Imaging device, article inspection device, and imaging method

Abstract

An imaging device (11) comprises an illumination unit (20), a camera (30), an optical path control member (40), and a control unit. The illumination unit (20) illuminates an article (12) disposed at an imaging position (SP). The camera (30) is disposed at a position on the reverse side of the article (12) from the illumination unit (20). The optical path control member (40) has a sheet shape and is disposed between the illumination unit (20) and the article (12). There are light-blocking parts (41) and light-transmitting parts (42) arranged in a two-dimensional arrangement pattern on a sheet surface (40S). Due to the control unit, the camera (30) forms an image (Img) of transmitted light that has passed through the article (12) and the light-transmitting parts (42). The pitch of the light-transmitting parts (42) is equal to or less than the pixel resolution of the camera (30). A transmitted optical axis (C2), which is the optical axis of transmitted light that is regulated to a prescribed viewing angle by the light-blocking parts (41) and has passed through the light-transmitting parts (42), is inclined with respect to an imaging optical axis (C1) of the camera (30).

Description

Imaging Device, Article Inspection Device, and Imaging Method

[0001] The present invention relates to an imaging device, an article inspection device, and an imaging method for imaging an article having at least a part of a transparent or translucent portion through which light can pass.

[0002] For example, in Patent Documents 1 and 2, an article inspection device is disclosed in which an optical path control member having a plurality of slits arranged in one direction for forming a light and dark pattern is disposed between an illumination unit and an article, and a camera images an image of transmitted light that has passed through the article through the light and dark pattern.

[0003] The article inspection device described in Patent Document 1 includes pattern irradiation means composed of a shade for forming a light and dark pattern (an example of an optical path control member) in which a light-transmitting portion and a light-blocking portion are continuous in one direction and an illumination light source, provided on the back side of a translucent workpiece. A photographing means (camera) that sandwiches the workpiece and faces the irradiation means photographs the light and dark pattern irradiated by the pattern irradiation means through the workpiece. Based on the change (bright spot) in the amount of emitted light (luminance) in the photographed image, defects on the surface of the workpiece are detected. By the light diffusion means, the light transmitted through the light-transmitting portion is guided as diffused light to the light-blocking portion side, and the appearance of the defects in the dark portion as bright spots is promoted as the amount of emitted light in the dark portion increases.

[0004] The article inspection device described in Patent Document 2 includes an illumination unit that illuminates transmitted light, a photographing unit (camera) that receives the transmitted light and photographs a product (an example of an article), and a slit plate (an example of an optical path control member) that forms light and dark stripes in which bright and dark portions are alternately repeated with respect to the product. The slit plate has a configuration in which light-transmitting portions and light-blocking portions are alternately formed. The article detection device makes a photographed image into a multi-tone grayscale image, and in the inspection region, the boundaries of each fine particle of the transparent fine particle body that appears in an intermediate tone are detected as points of change in light and dark, and based on the number of change points, the coating state of the transparent fine particle body is determined.

[0005] Japanese Unexamined Patent Application Publication No. 2020-91132 Japanese Unexamined Patent Application Publication No. 2010-204051

[0006] However, the article inspection apparatus described in Patent Documents 1 and 2 uses a light-dark pattern forming shade or slit plate that forms a light-dark pattern in which dark and light areas are aligned in one direction, resulting in a bias in the direction of light from the light-transmitting area or slit to the light-shielding area (dark area). Furthermore, there is a demand to acquire images that can identify characters and symbols formed on the article by embossing or other irregularities. However, there is a problem in obtaining images in which characters and symbols formed by embossing or other irregularities are easily identifiable. In addition, there is a problem in that defects consisting of irregularities such as scratches, not just embossing, are difficult to identify due to the effects of light refraction, etc. Thus, even when images are captured that include characters, symbols, etc. formed by embossing or other irregularities, it is difficult to identify the embossing of characters and symbols. The imaging apparatus and article inspection apparatus described in Patent Documents 1 and 2 have the problem that it is difficult to identify embossing of characters and symbols.

[0007] The means for solving the above problems and their effects are described below. The imaging device for solving the above problems is an imaging device for imaging an article having at least a part of a transparent or semi-transparent portion that light can pass through, and comprises: an illumination unit for illuminating the article placed at the imaging position; a camera positioned opposite the illumination unit to the article; a sheet-shaped optical path control member positioned between the illumination unit and the article and having light-shielding portions and light-transmitting portions arranged in a two-dimensional arrangement pattern on the sheet surface; and a control unit that causes the camera to image the article and the transmitted light that has passed through the light-transmitting portions to acquire an image, wherein the pitch of the light-transmitting portions is less than or equal to the pixel resolution of the camera, and the transmitted light axis, which is the optical axis of the transmitted light that passes through the light-transmitting portions and is restricted to a predetermined field of view by the light-shielding portions, is inclined at an acute angle with respect to the imaging optical axis of the camera. With this configuration, it is possible to capture an image in which recesses or protrusions such as embossing or scratches on the article can be easily identified.

[0008] In the above imaging device, the optical path control member has one or more sheet-like members and a light-transmitting portion formed on the sheet-like member and extending in the thickness direction of the sheet-like member, and the optical path control member may be arranged in a position inclined with respect to the imaging optical axis. With this configuration, since the optical path control member 40 is arranged in a position inclined with respect to the imaging optical axis, it is possible to capture images in which recesses or protrusions such as embossing or scratches on an article are easily identifiable with shading.

[0009] In the above imaging device, the optical path control member may have one or more sheet-like members and one or more light-transmitting portions formed on the sheet-like members, extending in an oblique direction such that the transmitted light axis is inclined at the acute angle with respect to the thickness direction of the sheet-like member, and the optical path control member may be arranged such that the transmitted light axis of the one or more light-transmitting portions is inclined with respect to the imaging optical axis. With this configuration, the angle at which the optical path control member 40 is inclined with respect to the imaging optical axis can be reduced. Therefore, the gradation of light and dark in the captured image IS can be suppressed to a small extent. Images can be captured that make it easy to identify recesses or protrusions such as embossing or scratches on an article.

[0010] In the above imaging device, the light-transmitting portion may be provided in two or more types, each extending in the diagonal direction, with the transmitted light axis inclined at two or more different angles relative to the thickness direction of the sheet-like member, and the optical path control member may be positioned such that the transmitted light axes of the two or more types of light-transmitting portions are inclined with respect to the imaging optical axis. With this configuration, since there are two or more types of light-transmitting portions with the transmitted light axis extending at two or more different angles inclined with respect to the thickness direction of the sheet-like member, the angle at which the optical path control member is inclined with respect to the imaging optical axis can be reduced. Therefore, the gradation of light and dark in the captured image can be suppressed to a small extent. Images can be captured that make it easy to identify recesses or protrusions such as embossing or scratches on an article.

[0011] The above-described imaging device further includes an adjustment unit for adjusting the contrast of the image, and the adjustment unit may be configured to adjust at least one of the following: the attitude angle of the optical path control member, the lens position of the camera, and the focal length of the camera. This configuration makes it possible to increase the contrast of the image.

[0012] In the above imaging device, the camera may image the article multiple times under multiple conditions in which the direction in which the transmitted light axis of the light-transmitting portion of the optical path control member is tilted with respect to the imaging light axis is different. With this configuration, multiple types of images with shading of recesses or protrusions such as embossing or scratches can be obtained with different light irradiation directions. By obtaining multiple types of images in which shading of embossing or scratches occurs in different locations, the accuracy of identifying recesses or protrusions such as embossing or scratches can be improved.

[0013] In the above-described imaging device, the article may be a container having an opening and a bottom that is either a transparent or translucent portion. The container is positioned at the imaging location with the opening facing the camera and the bottom facing the illumination unit, and the camera may image the inner bottom surface of the bottom through the opening. With this configuration, the camera images the inner bottom surface of the bottom through the opening, so the bottom can be imaged without separating the optical path control member and the bottom too far. For example, recesses or protrusions such as embossing or scratches formed on the bottom can be obtained as a well-defined, easily identifiable image.

[0014] An article inspection device that solves the above problems comprises an imaging device and an inspection processing unit that inspects recesses or protrusions of the article based on the image captured by the imaging device. With this configuration, recesses or protrusions such as embossing or scratches formed on the article can be inspected.

[0015] An imaging method that solves the above problems is an imaging method for imaging an article having at least a part of a transparent or semi-transparent portion that allows light to pass through, and includes illuminating the article placed at the imaging position with an illumination unit, and acquiring an image by imaging the article and the transmitted light that has passed through the transmitted light portion with a camera placed on the opposite side of the article from the illumination unit, with an optical path control member having a light-shielding portion and a light-transmitting portion arranged in two dimensions, placed between the illumination unit and the article, wherein the pitch of the light-transmitting portion is less than or equal to the pixel resolution of the camera, and the transmitted light axis, which is the optical axis of the transmitted light that passes through the light-transmitting portion and is restricted to a predetermined field of view by the light-shielding portion, is inclined at an acute angle with respect to the imaging optical axis of the camera. With this method, it is possible to capture an image in which recesses or protrusions such as embossing or scratches on the article can be easily identified.

[0016] According to the present invention, it is possible to capture images that make it easy to identify recesses or protrusions such as embossing or scratches on an article.

[0017] Figure 1 is a schematic side view showing an imaging device in the first embodiment. Figure 2 is a schematic front view showing an optical path control member. Figure 3 is a schematic front view showing an optical path control member different from that in Figure 2. Figure 4 is a schematic front view illustrating an optical path control member and its orientation angle. Figure 5 is a schematic front view illustrating an optical path control member and its orientation angle different from that in Figure 4. Figure 6 is a schematic front view illustrating an optical path control member and its orientation angle different from those in Figures 4 and 5. Figure 7 is a schematic side view illustrating the operation of an optical path control member in an imaging device. Figure 8 is a schematic side view illustrating the effect of an optical path control member and its orientation angle on the image in an imaging device. Figure 9 is a schematic plan view showing an imaging system comprising multiple imaging devices. Figure 10 is a schematic side view showing the imaging system in Figure 9. Figure 11 is a block diagram illustrating the electrical configuration of an article inspection device. Figure 12 is a schematic diagram illustrating the pixel resolution of a camera. Figures 13(a) to 13(e) are schematic diagrams showing images determined by the pixel resolution of the camera and the pitch of the light-transmitting portion. Figure 14 shows an image captured by an imaging device of a comparative example without an optical path control member. Figure 15 shows an image captured by an imaging device with an optical path control member, as opposed to the comparative example without a tilted optical path control member. Figure 16 shows an image captured by an imaging device with a tilted optical path control member. Figure 17 shows an image captured by an imaging device with a tilted optical path control member. Figure 18 shows an image captured by an imaging device with a tilted optical path control member. Figure 19 shows an image captured by an imaging device with a tilted optical path control member. Figure 20 is a schematic side view showing an imaging device in the second embodiment. Figure 21 is a schematic side view showing an imaging device in the second embodiment that differs from Figure 20. Figure 22 is a schematic front view showing an optical path control member. Figure 23 is a graph showing the relationship between the angle of the transmitted optical axis and the transmittance in the optical path control member. Figure 24 is a schematic partial side view of an imaging device illustrating the field of view of the optical path control member.

[0018] (First Embodiment) The imaging device and the article inspection device will be described below with reference to the drawings. The imaging device 11 shown in Figure 1 images an article 12 which has at least a part of a transparent portion that light can pass through. The imaging device 11 acquires an image of the target portion of the article 12 by imaging the target portion of the article 12. In the example shown in Figure 1, the article 12 is a container 13, for example, a PET bottle. The imaging device 11 images the letters and symbols engraved on the bottom 16 of the container 13, which is a PET bottle. Letters and symbols are drawn on the bottom 16 of the container 13, which is made of PET, by embossing 19 (see Figure 7) which consists of three-dimensional reliefs. Since the letters and symbols made of embossing 19 are only engraved by reliefs, if an image is taken by irradiating light from the front, for example, the letters and symbols of embossing 19 may be difficult to distinguish.

[0019] Article 12 may be a bottle made of a transparent synthetic resin other than PET (polyethylene terephthalate). Article 12 may be a transparent body consisting entirely of transparent parts. Article 12 may be colorless and transparent, but may also be colored and transparent. Article 12 may have a label attached to it. The label may be attached to the body or shoulder of Article 12. Alternatively, Article 12 may have text or a design printed on the body or shoulder instead of a label. Furthermore, Article 12 may be a glass container. The glass container may have at least a portion of a transparent part that allows light to pass through. The transparent portion of the glass container may be colorless and transparent or colored and transparent. The glass container may be formed entirely of transparent parts. Article 12 may also be an article having at least a portion of a translucent part that allows light to pass through.

[0020] <Basic Configuration of Imaging Device 11> First, the configuration of the imaging device 11 will be described with reference to Figure 1. As shown in Figure 1, the imaging device 11 comprises an illumination unit 20, a camera 30, and an optical path control member 40. The imaging device 11 acquires a desired image of the article 12 by having the camera 30 image the article 12. In this embodiment, an example of a transparent article 12 in which the entire article 12 is transparent will be described, but an article 12 having a transparent part may also be used.

[0021] In the example shown in Figure 1, article 12 is a transparent container 13. The container 13 is, for example, a PET bottle or a glass container. The container 13 has a cylindrical body 15, a bottom 16, a shoulder 17, and a mouth 18. When article 12 is a container 13, it may have a shape with an axis AL, for example, but it may also have a shape without an axis AL. Also, the article 12 shown in Figure 1 is an empty container 13.

[0022] Article 12 is a container 13 having an opening 18 and a bottom 16 which is a transparent or translucent portion. The container 13 is positioned at the imaging position SP with the opening 18 facing the camera 30 and the bottom 16 facing the illumination unit 20. The camera 30 images the inner bottom surface of the bottom 16 through the opening 18.

[0023] During imaging, the article 12 is positioned at the imaging position SP. The article 12 is positioned such that its axis AL is parallel to the imaging optical axis C1 of the camera 30. The imaging device 11 may include a transport unit 70 (see Figure 9) that transports the article 12 along a path to the imaging position SP. The transport unit 70 may be a transport belt that transports the article 12, or it may move the article 12 relative to the camera 30 in a direction intersecting the imaging optical axis C1. Alternatively, the transport unit 70 may be an articulated robot that transfers the article 12 to the imaging position SP. In short, the transport unit 70 only needs to be able to maintain the position of the article 12 with the part to be imaged facing the camera 30, and transport the article without obstructing anything other than the optical path control member 40 between the bottom part 16, which is the object to be imaged, and the illumination unit 20.

[0024] The illumination unit 20 illuminates the article 12 placed at the imaging position SP. In the example shown in Figure 1, the illumination unit 20 illuminates the bottom 16 of the article 12, which is the part to be imaged. The illumination unit 20 may be, for example, a surface light emitter. The illumination unit 20 is positioned so that its light-emitting surface faces the bottom of the article 12 at the imaging position SP.

[0025] The camera 30 is positioned on the opposite side of the item 12 from the illumination unit 20. The camera 30 captures an image Img of the transmitted light that has passed through the item 12 from the illumination unit 20. In other words, the imaging device 11 employs a light transmission method. The camera 30 captures an image of the inner bottom surface of the container 13 (PET bottle), which is the item 12, as seen from the inside, looking through the mouth 18 into the bottom 16.

[0026] The optical path control member 40 is positioned between the illumination unit 20 and the article 12. The optical path control member 40 is, as an example, an optical path control sheet. The optical path control member 40 is a sheet-like member having light-shielding portions 41 and light-transmitting portions 42 arranged in a two-dimensional pattern on a sheet surface 40S. The optical path control member 40 has striped light-shielding portions 41 and striped light-transmitting portions 42 arranged alternately in a predetermined direction. The light-shielding portions 41 and light-transmitting portions 42 are arranged two-dimensionally along the sheet surface 40S of the optical path control member 40.

[0027] The light-shielding portion 41 has the same thickness as the sheet. The light-transmitting portion 42 is the portion sandwiched between the two light-shielding portions 41 and is composed of a space or a light-transmitting member. The light-transmitting portion 42 may be composed of, for example, a transparent resin material that can transmit light. For example, the gap between the light-shielding portions 41 may be filled with a transparent resin material.

[0028] The optical path control sheet constituting the optical path control member 40 may include a louver layer (light-shielding layer) having a louver structure and a transparent high-performance resin layer sandwiching the louver layer. The louver layer has a plurality of louvers that constitute the light-shielding portion 41. The louvers define the direction of the transmitted optical axis C2 and the viewing angle of the light-transmitting portion 42. The transmitted optical axis C2 is defined by the angle that the wall surface of the light-shielding portion 41 (louver) adjacent to the light-transmitting portion 42 makes with respect to the sheet surface 40S. In this embodiment, the louvers define the transmitted optical axis C2 in a direction perpendicular to the sheet surface 40S. That is, the transmitted optical axis C2 is 90 degrees with respect to the sheet surface 40S. In other words, the angle that the transmitted optical axis C2 makes with respect to the thickness direction of the sheet-like member 46A (hereinafter also referred to as the "sheet thickness direction") is 0 degrees. Here, the viewing angle is the angular range in which light from the illumination unit 20 (light source) irradiated from the back side can be seen when viewed from a direction perpendicular to the sheet surface 40S. In other words, the viewing angle is the angular range in which the light transmittance that diffused light from the illumination unit 20 irradiated from the back side of the optical path control sheet can transmit through the light-transmitting unit 42 is greater than 0 (zero). The viewing angle is narrowed to a predetermined angle by the louvers. Under conditions where the opening width of the light-transmitting unit 42, i.e., the louver pitch, is constant, the larger the thickness of the light-shielding unit 41 (thickness of the light-shielding layer), the narrower the viewing angle tends to be. Also, under conditions where the thickness of the light-shielding unit 41 is constant, the smaller the opening width of the light-transmitting unit 42 (louver pitch), the narrower the viewing angle tends to be. The narrower the viewing angle, the higher the directivity of the transmitted light. The viewing angle is, for example, a value within the range of 10 degrees to 140 degrees. Preferably, the viewing angle is, for example, a value within the range of 20 degrees to 130 degrees. Furthermore, it is preferable that the viewing angle be within the range of 30 degrees to 120 degrees. If the lower limit of this viewing angle range is too small, the range of angles in which the optical path control member 40 can be tilted while ensuring sufficient transmitted light intensity is easily restricted. This restriction on the angle range limits the ease with which shadows are formed on uneven surfaces such as the embossing 19. Also, if the viewing angle is too large, the directivity of transmitted light decreases, making it difficult to form the desired shadows on uneven surfaces such as the embossing 19. For this reason, the viewing angle is preferably within the range defined by the above values. However, a viewing angle outside the above range may also be used. For example, a viewing angle of 5 degrees or a viewing angle of 150 degrees may be used.

[0029] The optical path control sheet may be configured such that the optical path of the emitted light, which is emitted after the incident light passes through the light-transmitting portion 42, is defined by the louvers according to the angle of incidence of the incident light with respect to the sheet surface 40S. The optical path control sheet may also be configured to diffuse light incident at an angle of incidence approximately parallel to the transmitted light axis C2, and transmit light incident at other angles of incidence. Examples of optical path control sheets include light control films manufactured by CCS Corporation. One example is the product name "LC Film" for flat illumination. Light control films are generally used as privacy films because they have a narrow viewing angle. The viewing angle of privacy films is usually about 60 degrees (about 30 degrees left and right). Note that optical path control sheets with structures other than the louver structure may also be used.

[0030] The thickness of the optical path control sheet constituting the optical path control member 40 is, for example, 0.01 mm to 1 mm. The optical path control sheet is not limited to a sheet made of a plate-like synthetic resin material with a thickness of 250 μm or more, but may also be a film made of a film-like synthetic resin material with a thickness of less than 250 μm. Furthermore, the optical path control sheet is not limited to 1 mm or less, but may have a thickness greater than 1 mm.

[0031] The pitch of the light-transmitting portion 42 is less than or equal to the pixel resolution of the camera 30. Details regarding the fact that the pitch of the light-transmitting portion 42 is less than or equal to the pixel resolution of the camera 30 will be described later. In addition, the striped light-shielding portion 41 extends in the direction of the sheet thickness. That is, the light-shielding portion 41 has a thickness that is approximately the same as or slightly thinner than the thickness of the sheet-like member 46A. The walls on both sides of a single striped light-shielding portion 41 are perpendicular to the sheet surface 40S. The light-transmitting portion 42 is formed between the walls on both sides of the light-shielding portion 41. For this reason, the light-transmitting portion 42 extends in a direction perpendicular to the sheet surface 40S.

[0032] The optical path control member 40 has one or more sheet-like members 46 and a light-transmitting portion 42 formed on the sheet-like members 46 and extending in the thickness direction of the sheet-like members 46. The optical path control member 40 is arranged such that the sheet-like members 46 are inclined with respect to the imaging optical axis C1.

[0033] In this embodiment, the optical path control member 40 is positioned in an inclined position where the sheet surface 40S is tilted by a predetermined acute angle with respect to the imaging optical axis C1 of the camera 30. In the optical path control member 40, the transmitted optical axis C2, which is the optical axis of the transmitted light that passes through the light-transmitting portion 42 and is restricted to a predetermined field of view by the light-shielding portion 41, is in a direction perpendicular to the sheet surface 40S. In other words, the transmitted optical axis C2 is parallel to the sheet thickness direction. The transmitted optical axis C2 is parallel to the axis of the light-transmitting portion 42 in a cross-section cut in a direction intersecting the direction of the stripes. In other words, the transmitted optical axis C2 is the optical axis of the transmitted light that has passed through the light-transmitting portion 42 within a predetermined angular range (light transmission angle) in this cross-section. The transmitted optical axis C2 of the light-transmitting portion 42 is inclined with respect to the imaging optical axis C1 of the camera 30. In this embodiment, by arranging the optical path control member 40 in an inclined position, the transmitted light axis C2 of the light-transmitting portion 42 is inclined at a predetermined acute angle with respect to the imaging light axis C1 of the camera 30. The optical path control member 40 is not limited to being formed from a transparent resin material; as long as it can maintain the shape of a sheet or film, the light-transmitting portion 42 may be an empty space without any filling.

[0034] The light-shielding portion 41 blocks some of the light (for example, visible light) L1 from the illumination unit 20. The light-transmitting portion 42 transmits some of the light L2 from the illumination unit 20. The camera 30 captures an image Img of the transmitted light Img, which is the light L2 that has been transmitted through the article 12, with L1 blocked by the light-shielding portion 41 and L2 transmitted through the light-transmitting portion 42.

[0035] Furthermore, the container 13 is positioned at the imaging position SP such that the imaging optical axis C1 of the camera 30 is parallel to the axis AL of the article 12, which is the container 13. By positioning the optical path control member 40 in an inclined position, it can be said that the transmitted optical axis C2 of the light-transmitting section 42 is inclined with respect to the axis AL of the article 12, which is the container 13.

[0036] If the optical path control member 40 is not tilted, the light in the direction pointed to by the transmitted optical axis C2 of the light-transmitting section 42 passes through the light-transmitting section 42, illuminating the bottom 16 of the article 12, which is a container 13 such as a PET bottle. In other words, the camera 30 can capture an image of the bottom 16 of the article 12 when light is shone on it from directly in front. However, in this case, the image of the bottom 16 of the article 12 when light is shone on it from directly in front will be an image in which it is difficult to distinguish the raised and recessed parts such as letters and symbols engraved with embossing 19.

[0037] <Arrangement Pattern of Light-Blocking and Light-Transmitting Sections in Optical Path Control Member 40> Next, the configuration of the optical path control member 40 will be described with reference to Figures 2 and 3. Figure 2 shows an optical path control member 43 with a single layer structure, composed of one optical path control sheet. Figure 3 shows an optical path control member 45 with a two-layer structure, in which two optical path control sheets shown in Figure 2 are stacked in orientations where the direction of the stripe pattern is rotated 90 degrees relative to each other. Thus, the optical path control member 40 may be an optical path control member 43 with a single layer structure as shown in Figure 2, or an optical path control member 45 with a two-layer structure.

[0038] In the single-layer optical path control member 43 shown in Figure 2, striped light-shielding portions 41 and striped light-transmitting portions 42 are arranged alternately in a predetermined direction (a direction intersecting the stripes). The striped light-shielding portions 41 extend in a direction perpendicular to the sheet surface 40S. The striped light-transmitting portions 42 open in a direction perpendicular to the sheet surface 40S.

[0039] In the two-layer optical path control member 45 shown in Figure 3, two single-layer optical path control sheets, as shown in Figure 2, are stacked and rotated 90 degrees. Therefore, in the plan view shown in Figure 3, the striped light-shielding portions 41 (horizontal stripes) that constitute the first layer of optical path control sheet and the striped light-shielding portions 41 (vertical stripes) that constitute the second layer of optical path control sheet intersect. For this reason, the light-shielding portions 41 are arranged in a grid pattern as shown in Figure 3. Alternatively, an optical path control member 40 having the same light-shielding portions 41 and light-transmitting portions 42 as in Figure 3 may be formed as a single-layer structure. For example, a single sheet-like member 46 may have square or circular light-transmitting portions 42 arranged in two dimensions.

[0040] The striped light-transmitting sections 42 that make up the first layer of the optical path control sheet are divided into multiple sections by the striped light-shielding sections 41 that make up the second layer of the optical path control sheet. Therefore, as shown in Figure 3, the light-transmitting sections 42, which consist of square-shaped openings, are arranged vertically and horizontally as windows in the grid-like light-shielding sections 41. Multiple light-transmitting sections 42 are scattered in a matrix-like manner vertically and horizontally.

[0041] The translucent portions 42, which are scattered in a matrix pattern vertically and horizontally, extend in a direction perpendicular to the sheet surface 40S. Multiple translucent portions 42 open in a direction perpendicular to the sheet surface 40S. <Configuration of the optical path control member 40> Next, the configuration and attitude angle of the optical path control member 40 will be described with reference to Figures 4 to 6. The optical path control member 40 shown in Figure 4 is an optical path control member 43 consisting of a single optical path control sheet with a horizontal stripe pattern. The transmitted light axis C2 of the translucent portion 42 makes a predetermined acute angle with the imaging light axis C1. That is, as shown in the right figure in Figure 4, the optical path control member 40 is tilted at an attitude angle PA indicated by the arrow in the figure. It is tilted at a predetermined angle so that the tip of the arrow is closer to the camera 30. A gradient of light and dark is formed in the image SI according to the direction of the tilt of the optical path control member 40. A gradient is formed in the image SI in which the end closer to the camera 30 is brighter and the end farther from the camera 30 is darker.

[0042] The optical path control member 40 shown in Figure 5 is an optical path control member 44 consisting of a single optical path control sheet with a vertical stripe pattern. The transmitted optical axis C2 of the light-transmitting section 42 forms a predetermined acute angle with the imaging optical axis C1. That is, as shown in the right-hand figure in Figure 5, the optical path control member 40 is tilted at the attitude angle PA indicated by the arrow in the figure. It is tilted at a predetermined angle so that the tip of the arrow is closer to the camera 30. A gradient of light and dark is formed in the image SI according to the direction of the tilt of the optical path control member 40. In the image SI, a gradient is formed in which the end closer to the camera 30 is brighter and the end farther from the camera 30 is darker.

[0043] The optical path control member 40 shown in FIG. 6 is an optical path control member 45 having a two-sheet structure in which one optical path control sheet with a horizontal stripe pattern shown in FIG. 4 and one optical path control sheet with a vertical stripe pattern shown in FIG. 5 are stacked with the stripe patterns intersecting each other. The transmission optical axis C2 of the light transmitting portion 42 forms a predetermined acute angle with the imaging optical axis C1. That is, as shown in the right diagram in FIG. 6, the optical path control member 40 is inclined at a posture angle PA indicated by an arrow in the figure. It is inclined at a predetermined angle in a direction in which the tip side of the arrow is closer to the camera 30. Depending on the inclination direction of the optical path control member 40, a light and shade gradation is formed in the image SI. In the image SI, a gradation is formed in which the end closer to the camera 30 is bright and the end farther from the camera 30 is dark.

[0044] <Function of the optical path control member 40> Next, referring to FIGS. 7 and 8, the transmission optical axis C2 and the posture angle of the optical path control member 40 will be described. In FIG. 7, only the bottom 16 portion of the article 12, which is the imaging target, is drawn. FIGS. 7 and 8 correspond to a view of the imaging device 11 in FIG. 1 seen from the opposite side, and the optical path control member 40 is inclined in the direction (orientation) opposite to that in FIG. 1.

[0045] As shown in FIG. 7, the optical path control member 40 is arranged at a posture angle in which the transmission optical axis C2 of the light transmitting portion 42 is inclined at a predetermined acute angle with respect to the imaging optical axis C1 of the camera 30. Diffused light L is emitted from the illumination unit 20. Light L2 in the direction along the transmission optical axis C2 of the light transmitting portion 42 among the diffused light L passes through the light transmitting portion 42. That is, the light passing through the light transmitting portion 42 is the light in the direction along the transmission optical axis C2. The light L hitting the light shielding portion 41 is shielded by the light shielding portion 41.

[0046] An embossed surface 19 is formed on the bottom 16 of the article 12. The embossed surface 19 consists of letters, symbols, etc., formed by raised and recessed areas. Transmitted light L2, which has passed through the light-transmitting portion 42 along the transmitted light axis C2, is irradiated onto the embossed surface 19. The light irradiated onto the embossed surface 19 is transmitted light L2 that is directed in a direction tilted at a predetermined angle with respect to the imaging light axis C1. The bottom 16 is perpendicular to the imaging light axis C1. Therefore, the transmitted light L2 is irradiated onto the embossed surface 19 formed on the bottom 16 from an oblique direction. In other words, even if the absolute value of the angle at which the surface of the embossed surface 19 is tilted with respect to the imaging light axis C1 is the same, the amount of light incident on the camera 30 changes between the positive and negative angles of the embossed surface 19. As a result, the shadow of the embossed surface 19 becomes larger. On the other hand, if the transmitted light axis C2 of the light-transmitting portion 42 of the optical path control member 40 is not tilted, the difference between the positive and negative angles disappears, and the shadow of the embossed surface 19 becomes smaller.

[0047] The predetermined acute angle, which is the angle between the imaging optical axis C1 and the transmitted optical axis C2, may be set appropriately within the range of acute angles. For example, the predetermined acute angle is a predetermined value within the range of 3 degrees to 60 degrees. Preferably, the predetermined acute angle is a predetermined value within the range of 6 degrees to 45 degrees. More preferably, it is a predetermined value within the range of 10 degrees to 35 degrees. If the lower limit of the predetermined acute angle range is too small, the angle between the direction of the illuminating light (transmitted light) and the surface of the imaging target (bottom surface of the bottom 16) tends to become large. In this case, it tends to be difficult to form shadows of uneven parts such as embossing 19 formed on the surface of the imaging target. On the other hand, if the upper limit of the predetermined acute angle range is too large, the amount of illuminating light (transmitted light) to the surface of the imaging target (bottom surface) such as the bottom 16 tends to become small. In this case, the difference in brightness of the shadows of uneven parts such as embossing 19 becomes a difference corresponding to the amount of light, so it is difficult to form a difference in shadow. Therefore, the range of the predetermined acute angle formed by the imaging optical axis C1 and the transmitted optical axis C2 should be within the range defined by the above numerical values.

[0048] As shown in FIG. 8, the optical path control member 40 is arranged at an attitude angle such that the transmission optical axis C2 of the light transmission part 42 intersects the imaging optical axis C1 at a predetermined acute angle. When viewed from the camera 30, the amount of light transmitted through the light transmission part 42 of the optical path control member 40 tends to be larger at positions closer to the camera 30. That is, when viewed from the camera 30, the larger the area of the region on the illumination part 20 visible through the light transmission part 42, the easier it is for the image to be brighter. For this reason, when the optical path control member 40 is arranged at an attitude angle such that the imaging optical axis C1 and the transmission optical axis C2 form an acute angle, an image with a gradation where the end closer to the camera 30 looks bright and the end farther from the camera 30 looks dark is easily obtained. Therefore, when viewed from the camera 30, as shown in the right diagrams in FIGS. 4 to 6, light and dark gradations are formed in the image SI according to the attitude angle of the optical path control member 40.

[0049] <Configuration of Imaging System 100> Next, referring to FIG. 9, an imaging system 100 including the imaging device 11 will be described. Although an image of the article 12 may be acquired using the imaging device 11 shown in FIG. 1, the ease of identifying the emboss 19 may change due to the influence of light and dark gradations. Therefore, an imaging system 100 including a plurality of imaging devices 11 with different directions of light and dark gradations may be configured. That is, as shown in FIG. 1, the imaging device 11 is not limited to being used alone, and an imaging system 100 including a plurality of imaging devices 11 shown in FIGS. 9 and 10 may be configured. The imaging system 100 acquires a plurality of images with different directions of light and dark gradations, for example, by irradiating light from different directions to the bottom 16 of the article 12 through the optical path control member 40.

[0050] As shown in FIG. 9, the imaging system 100 includes a transport unit 70 that transports the article 12 in the transport direction MD. The transport unit 70 transports the article 12 along a path passing through the imaging positions of each of the plurality of imaging devices 11. By the transport unit 70, the article 12 moves sequentially through the plurality of imaging devices 11. The container 13, which is the article 12, is transported by the transport unit 70 so as not to rotate. The transport unit 70 moves the container 13 in the transport direction MD with the bottom 16 of the container 13 exposed.

[0051] The imaging system 100 includes N imaging devices 11 (where N is a natural number of 2 or more) that image the article 12 being transported by the transport unit 70 at N locations in the direction MD of movement. In the example shown in Figure 9, N = 4, and the imaging system 100 includes 4 imaging devices 11. That is, as shown in Figure 9, the imaging system 100 includes, for example, 4 imaging devices 11A to 11D along the movement path in which the transport unit 70 transports the article 12.

[0052] More specifically, as shown in Figures 9 and 10, the imaging system 100 comprises a first imaging device 11A, a second imaging device 11B, a third imaging device 11C, and a fourth imaging device 11D. Each of the multiple imaging devices 11 comprises an illumination unit 20, a camera 30, and an optical path control member 40. Each optical path control member 40 in the multiple imaging devices 11 is positioned at a different orientation angle. In Figure 9, each optical path control member 40A to 40D is inclined in the direction indicated by the arrow inside. By making the inclination direction of each optical path control member 40A to 40D different, light is irradiated onto the bottom 16 of the article 12 from different directions.

[0053] More specifically, the first imaging device 11A comprises a first illumination unit 20A, a first camera 30A, and a first optical path control member 40A. The first optical path control member 40A is positioned at a first attitude angle. As shown in Figure 10, the first camera 30A captures an image of the article 12 when it is at a first imaging position SP1, including a gradient of light and dark caused by transmitted light L2 being irradiated from a direction corresponding to the first attitude angle.

[0054] The second imaging device 11B includes a second illumination unit 20B, a second camera 30B, and a second optical path control member 40B. The second optical path control member 40B is positioned at a second attitude angle. As shown in Figure 10, the second camera 30B images the article 12 when it is at the second imaging position SP2, thereby acquiring an image of the article 12 that includes a gradient of light and dark due to transmitted light L2 being irradiated from a direction corresponding to the second attitude angle.

[0055] The third imaging device 11C comprises a third illumination unit 20C, a third camera 30C, and a third optical path control member 40C. The third optical path control member 40C is positioned at a third attitude angle. As shown in Figure 10, the third camera 30C images the article 12 when it is at the third imaging position SP3, thereby acquiring an image of the article 12 that includes a gradient of light and dark due to transmitted light L2 being irradiated from a direction corresponding to the third attitude angle.

[0056] The fourth imaging device 11D comprises a fourth illumination unit 20D, a fourth camera 30D, and a fourth optical path control member 40D. The fourth optical path control member 40D is positioned at the fourth attitude angle. As shown in Figure 10, the fourth camera 30D images the article 12 when it is at the fourth imaging position SP4, thereby acquiring an image of the article 12 that includes a gradient of light and dark due to transmitted light L2 being irradiated from a direction corresponding to the fourth attitude angle.

[0057] In the N imaging devices 11A to 11D, the orientation of the transmitted light axis C2 of the optical path control members 40A to 40D is different for each. The N cameras 30A to 30D image the article 12 multiple times under multiple conditions in which the direction in which each transmitted light axis C2 of the light-transmitting section 42 in the optical path control members 40A to 40D is tilted with respect to the imaging light axis C1 is different for each other. Under the control of the imaging control unit 51 (see Figure 11), each of the cameras 30A to 30D shown in Figures 9 and 10 images the transmitted light L2 image of the article 12 once with the corresponding optical path control member 40A to 40D as the background.

[0058] In Figure 9, the transport unit 70 transports the article 12 without axial rotation. Cameras 30A to 30D capture images of the article 12 being transported by the transport unit 70 along the movement direction MD at their respective imaging positions SP1 to SP4. The directions of the transmitted light axes C2 of the four optical path control members 40A to 40D differ by 90 degrees in the plan view of Figure 9. Therefore, the bottom 16 of the container 13 is imaged with transmitted light illuminating it at an angle, each with a different direction of light direction.

[0059] By capturing multiple images with different directions of transmitted light, multiple types of images Img1 to Img4 are obtained, each with a different direction of shading from the unevenness of the emboss 19 (see Figure 7). Since multiple types of images Img1 to Img4 are acquired, the frequency of obtaining an image IS with appropriate shading from the uneven parts such as the emboss 19 increases. Therefore, it becomes easier to obtain an image IS in which the shading of the unevenness of the emboss 19 is clear. One may select the image IS in which the emboss 19 is clearest from the four types of image IS, or one may acquire a composite image by combining the four types of image IS into a single image. The transport unit 70 may also have a rotation mechanism that transports the article 12 in the movement direction MD while rotating it, as long as four types of image IS can be obtained. Alternatively, the transport unit 70 may be a rotary type that transports the article 12 while rotating it, with the mouth 18 of the article 12 being attracted or gripped. Even with this type of rotary type, it is sufficient that the camera 30 can image the bottom 16 through the mouth 18.

[0060] <Electrical Configuration of Article Inspection Device 10> Next, the electrical configuration of the article inspection device 10 will be described with reference to Figure 11. As shown in Figure 11, the article inspection device 10 comprises an imaging device 11 and an inspection processing unit 60. Note that the article inspection device 10 shown in Figure 11 shows one imaging device 11. In Figures 9 and 10, when there are N imaging devices 11 (where N is a natural number of 2 or more), although the direction of light irradiation to the object to be imaged (e.g., the bottom 16) of the article 12 via the optical path control member 40 in the N imaging devices 11 is different, the basic configuration of the imaging device 11 is the same. For this reason, only one imaging device 11 is shown in Figure 11, and the other N-1 imaging devices 11 are omitted.

[0061] As shown in Figure 11, the imaging device 11 includes an illumination unit 20, a camera 30, and an optical path control member 40. The imaging device 11 further includes a control unit 50 that controls the illumination unit 20 and the camera 30, etc. The control unit 50 includes an imaging control unit 51 and an image processing unit 53. The imaging control unit 51 includes a signal processing unit 52 that receives the imaging signal S1 from the camera 30.

[0062] The imaging device 11 may include a transport unit 70 that transports the article 12 (container 13) along a path passing through the imaging position SP. The transport unit 70 transports the container 13 in a manner that allows imaging of the bottom 16 of the container 13. The transport unit 70 can use any transport method as long as it can transport the container 13 in a manner that allows imaging of the bottom 16. The transport unit 70 may be, for example, a belt-type transport unit, a chuck-type transport unit, a suction-type transport unit, etc. The transport unit 70 may transport the container 13 while it is rotating, or it may transport it without rotating it.

[0063] The illumination unit 20 illuminates the article 12 at the imaging position SP. The illumination unit 20 has, for example, a plurality of light-emitting units 21. The light-emitting units 21 may be, for example, light-emitting LEDs. The illumination unit 20 may be configured to emit diffused light of white light or a specific color from the RGB three colors from a surface. The illumination unit 20 may illuminate the article 12 with visible light. The illumination unit 20 may be configured to change the intensity of the light according to the transparency and color of the article 12.

[0064] The imaging device 11 also includes a sensor 71 that detects an article 12 at the imaging position SP. When the sensor 71 detects an article 12 shortly before or when it reaches the imaging position SP, the illumination unit 20 illuminates the article 12 at the imaging position SP, and the camera 30 images the article 12 at the imaging position SP. The imaging control unit 51 controls the emission of light from the illumination unit 20 to irradiate the article 12 at the imaging position SP, and controls the imaging of the camera 30 to image the article 12, based on the detection signal from the sensor 71.

[0065] Article 12 is positioned between the camera 30 and the optical path control member 40 in a predetermined orientation with its bottom 16 facing the illumination unit 20 and its mouth 18 facing the camera 30. The camera 30 is positioned opposite the illumination unit 20 to the article 12 at the imaging position SP. The camera 30 includes a lens 31 and an image sensor 33 arranged inside the lens barrel 30a. The image Img focused by the lens 31 is formed on the image sensor 33. The camera 30 captures an image Img of light (for example, visible light) received by the image sensor 33. The image sensor 33 outputs an imaging signal S1 including the captured image. The light of the image captured by the camera 30 may include light other than visible light, such as near-infrared light. The camera 30 may also have an infrared cut filter between the lens 31 and the image sensor 33.

[0066] The optical path control member 40 is positioned between the illumination unit 20 and the article 12. The optical path control member 40 is sheet-shaped. The optical path control member 40 has light-shielding portions 41 and light-transmitting portions 42 arranged in a two-dimensional arrangement pattern on the sheet surface 40S shown in Figures 1 and 7. As shown in Figures 1 and 7, the optical path control member 40 is angle-adjusted to a predetermined orientation angle such that the transmitted light axis C2 of the light-transmitting portion 42 (see Figures 1 and 7) is tilted by a predetermined acute angle with respect to the imaging light axis C1, which is the optical axis of the camera 30. The direction along the transmitted light axis C2 is also the light-directing direction in which the light-transmitting portion 42 of the optical path control member 40 easily transmits light.

[0067] The imaging device 11 includes an adjustment unit 75 that adjusts the contrast of the image captured by the camera 30. The adjustment unit 75 performs at least one of the following adjustments: adjusting the attitude angle of the optical path control member 40, adjusting the position of the lens 31 of the camera 30, and adjusting the focal length of the camera 30. The imaging device 11 shown in Figure 11 includes an angle adjustment unit 80, a focus adjustment unit 35, and a lens position adjustment unit 36 ​​as the adjustment unit 75. The adjustment unit 75 may also be configured to move the position of the article 12. For example, the adjustment unit 75 may be configured to move the entire transport unit 70 or a part of the transport unit 70 capable of supporting the article 12 at the imaging position SP in a direction along the imaging optical axis C1. The adjustment unit 75 only needs to include at least the angle adjustment unit 80 among the angle adjustment unit 80, the focus adjustment unit 35, and the lens position adjustment unit 36.

[0068] The angle adjustment unit 80 adjusts the attitude angle of the optical path control member 40. The angle adjustment unit 80 includes an angle adjustment shaft 81 that can adjust the attitude angle of the optical path control member 40, and a rotation mechanism that rotates the angle adjustment shaft 81. The rotation mechanism may have an operating part that allows a person to manually rotate the angle adjustment shaft 81. In other words, the angle adjustment unit 80 may be manually operated. The rotation mechanism may also include a motor 82 for angle adjustment, which is a drive source. The attitude angle of the optical path control member 40 is adjusted by adjusting the amount of rotation of the angle adjustment shaft 81 using the power of the motor 82. The motor 82 may be driven by a person operating the operating part, by an amount corresponding to that operation, or it may be automatically driven and controlled by the control unit 50 based on information such as the product number of the item 12. In this way, the angle adjustment unit 80 adjusts the attitude angle of the optical path control member 40 so that the angle made by the transmitted light axis C2 of the light-transmitting part 42 with respect to the imaging light axis C1 of the camera 30, that is, the direction of light irradiation with respect to the bottom part 16, is a specific angle. In the case of an optical path control member 40 configured by stacking two optical path control sheets with their stripe directions perpendicular to each other (for example, Figures 3 and 6), the attitude angle of the optical path control member 40 is adjusted so that the transmitted optical axes C2 of the two types of translucent sections 42 that are perpendicular to each other are tilted at an acute angle with respect to the imaging optical axis C1. In this case, the angle adjustment unit 80 adjusts the optical path control member 40 to an attitude angle PA indicated by the arrow in the optical path control member 40 shown in the right-hand figure of Figure 6, for example.

[0069] Furthermore, the focus adjustment unit 35 is configured to allow adjustment of the focus of the camera 30. The focus adjustment unit 35 may be configured so that a person manually adjusts the focus of the camera 30, or it may be an autofocus adjustment unit (autofocus function unit) that can automatically adjust the focus of the camera 30. The focus adjustment unit 35 includes a mechanism to adjust the focal length by moving the lens 31 in the direction of the imaging optical axis C1. If the focus adjustment unit 35 is an autofocus adjustment unit, it detects the distance to the subject with a distance sensor and adjusts the focal length to focus on the subject by repeatedly moving the lens 31 with the power of a motor (not shown) according to the detected distance.

[0070] The lens position adjustment unit 36 ​​is a sliding mechanism that slides the camera 30 along the imaging optical axis C1. The lens position adjustment unit 36 ​​is a slider that supports the camera 30 and has a rail 37 that moves this slider along the imaging optical axis C1. The lens position adjustment unit 36 ​​adjusts the position of the lens 31 by sliding the slider along the rail 37, thereby moving the entire camera 30 along the imaging optical axis C1. The lens position adjustment unit 36 ​​adjusts the distance between the camera 30 (lens 31) and the object 12 which is the subject. The lens position adjustment unit 36 ​​may be a manual type in which a person manually moves the slider along the rail 37. Alternatively, the lens position adjustment unit 36 ​​may be an electric type having a motor (not shown) as the drive source for the slider. In this case, it may be a manual operation type in which the motor is driven by an amount corresponding to the amount of operation by the person operating the operation unit, or it may be an automatic adjustment type in which the control unit 50 drives and controls the motor based on information such as the product number of the object 12.

[0071] The imaging control unit 51 includes a signal processing unit 52 that receives the imaging signal S1 from the camera 30. The signal processing unit 52 performs signal processing on the imaging signal S1 received from the camera 30. When the camera 30 is a monochrome camera and the signal processing unit 52 receives a monochrome imaging signal S1, it performs normalization processing, brightness adjustment by nonlinear processing such as gamma correction, and edge enhancement processing on the monochrome imaging signal S1 as needed. The signal processing unit 52 converts the processed imaging signal S1 into an image signal S2 that includes a one-band monochrome image. The signal processing unit 52 outputs the image signal S2 to the image processing unit 53.

[0072] Furthermore, if the signal processing unit 52 is configured to receive an RGB color imaging signal S1 from the camera 30, which is a color camera, it performs normalization processing, color separation processing to separate the image signal S1 into individual bands R, G, and B, brightness adjustment by nonlinear processing such as gamma correction, and edge enhancement processing as needed. The signal processing unit 52 may also output an image signal S2 containing the RGB color image, R image, G image, and B image to the image processing unit 53.

[0073] The camera 30 may acquire one image in a single imaging session, or it may acquire multiple images in multiple imaging sessions. In this embodiment, one or more images are acquired for each item 12, depending on the number of cameras 30.

[0074] The imaging control unit 51 controls the illumination unit 20 and the camera 30. The imaging control unit 51 controls the illumination of the illumination unit 20 and the imaging of the camera 30 at a timing based on a detection signal from the sensor 71 that detects the article 12 just before it reaches the imaging position SP or when the article 12 has reached the imaging position SP. The imaging control unit 51 causes the illumination unit 20 to emit light to illuminate the article 12 at the imaging position SP. The imaging control unit 51 causes the camera 30 to take an image while the illumination unit 20 is illuminating the article 12. The imaging control unit 51 causes the camera 30 to take an image Img of the transmitted light that has passed through the transparent portion of the article 12.

[0075] In the imaging system 100 equipped with four imaging devices 11 shown in Figures 9 and 10, the bottom 16 of the article 12 is imaged by four cameras 30 under four different imaging conditions with different light illumination directions. Four images of the bottom 16 of the article 12 with different light illumination directions are acquired by each camera 30. The number of imaging devices 11 may be one, two, three, or five or more. The number of cameras 30 may be selected according to the type of image required. For example, if the control unit 50 stores the images in memory and uses them when needed for traceability or other purposes, one or two imaging devices 11 may be sufficient. Furthermore, when used for inspection, the accuracy of inspection may be improved by providing two, three, four or more imaging devices 11 to use multiple types of images with different light illumination directions. Alternatively, by rotating the article 12, multiple types of images with different light illumination directions may be acquired by one camera 30 through multiple imaging attempts.

[0076] The image processing unit 53 generates an captured image IS by applying predetermined image processing to the image signal S2. The image processing unit 53 may also perform a synthesis process to combine multiple types (for example, four types) of images with different light irradiation directions based on multiple image signals S2 into one image. In addition to the synthesis process, the image processing unit 53 may also perform a trimming process to cut out the item image area or the inspection target area from the image. The image processing unit 53 outputs the generated captured image IS to the inspection processing unit 60.

[0077] The inspection processing unit 60 inspects the recesses or protrusions of the article 12 based on images captured by one or more imaging devices 11. The recesses or protrusions of the article 12 to be inspected include embossing 19 and scratches on the container 13. The inspection processing unit 60 inspects the article 12 based on an image IS that shows a specific area including the recesses or protrusions of the article 12. The inspection processing unit 60 may use the traceability of the article 12 as the purpose of inspection, or it may inspect the article 12 for defects such as scratches, dirt, or improper engraving. For example, if the purpose is traceability, it is sufficient to obtain an image that can identify engraved characters or symbols such as embossing 19. On the other hand, when inspecting scratches, dirt, or improper engraving of the article 12 that require a certain level of inspection accuracy, the inspection processing unit 60 may employ a method of comprehensively evaluating the inspection results obtained by individually inspecting multiple types of images Img1 to Img4 (see Figure 10) captured with different light irradiation directions. Alternatively, the inspection processing unit 60 may employ a method to improve inspection accuracy by using a composite image obtained by combining images of multiple types of images Img1 to Img4 into a single image, to inspect the article 12 for scratches, dirt, marking defects, etc.

[0078] The inspection processing unit 60 outputs traceability images to the display unit 65 as inspection results, or outputs inspection images and information regarding the presence or absence of defects to the display unit 65. <Regarding the imaging limit resolution pitch> Next, with reference to Figures 12 and 13, the relationship between the pitch of the light-transmitting portion 42 constituting the optical path control member 40 and the pixel resolution of the camera 30 will be explained.

[0079] Figure 12 shows the captured image IS obtained when the camera 30 captures an imaging area including the embossed object 19, which is the actual object to be imaged. Figure 12 is a diagram in which multiple imaging pixels 33A arranged on the image sensor 33 are projected onto the captured image IS. In the example shown in Figure 12, the captured image IS projects a total of 99 imaging pixels 33A, 11 pixels in the horizontal direction and 9 pixels in the vertical direction. The pixel pitch of the imaging pixels 33A projected onto the captured image IS is 5 mm, as shown by the scale SL in Figure 12. The letters "A4" in the captured image IS are, for example, the embossed object 19. In Figure 12, the width of the letters made up of the embossed object 19 included in the captured image IS is 20 mm for "A" and 17 mm for "4", as shown by the scale SL.

[0080] When the position of the camera 30 is changed, the pixel pitch of the imaging pixels 33A projected onto the captured image IS, and the character width of the embossing 19, change according to the camera position. The actual pixel pitch of the imaging pixels 33A of the image sensor 33 is, for example, 3 to 5 μm.

[0081] The image sensor 33 captures the optical path control member 40, which is located further back from the camera 30 than the bottom 16 on which the embossing 19 is formed. In other words, the black and white striped pattern formed by the light-shielding portion 41 and the light-transmitting portion 42 of the optical path control member 40 is captured on the image sensor 33.

[0082] As shown in Figures 13(a) to (e), the alternating arrangement of light-shielding portions 41 and light-transmitting portions 42 creates a black and white striped pattern. Depending on the pitch of this black and white striped pattern and the size of the imaging pixels 33A, there are cases where the black and white striped pattern created by the light-shielding portions 41 and light-transmitting portions 42 is reflected in the image SI, and cases where the black and white striped pattern is reflected in the image SI at a level where it cannot be distinguished due to the resolution limits of the image sensor 33.

[0083] In Figures 13(a) and (b), the pitch of the light-transmitting portion 42 constituting the optical path control member 40 is greater than the pixel resolution of the camera 30, which is determined by the pitch (pixel pitch) of the imaging pixels 33A of the camera 30. Therefore, as shown in Figures 13(a) and (b), the optical path control member 40 is reflected on the image sensor 33 in a way that allows for the identification of black and white stripes. In this case, in the example shown in the right-hand figure of Figures 13(a) and (b), the light-shielding portion 41 appears as a dark area in the image SI. Therefore, for example, in the captured image IS shown in Figure 12, a part of the embossing 19 may be hidden by the dark area of ​​the light-shielding portion 41 and become invisible.

[0084] Figure 13(c) shows the case where the pitch of the light-transmitting portion 42 constituting the optical path control member 40 is the same as or slightly smaller than the pixel resolution of the camera 30. As a result, as shown in Figure 13(c), the optical path control member 40 is reflected on the image sensor 33 with a reduced contrast between the light and dark areas of the black and white stripes, and with a shorter stripe pitch. In the example shown in the right-hand figure of Figure 13(c), the dark areas of the light-shielding portion 41 and the bright areas of the light-transmitting portion 42 are difficult to distinguish in the image SI. As a result, as shown in Figure 12, an image IS is obtained at a level where the embossing 19 can be somewhat identified.

[0085] In Figures 13(d) and (e), the pitch of the light-transmitting portion 42 constituting the optical path control member 40 is smaller than the pixel resolution of the camera 30. Therefore, as shown in the right-hand figure of Figures 13(d) and (e), the optical path control member 40 appears in the image SI as a single shade of gray, indistinguishable from the black and white striped pattern. In reality, however, the distance from the camera 30 to the emboss 19 is different from the distance from the camera 30 to the optical path control member 40, so the black and white pattern is blurred to some extent.

[0086] In this embodiment, as shown in Figures 13(c) to (e), the pitch of the light-transmitting portion 42 constituting the optical path control member 40 is set to be less than or equal to the pixel resolution of the camera 30. As a result, an image IS is obtained that allows the entire embossing 19 shown in Figure 12 to be identified.

[0087] For example, in the example shown in Figure 13(a), the pitch of the light-transmitting portion 42 of the optical path control member 40 is equal to four times the pitch of the imaging pixel 33A. Also, in the example shown in Figure 13(b), the pitch of the light-transmitting portion 42 of the optical path control member 40 is equal to twice the pitch of the imaging pixel 33A. If the pitch of the light-transmitting portion 42 of the optical path control member 40 becomes smaller than in the state shown in Figure 13(b), the image SI will no longer be able to distinguish between the light-shielding portion 41 and the light-transmitting portion 42. The pitch of the light-transmitting portion 42 at this point is called the imaging limit resolution pitch IP. The imaging limit resolution pitch IP is expressed as IP = 2 × PP, using the pitch PP of the imaging pixel 33A. Note that below the imaging limit resolution pitch, the image SI will no longer be able to distinguish between the light-shielding portion 41 and the light-transmitting portion 42. Generally, the limit at which the light-shielding portion 41 and the light-transmitting portion 42 can no longer be distinguished is called the Nyquist limit. The period (pitch) at that time, i.e., the Nyquist frequency Fn, is given by Fn = 1 / IP. The image pixel pitch is determined by the pitch of the image pixels 33A of the image sensor 33 and the image area size. The image area size is the size of the image area including the emboss 19. The image area size is determined by the lens focal length and the distance between the camera and the subject.

[0088] <About the imaging method> The imaging method for imaging an article 12 having at least a part of a transparent or semi-transparent portion through which light can pass is included in the following (A) to (D). (A) Illuminating the article 12 placed at imaging position SP with the illumination unit 20. (B) With an optical path control member 40 having a light-shielding portion 41 and a light-transmitting portion 42 arranged in two dimensions, placed between the illumination unit 20 and the article 12, the camera 30, positioned on the opposite side of the illumination unit 20 from the article 12, captures an image Img of the transmitted light that has passed through the article 12 and the light-transmitting portion 42, thereby acquiring an image IS. (C) The pitch of the light-transmitting portion 42 is less than or equal to the pixel resolution of the camera 30. (D) The transmitted light axis C2, which is the optical axis of the transmitted light that passes through the light-transmitting portion 42 and is restricted to a predetermined field of view by the light-shielding portion 41, is inclined with respect to the imaging optical axis C1 of the camera 30.

[0089] <Operation of the First Embodiment> Next, the operation of the imaging device 11 and the article inspection device 10 will be described. As shown in Figure 9, the transport unit 70 transports the transparent article 12, which is the subject, along the movement direction MD. The control unit 50 controls the illumination units 20A to 20D and the cameras 30A to 30D based on the detection signal from the sensor 71, thereby sequentially imaging the article 12 at four imaging positions SP1 to SP4. The imaging control unit 51 controls the illumination unit 20, so that the article 12 is illuminated with, for example, white light from the illumination unit 20. The camera 30 captures an image Img of the transmitted light that has passed through the light-transmitting portion 42 of the optical path control member 40 and the article 12.

[0090] Four cameras 30A to 30D capture images of the article 12 four times via optical path control members 40 with different orientation angles, thereby capturing four types of transmitted images Img1 to Img4 of the article 12 with different light irradiation directions. The captured images IS acquired by each camera 30A to 30D capturing the article 12 are sent to the inspection processing unit 60. The inspection processing unit 60 stores the captured images IS received from the image processing unit 53 in memory along with traceability information, and performs inspection processing based on the captured images IS to check for defects in the engraving of characters and symbols formed by the embossing 19, as well as for scratches and other irregularities.

[0091] Here, the captured image IS of the embodiment captured by camera 30 will be explained in comparison with the comparative example. Figure 14 is the captured image IS0 captured by the imaging device of the first comparative example, which does not have an optical path control member 40. Figure 15 is the captured image IS1 captured by the imaging device of the second comparative example, which has an optical path control member 40, but the imaging optical axis C1 and the transmitted optical axis C2 are parallel and the optical path control member 40 is not in an inclined position. Figures 16 to 19 are the captured images IS2 to IS5 captured by the imaging device 11 of the embodiment. In the imaging device 11 of each embodiment, the attitude angle of the optical path control member 40 is adjusted to different inclination angles by the angle adjustment unit 80. From Figure 16 to Figure 19, the attitude angle of the optical path control member 40 when capturing the captured image IS is adjusted in stages and becomes larger.

[0092] Figure 14 shows the image IS0 captured by the imaging device of the first comparative example, which does not have the optical path control member 40. In the image IS0, characters formed by embossing 19 and other irregularities cannot be identified.

[0093] Figure 15 shows the image IS1 captured by the imaging device of the second comparative example, in which the optical path control member 40 is positioned without tilting. In the image IS1, although the characters formed by the unevenness of the embossing 19 can be faintly identified, the shadows of the unevenness of the embossing 19 are small and the characters are not clear.

[0094] Figure 16 shows the captured image IS2 taken by the imaging device 11, where the tilt angle of the orientation angle of the optical path control member 40 is small. In the captured image IS2, although the characters formed by the unevenness of the embossing 19 can be identified, the characters of the embossing 19 are not very clear because the shading of the unevenness of the embossing 19 is small.

[0095] Figure 17 shows an image IS3 captured by an imaging device 11 in which the tilt angle of the orientation angle of the optical path control member 40 is appropriate. In the image IS3, the shading of the characters formed by the unevenness of the embossing 19 is appropriate, so the characters of the embossing 19 are clear.

[0096] Figure 18 shows the image IS4 captured by the imaging device 11, where the tilt angle of the optical path control member 40 is large. In the image IS4, the shading of the characters formed by the unevenness of the embossing 19 is slightly darker. Because the shading is a little darker, the characters of the embossing 19 appear darker.

[0097] Figure 19 shows an image IS5 captured by an imaging device 11 where the tilt angle of the optical path control member 40's attitude angle is excessively large. In the image IS5, the shading of the characters formed by the unevenness of the embossing 19 tends to be too dark. Although this is within an acceptable range for inspection, depending on the location of the embossing 19, excessive shading may make it difficult to identify the characters on the embossing 19. Furthermore, if the shading of other uneven parts besides the embossing 19 is large, the shading of those other uneven parts may overlap with the shading of the embossing 19, making it easier to identify the characters. For this reason, the tilt angle of the optical path control member 40's attitude angle may be set to an angle that makes it easy to identify the characters on the embossing 19, taking into consideration the degree of unevenness of the embossing 19 and the influence of shading from other uneven parts besides the embossing 19.

[0098] <Effects of the First Embodiment> According to the first embodiment described in detail above, the following effects can be obtained. (1-1) The imaging device 11 images an article 12 having at least a part of a transparent or semi-transparent portion that light can pass through. The imaging device 11 comprises an illumination unit 20, a camera 30, an optical path control member 40, and a control unit 50. The illumination unit 20 illuminates the article 12 placed at the imaging position SP. The camera 30 is positioned on the opposite side of the article 12 from the illumination unit 20. The optical path control member 40 is sheet-shaped and is placed between the illumination unit 20 and the article 12, and has light-shielding portions 41 and light-transmitting portions 42 arranged in a two-dimensional arrangement pattern on the sheet surface 40S. The control unit 50 causes the camera 30 to image the transmitted light that has passed through the article 12 and the light-transmitting portions 42 to acquire an image. The pitch of the light-transmitting portions 42 is less than or equal to the pixel resolution of the camera 30. The transmitted light axis C2, which is the optical axis of the transmitted light that passes through the light-transmitting portion 42 and is restricted to a predetermined field of view by the light-shielding portion 41, is inclined at an acute angle with respect to the imaging optical axis C1 of the camera 30. Therefore, an image can be captured that makes it easy to identify recesses or protrusions such as embossing 19 or scratches on the article 12.

[0099] (1-2) The optical path control member 40 has one or more sheet-like members 46 and a light-transmitting portion 42 formed on the sheet-like members 46 and extending in the thickness direction of the sheet-like members 46. The optical path control member 40 is arranged in a position inclined with respect to the imaging optical axis C1. With this configuration, since the optical path control member 40 is arranged in a position inclined with respect to the imaging optical axis C1, it is possible to capture an image of the embossing 19 or recesses or protrusions such as scratches on the article 12 with shading that makes them easy to identify.

[0100] (1-3) The imaging device 11 further includes an adjustment unit 75 for adjusting the contrast of the image. The adjustment unit 75 is configured to adjust at least one of the following: the attitude angle of the optical path control member 40, the lens position of the camera 30, and the focal length of the camera 30. This configuration makes it possible to increase the contrast of the image.

[0101] (1-4) The camera 30 images the article 12 multiple times under multiple conditions in which the transmitted light axis C2 of the light-transmitting portion 42 of the optical path control member 40 is tilted in a different direction with respect to the imaging light axis C1. With this configuration, multiple types of images with shading of recesses or protrusions such as embossing 19 or scratches can be obtained with different light irradiation directions. Multiple types of images with different locations where shading occurs for embossing 19 or scratches can improve the accuracy of identifying recesses or protrusions such as embossing 19 or scratches.

[0102] (1-5) Article 12 is a container 13 having an opening 18 and a bottom 16 which is a transparent or translucent portion. The container 13 is positioned at the imaging position SP with the opening 18 facing the camera 30 and the bottom 16 facing the illumination unit 20. The camera 30 images the inner bottom surface of the bottom 16 through the opening 18. With this configuration, since the camera 30 images the inner bottom surface of the bottom 16 through the opening 18, the bottom 16 can be imaged without separating the optical path control member 40 and the bottom 16 too far. For example, recesses or protrusions such as embossing 19 or scratches formed on the bottom 16 can be obtained as a shaded and easily identifiable image.

[0103] (1-6) The article inspection device 10 comprises an imaging device 11 and an inspection processing unit 60 that inspects recesses or protrusions of the article 12 based on the image captured by the imaging device 11. With this configuration, recesses or protrusions such as embossing 19 or scratches formed on the article 12 can be inspected.

[0104] (1-7) The imaging method involves imaging an article 12 having at least a portion of a transparent or semi-transparent portion through which light can pass. The imaging method includes the following (A) to (D): (A) Illuminating the article 12 placed at imaging position SP with the illumination unit 20. (B) With an optical path control member 40 having a light-shielding portion 41 and a light-transmitting portion 42 arranged in two dimensions, positioned between the illumination unit 20 and the article 12, a camera 30 positioned on the opposite side of the illumination unit 20 from the article 12 captures an image of the transmitted light that has passed through the article 12 and the light-transmitting portion 42 to acquire an image IS. (C) The pitch of the light-transmitting portion 42 is less than or equal to the pixel resolution of the camera 30. (D) The transmitted light axis C2, which is the optical axis of the transmitted light that passes through the light-transmitting portion 42 and is restricted to a predetermined field of view by the light-shielding portion 41, is inclined at an acute angle with respect to the imaging optical axis C1 of the camera 30. This method makes it possible to capture images that clearly identify embossing 19 or recessed or raised areas such as scratches on the article 12.

[0105] (Second Embodiment) Next, a second embodiment will be described with reference to Figures 20 to 22. In the second embodiment, the configuration of the optical path control member 40 differs from that of the first embodiment. The configuration other than the optical path control member 40 is the same as in the first embodiment.

[0106] The optical path control member 40 has one or more sheet-like members 46 and a light-shielding portion 41 and a light-transmitting portion 42 formed on the sheet-like members 46. In this embodiment, the optical path control member 40 has one or more types of light-transmitting portions 42 that extend in an oblique direction such that the transmitted optical axis C2 is inclined at an acute angle with respect to the sheet thickness direction. The type of the one or more types of light-transmitting portions 42 is the type of angle of the transmitted optical axis C2, which is inclined at an acute angle with respect to the sheet thickness direction, with respect to the sheet surface 40S. Figure 20 is an example of one type of light-transmitting portion 42 having a transmitted optical axis C2 that is inclined at an acute angle with respect to the sheet thickness direction. Figure 21 is an example of having two types of light-transmitting portions 42, each having two types of transmitted optical axes C2 and C3 as transmitted optical axes that are inclined at an acute angle with respect to the sheet thickness direction.

[0107] The one or more light-transmitting sections 42 shown in Figures 20 and 21 are formed such that one or more transmitted light axes C2 (or C2, C3) are inclined at an acute angle with respect to the sheet surface 40S. Therefore, the optical path control member 40 is positioned so that its sheet thickness direction is parallel to the imaging optical axis C1. The optical path control member 40 has one or more light-transmitting sections 42 having one or more transmitted light axes C2 formed on different sheet-like members 46 for each type. The optical path control member 40 shown in Figure 20 is composed of a single-layer optical path control member 47 made up of a single sheet-like member 46 on which one type of light-transmitting section 42 having a transmitted light axis C2 is formed.

[0108] The optical path control sheets constituting the optical path control members 47 and 48 may include a louver layer having a louver structure and a transparent high-performance resin layer sandwiching the louver layer. The louver layer has a plurality of louvers composed of light-shielding portions 41. The louvers define the direction of the transmitted optical axis C2 of the light-transmitting portion 42 and the viewing angle. In this embodiment, a louver angle, which is a predetermined acute angle with respect to the sheet thickness direction, is set in the light-shielding portion 41 (louver). Therefore, the transmitted optical axis C2 is inclined at an acute angle with respect to the sheet thickness direction. In addition, the viewing angle is narrowed to a predetermined angle by the louvers. The viewing angle is a value within the same angular range as the viewing angle of the optical path control sheet constituting the optical path control member 40 in the first embodiment. The viewing angle is, for example, a value within the range of 10 degrees to 140 degrees. Preferably, it is a value within the range of 20 degrees to 130 degrees. More preferably, it is a value within the range of 30 degrees to 120 degrees. However, viewing angles outside the above range may also be adopted. For example, a field of view of 5 degrees or 150 degrees would be acceptable.

[0109] In the other (second layer) optical path control sheet constituting the optical path control member 48 shown in Figure 21, the louvers also define the direction of the transmitted optical axis C3 of the light-transmitting portion 42 and the viewing angle. The louver angle causes the transmitted optical axis C3 to be inclined at an acute angle with respect to the sheet thickness direction. Furthermore, the viewing angle is narrowed to a predetermined angle similar to that of the first embodiment. The viewing angle is, for example, a value within the range of 3 degrees to 60 degrees. Preferably, it is a predetermined value within the range of 6 degrees to 45 degrees. More preferably, it is a predetermined value within the range of 10 degrees to 35 degrees.

[0110] Furthermore, the two types of transmitted light axes C2 and C3 have different directions. In the example shown in Figures 21 and 22, the two types of transmitted light axes C2 and C3 are inclined at a predetermined acute angle with respect to the sheet thickness direction, but the direction of inclination differs by a predetermined angle (for example, 90 degrees) in the plan view shown in Figure 22. As long as the directions of inclination are different, the angles at which the two types of transmitted light axes C2 and C3 are inclined at an acute angle with respect to the sheet thickness direction may be the same or different.

[0111] The difference in the direction (orientation) of the inclination of multiple types (e.g., two types) of transmitted optical axes C2 and C3 relative to the imaging optical axis C1 is indicated by the angle formed by the line segments projected onto a virtual plane perpendicular to the imaging optical axis C1, for example. The angle formed by the line segments projected onto the virtual plane of the transmitted optical axes C2 and C3 is not limited to the maximum value of 90 degrees, but may be an angle less than 90 degrees. In this case, the angle range is preferably, for example, 20 degrees or more and 90 degrees or less. Preferably, it is between 45 degrees and 90 degrees. An angle less than 20 degrees is also acceptable.

[0112] Examples of optical path control sheets include the "Shin-Etsu VCF" product, a field of view / optical path control film manufactured by Shin-Etsu Polymer Co., Ltd., specifically the version with an angled louver. The angled louver version features an angled shading layer (shading portion 41) that shifts the viewing angle away from the front. "Shin-Etsu VCF" is available in several field of view angles for use as an optical path control sheet: a standard type with a 60-degree field of view, narrow field of view types with 30 and 20 degrees, and a wide field of view type with a 120-degree field of view. The field of view can also be any predetermined angle within the range of 10 degrees to 140 degrees. Optical path control sheets with structures other than the louver structure may also be used.

[0113] Since the transmitted light axis C2 of the light-transmitting section 42 is inclined at an acute angle with respect to the sheet thickness direction, the single-layer optical path control member 47 is positioned parallel to the bottom 16 of the container 13 at the imaging position SP. Even when the optical path control member 47 is positioned parallel to the bottom 16 of the container 13, the transmitted light axis C2 of the light-transmitting section 42 is at an acute angle with respect to the imaging optical axis C1. The optical path control member 47 shown in Figure 20 is positioned such that the transmitted light axis C2 of one or more light-transmitting sections 42 is inclined at an acute angle with respect to the imaging optical axis C1.

[0114] In the first embodiment, in order to set the transmitted optical axis C2 at an acute angle with respect to the imaging optical axis C1, it was necessary to position the optical path control member 40 at an orientation angle that was tilted at an acute angle with respect to the imaging optical axis C1. In contrast, the optical path control member 47 shown in Figure 20 can be positioned so that the sheet surface 40S is perpendicular to the imaging optical axis C1 of the camera 30. That is, the optical path control member 47 can be positioned so that the bottom 16 of the container 13 and the sheet surface 40S are parallel. As a result, it becomes possible to position the bottom 16 of the article 12 and the illumination unit 20 closer together, making it easier to secure a large amount of light to illuminate the bottom 16. In addition, since it is not necessary to tilt the sheet surface 40S, the installation area and installation space size of the imaging device 11, especially the optical path control member 40, can be reduced. Furthermore, it becomes unnecessary to make fine angle adjustments to the sheet surface 40S. Furthermore, similar to the configuration of the first embodiment, the imaging optical axis C1 and the transmitted optical axis C2 intersect at an acute angle, so a light and dark gradient is similarly formed in the image IS captured by the camera 30. This light and dark gradient allows shading to be formed on the emboss 19.

[0115] The optical path control member 40 shown in Figure 21 is a two-layer optical path control member 48 formed by stacking two single-layer optical path control members 47 shown in Figure 20, with the stripe directions (louver directions) formed by the light-shielding portion 41 and the light-transmitting portion 42 oriented at 90-degree different angles from each other. The optical path control member 48 is provided with two or more types of light-transmitting portions 48 that extend in an oblique direction, with the transmitted optical axes C2 and C3 of each sheet inclined at an acute angle with respect to the sheet thickness direction. The light-transmitting portions 42 formed on each of the two sheet-like members 46A and 46B are provided with two or more types, with their respective transmitted optical axes C2 and C3 forming an acute angle with respect to the imaging optical axis C1. The direction in which each of the two or more transmitted optical axes C2 and C3 inclinates with respect to the imaging optical axis C1 is different. Alternatively, the optical path control member 40 shown in Figure 21 may be replaced with a two-layer optical path control member 48, and a single-layer structure may be used in which two types of light-transmitting sections 42 with different angles of transmitted optical axes C2 and C3 are formed on a single sheet-like member 46.

[0116] As shown in Figures 21 and 22, the two-layer optical path control member 48 has two or more types of light-transmitting sections 42, each with transmitted light axes C2 and C3 that are inclined at an acute angle with respect to the imaging light axis C1. As shown in Figure 22, the two or more types of transmitted light axes C2 and C3 are inclined in different directions with respect to the imaging light axis C1.

[0117] Furthermore, the two-layer optical path control member 48 shown in Figure 21 is positioned so that its sheet surface 40S is parallel to the bottom 16 of the container 13. This allows for a closer positioning of the bottom 16 of the article 12 and the illumination unit 20, making it easier to secure a larger amount of light to illuminate the bottom 16. In addition, the installation area and space size of the imaging device 11, particularly the optical path control member 40, can be reduced. Moreover, fine angle adjustments of the sheet surface 40S become unnecessary.

[0118] <Regarding the total light transmittance and field of view of the optical path control member> Figure 23 shows the total light transmittance of the optical path control member 40. Figure 24 shows the field of view of the optical path control member 40 in the imaging device 11.

[0119] First, with reference to Figure 23, the total light transmittance (hereinafter simply referred to as "transmittance") of the optical path control member 40 will be explained. In the graph shown in Figure 23, the horizontal axis is angle and the vertical axis is transmittance. The angle on the horizontal axis is defined as 0 degrees when the optical path control sheet is viewed from directly in front, that is, from a direction perpendicular to the sheet surface 40S. With 0 degrees as the center, angles viewed from the right at an angle are considered positive (+) and angles viewed from the left at an angle are considered negative (-). The distribution line T0 in the graph corresponds to the viewing angle when the optical path control sheet of the first embodiment is not tilted. If the transmitted light axis at this time is C0, then C0 = 0 degrees. On the other hand, the distribution lines T1 and T2 correspond to the optical path control sheet of the second embodiment.

[0120] The transmitted light is directed towards the angle near the peak of transmittance in each distribution line T0, T1, and T2. Distribution line T0 has a peak in transmittance at an angle of 0 degrees (C0 = 0 degrees) when the optical path control sheet is viewed from directly in front (perpendicular) to the sheet surface 40S. The field of view is approximately 70 degrees. The field of view is the range of angles in which the light transmittance is greater than 0. Note that a field of view of approximately 70 degrees is just one example.

[0121] The distribution line T1 has a peak at an angle tilted from 0 degrees when viewed directly in front, that is, at an angle viewed from the direction along the transmitted light axis C2 (for example, C2 = 15 degrees). In this example, the peak of transmittance is at an angle of the transmitted light axis C2 tilted 15 degrees to the right of 0 degrees. In other words, the transmitted light is directed at an angle tilted 15 degrees to the right of 0 degrees. The field of view is approximately 70 degrees in this example.

[0122] The distribution line T2 has a peak at an angle tilted from 0 degrees, that is, at an angle viewed from the direction along the transmitted light axis C2 (for example, C2 = 30 degrees). In this example, the transmittance peak is at an angle of the transmitted light axis C2 tilted 30 degrees to the right of 0 degrees. In other words, the transmitted light is directed at an angle tilted 30 degrees to the right of 0 degrees. The field of view is approximately 70 degrees in this example.

[0123] A 0-degree angle when viewed from the front means that, in the imaging device 11, the light in the direction of the transmitted light is incident at a right angle to the imaging target surface (for example, the bottom 16) of the inspection target which is perpendicular to the optical axis C1 of the camera 30. This means that the angle with respect to the optical axis C1 (hereinafter also referred to as the "direction angle") is 0 degrees. In other words, the direction angle is 0 degrees.

[0124] For distribution line T0, the directionality angle of transmitted light is 0 degrees, so it is necessary to tilt the optical path control sheet to form shadows on uneven surfaces such as the embossing 19. On the other hand, for distribution lines T1 and T2, the directionality angles of transmitted light are, for example, 15 degrees and 30 degrees, respectively, so it is not necessary to tilt the optical path control sheet to form shadows on uneven surfaces such as the embossing 19, or it is sufficient to adjust only the difference in angle until the target directionality angle is reached.

[0125] In the graph in Figure 23, an angle of 0 degrees represents the angle at which light is shone straight and perpendicular to the surface being inspected, without any tilt. With 0 degrees as the reference point, positive angles indicate angles of light tilted to the right, while negative angles indicate angles of light tilted to the left. In order to form shadows on uneven surfaces such as the embossed surface 19, there needs to be a difference in the amount of light between the light tilted to the right and the light tilted to the left. Here, assuming the light source is common and the light irradiation conditions are the same, the area of ​​each distribution line T0 to T2 in the graph correlates with the amount of light.

[0126] The distribution line T0 shows that the amount of light tilted to the right and the amount of light tilted to the left are almost the same. Therefore, in this orientation, it is not possible to form shadows on uneven surfaces such as the embossed surface 19. In order to form shadows on uneven surfaces such as the embossed surface 19, it is necessary to tilt the optical path control sheet to adjust the transmitted optical axis C0 to the desired directional angle.

[0127] On the other hand, the distribution lines T1 and T2 show a large difference in light intensity between light tilted to the right and light tilted to the left. Therefore, even in a non-tilted position, shadows can be formed on uneven surfaces such as the embossed surface 19.

[0128] That is, the area occupied by the positive angle relative to 0 degrees is called the first area Sa1, and the area occupied by the negative angle relative to 0 degrees is called the second area Sa2. In order to form shading on the uneven surface, it is desirable that |Sa1 - Sa2| > 0. Here, if the smaller of the two areas Sa1 and Sa2 is s1 and the larger of the two is s2, then the ratio R1 of the two areas Sa1 and Sa2 is given by R1 = s1 / s2. If R1 < 1, it is easier to form shading on the uneven surface. The ratio R1 is preferably 0 or more and less than 0.8. Preferably, the ratio R1 is 0 or more and less than 0.7. More preferably, the ratio R1 is 0 or more and less than 0.6.

[0129] Next, the characteristics related to the field of view will be explained with reference to Figure 24. Figure 24 shows the field of view of the optical path control sheet corresponding to the distribution line T0 in Figure 23, and the field of view of the optical path control sheet corresponding to the distribution lines T1 and T2 in Figure 23, which have a transmitted light axis C2 tilted with respect to 0 degrees. The former is the field of view θ1 of the transmitted light LV1 shown by the dashed line in Figure 24, and the latter is the field of view θ2 of the transmitted light LV2 shown by the solid line in Figure 24. In Figure 24, the field of view θ1 and θ2 are shown at the position where the optical path control sheet constituting the optical path control member 40 intersects with the imaging optical axis C1. Therefore, the axis at an angle of 0 degrees shown by the dashed line in Figure 24 is parallel to the imaging optical axis C1.

[0130] The field angles θ1 and θ2 are shown as the same value, for example. The center line of the transmitted light LV1 is at an angle of 0 degrees. Therefore, the left angle α1 and the right angle β1, which divide the field angle θ1 of the transmitted light LV1 with respect to the 0-degree axis, are of equal magnitude.

[0131] On the other hand, the transmitted light LV2 has its center line as the transmitted light axis C2. Therefore, the field of view angle θ2 of the transmitted light LV2 is divided into two angles: α2 on the left and β2 on the right with respect to the 0-degree axis. The left angle α2 is larger than the right angle β2. Figure 24 shows an example where the transmitted light axis C2 is tilted to the left of the 0-degree axis, but if it is tilted to the right, the left angle α2 becomes smaller than the right angle β2.

[0132] Here, if we let γ1 be the smaller of the two angles α2 and β2, and γ2 be the larger of the two angles α2 and β2, then the ratio R2 of the two angles α2 and β2 is given by R2 = γ1 / γ2. When α2 ≠ β2, that is, when R2 < 1, shadows are easily formed on uneven surfaces. Furthermore, the smaller the value of the ratio R2, the easier it is for shadows to be formed on uneven surfaces. For this reason, the ratio R2 should be between 0 and 0.8. Preferably, the ratio R2 should be between 0 and 0.7. More preferably, the ratio R2 should be between 0 and 0.6.

[0133] Furthermore, when the optical path control sheet is tilted in the optical path control member 40 (43, 44, 45) of the first embodiment from the field of view angle θ1 of the transmitted light LV1 in Figure 24, depending on the tilt angle, the imaging optical axis C1 of the camera 30 may deviate from the field of view angle θ2. In the example shown in Figure 24, when the tilt angle of the optical path control sheet is, for example, θ1 / 2, the imaging optical axis C1 is exactly outside the field of view angle θ1. At this time, light from the region to the left of the imaging optical axis C1 of the optical path control sheet is less likely to illuminate the right half of the bottom 16 and is less likely to enter the camera 30. Within the region to the left of the optical path control sheet, the further to the left the position, the further to the left the limit position of light that can illuminate the bottom 16 and enter the camera 30 shifts to the left. On the other hand, light from the region to the right of the imaging optical axis C1 of the optical path control sheet is entered into the camera 30 while illuminating the right half of the bottom 16. For this reason, the imaging device 11 can image the entire bottom 16. Furthermore, even within the region to the right of the imaging optical axis C1 of the optical path control sheet, the further to the left the position, the further to the left the limit position of light that can illuminate the bottom 16 while entering the camera 30 shifts to the left. For this reason, in the first embodiment in which the optical path control member 40 is tilted, a brightness gradient (see Figures 4 to 6) occurs due to the tilted orientation of the optical path control member 40.

[0134] The dark areas in this brightness gradient reduce the visibility of the bottom 16 in the captured image IS. Therefore, from the viewpoint of brightness gradient, the attitude angle PA, which is the inclination angle of the optical path control member 40 in the first embodiment, should be an acute angle and within the range defined by the following field of view angle θ1. That is, the attitude angle PA should be less than or equal to the field of view angle θ1. Preferably, the attitude angle PA should be less than or equal to 3 / 4 (3θ1 / 4) of the field of view angle θ1. More preferably, the attitude angle PA should be less than or equal to 1 / 2 (=θ1 / 2) of the field of view angle θ1. Note that the attitude angle PA of the optical path control member 40 may be an angle outside the above range.

[0135] According to this second embodiment, the following effects can be obtained. (2-1) The optical path control member 40 has one or more sheet-like members 46 and one or more light-transmitting parts 42 formed on the sheet-like members 46, which extend in an oblique direction such that the transmitted light axis C2 is inclined at an acute angle with respect to the thickness direction of the sheet-like members 46. The optical path control member 40 is arranged such that the transmitted light axis C2 of the one or more light-transmitting parts 42 is inclined with respect to the imaging light axis C1. With this configuration, the angle at which the optical path control member 40 is inclined with respect to the imaging light axis C1 can be reduced. As a result, it becomes possible to arrange the bottom 16 of the article 12 and the illumination unit 20 closer together, making it easier to secure a large amount of light to illuminate the bottom 16. Therefore, it is possible to capture an image IS that makes it easy to identify recesses or protrusions such as embossing 19 or scratches on the article 12.

[0136] (2-2) Two or more types of light-transmitting sections 42 are provided, each extending in an oblique direction with the transmitted light axes C2 and C3 inclined at two or more different angles relative to the thickness direction of the sheet-like members 46A and 46B. The optical path control member 48 is arranged such that the transmitted light axes C2 and C3 of the two or more types of light-transmitting sections 42 are inclined with respect to the imaging optical axis C1. With this configuration, since there are two or more types of light-transmitting sections 42 with the transmitted light axis C2 extending at two or more different angles inclined with respect to the thickness direction of the sheet-like members 46A and 46B, the angle at which the optical path control member 48 is inclined with respect to the imaging optical axis C1 can be reduced. As a result, it becomes possible to arrange the bottom 16 of the article 12 and the illumination section 20 closer together, making it easier to secure a large amount of light to illuminate the bottom 16. Therefore, it is possible to capture an image IS that makes it easy to identify recesses or protrusions such as embossing 19 or scratches on the article 12. Furthermore, since adjusting the angles of the respective transmitted light axes C2 and C3 of the two types of light-transmitting sections 42 does not depend solely on adjusting the orientation of the optical path control member 48, it is easy to set the respective transmitted light axes C2 and C3 of the two types of light-transmitting sections 42 to an appropriate angle with respect to the imaging optical axis C1.

[0137] <Example of Modification> The embodiment is not limited to the above and may be modified in the following ways: The optical path control member 40 may be attached to the surface of the light-emitting surface of the illumination unit 20. The light-emitting surface of the illumination unit 20 is positioned at an orientation angle that makes a predetermined acute angle with respect to the imaging optical axis C1 of the camera 30. In other words, the illumination unit 20 is positioned at an orientation angle in which the normal direction of the light-emitting surface of the illumination unit 20 is inclined at an acute angle with respect to the imaging optical axis C1. The optical path control member 40 attached to the light-emitting surface of the illumination unit 20 is positioned at an orientation angle in which the transmitted optical axis C2 is inclined at an acute angle with respect to the imaging optical axis C1.

[0138] In the first and second embodiments, when multiple optical path control sheets are stacked, the number of sheets to be stacked is not limited to two, but may be three or four. Each sheet-like member 46 is configured such that the transmitted optical axis C2 of the light-transmitting portion 42 and the imaging optical axis C1 form different acute angles.

[0139] The shape of the light-shielding portion 41 and the shape of the light-transmitting portion 42 may be different. Also, the shapes of the light-shielding portion 41 and the light-transmitting portion 42 are not limited to stripes. The shapes of the light-shielding portion 41 and the light-transmitting portion 42 may be oval or elliptical, or they may be polygons such as triangles, rhombuses, pentagons, or hexagons.

[0140] - An electronically controlled optical path control sheet (for example, a dimming sheet) may be used as the optical path control member 40. The electronically controlled optical path control sheet may be a liquid crystal type in which the light-transmitting portion of the light-shielding portion and light-transmitting portion can be electrically switched. The liquid crystal type optical path control sheet may include, for example, a pair of alignment films sandwiching a liquid crystal layer, a pair of transparent electrodes (pixel electrodes), and a pair of polarizing filters. For example, the control unit 50 controls the optical path control sheet electrically by turning the applied voltage on / off or adjusting the voltage, thereby adjusting the formation / non-formation of at least the light-transmitting portion 42 and the transmitted light axis C2. For example, the control unit 50 may switch the angle of the transmitted light axis C2 of the light-transmitting portion 42 according to the type of article 12 or the degree of unevenness of the characters or symbols formed by the embossing 19.

[0141] - The direction in which the transmitted light axis C2 of the light-transmitting section 42 is inclined at an acute angle with respect to the imaging optical axis C1 of the camera 30 may be either clockwise in Figure 1 (counterclockwise in Figures 7 and 8) or counterclockwise (clockwise in Figures 7 and 8). In either direction, it is sufficient that the transmitted light axis C2 is inclined at an acute angle with respect to the imaging optical axis C1. Also, in the second embodiment, the direction in which the transmitted light axis C2 of the light-transmitting section 42 is inclined at an acute angle with respect to the imaging optical axis C1 of the camera 30 may be either counterclockwise or clockwise in Figures 20 and 21.

[0142] - The object to be imaged on the container 13 may be a part other than the bottom 16. For example, the body 15, shoulder 17, mouth 18, or neck of the container 13 may be the object to be imaged. In this case, if the camera 30 is configured to image the object to be imaged, such as the body 15, shoulder 17, or mouth 18 of the container 13, from a direction in which the imaging optical axis C1 intersects the axis AL of the container 13, a cap (not shown) may be attached to the mouth 18 of the container 13. Also, the object to be imaged, the container 13, is not limited to being empty, but may contain a transparent or translucent liquid that can transmit light.

[0143] - The subject article 12 is not limited to PET bottles or glass containers, as long as it has transparent or translucent parts. Article 12 may be a container 13, for example, a dish, cup, beaker or other laboratory container. Article 12 is not limited to a container, but may also be a transparent or translucent plate or tray-shaped article. It may also be a transparent or translucent synthetic resin product (e.g., an acrylic product), a glass product, or a transparent or translucent part. Furthermore, the shape of article 12 may have an axis AL or may not have an axis AL.

[0144] Article 12 is not limited to being entirely transparent or semi-transparent; it may be partially transparent or semi-transparent. At least a portion of the transparent portion is sufficient to be the object of imaging. Furthermore, the transparent portion of article 12 is not limited to being transparent or semi-transparent to visible light; it may also be transparent or semi-transparent to ultraviolet or infrared light.

[0145] - The imaging device 11 may be used solely for traceability purposes, or solely for inspection purposes to check for the presence or absence of markings, scratches, etc. on the embossed surface 19 of the article 12. - The portion of the article 12 that the imaging device 11 images is not limited to the bottom 16. The imaging device 11 may also image the body 15 of the article 12, or the mouth 18.

[0146] 10...Item inspection device, 11...Imaging device, 11A...First imaging device, 11B...Second imaging device, 11C...Third imaging device, 11D...Fourth imaging device, 12...Item, 13...Container, 15...Body, 16...Bottom, 17...Shoulder, 18...Mouth, 19...Embossing, 20...Illumination unit, 20A...First illumination unit, 20B...Second illumination unit, 20C...Third illumination unit, 20D...Fourth illumination unit, 21...Light-emitting unit, 30...Camera, 30A...First camera, 30B...Second camera, 30C...Third camera, 30D...Fourth camera, 30a...Lens barrel, 31...Lens, 33...Image sensor, 33A...Imaging pixel, 35...Focus adjustment unit, 36...Lens position adjustment unit, 37...Rail, 40...Optical path control member, 40A...First optical path control member, 40B...Second optical path control member, 40C...Third optical path control member, 40D...Fourth optical path control member, 40S...Sheet surface, 41...Light shielding part, 42...Light transmitting part, 43...Optical path control member, 44...Optical path control member, 45...Optical path control member, 46...Sheet-like member, 46A...Sheet-like member, 46B...Sheet-like member, 47...Optical path control member, 48 ...Optical path control member, 50...Control unit, 51...Imaging control unit, 52...Signal processing unit, 53...Image processing unit, 60...Inspection processing unit, 65...Display unit, 70...Transport unit, 71...Sensor, 75...Adjustment unit, 80...Angle adjustment unit, 81...Angle adjustment axis, 82...Motor, 100...Imaging system, L...Diffused light, L1...Light, L2...Light (transmitted light), AL...Axis, PA...Attitude angle, MD...Direction of movement, C1...Imaging optical axis, C2...Transmitted light axis, C3...Transmitted light axis, S1...Imaging signal, S2...Image signal, SP...Imaging position, SP1...First imaging Position, SP2...Second imaging position, SP3...Third imaging position, SP4...Fourth imaging position, Img...Image (transmitted image), Img1-Img4...Image (transmitted image), SL...Scale, SI...Image, IS...Captured image, IS0...Captured image of comparative example, IS1...Captured image of comparative example, IS2...Captured image of example, IS3...Captured image of example, IS4...Captured image of example, IS5...Captured image of example, T0...Distribution line, T1...Distribution line, T2...Distribution line, LV1...Transmitted light, LV2...Transmitted light, θ1...Field of view angle, θ2...Field of view angle.

Claims

1. An imaging device for imaging an article having at least a portion of a transparent or translucent portion through which light can pass, comprising: an illumination unit for illuminating the article placed at an imaging position; a camera positioned opposite the illumination unit to the article; a sheet-shaped optical path control member positioned between the illumination unit and the article and having light-shielding portions and light-transmitting portions arranged in a two-dimensional arrangement pattern on a sheet surface; and a control unit for causing the camera to image the article and the transmitted light that has passed through the light-transmitting portions to acquire an image, wherein the pitch of the light-transmitting portions is less than or equal to the pixel resolution of the camera, and the transmitted light axis, which is the optical axis of the transmitted light that passes through the light-transmitting portions and is restricted to a predetermined field of view by the light-shielding portions, is inclined at an acute angle with respect to the imaging optical axis of the camera.

2. The imaging apparatus according to claim 1, wherein the optical path control member comprises one or more sheet-like members and a light-transmitting portion formed on the sheet-like member and extending in the thickness direction of the sheet-like member, and the optical path control member is arranged in a position inclined with respect to the imaging optical axis.

3. The imaging apparatus according to claim 1, wherein the optical path control member comprises one or more sheet-like members and one or more light-transmitting portions formed on the sheet-like members, the light-transmitting portions extending in an oblique direction such that the transmitted light axis is inclined at the acute angle with respect to the thickness direction of the sheet-like member, and the optical path control member is arranged such that the transmitted light axis of the one or more light-transmitting portions is inclined with respect to the imaging light axis.

4. The imaging apparatus according to claim 3, wherein two or more light-transmitting portions are provided, each extending in the oblique direction such that the transmitted light axis is inclined at two or more different angles with respect to the thickness direction of the sheet-like member, and the optical path control member is arranged such that the transmitted light axes of the two or more light-transmitting portions are inclined with respect to the imaging light axis.

5. The imaging device according to claim 1, further comprising an adjustment unit for adjusting the contrast of the image, wherein the adjustment unit is configured to adjust at least one of the attitude angle of the optical path control member, the lens position of the camera, and the focal length of the camera.

6. The imaging device according to claim 1, wherein the camera images the article multiple times under multiple conditions in which the direction in which the transmitted light axis of the light-transmitting portion of the optical path control member is inclined with respect to the imaging light axis is different.

7. The imaging device according to claim 1, wherein the article is a container having an opening and a bottom which is the transparent or translucent portion, the container is positioned at the imaging position with the opening facing the camera and the bottom facing the illumination unit, and the camera images the inner bottom surface of the bottom through the opening.

8. An article inspection device comprising an imaging device according to any one of claims 1 to 7, and an inspection processing unit that inspects recesses or protrusions of an article based on the image captured by the imaging device.

9. An imaging method for imaging an article having at least a portion of a transparent or translucent portion through which light can pass, comprising: illuminating the article, which is placed at an imaging position, with an illumination unit; and acquiring an image by imaging the article and the transmitted light that has passed through the transmitted portion with respect to the article, with an optical path control member having a light-shielding portion and a light-transmitting portion arranged in two dimensions, placed between the illumination unit and the article, wherein the pitch of the light-transmitting portion is less than or equal to the pixel resolution of the camera, and the transmitted light axis, which is the optical axis of the transmitted light that passes through the light-transmitting portion and is restricted to a predetermined field of view by the light-shielding portion, is inclined at an acute angle with respect to the imaging optical axis of the camera.

Images