Coin visual inspection device
By employing oblique illumination units and cameras to capture specularly reflected light from coin edges, the device achieves precise imaging and inspection of serrated patterns, enhancing the accuracy of coin appearance evaluation.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- FUJI ELECTRIC CO LTD
- Filing Date
- 2022-08-26
- Publication Date
- 2026-06-02
Smart Images
Figure 0007868457000001 
Figure 0007868457000002 
Figure 0007868457000003
Abstract
Description
Technical Field
[0001] The present invention relates to an appearance inspection device that mainly inspects the appearance of patterns and the like formed on the front and back surfaces and the peripheral edge of a coin in the final process of a coin manufacturing line. In particular, the present invention relates to a coin appearance inspection device that can accurately inspect the serration pattern and the like on the outer peripheral surface of the edge of a coin.
Background Art
[0002] In a coin manufacturing line, defective products are generated due to various reasons. Examples of types of defects include chipping of coins, misalignment or blurring of patterns, eccentricity of holes, chipping of embossing / stamping, soiling of coins, and mixing of different types of coins. In the final process, it is required to conduct an appearance inspection to reliably distinguish between non-defective coins without the above-mentioned defects and defective coins with defects and sort them. In addition, the objects of appearance inspection include not only the patterns on the front and back surfaces of coins, but also the serration patterns formed on the outer peripheral surface of the edge for anti-counterfeiting, the finished state of irregular serration patterns with uneven intervals between each serration part, and the phase (shift) state between these serration patterns and the characters and patterns on the front and back surfaces.
[0003] Conventionally, visual inspection by an inspector has been the mainstream for inspecting the appearance of coins. However, for about 20 years, appearance inspection devices that process captured images by a camera to determine the quality of the appearance have been introduced. Since the initial appearance inspection device had limitations in the sensitivity of the camera and the like, it was necessary to expose the coin in a stationary state. Therefore, the coin was transported while repeatedly accelerating, decelerating, and stopping using an index table that holds the coin, and the front and back surfaces and the edge of the coin were imaged at the stop timing in the transport process.
[0004] Here, Patent Document 1 describes an appearance inspection device that images the upper surface, lower surface, and outer diameter surface of a coin while it is moving without stopping the coin that moves by its own weight, and performs an appearance inspection. Figure 15 is a diagram showing the main components of the optical system of this appearance inspection device. In Figure 15, C0 is a coin that moves on an inclined transport surface 156 by its own weight, 150 is a ring-shaped mirror positioned on the upper side of coin C0, 151 is a ring-shaped first LED that illuminates the upper surface of coin C0, 152 is a first camera that receives reflected light from the upper surface of coin C0 and takes an image, 153 is a transparent plate positioned on the lower side of coin C0, 154 is a ring-shaped second LED that illuminates the lower surface of coin C0, 155 is a second camera that receives reflected light from the lower surface and the area around the edge of coin C0 and takes an image, and 157 is a coin arrival sensor that detects when coin C0 has reached the imaging position.
[0005] In this visual inspection device, the second camera 155 can receive not only reflected light from the underside of the coin C0, but also reflected light from the outer edge of the coin C0 by the mirror 150. Therefore, the patterns on the front and back surfaces of the coin C0 and the patterns around the edges can be imaged and inspected almost simultaneously.
[0006] However, since the speed of the coin C0 moving on the conveying surface 156 depends solely on the weight of the coin C0 and the inclination angle of the conveying surface 156, it is difficult to improve the processing speed per unit time. Furthermore, if the mirror 150 is dirty, the amount of reflected light from the outer edge of the coin C0 that enters the second camera 155 via the mirror 150 decreases, making it difficult to accurately image the jagged pattern and other features on the outer edge of the coin. Furthermore, the visual inspection device described in Patent Document 1 is primarily intended for integration into coin processing machines such as coin deposit machines and coin deposit / withdrawal machines, and is unsuitable for applications requiring high-speed inspection of the appearance of coins in the final stage of a coin manufacturing line.
[0007] Against this backdrop, the applicant has already filed a patent application for a coin appearance inspection device, as shown in Patent Document 2, which improves the processing capacity of a series of processes including coin transport and imaging, enables more accurate imaging of the patterns on the front and back surfaces and around the edges of coins, and facilitates application to coin manufacturing lines. This coin visual inspection device is configured to continuously supply coins to a cutting section with a predetermined initial speed and gravity, introduce the cut coins one by one into an imaging section, and capture images of the first and second sides (front and back) and the surrounding edges of the coins as they move using a single-side camera and a double-side camera, after which a sorting section sorts the coins into good and defective coins. [Prior art documents] [Patent Documents]
[0008] [Patent Document 1] Japanese Patent Publication No. 5140510 (Figures 1, 5, etc.) [Patent Document 2] Japanese Patent Publication No. 2021-68359 (Figures 1-3,
[0036] ,
[0037] , etc.) [Overview of the Initiative] [Problems that the invention aims to solve]
[0009] The coin appearance inspection device described in Patent Document 2 can improve processing capacity compared to the appearance inspection device described in Patent Document 1, and can also be applied to the final stage of a coin manufacturing line. However, in this coin appearance inspection device, a ring-shaped first oblique illumination unit is positioned, for example, on the side of the single-sided camera. The single-sided camera receives the reflected light from the edge of the coin by the first oblique illumination unit via a first ring-shaped prism, thereby imaging the pattern around the edge of the first side of the coin. Similarly, the pattern around the edge of the second side of the coin is imaged by the two-sided camera using a second oblique illumination unit and a second ring-shaped prism positioned on the side of the two-sided camera.
[0010] As described above, when imaging reflected light from the outer surface of a coin, particularly the rim, using an oblique illumination unit and a camera positioned on the same inspection surface of the coin, if the coin is already in circulation, the outer surface of the rim has a certain degree of roughness, so the reflected light necessary to reproduce the serrated pattern can be obtained. However, with a coin that has just been manufactured, the rim is almost mirror-like, so the light from the oblique illumination unit is specularly reflected, and it is not possible to obtain sufficient reflected light incident on the camera, making it difficult to accurately image the serrated pattern on the outer surface of the rim.
[0011] Here, Figure 16(a) is an image of one side of a 500 yen coin taken using prior art (for example, a coin appearance inspection device described in Patent Document 2), and Figure 16(b) is a magnified image of the area enclosed by a square in (a). Figures 17(a) and (b) are images of the other side of the 500 yen coin taken in the same manner. As can be seen from these figures, conventional methods have not been able to accurately image the serrated patterns on the outer edge of coins, resulting in problems such as parts of the pattern becoming unclear.
[0012] Therefore, the problem to be solved by the present invention is to provide a coin appearance inspection device that improves inspection accuracy by accurately imaging the jagged pattern, phase, etc. on the outer surface of the coin, by imaging the reflected light of the light irradiated onto the surface to be inspected by a camera on the surface to be inspected side of the coin, and by irradiating the area around the edge of the coin with light from an oblique illumination unit installed on the opposite side of the surface to be inspected, and imaging the specular reflected light from the area around the edge, especially the outer surface of the edge, with the camera. [Means for solving the problem]
[0013] To solve the above problems, the coin appearance inspection apparatus of the present invention, as described in claim 1, illuminates one side of a coin that has reached an imaging position on a transport path with a single-side illumination unit and images the reflected light with a single-side camera, illuminates two sides of the coin with a double-side illumination unit and images the reflected light with a double-side camera, and processes the images captured by the single-side camera and the double-side camera to inspect the appearance of the coin, The aforementioned single-sided illumination unit comprises an incident illumination unit and a diffuse illumination unit for illuminating one side of the coin, and an oblique illumination unit for illuminating the flat pattern and edge of one side of the coin. The two-sided illumination unit comprises an incident illumination unit and a diffuse illumination unit that illuminate the two sides of the coin, and an oblique illumination unit that illuminates the flat pattern and edges of the two sides of the coin. When the single-sided camera images one side of the coin, the single-sided camera receives specularly reflected light from the oblique illumination unit of the two-sided illumination unit illuminating the edge, and when the two-sided camera images two sides of the coin, the two-sided camera receives specularly reflected light from the oblique illumination unit of the single-sided illumination unit illuminating the edge.
[0014] In particular, the present invention is characterized in that the specularly reflected light of the irradiated portion of the edge is the specularly reflected light of the irradiated portion of the jagged pattern formed on the outer peripheral surface of the edge. [Effects of the Invention]
[0015] According to the present invention, the pattern around the edge of a coin, including the serrated pattern on the outer rim, can be imaged with high precision along with the patterns on the front and back surfaces, allowing for accurate inspection of the coin's appearance, including any chipping, distortion, or staining of the pattern, as well as the phase relationships between patterns. In particular, even for coins whose outer edges are mirror-like immediately after manufacturing, this technology can reliably capture specularly reflected light from the outer edges and obtain accurate images, thereby improving the accuracy of visual inspection compared to conventional techniques. [Brief explanation of the drawing]
[0016] [Figure 1] This is a diagram showing the configuration of a coin appearance inspection device according to an embodiment of the present invention. [Figure 2] Figure 1 is a diagram showing the configuration of the cutting unit and its control device. [Figure 3] This is an explanatory diagram of the opening of the transport guide near the image acquisition position of the coin. [Figure 4] Figure 1 is a cross-sectional view showing the internal structure of the camera box along with the optical path of the illumination light. [Figure 5] It is an explanatory diagram of the ring-shaped prism in FIG. 4. [Figure 6] It is a cross-sectional view showing the internal structure of the camera box in another embodiment of the present invention. [Figure 7] It is an explanatory diagram of the diffusion prism in FIG. 6. [Figure 8] It is a cross-sectional view for explaining the operation of the diffusion prism in FIG. 7. [Figure 9] It is an overall circuit configuration diagram of an embodiment of the present invention. [Figure 10] It is a circuit configuration diagram of the main part in FIG. 9. [Figure 11] It is an explanatory diagram of the lighting time and light intensity of the oblique illumination unit driven by each power supply unit in FIG. 10. [Figure 12] It is a timing chart showing the operation of an embodiment of the present invention. [Figure 13] (a) is an imaging image of one side of a 500-yen coin captured according to an embodiment of the present invention, and (b) is an enlarged image of the portion surrounded by □ in (a). [Figure 14] (a) is an imaging image of the other side of a 500-yen coin captured according to an embodiment of the present invention, and (b) is an enlarged image of the portion surrounded by □ in (a). [Figure 15] It is a configuration diagram of the optical system of the appearance inspection device described in Patent Document 1. [Figure 16] (a) is an imaging image of one side of a 500-yen coin captured according to the prior art, and (b) is an enlarged image of the portion surrounded by □ in (a). [Figure 17] (a) is an imaging image of the other side of a 500-yen coin captured according to the prior art, and (b) is an enlarged image of the portion surrounded by □ in (a).
Mode for Carrying Out the Invention
[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figure 1(a) is a schematic overall configuration diagram of the coin appearance inspection device according to this embodiment, Figure 1(b) is a side view of the imaging unit in Figure 1(a), and Figure 1(c) is an explanatory diagram of the force acting on the uninspected coins in the transport guide. The configuration of this embodiment is substantially the same as the appearance inspection device described in Patent Document 2, except for the imaging unit 250 which will be described later. The following will provide a general overview of the system, focusing on the means of transporting coins.
[0018] In Figure 1(a), uninspected coins (hereinafter also simply referred to as coins) C0, which are fed from the preceding process (stamping process) of the coin manufacturing line, are aligned upright by the coin feeder 10 and supplied to the cutting section 200 via the vertically positioned transport guides 20. The coin feeder 10's alignment output capability is set higher than the processing capacity of the imaging unit 250 (described later), and the supply amount is controlled so that multiple coins C0 accumulate continuously at the entrance of the cutting unit 200. Since the coin feeder 10 supplies coins C0 asynchronously with the dispensing unit 200, if the dispensing operation is performed before the coins C0 have reached the entrance of the dispensing unit 200, jamming will occur, leading to damage to the coins C0 or shutdown of the device. Therefore, coin arrival sensors 301 and 302 are placed upstream of the dispensing unit 200 and inside the dispensing unit 200, and the dispensing operation is not performed if the coins C0 are not detected by these sensors 301 and 302.
[0019] The cutting unit 200 rotates a pair of cutting discs 210 and 220 in opposite directions, separating the coins C0 that are trapped in the transport guide 20 one by one at predetermined time intervals and sending them out towards the transport guide 21. In this embodiment, the coins C0 are not sent out (dropped) by gravity alone, but are sent out while a constant initial velocity is given to the coins C0 by the rotational force of the cutting discs 210 and 220. When the cutting unit 200 separates and sends out the coins C0 one by one, gaps are created between the coins C0 supplied to the imaging unit 250. As a result, the edges of the coins C0 are sufficiently illuminated by illumination light, and the reflected light from the edges is reliably incident on the single-plane camera 115 and the double-plane camera 125 via the lenses 114 and 124 described later.
[0020] In the cutting unit 200, for example, if 500 yen coins are cut every 60 ms, 1000 coins / minute can be processed in one system, and the mechanism for transporting the coins C0 to the imaging position can be greatly simplified compared to the conventional technology in Patent Document 1. The processing capacity of the stamping machine (not shown) located upstream of this appearance inspection device is about 850 coins / minute, so the above-mentioned processing capacity is sufficient for the cutting unit 200. At the entrance to the cutting section 200, it is desirable to shorten the vertical portion of the transport guide 20 so that the free fall velocity of the coin C0 does not become too high.
[0021] Figure 2 is a detailed configuration diagram of the cutting unit 200 and its control device. As shown in Figure 2(a), the cutting unit 200 is equipped with cutting discs 210 and 220 that rotate in opposite directions, and multiple cutting protrusions 210a and 220a are formed on the outer circumferential surfaces of these cutting discs 210 and 220, with spacing between them that allows for the insertion of one coin C0. P1 and P2 are imaging positions by the imaging unit 250, which will be described later, and 303 is a coin arrival sensor that detects when the coin C0 has reached the imaging positions P1 and P2. If the type of coin C0 to be inspected changes and the outer diameter of the coin changes, the transport guides 20, 21 and the cutting discs 210, 220 can be replaced to address the issue.
[0022] Figures 2(b) and 2(c) show examples of the configuration of the control device for the cutting unit 200. Figure 2(b) shows an example of rotating the cutting discs 210 and 220 at high speed using synchronous servo motors 231 and 232 with an output of 0.1 kW, for example, while Figure 2(c) shows an example of rotating the cutting discs 210 and 220 using a single synchronous servo motor 233 and a drive gear 234. In these figures, 230 is a synchronous servo controller. By rotating the cutting discs 210 and 220 synchronously at the same speed, coin C0 can be cut without rotating it. Not rotating coin C0 is important for performing a rotation angle inspection (inspection of the displacement angle (phase angle) of the imprinted pattern along the circumferential direction of the front and back of coin C0) based on the patterns on the front and back of coin C0 when imaging coin C0. If a slight rotation of the coin C0 is acceptable, the coin C0 may be cut using a single cutting disc.
[0023] It is desirable that the coin C0 cut out by the cutting unit 200 be free from the displacement in the x direction (horizontal direction) and the floating in the z direction (direction toward the front of the paper) as shown in Figure 1(a). The transport surface of the transport guide 21 from the cutting unit 200 to the imaging unit 250 should, of course, have a low coefficient of friction, but in particular, to eliminate the floating of the coin C0 in the z direction, it is effective to slightly incline the transport direction of the coin C0 with respect to the y direction (vertical direction, i.e., the direction in which gravity acts) in Figure 1(a). Figures 1(b) and 1(c) show the state in which the transport direction 21a of the transport guide 21, i.e., the transport surface, is inclined at an angle θ with respect to the vertical direction. As a result, if the mass of the coin C0 is m and the acceleration due to gravity is G, a pressing force F (=mGcosθ) shown in Figure 1(c) is applied from the coin C0 to the transport surface, thereby suppressing the floating of the coin C0.
[0024] Figure 3 is an explanatory diagram of the opening 21B of the transport guide 21 near the imaging position of coin C0. The length of the opening 21B formed in the middle of the transport guide 21 along the coin transport direction is L1=L2, allowing the single-sided camera 115 and the double-sided camera 125 to image the front, back, and edge CX of the coin C0 almost simultaneously with a slight time difference. The shape of the opening 21B can be any shape, such as a circle or an ellipse, as long as there is no risk of obstructing the illumination light from the multiple illumination units described below.
[0025] The arrival of coin C0 at the imaging position is detected by the coin arrival sensor 303. Considering the need to accommodate multiple types of coins with different outer diameters, the coin arrival sensor 303 is positioned to detect when the coin with the smallest outer diameter reaches the imaging position. For coins with larger outer diameters, the delay time corresponding to the difference in outer diameter travel time can be adjusted accordingly. For example, a 5-yen coin has an outer diameter of 22.2 mm, and a 500-yen coin has an outer diameter of 26.5 mm, a difference of 4.3 mm (the difference in radius is approximately 2.2 mm). Therefore, if the transport speed of coin C0 at the imaging position is 1.0 m / s, a delay time of approximately 2.2 ms should be set according to the difference in radius.
[0026] Next, as shown in Figure 1(b), the imaging unit 250 includes camera boxes 110 and 120 positioned on both sides of the transport guide 21, and inside these are respectively oblique illumination units 111 and 121, diffuse illumination units 112 and 122, incident illumination units 113 and 123, lenses 114 and 124, a single-plane camera 115, and a double-plane camera 125. Here, the oblique illumination section 111, the diffuse illumination section 112, and the incident illumination section 113 constitute the one-sided illumination section in the claim, and the oblique illumination section 121, the diffuse illumination section 122, and the incident illumination section 123 constitute the two-sided illumination section in the claim.
[0027] Figures 4(a) and 4(b) are cross-sectional views showing the internal structure of the camera boxes 110 and 120 along with the optical path of the illumination light. Figure 4(a) shows the optical path superimposed when imaging is performed by the two-plane camera 125, and Figure 4(b) shows the optical path superimposed when imaging is performed by the one-plane camera 115. The structures of the oblique illumination sections 111, 121, the diffuse illumination sections 112, 122, the incident illumination sections 113, 123, etc., will be described below based on Figures 4(a) and (b).
[0028] The oblique lighting sections 111 and 121 are formed in a ring shape, with numerous LEDs arranged on their inner surface. These LEDs emit highly directional light at a low angle onto the flat patterns and edges CX on each face of the coin C0. The diffuse illumination sections 112 and 122, adjacent to the oblique illumination sections 111 and 121, are also formed in a ring shape with numerous LEDs arranged on their inner surface. The light emitted from these LEDs passes through the ring-shaped prisms 116 and 126 made of transparent acrylic or optical glass, becoming a weakly directional diffused light that illuminates the entire front and back surfaces of the coin C0. Figure 5(a) is a front view of the ring-shaped prisms 116 and 126, and (b) is a cross-sectional view of AA, which has a structure in which a hollow cone is cut by a plane perpendicular to its axis. The incident illumination units 113 and 123, adjacent to the diffuse illumination units 112 and 122 respectively, emit light from numerous LEDs positioned on their internal bottom surfaces. This light is then filtered through diffuser plates 113a and 123a and half mirrors 113b and 123b to become parallel light, illuminating both sides of the coin C0.
[0029] Next, we will explain the light paths provided by each lighting unit. As shown in Figure 4(a), when imaging is performed by the two-sided camera 125, the light emitted from the oblique illumination unit 111 on one side of the coin C0 is specularly reflected by the outer circumferential surface of the edge of the coin C0, and this reflected light enters the ring-shaped prism 126 on the second side of the coin C0, undergoing multiple reflections, and then enters the two-sided camera 125 via the lens 124. In addition, the light emitted from the diffuse illumination unit 122 on the second side of the coin C0 becomes diffused light via the ring-shaped prism 126 and illuminates the entire two sides of the coin C0, and this reflected light enters the two-sided camera 125 via the lens 124. Furthermore, the light emitted from the incident illumination unit 123 on the second side of the coin C0 illuminates the entire two sides of the coin C0 via the diffuser plate 123a and half mirror 123b, and this reflected light enters the two-sided camera 125 via the lens 124.
[0030] On the other hand, as shown in Figure 4(b), the optical path when imaging with the single-sided camera 115 is symmetrical to that when imaging with the double-sided camera 125 described above. The light that is illuminated from the oblique illumination unit 121 on the double-sided side, specularly reflected by the outer circumferential surface of the edge of the coin C0, and comes through the ring-shaped prism 116, along with the light reflected from the entire surface of one side of the coin C0 by the diffuse illumination unit 112 and the ring-shaped prism 116, and the light reflected from the entire surface of one side of the coin C0 by the incident illumination unit 113, all enter the single-sided camera 115 via the lens 114. In Figures 4(a) and 4(b), the housings of the incident illumination units 113 and 123 are depicted as interfering with the optical path. However, it goes without saying that by providing openings in the housings or by forming the housings themselves from transparent materials, the structure is designed so that they do not interfere with the optical path.
[0031] Next, Figure 6 is a cross-sectional view showing the internal structure of camera boxes 110 and 120 in another embodiment of the present invention. In this embodiment, ring-shaped diffusion prisms 117 and 127, made of transparent acrylic or optical glass, are arranged on the inner surfaces of the ring-shaped prisms 116 and 126. Figure 7(a) is a front view of the diffusion prisms 117 and 127, and (b) is a cross-sectional view of BB. The overall structure is similar to that of the ring-shaped prisms 116 and 126, having been cut by a plane perpendicular to the axis of a hollow cone.
[0032] Figure 8 is a cross-sectional view illustrating the action of diffusion prism 127 (and the same for diffusion prism 117) as an example. The light emitted by the diffuse illumination unit 122 passes through the ring-shaped prism 126 and is diffusely reflected by the diffuse reflective surface 127b of the diffuse prism 127 via the transmissive surface 127a made of transparent adhesive or the like. This diffusely reflected light passes through the inside of the diffuse prism 127 to the diffuse reflective surface 127c, is reflected again, and is emitted from the transmissive surface 127d, thereby illuminating both sides of the coin C0 as diffusely reflected light (indirect illumination light). Furthermore, the reflected light, which is illuminated from the oblique illumination unit 111 on one side of the coin C0 and specularly reflected from the outer surface of the edge CX of the coin C0, is reflected from the inner bottom surface of the ring-shaped prism 126, further reflected by the diffuse reflection surface 127c, passes through the inside of the ring-shaped prism 126, and reaches the two-sided camera 125 via a lens 124 (not shown).
[0033] As described above, based on the images captured by the imaging unit 250 of the front and back surfaces and edge CX of the coin C0 by the single-sided camera 115 and the double-sided camera 125, the CPU 510 in the image processing PC 500 (described later) inspects the coin C0 for chips, phase shifts or positional shifts of patterns, chips in imprints or markings, dirt on the coin, serrations on the edge CX, etc., to determine the quality of its appearance and transport it in the direction of the sorting unit 400 as shown in Figure 1(a) above. When the coin arrival sensor 304 detects that the coin C0 has been delivered to the sorting unit 400, good coins C are collected from the transport guide 91 into the good coin collection box 90, and defective coins C1 are collected from the transport guide 61 into the defective coin collection box 60.
[0034] Next, Figure 9 is an overall circuit diagram of an embodiment of the present invention. In Figure 9, the image processing PC 500 includes a CPU 510 that comprehensively controls the entire device, image processing units 501 and 502 that process the single-sided image signal from the single-sided camera 115 and the double-sided image signal from the double-sided camera 215, respectively, triggered by the coin arrival signal from the coin arrival sensor 303, and generate control signals for the single-sided illumination power supply unit 710, the double-sided illumination power supply unit 720, and the edge oblique illumination power supply unit 730, and a DIO (digital input / output) board 503 that outputs the visual inspection result of the coin C0 by the CPU 510 as an inspection result signal to the PLC (programmable logic controller) 600 for mechanism control, and digitally outputs the lighting time and illumination light intensity setting values for each illumination unit to each power supply unit 710, 720, and 730. Furthermore, the PLC600 is configured to generate a control reject signal based on the inspection result signal and timing signal, and output it to various parts of the device.
[0035] Furthermore, the single-sided illumination power supply unit 710 supplies power voltage to the oblique illumination unit 111, the diffuse illumination unit 112, and the incident illumination unit 113 from its output ports "oblique 1", "diffuse 1", and "incident 1", respectively, while the two-sided illumination power supply unit 720 supplies power voltage to the oblique illumination unit 121, the diffuse illumination unit 122, and the incident illumination unit 123 from its output ports "oblique 2", "diffuse 2", and "incident 2". Furthermore, the edge-mounted oblique lighting power supply unit 730 has, as enclosed by the ellipse, an output port "oblique 22" which is wired or connected to the output port "oblique 1" of the single-sided lighting power supply unit 710, and an output port "oblique 12" which is wired or connected to the output port "oblique 2" of the two-sided lighting power supply unit 720.
[0036] Figure 10 shows a circuit diagram illustrating the connection relationship between the output ports "diagonal 1" and "diagonal 22" described above. In the diagram, the power supply unit 7101 for single-sided diagonal lighting corresponds to output port "diagonal 1," and the power supply unit 7301 for edge diagonal lighting corresponds to output port "diagonal 22." The combined output of these single-sided diagonal lighting power supply units 7101 (diagonal 1) and edge diagonal lighting power supply unit 7301 (diagonal 22) is supplied to the diagonal lighting unit 111 on the single-sided side. The connection relationship for providing the sum of the output values from output ports "diagonal 2" and "diagonal 12" to the diagonal illumination unit 121 on the two sides is the same and therefore is omitted from the illustration.
[0037] In Figure 10, the single-sided oblique lighting power supply unit 7101 comprises a variable power supply unit 7101a that varies the output voltage according to the intensity setting value input from the DIO board 503 in Figure 9, and a switching element 7101b and a reverse current prevention diode 7101c connected to the variable power supply unit 7101a. Both ends of the series circuit of these are connected to the series-parallel LED group in the oblique lighting unit 111. The on / off time of the switching element 7101b is controlled according to the lighting time setting value input from the DIO board 503 in Figure 9. Similarly, the edge oblique illumination power supply unit 7301 also comprises a variable power supply unit 7301a, a switching element 7301b and a reverse current prevention diode 7301c connected to the variable power supply unit 7301a, and both ends of the series circuit of these are connected to the series-parallel LED group in the oblique illumination unit 111. With the above configuration, the series-parallel LED group within the oblique lighting section 111 is supplied with power voltage from the single-sided oblique lighting power supply section 7101 and the edge oblique lighting power supply section 7301, and is controlled to emit light according to a predetermined light intensity and lighting time.
[0038] Figure 11 shows an example of the lighting time and light intensity of the oblique lighting unit 111, where (a) is operation using power supplied from the single-sided oblique lighting power supply unit 7101, and (b) is operation using power supplied from the edge oblique lighting power supply unit 7301. Note that the lighting time and light intensity can be set arbitrarily.
[0039] Next, Figure 12 is a timing chart showing the operation of an embodiment of the present invention. First, when the coin arrival sensor 303 detects that the transported coin C0 has reached the imaging position within the imaging unit 250, a coin arrival signal is input to the image processing units 501 and 502 in Figure 9. The coins C0 are set to reach the imaging position at intervals of at least 60 ms.
[0040] In the image processing PC 500, after an appropriate length of imaging adjustment time for one side, the image processing unit 501 exposes the one-sided camera 115 for, for example, 75 [μs]. At the same time, a control signal from the DIO board 503 drives the one-sided illumination power supply unit 710 to supply power voltage from the output ports "Oblique 1", "Diffuse 1", and "Incident 1", illuminating the one-sided illumination unit (oblique illumination unit 111, diffuse illumination unit 112, incident illumination unit 113) for, for example, 50 [μs]. At the same time, power voltage is supplied from the output port "Oblique 2" of the two-sided illumination power supply unit 720 via the output port "Oblique 12" of the oblique illumination power supply unit 730 to illuminate the two-sided illumination unit (oblique illumination unit 121). The illumination time and light intensity for "Oblique 1," "Diffuse 1," "Incident 1," and "Oblique 2" can each be set to an optimal value to produce an image that is easy to inspect. As a result, the illumination state shown in Figure 4(b) above is obtained, and the overall pattern on one side of the coin C0 is imaged by the illumination light from the oblique illumination unit 111, diffuse illumination unit 112, and incident illumination unit 113 on the one-side side, while at the same time, the serrated pattern on the outer edge of the coin C0 can be accurately imaged by the one-side camera 115 by the illumination light from the oblique illumination unit 121 on the two-side side.
[0041] Subsequently, the image captured by the single-sided camera 115 is transferred to the image processing unit 501 over a period of, for example, 33 ms, to perform image inspection to determine whether the pattern, its phase, and any irregular serrations on one side of the coin C0 are accurately formed. Finally, as the last step for the single-sided side, the inspection result is notified to the PLC 600.
[0042] For the imaging process of the second side of coin C0, exposure of the second-side camera 125 is started after, for example, 100 [μs] has elapsed since the imaging adjustment time for the first side. Here, if the exposure start times of the one-sided camera 115 and the two-sided camera 125 are 100 [μs] apart, and assuming the movement speed of the transported coin C0 is 1 [m / s], the coin C0 will move approximately 100 [μm] vertically during that 100 [μs] period. However, this displacement of the coin C0 can be corrected by calculations performed by the image processing units 501 and 502, so that the patterns on one side, two sides, and the area around the edge of the coin C0 can be captured at virtually the same time. The amount of rotation of the coin C0 corresponding to the above displacement can be ignored.
[0043] Simultaneously with the exposure of the two-sided camera 125, a control signal from the DIO board 503 drives the two-sided illumination power supply unit 720 to supply power voltage from the output ports "Oblique 2", "Diffuse 2", and "Incident 2", illuminating the two-sided illumination unit (oblique illumination unit 121, diffuse illumination unit 122, incident illumination unit 123) for, for example, 50 [μs]. At the same time, power voltage is supplied from the output port "Oblique 1" of the one-sided illumination power supply unit 710 via the output port "Oblique 22" of the oblique illumination power supply unit 730 to illuminate the one-sided illumination unit (oblique illumination unit 111). The illumination time and light intensity for "Oblique 2," "Diffuse 2," "Incident 2," and "Oblique 1" can each be set to an optimal value to produce an image that is easy to inspect. As a result, the illumination state shown in Figure 4(a) above is obtained, and the overall pattern on both sides of the coin C0 is imaged by the illumination light from the oblique illumination unit 121, diffuse illumination unit 122, and incident illumination unit 123 on the two-sided side. At the same time, the serrated pattern on the outer edge of the coin C0 can also be accurately imaged by the two-sided camera 115 using the illumination light from the oblique illumination unit 111 on the one-sided side.
[0044] The image transfer process, image inspection process, and inspection result notification process for the two-sided camera 115 are the same as those described for the single-sided camera. Then, as the final overall process, the PLC600 combines the inspection results from side 1 and side 2 to make an overall judgment on whether the coin C0 is good or bad based on its appearance. Based on the result of this judgment, the sorting unit 400 in Figure 1 is operated to sort the good coins C and the defective coins C1. The times required for each process shown in Figure 12 are merely illustrative values and are not in any way limiting.
[0045] Images of the front, back, and surrounding edges of a 500 yen coin, captured by the operations described above, are shown in Figures 13 and 14. Figure 13(a) is an image of one side of a 500 yen coin, taken using the diffusion prisms 117 and 127 shown in Figures 6 to 8. Figure 13(b) is a magnified image of the area enclosed by the square in (a). Figures 14(a) and (b) are images of the other side of the 500 yen coin, taken in the same manner. As can be seen from these figures, the coin appearance inspection device of the present invention can clearly image patterns on the edge of a coin, irregular serrations where the spacing between each serration on the outer surface of the edge is uneven, and the phase between these patterns and the characters on the front and back sides. For this reason, the present invention can contribute to improving the accuracy of appearance inspection. [Explanation of Symbols]
[0046] C0: Unchecked coin C1: Defective coins C: Good quality coin CX:Edge P1, P2: Imaging positions G0, GX: Pattern 10: Coin feeder 20,21,61,91: Conveyor guide 21a: Conveying direction (conveying surface) 21B: Opening 60: Defective product collection box 90: Good product collection box 110,120: Camera Box 111,121: Oblique lighting section 112,122: Diffuse illumination section 113,123: Incident illumination section 113a, 123a: Diffuser 113b, 123b: Half mirror 114,124: Lens 115:1 aspect ratio camera 116,126: Ring-shaped prism 117,127: Diffusion prism 125:2-angle camera 127a, 127d: Transparent surface 127b, 127c: Diffuse reflecting surface 200: Cutting section 210,220: Cut disc 210a, 220a: Cut-out protrusion 230: Synchronous servo controller 231, 232, 233: Synchronized servo motors 234: Drive gear 250: Imaging Department 301, 302, 303, 304: Coin arrival sensor 400: Sorting Department 500: Image processing PC 510:CPU 501, 502: Image Processing Unit 503: DIO Board 600:PLC 710: Power supply section for single-sided lighting 7101: Power supply section for 1-sided oblique lighting (oblique 1) 7101a, 7301a: Variable power supply 7101b, 7301b: Switching element 7101c, 7301c: Reverse current protection diode 720: Power supply section for dual-sided lighting 730: Power supply section for edge diagonal lighting 7301: Power supply section for edge diagonal lighting (diagonal 22)
Claims
1. In a coin appearance inspection device, when a coin reaches an imaging position on the transport path, one side of the coin is illuminated by a single-side illumination unit and the reflected light is imaged by a single-side camera, and the two sides of the coin are illuminated by a double-side illumination unit and the reflected light is imaged by a double-side camera, and the images captured by the single-side camera and the double-side camera are imaged to inspect the appearance of the coin, The aforementioned single-sided illumination unit comprises an incident illumination unit and a diffuse illumination unit for illuminating one side of the coin, and an oblique illumination unit for illuminating the flat pattern and edge of one side of the coin. The two-sided illumination unit comprises an incident illumination unit and a diffuse illumination unit that illuminate the two sides of the coin, and an oblique illumination unit that illuminates the flat pattern and edges of the two sides of the coin. A coin appearance inspection device characterized in that, when the single-sided camera images one side of the coin, the single-sided camera receives specularly reflected light from the illuminating portion of the edge by the oblique illumination portion of the two-sided illumination unit, and when the two-sided camera images two sides of the coin, the two-sided camera receives specularly reflected light from the illuminating portion of the edge by the oblique illumination portion of the single-sided illumination unit.
2. In the coin appearance inspection device described in claim 1, A coin appearance inspection device characterized in that the diffuse illumination section and oblique illumination section constituting the one-sided illumination section, and the diffuse illumination section and oblique illumination section constituting the two-sided illumination section, are formed in a ring shape that surrounds the central axis of the coin.
3. In the coin appearance inspection device described in claim 1 or 2, A coin appearance inspection device characterized by comprising a ring-shaped prism that diffuses the light emitted from a diffuse illumination unit constituting the one-sided illumination unit and illuminates one side of the coin, and a ring-shaped prism that diffuses the light emitted from a diffuse illumination unit constituting the two-sided illumination unit and illuminates the two sides of the coin.
4. In the coin appearance inspection device described in claim 3, A coin appearance inspection device characterized in that a ring-shaped diffusion prism is arranged on the inner surface of the ring-shaped prism for diffusing the light incident on the ring-shaped prism and irradiating it onto the coin.
5. In the coin appearance inspection device described in claim 1 or 2, A coin appearance inspection device characterized in that the specularly reflected light of the light irradiated onto the edge is the specularly reflected light of the light irradiated onto the serrated pattern formed on the outer circumferential surface of the edge.