JP2023060918A - Pattern position inspection method - Google Patents

Abstract

To provide a pattern inspection method in which the resolution of a line camera in a paper flow direction is precisely calculated for the position inspection of multiple patterns formed on a continuous sheet by a paper making machine, etc., and the pattern positions applied to the continuous sheet are inspected with high accuracy by the calculated resolution.SOLUTION: This invention discloses a pattern position inspection method that inspects the positions of a plurality of patterns formed on a continuous sheet in a paper making machine when the continuous sheet is dry and in a transportation state, the pattern position inspection method comprising: a step of imaging a predetermined area containing a plurality of patterns formed on a continuous sheet; a step of measuring the amount of movement of the continuous sheet to be imaged without contact; a step of calculating the resolution in the paper flow direction from the amount of movement; and a step of determining whether the pattern positions are good or bad.SELECTED DRAWING: Figure 11

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern position inspection method for inspecting, with high precision, the position of a stitch pattern or the like applied to paper continuously manufactured on a paper machine.

Recent developments in digital equipment such as scanners and color copiers have made it possible to produce sophisticated counterfeits of security media such as bills and passports. As one of the anti-counterfeiting measures, there is a plowing pattern. The squeezing pattern is a pattern that cannot be visually recognized under reflected light, but can be visually recognized only under transmitted light, and can be applied only at the stage of manufacturing paper. be. In addition to the stitched pattern, a printed pattern and anti-counterfeiting material such as thread may be applied during the paper manufacturing stage. Since these patterns and anti-counterfeiting techniques make it difficult to forge sophisticated security media, they need to be applied with high positional accuracy.

Such a patterned continuous paper is manufactured by a paper machine, and is divided into fourdrinier, drying, calendering, inspection, and winding sections from the upstream side to the downstream side of the paper conveying path of the paper machine. etc. In some cases, a printing section is provided between the fourdrinier section and the drying section. For example, in the fourdrinier portion, the wet paper web on the wire is provided with a pattern, and in the printing portion, the printed pattern is applied to the continuous paper in the wet paper state at a position synchronized with the paper web. The drying section applies heat to the wet paper to dry the paper, and the calendering section applies pressure to the surface of the paper immediately after drying to increase the smoothness of the paper. Then, the inspection unit performs a defect inspection for inspecting holes and foreign matter in the paper, and a position inspection for pruning patterns and printed patterns.

Regarding such a paper machine, Patent Document 1 discloses a technique for automatically controlling the expansion and contraction of continuously manufactured paper and improving the positioning of patterns such as plowing patterns and register marks applied to the paper. disclosed. This technology consists of an image sensor camera, a light source, and a counter, as well as a dimension measuring device consisting of a rotary encoder, a mark sensor, etc., installed at the place where the paper runs stably in the drying section to measure the dimension of the paper in the direction of flow. By providing a paper width measuring device to measure the width direction of the paper, it is possible to automatically measure and control the expansion and contraction of the paper at all times without sampling the paper and measuring the expansion and contraction of the paper, which was conventionally implemented. By doing so, it is possible to improve product quality and workability.

Conventionally, it has also been practiced to accurately inspect the positions of patterns on a paper machine. These pattern position inspections are inspections to ensure that the continuous paper manufactured by the paper machine is within the tolerance of the product standard when cutting the continuous paper manufactured by the paper machine to the predetermined size of the security medium. Measure the distance between the cross stitch pattern and the stitch pattern, the distance from the midpoint of the stitch pattern group calculated in the sheet unit area to each stitch pattern, and the distance between the stitch pattern and the printed pattern. , and determines whether the distance is within the product standard. Accuracy of pattern position inspection is extremely important in the production of continuously manufactured paper. If the inspection accuracy of the pattern position is low, the paper is determined to be good even though the patterns are greatly displaced from the appropriate positions. It is from.

In the fourdrinier section of the paper machine, the position of the pattern changes as the paper expands and contracts during drying in the drying section. Positional inspection of the pattern is performed in the inspection section after the drying section. Then, in the inspection section of the paper machine, the pattern position measurement data for each area judged to be good paper is stored, and by utilizing the measurement data in the subsequent cutting process, etc., a security medium that suppresses the pattern position. can be obtained. On the other hand, areas that have been judged to be defective paper by the inspection section of the paper machine are marked as defective paper by the inspection section, for example, and are removed from good paper by detecting the mark in the cutting process. .

A pattern position inspection device is generally composed of an LED illumination, a line camera, an encoder, an image processing section, and the like. When capturing an image of a pattern formed on the continuous paper, the continuous paper is irradiated with LED illumination, and a transmission image of the continuous paper is captured by a line camera to obtain a cut-in transmission image. Further, the encoder sends a line camera imaging signal to the image processing section in synchronization with the continuous paper being conveyed. This line camera imaging signal is a signal synchronized with the continuous paper being conveyed. Then, the image captured by the line camera is subjected to quality determination as to whether or not it is within the allowable range of the preset standard in the image processing unit.

The image processing unit, which determines whether the position of the stitch pattern is good or bad, detects the position of the stitch pattern by performing pattern matching on the transparent image of the continuous paper using a preset reference image of the stitch pattern. . Next, from the position coordinates of the detected squeezing pattern, the squeezing position is measured, and pass/fail judgment is performed depending on whether or not the position is within the allowable range. In addition, it is necessary to investigate and set the correct resolution of the line camera in the width direction and the flow direction in advance in this image processing unit. Specifically, the resolution of the line camera in the width direction is to take an image of a scale with high-accuracy marks printed on the paper transport path, count the number of pixels between the scale marks in the captured image, and calculate the number of pixels between the marks. is calculated by dividing the actual length of by the number of pixels between tick marks. In addition, the resolution of the line camera in the machine direction is obtained by actually measuring the distance between the patterns on the paper with a scale, then counting the number of pixels between the captured patterns, and calculating the actual distance between the patterns. is calculated by dividing by the number of pixels.

Since the line camera imaging signal needs to be synchronized with the continuous paper being conveyed, it is necessary to place the encoder on the continuous paper so that the rollers of the encoder that emits the line camera imaging signal come into direct contact with the paper being conveyed. there were.

Japanese Patent No. 1806540

In Patent Document 1 and the conventional pattern position inspection method, the rollers come into direct contact with the paper being conveyed, so there is a risk of damaging the paper. Therefore, as in the side view of the inspection unit shown in FIG. 12, it was necessary to make the rollers of the encoder contact the paper roll that rotates with the paper instead of directly contacting the paper. .
However, a general paper roll is an iron roll that rotates with the paper being conveyed, and has a smooth surface and a large rotational load, and the paper roll may slip on the paper being conveyed. When the paper roll slips, the rotation speed of the rollers of the encoder loses synchronization with the conveyed paper, and thus there is a problem that the measurement error of the pattern position in the flow direction increases.

For example, when the actual distance between patterns in the paper flow direction is 100.0 mm, the number of pixels of the line camera image taken between them is 1000, and the preset resolution is 0.1 mm/pixel, the pattern By multiplying 1000 pixels, which is the distance between the patterns, by 0.1 mm/pixel, the distance between the patterns is calculated to be exactly 100.0 mm.
However, although the paper roll slips and the paper is conveyed at a constant speed, the number of imaging signals from the encoder decreases. When the number of pixels is reduced to 900, the pattern interval length calculated by multiplying 900 pixels by 0.1 mm/pixel is 90.0 mm, which is 10 mm shorter than the actual length.

Further, since the continuous paper in the inspection section of the paper machine is wound at a constant peripheral speed in the winding section, it is always pulled in the direction of the winding section. , when the continuous paper stretches evenly at point A between the line camera imaging area and the downstream paper roll, the speed of the paper in the line camera imaging area decreases, and the line camera imaging signal from the encoder moves It is not synchronized with the continuous form. Therefore, there is a problem that the error in the position of the plowing pattern in the flow direction is large.

Accordingly, the present invention relates to a method for inspecting the position of a plurality of patterns formed on continuous paper by a paper machine or the like. By automatically updating the calculated resolution, the position of the pattern applied to the continuous paper can be inspected with high accuracy.

The pattern position inspection method of the present invention is a pattern position inspection method for inspecting the positions of a plurality of patterns formed on a continuous sheet of paper in a paper machine while the continuous sheet of paper is dried and transported on the paper machine,
capturing an image of a predetermined area including a plurality of patterns formed on the continuous paper;
Non-contact measurement of the amount of movement of the continuous paper in or near a predetermined area to be imaged,
Calculate the resolution in the paper flow direction by dividing the measured amount of movement of the continuous paper by the number of imaging signals per unit time,
A target pattern is detected from a captured image obtained by imaging, the number of pixels between the detected patterns is counted, the counted number of pixels is multiplied by the resolution to calculate the distance between the patterns, and the calculated distance between the patterns is calculated. is compared with a preset threshold to determine whether the pattern position is good or bad.

Further, the pattern position inspection method of the present invention is characterized in that the resolution is automatically updated periodically.

According to the present invention, the position of a pattern formed on a continuous sheet of paper manufactured by a paper machine or the like can be precisely calculated by using a non-contact laser speedometer, so that the position of the pattern can be inspected with high accuracy. can be done.

FIG. 1 shows a continuous sheet with a plow pattern on a paper machine; FIG. 4 is a side view of an apparatus (S) for carrying out the pattern position inspection method according to the present embodiment; FIG. 4 is a cross-sectional view of a line camera imaging area of continuous paper in the present embodiment; FIG. 4 is a cross-sectional view of a line camera imaging area of continuous paper in the present embodiment; FIG. 4 is a side view of a line camera imaging area in the embodiment; It is a schematic diagram which shows the principle of the laser speedometer in this Embodiment. It is an arrangement example of a non-contact laser speedometer in the present embodiment. FIG. 10 is a diagram showing the measurement timing of the line camera image signal and the movement amount of the continuous paper in the present embodiment; FIG. 3 is a diagram showing an example of arrangement of optical sensors according to the present embodiment; FIG. 10 is a diagram for explaining a method of calculating resolution according to the arrangement example of FIG. 9 in this embodiment; 3 is a flow chart of a pattern position inspection method according to the present embodiment; FIG. FIG. 10 is a side view for explaining a conventional pattern position inspection method;

A mode for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments described below, and includes various other embodiments within the scope of the technical ideas described in the claims.

(Embodiment)
FIG. 1 is a diagram showing a strip-shaped continuous paper (2) on which a plurality of patterns (1) are formed, which is an object to be inspected in the pattern position inspection method of the present invention. In this embodiment, a plurality of patterns (1) are arranged in the X direction, which is the width direction of the paper, and the Y direction, which is the flow direction of the paper. Also, the pattern (1) is formed in the region (3) enclosed by the dotted line, which will be cut in a post-process to form a sheet unit. In FIG. 1, for convenience of explanation, the region (3), which is a sheet unit, is indicated by a dotted line, but it does not actually exist. The continuous paper (2) is finally cut in a post-process to a standard size for a product form that is required for each sheet or from each sheet to become a security medium. In the present embodiment, as shown in FIG. 1, eight patterns (1) are arranged in a sheet unit area (3) surrounded by dotted lines. The number and arrangement of (1) are not limited to the example shown in FIG.

In this embodiment, the pattern (1) formed on the continuous paper (2) may be a stitched pattern, a printed pattern, a thread, a register mark, or the like. Further, the continuous paper (2) may be provided with a combination of pruning patterns, printed patterns, threads, register marks, and the like. In the present embodiment, the positional inspection of the printed pattern or the like uses the same method as the positional inspection of the cut-in pattern (1), so in the present embodiment, the cut-in pattern (1) will be described as an example.

The continuous paper (2) is a belt-shaped paper on which the pattern (1) is formed by a paper machine, and is manufactured by a fourdrinier paper machine, a cylinder paper machine, or the like. In the present embodiment, an example in which a dandy roll is used to form a plow-in pattern (1) on a continuous paper (2) made using a fourdrinier paper machine will be described, but the present invention is not limited to this. Instead, the pattern (1) may be formed by a press process, or by a circular net method.

A fourdrinier paper machine is composed of a fourdrinier section, a printing section, a drying section, a calendering section, an inspection section, a winding section, and the like (not shown) from the upstream side to the downstream side of the manufacturing process. In the Fourdrinier part, the wet paper on the wire is formed with a plowing pattern (1), passed through a drying part, an inspection part, etc., and wound up to form a paper roll.

The continuous paper (2) with the slit pattern (1) formed in the Fourdrinier part is inspected because the position of the slit pattern (1) changes due to the expansion and contraction of the paper due to the evaporation of moisture in the drying part. A positional inspection of the plowing pattern is performed in the part. Here, the inspection of the position of the cutout pattern (1) in the inspection unit is to inspect the positions between the cutout patterns (1) that have changed due to the expansion and contraction of the paper. For example, when determining whether or not the distance between adjacent stitch patterns (1) is within the product standard, as shown by the dotted line in FIG. The distance between the cutout pattern (1') and the cutout pattern (1''), and each cutout pattern (1) from the midpoint (4), which is the intersection point when connecting the cutout patterns with a straight line. It also includes the case of determining whether the distance to the product is within the tolerance of the product standard.

FIG. 2 shows a side view of a pattern position inspection apparatus (S) for carrying out the position inspection method of the present invention. The pattern position inspection device (S) includes at least an LED illumination (5), a line camera (6), an encoder (7), encoder rollers (12), a downstream paper roll (8), and an image processing section (9). , a non-contact laser velocimeter (13) and a controller (14). Comparing the side view of the pattern position inspection apparatus of the present invention in FIG. 2 with the prior art of FIG. ing.

As shown in FIG. 2, the transport path of the continuous paper (2) in the inspection section is determined by the arrangement of the paper rolls, and the continuous paper (2) is positioned above the upstream paper roll (9) and downstream paper rolls (9). 8). The paper roll (9) on the upstream side and the paper roll (8) on the downstream side are one iron roll commonly used for the continuous paper (2), and rotate together with the continuous paper (2). do.

In the present invention, the LED illumination (5) irradiates the entire surface of the continuous paper (2) in the width direction with high-intensity white light, and the LED illumination and the The line cameras are arranged facing each other with the continuous paper (2) interposed therebetween. By arranging in this way, the line camera (6) can capture a cut-in transmission image with less distortion and sufficient brightness and contrast. A line camera (6) receives an imaging signal from an encoder (7) and picks up an image of one line. In the present embodiment, a line camera imaging area (11) for capturing a paper transmission image by the line camera (6) is positioned substantially midway between the upstream paper roll (10) and the downstream paper roll (8). However, if the line camera imaging area (11) can be stably obtained, it is not limited to this.

In the above description, as shown in FIG. 2, the position of the slit pattern (1) is inspected, so the LED illumination (5) is arranged at a position facing the line camera (6) through the continuous paper (2). However, the LED illumination (5) may be installed at a position where a good captured image can be obtained by the line camera (6). For example, when photographing the printed pattern (1) formed on the continuous paper (2), the LED illumination (5) and the line camera (6) are placed on the side of the continuous paper (2) on which the printed pattern (1) is formed. The continuous paper (2) is irradiated with white light from the LED illumination (5) at an angle of about 45 degrees, and the line camera (6) is arranged perpendicular to the continuous paper (2). A reflected image of the continuous paper (2) can be captured.

Next, as shown in FIG. 2, the downstream paper roll (8) through which the continuous paper (2) passes is in contact with the roller (12) of the encoder at its upper portion. Most preferably, the continuous paper (2) and the encoder roller (12) are brought into direct contact in order to completely synchronize the encoder (7) with the amount of movement of the continuous paper (2). ) may damage the continuous paper (2), so in the present invention, the downstream paper roll (8) and the roller (12) of the encoder are brought into contact and synchronized. A line camera imaging signal emitted from the encoder (7) is a signal synchronized with the continuous paper being conveyed, and a signal synchronized with the rotation of the downstream paper roll (8). Also, the line camera imaging signal from the encoder (7) is common to the position inspection devices for a plurality of areas.
In this embodiment, the rollers (12) of the encoder are placed in contact with the paper roll (8) on the downstream side, but the rollers (12) of the encoder are placed in contact with the paper roll (10) on the upstream side. may

Next, the non-contact laser velocimeter (13) used in this embodiment will be described. As shown in FIG. 2, the non-contact laser speedometer (13) is provided near the paper transport path and measures the amount of movement of the continuous paper (2) passing through the line camera imaging area (11). In this specification, the term "near the paper transport path" means any position above, below, or oblique to the continuous paper (2) as long as it does not directly contact the continuous paper (2) being transported. Alternatively, it may be positioned upstream or downstream with respect to the continuous paper (2) being conveyed. This will be explained below.

FIG. 3 is a sectional view of the line camera imaging area (11) of the continuous paper (2) when the pattern position inspection device (S) of the present invention is viewed from the downstream side to the upstream side in the paper conveying direction. . For example, as shown in FIG. 3, when the non-contact laser speedometer (13) is located outside the field of view of the line camera (6), the image captured by the line camera (6) is captured by the laser beam (15). ) is not captured. Therefore, the captured image can be used not only for inspecting the position of the stitched pattern (1) but also for inspecting defects such as holes and stains in the continuous paper.

However, as shown in FIG. 4, the location where the non-contact laser speedometer (13) is arranged may be arranged within the imaging field of view of the line camera (6). In this case, since the laser light (15) from the non-contact laser velocimeter (13) is captured in the transmission image captured by the line camera (6), the captured image cannot be used for defect inspection, but the laser light ( 15), the position of the cut-in pattern (1) can be inspected by arranging it so that the cut-in pattern (1) to be inspected does not pass through.

Another example of the arrangement of the non-contact laser speedometer (13) will be explained based on the side view of the line camera imaging area (11) shown in FIG. As shown in FIG. 5, when the non-contact laser speedometer (13) is placed downstream of the line camera imaging area (11), the laser beam (15) is reflected in the image captured by the line camera (6). An image obtained by imaging, which is not imaged, can be inspected for defects such as holes and stains on the continuous paper (2). For the same reason, the non-contact laser speedometer (13) may be placed on the upstream side of the line camera imaging area (11) (not shown).

Next, the principle of the non-contact laser velocimeter (13) will be explained. FIG. 6 is a schematic diagram showing the principle of the non-contact laser velocimeter (13). In the non-contact laser velocity meter (13), when the two-axis laser beams (15) are crossed at an angle 2θ, the light and dark frequencies of the interference fringe generated at the crossing position of the laser beams (15) pass through it. It is a speedometer that uses the phenomenon that changes with the speed of an object. A laser Doppler velocimeter is used as the non-contact laser velocimeter (13).
A non-contact laser velocimeter (13) irradiates a laser beam (15) on the continuous paper (2) moving in the paper flow direction (Y direction) in the line camera imaging area (11), ) to measure the speed of the continuous paper (2). Then, the amount of movement of the paper is calculated by integrating the measured velocity over the measurement time. The movement amount is the distance that a predetermined position of the continuous paper (2) moves in the paper flow direction (Y direction) per unit time. During the position inspection, the non-contact laser velocity meter (13) constantly transmits the calculated amount of movement of the continuous paper (2) to the controller (14).

FIG. 7 is a layout diagram of a non-contact laser speedometer (13) when a plurality of stitch patterns (1) are arranged on a continuous sheet (2). In the present invention, the non-contact laser speedometer (13) is installed at least in one place with respect to the conveyed continuous paper (2). If the area is large, a plurality of non-contact laser speedometers (13) may be arranged for each area. As a result, even if there is a slight misalignment in the plow-in pattern (1) due to differences in paper expansion and contraction in the areas of the continuous paper (2) (center and both ends in the width direction), the amount of movement can be accurately calculated for each area. Since the measurement can be performed at a constant distance, the position inspection accuracy can be further improved.

Next, the controller (14) in this embodiment will be described. The controller (14) receives the line camera imaging signal from the encoder (7) and the amount of movement of the continuous paper (2) measured by the non-contact laser speedometer (13), as shown in FIG. By dividing the movement amount of 2) by the number of line camera imaging signals, the flow direction resolution of the position inspection device for the cut-in pattern (1) is calculated. In this embodiment, the controller (14) can receive the line camera imaging signal from the encoder (7) and the amount of movement of the continuous paper (2) measured by the non-contact laser speedometer (13). It doesn't matter where you are. In this embodiment, the resolution of the line camera 6 in the flow direction is calculated by the controller 14, but the function of the controller 14 may be provided in the image processing section 9.

FIG. 8 is a diagram showing the measurement timing of the line camera imaging signal and the movement amount of the continuous paper (2). The line camera (6) picks up an image of one line with a preset exposure time when the signal from the encoder (7) rises. The non-contact laser speedometer (13) measures the movement amount of the continuous paper (2) by integrating the measured speed of the continuous paper (2) over the measurement time.
The controller (14) stores the number of imaging signals (P1) of the line camera (6) from a preset time (T0) to time (T1) and the movement amount (L1) of the continuous paper (2), and stores T1 After the time elapses, the controller (14) quickly divides the amount of movement (L1) of the continuous paper (2) by the number of line camera imaging signals (P1), thereby changing the flow direction of the line camera (6) for a certain period of time. Calculate resolution.

In addition, as shown in FIG. 9, in the vicinity of the line camera imaging area (11), only the pruning pattern (18) located on the most positive side in the X direction and Y direction in the area (3) is detected. By providing an optical sensor (17) or the like for detecting the pruning pattern (18) at the position where the pruning pattern (18) located on the most plus side passes through, it is possible to calculate the resolution in the flow direction in a certain section. This will be explained with reference to FIG. 10. A signal of the stitch pattern (1) detected by the optical sensor (17) is sent to the counter (19). By comparing the pattern of the four continuous detection signals from the optical sensor (17) with the pattern of the detection signal from the optical sensor (17), the pruning pattern (18) located on the most positive side in the X direction is identified and signaled. (S0) and signal (S1) to the controller (14). In the controller (14), the moving amount (L2) of the continuous paper (2) between the signal (S0) and the signal (S1) is divided by the number of line camera imaging signals (P2) to obtain the resolution in the flow direction of the area. can be calculated.
In the above description, the method of detecting the plow-in pattern (1) located on the most positive side in the X direction was explained. A plowing pattern (1) exceeding the range can be detected.

The controller (14) transmits to the image processing section (9) the resolution in the flow direction calculated within a certain period of time or within a certain interval. In the image processing section (9), the image picked up by the line camera (6) for each line is formed as a two-dimensional image, and the resolution sent from the controller (14) is used to create a squiggle pattern (1 ) can be calculated to determine the quality of the plow-in pattern position.

Specifically, in the image processing section (9), the stitched pattern (1) to be subjected to position measurement is detected from the line camera-captured image captured by the line camera, mainly using pattern matching. Next, the number of pixels between the detected patterns is counted, and the distance between the patterns is calculated by multiplying the counted number of pixels by the resolution calculated above. Then, the calculated distance between patterns is compared with a preset threshold value (permissible range), and the pattern position is judged to be good or bad depending on whether the distance is within the threshold value.

In the image processing section (9), the resolution is automatically updated periodically. Further, while the resolution is being updated, the position inspection of the clearance pattern (1) continues by using the pre-update resolution.

(Pattern position inspection method)
Next, a pattern position inspection method using the pattern position inspection apparatus (S) described above will be described. FIG. 11 is a flowchart of the pattern position inspection method according to the embodiment of the present invention. As shown in FIG. 11, the pattern position inspection method according to the embodiment of the present invention includes at least an imaging step (Step 1), a movement amount measurement step (Step 2), a resolution calculation step (Step 3), and a pattern inspection step (Step 4). . Each step will be described below.

(Imaging step (Step 1))
In the imaging step (Step 1), the continuous paper (2) being conveyed is imaged using a line camera (6) or the like to capture an image of the pruning pattern (1). At that time, in order to obtain a good captured image of the stitched pattern (1), the shooting conditions are adjusted in advance, such as the appropriate lighting such as the LED lighting (5), the amount of irradiation, the position of the line camera (6) and the lighting, etc. It is desirable to keep

(Moving amount measurement step (Step 2))
In the moving amount measuring step (Step 2), the moving amount of the continuous paper (2) in or near the predetermined area to be imaged in the imaging step (Step 1) is measured in a non-contact manner using a non-contact laser velocimeter (13) or the like. Measure. In the measurement, as described in FIG. 4, the amount of movement within the imaging field of view in the imaging step (Step 1) may be measured, or as described in FIG. You may measure the movement amount of the area|region which deviated from. It should be noted that the movement amount measurement step (Step 2) should be performed at a position that does not come into direct contact with the conveyed continuous paper (2) with high measurement accuracy of the non-contact laser speedometer (13).
Further, as shown in FIG. 7, when the width of the continuous paper (2) is wide, the movement amount may be measured for each area. This makes it possible to accurately measure the amount of movement even when there is a slight misalignment in the plow-in pattern (1) due to the difference in expansion and contraction of the paper in the areas of the continuous paper (2) (center and both ends in the width direction). Therefore, it is possible to further improve the position inspection accuracy.

(Resolution calculation step (Step 3))
In the resolution calculation step (Step 3), the movement amount of the continuous paper (2) in the predetermined area measured in the movement amount measurement step (Step 2) is divided by the number of imaging signals per unit time to obtain the paper flow direction of the line camera. Calculate the resolution of Specifically, as shown in FIG. 2, the controller (14) receives the line camera imaging signal from the encoder (7) and the movement amount of the continuous paper (2) measured by the non-contact laser speedometer (13). . Then, in the controller (14), the moving amount of the continuous paper (2) is divided by the number of line camera imaging signals, thereby calculating the flow direction resolution of the position inspection device for the pruning pattern (1).

(Pattern inspection process (Step 4))
In the pattern inspection step (Step 4), the position of the trim pattern in the captured image is inspected. Specifically, first, the resolution in the flow direction calculated in the resolution calculation step (Step 3) is transmitted from the controller (14) to the image processing section (9).
Further, in the image processing section (9), the stitch pattern (1) to be subjected to position measurement is detected from the captured image captured in the image capturing step (Step 1). An existing method such as pattern matching can be used to detect the trimming pattern (1). Next, the number of pixels between the detected patterns is counted, and the counted number of pixels is multiplied by the resolution calculated above to calculate the distance between the patterns. Then, the calculated distance between patterns is compared with a preset threshold value (permissible range), and the pattern position is judged to be good or bad depending on whether the distance is within the threshold value. In the present embodiment, an example of determining the quality of the position between the stitched patterns (1) is shown, but the present invention is not limited to this, and can be performed between arbitrary patterns or from the edge of the continuous paper (2). It can be used for various examples such as the position to the pattern. The above is the description of the flow of the pattern position inspection method according to the embodiment of the present invention.

According to the present invention, even if the paper roll (7) slips, the resolution is automatically updated on a regular basis, so errors in the position inspection of the cutout pattern (1) can be kept small.

In the present embodiment, when the amount of slippage of the downstream paper roll (8) constantly changes, the resolution of the position inspection device for the pruning pattern (1) is constantly updated. ) becomes complicated. Therefore, a threshold for the amount of change in resolution is set in advance in the controller (14), and only when the threshold is exceeded, the resolution in the flow direction can be transmitted to the image processing section (9).

For example, when the resolution change threshold is ±0.000010 mm/, when the downstream paper roll (8) slips and the flow direction resolution changes from 0.1000000 mm/pixel to 0.100015 mm/pixel , the resolution is transmitted from the controller (14) to the image processing section (9) and updated. However, for example, when the resolution changes from 0.1000000 mm/pixel to 0.100008 mm/pixel, the changed resolution is smaller than the threshold, so the resolution can be set not to be transmitted to the image processing unit (9). .

1 Pattern (Skeined pattern, printed pattern)
2 Continuous paper 3 Sheet-based area 4 Middle point 5 LED illumination 6 Line camera 7 Encoder 8 Downstream paper roll 9 Image processing unit 10 Upstream paper roll 11 Line camera imaging area 12 Encoder roller 13 Non-contact laser speedometer 14 Controller 15 Laser light 16 Scattered light 17 Optical sensor 18 Plow pattern located on the most positive side

Claims (2)

A pattern position inspection method for inspecting the positions of a plurality of patterns formed on a continuous paper in a paper machine while the continuous paper is dried and transported on the paper machine, comprising:
capturing an image of a predetermined area including a plurality of patterns formed on the continuous paper;
non-contact measurement of the amount of movement of the continuous paper in or near the predetermined area to be imaged;
calculating the resolution in the paper flow direction by dividing the measured amount of movement of the continuous paper by the number of imaging signals per unit time;
A target pattern is detected from the captured image obtained by the imaging, the number of pixels between the detected patterns is counted, and the counted number of pixels is multiplied by the resolution to calculate the distance between the patterns. and comparing the calculated distance between the patterns with a preset threshold to determine whether the pattern position is good or bad.
2. The pattern position inspection method according to claim 1, wherein said resolution is automatically updated periodically.

Images