed.

[0020] The polarizing plate 5 provided in the imaging device 7 is disposed between the rotating wave plate 4 and the camera 6. This polarizing plate 5 is an optical element that transmits a component of the light that has been reflected by the right-angle prism mirror 3 and then passed through the rotating wave plate 4, which is linearly polarized in a fixed direction.

[0021] The image processing device 8 is a device that detects foreign objects on the target object S by receiving image data acquired by the camera 6. The image processing device 8 is physically an arithmetic device (such as a computer) that incorporates a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit), a recording medium such as a RAM (Random Access Memory) or a ROM (Read Only Memory), a communication module, and an input / output module. The image processing device 8 may also be configured with an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). The image processing device 8 may acquire image data from the camera 6 via a cable, or may acquire image data from the camera 6 via wireless communication. The detection function of the image processing device 8 will be described later.

[0022] Here, a mechanism for detecting reflected light from the object S in the image acquisition device 1 will be described with reference to Fig. 2. Fig. 2 is a diagram showing an image of reflected light occurring at the object S when the image acquisition device 1 is used.

[0023] Each polarized light beam L0 diffused and irradiated by the lighting device 2 reaches a wide area on the surface of the object S. The object S, such as food, has the property of producing specularly reflected light L1 and diffusely reflected light L2 when light is incident on it. In particular, when polarized light beam L0 is incident on the object S, the degree of polarization of the specularly reflected light L1 generated based on the incident light beam L0 is relatively high, and the degree of polarization of the diffusely reflected light L2 generated based on the incident light beam L0 is relatively low. Furthermore, if a foreign object FS, such as a plastic film, that has the property of transmitting polarized light, is present on the surface of the object S, the polarized light beam L0 incident on the foreign object FS generates specularly reflected light L3 that is specularly reflected by the surface of the foreign object FS, specularly reflected light L4 that passes through the foreign object FS and is specularly reflected by the back surface of the foreign object FS, and diffusely reflected light L5 that is diffusely reflected by the foreign object FS. In this case, the specularly reflected light L3 and L4 have a relatively higher intensity than the specularly reflected light L1, and the degree of polarization thereof is higher than that of the diffusely reflected light L2 and L5, just like the specularly reflected light L1. Furthermore, if the material of the foreign substance FS has birefringence, the polarization state of the specularly reflected light L4 will change from the polarization state of the incident light ray L0.

[0024] 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 image data corresponding to a plurality of different polarization components, for the same object S, from the camera 6 in order to two-dimensionally detect the reflectance or polarization state of the light reflected from the object S by utilizing the properties of the reflected light. Specifically, the image processing device 8 acquires four or more images of the same object S while rotating the rotatable waveplate 4 at predetermined angle intervals, the image data being used to calculate the Stokes parameters for each pixel using the rotating compensator method. In this way, the image processing device 8 acquires image data showing different polarization components by detecting light including specularly reflected light from the object S while rotating the rotatable waveplate 4.

[0025] FIG. 3 shows an example of multiple image data sets acquired by the image processing device 8 for the same object S, and FIG. 4 shows the change in luminance at one pixel relative to the rotation angle of the rotatable wave plate 4. In the example shown here, 18 pieces of image data were acquired while rotating the rotatable wave plate 4 in 10-degree increments within a range from 0 to 170 degrees. The graph shown in FIG. 4 shows the change in luminance at the pixel at position P1 on the image data shown in FIG. 3. As shown in this graph, the luminance of the polarized light component detected by the pixel varies periodically as the rotatable wave plate 4 is rotated.

[0026] Next, a description will be given of the configuration of an inspection system 100, which is an inspection device according to an embodiment. Fig. 5 shows a schematic configuration of the inspection system 100 according to an embodiment.

[0027] The inspection system 100 includes the image acquisition device 1 having the above-described configuration, a conveying device 11 such as a belt conveyor that conveys the object S in a predetermined direction, and a computer (inspection processing unit) 12 that calculates image data output from the image acquisition device 1. The image acquisition device 1 acquires image data of the object S conveyed by the conveying device 11, and outputs the acquired image data to the computer 12.

[0028] The computer 12 has the same hardware configuration as the image processing device 8. That is, the computer 12 is physically an arithmetic device incorporating a CPU or GPU as a processor, RAM or ROM as a recording medium, a communication module, an input / output module, etc. The computer 12 may acquire image data from the image processing device 8 via a cable, or may acquire image data from the image processing device 8 via wireless communication.

[0029] Functionally, the computer 12 performs an inspection process for the object S based on, for example, a plurality of image data using a rotation compensator method. That is, the computer 12 first obtains the brightness of one pixel from a plurality of image data obtained for the same object S.

[0030] Here, the luminance I of a pixel of each image data is theoretically expressed by the following formula (1): I=I0(2+S1-2S3sin2C+S1cos4C+S2sin4C) (1) In the above formula (1), I0 represents the average luminance of all reflected light incident on the imaging device 7, S1, S2, and S3 represent the Stokes parameters, and C represents the rotation angle of the rotatable wave plate 4. The Stokes parameter S1 represents the difference in intensity between orthogonal polarization components, the Stokes parameter S2 represents the difference in intensity between the +π / 4 polarization component and the -π / 4 polarization component, and the Stokes parameter S3 represents the difference in intensity between the right-handed circular polarization component and the left-handed circular polarization component. The degree of polarization p at a given pixel is expressed by the following formula (2): p=S1 2 +S2 2 +S3 2 (2)

[0031] The computer 12 processes the brightness of one pixel of the multiple image data using the relationship in equation (1) above to calculate the Stokes parameters S1, S2, S3, and brightness I0 for that pixel. For example, the computer 12 calculates the Stokes parameters S1, S2, S3 as a Fourier series. Furthermore, the computer 12 repeats the same calculation for all pixels of the image data to calculate the Stokes parameters S1, S2, S3, and brightness I0 for all pixels.

[0032] In addition, the computer 12 can obtain an inspection result image showing the distribution of polarization in the light reflected from one object S by performing one of the following calculations based on the Stokes parameters S1, S2, S3 and brightness I0 of each pixel obtained for one object S: (Specular reflection light distribution) p×I0 (Linear polarization distribution) S1×I0 (Linear polarization distribution) S2×I0 (Circular polarization distribution) S3×I0 The computer 12 then outputs one or more inspection result images obtained for one object S to an output device such as a display. The computer 12 may also output the inspection result images to an external device via a network, a recording medium, etc.

[0033] Next, a method for inspecting the object S using the inspection system 100 will be described, and an image acquisition method according to this embodiment will be described in detail. Fig. 6 is a flowchart showing the steps of the method for inspecting the object S.

[0034] First, when the inspection process of the object S is started, the conveying device 11 starts conveying the object S (step S1). After that, when the object S is conveyed by the conveying device 11 into the irradiation range of the polarized light of the illumination device 2, the polarized light from the illumination device 2 is irradiated onto the object S (step S2).

[0035] In response, reflected light generated on the surface of the object S is incident on the camera 6 via the rotating wave plate 4 and the polarizing plate 5, and a two-dimensional image of the reflected light is detected by the camera 6, thereby outputting image data (S3). At this time, detection of the two-dimensional image of the reflected light is repeated while rotating the rotating wave plate 4, and multiple image data reflecting the detection results of multiple polarization components of the reflected light are output.

[0036] 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 Stokes parameters, etc. for each pixel based on the brightness of each pixel of the image data (step S4). Next, the computer 12 calculates the Stokes parameters, etc. for each pixel to acquire one or more inspection result images showing the polarization distribution of the light reflected from the object S (step S5). The inspection result image is at least one of a specular reflection light distribution, a linear polarization distribution, and a circular polarization distribution. Finally, the computer 12 outputs one or more inspection result images of the object S to an output device as images in which a foreign substance FS present on the object S is detected (step S6), thereby completing the inspection process for the object S.

[0037] 7 to 9 show examples of images acquired by the inspection process of the inspection system 100. FIG. 7 is an original image of reflected light acquired by the camera 6 with the rotating wavelength plate 4 and polarizing plate 5 removed. FIG. 8 is an inspection result image, which is a specular reflection light distribution acquired by the computer 12. FIG. 9 is an inspection result image, which is a linear polarization distribution acquired by the computer 12. Note that since the illumination light is circularly polarized, the linear polarization distribution refers to an image that shows the degree of change in the polarization state. FIG. 10 is a graph showing the luminance distribution at the position of line P2 on the three images shown in FIGS. 7 to 9. When the evaluation value C is calculated by dividing the average luminance at positions where a foreign substance FS is present in this luminance distribution by the average luminance at positions where a foreign substance FS is not present, the result is C=1.5 for FIG. 7, C=3.3 for FIG. 8, and C=7.4 for FIG. 9. These results demonstrate that the image of the foreign substance FS is clearly visible in the inspection result image acquired by the inspection system 100, and that the inspection system 100 can effectively detect the foreign substance FS.

[0038] According to this embodiment, it is possible to evaluate the distribution of the polarization state of light that is polarized and specularly reflected by the object S, based on image data detected by the image acquisition device 1. As a result, it is possible to detect with high accuracy any foreign matter FS on the object S that has the property of transmitting and reflecting polarized light.

[0039] In the image acquisition device 1, the illumination device 2 is configured to irradiate the target object S with diffused polarized light. This makes it possible to detect foreign objects FS that have the property of transmitting and reflecting polarized light over a wide range when targeting a three-dimensional target object S such as food.

[0040] Furthermore, in the image acquisition device 1, the illumination device 2 is configured to irradiate circularly polarized light. In this case, even if the foreign matter FS has birefringence, the foreign matter FS can be detected with high accuracy.

[0041] Furthermore, in the image acquisition device 1, the imaging device 7 includes a polarizing plate 5 and is configured to detect reflected light via the polarizing plate 5. In this way, the distribution of the polarization state of light that is specularly reflected from the object S can be evaluated with a simple configuration.

[0042] Furthermore, in the image acquisition device 1, the imaging device 7 further includes a rotating wave plate 4 and is configured to detect reflected light via the rotating wave plate 4. In this case, the distribution of the polarization state of light that is specularly reflected from the object S can be evaluated with high accuracy by calculation using the Stokes parameters, etc.

[0043] Alternatively, the inspection system 100 according to this embodiment can efficiently detect objects on multiple objects S that have the property of transmitting and reflecting polarized light while transporting the multiple objects S.

[0044] Various embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments, and may be modified or applied to other things within the scope that does not change the gist of the claims.

[0045] 11 is a schematic diagram of an image acquisition device 1A according to a first modified example. The image acquisition device 1A has a configuration 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 2a and a polarizing sheet 2c attached in proximity to the light irradiation surface of the main body 2a, and irradiates linearly polarized light in a predetermined polarization state toward the object S by diffusing the polarized light.

[0046] 12 and 13 show examples of images acquired by the inspection process of the inspection system 100 including the image acquisition device 1A. FIG. 12 shows an original image of reflected light acquired by the camera 6 with the rotating wavelength plate 4 and polarizing plate 5 removed. FIG. 13 shows an inspection result image, which is a circular polarization distribution acquired by the computer 12. Note that since the illumination light is linearly polarized, the circular polarization distribution refers to an image that shows the degree of change in the polarization state. FIG. 14 is a graph showing the luminance distribution at the position of line P3 on the two images shown in FIGS. 12 and 13. When the evaluation values ​​C corresponding to the two foreign substances FS are calculated based on this luminance distribution, the results are C = 1.1, 1, and 3 for FIG. 12 and C = 5.9 and 7.1 for FIG. 13. These results demonstrate that the foreign substance FS is clearly visible in the inspection result image acquired by the inspection system 100, demonstrating that the inspection system 100 can effectively detect the foreign substance FS.

[0047] FIG. 15 is a schematic diagram of an image acquisition device 1B according to a second modified example. The image acquisition device 1B has a configuration in which the rotating wavelength plate 4 and polarizing plate 5 in the image acquisition device 1 are replaced with a rotating polarizing plate 5B. The rotating polarizing plate 5B is supported rotatably around a rotation axis that is aligned with the direction of incidence of light from the rectangular prism mirror 3 so as to change the polarization direction of the linearly polarized light to be transmitted. The image processing device 8 of the image acquisition device 1B repeatedly captures two-dimensional images of a single object S using the camera 6 while changing the rotation angle of the rotating polarizing plate 5B, and acquires and stores the resulting multiple pieces of image data. The computer 12 acquires the multiple pieces of image data acquired by the image processing device 8 as inspection result images.

[0048] 16 and 17 show examples of images acquired by the inspection process of the inspection system 100 including the image acquisition device 1B. FIG. 16 shows an original image of reflected light acquired by the camera 6 with the rotating polarizer 5B removed, and FIG. 17 shows a calculated image based on the inspection result image acquired by the computer 12. For example, a calculated image can be obtained by subtracting the average value of each of a first inspection result image and a second inspection result image acquired with the rotating polarizer 5B rotated at different angles, and then calculating the absolute value of the difference between the first inspection result image and the second inspection result image from which the average value has been subtracted. FIG. 18 is a graph showing the luminance distribution at the position of the line P4 on the two images shown in FIGS. 16 and 17. When the evaluation values ​​C corresponding to the two foreign substances FS in this luminance distribution were calculated, the results were C = 1.2 and 1.3 in the case of FIG. 16 and C = 9.2 and 11.4 in the case of FIG. 17. From this result, it can be seen that the image of the foreign matter FS stands out in the inspection result image obtained by the inspection system 100, and that the inspection system 100 can effectively detect the foreign matter FS.

[0049] In the image acquisition device 1B according to the second modification, an imaging device 201 having the configuration shown in Fig. 19 may be used instead of the imaging device 7. The imaging device 201 is configured to split the reflected light from the object S incident on the right-angle prism mirror 3 into a plurality of polarized light components, and form a two-dimensional image of the two split polarized light components on the light receiving surface of an internal imaging element. The configuration of the imaging device 201 will be described below.

[0050] As shown in Figure 19, the imaging device 201 is configured by incorporating a collimator lens 203, an imaging lens 204, a front-stage polarizing beam splitter 205a, a rear-stage polarizing beam splitter 205b, a front-stage mirror 206a, a rear-stage mirror 206b, and an imaging lens moving mechanism 208 within a housing 202.

[0051] A circular field stop 209 is provided at the center of one end surface of a cylindrical portion 202a that constitutes a part of the housing 202. The field stop 209 has a stop adjustment mechanism 214 that can variably set its inner diameter (width). The collimator lens 203 is aligned along its optical axis A. １is fixed inside the other end of the cylindrical portion 202a so that it coincides with the central axis of the cylindrical portion 202a, i.e., the central axis of the field stop 209. With this structure, the field stop 209 is aligned with the optical axis A １ The end face of the cylindrical portion 202a of the housing 202 is fixed facing the right-angle prism mirror 3, and the reflected light from the right-angle prism mirror 3 is guided from the field stop 209 to the optical axis A. １ The collimator lens 203 receives the reflected light that has passed through the field stop 209, converts the reflected light into parallel light, and directs the parallel light into the housing 202 along the optical axis A. １ By adjusting the aperture of the field stop 209, it is possible to limit the field range on the imaging plane of the light reflected from the object.

[0052] On the opposite side of the cylindrical portion 202a of the housing 202, a cylindrical portion 202b is integrally formed, which is positioned coaxially with the cylindrical portion 202a, and a circular window portion 210 is provided in the center of the end face of this cylindrical portion 202b, through which an optical image formed based on reflected light input from the cylindrical portion 202a side passes to the outside. A camera 6 is attached to the end face of the cylindrical portion 202b of the housing 202. The camera 6 has an image sensor 6a built in, and the light receiving surface 6b of the image sensor 6a faces the window portion 210, and the center of the light receiving surface 6b is aligned with the optical axis A of the collimator lens 203. １ The right-angle prism mirror 3 is mounted so that the light receiving surface 6b is positioned above the right-angle prism mirror 3 and so that the light receiving surface 6b coincides with the position at which the optical image output from the window 210 is formed. With this mounting structure, the optical image formed by the imaging device 201 can be captured by the camera 6 with the imaging device 201 arranged coaxially with the right-angle prism mirror 3.

[0053] Furthermore, the optical axis A inside the housing 202 between the cylindrical portions 202a and 202b １ On the top, a front-stage polarizing beam splitter 205a and a rear-stage polarizing beam splitter 205b, which are light separation elements, are detachably arranged. These polarizing beam splitters 205a and 205b are integrated and arranged along the optical axis A １The polarizing beam splitters 205a and 205b may be integrated with a front-stage mirror 206a and a rear-stage mirror 206b (described later) so as to be detachable.

[0054] The front-stage polarizing beam splitter 205a is positioned adjacent to the collimator lens 203 and is aligned with the optical axis A １ Its center is located on the top, and its light receiving surface is on the optical axis A. １ The front-stage polarizing beam splitter 205a is disposed so as to be inclined at 45 degrees with respect to the plane perpendicular to the plane of the collimator lens 203. The front-stage polarizing beam splitter 205a splits and transmits linearly polarized light (hereinafter referred to as "first split light") at a predetermined angle θ1 out of the parallel light output from the collimator lens 203, and directs the first split light along the optical axis A. １ At the same time, the front-stage polarizing beam splitter 205a splits and reflects the linearly polarized light (hereinafter referred to as the "second split light") of the parallel light at a predetermined angle θ2 different from the predetermined angle θ1, and outputs the second split light along the optical axis A. １ 19. The output is perpendicular to the direction of the arrow (downward in FIG. 19).

[0055] The rear polarizing beam splitter 205b is located at a position away from the front polarizing beam splitter 205a toward the window portion 210, and its center is aligned with the optical axis A. １ The light receiving surface is shifted a predetermined distance from the top toward the rear mirror 206b, and the light receiving surface is aligned with the optical axis A. １ The rear polarizing beam splitter 205b is configured with an optical member having the same transmission and reflection characteristics as the front polarizing beam splitter 205a, and by further transmitting the first split light that has passed through the front polarizing beam splitter 205a, the rear polarizing beam splitter 205b directs the first split light along the optical axis A. １ At the same time, the rear polarizing beam splitter 205b reflects the second split light that has been reflected by the front polarizing beam splitter 205a and then passed through the front mirror 206a and the rear mirror 206b, and directs the second split light along the optical axis A. １ The light is output toward the window 210 in a direction inclined with respect to the direction of the arrow.

[0056] That is, these polarizing beam splitters 205a and 205b are light splitting elements that split the parallel light from the collimator lens 203 into two polarized components, namely, first and second split lights.

[0057] The front mirror 206a is provided at a distance from the front polarizing beam splitter 205a in the reflection direction of the second split light, and the angle of the light receiving surface of the front mirror 206a is set to be equal to the angle of the optical axis A １ The front mirror 206a is set to be inclined at 45 degrees with respect to the plane perpendicular to the front mirror 206a. The front mirror 206a directs the second split light output from the front polarizing beam splitter 205a along the optical axis A. １ The rear mirror 206b is spaced apart from the front mirror 206a in the reflection direction of the second split light and is disposed so as to face the light receiving surface of the rear polarizing beam splitter 205b. The angle of the light receiving surface of the rear mirror 206b is set to be equal to or larger than the optical axis A. １ The rear mirror 206b is set to be inclined by 45+α degrees (α is a preset angle) with respect to the plane perpendicular to the optical axis A. １ The light is reflected toward the light receiving surface of the rear polarizing beam splitter 205b along a direction intersecting the direction of the polarizing beam splitter 205b.

[0058] Furthermore, the optical axis A between the rear polarizing beam splitter 205b and the window portion 210 １ An imaging lens 204 is provided on the upper surface of the imaging lens 204, and is supported by an imaging lens moving mechanism 208 so that its position can be adjusted. ２ is optical axis A １ , and the imaging lens moving mechanism 208 moves the optical axis A ２ is optical axis A １ While maintaining a parallel state to the optical axis A １ Specifically, the imaging lens 204 is configured to be movable in a direction perpendicular to the optical axis A by an imaging lens moving mechanism 208. ２ is optical axis A １ and a first state that coincides with the optical axis A ２ is optical axis A １The imaging lens 204 can be set to a first state, in which the first polarizing beam splitter 205a is shifted a predetermined distance from the first state, and a second state, in which the second polarizing beam splitter 205b is shifted a predetermined distance from the first state. At this time, the center of the rear-stage polarizing beam splitter 205b is positioned on the optical axis of the imaging lens 204. This reduces vignetting. The imaging lens movement mechanism 208 may be a slide mechanism that continuously adjusts the position of the imaging lens 204, or a switching mechanism that switches between 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 movement mechanism 208, the imaging lens 204 receives first and second split light beams split from the reflected light via the polarizing beam splitters 205a and 205b, and forms the split light beams as separated first and second optical images on the light-receiving surface 6b of the camera 6 attached to the outside of the window 210. On the other hand, the imaging lens 204 is set to a first state by the imaging lens moving mechanism 208, and when the polarizing beam splitters 205a and 205b are removed, the imaging lens 204 receives reflected light only via the collimator lens 203 and forms a single optical image on the light receiving surface 6b inside the camera 6 attached to the outside of the window portion 210.

[0059] The imaging device 201 configured as described above can be used in both an observation mode (hereinafter referred to as "single view mode") in which the reflected light is observed as a single optical image by the camera 6, and an observation mode (hereinafter referred to as "double view mode") in which the reflected light is separated into two optical images by the camera 6 and observed. The image acquisition device 1B employing the imaging device 201 can simultaneously obtain images of multiple polarization components of the reflected light, and can instantly evaluate the distribution of the polarization state of light that is polarized by the object S and specularly reflected.

[0060] In the above embodiment, it is preferable that the light irradiation device irradiates the target with diffused polarized light, thereby making it possible to detect objects that transmit and reflect polarized light over a wide range when a three-dimensional target is the target.

[0061] In the above embodiment, it is also preferable that the light irradiation device irradiates polarized light that is circularly polarized, in which case the object can be detected with high accuracy even if the object has birefringence.

[0062] Furthermore, in the above-described embodiment, it is also preferable that the light irradiation device irradiates polarized light that is linearly polarized, which makes it possible to easily evaluate the distribution of changes in the polarization state based on the detected image, and to easily detect objects that transmit and reflect polarized light.

[0063] Furthermore, in the above-described embodiment, it is also preferable that the imaging device includes a polarizing plate and detects light specularly reflected through the polarizing plate. In this way, the distribution of the polarization state of light polarized by an object and specularly reflected can be evaluated with a simple configuration.

[0064] In the above embodiment, it is preferable that the imaging device further includes a wave plate and detects light specularly reflected through the wave plate. In this case, the distribution of the polarization state of light specularly reflected from the object can be evaluated with high accuracy by calculation.

[0065] Furthermore, in the above embodiment, it is preferable that the imaging device includes a light separation element that separates the specularly reflected light into multiple light components, and captures the multiple light components to obtain image data including multiple images. In this case, multiple images can be obtained simultaneously, and the distribution of the polarization state of light polarized by the object and specularly reflected can be immediately evaluated.

[0066] The image acquisition device of 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 polarized light that is specularly reflected by the object and acquires image data containing different polarization components of the light; and an image processing unit that detects objects that are present on the object and through which the polarized light passes, based on multiple images."

[0067] The image acquisition device of the embodiment may be [2] "the image acquisition device according to the above [1], in which the light irradiation device irradiates the object with diffused and polarized light."

[0068] The image acquisition device of the embodiment may be [3] "the image acquisition device according to the above [1] or [2], in which the light irradiation device irradiates polarized light that is circularly polarized."

[0069] The image acquisition device of the embodiment may be [4] "the image acquisition device according to the above [1] or [2], in which the light irradiation device irradiates polarized light that is linearly polarized."

[0070] The image acquisition device of the embodiment may be [5] "an image acquisition device according to any one of [1] to [4] above, in which the imaging device includes a polarizing plate and detects light specularly reflected through the polarizing plate."

[0071] The image acquisition device of the embodiment may be [6] "the image acquisition device described in [5] above, in which the imaging device further includes a wavelength plate and detects light specularly reflected through the wavelength plate."

[0072] The image acquisition device of the embodiment may be [7] "an image acquisition device according to any one of [1] to [4] above, which includes a light separation element that separates specularly reflected light into multiple light components, and captures the multiple light components to acquire image data including multiple images."

[0073] The inspection device of the embodiment is [8] "an inspection device comprising an image acquisition device described in any one of [1] to [7] above, a conveying device that conveys an object in a predetermined direction, and an inspection processing unit that inspects the object based on data output from the image acquisition device."

[0074] The image acquisition method of the embodiment is [9] "an image acquisition method comprising a light irradiation step of irradiating an object with polarized light, an imaging step of detecting the polarized light specularly reflected by the object and acquiring image data containing different polarization components of the light, and an image processing step of detecting objects present on the object through which the polarized light passes, based on multiple images."

[0075] 1, 1A, 1B...image acquisition device, 2...illumination device (light irradiation device), 4...rotating wavelength plate, 5...polarizing plate, 5B...rotating polarizing plate, 7, 201...imaging device, 205a, 205b...polarizing beam splitter (light separation element), 8...image processing device (image processing section), 11...conveying device, 12...computer (inspection processing section), 100...inspection system (inspection device), S...object, FS...foreign matter.

Claims

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

2. The light irradiation device irradiates the polarized light toward the object in a diffuse manner. The image acquisition device of claim 1 .

3. The light irradiation device irradiates the polarized light which is circularly polarized.

3. An image acquisition device according to claim 1 or 2.

4. The light irradiation device irradiates the polarized light which is linearly polarized light.

3. An image acquisition device according to claim 1 or 2.

5. The imaging device includes a polarizing plate and detects the specularly reflected light through the polarizing plate.

3. An image acquisition device according to claim 1 or 2.

6. The imaging device further includes a wave plate and detects the specularly reflected light through the wave plate.

6. An image acquisition device according to claim 5.

7. the imaging device includes a light separation element that separates the specularly reflected light into a plurality of light components, and captures the plurality of light components to obtain the image data including a plurality of images.

3. An image acquisition device according to claim 1 or 2.

8. An image acquisition device according to claim 1 or 2; A conveying device that conveys the object in a predetermined direction; an inspection processing unit that inspects the object based on data output from the image acquisition device; An inspection device comprising:

9. A light irradiation step of irradiating the object with polarized light; an imaging step of detecting light that is specularly reflected by the object and acquiring image data including different polarization components of the light; an image processing step of detecting an object that is present on the target object and through which the polarized light passes, based on the image data; An image acquisition method comprising:

10. In the light irradiation step, the polarized light is diffused and irradiated toward the object. The image acquisition method according to claim 9.

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

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

13. In the imaging step, the specularly reflected light is detected via a polarizing plate. The image acquisition method according to claim 9 or 10.

14. In the imaging step, the specularly reflected light is detected via a wave plate. The image acquisition method according to claim 13.

15. In the imaging step, the specularly reflected light 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. The image acquisition method according to claim 9 or 10.