JP2012247278A - Watermark position checking method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a checking method with which a watermark and a paper end are imaged sharply and a watermarked position is measured highly accurately without incurring variance.SOLUTION: An imaging condition of a paper end imaging line camera is preset to such an imaging condition that a paper end can be imaged sharply, and an imaging condition of a watermark imaging line camera is set to such an imaging condition that a watermark can be imaged sharply. Afterwards, a paper end image and a watermark image are captured in the line cameras, respectively, coordinates indicating the paper end are detected from the paper end image, and coordinates indicating the watermark are detected from the watermark image. After a distance from the coordinates of the paper end to the coordinates of the watermark is calculated, it is determined whether or not the calculated distance between the coordinates is settled within an allowable range, thereby determining whether or not a position forming the watermark therein is acceptable.

Description

  The present invention relates to a method for inspecting a pouring position of a paper sheet that has undergone poking.

  With the recent development of digital devices such as scanners and color copiers, it has become possible to easily produce elaborate counterfeit products such as banknotes and passports. As one of the measures for preventing counterfeiting, a large number of creased printed materials are distributed. The penetration means that the pattern cannot be visually recognized under reflected light, but the pattern can be visually recognized only under transmitted light. The printed material subjected to the squeezing is manufactured by squeezing the paper before printing and then performing various printings on the paper. Therefore, when producing printed matter related to the printing and banking position of banknotes and passports, it is extremely important to confirm the position of the paper from the paper edge to the papering at the time of paper production.

  As a method of confirming the paper pouring position, the applicant applies the mark for confirming the pouring position to the edge of the paper by the pouring and stacks the paper when laminating the paper. An application has been filed for a method for inspecting the pouring position by drawing a double line from the side of the printed paper in the vicinity of the poking position confirmation mark and comparing the positional relationship between the poking position confirmation mark and the double line ( For example, see Patent Document 1).

  As another method, the paper that has been squeezed is conveyed by a transmission drum or a conveyor, and the paper being conveyed is irradiated by illumination installed in the transmission drum. An inspection apparatus is disclosed in which a transmission image is picked up by a line camera installed in the apparatus, and a clearance is inspected based on the transmission image thus picked up (see, for example, Patent Document 2).

  Furthermore, a bill discriminating device using an image sensor and a black transfer roller is disclosed as a method for detecting the other paper edge (see, for example, Patent Document 3). This bill discriminating device detects a paper edge (lower end) from a state where there is no bill whose output level of the image sensor is black when the bill passes, and rises to a state where there is a white bill. When the edge of the paper is detected, detection of the reflected image of the image sensor is started. After that, when the edge of the paper (upper edge) is detected and falling from white to black, the acquisition of the image sensor data is terminated. is there.

JP 2009-229177 A JP 2005-513436 A JP 7-334724 A

  However, in the method of Patent Document 1, when a stacking deviation occurs during the stacking of sheets, a double line is drawn in a state where the deviation has occurred. The inspection will be based on the double line that is not correlated with the position. In this method of inspecting with two lines, since the sheets are stacked manually, there is a high possibility that variations will be caused by the operator, and as a result, there remains a problem that the inspection accuracy of the cleaning position is lowered. It was. Furthermore, personnel who perform sheet loading, line drawing, and squeeze position inspection are required, and the human cost has been a problem.

  Further, in the method of Patent Document 2, it is necessary to irradiate the sheet with visible light with high illuminance in order to capture a clear penetration, and in that case, the edge of the sheet is clear by strong light coming from the illumination. There is a problem that it is impossible to pick up a paper edge image. On the other hand, in order to prevent the light from wrapping around, it is possible to capture the edge of the paper when it is irradiated with visible light with low illuminance. However, it is impossible to carry out the position inspection of the clearance with high accuracy.

  Furthermore, in the method of Patent Document 3, the edge of the paper is clearly detected, but as described above, in order to capture a clear penetration, in the case where high-illuminance visible light is irradiated, the light from the illumination As a result, the output level of the image sensor does not normally rise from the black level (without banknotes) to the white level (with banknotes) when the banknote passes, and the paper edge cannot be detected.

  The present invention solves these problems, and provides an inspection method for clearly capturing images of a squeeze and a paper edge and measuring the squeezed position with high accuracy without causing variations. By the way.

  In order to achieve the above-described object, a method for inspecting a pouring position according to the present invention includes a paper edge imaging line camera for imaging a paper edge of a paper, and a gap imaging line camera for imaging a gap formed on the paper. In the indentation position inspection method for inspecting the position from the edge of the paper to the indentation formed on the sheet using an inspection apparatus having at least the Set the imaging conditions for clear imaging, set the imaging conditions for the clear imaging line camera to the imaging conditions that enable clear imaging of the penetration formed on the paper, irradiate the surface of the paper with visible light, and then transmit through the paper. Light is detected, a paper edge image and a cut-in image are acquired by each line camera, the paper edge image is binarized, and then the paper edge of the paper is detected from the binarized paper edge image. The coordinates are detected, and the corrected image is corrected based on at least one side of the coordinates indicating the paper edge of the paper detected from the paper edge image, and the corrected image is set in advance. Pattern matching is performed with the reference standard image, and the coordinates indicating the cleaning position in the paper are detected, the distance from the coordinates indicating the paper edge of the paper to the coordinates indicating the cleaning position is calculated, and the calculated paper in the paper is calculated. The distance from the coordinates indicating the edge position to the coordinates indicating the pouring position in the paper, and the allowable range of the distance from the coordinates indicating the paper edge position in the pre-set paper to the coordinates indicating the poking position in the paper A comparison is made, and whether or not the position where the clearance is formed is determined according to whether or not it is within the allowable range.

  In addition, according to the method for inspecting the pouring position of the present invention, at least one of the exposure time, the aperture, and the gain is set as the imaging condition for clearly capturing the edge of the sheet and the imaging condition for clearly capturing the gap formed on the sheet. It is characterized by combining.

  Furthermore, the cleaning position inspection method of the present invention is characterized in that at least one of the exposure time, the aperture, and the gain, which are the imaging conditions described above, is different.

  By performing the poking position inspection of the present invention, it becomes possible to clearly pick up the pouring pattern and the paper edge. Therefore, it is possible to inspect an accurate insertion position using the captured clear image.

The top view which shows an example of the paper (2) used as the inspection object of this invention Schematic diagram showing an example of a penetration inspection device (M) Block diagram of penetration inspection device (M) Schematic diagram explaining the wraparound of light Schematic diagram showing the imaging position of each line camera (9, 10) Schematic diagram showing the imaging position of each line camera (9, 10) Flow chart showing the pouring position inspection method Schematic diagram showing the paper edge image (9a) Schematic diagram showing the cut-in image (10a) Schematic diagram showing a method of calculating a correction value from the paper edge image (9a) Schematic diagram showing a method for correcting the cut-in image (10a) Schematic diagram showing pattern matching Schematic diagram showing a cut-in image (10a '') after pattern matching

  Embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments to be described below, and various other embodiments can be implemented within the scope of the technical idea described in the claims.

  FIG. 1 is a plan view showing an example of a sheet (2) that is an object to be inspected according to the present invention, and at least a part of a substrate (2a) is filled (1). The penetration (1) is a pattern applied by partially varying the thickness and density of the substrate (2a). By observing the paper (2) under transmitted light, the pattern and outer shape applied with the substrate (2a) partially different in thickness and density are clearly visible. Hereinafter, in the present invention, it is said that the clearance (1) is formed on the paper (2) when the clearance (1) is applied to the substrate (2a). The paper (2) has a long side (3) and a short side (4) which are paper edges (L). Note that, as shown by a bold line in FIG. 1, the paper edge (L) in the present invention is a collective term that includes a total of four sides, the upper and lower long sides (3) and the left and right short sides (4). . The gap (1) is inspected by measuring the distance from the paper edge (L) of the sheet (2) and the distance between the gaps (1).

  In FIG. 1, a plurality of identical images (1) are formed on a sheet (2) on 20 surfaces of 4 rows × 5 surfaces, and then the sheet (2) is cut one by one. Thus, 20 sheets of paper are obtained. It should be noted that the number of faces and the position at which the clearance (1) is formed are not particularly limited as long as the clearance (1) is formed, not limited to the 20 faces described above.

  Next, the penetration inspection apparatus (M) for inspecting the position of the penetration (1) formed on the paper (2) will be described.

  The penetration inspection apparatus (M) in FIG. 2 includes an illumination (8) that is an irradiation unit, a paper edge imaging line camera (9) and a penetration imaging line camera (10) that are imaging units, and an image processing unit (13). ), A determination unit (14) including a storage unit, and a control unit (not shown) that controls each unit.

  In the penetration inspection device (M), the sheet (2) is sent out to the upstream conveyor (6) by a feeder unit (not shown). Next, after capturing the paper (2) with the two line cameras (9, 10) (1) and the edge (L), respectively, the image processing unit (13) based on each captured image, The inspection of the insertion (1) position is performed, and finally the pass / fail judgment of the paper (2) is performed in the determination unit (14).

  FIG. 3 is a block diagram showing the penetration inspection apparatus (M) described above. Hereinafter, the inspection apparatus (M) for inspecting the insertion position of the present invention will be described.

  The feeder unit (not shown) is means for feeding sheets (2) one by one to the upstream conveyor (6).

  The upstream conveyor (6) and the downstream conveyor (7) are means for transporting the paper (2), and each includes a transport belt (6a, 7a) and a roller (6b, 7b). Each conveyor (6, 7) is linearly arranged in the same direction as the transport direction, so that the paper (2) is transported one by one in the penetration inspection device (M) while maintaining flatness. It becomes possible to do.

  In each conveyor (6, 7), the rollers (6b, 7b) rotate to rotate the conveyor belts (6a, 7a) synchronously. Thereby, the paper (2) on the transport belts (6a, 7a) is transported through the penetration inspection device (M). When the paper (2) is transported at a high speed (for example, a speed of about 3 m / s), the paper (2) being transported fluctuates, and accurate imaging is performed by the line cameras (9, 10). An image may not be acquired. In that case, a plurality of suction holes may be provided in the transport belt (6a, 7a) to transport the paper while sucking. Furthermore, a means for holding the paper (2) may be attached in the vicinity of each conveyor (6, 7).

  The illumination (8) is a means for irradiating the surface of the paper (2) with visible light, and is disposed below or above the paper (2) transport path between the upstream conveyor (6) and the downstream conveyor (7). The By arranging the illumination (8) between the conveyors (6, 7), visible light irradiated from below or above the paper (2) passes only through the paper (2), and then the paper (2). Is received by each line camera (9, 10) arranged on the opposite side to the lower side or the upper side where the illumination (8) is arranged, which is a position opposite to each other, to capture a transmission image of the paper (2) It becomes possible.

  By uniformly irradiating the sheet (2) with visible light by the illumination (8), it is possible to image the gap (1) applied to the entire sheet (2). The illumination (8) needs to use high-luminance illumination such as high-luminance white LED illumination or metal halide illumination in order to capture the clear image of the gap (1). Furthermore, it is preferable to use a compact type that can store the paper (2) being conveyed without interfering with the space between the upstream conveyor (6) and the downstream conveyor (7).

  Of the two line cameras (9, 10), the paper edge imaging line camera (9) which is one of the line cameras is means for capturing a paper edge image (9a) where the paper edge (L) is clear, The sheet (2) is disposed at a position facing the illumination (8) via the conveyance path. As shown in FIG. 2, when the illumination (8) is disposed below the transport path of the paper (2), each line camera (9, 10) faces the illumination (8) via the transport path. When the illumination (8) is arranged above the conveyance path of the paper (2), each line camera (9, 10) is located below the illumination (8) via the conveyance path. Be placed. Each of the line cameras (9, 10) is a camera that sequentially acquires a one-dimensional image. The captured one-dimensional image is obtained for each line camera (9, 10) in the image processing unit (13). By arranging in the order of acquisition, it becomes one two-dimensional image. This two-dimensional image is each image (9a, 10a). Hereinafter, in the present invention, each image (9a, 10a) is an image captured by each line camera (9, 10), and the description of the process of generating a two-dimensional image from the one-dimensional image is omitted. .

  Note that, when an area camera is used as the imaging unit in the present invention, it is necessary to capture an image after the imaging target is stopped in front of the camera, which is not preferable because a lot of machine downtime occurs. Therefore, in the present invention, a line camera is used as the imaging unit. Each of the line cameras (9, 10) uses a known CCD line camera that inputs the transmitted light from the sheet (2) in a direction orthogonal to the conveyance direction of the sheet (2) as an image.

  The paper edge image (9a) is an image in which the paper edge (L) of the paper (2) is clearly imaged without being affected by the wraparound of light from the illumination (8). FIG. 4 is a schematic diagram for explaining the wraparound of light. As shown in FIGS. 4A and 4B, the line cameras (9, 10) capture an image within the viewing angle of θ1 including the paper edge of the paper (2). As shown in FIG. 4A, when the illumination (8) has low brightness, the amount of light received from the illumination (8) decreases, and the image captured by the line camera becomes a dark image. No wraparound occurs. On the other hand, when the illumination (8) has high brightness, the amount of light received from the illumination (8) increases as shown in FIG. 4B, and the image captured by the line camera becomes a bright image. Light wraparound occurs.

  Therefore, by reducing the amount of light received from the illumination (8) of the paper edge imaging line camera (9), a dark image can be obtained, but a clear paper edge (L) where light does not wrap around can be captured. It becomes. Further, by increasing the amount of light received from the illumination (8) of the clear imaging line camera (10), the light wraps around, but it is possible to capture a clear clear (1).

  Of the two line cameras (9, 10), the picked-up image line camera (10) is a means for picking up the picked-up image (10a) in which the clear (1) is clear, and the paper edge described above. Similar to the imaging line camera (9), it is arranged at a position facing the illumination (8) through the paper (2) conveyance path. The cut-in image (10a) is an image obtained by picking up the high-contrast image (1).

  In order to take a paper edge image (9a) where the paper edge (L) of the paper (2) is clear and a penetration image (10a) where the penetration (1) is imaged with high contrast, a paper edge imaging line camera is used in advance. The imaging condition of (9) is set to an imaging condition that allows the paper edge (L) of the paper (2) to be clearly photographed, and the imaging condition of the clear imaging line camera (10) is set to the clear formed on the paper (2). (1) is set as an imaging condition that enables clear shooting.

  The two line cameras (9, 10) appropriately set the imaging conditions such as sensitivity, imaging lens, and arrangement location according to the conditions under which each image can be clearly captured. Each of the images (9a, 10a) acquired by the line cameras (9, 10) has a low-lightness image in which the paper edge (L) is clearly imaged and a lightness in which the gap (1) is clearly imaged. The brightness difference between the images (9a, 10a) is preferably about 10 times, and in order to obtain such images with different brightness, the illumination (8) is obtained by two line cameras (9, 10). ) Needs to be different.

  In the line camera, when the amount of light received from the illumination (8) is small, the captured image becomes a dark image. On the other hand, when the amount of light received from the illumination (8) is large, the captured image becomes a bright image. Therefore, by setting the received light amount from the illumination (8) of the paper edge imaging line camera (9) to be smaller than the received light amount of the imaging line camera (10), it becomes a dark image, but the light wraps around. A clear paper edge (L) can be imaged without being affected. Also, the clear imaging line camera (10) captures a clear penetration (1), although light wraparound occurs by setting a larger amount of received light than the paper edge imaging line camera (9). It becomes possible to do.

  The imaging conditions that can clearly capture the paper edge (L) of the paper (2) and the imaging conditions that can clearly capture the gap (1) formed on the paper (2) are the sensitivity of the line camera, the location of the imaging lens, and the camera. In the same case, it is assumed that at least one of the exposure time, aperture and gain of each line camera or a combination thereof, and further, at least one of the exposure time, aperture and gain of each line camera is different.

  The imaging condition setting method in the paper edge imaging line camera (9) is as follows. First, the paper edge (L) of the paper (2) that is the inspection object is set to at least one or a combination of exposure time, aperture, and gain. In other words, different images are taken according to a plurality of imaging conditions. Among the captured images, the imaging condition when taking the image with the sharpest edge of the paper (L) is taken as the imaging condition under which the paper edge (L) of the paper (2) can be taken clearly. The imaging condition of the paper edge imaging line camera (9) is set.

  The imaging condition setting method in the penetration imaging line camera (10) is as follows. First, the penetration (1) of the sheet (2) as the inspection object is changed to at least one or a combination of exposure time, aperture and gain. In other words, different images are taken according to a plurality of imaging conditions. Of the captured images, the imaging condition when taking the image with the most clear (1) is taken as the imaging condition that allows the clear (1) to be taken clearly, and based on that, the clear imaging line camera The imaging condition of (10) is set.

  When images with different brightness are acquired by making the exposure times of the two line cameras (9, 10) different from each other, the paper edge imaging line camera () is compared with the exposure time of the clear imaging line camera (10). By setting the exposure time of 9) to be short, the amount of light received from the illumination (8) is reduced.

  Further, when acquiring images with different brightness by making the apertures of the two line cameras (9, 10) different from each other, the paper edge imaging line camera ( By closing the aperture of 9), the amount of light received from the illumination (8) is reduced.

  Further, when acquiring images with different brightness by differentiating the gains of the two line cameras (9, 10), the paper edge imaging line camera ( By reducing the gain of 9) and setting it, the amount of light received from the illumination (8) is reduced.

  Note that the gain setting includes acquiring images having different brightness levels by changing the sensitivities of the two line cameras (9, 10). As a method of making the sensitivity different, a method of reducing the light receiving element of the paper edge imaging line camera (9) as compared with the light receiving element of the buried imaging line camera (10) and the light receiving of the buried imaging line camera (10). There are methods in which the elements are arranged in two rows and the light receiving elements of the paper edge imaging line camera (9) are arranged in one row, and the amount of light received from the illumination (8) is adjusted by these methods.

  In order to inspect the insertion position formed on the sheet (2) with high accuracy, the same line in which the imaging position (input line) of each line camera (9, 10) is orthogonal to the conveyance direction (v1) of the sheet (2). It is necessary to input the upper sheet (2) with the same resolution, and the arrangement is as shown in the schematic diagrams of FIGS.

  FIGS. 5A and 6A are schematic views seen from the transport direction (v1) in FIG. 2, and FIGS. 5B and 6B are orthogonal to the transport direction (v1). It is the figure seen from direction (v2). In order to image the same position of the sheet (2), as shown in FIGS. 5 (a) and 5 (b), each line camera (9, 10) in the transport direction (v1) of the sheet (2). And the center line of the paper (2) being conveyed are arranged so that they substantially coincide with each other, and as shown in FIGS. 6 (a) and 6 (b), the conveyance direction of the paper (2) There is a case where they are arranged in a straight line in a direction (v2) orthogonal to (v1). These arrangements may be appropriately selected depending on the apparatus configuration of the penetration inspection apparatus (M).

  The line cameras (9, 10) arranged in this way are arranged so as to be shifted in the direction (v2) orthogonal to the transport direction. Therefore, before inspection, it is necessary to image the paper (2) on which the matrix-like scale is printed in advance, measure the deviation in the direction (v2) perpendicular to the transport direction, and store it in the image processing unit (13). There is.

  The encoder (12) is means for detecting the rotation timing of the rollers (6b, 7b) of the conveying belts (6a, 7a) that convey the paper (2), and the rollers (6b, 7b) of the conveyors (6, 7). ) Is installed on the roller shaft.

  By using the timing signal from the encoder (12), each line camera (9, 10) can capture each detected image (9a, 10a) synchronized with the conveying speed of each conveyor (6, 7). It becomes possible.

  The image processing unit (13) detects the paper edge (L) and the insertion (1) using each detected image (9a, 10a), and then between the paper edge (L) and the insertion (1). It is a means for calculating dimensions.

  The determination unit (14) determines whether the dimension between the long side (3) and the short side (4) and the clearance (1) is within a preset allowable range. It is means for performing pass / fail judgment of the insertion position.

  In addition, after transferring the determination result in the determination unit (14) to the control unit (not shown), the paper (2) may be automatically selected by the paper discharge unit (not shown).

  Next, according to the flowchart shown in FIG. 7, the penetration position inspection method using the penetration inspection apparatus (M) described above will be described.

  In step (hereinafter referred to as “st”) 10, a paper edge image (9 a) in which the paper edge (L) of the paper (2) is clear, and a clear image (10 a) in which the clear (1) is imaged with high contrast. ) In advance, the imaging condition of the paper edge imaging line camera (9) is set to an imaging condition that allows the paper edge (L) of the paper (2) to be clearly captured, and the The imaging condition is set to an imaging condition that allows the clearing (1) formed on the paper (2) to be taken clearly. In addition, about imaging conditions, it changes also with to-be-inspected object and illumination (8). Therefore, the operator needs to investigate in advance the imaging conditions that can clearly capture each image (9a, 10a) and to set in advance at the time of inspection.

  For example, each line camera (9, 10) has the same camera and imaging conditions, and each time the transport belt (7a) of the downstream conveyor (7) moves 0.2 mm, a one-dimensional image with a resolution of 0.2 mm. When the images (9a, 10a) are input and the conveyance speed of the paper (2) is 2 m / s and the illuminance of visible light emitted from the illumination (8) is relatively low, the paper edge imaging line By setting the exposure time of the camera (9) to 10 μs and the exposure time of the plow-up imaging line camera (10) to 90 μs, the clear long side (3) and the short side (4) and the clear penetration (1 ) Can be imaged respectively.

  As another setting example, each line camera (9, 10) has the same camera and imaging conditions, and each time the transport belt (7a) of the downstream conveyor (7) moves 0.2 mm, the resolution is 0.2 mm. When a one-dimensional image is input and each image (9a, 10a) is picked up, the paper edge is relatively high when the paper conveyance speed is 3 m / s and the illuminance of visible light emitted from the illumination (8) is relatively high. By setting the exposure time of the imaging line camera (9) to 5 μs and the exposure time of the penetration imaging line camera (10) to 60 μs, the clear long side (3) and the short side (4) are clearly clear. (1) can be imaged respectively.

  Next, in st11, uniform visible light is irradiated onto the sheet (2) from the illumination (8) attached between the upstream conveyor (6) and the downstream conveyor (7).

  Next, in st12, when the paper (2) approaching the imaging line of each line camera (9, 10) is detected by the photoelectric sensor (not shown), the paper edge imaging line camera (9) Imaging of the paper edge image (9a) in which the paper edge (L) is clearly imaged is started. In the paper edge imaging line camera (9), the transmitted light of the paper (2) by the illumination (8) and the illumination ( The paper edge image (9a) is picked up by receiving the direct light from 8).

  FIG. 8 is a schematic diagram showing a paper edge image (9a) captured by the paper edge imaging line camera (9). In the paper edge image (9a), the paper edge (L) is clearly captured. On the other hand, the gap (1) is imaged unclearly. Note that the clearance (1) is illustrated by a broken line for the sake of explanation, but in reality, it is unclearly captured as described above.

  Next, in st22, which is parallel to st12, the clear image (10a) in which the clear (1) is clearly captured by the clear imaging line camera (10) at the same timing as the start of imaging of the paper edge imaging line camera. The captured image (10a) is captured by receiving the transmitted light of the sheet (2) by the illumination (8) and the direct light from the illumination (8).

  FIG. 9 is a schematic diagram showing a penetration image (10a) captured by the penetration imaging line camera (10). The clear image (10a) is a clear image of the clear (1). On the other hand, the edge of the paper (L) is imaged unclearly due to the wraparound of light.

  Each detected image (9a, 10a) is preferably subjected to sub-pixel processing in order to detect a clearer image. Sub-pixel processing is an image processing method that makes it possible to determine the boundary with high accuracy by differentiating the luminance gradient in the vicinity of the boundary. When determining the boundary and position of an object, the detection (or measurement) accuracy of the boundary is determined. Is 1 pixel in the binarized image, but can be increased to 1 pixel or less by using the luminance gradient near the boundary of the object.

  The sheet (2) imaged by each of the line cameras (9, 10) has an imaging position (9, 10) of each line camera (9, 10) due to a conveyance error of the sheet (2) of the penetration inspection device (M). The input line is skewed by θ1 °, and the position of the D corner serving as the reference coordinate of the sheet (2) is shifted by X1 in the transport direction (v1) and Y1 in the direction (v2) perpendicular to the transport direction. Variations are seen in the condition. Note that the skew is that the sheet (2) is inclined obliquely during conveyance.

  FIG. 10 is a schematic diagram of a paper edge image (9a) in which a conveyance error of the paper (2) occurs. In FIG. 10, the direction (v2) perpendicular to the transport direction, that is, the direction of the imaging position (input line) of each line camera (9, 10) is the X axis, and the transport direction (v1) of the paper (2) is the Y axis. The four corners of the paper (2) are A, B, C, and D corners. In FIG. 10, when the image was captured by the paper edge imaging line camera (9), the image was captured at a position where the D corner was shifted by (X1, Y1). Further, the sheet (2) was imaged with the long side (3) skewed by θ1 °.

  In st12, the image processing unit (13) detects the paper edge (L) by binarizing the paper edge image (9a) with a preset threshold value, and detects the coordinates of the four corners from the paper edge (L). By using a known method, the D corner coordinates (X1, Y1) of the reference long side (3) and the skew (θ1) are calculated by the calculation method. Next, (−X1, −Y1) and −θ1 °, which are correction values for performing correction so that the calculated D corner is (0, 0) and θ1 ° is on the X axis, are calculated.

  In st23, the cut-in image (10a) is corrected using the correction value calculated in st13. FIG. 11 is a schematic diagram showing a method of correcting the cut-in image (10a). Note that in the cut-in image (10a), since the paper edge (L) is not clearly captured as described above, the paper edge (L) is illustrated by a broken line. In each line camera (9, 10), the same position of the paper (2) is imaged at the same timing. Therefore, the corrected image (10a) is corrected using the same correction value as that calculated in st13.

  FIG. 11A is a schematic diagram showing a cut-in image (10a). Since the paper edge (L) is not clearly picked up in the clear image (10a), the image shift (X1, Y1) and skew (θ1) cannot be calculated as in the paper edge image (9a). . Therefore, by using the correction value calculated in the paper edge image (9a) described above, correction can be performed in the same manner as the paper edge image (9a) as shown in FIG. 11B.

  In the image processing unit (13), as shown in the arrangement of FIG. 6, a deviation amount in the direction (v2) perpendicular to the conveyance direction of each line camera (9, 10) is recorded in advance. By subtracting, the coordinates of the D corner become (0, 0).

  In st24, the corrected image (10a ′) is subjected to pattern matching (correlation method) using a preset reference image (10b), and all of the images (1) in the paper (2) are detected. The coordinates (X ′, Y ′) are calculated.

  FIG. 12 is a schematic diagram illustrating a state in which pattern matching is performed. The penetration reference image (10b) is an image serving as an inspection reference when pattern matching is performed, and is a portion that is a feature point in the image of the penetration (1). In addition, the location used as a feature point refers to a portion with high contrast in the clearance (1). For example, when the clearance (1) is a person image, the eyes, mouth, shoulders, and the like. On the other hand, the portion having few feature points is a portion having a low contrast in the clearance (1), such as the center of the elbow or the center of the cheek.

  Regarding the selection of the penetration reference image (10b), the image of the penetration (1) is examined in advance, and one surface with the least variation is selected, and the clearance within the one surface or within the one surface (1 ) Must be set as the reference image (10b).

  In addition, in the clearance reference image (10b), the clearance reference coordinates (u) are set in advance. The clearance reference coordinate (u) is an arbitrary point representing the position of the clearance (1), and may be an arbitrary point such as a corner in addition to the center of gravity shown in the figure.

  In order to pattern match the penetration image (10a ′) and the penetration reference image (10b), the search area (W) is set for all 20 surfaces on which the penetration (1) is formed, Next, it is determined by pattern matching which part in the search area (W) has the highest similarity in the penetration reference image (10b). The search area (W) is a range of the position where the clearance (1) exists in the paper (2), and the location (1) in which the clearance (1) is previously formed in the paper (2) ( For example, if there are 20 planes, it is necessary to set pixels in each search area (W) (L1 × L2) in 20 planes).

  FIG. 13 is a schematic diagram showing the inserted image (10a ″) after pattern matching. Each of the slots (1) has a coordinate (X ′, Y ′). The coordinates (X ′, Y ′) of the clearance (1) calculated by pattern matching are not particularly limited as long as the coordinates can identify each clearance (1). An arbitrary point such as the center of gravity or corner of the gap (1) can be used as a coordinate.

  In st25, the distance between the paper edge (L) and the insertion (1) is calculated. The distance between the long side (3) and the short side (4), which are the paper edges (L), and the clearance (1) is multiplied by the resolution (X ′, Y ′) of each clearance (1). It is calculated by. Note that the resolution is a value indicating the size of one pixel in each image (9a, 10a) on the paper (2). In order to inspect with high accuracy, the resolution is desirably 0.2 mm or less.

  Further, the calculated resolution in the direction of the long side (3) of the paper (2) is reduced in accuracy due to the distortion of the lens of each line camera (9, 10). Is desirable.

  Finally, in st26, in the determination unit (14), the dimension between the long side (3) and the short side (4) and all the clearances (1) is a dimension that is a preset allowable range. Are compared to determine whether or not they are within the allowable range. Based on the pass / fail judgment, it is transferred to a control unit (not shown) of the penetration inspection device (M), and the paper (2) is automatically selected in the paper discharge unit (not shown). In addition, in the case where a waste paper is generated, the clearance inspection device (M) is stopped, or a marking device (not shown) is installed in a paper discharge unit (not shown), and before paper discharge. It is good also as a structure which marks on the waste paper.

DESCRIPTION OF SYMBOLS 1 Slow 2 Paper 2a Base material 3 Long side 4 Short side 6 Upstream conveyor 7 Downstream conveyor 6a, 7a Conveyor belt 6b, 7b Roller 8 Illumination 9 Paper edge imaging line camera 9a Paper edge image 10 Sucking imaging line camera 10a Included image 10b Included reference image 12 Encoder 13 Image processing unit 14 Judgment unit L Paper edge M Entry inspection device u Entry reference coordinate W Search area

Claims (3)

Formed on the paper from the paper edge using an inspection apparatus having at least a paper edge imaging line camera for imaging the paper edge of the paper and a penetration imaging line camera for imaging the penetration formed on the paper. In the method for inspecting the pouring position for inspecting the position up to the pouring,
Set the imaging conditions of the paper edge imaging line camera in advance to imaging conditions that allow the paper edge of the paper to be clearly captured,
The imaging condition of the squeeze imaging line camera is set to an imaging condition where the squeeze formed on the paper can be taken clearly,
After irradiating the surface of the paper with visible light, the transmitted light from the paper is detected, and the paper edge image and the squeezed image line camera respectively acquire the paper edge image and the squeezed image,
Detecting coordinates indicating the paper edge of the paper from the paper edge image;
Correcting the scraped image with reference to at least one side of coordinates indicating the paper edge of the paper detected from the paper edge image;
Pattern-matching the corrected cleaning image and a preset cleaning reference image, and detecting coordinates indicating the cleaning position in the paper;
Calculating the distance from the coordinate indicating the paper edge of the paper to the coordinate indicating the insertion position;
The calculated distance from the coordinates indicating the paper edge position in the paper to the coordinates indicating the paper insertion position in the paper, and the preset position in the paper from the coordinates indicating the paper edge position in the paper. And a determination of whether or not the position where the clearance is formed is accepted or not based on whether or not it is within the allowable range.   The imaging condition for clearly capturing the paper edge of the sheet and the imaging condition for clearly capturing the gap formed on the sheet are at least one of exposure time, aperture, and gain, or a combination thereof. The method for inspecting the clearance position described.   3. The penetration according to claim 2, wherein at least one of an exposure time, an aperture, and a gain is different between an imaging condition for clearly capturing the edge of the sheet and an imaging condition for clearly capturing the clearance formed on the sheet. Position inspection method.

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