JP2017016443A - Paper sheets identification apparatus, and paper sheets identification method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper sheets identification apparatus capable of identifying paper sheets based on images of the paper sheets irrespective of the state of paper sheets.MEANS FOR SOLVING THE PROBLEM: A paper sheets identification apparatus in an embodiment for identifying paper sheets based on the images of the paper sheets, includes: an imaging unit that picks up images of the paper sheets; an image processor that rotates and corrects the images of the paper sheets acquired from the imaging unit and identifies the paper sheets based on the rotated and corrected images. The image processor segments the images of the paper sheets into plural areas and rotates and corrects the images on each of the plural areas.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a paper sheet identification device and a paper sheet identification method for identifying paper sheets such as banknotes and securities.

  The paper sheet identification device uses the image acquired from the paper sheet to determine the type and authenticity of the paper sheet, and there is a defect such that the image of the paper sheet is oblique with respect to the reference direction. Even if it occurs, the image of the paper sheet can be identified by correcting this. For example, Japanese Patent Application Laid-Open No. 7-311867 and Japanese Patent Application Laid-Open No. 8-212417 are disclosed as prior arts that disclose correcting a paper sheet image. These paper sheet identification devices according to the prior art calculate the skew angle of the paper sheet from the image of the paper sheet, and rotate the image based on the calculation result to enable the paper sheet identification. Yes.

JP 7-311867 JP-A-8-212417

  However, depending on the degree of damage such as folding, tearing, or other deformation of the paper sheet, even if the paper image is corrected as in the prior art, the paper sheet It was difficult to identify the class. Accordingly, the present invention has an object to provide a paper sheet identification device and a paper sheet identification method that enable identification of paper sheets based on images of paper sheets regardless of the state of the paper sheets. To do.

  In order to achieve the above object, the present invention provides a paper sheet identification apparatus for identifying a paper sheet based on an image of a paper sheet, an imaging apparatus that captures the image of the paper sheet, and the imaging apparatus. An image processing device that rotationally corrects the image of the paper sheet obtained from the image and identifies the paper sheet based on the corrected image, and the image processing device includes the image of the paper sheet. Differentiating into a plurality of areas, the rotation correction of the image is performed in each of the plurality of areas.

  According to the present invention, it is possible to provide a paper sheet identification apparatus and a paper sheet identification method that enable identification of paper sheets based on images of paper sheets regardless of the state of the paper sheets. I can do it.

It is a front perspective view of the paper sheet processing apparatus carrying the paper sheet identification device which concerns on this invention. It is a back perspective view of the paper sheet processing apparatus. It is a hardware block diagram of the paper sheet processing apparatus. It is a side view of the paper sheet processing apparatus showing a paper sheet conveyance path inside the paper sheet processing apparatus main body. It is a hardware block diagram of the paper sheet identification device which concerns on embodiment of this invention. It is a figure which shows the principle of the imaging of paper sheets performed by the imaging device of the paper sheet identification device which concerns on embodiment of this invention. It is a top view of the paper sheets currently conveyed by one form of the conveyance apparatus of paper sheets. It is a plane image of paper sheets for showing an example of a conveyance form of paper sheets. It is a plane image of paper sheets for showing the other example of the conveyance form of paper sheets. It is a plane image of paper sheets for showing the further another example of the conveyance form of paper sheets. It is the graph which showed the relationship of the skew angle in each line segment of the image of paper sheets. It is a plane image of paper sheets before skew angle correction. It is a plane image of the paper sheet after the skew angle is corrected. It is a flowchart explaining an example of paper sheet identification operation | movement. It is a flowchart which concerns on an example of the image correction operation | movement of paper sheet identification device. 16 is a flowchart according to a modified example of the image correction operation in FIG. 15.

  Next, an embodiment of the present invention will be described. 1 and 2 show a paper sheet (banknote) processing apparatus, and FIG. 3 is a hardware block diagram of the paper sheet processing apparatus 1. The paper sheet processing apparatus 1 enables handling of paper sheets, and is installed such that the front side faces a customer side and the back side faces a financial institution such as a bank. The paper sheet processing apparatus 1 includes a control circuit 10, a transport apparatus 3, a paper sheet identification apparatus 4, a communication apparatus 5, a customer side display apparatus 6, a customer side operation apparatus 7, and a financial institution side display apparatus. 8 and a financial institution-side operation device 9. The paper sheet processing apparatus 1 is used for processing such as deposit and withdrawal of paper sheets, and the control circuit 10 controls the operation of each apparatus such as a transport apparatus.

  The conveyance device 3 conveys the paper sheet along the paper sheet conveyance path in the paper sheet processing apparatus. The paper sheet identification device 4 identifies the denomination and authenticity of each paper sheet transported along the paper sheet transport path. The paper sheet identification device 4 obtains an image of the paper sheet, and identifies the type and authenticity of the paper sheet based on the pattern appearing in the image. The communication device 5 controls communication with a host device such as a host device (not shown) of a financial institution or a terminal operated by a financial institution side person.

  The customer side display device 6 displays a guidance message for the customer, a paper sheet count result, and the like. On both the left and right sides of the front side of the sheet processing apparatus 1, a lamp that indicates whether or not the customer is in use and a lamp that notifies the occurrence of a failure are provided. The customer side display device 6 performs lighting control of these lamps. The customer side operation device 7 has start buttons 7a and 7b provided on both the left and right sides of the front surface of the main body of the sheet processing apparatus 1. By counting the start buttons 7a and 7b, the counting of the sheets fed by the customer is started.

  The financial institution-side personnel display device 8 includes financial institution-side personnel indicators 8 a and 8 b provided on the left and right sides of the back side of the main body of the paper sheet processing apparatus 1. On both the left and right sides of the back of the main body of the paper sheet processing apparatus 1, there are provided a lamp for indicating whether or not financial institution personnel are in use and a lamp for notifying the occurrence of a failure. The personnel display device 8 performs lighting control of these lamps. The personnel-side operation device 9 has start buttons 9a and 9b provided on the left and right sides of the back side of the main body of the sheet processing apparatus 1. By counting the start buttons 9a and 9b, the counting of the sheets fed by the personnel is started.

  FIG. 4 shows a paper sheet transport path inside the paper sheet processing apparatus main body. The left side is the front side of the main unit. The paper sheet processing apparatus 1 includes, on the front side and the back side, paper sheet inlets 11 and 21, paper sheet discharge ports 12 and 22, and paper sheet return port 13, respectively. 23. The front-side paper sheet input port 11, the paper sheet discharge port 12, and the paper sheet return port 13 each have a shutter.

  The paper sheet processing apparatus 1 stores a collection cartridge 15 and a denomination cartridge 16 (16a to 16e) in a detachable manner inside. The collection cartridge 15 stores paper sheets that cannot be used in transactions. The denomination cartridge 16 has a denomination of paper sheets to be stored therein. For example, the denomination cartridge 16a is for 100 US dollar paper sheets, the denomination cartridge 16b is for 50 US dollar paper sheets, the denomination cartridge 16c is for 20 US dollar paper sheets, the denomination cartridge 16d is for 10 US dollar paper sheets, The money type cartridge 16e is for 5 US dollar paper sheets. The paper sheet processing apparatus 1 includes a temporary storage unit 17 that temporarily stores paper sheets.

  The paper sheet transport path 30 includes a paper sheet input port 11, 21, a paper sheet discharge port 12, 22, a paper sheet return port 13, 23, a collection cartridge 15, a denomination cartridge 16, and a temporary storage unit 17. The paper sheet identification device 4 exists in the middle of the paper sheet conveyance path 30.

  FIG. 5 shows a hardware block diagram of the paper sheet identification device 4. The paper sheet identification device 4 includes a paper sheet image capturing device 230 such as a line sensor or an image sensor, and the control circuit (image processing device) 2 uses the information obtained by the imaging device 230 as a paper sheet identification program. The outer shape of the image is processed (outer shape processing unit 240), and based on the outer shape processed image, the type of paper sheet (denomination in the case of banknotes) is determined (denomination determination unit 250), The authenticity is determined (authentication determination unit 260). The control circuit 2 is configured by known computer hardware resources and software. The outer shape processing unit 240, the denomination determining unit 250, and the authenticity determining unit 260 are configured by hardware resources (CPUP and the like) and software, but may be configured by graphic hardware such as a graphic board.

  The ROM 210 includes a nonvolatile memory, and stores a paper sheet identification program and fixed value parameters. The RAM 220 includes a volatile memory, and stores variables handled by the control circuit 2 and images captured by the imaging device 230. The outline processing unit 240 obtains an outline, a skew angle, and the like in the image of the paper sheet, and corrects the position of the image by rotation processing, parallel movement, and the like. The denomination determining unit 250 determines the denomination while distinguishing the direction of the paper sheet. The authenticity determination unit 260 determines whether or not the paper sheet is a genuine note from the corrected paper sheet image. The various sensors 280 include a magnetic sensor, a thickness sensor, and the like, and are used for authenticating paper sheets.

  FIG. 6 is a diagram illustrating the principle of imaging of the paper sheet 300 performed by the imaging device 230. The paper sheet 300 is conveyed in the direction 420. A light emitter 400A including a plurality of LEDs arranged in the width direction of the paper sheet irradiates the upper surface of the paper sheet 300, and the line sensor 410A receives the light reflected from the paper sheet 300. Since the image data from the line sensor 410A is continuously stored in the RAM 220 in the process of transporting the paper sheet 300, the control circuit 2 can generate a two-dimensional image of the paper sheet. With respect to the lower surface of the paper sheet 300, a two-dimensional image of the paper sheet is obtained by the light emitter 400B and the line sensor 410B in the same manner as the upper surface. Note that the paper sheet identification device 4 may be configured to capture only one side of the sheet instead of capturing images on both sides of the paper sheet, and employs a two-dimensional image sensor instead of the line sensor. May be.

  FIG. 7 is a plan view of the sheet 300 being conveyed, showing one form of conveyance of the sheet 300. The transport device 3 includes a belt 450A that sandwiches the right side of the paper sheet 300 in the transport direction 420 from the upper surface and the lower surface, and a belt 450B that sandwiches the left side of the paper sheet from the upper surface and the lower surface of the paper sheet. The paper sheet 300 is conveyed by rotating the belt in the same direction. When the paper sheet 300 is transported, depending on the state of the paper sheet and the state of the transport device, the transport mode of the paper sheet is different from the optimum state, and this transport mode is a characteristic difference of the image of the paper sheet. appear. For example, the paper sheet 300 may be conveyed while forming an angle (θ) with respect to the direction 301 perpendicular to the conveyance direction. When the paper sheet 300A is transported at an inclination with respect to the transport direction 420, it is referred to as “the paper sheet is skewed”, and the angle (θ) between the paper sheet and the orthogonal direction 301 is already set. As mentioned above, it is called “skew angle”.

  When the paper sheet 300A is conveyed with a skew angle (θ), this effect appears in the image of the paper sheet obtained by the imaging device 230, resulting in a skewed image. The problem of misalignment of leaf designs occurs. Therefore, the outline processing unit 240 calculates the skew angle of the paper sheet based on the detected image of the paper sheet 300, rotates the image in a direction to eliminate the skew angle, and based on the corrected image, The seed determination unit 250 determines the denomination of the paper sheet, and the authenticity determination unit 260 determines the authenticity of the paper sheet.

  Even if the paper sheet is in a skewed state, as shown in FIG. 8, the corner of the paper sheet 300 is slightly bent (422), or as shown in FIG. Even if the end portion is bent widely (424), the skew angle is the same as the entire paper sheet 300 because the paper sheet 300 is equally pinched by the conveying belts 450A and 450B.

On the other hand, as shown in FIG. 9, for example, when there is a fold along the longitudinal center line (EB) of the paper sheet, and there is a tear 423 on the end side of the fold, The skew angle may be different on the left and right sides (regions). In FIG. 9, the skew angle (θ ₁ ) on the left side of the paper sheet 300 and the skew angle (θ ₂ ) on the right side of the paper sheet 300 are different. Is large (θ ₂ > θ ₁ ). In this case, even if the paper sheet is rotated at its center G so as to cancel the skew angle, the image cannot be corrected so as to eliminate the skew angle on at least one of the left and right sides of the paper sheet. .

  Next, paper sheet identification processing in the paper sheet identification apparatus will be described with reference to FIG. FIG. 14 is a flowchart showing the operation of the control circuit 2. When the control circuit 2 detects that the paper sheet 300 has reached the imaging device 230, the control circuit 2 starts the identification program, drives the light emitters (400A, 400B) and the sensors (410A, 410B), A paper sheet is imaged every time (S10).

  Next, the control circuit 2 performs image processing necessary for identifying the paper sheet on the captured image. That is, the control circuit 2 extracts the outline of the paper sheet from the image of the paper sheet, the center of the paper sheet, the four vertices, the middle point of the upper side, the middle point of the lower side, the length of each line segment, and the skew angle. And the image is rotationally corrected based on the calculated values to determine the image of the paper sheet (S11). The control circuit 2 determines the denomination based on the confirmed image (S12), and the paper sheet 300 is genuine using the image and the data collected by the various sensors 28 based on the denomination. Whether or not is true or false is determined (S13).

  FIG. 15 is a flowchart for explaining the details of the above-described outline processing (S11). The control circuit 2 determines the outline of the paper sheet from the image of the paper sheet (S20). From these outlines, as can be easily understood with reference to FIGS. 8 to 10, a line segment AB (B: midpoint on the lower side of the paper sheet) and a right half line of the lower side of the paper sheet. A total of 6 sections including a line BC, a line segment DE on the right side of the upper side DE (E: middle point on the upper side of the sheet), a line segment EF on the left side of the upper side, a line segment AF on the left side, and a line segment CD on the right side An approximate straight line is extracted for each line segment (S21). The reason why the approximate curves are extracted on the left and right sides of the paper sheet is that the control circuit 2 performs correction by distinguishing the left and right sides of the paper sheet.

For example, the control circuit 2 calculates an approximate curve so that the error is minimized by the least square method, or performs processing so that the ratio of the contour points whose distance from the approximate line is within a certain value is the largest. Then, the control circuit 2 obtains an intermediate point between the four vertexes and the lower side and an intermediate point between the upper side from the intersection of the adjacent approximate lines (S22). As a result, when the lower right corner 422 of the paper sheet 300 is slightly folded (422) as shown in FIG. 8, the vertex obtained as the intersection of the approximate straight lines is C, and the folded corner Matches the original vertex when not affected. Meanwhile, the vertex determined as the intersection of the fitted line when the folding area 424 is widely formed in the longitudinal direction of the paper sheet 300 as shown in FIG. 10 becomes C _1, the vertex C (original of the sheet The coordinates are different from (vertex).

The control circuit 2 calculates the skew angle based on the vertices obtained from the image of the paper sheet 300 (S23). θ _AB is an oblique angle of the line segment AB as an angle formed by the line segment AB with respect to a direction orthogonal to the transport direction. When the paper sheet is transported without being inclined, the skew angle is zero or substantially zero. The same applies to θ _BC , θ _EF and θ _DE .

The oblique angles of the four approximate straight lines (line segment AB, line segment BC, line segment DE, line segment EF) in the case of FIG. 8 are substantially the same as shown in FIG. In the case of FIG. 9, the skew angles of the four approximate lines are substantially equal to θ _AB and θ _EF and θ _BC and θ _DE are substantially equal as shown in FIG. 11B, but θ _AB and θ _BC. The difference is relatively large. The skew angles of the four approximate lines in the case of FIG. 10 are substantially equal to θ _AB , θ _EF and θ _DE as shown in FIG. 11C, but the difference between θ _AB and θ _BC is relatively large.

  In the paper sheet 300 of FIG. 10, although the folding area 424 exists, the skew angle of the paper sheet itself is the same on the left and right sides. Therefore, the control circuit 2 determines whether or not correction of the folding of the paper sheet is necessary in order to obtain an appropriate skew angle in the right half and the left half of the paper sheet (S24). That is, the control circuit 2 determines whether the difference between the skew angle of the upper side line segment and the skew angle of the lower side line is within the threshold value 1 in each of the right half and the left half of the paper sheet 300. If the difference is larger, it is determined that it is necessary to correct the fold and obtain an appropriate skew angle (YES in S24).

When | θ _EF −θ _AB |> threshold value 1 is determined, in the left half of the paper sheet, correction of the folded area, that is, the skew angle of at least one of the upper side EF and the lower side AB of the left side area of the paper sheet Is determined to be necessary. Similarly, when determining | θ _DE −θ _BC |> (threshold 1), the control circuit 2 determines that correction of the folding region in the right region of the paper sheet 300 is necessary.

As shown in FIG. 10, when a long folded region is generated on the lower right side BC ₁ of the paper sheet 300 as shown in FIG. 10, | θ _DE −θ _BC |> threshold value 1 and Since | θ _EF −θ _AB | ≦ threshold 1, the control circuit 2 determines that folding correction is necessary in the right half of the paper sheet (YES in S24).

Next, as shown in FIG. 10, when the control circuit 2 determines that correction of the folded portion is necessary in one of the plurality of regions of the paper sheet 300, the left upper side EF and the right upper side DE of the paper sheet The difference between the skew angle (| θ _EF −θ _DE |) of the paper sheet and the skew angle difference (| θ _AB −θ _BC1 |) between the lower left side AB and the lower right side BC ₁ of the paper sheet is calculated. If it is determined whether or not the difference is larger than the threshold value 2 and the result is affirmative, the skew angle of the line segment with the folded area is not broken with reference to the skew angle of the unfolded area. Replace with the skew angle of the line segment of the area (S25).

That is, if the control circuit 2 determines that correction of the folded portion is necessary only in the right half of the paper sheet and determines | θ _AB −θ _BC |> threshold 2, θ _BC is replaced with θ _AB , or | If it is determined that θ _EF −θ _DE |> threshold value 2, the skew angle (θ _DE ) is replaced with the skew angle (θ _EF ). When the control circuit 2 determines that correction of the folded portion is necessary only in the left half of the paper sheet and determines | θ _AB −θ _BC |> threshold 2, the skew angle (θ _AB ) is changed to the skew angle (θ _BC ), And | θ _EF −θ _DE |> threshold 2, the skew angle (θ _EF ) is replaced with the skew angle (θ _DE ).

In the transport mode of the paper sheet shown in FIG. 10, | θ _EF −θ _DE | ≦ threshold 2 is satisfied, and the skew angle is not corrected on the upper right side of the paper sheet, but as described above, | θ _{Since AB} −θ _BC |> threshold 2, the skew angle θ _BC of the line segment _BC is replaced with the skew angle θ _AB of the adjacent line segment AB on the lower right side of the paper sheet. As a result, the coordinates of the lower right vertex of the paper sheet are replaced from the point C ₁ to the original lower right vertex point C of the paper sheet. On the other hand, in the case where the paper sheet is transported in FIG. 8, the difference between the skew angle of the upper side of the paper sheet and the skew angle of the lower side of the paper sheet is the threshold value in the right half and the left half of the paper sheet. Since it is within 1, the folding area is not corrected (S234: NO).

  As shown in FIG. 10, not only the lower half of the right half of the paper sheet is folded long (424), but also the left half of the paper sheet ( If there is a similar fold on the lower side AB and / or the upper side EF), fold correction is required on both the right and left halves of the paper sheet. The control circuit 2 determines which line segment is based on the skew angle. In this case, various methods are conceivable. The control circuit 2 sets the skew angle of the line segment whose angle between the right side and the left side is close to π / 2 as the reference skew angle, or the right and left sides of the sheets. Only when the difference in skew angle between the matching line segments is small, the skew angle is corrected only when the skew angle can be reliably corrected, for example, by setting the skew angle of one line segment to the reference skew angle.

  Next, the control circuit 2 determines the length of the lower left side AB of the paper sheet, the length of the lower right side BC of the paper sheet, and the upper right side of the paper sheet from the intersection of each line segment after the skew angle is corrected. The DE length, the length of the upper left side EF of the paper sheet, the length of the right side CD of the paper sheet, the length of the left side AF of the paper sheet and the center G of the paper sheet are calculated (S26). An approximate contour of the leaf image is determined.

  Next, in order to eliminate the skew angle from the image of the paper sheet 300, the control circuit 2 performs correction for rotating the paper sheet image on the left and right sides of the image of the paper sheet, or the paper sheet It is determined whether to perform the entire image.

The control circuit 2 determines the skew angle (θr) of the right half of the image of the paper sheet,
Calculated from θr = (θ _BC + θ _DE ) / 2,
Set the skew angle of the left half of the paper sheet to (θl),
Calculated from θl = (θ _AB + θ _EF ) / 2.

Then, the control circuit 2 compares the difference between θr and θl (| θr−θl |) and the threshold 3, and if this difference is larger than the threshold 3, the right half and the left half of the image of the sheet are separately provided. It is determined that it is necessary to rotate at a certain angle (YES in S27). In the case where the paper sheet is transported in FIG. 8, the difference (| θr−θl |) ≦ threshold value 3 is satisfied, and the control circuit 2 rotates the image of the paper sheet so as to be different on the left and right sides (divided rotation). It is determined that it is not necessary (NO in S27). Even when the paper sheet is conveyed as shown in FIG. 10, θ _BC has already been replaced by θ _AB , so | θr−θl | ≦ threshold value 3 and the image of the paper sheet is different on the left and right sides. Is determined to be unnecessary (NO in S27). 8 and FIG. 10, the skew angle (θ _N ) of the upper line segment and the lower line segment is the same in each of the left and right sides of the image of the paper sheet. For,
θr = (θ _N + θ _N ) / 2, θl = (θ _N + θ _N ) / 2
From θ _M = (θr + θl) / 2 (= θ _N ),
The control circuit 2 rotates the entire sheet image by θ _M (= θ _N ) with the center point G of the sheet image as the center of rotation (S29).

On the other hand, in the case where the paper sheet is conveyed as shown in FIG. 9, the control circuit determines that | θr−θl |> threshold 3 and needs to rotate the image of the paper sheet in a different manner on the left and right. Is determined. As shown in FIG. 12, the control circuit 2 rotates the right half image clockwise by a skew angle θ ₃ around the center G of the sheet image, and skews the left half image. It is rotated counterclockwise by the angle θ ₄ minutes (S28). As a result, the image 330A after the rotation of the original image 330 of the paper sheet is corrected so that the skew angle is eliminated in each of the right half and the left half of the paper sheet as shown in FIG. . The control circuit 2 can obtain a corrected image from which the skew angle is eliminated from the original image of the paper sheet, and can perform the denomination or authenticity determination of the paper sheet.

  In the flowchart of FIG. 15, it has been determined whether it is necessary to rotate the left and right sides of the paper sheets in different modes (S27). However, the related processing (S27, S29) is omitted, and the paper sheets are always used. The left and right sides of the class may be rotated separately (FIG. 16). In the case where the skew angle on the left and right sides of the paper sheet is the same, the left and right sides are rotated at the same angle, so that the same corrected image as that obtained when the paper sheet is rotated as a whole is obtained.

  In the above-described embodiment, the paper sheet is transported with the longitudinal direction of the paper sheet orthogonal to the transport direction. However, the paper sheet is transported along the transport direction in the longitudinal direction of the paper sheet. Even in this case, by dividing the image of the paper sheet before and after the conveyance direction, it is possible to eliminate the influence of the skew of the paper sheet.

2 Control circuit (image processing device)
4 Paper sheet identification device 230 Imaging device 300 Paper sheet

Claims (9)

In the paper sheet identification device for identifying the paper sheet based on the image of the paper sheet,
An imaging device for capturing an image of the paper sheet;
An image processing device that rotationally corrects the image of the paper sheet obtained from the imaging device and identifies the paper sheet based on the image after the rotation correction;
With
The image processing apparatus is a paper sheet identification apparatus that distinguishes an image of the paper sheet into a plurality of areas based on the transport mode of the paper sheet, and performs rotation correction of the image in each of the plurality of areas.   The paper sheet identification apparatus according to claim 1, wherein the image processing apparatus distinguishes an image of the paper sheet into a plurality of regions based on a conveyance direction of the paper sheet.   The image processing device calculates a skew angle with respect to a conveyance direction of the paper sheet from an image of each of the plurality of areas, and rotationally corrects the image of each of the plurality of areas based on the skew angle. The paper sheet identification apparatus according to 1. The image processing apparatus includes:
For each image of the plurality of regions, calculate a skew angle with respect to the transport direction of the paper sheet,
Determine the skew angle difference between the images,
Depending on the result of the determination, the entire image of the paper sheet is rotationally corrected based on the skew angle without distinguishing the image of the paper sheet into a plurality of regions, and / or The paper sheet identification device according to claim 1, wherein the image of each region is rotationally corrected based on the skew angle.   The paper sheet identification device according to claim 3, wherein the image processing device corrects the influence of folding on the paper sheet from the image and then rotationally corrects the image of each of the plurality of regions. The image processing apparatus includes:
Based on the transport direction of the paper sheet, the image of the paper sheet is distinguished into a first area and a second area,
Calculating a first skew angle with respect to the transport direction from the image of the first region;
Calculating a second skew angle with respect to the transport direction from the image of the second region;
Comparing the first skew angle with the second skew angle;
Evaluating a difference between the first skew angle and the second skew angle based on a predetermined threshold;
If the result of the evaluation is first, the entire image of the paper sheet is rotationally corrected based on at least one of the first skew angle and the second skew angle;
If the result of the evaluation is second, the image of the first area is rotationally corrected based on the first skew angle, and the image of the second area is set to the second skew angle. Rotation correction based on
The paper sheet identification apparatus according to claim 1. The image processing apparatus includes:
When the evaluation is the first, the same skew angle based on the first skew angle and the second skew angle is used, and the images of the plurality of regions are not distinguished from each other. The paper sheet identification apparatus according to claim 6, wherein the entire image of the paper sheet is rotationally corrected. In a method for identifying a paper sheet based on an image of the paper sheet by a control circuit that enables image processing,
The control circuit includes:
A first step of acquiring an image from the paper sheet;
A second step of rotationally correcting the image of the paper sheet;
Performing a third step of identifying the paper sheet based on the image after the rotation correction,
The second step is a paper sheet identification method in which an image of the paper sheet is classified into a plurality of areas based on the transport mode of the paper sheet, and the rotation correction of the image is performed in each of the plurality of areas. The program for making a computer perform each step of Claim 8.

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