JP6980538B2 - Tablet inspection method and tablet inspection equipment - Google Patents

Description

The present invention relates to a tablet inspection method and a tablet inspection apparatus, and more particularly to an inspection technique using a camera for imaging a tablet.

Conventionally, a tablet inspection device for inspecting the appearance of a tablet has been proposed (for example, Patent Documents 1 to 3). In Patent Document 1, the inspection unit includes a transporting means for transporting tablets and four imaging devices (cameras) for imaging the tablets being transported. The two cameras capture the top and bottom surfaces of the tablet, respectively, and the other two cameras capture the sides of the tablet from opposite sides. The inspection unit performs visual inspection by performing image processing on each of the captured images captured by the camera.

In this patent document 1, since a plurality of cameras are used, the cost is high. On the other hand, in Patent Document 2, the inspection device includes a conveyor for transporting tablets and one imaging device for imaging the tablets being transported. The image pickup apparatus takes an image so that the upper surface of the tablet seen from above and the side surface of the tablet seen from all sides are contained in one captured image.

Specifically, this image pickup device includes one camera and four prisms. The camera is located on the upper side of the tablet, and light from the upper surface of the tablet is imaged on the imaging surface of the camera. The prisms are arranged on all sides of the tablet and reflect the light from the sides of the tablet to the camera. The light is also imaged on the image pickup surface of the camera. This allows the camera to image the appearance of the tablet as seen from five directions. The inspection device inspects the appearance of the tablet by performing image processing on the captured image captured by the camera.

Further, also in Patent Document 3, the inspection device includes a transport unit for transporting the tablet and an image pickup device for capturing an image of the tablet during transport. More specifically, the image pickup apparatus has a camera and two prisms. The camera is located on the upper side of the tablet, and light from the upper surface of the tablet is imaged on the imaging surface of the camera. The two prisms are located at positions that sandwich the tablet, and reflect the light from the side of the tablet to the camera. The light is also imaged on the imaging surface. The prism is arranged so that the camera can take an image of the side surface of the tablet from the side. The inspection device inspects the appearance of the tablet by performing image processing on the captured image captured by the camera.

International Publication No. 2015/041112 Japanese Unexamined Patent Publication No. 2012-123009 Japanese Unexamined Patent Publication No. 2004-45097

For example, when the upper surface of the tablet is imaged vertically as in Patent Documents 1 to 3, the chip formed on the peripheral edge of the upper surface of the tablet is located on the outer periphery of the tablet. The outer circumference of the tablet referred to here refers to the outline of the tablet area occupied by the tablet in the captured image. As described above, the chip located on the outer periphery of the tablet can be easily detected from the captured image. This is because the chipping occurs at the boundary between the tablet region and the background region in the captured image.

On the other hand, for example, if the tablet is imaged diagonally upward, this one-way imaging captures both the top surface and the side surface of the tablet. In this case, in the captured image, the upper surface and the side surface of the tablet are in contact with each other. That is, in this captured image, the portion of the peripheral surface of the upper surface of the tablet that is in contact with the side surface is located inside the tablet region, not the outer circumference of the tablet (outline of the tablet region). When a chip of a tablet occurred in the portion, it was difficult to detect the chip from the captured image.

Therefore, an object of the present invention is to provide a tablet inspection method and a tablet inspection apparatus capable of detecting a chipping of a tablet generated on the boundary between the main surface and the side surface in a captured image in which the main surface and the side surface of the tablet are in contact with each other. ..

The first aspect of the tablet inspection method is a tablet inspection method for inspecting the appearance of a tablet having a pair of a first main surface and a second main surface and a side surface, wherein the tablet is imaged and the first main surface is described. Corresponds to the step (a) of generating an captured image in which both of the side surfaces are captured, and the boundary between the main surface region and the side surface region occupied by the first main surface and the side surface of the tablet in the captured image. A step (b) of specifying a boundary edge and calculating a first approximation line that approximates the boundary edge based on a function indicating the shape of the boundary in the captured image, each pixel on the boundary edge, and the above. A step (c) of determining that the peripheral edge of the first main surface of the tablet is chipped when the distance from the first approximation line is longer than a predetermined threshold value is provided.

The second aspect of the tablet inspection method is the tablet inspection method according to the first aspect, wherein the main surface region and the side surface region constitute a tablet region occupied by the tablet in the captured image. In the step (b), an edge detection process is performed on the captured image to generate an edge image (b1), and a tablet edge corresponding to the contour of the tablet region is specified from the edge image (b2). And the outer edge and side surface of the main surface corresponding to the portion of the peripheral edge of the first main surface in the captured image that becomes a part of the contour of the tablet region and the peripheral edge of the second main surface in the captured image, respectively. The boundary edge is specified by the step (b3) of extracting the outer edge from the tablet edge and the search for pixels in the search region separated from the side surface outer edge by a predetermined distance along a predetermined direction in the edge image. Based on the step (b4) and the function indicating the shape of the contour of the main surface region in the captured image, the second approximation line of the pair of main surface edges of the main surface outer edge and the boundary edge is calculated. A step (b5) and a step (b6) of extracting the first approximation line of the boundary edge from the second approximation line are provided.

The third aspect of the tablet inspection method is the tablet inspection method according to the second aspect, wherein the tablet has a substantially disk shape, the function is a function indicating an ellipse, and the second approximation line. Is an ellipse.

The fourth aspect of the tablet inspection method is the tablet inspection method according to the second or third aspect, and in the step (b4), the pixels in the search area of the edge image are included in the pixels. The boundary edge is specified by searching for a pixel in which the pixel value of the corresponding pixel of the captured image is larger than a predetermined threshold value.

A fifth aspect of the tablet inspection method is the tablet inspection method according to the third or fourth aspect, and in the step (b4), in the search region, the side surface outer edge is directed toward the main surface outer edge. The pixel is searched for to identify the boundary edge.

The sixth aspect of the tablet inspection method is the tablet inspection method according to any one of the second to fifth aspects, from the second approximation line of the main surface edge calculated in the step (b5). When the distance between the step of extracting the third approximation line of the outer edge of the main surface and the distance between each pixel on the outer edge of the main surface and the third approximation line is longer than a predetermined threshold value, the tablet is said to be said. A step of determining that the peripheral edge of the first main surface is chipped is provided.

The seventh aspect of the tablet inspection method is the tablet inspection method according to any one of the second to sixth aspects, from the second approximation line of the main surface edge calculated in the step (b5). When the step of extracting the fourth approximation line of the side surface outer edge and the distance between each pixel on the side surface outer edge and the fourth approximation line is longer than a predetermined threshold value, the second of the tablets. It is provided with a step of determining that the peripheral edge of the main surface is chipped.

An eighth aspect of the tablet inspection device is a tablet inspection device for inspecting the appearance of a tablet having a pair of a first main surface and a second main surface and a side surface, wherein the tablet is imaged and the first main surface is described. The image processing unit includes an image pickup unit that generates an image capture image in which both of the side surfaces are captured, and the image processing unit includes a main surface region occupied by the first main surface and the side surface of the tablet in the captured image. The boundary edge corresponding to the boundary between the image and the side region is specified, and a first approximation line that approximates the boundary edge is calculated based on a function indicating the shape of the boundary in the captured image, and the boundary edge is calculated. When the distance between each of the above pixels and the first approximation line is longer than a predetermined threshold value, it is determined that the peripheral edge of the first main surface of the tablet is chipped.

According to the first aspect of the tablet inspection method and the eighth aspect of the tablet inspection apparatus, in the captured image in which the first main surface and the side surface of the tablet are in contact with each other, the tablet generated on the boundary between the first main surface and the side surface. Chips can be detected.

According to the second aspect of the tablet inspection method, the first approximation line of the boundary edge can be appropriately obtained.

According to the third aspect of the tablet inspection method, since an appropriate function is adopted according to the shape of the tablet, a second approximation line closer to the main surface of the tablet can be calculated.

According to the fourth aspect of the tablet inspection method, it is possible to calculate a first approximation line that is closer to the shape of the boundary between the main surface and the side surface in the captured image.

According to the fifth aspect of the tablet inspection method, even if a score line is formed on the main surface of the tablet, it is possible to avoid erroneous detection of the edge corresponding to the score line as the boundary edge.

According to the sixth aspect of the tablet inspection method, the chipping of the tablet generated on the peripheral edge of the first main surface can be detected.

According to the seventh aspect of the tablet inspection method, the chipping of the tablet generated on the peripheral edge of the second main surface can be detected.

It is a figure which shows the example of the structure of the tablet inspection apparatus schematically. It is a perspective view which shows an example of a tablet. It is a figure which shows typically an example of the internal structure of an image pickup head. It is a figure which shows typically an example of the internal structure of an image pickup head. It is a figure which shows the example of the captured image schematically. It is a figure which shows the example of the captured image schematically. It is a flowchart which shows an example of the operation of a tablet inspection apparatus. It is a figure which shows typically an example of the tablet edge corresponding to the outer periphery of a tablet in the captured image. It is a figure for demonstrating an example of the method of specifying the boundary edge corresponding to the boundary between the main surface and the side surface of a tablet in the captured image. It is a flowchart which shows an example of the method of specifying a boundary edge. It is a figure which shows the example of various edges and their approximate lines schematically. It is a flowchart which shows an example of an inspection process. It is a flowchart which shows a more specific example of an inspection process. It is a flowchart which shows the more specific example of an inspection process. It is a flowchart which shows another example of the method of specifying a boundary edge. It is a figure for demonstrating another example of the method of specifying a boundary edge. It is a figure which shows the other example of various edges and their approximate lines schematically. It is a figure which shows the other example of various edges and their approximate lines schematically.

Hereinafter, embodiments will be described in detail with reference to the drawings. In the drawings, the dimensions and numbers of each part are exaggerated or simplified as necessary for the purpose of easy understanding. In the drawings, the same reference numerals are given to the parts having the same configuration and function, and the duplicate description is omitted in the following description. Further, in each figure, in order to clarify the directional relationship of the components, an XYZ Cartesian coordinate system with the Z-axis direction as the vertical direction and the XY plane as the horizontal plane is appropriately attached.

FIG. 1 is a diagram schematically showing an example of the configuration of the tablet printing apparatus 10. The tablet printing apparatus 10 includes a tablet inspection apparatus 1 and a printing head 6.

The tablet inspection device 1 is a device for inspecting the appearance of the tablet 9. FIG. 2 is a perspective view schematically showing an example of tablet 9. In the example of FIG. 2, the tablet 9 has a substantially disk shape. Specifically, the tablet 9 includes a pair of main surfaces 9a and 9b and side surfaces 9c. The main surfaces 9a and 9b have substantially the same circular shape in a plan view. One and the other of the main surfaces 9a and 9b may be referred to as a front surface and a back surface, respectively, and may also be referred to as an upper surface and a lower surface, respectively.

The main surface 9a and the side surface 9c of the tablet 9 are connected to each other while forming a corner portion, and the main surface 9b and the side surface 9c are also connected to each other while forming a corner portion. The diameter of the tablet 9 is set to, for example, about 5 [mm] to about 10 to several [mm], and the thickness thereof can be set to, for example, about 5 [mm] or less.

As illustrated in FIG. 2, a score line 91 may be formed on the main surface 9a of the tablet 9. The secant 91 is a groove extending linearly from one end of the main surface 9a to the other through the center of the main surface 9a. Further, a similar score line may be formed on the main surface 9b.

With reference to FIG. 1, the tablet inspection device 1 includes a hopper 2, a transfer drum 3, a transfer unit 4, an image pickup head 5, a sorting unit 7, and a control unit 8.

The hopper 2 is a charging unit for charging the tablet 9 into the tablet printing device 10. The hopper 2 is provided on the upper side of the ceiling of the housing (not shown) of the tablet printing apparatus 10. The tablet 9 charged from the hopper 2 is guided to the transport drum 3. The elements other than the hopper 2 are provided inside the housing of the tablet printing apparatus 10.

The transport drum 3 has a substantially columnar shape, and its central axis is arranged in a posture along the Y-axis direction. The transport drum 3 is rotated counterclockwise on the paper of FIG. 1 with the central axis as the center of rotation by a rotary drive motor (not shown). This rotary drive motor is controlled by, for example, the control unit 8.

A plurality of suction holes (not shown) are formed side by side along the circumferential direction on the outer peripheral surface of the transport drum 3. Each of the plurality of suction holes communicates with a suction mechanism (not shown) provided inside the transport drum 3. This suction mechanism is controlled by, for example, the control unit 8. By activating this suction mechanism, a negative pressure lower than the atmospheric pressure can be applied to each of the plurality of suction holes. As a result, each suction hole of the transport drum 3 can suck and hold one tablet 9.

The transport unit 4 is arranged below the transport drum 3. The tablet 9 adsorbed and held on the outer peripheral surface of the transport drum 3 moves in the circumferential direction as the transport drum 3 rotates. When the tablet 9 moves to the lower side of the transport drum 3, the suction mechanism releases the adsorption to the tablet 9, so that the tablet 9 falls and is delivered to the transport unit 4.

The transport unit 4 transports the tablets 9. In the example of FIG. 1, the transport unit 4 is a belt conveyor and includes a transport belt 41 and a pair of pulleys 42. The pair of pulleys 42 are arranged at intervals in the X-axis direction, for example, and their central axes are arranged in a posture along the Y-axis direction. Each of the pair of pulleys 42 rotates with its own central axis as the center of rotation.

The transport belt 41 is hung on a pair of pulleys 42. When at least one of the pair of pulleys 42 is rotationally driven by a drive motor (not shown), the conveyor belt 41 rotates in the direction indicated by the arrow in FIG. This drive motor is controlled by, for example, the control unit 8.

On the outer peripheral surface of the transport belt 41, a plurality of suction holes (not shown) are formed side by side along the circumferential direction thereof. Each of the plurality of suction holes communicates with a suction mechanism (not shown) provided inside the transport belt 41. This suction mechanism is controlled by, for example, the control unit 8. By activating this suction mechanism, a negative pressure lower than the atmospheric pressure can be applied to each of the plurality of suction holes. As a result, each suction hole of the transport belt 41 can suck and hold one tablet 9.

As the transport belt 41 rotates while sucking and holding the tablet 9, the tablet 9 is transported in the direction away from the transport drum 3 along the X-axis direction.

The image pickup head 5 is arranged at a position facing the transport unit 4 on the downstream side of the transport drum 3 in the middle of the transport path of the tablet 9 by the transport unit 4. The imaging area of the imaging head 5 includes a part of the transport belt 41. The image pickup head 5 takes an image of the tablet 9 as the tablet 9 moves in the image pickup area, and generates an image to be captured. The image pickup head 5 outputs this captured image to the control unit 8. An example of a specific internal configuration of the image pickup head 5 will be described in detail later.

The control unit 8 inspects the appearance of the tablet 9 by performing image processing on the input captured image. If the appearance of the tablet 9 is defective, the control unit 8 determines that the tablet 9 is a defective product, and if the appearance of the tablet 9 is not defective, the control unit 8 determines that the tablet 9 is a non-defective product. As the defect, a defect such as an impurity adhering to the tablet 9 or a defect (for example, chipping) in the shape of the tablet 9 can be exemplified. An example of specific image processing by the control unit 8 will be described in detail later.

The print head 6 is arranged on the downstream side of the image pickup head 5 and above the transfer belt 41 during the transfer of the tablet 9. The print head 6 is controlled by, for example, the control unit 8 to perform a printing process on the tablet 9. The print head 6 includes a plurality of ejection nozzles (not shown), and ejects ink droplets from each ejection nozzle by an inkjet method. The inkjet method may be a piezo method in which a voltage is applied to a piezo element (piezoelectric element) to deform it and eject ink droplets, or an ink droplet is generated by energizing a heater to heat the ink. It may be a thermal method that discharges ink. In the present embodiment, since the tablet 9 is printed, an edible ink manufactured from a raw material approved by the Food Sanitation Law is used as the ink.

In the example of FIG. 1, since the print head 6 is located on the downstream side of the transport path with respect to the image pickup head 5, the control unit 8 may determine the necessity of the print process according to the inspection result of the tablet 9. .. More specifically, when the tablet 9 is determined to be a non-defective product in the visual inspection, the control unit 8 controls the print head 6 so as to perform a printing process on the tablet 9, and determines that the tablet 9 is a defective product. If this is the case, the print head 6 may be controlled so that the tablet 9 is not printed. According to this, unnecessary printing processing can be avoided.

The sorting unit 7 sorts the tablets 9 according to the result of the visual inspection. For example, the sorting unit 7 has a non-defective product box and a defective product box. These boxes have a box-like shape that opens upward. The non-defective product box contains the tablets 9 determined to be non-defective products, and the defective product box contains the tablets 9 determined to be defective products. For example, these boxes are arranged side by side along the X-axis direction on the lower side of the transport belt 41. When the tablet 9 determined to be a non-defective product is located directly above the opening of the non-defective product box, the control unit 8 controls the suction mechanism in the transport belt 41 to release the adsorption to the tablet 9. As a result, the tablet 9 falls into the inside of the good product box and is housed in the good product box. Similarly, the tablet 9 determined to be a defective product is housed inside the defective product box.

The control unit 8 controls various components as described above, and also performs image processing on the image captured image input from the image pickup head 5 to perform an appearance inspection of the tablet 9.

The control unit 8 is an electronic circuit device, and may include, for example, a data processing device and a storage medium. The data processing device may be, for example, an arithmetic processing unit such as a CPU (Central Processor Unit). The storage unit may have a non-temporary storage medium (for example, ROM (Read Only Memory) or hard disk) and a temporary storage medium (for example, RAM (Random Access Memory)). For example, a program that defines a process executed by the control unit 8 may be stored in the non-temporary storage medium. When the processing device executes this program, the control unit 8 can execute the processing specified in the program. Of course, a part or all of the processing executed by the control unit 8 may be executed by the hardware.

<Image pickup head>
The image pickup head 5 takes an image of the tablet 9 in the process of being conveyed from the direction in which at least two surfaces of the tablet 9 are captured. The tablet 9 may be sucked and held by the transport belt 41 with its main surface 9b facing the transport belt 41 side, or by suction and holding by the transport belt 41 with its main surface 9a facing the transport belt 41 side. It may be done. In the following, for convenience of explanation, it is assumed that the main surface 9b of the tablet 9 is held by the transport belt 41 in a posture in which the main surface 9b faces the transport belt 41 side. Further, in a state where the tablet 9 is adsorbed and held by the transport belt 41, at least a part of the side surface 9c on the main surface 9a side is exposed from the transport belt 41.

The image pickup head 5 images the tablet 9 from the direction in which both the main surface 9a and the side surface 9c of the tablet 9 are captured. This produces an image in which both the main surface 9a and the side surface 9c of the tablet 9 are captured. 3 and 4 are diagrams schematically showing an example of the internal configuration of the image pickup head 5. For example, the image pickup head 5 includes an inspection camera 51, a lens group 52, a mirror 53, and a pyramid-shaped mirror 54. The inspection camera 51 is an image sensor such as a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor. The inspection camera 51 is arranged at a position facing a part of the transport path of the tablet 9 in the Z-axis direction so that its imaging surface faces the transport belt 41 side.

The mirror 53 is provided to guide the light from the main surface 9a and the side surface 9c of the tablet 9 to the pyramidal mirror 54 described later. In explaining the position of the mirror 53, for convenience, it is assumed that the tablet 9 is stopped at a position facing the inspection camera 51 in the Z-axis direction. With reference to FIG. 3, the mirror 53 is located between the inspection camera 51 and the tablet 9 in the Z-axis direction and is located outside the tablet 9 in plan view (ie, along the Z-axis direction). Has been done. Further, the mirror 53 is arranged so as to face each surface of the pyramid-shaped mirror 54.

The pyramidal mirror 54 guides the light reflected by the mirror 53 from the main surface 9a and the side surface 9c of the tablet 9 to the image pickup surface of the inspection camera 51 via the lens group 52. The pyramid-shaped mirror 54 is composed of four mirrors, and the pyramid-shaped mirror 54 is arranged so as to face each mirror 53.

A part of the light reflected or scattered on the main surface 9a and the side surface 9c of the tablet 9 travels diagonally upward toward one of the mirrors 53, is reflected by the mirror 53, and the light reflected by the mirror 53 is a prismatic shape. After being reflected by the mirror 54, an image is formed on the image pickup surface of the inspection camera 51 via the lens group 52. In other words, the angles of the reflective surfaces of the mirror 53 and the pyramidal mirror 54 with respect to the ground are adjusted so that the light traveling diagonally upward from the main surface 9a and the side surface 9c of the tablet 9 can be reflected toward the imaging surface of the inspection camera 51. Has been done.

As a result, the inspection camera 51 can capture the appearance of the tablet 9 as seen from the mirror 53. That is, the inspection camera 51 can substantially image the tablet 9 from an oblique direction, and the captured image includes both the main surface 9a and the side surface 9c of the tablet 9. In FIG. 3, an example of the light path is shown by a broken line.

In the example of FIG. 4, a plurality of mirrors 53 (four in the figure) are arranged. For example, the two mirrors 53 are arranged at intervals in the X-axis direction, and the remaining two mirrors 53 are arranged at intervals in the Y-axis direction. According to this, the tablet 9 is surrounded on all sides by the mirror 53 in a plan view. Further, pyramid-shaped mirrors 54 are arranged at intervals in the center of each mirror 53. The light reflected by each mirror 53 is further reflected by the pyramid-shaped mirror 54, and is imaged on the image pickup surface of the inspection camera 51 via the lens group 52. Specifically, the light reflected by the four mirrors 53 is imaged in different regions of the imaging surface of the inspection camera 51. As a result, the image pickup head 5 images the tablet 9 from four directions and generates an image taken including the appearance of the tablet 9 seen from the four directions.

FIG. 5 is a diagram schematically showing an example of the captured image IM1. The captured image IM1 includes the appearance of the tablet 9 as viewed from four directions, and in any of these, the main surface 9a and the side surface 9c of the tablet 9 are shown. Here, since the tablet 9 is imaged from four directions, the side surface 9c of the tablet 9 can be imaged over the entire circumference. Hereinafter, the main surface 9a and the side surface 9c of the tablet 9 shown in the captured image IM1 are referred to as the main surface 9aa and the side surface 9ca, respectively, in order to distinguish them from the main surface 9a and the side surface 9c of the actual tablet 9.

The image pickup head 5 may have a light source for illumination (not shown). This illumination light source irradiates the tablet 9 with light. Thereby, the brightness of the tablet 9 in the captured image IM1 can be improved.

Further, in the examples of FIGS. 3 and 4, although the light path is bent by the mirror 53 and the pyramid-shaped mirror 54, the present invention is not necessarily limited to this. As an element that bends the path of light, another optical element such as a prism may be adopted.

<Inspection>
The control unit 8 performs image processing on the image captured image IM1 input from the image pickup head 5 and inspects the appearance of the imaged tablet 9. Therefore, the control unit 8 functions as an image processing unit.

In the following, for the sake of simplicity, the appearance of the tablet 9 when viewed from one direction will be described. FIG. 6 is a diagram schematically showing an example of an image captured image IM11 obtained by photographing a defective tablet 9 from one direction. In the example of FIG. 6, the missing B1 is present at the boundary between the main surface 9aa and the side surface 9ca of the tablet 9.

The control unit 8 performs image processing on the captured image IM 11 to detect the missing B1 of the tablet 9. Hereinafter, a more specific description will be given.

FIG. 7 is a flowchart showing an example of the operation in the tablet inspection device 1. First, in step S1, the imaging head 5 images the tablet 9 in the process of being transported from the direction in which both the main surface 9a and the side surface 9c of the tablet 9 are captured, and the captured image in which both the main surface 9a and the side surface 9c of the tablet 9 are captured. Generate IM11. The image pickup head 5 outputs the captured image IM 11 to the control unit 8.

Next, the control unit 8 detects the main surface edge corresponding to the contour of the main surface region Ra occupied by the main surface 9aa of the tablet 9 in the captured image IM11. As shown in FIG. 6, when the chip B1 occurs at the boundary between the main surface region Ra and the side surface region Rc, the main surface edge is an edge corresponding to the contour of the main surface 9aa including the chip B1. Know that there is. The detection of the main surface edge is executed, for example, by a series of processes of steps S2 to S5 in FIG.

First, in step S2, the control unit 8 performs edge detection processing on the captured image IM 11 to generate an edge image. However, here, the control unit 8 performs edge detection processing on the captured image IM11 from which the background region BR is deleted. The background region BR is a region other than the tablet region TR occupied by the tablet 9 in the captured image IM11. This tablet region TR is composed of a main surface region Ra and a side surface region Rc.

In order to delete the background region BR, the control unit 8 first distinguishes between the tablet region TR and the background region BR of the captured image IM11. For example, the control unit 8 distinguishes between the tablet region TR and the background region BR by using the binarization process for the captured image IM11. Since the background region BR includes the transport belt 41, in order to accurately distinguish between the tablet region TR and the background region BR, the contrast between the actual color of the transport belt 41 and the color of the tablet 9 is increased. good. For example, when the tablet 9 is white, the transport belt 41 is black. When the control unit 8 specifies the background area BR, the control unit 8 deletes the background area BR in the captured image IM11. For example, the control unit 8 deletes the background area BR by setting the pixel values of all the pixels in the background area BR to zero.

Next, the control unit 8 performs edge detection processing on the captured image IM11 from which the background region BR has been deleted to generate an edge image. Although the specific processing method of the edge detection processing does not need to be particularly limited, an example thereof will be briefly described. For example, the control unit 8 performs edge strength processing on the captured image IM11 after removal to generate an edge strength image. The edge strength processing includes, for example, a calculation process of a difference in pixel values between pixels, whereby a region having a large difference in pixel values between pixels in the captured image IM 11 becomes an edge strength image. In this edge intensity image, the control unit 8 determines for each pixel whether or not the pixel value is larger than a predetermined edge threshold value. The edge threshold value may be set in advance and stored in the storage medium of the control unit 8, for example. The control unit 8 detects a pixel having a pixel value larger than the edge threshold value and generates an edge image.

Since this edge image is generated based on the captured image IM11 from which the background region BR is removed, the edge in the background region BR (for example, the unevenness of the transport belt 41) is not detected in the edge image. That is, the edge corresponding to the contour of the tablet region TR (hereinafter referred to as the tablet edge) is located at the outermost circumference of the edge group in the edge image.

Therefore, in step S3, the control unit 8 specifies the tablet edge as follows. That is, the control unit 8 identifies the edge located on the outermost circumference of the edge group in the edge image as the tablet edge P0 (see FIG. 8).

FIG. 8 is a diagram schematically showing an example of the tablet edge P0. In the example of FIG. 8, the tablet edge P0 is schematically shown by being divided into a plurality of edges. The tablet edge P0 is composed of a side surface outer edge P1, a main surface outer edge P2, and a pair of side ridge edge P4. The side surface outer edge P1 is an edge corresponding to the portion of the peripheral edge of the main surface 9b of the tablet 9 that is reflected in the captured image IM11. Since the main surface 9b has a circular shape, the side surface outer edge P1 ideally has a semi-elliptical shape. The semi-elliptical shape referred to here is a shape obtained by dividing an ellipse into two on its long axis.

The main surface outer edge P2 is an edge corresponding to a portion of the peripheral edge of the main surface 9aa of the tablet 9 that is not in contact with the side surface 9ca in the captured image IM11. It can be said that the outer edge P2 of the main surface corresponds to a part of the contour of the tablet region TR in the peripheral edge of the main surface 9aa of the tablet 9. Since the main surface 9a has a circular shape, the outer edge P2 of the main surface ideally has a semi-elliptical shape. More specifically, the side surface outer edge P1 and the main surface outer edge P2 have a semi-elliptical shape that bulges on opposite sides to each other.

The pair of side surface ridge edges P4 ideally extend linearly, and both ends of the main surface outer edge P2 are connected to both ends of the side surface outer edge P1. The pair of side ridge edges P4 are edges corresponding to a part of the contour of the side surface 9ca of the tablet 9 in the captured image IM11. The pair of side ridge edges P4 extend substantially in parallel, and the extending direction thereof is predetermined by the arrangement of the internal configuration of the image pickup head 5. Here, it is assumed that the side ridge line edge P4 extends in a direction intersecting the lateral direction in the captured image IM11 at approximately 45 degrees.

It should be noted that the pair of side ridge edges P4 are not actually perfectly parallel. The pair of side ridge edges P4 are slightly inclined so as to approach each other toward the side outer edge P1 side. In the following, for the sake of simplicity, it is assumed that the pair of side ridge edges P4 are parallel. If considered more strictly, the extending direction of the side ridge edge P4 described below may be understood as the direction represented by the bisector of the extending direction of the pair of side ridge edges P4.

With reference to FIG. 7 again, in step S4, the control unit 8 extracts the side surface outer edge P1 and the main surface outer edge P2 from the tablet edge P0 specified in step S3. For example, the control unit 8 specifies the edge of the tablet edge P0 extending along the predetermined direction D1 (= extending direction of the side surface ridge line edge P4) as the side surface ridge line edge P4. Then, the control unit 8 identifies one of the two edges on the predetermined side (upper right side in the figure) as the side surface outer edge P1 among the two edges excluding the side ridge line edge P4 from the tablet edge P0, and the other is the main surface outer edge P2. To specify.

Next, in step S5, the control unit 8 identifies the boundary edge P3 from the edge image. The boundary edge P3 is an edge corresponding to the boundary between the main surface 9aa and the side surface 9ca of the tablet 9 in the captured image IM11. In other words, the boundary edge P3 is an edge corresponding to the boundary between the main surface region Ra and the side surface region Rc. As shown in FIG. 6, when the chip B1 is present, the boundary edge P3 includes a part of the edge corresponding to the contour of the chip B1. A specific example of the boundary edge P3 will be described later.

In the absence of chipping B1 in tablet 9, the boundary edge P3 ideally has a semi-elliptical shape that bulges opposite to the outer edge P2 of the main surface. That is, the boundary edge P3 has the same shape as the side surface outer edge P1. Further, since the tablet 9 is not so thick here, it can be considered that the boundary edge P3 and the side surface outer edge P1 have substantially the same shape if the tablet 9 is not chipped and B1 is not generated. That is, the boundary edge P3 exists in a region in which the side surface outer edge P1 is translated along the predetermined direction D1 toward the main surface outer edge P2 by the length of the side surface ridge line edge P4. Since the length of the side ridge edge P4 is predetermined according to the thickness of the tablet 9 and the arrangement of the internal configuration of the image pickup head 5, if the side outer edge P1 is specified, the region where the boundary edge P3 exists is estimated. be able to.

Therefore, the control unit 8 searches for pixels in the search region R1 (see also FIG. 9) separated by a predetermined distance from the side surface outer edge P1 toward the main surface outer edge P2 along the predetermined direction D1 to obtain the boundary edge P3. Identify. FIG. 9 is a diagram schematically showing an example of the search region R1. In explaining an example of the search area R1, the center line L0 of the search area R1 and the lines L1 to L4 forming the contour of the search area R1 are introduced.

The center line L0 is a line obtained by moving the side surface outer edge P1 toward the main surface outer edge P2 along the predetermined direction D1 by the length of the side surface ridge line edge P4. Further, in the example of FIG. 9, although a part of the boundary edge P3 and a part of the center line L0 are shown to coincide with each other, they may actually be different from each other.

The lines L1 and L2 are lines in which the center line L0 is moved along the predetermined direction D1 to the opposite sides by a predetermined width. This predetermined width is preset according to the assumed size of the chipped B1. In FIG. 9, line L1 is closer to the side outer edge P1 than line L2. The lines L3 and L4 extend along the predetermined direction D1 and connect both ends of the lines L1 and L2, respectively. The search region R1 is a region surrounded by a set of these lines L1 to L4.

Note that FIG. 9 also shows a chipped edge P'corresponding to the contour of the chipped B1 and a part of the secant edge P5 corresponding to the secant 91. Further, in the following, for convenience of explanation, the pixel group arranged along the predetermined direction D1 in the search area R1 is referred to as a “row”.

FIG. 10 is a flowchart showing an example of the search process of the control unit 8. First, in step S51, the control unit 8 initializes the values N and M to 1, respectively. The value N indicates the number of the row in the search area R1, and the value M indicates the number of the pixel belonging to the row. The first pixel is a pixel on the line L1, and the Mth pixel is a pixel next to the (M-1) th pixel in each row.

Next, in step S52, the control unit 8 determines whether or not the Nth row and Mth pixel in the search area R1 of the edge image indicates an edge. When a negative determination is made, in step S53, the control unit 8 adds 1 to the value M to update the value M, and executes step S52 again using the updated value M. That is, if a pixel indicating an edge (hereinafter, also referred to as an edge pixel) cannot be detected, the same determination is made for the next pixel.

When a positive determination is made in step S52, in step S54, the control unit 8 grasps the pixel as a component of the boundary edge P3. Next, in step S55, the control unit 8 adds 1 to the value N to update the value N, and initializes the value M to 1. Next, in step S56, the control unit 8 determines whether or not the value N is larger than the reference value Nref. The reference value Nref is the total number of rows included in the search area R1. That is, the control unit 8 determines whether or not all the rows have been searched. When it is determined that all the rows have not been searched, the control unit 8 executes step S52 again. When it is determined that all the rows have been searched, the control unit 8 ends the search process.

As described above, the control unit 8 sequentially selects pixels from the line L1 in each row in the search area R1, and specifies the first detected edge pixel as a component of the boundary edge P3. In the example of FIG. 9, the search direction of the pixel is schematically indicated by a solid arrow in the search area R1, and the end point of the arrow indicates a component of the boundary edge P3. According to this search process, the pixels on the chipped edge P'are identified as the components of the boundary edge P3 as follows. That is, the pixel on the edge Pc'on the line L1 side (that is, the side surface outer edge P1 side) of the chipped edge P'is specified as a component of the boundary edge P3. In FIG. 9, some of the pixels identified as the components of the boundary edge P3 are schematically indicated by black circles.

Further, according to the above-mentioned search process, the pixel on the secant edge P5 is not specified as a component of the boundary edge P3. This is because the secant edge P5 is located on the outer edge P2 side of the main surface with respect to the boundary edge P3, and the control unit 8 moves the search area R1 from the line L1 side to the line L2 side (that is, from the outer side edge P1 to the main surface). This is because the search is performed (to the outer edge P2 side). That is, according to this search process, the control unit 8 can specify the component of the boundary edge P3 before searching for the pixel of the secant edge P5.

The control unit 8 specifies a set of the main surface outer edge P2 specified in step S4 and the boundary edge P3 specified in step S5 as the main surface edge P23. When the chip B1 is generated, the main surface edge P23 does not have an ideal elliptical shape and deviates from the ideal elliptical shape in the portion corresponding to the chip B1 (see also FIG. 11 described later). ). Therefore, if an approximate line close to this ideal ellipse is calculated, the chipping B1 can be detected based on the portion where the approximate line and the main surface edge P23 deviate from each other.

Therefore, in step S6, the control unit 8 calculates an approximate line (ellipse) that approximates the main surface edge P23 based on the function of the ellipse. More generally, the control unit 8 calculates an approximate line of the main surface edge P23 based on a reference function predetermined as the shape of the contour of the main surface region Ra in the captured image IM11. The reference function referred to here is a function representing the shape of the contour of the main surface region Ra when the tablet 9 is not defective, and the position and size thereof are variables. If it is an elliptic function, for example, the length of the major axis, the length of the minor axis, the extending direction of the major axis, the center, and the like can be adopted as variables. The control unit 8 calculates an ellipse E1 (more specifically, the length of the major axis, the length of the minor axis, the extending direction and the center of the major axis) that approximates the main surface edge P23 by the least squares method.

As described above, since the approximate line of the main surface edge P23 is calculated based on the reference function indicating the contour of the main surface region Ra, this approximate line is close to the contour of the main surface region Ra. Further, in the above-mentioned specific example, the tablet 9 has a substantially disk shape. That is, the main surface 9a of the tablet 9 has a substantially circular shape. Therefore, in the captured image IM11, the peripheral edge of the main surface 9aa ideally has an elliptical shape. Correspondingly, in this embodiment, an elliptic function is used as a reference function. Therefore, it is possible to appropriately calculate an approximate line close to the contour of the main surface region Ra.

In the following, of the two semi-ellipses obtained by dividing the ellipse E1 along its long axis, the semi-ellipse on the main surface 9aa side and the semi-ellipse on the side surface 9ca side are also referred to as semi-ellipses E11 and E12, respectively. The semi-ellipses E11 and E12 correspond to the approximate lines of the outer edge P2 of the main surface and the boundary edge P3, respectively.

Next, in step S7, the control unit 8 calculates an approximate line (semi-ellipse) that approximates the side surface outer edge P1 based on the ellipse E1. For example, the control unit 8 calculates the ellipse E2 along the side outer edge P1 by using the Levenberg-Marquardt (LM) method while moving the ellipse E1 along the predetermined direction D1. This ellipse E2 corresponds to the peripheral edge of the main surface 9b of the tablet 9. Therefore, the control unit 8 divides the ellipse E2 along its major axis, and finds the semi-ellipse E21 farther from the boundary edge P3 as an approximate line of the side outer edge P1 among the two obtained semi-ellipses.

The control unit 8 may reduce the ellipse E1 by a predetermined ratio when calculating the ellipse E2. This is because in a perspective view such as the captured image IM11, the peripheral edge of the main surface 9b of the tablet 9 is smaller than the peripheral edge of the main surface 9a of the tablet 9 at a predetermined ratio. This predetermined ratio is preset according to the thickness of the tablet 9.

The control unit 8 does not necessarily calculate the ellipse E2 based on the ellipse E1, and does not necessarily have to calculate the semi-ellipse E21 from the ellipse E2. For example, the control unit 8 may obtain the semi-ellipse E12 from the ellipse E1 and calculate the semi-ellipse E21 by using the LM method while moving the semi-ellipse E12 along the predetermined direction D1. Further, in calculating the semi-ellipse E21, the semi-ellipse E12 may be reduced by a predetermined ratio.

FIG. 11 is a diagram schematically showing an example of various edges and their approximate lines for the tablet 9 in which the chipped B1 is generated. The main surface edge P23 extends along the portion of the contour of the chip B1 on the side surface 9ca side and the peripheral edge of the main surface 9aa. In the example of FIG. 11, although the side surface outer edge P1 and the semi-ellipse E21 which is an approximate line thereof are shown to coincide with each other, they may actually differ from each other.

Next, in step S8, the control unit 8 executes the inspection process. This inspection process is a process for detecting chips generated on the peripheral edges of the main surfaces 9a and 9b of the tablet 9. FIG. 12 is a flowchart showing a specific example of this inspection process. First, in step S81, the control unit 8 extracts the semi-ellipses E11 and E12, which are the approximate lines of the main surface outer edge P2 and the boundary edge P3, from the ellipse E1 which is the approximate line of the main surface edge P23, respectively. Specifically, the control unit 8 calculates the semi-ellipse obtained by dividing the ellipse E1 along its long axis as the semi-ellipses E11 and E12, respectively.

Next, in step S82, the control unit 8 has a distance d (also referred to in FIG. 11) between each pixel on the boundary edge P3 and the semi-ellipse E12, which is larger than a predetermined threshold value (hereinafter referred to as a distance threshold value) dth. Determine if it is long. The distance threshold value dth may be set in advance and stored in the storage medium of the control unit 8, for example. In the example of FIG. 11, the distance d between a pixel on the boundary edge P3 and the semi-ellipse E12 is shown. When a positive judgment is made in step S82, in step S83, the control unit 8 controls the peripheral edge of the main surface 9a of the tablet 9 (more specifically, the boundary between the main surface 9aa and the side surface 9ca in the captured image IM11). ) Is judged to be missing. When a negative judgment is made, the control unit 8 does not execute step S83.

FIG. 13 is a flowchart showing a more specific example of the processing of steps S82 and S83. First, in step S801, the control unit 8 initializes the value n to 1. The value n is a number indicating a pixel on the boundary edge P3. Each pixel on the boundary edge P3 is assigned a continuous number in order from one end to the other end.

Next, in step S802, the control unit 8 calculates the distance d between the nth pixel (hereinafter referred to as a pixel of interest) on the boundary edge P3 and the semi-ellipse E12. For example, the control unit 8 calculates the distance between the pixel of interest and each of the pixels on the semi-ellipse E12, and selects the smallest value as the distance d.

Next, in step S803, the control unit 8 determines whether or not the distance d is longer than the distance threshold value dth. When a positive judgment is made, in step S804, the control unit 8 determines that the pixel of interest is a pixel showing the outline of the chip, and determines that the peripheral edge of the main surface 9a of the tablet 9 has a defect. do. Next, the control unit 8 executes step S805 described later. On the other hand, when a negative determination is made, the control unit 8 executes step S805 without executing step S804.

In step S805, the control unit 8 adds 1 to the value n and updates the value n. Next, in step S806, the control unit 8 determines whether or not the value n is larger than the reference value nref. The reference value nref is the total number of pixels constituting the boundary edge P3. That is, it is determined whether or not the determination is completed for all the pixels on the boundary edge P3. When a negative determination is made in step S806, the determination has not been completed for all the pixels, so the control unit 8 executes step S802 again. On the other hand, when a positive determination is made in step S806, the control unit 8 ends the process.

In the above example, the above determination is made for all the pixels on the boundary edge P3. However, when it is not necessary to detect the number of chips and their positions, the above determination for the remaining pixels may be omitted when one pixel showing the outline of the chip is detected. This point is the same for all the inspection processes described below.

With reference to FIG. 12 again, in step S84, the control unit 8 determines whether or not the distance between each pixel on the outer edge P2 of the main surface and the semi-ellipse E11 which is an approximate line thereof is longer than the distance threshold value dth. to decide. When a positive judgment is made, in step S85, the control unit 8 has a chip on the peripheral edge of the main surface 9a of the tablet 9 (more specifically, the portion of the captured image IM 11 that is not in contact with the side surface 9ca). Judge. When a negative judgment is made, the control unit 8 does not execute step S85.

Next, in step S86, the control unit 8 determines whether or not the distance between each pixel on the side surface outer edge P1 and the semi-ellipse E21 which is an approximate line thereof is longer than the distance threshold value dth. When a positive judgment is made, in step S87, the control unit 8 determines that the peripheral edge of the main surface 9b of the tablet 9 (more specifically, the portion shown in the captured image IM11) is chipped. .. When a negative judgment is made, the control unit 8 does not execute step S87.

An example of the specific method of steps S84 and S85 and an example of the specific method of steps S86 and S87 are the same as the specific method of steps S82 and S83.

As described above, according to the tablet inspection device 1, it is possible to detect chips generated on the peripheral edges of the main surfaces 9a and 9b of the tablet 9.

The execution order of the set of steps S82 and S83, the set of steps S84 and S85, and the set of steps S86 and S87 may be changed as appropriate. Further, when it is not necessary to detect the number and position of chips, the control unit 8 does not necessarily have to execute all the determinations of steps S82, S84, and S86. When a positive judgment is made in any one of the control units 8, the remaining judgment may be omitted.

Further, in the above example, the control unit 8 calculated an approximate line (ellipse E1) approximated to the main surface edge P23, and extracted the semi-ellipses E11 and E12 from the ellipse E1. However, the control unit 8 calculates an approximate line (semi-elliptical E12) of the boundary edge P3 based on a reference function predetermined as the shape of the boundary between the main surface 9aa and the side surface 9ca of the tablet 9 in the captured image IM11. You may. Similarly, the control unit 8 has an approximate line (approximate line) of the outer edge P2 of the main surface based on a reference function predetermined as the shape of the portion of the peripheral edge of the main surface 9aa of the tablet 9 that is not in contact with the side surface 9ca in the captured image IM11. The semi-ellipse E11) may be calculated.

<Inspection processing>
In the above example, for example, when the distance d between one pixel on the boundary edge P3 and the semi-ellipse E12 is longer than the distance threshold value dth, the control unit 8 determines that the pixel shows the contour of the chip (. Steps S802-S804). That is, when the one pixel is separated from the semi-ellipse E12 by a distance longer than the distance threshold value dth, it is determined that the pixel shows the outline of the chip. However, when the chipping B1 occurs, with reference to FIG. 11, a plurality of consecutive pixels on the boundary edge P3 are separated from the semi-ellipse E12 by a distance longer than the distance threshold value dth. That is, if only one pixel is separated from the semi-ellipse E12 by a distance longer than the distance threshold dth, that pixel may be noise rather than exhibiting missing B1. Therefore, here, it is suppressed that such noise is erroneously detected as a chip.

Specifically, the control unit 8 determines whether or not a plurality of pixels separated from the semi-ellipse E12 at a distance d longer than the distance threshold dth are continuous on the boundary edge P3, and when a positive judgment is made. In addition, it is determined that the group of continuous pixels shows the outline of the missing B1 and is located on the peripheral edge of the main surface 9a of the tablet 9 (more specifically, the boundary between the main surface 9aa and the side surface 9ca of the captured image IM11). It is determined that the chip B1 has occurred.

FIG. 14 is a flowchart showing an example of a specific method of such an inspection process. First, in step S811, the control unit 8 initializes the values n and m to 1,0, respectively. The value m indicates the number of pixels that are separated from the semi-ellipse E12 by a distance longer than the distance threshold value dth and are continuous on the boundary edge P3, as will be clear from the explanation below.

Next, the control unit 8 executes steps S812 and S813 in this order. Steps S812 and S813 are the same as steps S802 and S803, respectively. If a positive judgment is made in step S813, in step S814, the control unit 8 adds 1 to the value m to update the value m.

Next, in step S815, the control unit 8 adds 1 to the value n and updates the value n. Next, in step S816, the control unit 8 determines whether or not the value n is larger than the reference value nref. That is, the control unit 8 determines whether or not processing has been performed on all the pixels on the boundary edge P3. If a negative determination is made, the control unit 8 again executes step S812 in order to determine the next pixel. On the other hand, if a positive judgment is made, the control unit 8 ends the process.

If a negative determination is made in step S813, in step S817, the control unit 8 determines whether or not the value m is larger than the threshold value (hereinafter referred to as continuous threshold value) mth. The continuous threshold value mth may be set in advance and stored in the storage medium of the control unit 8, for example.

When a positive judgment is made in step S817, in step S818, the control unit 8 shows the outline of the chipping of a group of the (n-1) th pixels from the (n−m + 1) th pixel. It is determined that the main surface 9a is missing (more specifically, the boundary between the main surface 9aa and the side surface 9ca in the captured image IM11) and B1 is generated. Next, in step S819, the control unit 8 initializes the value m to 0 and executes step S815. If a negative determination is made in step S817, the control unit 8 executes step S819 without executing step S818.

According to this inspection process, the value m is initialized to zero when a pixel whose distance d is shorter than the distance threshold dth is detected (step S819), and pixels having a distance d longer than the distance threshold dth are consecutive. It is incremented each time it is detected (step S815). Therefore, the value m indicates the number of consecutive pixels whose distance d is longer than the distance threshold value dth. Then, when this value m is larger than the continuous threshold value mth, the control unit 8 determines that a chip has occurred (steps S817 and S818). As a result, it is possible to suppress erroneous detection of chipping and detect chipping with higher accuracy.

This inspection process is also applicable to the side surface outer edge P1 and the main surface outer edge P2.

<Boundary edge>
In the above example, in the search from the line L1 to the line L2 of each line of the search area R1, the first detected edge pixel is grasped as a component of the boundary edge P3 (see FIG. 9). Therefore, among the chipped edges P', the pixels on the edge Pc' on the line L1 side are adopted as the components of the boundary edge P3. Therefore, the components of the boundary edge P3 are biased toward the edge Pc'of the chipped edges P'. As a result, the ellipse E1 (a set of semi-ellipses E11 and E12) that approximates the main surface edge P23 tends to deviate from the contour of the main surface region Ra.

Here, it is intended to calculate an ellipse E1 that is closer to the contour of the main surface region Ra by devising a search method for the boundary edge P3. Specifically, paying attention to the distribution of the pixel values of the defect region in the captured image IM11, the components of the boundary edge P3 are the edge Pc'on the line L1 side and the edge Pa'on the line L2 side of the edge P'. It is intended to identify the boundary edge P3 so that it is dispersed.

By the way, the surface of the chipped tablet 9 is rougher than the surface roughness of the main surface 9a and the side surface 9c, and the luminance component in the defect region in the captured image IM11 is scattered. Therefore, the luminance component also varies even in the contour (edge P') of the defect region. Therefore, the pixel value on the edge Pa'in the captured image IM11 also varies in a certain range, and the pixel value on the edge Pc' also varies in the same range.

Therefore, the control unit 8 searches for pixels in the search area R1 of the edge image whose pixel value in the corresponding captured image IM 11 is larger than a predetermined threshold value (hereinafter referred to as a brightness threshold value). This brightness threshold is preset according to the brightness of the main surface 9aa of the tablet 9. For example, the brightness threshold is preset to a value within the above range. Such a brightness threshold can be set by, for example, simulation or experiment. The brightness threshold value may be stored in the storage medium of the control unit 8, for example. Hereinafter, an example of a specific operation will be described.

FIG. 15 is a flowchart showing an example of the search process by the control unit 8. Compared to FIG. 10, the control unit 8 further executes step S57. This step S57 is executed when a positive judgment is made in step S52. In step S57, the control unit 8 determines whether or not the pixel value of the Nth row Mth pixel in the search area R1 of the captured image IM 11 is larger than the brightness threshold value.

When a negative determination is made in step S57, the control unit 8 executes step S53, and when a positive determination is made, the control unit 8 executes step S54.

According to this, even if it is an edge pixel in the search area R1, if the pixel value of the pixel of the captured image IM11 corresponding to the edge pixel is smaller than the brightness threshold, the edge pixel is the boundary edge P3. When the pixel value of the pixel of the captured image IM11 is larger than the brightness threshold value, the edge image is grasped as the component of the boundary edge P3.

As a result, the pixels grasped as the constituent elements of the boundary edge P3 are dispersed on the edge P'. FIG. 16 is a diagram schematically showing an example of an edge in an edge image when the boundary between the main surface 9aa and the side surface 9ca of the tablet 9 is chipped. Also in the example of FIG. 16, some of the pixels grasped as the boundary edge P3 are schematically indicated by black circles. As illustrated in FIG. 16, the pixels are dispersed in the edges Pa'and Pc'of the edge P'. In other words, the brightness threshold is set so that the pixel grasped as the boundary edge P3 is not biased to only one side at the edge P'. As a more specific example, the brightness of the main surface 9aa of the tablet 9 (for example, the average value, the median value, the maximum value or the minimum value of the pixel value (or the brightness value), the same applies hereinafter) is the side surface 9ca of the tablet 9. When the brightness is higher than the brightness, the brightness of the main surface 9aa is adopted as the brightness threshold, and when the brightness of the main surface 9aa of the tablet 9 is lower than the brightness of the side surface 9ca of the tablet 9, the brightness is used. The brightness of the side surface 9ca is adopted as the threshold value.

The semi-ellipse E11 that approximates the boundary edge P3 becomes a semi-ellipse that is closer to the peripheral edge of the main surface 9aa of the tablet 9, and the ellipse E1 that approximates the main surface edge P23 is an ellipse that is closer to the peripheral edge of the main surface 9aa of the tablet 9. It becomes.

FIG. 17 is a diagram schematically showing an example of various edges and their approximate lines for the tablet 9 in which the chip B1 is generated. Since the components of the boundary edge P3 are dispersed in the edges Pa'and Pc'at the chipped edge P', in the example of FIG. 17, the component of the chipped edge P'is partially specified as a component of the boundary edge P3. To show, the chipped edge P'is shown by a broken line. Further, in the example of FIG. 17, the main surface outer edge P2 and the semi-ellipse E11 are shown to coincide with each other, and the side surface outer edge P1 and the semi-ellipse E21 are shown to coincide with each other. The boundary edge P3 is shown to coincide with the semi-ellipse E12 in the portion other than the chipped edge P'. In reality, these can be different from each other.

As can be understood from the comparison of FIGS. 11 and 17, the distance d between each pixel on the boundary edge P3 and the semi-ellipse E12 is calculated to be larger at the missing edge P'. Therefore, it is easier to detect the chipped B1. In other words, the missing B1 can be detected with higher accuracy.

Moreover, since the components of the boundary edge P3 are dispersed by the chipped edge P', the chipped B1 can be detected by using both the pixel on the edge Pa'and the pixel on the edge Pc'. As a result, even when the chipped B1 is formed unevenly toward the main surface 9aa, that is, when the edge Pc'does not project much toward the side surface 9ca and projects toward the main surface 9aa. Even if there is, the missing B1 can be detected. The details will be described below.

FIG. 18 is a diagram schematically showing an example of various edges and their approximate lines when the chip B1 does not project to the side surface 9ca side. When the chip B1 does not project so much toward the side surface 9ca, the distance d between each pixel on the edge Pc'and the semi-ellipse E12 becomes short. Then, depending on the shape of the chip B1, the distance d for all the pixels on the edge Pc'may be shorter than the distance threshold dth. At this time, if the search process of FIG. 9 is adopted and the components of the boundary edge P3 are biased toward the edge Pc', the chipped B1 cannot be detected in the subsequent inspection process.

On the other hand, if the chip B1 projects toward the main surface 9aa, the distance d between the pixel on the edge Pa'and the semi-ellipse E12 becomes longer than the distance threshold dth, as shown in FIG. Therefore, if the search process of FIG. 16 in which the components of the boundary edge P3 are dispersed in both the edges Pa'and Pc' is used, this chipping B1 can be detected in the subsequent inspection process. This is because, in this inspection process, the magnitude of the distance d and the distance threshold value dth between the pixel on the edge Pa'and the semi-ellipse E12 in the boundary edge P3 is determined (steps S82 and S83).

<Center line of search area>
In the above example, it has been described that the center line L0 of the search region R1 is a line obtained by moving the side surface outer edge P1, but the side surface outer edge P1 may be enlarged by a predetermined magnification during this movement. Strictly speaking, the boundary edge P3 is larger than the side surface outer edge P1 at a predetermined magnification.

Modification example.
<Main surface of tablets>
In the above-mentioned example, the tablet 9 transported in a posture in which the main surface 9b faces the transport belt 41 side is described as an inspection target. When the tablet 9 is transported with the main surface 9a of the tablet 9 facing the transport belt 41, the tablet inspection device 1 performs a visual inspection on the main surface 9b and the side surface 9c of the tablet 9.

Further, for example, after the visual inspection of the tablet 9, the transport posture of the tablet 9 may be reversed and the visual inspection of the tablet 9 may be performed in that state. According to this, it is possible to perform a visual inspection on the entire surface (main surfaces 9a, 9b and side surfaces 9c) of the tablet 9.

<Tablet shape>
In the above example, the tablet 9 had a substantially disk shape. For example, as this disk shape, a so-called flat lock or a lock with R can be adopted. However, the tablet 9 is not necessarily limited to the disk shape. That is, the main surfaces 9a and 9b do not necessarily have to have a circular shape. Since the shapes of the main surfaces 9a and 9b are known, the shape of the peripheral edge of the main surface 9a (or the main surface 9b) that will appear in the captured image IM11 can be determined in advance by the reference function. Although this reference function indicates the shape, its size and position are variables. The reference function may be stored in advance in the storage medium of the control unit 8, for example. The control unit 8 may generate an edge image from the captured image IM11 and obtain an approximate line of the main surface edge included in the edge image based on the reference function.

As described above, the tablet inspection method and the tablet inspection apparatus have been described in detail, but the above description is exemplary in all aspects, and the disclosure is not limited thereto. Further, the various modifications described above can be applied in combination as long as they do not contradict each other. And it is understood that a large number of modifications not exemplified can be assumed without departing from the scope of this disclosure.

1 Tablet inspection device 5 Imaging unit (imaging head)
8 Image processing unit (control unit)
9 Tablets 9a 1st main surface (main surface)
9b 2nd main surface (main surface)
9c Side surface E1 2nd approximation line (ellipse)
E11 3rd approximation line (semi-elliptical)
E12 1st approximation line (semi-elliptical)
E21 4th approximation line (semi-elliptical)
IM1 Captured image P0 Tablet edge P1 Side surface outer edge P2 Main surface outer edge P3 Boundary edge P23 Main surface edge R1 Search area Ra Main surface area Rc Side area TR Tablet area

Claims (8)

A tablet inspection method for inspecting the appearance of a tablet having a pair of first main surface and second main surface and side surface.
A step (a) of imaging a tablet to generate an captured image in which both the first main surface and the side surface are captured.
In the captured image, the boundary edge corresponding to the boundary between the main surface region and the side surface region occupied by the first main surface and the side surface of the tablet is specified, and the first approximation line approximate to the boundary edge is defined. The step (b) of calculating based on the function indicating the shape of the boundary in the captured image, and
A step (c) of determining that the peripheral edge of the first main surface of the tablet is chipped when the distance between each pixel on the boundary edge and the first approximation line is longer than a predetermined threshold value. ) And a tablet inspection method. The tablet inspection method according to claim 1.
The main surface region and the side surface region constitute a tablet region occupied by the tablet in the captured image.
The step (b) is
The step (b1) of generating an edge image by performing edge detection processing on the captured image, and
The step (b2) of specifying the tablet edge corresponding to the contour of the tablet region from the edge image,
The outer edge of the main surface and the outer edge of the side surface corresponding to the portion of the peripheral edge of the first main surface in the captured image that becomes a part of the contour of the tablet region and the peripheral edge of the second main surface in the captured image, respectively. In the step (b3) of extracting from the tablet edge and
In the edge image, a step (b4) of searching for pixels in a search region separated by a predetermined distance from the outer side edge in a predetermined direction to specify the boundary edge.
A step (b5) of calculating a second approximation line of a set of main surface edges of the outer edge of the main surface and the boundary edge based on a function indicating the shape of the contour of the main surface region in the captured image.
A tablet inspection method comprising a step (b6) of extracting the first approximation line of the boundary edge from the second approximation line. The tablet inspection method according to claim 2.
The tablet has a substantially disk shape and has a substantially disk shape.
The tablet inspection method, wherein the function is a function indicating an ellipse, and the second approximation line is an ellipse. The tablet inspection method according to claim 2 or 3.
In the step (b4),
A tablet inspection method for identifying a boundary edge by searching for a pixel in the search region of the edge image and having a pixel value of a pixel of the captured image corresponding to the pixel larger than a predetermined threshold value. The tablet inspection method according to claim 3 or 4.
In the step (b4),
A tablet inspection method for identifying the boundary edge by searching for pixels from the side surface outer edge toward the main surface outer edge in the search region. The tablet inspection method according to any one of claims 2 to 5.
A step of extracting a third approximation line of the outer edge of the main surface from the second approximation line of the main surface edge calculated in the step (b5), and a step of extracting the third approximation line of the outer edge of the main surface.
A step of determining that the peripheral edge of the first main surface of the tablet is chipped when the distance between each pixel on the outer edge of the main surface and the third approximation line is longer than a predetermined threshold value. A tablet inspection method that comprises. The tablet inspection method according to any one of claims 2 to 6.
A step of extracting a fourth approximation line of the side surface outer edge from the second approximation line of the main surface edge calculated in the step (b5), and a step of extracting the fourth approximation line of the side surface outer edge.
A step of determining that the peripheral edge of the second main surface of the tablet is chipped when the distance between each pixel on the outer edge of the side surface and the fourth approximation line is longer than a predetermined threshold value. A tablet inspection method. A tablet inspection device for inspecting the appearance of a tablet having a pair of a first main surface and a second main surface and a side surface.
An imaging unit that captures an image of a tablet and generates an image that captures both the first main surface and the side surface.
Equipped with an image processing unit
The image processing unit
In the captured image, the boundary edge corresponding to the boundary between the main surface region and the side surface region occupied by the first main surface and the side surface of the tablet is specified.
A first approximation line that approximates the boundary edge is calculated based on a function indicating the shape of the boundary in the captured image.
A tablet inspection for determining that the peripheral edge of the first main surface of the tablet is chipped when the distance between each pixel on the boundary edge and the first approximation line is longer than a predetermined threshold value. Device.

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