JP5939576B2 - Paper sheet identification device - Google Patents

Description

  The present invention relates to a paper sheet identification device that performs authenticity determination of paper sheets such as banknotes and cash vouchers. In particular, the present invention relates to a paper sheet identification device that performs authenticity determination based on a micro pattern (line pattern) provided on a paper sheet.

  In various devices that allow handling of banknotes, such as vending machines, only proper banknotes are accepted based on the authenticity determination of banknotes. Conventionally, the authenticity judgment of a banknote is performed based on the printing pattern printed on the banknote, the color of printing, or the like. By the way, in the current banknote, a micro pattern (also referred to as a “multi-line pattern”) in which a large number of fine lines are written side by side, and characters and figures are viewed as a latent image by slightly shifting the interval between the fine lines. Has been.

  Conventionally, the authenticity determination of a banknote has been confirmed by whether or not the latent image can be visually recognized when the micropattern region is viewed, that is, by human eyes.

  Patent Document 1 discloses a paper sheet authenticity determination apparatus that performs authenticity determination on the micropattern by the apparatus. In this authenticity determination device, the transmitted light of the paper sheet is converted into an electric signal with a resolution of a cycle having a smaller interval than the shift amount of the uneven linear pattern in the line image portion of the latent image pattern character or figure. It is characterized in that a bright and dark line pattern corresponding to the uneven shape is obtained.

Japanese Patent No. 4909696

  As described in Patent Document 1, the micro pattern (light-dark line pattern) can be confirmed by irradiating light on one surface of the paper sheet and observing the transmitted light transmitted through the paper sheet. Is possible. However, when light is transmitted through the paper sheet, light scattering occurs on the surface and inside of the paper sheet, and it becomes a noise component when receiving light, which makes it difficult to observe the micropattern. It was. Further, most of the banknotes to be identified by the paper sheet identifying apparatus have folds and wrinkles, and the light scattering becomes more remarkable due to such folds and wrinkles.

Therefore, the paper sheet identification apparatus according to the present invention is characterized by the following matters.
In a paper sheet identification device for identifying a paper sheet having a micro pattern configured by arranging a plurality of fine lines,
Conveying means for conveying the paper sheet;
A light emitting element that emits light to one surface of the paper sheet transported by the transport means;
A light receiving element that receives transmitted light from the other surface of the paper sheet transported by the transport means;
A first slit located between the light receiving element and the light receiving element having an opening on a line segment connecting the light emitting element and the light receiving element, and being conveyed by the conveying means;
An opening on a line segment connecting the light emitting element and the light receiving element, and a second slit located between the first slit and the light receiving element;
Control means for determining the presence or absence of the micropattern based on transmitted light from the other surface of the paper sheet received by the light receiving element ;
The length of the first slit and the second slit in the transport direction of the transport means is smaller than the width of the fine line of the micro pattern to be identified or the interval between the fine lines. To do.

Furthermore, in the paper sheet identification apparatus according to the present invention,
The lengths of the first slit and the second slit in the transport direction of the transport means are less than 80% of the width of the fine line or the interval between the fine lines.

In addition, the paper sheet identification device according to the present invention includes:
In a paper sheet identification device for identifying a paper sheet having a micro pattern configured by arranging a plurality of fine lines,
Conveying means for conveying the paper sheet;
A light emitting element that emits light to one surface of the paper sheet transported by the transport means;
A light receiving element that receives transmitted light from the other surface of the paper sheet transported by the transport means;
A first slit located between the light receiving element and the light receiving element having an opening on a line segment connecting the light emitting element and the light receiving element, and being conveyed by the conveying means;
An opening on a line segment connecting the light emitting element and the light receiving element, and a second slit located between the first slit and the light receiving element;
Control means for determining the presence or absence of the micropattern based on transmitted light from the other surface of the paper sheet received by the light receiving element;
The length between the first slit and the second slit is at least twice the width of the fine line or the interval between the fine lines.

Furthermore, the paper sheet identification device according to the present invention is:
Frequency conversion information is generated by frequency conversion of a light reception output signal output from the light receiving element, and the presence or absence of the micropattern is identified based on the frequency conversion information.

Furthermore, the paper sheet identification device according to the present invention is:
The presence or absence of the micropattern is identified based on a value in a predetermined frequency region of the frequency conversion information.

Furthermore, the paper sheet identification device according to the present invention is:
The presence / absence of the micropattern is identified based on a second frequency domain value with respect to a first frequency domain value of the frequency conversion information.

  According to the paper sheet identification apparatus of the present invention, the first slit and the second slit having openings on the line segment connecting the light emitting element and the light receiving element are provided in the front stage of the light receiving element that receives the transmitted light of the banknote. In this way, it is possible to suppress the influence of scattered light generated on the surface and inside of the banknotes, and the folding and wrinkling of banknotes, and to improve the identification accuracy of micropatterns to be identified. In addition, since the light incident on the banknote does not require high accuracy, it is possible to reduce manufacturing costs, labor, and maintainability.

The figure which shows the surface of the banknote (paper sheets) used by embodiment of this invention The top view which shows the mode of the banknote conveyance in the paper sheet identification device which concerns on embodiment of this invention. The figure explaining the state of scattering in the transmitted light of paper The figure explaining an example for scattering suppression in the transmitted light of paper sheets Side sectional view which shows the structure of the paper sheet identification device which concerns on embodiment of this invention Side sectional view which shows the structure of the sensor part which concerns on embodiment of this invention The block diagram which shows the control structure of the paper sheet identification device which concerns on embodiment of this invention. The flowchart which shows the micro pattern identification process which concerns on embodiment of this invention The figure for demonstrating numerical verification about the space | interval of the 1st slit and 2nd slit in the sensor part which concerns on embodiment of this invention. The figure which shows the light reception output signal which concerns on embodiment of this invention (a fine line is a light emitting element side) The figure which shows the light reception output signal which concerns on embodiment of this invention (a fine line is a light emitting element side) The figure which shows the light reception output signal when there is one slit (the fine line is the light emitting element side) The figure which shows the light reception output signal when there is one slit (the fine line is the light receiving element side) The figure which shows the frequency conversion information which concerns on embodiment of this invention

  Now, an embodiment of the paper sheet identification apparatus according to the present invention will be described. FIG. 1 is a diagram illustrating the surface of a banknote (paper sheet) that is an identification target in the embodiment of the present invention. In the paper sheet identification apparatus according to the present invention, the paper sheet to be identified is intended for various paper sheets having a micro pattern such as various securities such as gold vouchers, securities, and coupons in addition to such banknotes. Is possible.

  The banknote shown in FIG. 1 is a diagram showing the surface of a current thousand-yen bill as an example of paper sheets, and a watermark region B2 is provided at the center. A micro pattern region is formed at the lower left of the thousand yen bill. This micro pattern (also referred to as “line pattern”) has a line width of about 0.08 mm to 0.10 mm and long fine lines in the vertical direction, and substantially equal intervals in the horizontal direction (about 0.08 to 0.10 mm). Latent image patterns (characters of “1000” in the current thousand-yen bill) are formed by arranging the patterns between the fine lines slightly. The paper sheet identification device of the present invention determines the authenticity of a paper sheet by identifying the presence or absence of the micropattern.

  FIG. 2 is a top view showing a state of banknote conveyance in the paper sheet recognition apparatus 1 according to the embodiment of the present invention. FIG. 2 shows a state in which a banknote B (the same banknote B as that in FIG. 1) to be identified is conveyed to the paper sheet identification apparatus 1. The figure shows a top view of the lower structure of the paper sheet identification device 1.

  In the paper sheet identification apparatus 1, driving rollers 42A to 42D using the banknote B as a conveying unit are provided. The banknote B that has arrived at the banknote recognition apparatus 1 by another transport means or the like is sandwiched between the drive rollers 42A to 42D and the opposing rollers 43A to 43D facing each other, and the upper and lower portions of the banknote B are sandwiched between the driving rollers 42A to 42D. It is conveyed in the left direction. In the paper sheet identification device 1, two sensor units 20 </ b> A and 20 </ b> B for identifying the micropattern of the banknote B are provided on one of the transport paths that form the transport path of the banknote B. In the lower configuration of the present embodiment, the light receiving side configuration is arranged in the sensor units 20A and 20B.

  When the bill B passes through the paper sheet identification device 1 in the direction as shown in the figure, the presence or absence of the micro pattern is identified by one of the two sensor units 20A and 20B. In the case of the bill B insertion direction as shown in the figure, light is irradiated on the side on which the micropattern is printed, and transmitted light is received by the sensor unit 20A located below. When the bill B is turned upside down depending on the insertion direction of the bill B, the front and back of the bill B may be reversed. In each case, the passing position of the micropattern region B1 and the printing side of the micropattern region B1 are different. It becomes. In the paper sheet identification device 1, by detecting the insertion direction of the banknote B, which of the sensor units 20A and 20B is used for micropattern identification and the identification process of the sensor units 20A and 20B to be used are switched. I am going to do that.

Now, the method and problem of micro pattern identification will be described with reference to FIGS. FIG. 3 is a diagram showing a micro-pattern identification configuration using transmitted light, and is a cross-sectional view seen from the cross-sectional direction of the banknote. In this figure, the fine line printing part B1a (the part on which the ink constituting the fine line is placed) that forms the micro pattern is located on the light emitting element 21 side. The light emitted from the light emitting element 21 enters one side of the bill B. At this time, the light reaching the bill B is shielded by the fine line printing unit B1a. On the other hand, the light that reaches between the fine line printing parts B1a passes through the bill B and enters the light receiving element 23 side. At this time, light scattering occurs inside and on the surface of the bill B, and scattered light is incident on the light emitting element 23 in addition to the regular light. In an actual paper sheet identification device, the scattered light incident on the light receiving element 23 becomes even more prominent due to the folding or wrinkling of the bills B and the waviness during conveyance.

  Such scattered light goes around the dark area formed by the fine line printing portion B1a and appears as an unnecessary noise component in the signal for micropattern identification output from the light receiving element 23. When an experiment was performed with an actual paper sheet identification device 1, the signal output from the light receiving element 23 was not a clean waveform having a predetermined interval, and was not suitable for identifying a micro pattern. Although the signal-to-noise ratio of the signal has been improved by increasing the light emission intensity of the light emitting element 21, the amount of scattered light increases with respect to the dark region, and thus cannot solve the above-described problem. It was.

  As a solving means for suppressing such scattered light, it is conceivable to irradiate light from the light emitting element 21 through an optical system. FIG. 4 shows a configuration in which an optical system F is provided on the light emitting element 21 side in order to suppress scattering in the transmitted light of the paper sheet. In such a form, the light emitted from the light emitting element 21 is collected by the optical system F and enters the light receiving element 23. By using the optical system F in this way, it is possible to suppress scattered light generated in the bill B. However, in such a form, it is difficult to effectively suppress scattered light unless the optical system F must be used and the optical system F is properly aligned.

  In the form employing the optical system F as shown in FIG. 4, it is possible to suppress scattered light, and providing the optical system F increases the cost. Also, in the paper sheet identification device 1, in order to remove jammed paper sheets, an opening / closing mechanism is often adopted for the paper sheet transport path. In such an opening / closing mechanism, there is a possibility that a positional deviation occurs between the configuration on the light emitting element side and the configuration on the light receiving element side when opening and closing. In the configuration employing the optical system F that requires strict alignment, there is a problem that the light emitted from the light emitting element 21 does not reach the light receiving element 23 when such a positional shift occurs.

  In view of such problems, an object of the present invention is to provide a paper sheet identification device that suppresses scattered light with a simple configuration and identifies a micropattern.

  FIG. 5 is a side cross-sectional view showing the configuration of the paper sheet identification apparatus according to the embodiment of the present invention. 2 is a cross-sectional view of the paper sheet identification device 1 of FIG. 2 as viewed from the side and cut near the sensor unit 20A. The paper sheet identification apparatus 1 is configured to include a transport unit and a sensor unit 20. In addition, it has a transport means, control of the sensor unit 20, and control means for identifying the presence or absence of a micro pattern.

  FIG. 5 shows two drive rollers 42A and 42B. Opposing rollers 43A and 43B are arranged to face the driving rollers 42A and 42B. The driving rollers 42A and 42B are rotated in the direction of the arrow shown by driving means such as a motor. Further, the opposing rollers 43A and 43B are arranged at positions where they come into contact with the driving rollers 42A and 43B, and convey the bill B inserted into the paper sheet identification device 1 in the left direction in the figure.

In the paper sheet identification device 1, a conveyance path through which the bill B passes is formed by two opposed conveyance path walls 11A and 11B. A light receiving element 23 disposed on the substrate 24 is disposed on one of the transport paths (on the transport path wall 11A side). For the light receiving element 23, a photodetector (PD) capable of detecting the intensity of the received transmitted light is used. Further, on the other side of the transport path (on the transport path wall 11B side), a light emitting element 21 (using an LED in this embodiment) disposed on the substrate 22 is disposed. The light emitted from the light emitting element 21 passes through the bill B conveyed in the conveying path, is received by the light receiving element 23, and is converted and output as a light reception output signal. The light reception output signal output from the light receiving element 23 is used for detection of a micro pattern by a control means (not shown).

  FIG. 6 is a side sectional view showing details of the sensor unit 20 of the paper sheet identifying apparatus 1, and is an enlarged view of the sensor unit 20 of FIG. An opening 111 is provided in the transport path wall 11B, and guides light emitted from the light emitting element 21 to the side of the bill B transported in the transport path. As a configuration on the light receiving side, a first slit forming plate 26 and a second slit forming plate 27 are provided in addition to the light receiving element 23 described above. Each of the first slit forming plate 26 and the second slit forming plate 27 is provided with a first slit 261 and a second slit 271 in order to receive light irradiated from the light emitting element 21 (transmitted light of the bill B). ing. In the present embodiment, the periphery of the first slit forming plate 26 and the second slit forming plate 27 is connected by a connecting portion 29 to form a unit. The first slit 261 and the second slit 271 are formed in each first slit forming plate 26 and the second slit forming plate 27 so as to have an opening on a line segment connecting the light emitting element 21 and the light receiving element 23. By passing through these two slits 261 and 271, the transmitted light arriving at the light receiving element 23 is in a state in which the scattered component is suppressed, and the transmitted light near the micropattern to be identified is effectively received. Light can be guided to the element 23 side.

  In the present embodiment, the light receiving side ribs 25 </ b> A and 25 </ b> B are provided around the first slit 261 in order to suppress the flapping (position fluctuation) of the bill B in the vicinity of the micro pattern identification region. By providing the light receiving side ribs 25A and 25B, the width of the conveyance path in the vicinity of the micro pattern identification area can be narrowed, and the bill B can be stabilized. In this embodiment, the width L2 of the conveyance path is 1.2 mm, and the heights of the light receiving side ribs 25A and 25B are 0.4 [mm]. Therefore, the width L1 of the conveyance path through which the bill B can pass is 0.8 [mm].

  In the present embodiment, the width W1 of the light receiving element 23 is 1.5 [mm], and the opening width W2 of the first slit forming plate 26 and the second slit forming plate 27 with respect to the banknote progression direction is 0.05 [mm]. The distance L3 between the first slit forming plate 26 and the second slit forming plate 27 is about 1 [mm].

  As described above, in the paper sheet identification apparatus 1 according to the present embodiment, by using the two slits 261 and 271, the influence of scattered light incident on the light receiving element 23 is suppressed, and the identification accuracy of the micro pattern to be identified is improved. It is possible to improve. Furthermore, the light incident on the bill B does not need an optical system as described with reference to FIG. 4, or a simple optical system may be used, and the manufacturing cost can be reduced. As for the light emitting element 21, it is possible to adopt a relatively low-cost cannonball-type LED (LED having a light-emitting surface having a cannonball shape) as shown in FIG. It becomes possible. Further, the positioning of the light emitting element 21, the light receiving element 23, the first slit 261, and the second slit 271 can be easily performed, and labor during manufacturing and maintenance can be reduced.

  FIG. 7 is a block diagram showing a control configuration of the paper sheet identification apparatus according to the embodiment of the present invention. The paper sheet identification apparatus 1 of the present embodiment includes a sensor unit 20 including a light emitting element 21, a light receiving element 23, and the like, a banknote transport unit 40 as a banknote transport unit, and a control unit 30 as a control unit. . The light reception output signal output from the light receiving element 23 of the sensor unit 20 is amplified by the amplifier 28 and output to the control unit 30. The banknote transport unit 40 that transports the banknote B includes an encoder 41 that is provided in any one of the motor 42 and the drive rollers 42A to 42D as drive units that rotationally drive the drive rollers 42A to 42D and detects the amount of rotation. It is configured. The amount of rotation output from the encoder 41 is converted into the conveyance speed of the bill B using various conditions such as the diameter of the drive roller on the control unit 30 side.

  The control unit 30 includes a CPU as a central processing unit, a program, and a ROM and RAM as storage means for storing various data. The control unit 30 drives and controls the drive unit 42, the banknote speed detection unit 33 that detects the banknote B transport speed based on the rotation amount output from the encoder 41, and the banknote B transport time. A timer counter 34 for counting is provided. The A / D converter 31 digitizes the light reception output signal output from the amplifier 28, the transport speed of the bill B output from the transport speed detection unit 33, and the transport time of the bill B output from the timer counter 34, thereby micropattern determination unit 32. Output to (calculation unit). The micropattern determination unit 32 determines the micropattern area B1 of the banknote B based on the transport speed and the transport time of the banknote B, and the presence / absence of the micropattern based on the received light output signal acquired for the micropattern area B1. Determine.

  In addition, the relative position of the micro pattern with respect to the conveyance path varies depending on the insertion direction of the bill B as described above. Therefore, in the paper sheet identification apparatus 1, the insertion direction of a banknote is determined with various sensors, and the position corresponding to the insertion direction is determined. In FIG. 7 and the like, a configuration specialized for micro pattern identification is described. However, in the paper sheet recognition apparatus 1, a banknote B (paper sheet) is based on other characteristics of the banknote B by a sensor (not shown). Class)).

  FIG. 8 is a flowchart showing a micro pattern identification process according to the embodiment of the present invention. When it is detected that the bill B is inserted into the paper sheet identification device 1, the execution of the micro pattern identification process is started. First, the insertion direction of the banknote B is determined by a sensor (not shown) that determines the insertion direction of the banknote B (S101). Next, the position of the micro pattern on the banknote B is determined based on the insertion direction of the banknote B determined in S101 (S102). As described with reference to FIG. 2, the positional relationship (vertical position, front and back positions of the fine line printing unit B1a) of the micro pattern area B1 with respect to the paper sheet identification device 1 differs depending on the insertion direction of the bill B. The position of the micro pattern detected in S102 indicates which sensor unit 20A, 20B provided in the paper sheet identification device 1 is used to detect the micro pattern, and which surface the fine line printing unit B1a detects. It is used to change the threshold value for discrimination depending on whether it is located in the position.

  The control unit 30 acquires a light reception output signal output from one of the sensor units 20A and 20B based on the position of the micro pattern determined in S102, and stores it in a RAM or the like in the control unit 30. The presence / absence detection of the micro pattern is performed based on this light reception output signal. In this embodiment, the received light output signal is subjected to frequency conversion such as FFT to be converted into frequency conversion information (S104), and determination is made based on the characteristic value of the frequency conversion information. Further, in the present embodiment, in consideration of the fact that the fine line printing part B1a is located on the light emitting element 21 side or the light receiving element 23 side in the bill B insertion direction, the threshold for determination is changed.

  The characteristic value of the frequency conversion information can be set as follows, for example. FIG. 14 shows actual measurement values of frequency conversion information obtained by performing frequency conversion on the light reception output signal in the micropattern region B1. 14A shows a case where the fine line printing unit B1a is located on the light emitting element 21 side, and FIG. 14B shows frequency conversion information when the fine line printing unit B1a is located on the light receiving element 21 side. is there. In this embodiment, the micro pattern of the banknote B is observed as a peak near 1000 [Hz] from the relationship with the conveyance speed.

The micro pattern is detected based on a value obtained by integrating the frequency region (region A) in the vicinity of 1000 [Hz] in the frequency conversion information, and determining that the micro pattern is present on condition that the value is equal to or greater than a threshold value. Can be considered. In addition to such a determination mode, it is also possible to suppress erroneous determination due to variation in the SN ratio by referring to another frequency region (region B). For example, the micropattern detection condition may be that the ratio between the value obtained by integrating the region B and the value obtained by integrating the region A is equal to or greater than a threshold value. Noise components such as white noise are often superimposed on the entire frequency region, and by making a determination based on the ratio with other regions B in this way, erroneous determination due to variations in the SN ratio can be suppressed. It becomes possible.

  In the embodiment described above, (1) the integrated value of the frequency region (region A) near the frequency (1000 [Hz]) by the micro pattern, or (2) the integrated value of the region A and another frequency region (region B). Although the micro pattern is detected based on the ratio to the integrated value, the micro pattern can be detected using the maximum value (peak) in each of the regions A and B. That is, (1 ′) the maximum value in the frequency region (region A) near the frequency (1000 [Hz]) by the micro pattern, or (2) the maximum value in region A and the maximum value in other frequency regions (region B). It is good also as performing by ratio.

  Further, when FIG. 14A is compared with FIG. 14B, the peak value due to the micro pattern is the same as when the fine line printing portion B1a is located on the light emitting element 21 side (FIG. 14A). It can be seen that this is different from the case where it is located on the light receiving element 23 side (FIG. 14B). In order to cope with such a difference, it is possible to more accurately determine the micropattern by switching the threshold value for determination according to the position of the fine line printing unit B1a (depending on the insertion direction of the bill B). Become.

  Returning to the micropattern identification process of FIG. 8, the micropattern determination will be described. As described with reference to FIG. 14, in the present embodiment, the threshold for micropattern determination is different between when the fine line printing unit B1a is on the light emitting element 21 side and on the light receiving element 23 side. The position of the fine line printing unit B1a is based on the determination result of S102. When it is determined that the fine line printing unit B1a is on the light emitting element 21 side (S105: Yes), the micro pattern is determined using the first threshold value. If the characteristic value of the frequency conversion information converted in S104 (such as the value in the frequency domain corresponding to the micropattern) is equal to or greater than the first threshold (S106: Yes), it is determined that there is a micropattern (S108). On the other hand, when the characteristic value is smaller than the first threshold (S106: No), it is determined that there is no micro pattern (S109).

  When it is determined that the fine line printing unit B1a is on the light receiving element 23 side (S105: No), the micro pattern is determined using the second threshold value. If the characteristic value of the frequency conversion information converted in S104 is greater than or equal to the second threshold (S107: Yes), it is determined that there is a micro pattern (S108). On the other hand, when the characteristic value is smaller than the second threshold value (S107: No), it is determined that there is no micro pattern (S109). As described above, the micro pattern identification processing of the present embodiment takes into account the front and back positions of the micro pattern, and it is possible to perform more accurate micro pattern detection by changing the threshold according to the front and back positions. It has become.

Then, in the paper sheet identification apparatus 1 of this embodiment, the numerical verification of a structure is performed about the 1st slit 261 and the 2nd slit 271 which suppress a scattered light. In the micro pattern of the current bill B such as the thousand yen bill described in FIG. 1, the fine line width W0 is about 0.08 [mm] to 0.10 [mm], and the interval between the fine lines is also about 0. .08 [mm] to 0.10 [mm]. It is preferable that the length of each first slit 261 and second slit 271 in the bill conveyance direction (W2 in FIG. 6) be at least smaller than the fine line width and the fine line interval. Therefore, when the current banknote B is used as a micro pattern identification target, the upper limit of the length W2 is kept at 0.08 [mm]. More preferably, it is preferably less than 80% of the fine line width or the interval between fine lines. The lower limit of the length W2 is preferably set to 20% or more of the fine line width and the fine line interval because of insufficient light quantity. In the present embodiment, this length W2 is set to 0.05 [mm].

  Next, numerical verification is performed on the distance between the first slit 261 and the second slit 271 (L3 in FIG. 6). FIG. 9 is a schematic view showing the arrangement of the bills B, the first slits 26 and the second slits 27. Here, the distance L3 between the first slit forming plate 26 and the second slit forming plate 27 is numerically verified using the condition that the scattered light is most likely to enter the light receiving element 23.

  As described above, in the present embodiment, the width W2 of the first slit 261 and the second slit 271 is set to 0.05 [mm]. Moreover, since the width L2 of the conveyance path in FIG. 6 is set to 1.2 [mm], it can be seen that the distance L4 in which the banknote is conveyed most away from the light receiving element 23 is also 1.2 [mm]. . In FIG. 9, a right triangle indicated by a dark portion is a case where the center of the fine line printing portion B1a is located on the central axis of the first slit 261 and the second slit 271, and the light receiving element 23 is the fine line printing portion B1a. It is a position where light can be shielded. When the bill B is further positioned on the light emitting element 21 side (upward in the drawing), transmitted light from the periphery of the fine line printing portion B1a is incident on the light receiving element 23.

The width W0 of the fine line printing part B1a is 0.08 to 0.01 [mm] in the current banknote B. Here, the case where W0 is 0.08 [mm], which is the strictest condition, is verified. Since the right triangle shown by the dark line is a right triangle having the angle α in common, the following conditional expression holds.
tan α = W2 / L3 = W3 / (L3 + L4)
Here, W3 = W0 / 2 + W2 / 2,
When W0 = 0.08 [mm], W2 = 0.05 [mm], and L4 = 1.2 [mm] are substituted into the above conditional expression, L3 = 4 [mm] is calculated. Therefore, when the current micropattern of the bill B is set as an identification target, the theoretical lower limit value of the length L3 between the first slit 261 and the second slit 271 is 4 [mm].

  The lower limit value of the length L3 depends on the width W0 of the fine line printing portion B1a and the distance L4 between the first slit 26 and the bill B. Table 1 below summarizes the lower limit value of the length L3 when W0 and L4 are changed. The theoretical lower limit of the length L3 is 0.8 to 4 [mm].

The actual micropattern to be measured is a change in brightness, and in this embodiment, in particular, it is sufficient if the frequency characteristics of the micropattern can be acquired. Therefore, a length of 1/4 is allowed for this theoretical value. Therefore, for the current banknote B with W0 of 0.08 to 0.10 [mm], the actual lower limit value of the length L3 is 1/4 of the theoretical lower limit value of L3 described above, that is,. It is preferable to set it as 2-1 [mm]. Further, the upper limit value of the length L3 is preferably double the actual lower limit value, that is, about 0.4 to 2 [mm] in consideration of the SN ratio of transmitted light reaching the light receiving element 23. When the above is normalized based on the width between the fine lines of the micropattern to be identified as a reference, the lower limit of the length L3 is twice the width of the fine lines or the distance between the fine lines, The upper limit value is 25 times the width of the fine lines or the interval between the fine lines.

  10 and 11 show actual measurement results in the paper sheet identification apparatus 1 of this embodiment that employs two slits 261 and 271. FIG. 10 shows a measurement result when the fine line printing part B1a is located on the light emitting element 21 side, and FIG. 11 shows a measurement result when the fine line printing part B1a is located on the light receiving element 23 side. In each figure, (A) is a waveform of a region including a micro pattern, and (B) is an enlarged view of both time (horizontal axis) and voltage value (vertical axis) in the micro pattern. ing.

  As shown in each figure (A), both waveforms are flat without being affected by the scattered light of the bill B. In addition, each figure (B) shows that a waveform by a micro pattern can be acquired.

  In order to confirm the effect of adopting the two slits 261 and 271, the measurement results are shown in FIGS. 12 and 13 for the case where only one slit is used. FIG. 12 shows the measurement results when the fine line printing part B1a is located on the light emitting element 21 side, and FIG. 13 shows the measurement results when the fine line printing part B1a is located on the light receiving element 23 side. The vertical axis is the same scale as in FIGS. It can be seen that both waveforms are greatly wavy due to the influence of scattered light due to flapping of bills B and the like.

  In FIG. 14, frequency conversion (FFT) is performed on the waveform (FIG. 10, FIG. 11) acquired by the light receiving element 23 for the paper sheet identification apparatus 1 of the present embodiment that employs two slits 261 and 271. The result (frequency conversion information) of having performed is shown. FIG. 14A shows the measurement result when the fine line printing unit B1a is located on the light emitting element 21 side, and FIG. 14B shows the measurement when the fine line printing unit B1a is located on the light receiving element 23 side. It is a result.

  In both cases, it can be seen that a peak due to a micro pattern occurs in the vicinity of 1000 [Hz]. As described above, it is possible to identify the presence or absence of the micro pattern for the bill B based on the value in the frequency region near 1000 [Hz].

  As described above, according to the paper sheet identification apparatus 1 of the present embodiment, the two first slits 261 and the second slits 271 are provided, so that it is effective that the scattered light generated in the bill B enters the light receiving element 23. Therefore, it is possible to accurately determine the presence or absence of the micro pattern on the banknote B. Further, on the light emitting element 21 side, it is not necessary to provide a highly accurate optical system, and it is possible to reduce the cost in terms of adopting a bullet-type LED for the light emitting element 21. .

  Note that the present invention is not limited to these embodiments, and embodiments configured by appropriately combining the configurations of the respective embodiments also fall within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Paper sheet identification apparatus 11 ... Conveyance path wall 111 ... Opening 20 ... Sensor part 21 ... Light emitting element (LED)
22, 24 ... substrate 23 ... light receiving element 25A, B ... light receiving side rib 26 ... first slit forming plate 261 ... first slit 27 ... second slit forming plate 271 ... second slit 28 ... amplifier 30 ... control unit 31 ... A / D converter 32... Micro pattern determination unit (calculation unit)
33 ... Conveyance speed detection unit 34 ... Timer counter 35 ... Drive control unit 40 ... Bill conveyance unit 41 ... Encoder 41 ... Drive unit (motor)
42 ... Drive roller 43 ... Opposite roller B ... Banknote B1 ... Micro pattern area B2 ... Watermark area F ... Optical system

Claims (6)

In a paper sheet identification device for identifying a paper sheet having a micro pattern configured by arranging a plurality of fine lines,
Conveying means for conveying the paper sheet;
A light emitting element that emits light to one surface of the paper sheet transported by the transport means;
A light receiving element that receives transmitted light from the other surface of the paper sheet transported by the transport means;
A first slit located between the light receiving element and the light receiving element having an opening on a line segment connecting the light emitting element and the light receiving element, and being conveyed by the conveying means;
An opening on a line segment connecting the light emitting element and the light receiving element, and a second slit located between the first slit and the light receiving element;
Control means for determining the presence or absence of the micropattern based on transmitted light from the other surface of the paper sheet received by the light receiving element ;
The length of the first slit and the second slit in the transport direction of the transport means is smaller than the width of the fine line of the micro pattern to be identified or the interval between the fine lines. Yes Paper sheet identification device. Length of the second slit and the first slit in the conveying direction of the conveying means, the width of the fine line, or, in claim 1, wherein less than 80% of the spacing between the fine lines The paper sheet identification device described. In a paper sheet identification device for identifying a paper sheet having a micro pattern configured by arranging a plurality of fine lines,
Conveying means for conveying the paper sheet;
A light emitting element that emits light to one surface of the paper sheet transported by the transport means;
A light receiving element that receives transmitted light from the other surface of the paper sheet transported by the transport means;
A first slit located between the light receiving element and the light receiving element having an opening on a line segment connecting the light emitting element and the light receiving element, and being conveyed by the conveying means;
An opening on a line segment connecting the light emitting element and the light receiving element, and a second slit located between the first slit and the light receiving element;
Control means for determining the presence or absence of the micropattern based on transmitted light from the other surface of the paper sheet received by the light receiving element;
The length between the first slit and the second slit is at least twice the width of the fine line or the interval between the fine lines.
Paper sheet identification device. Generates frequency conversion information by frequency converting the received light output signal output from the light receiving element, from claim 1, wherein the identifying the presence or absence of the micro-pattern on the basis of said frequency conversion information according to claim 3 The paper sheet identification apparatus of any one of Claims 1. The paper sheet identification apparatus according to claim 4 , wherein the presence or absence of the micropattern is identified based on a value in a predetermined frequency region of the frequency conversion information. 5. The paper sheet identification apparatus according to claim 4 , wherein the presence or absence of the micropattern is identified based on a value of a second frequency domain with respect to a value of the first frequency domain of the frequency conversion information.

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