JP3353613B2 - Paper sheet identification device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet discriminating apparatus for discriminating the authenticity of a sheet.

[0002]

2. Description of the Related Art In recent years, in many cases, forgery of paper sheets has been performed by cutting off copies of the paper sheets. Forged spoofed paper sheets created by splicing such as black and white copies of paper sheets are difficult to detect by partial linear scanning with a point-type sensor, and it is possible to read the pattern of the paper sheet surface The use of a sensor is effective in discriminating cut and forged paper sheets.

FIG. 5 is a conceptual diagram showing an example of a configuration of a conventional point-type sheet discriminator and a method of scanning a sheet with respect to a magnetic sensor and an optical sensor. In the case of partial linear scanning by a point-type sensor as shown in this figure, if the magnetic sensor 9 determines the authenticity by detecting magnetism, the scanning area 11
By applying magnetism by means such as attaching a magnetic tape to the device, the authenticity determination by the magnetic sensor 9 becomes invalid.
Further, even if the optical sensor 10 detects a pattern or color by light, if the same pattern or color is similarly given to the scanning area 12 by means such as cutting, the authenticity determination by the optical sensor 10 becomes invalid. .

In order to solve this problem, a high-precision and high-performance banknote discriminating unit sometimes uses a contact-type linear image sensor for reading a pattern on the entire surface of a target paper sheet. The contact-type linear image sensor has a large number of divided bits, and is expensive because it has a lens array corresponding to the number of bits, and the cost of the discriminating section is greatly increased.

[0005] Instead of a contact type linear image sensor,
It is also possible to read a pattern on the entire surface of a sheet using a lens-reduced linear image sensor composed of one lens and a linear image sensor used in a copying machine or the like. FIG. 6 is a conceptual diagram showing an example of such a configuration.
(A) is a diagram viewed from a direction perpendicular to the transport direction of the paper sheet 3, and (b) is a diagram viewed from the transport direction. The illumination light source 2 irradiates light from the back of the paper sheet 3 and transmits the transmitted light to the imaging lens 4.
Thus, an image is formed on the light receiving surface of the photo sensor array 1 which is a kind of linear image sensor. Lighting source 2 is paper 3
Are arranged in the direction perpendicular to the transport direction in order to make the amount of light uniform.

However, such a photosensor array 1
The light receiving element such as does not perform a sufficient function unless the light receiving amount is adjusted to be appropriate. When the amount of light is small, a sufficient signal cannot be obtained, and when the amount of light is too large, the signal is saturated. Therefore, it is necessary to add an auxiliary function such as adjustment of the light amount. 7 to 9 are diagrams showing the relationship between the sensor position and the sensor output when a black line and a blue line are drawn on a blank sheet of paper and an image is taken by the photosensor array 1. FIG. FIG. 7 shows a case in which the light amount is appropriate. The sensor output of the portion 1a detecting the black line is lower than the threshold value, but the sensor output of the portion 1b detecting the blue line is larger than the threshold value. Therefore, a black line can be detected at the threshold level. However, when the amount of light is insufficient and the overall signal level decreases as in the case of FIG. 8, it is impossible to discriminate between a black line and a blue line with the same threshold value. FIG. 9 shows a state in which the amount of light in the peripheral portion is insufficient (referred to as shading). There is no problem in this state, but when the amount of light decreases, a portion below the threshold occurs in the outer peripheral portion. come.

Although the obtained pattern data is authenticated by pattern matching with reference data, the paper sheet transport path usually has some allowance for the width of the paper sheet. Therefore, the conveyed paper sheet does not always pass a fixed position with respect to the reading position of the sensor. Therefore, if pattern matching is performed as it is, there is a possibility of erroneous discrimination. For this reason, it is necessary to first extract a target feature or edge of the sheet, compare it with that of the reference data, and correct the position.

Further, if the resolution of the sensor is increased in order to read an image more clearly, it is necessary to increase the accuracy of position correction.

[0009]

As described above, the conventional sheet discriminating apparatus has the following problems. (1) A light source for illuminating the entire surface of a sheet is required when the pattern on the entire surface of the sheet is read by the sensor, and the light amount of the light source is adjusted so that the amount of light received by the sensor is appropriate.
It is necessary to correct the amount of received light, and a circuit and a mechanism for that need to be added, so that the cost increases and the number of parts increases. (2) The magnitude of the output of each sensor, which is a pixel, is used to extract a pattern or the like from the output signal (image data) of the read sensor. For example, it is determined that the pattern is black or another color based on a certain threshold. However, when the light amount changes due to a change in the light source or the like, the pattern cannot be stably extracted as shown in FIGS. 7 and 8. (3) When a pattern or the like is extracted from the read image data and compared with a reference pattern, there is a possibility that the transport position of the paper sheet may fluctuate by a certain width, so that erroneous determination may be performed. It is necessary to correct the position of the image. This position correction is a heavy burden because a huge amount of image data is processed by a microcomputer or the like, and requires a considerable amount of time. (4) Among banknotes, especially banknotes, etc., which follow various processes, are worn out from the same kind as new ones, and have folds that are worn out and become wrinkled or discolored, or stains are attached. There are various things, and various noises are included in the image data. For this reason, it may be determined that it is a "counterfeit part" even though it is a genuine note.

An object of the present invention is to provide a paper sheet discriminating apparatus using a linear image sensor, which solves the above-mentioned difficulties, is inexpensive, has a short discrimination time, and has a low probability of discrimination. And

[0011]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned problems.
To solve the problem, the direction perpendicular to the conveyance direction of the conveyed paper sheets
Linear image cell consisting of multiple pixels
A light receiving unit having a sensor, a light source for illuminating the paper sheet,
The reflected light or transmitted light from the paper sheet is converted into the linear light.
An imaging lens for forming an image on the image sensor.
It has a take-off sensor, and for a certain period of time when transporting the paper sheets
The light from the paper sheet is received and scanned by the light receiving unit at every interval.
The paper based on the output pixel data of the light receiving unit obtained
In a paper sheet discriminating apparatus for discriminating leaves, the pixel data
Data for each scan from multiple pixel data
Divided into multiple parts, and further in the transport direction
Matrix divided into multiple parts consisting of pixel data
Set a box-shaped discrimination area, and
Find the absolute value or the sum of the squared values of the output difference between matching pixels
To determine whether or not it is a "counterfeit part"
Together with setting a group consisting of a plurality of the discrimination areas
And the discrimination error that has been discriminated as a “counterfeit part” within that group.
Discriminate whether or not it is fake paper by the ratio of rear
It is characterized by:

A part of the discrimination area is different from each other.
Can be set repeatedly in the loop. In addition, once
One or one linear image sensor for each light-receiving scan
When the light reception amount of the above pixels reaches the preset light amount
The light reception of the linear image sensor for that time is terminated.
Is preferred.

In the present invention, the output of the pixel itself is
Rather, the use of the absolute value or the square value thereof of the difference in output between the adjacent pixels, it is possible to detect the contrast more stably. Also, instead of pixel units,
By obtaining the sum in a discrimination area having a fixed area including a plurality of pixel data , the influence of a positional shift or a print shift in conveyance is reduced, and the accuracy of the discrimination is improved. Furthermore, by setting a group in which several discrimination areas are put together and performing true / false discrimination by comprehensive judgment, the influence of wrinkles and stains is reduced, and the discrimination accuracy is further improved.

Further, each time light is received (scanned), a linear
The amount of light received by one or more pixels of the image sensor is predicted.
When the set light intensity is reached, the sensor
By turning off the light, the light source always changes even if the light source changes.
The appropriate amount of received light is obtained, and the pattern of the target
Trust can be obtained stably, and the accuracy of
Improve.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention discriminates paper sheets in the same configuration as that shown in FIG. 6, and quantifies the contrast of the paper sheet patterns based on the following two ideas. I have. The first is that the light reception by the sensor is terminated when the light reception amount of one or more pixels of the sensor reaches a predetermined light amount for each light reception (scanning). .

In the second method, the absolute value of the output difference between adjacent pixels of the sensor or its square value is sequentially obtained, and the contrast of the image of the paper sheet is quantified using the value.
Further, a sum of the absolute value or the square value is obtained in an appropriate area unit, and the contrast of the area is quantified. Examples will be described below.

FIG. 2 is a diagram showing the relationship between sensor position and sensor output for explaining a first embodiment of a paper sheet discriminating apparatus according to the present invention. Corresponds to 1. In the same manner as described in the section of the related art, the data is obtained when a black line and a blue line are drawn on a white paper and the image is captured by the photosensor array (hereinafter abbreviated as a sensor array) 1. In this case, when the light receiving amount of some of the sensors (that is, pixels) in the sensor array 1 reaches a predetermined light receiving amount (in the figure, the sensor output is 100), the sensor array 1
To the sensor, and the light reception of the sensor is terminated.

In this case, since the sensor receiving the light from the brightest white paper portion (background) receives the largest amount of light, the light reception is terminated when the received light amount of this portion reaches a predetermined value. Then, since the contrast between the white paper portion, the blue line portion, and the black line portion is determined by the brightness of each color and is constant, the output of the sensor detecting the blue line portion and the black line portion is constant regardless of the amount of illumination light. Thus, the contrast can be stably obtained, and the threshold value can be set constant. Therefore, if this method is used, the illumination light source 2
It is possible to omit or simplify the adjustment of the output and the compensation of the output of the sensor.

After the pattern of the paper sheet is detected in this manner, the paper sheet is discriminated by pattern matching. [Second Embodiment] In this embodiment, a reference signal which is a detection signal level of a background based on a sensor position, such as shading appearing in an output of a linear image sensor due to arrangement of illumination light sources, individual variations, characteristics of an optical system, and the like. When the level is no longer constant (for example, as shown in FIG. 9)
In addition, the contrast of a pattern is quantified and detected, and a pattern having a different contrast, such as black and blue, can be determined.

More specifically, the absolute value of the difference between the outputs of adjacent sensors on the sensor array 1 (hereinafter referred to as a differential value) or its square value is obtained. FIG. 1 is a diagram showing characteristics such as sensor output with respect to a sensor position for explaining the second embodiment. A thick line indicates a sensor output, and a thin line indicates a square value of a differential value (hereinafter, a differential square value and a differential square value). Abbreviated).

As shown in FIG. 1, the differential square value is large in the portion where the edge of the black line is detected, but is not 0 since the detection level is not constant in the portion where the blank portion is detected. Becomes a value close to "0", and in the portion where the edge of the blue line is detected, the value is clearly smaller than black, and is an intermediate value between the case of the black line and the blank portion. In this way, according to this embodiment, it is possible to determine the black line, the blue line, and the blank portion much more reliably than when the determination is made based on the output level of the sensor.

After quantifying and detecting the pattern of the sheet in this way, the sheet is discriminated by pattern matching. [Third Embodiment] In the second embodiment, when discriminating paper sheets by pattern matching, if the resolution of the sensor is high, there is a possibility that erroneous discrimination may occur due to a slight positional shift of the object. The third embodiment is an embodiment for mitigating the influence of the positional deviation, in which data for one scan of the sensor array 1 is divided into a plurality of portions, and the divided section has an expected maximum positional deviation. It is three times or more. The absolute value of the differential value or the sum of the differential squared values is obtained for each of the divided parts, and this is used as the discrimination data of each divided part. An example of this division corresponds to nine divisions in the vertical direction in FIG.

The determination data of the section including the sensor detecting the line (pattern) has a larger value than that of the portion detecting only the blank sheet, and it is easy to determine both. In addition, even if the position where the line (pattern) is detected is shifted due to the shift of the transport position or the print position, there is no large difference in the discrimination data within the same section. The possibility of misjudgment due to misalignment is greatly reduced.

[Fourth Embodiment] As described above, when discriminating paper sheets using the sensor array 1, the target paper sheets pass through the detection position (area) of the sensor array 1. By transporting and repeatedly performing imaging by the sensor array 1, it is possible to quantify and detect the contrast of the sheet pattern. The fourth embodiment detects such a contrast related to the surface pattern of a paper sheet.

In order to detect the contrast with respect to the surface pattern, one scan performed in the third embodiment is divided into a plurality of portions, and further, the transport direction is divided every predetermined number of scans, and the discrimination as shown in FIG. Area 5 is set. In FIG.
One scan is divided into nine parts, and four parts are divided into ten parts in the transport direction. An area surrounded by the division unit is defined as a determination area 5, and data of the entire imaged surface is divided into 9 × 10. .

The discrimination data of each divided portion of the sensor array 1 is obtained for each scan, and the result of adding the discrimination data in the discrimination area 5 is used as the discrimination data of the discrimination area. The value of the discrimination data depends on whether the pattern of the portion corresponding to the discrimination area 5 on the paper sheet to be discriminated is, for example, a black and white, a lightly colored pattern, or a blank paper. Since the state changes, it is possible to determine the state based on the determination data. Therefore, the sheet is discriminated by pattern matching in units of the determination area.

By setting the discrimination area in an area instead of a pixel unit as described above, even if there is a displacement between the width direction and the transport direction due to the transport or a print positional shift, the possibility of erroneous determination is greatly increased. Become smaller. Increasing the size of the discrimination area 5 increases the resistance to misalignment, and decreasing the size allows the contrast to be detected with high sensitivity. Regarding the resistance to the positional deviation, the lower limit of the size of the determination area 5 may be determined so as to allow a range such as the positional accuracy of the transport. However, if the discrimination area is reduced in order to increase the sensitivity of the contrast, the possibility of erroneous discrimination due to noise such as small stains and damaged parts such as folds increases.

[Fifth Embodiment] In a fifth embodiment, a plurality of adjacent determination areas are set as one group, and some groups are set on the entire surface on which a sheet is imaged. Find the discrimination results for each discrimination area in the group,
Then, it is determined whether or not the portion of the paper sheet corresponding to the group is forged based on the ratio of the determination area determined to be.
In the group corresponding to the forged part of the forged paper sheet, a determination result of “forged part” will be obtained in many determination areas, and in a part that is not forged, the “genuine part” ”Will be obtained.

If such a group is set in advance by assuming a forged portion due to cut-off, the discriminating ability of various types of cut-and-forged paper sheets becomes high, and the discrimination can be made effectively. be able to. FIG. 4 is a diagram showing an example of setting such a groove, and three groups 6, 7, and 8 are shown.
Is set. Of these, the groups 6 and 7 partially share the discrimination area included therein. in this way,
The groups may be independent or partially shared.

In the method using the differential absolute value of the sensor output or its squared value, when the light receiving amount of some of the sensors in the sensor array 1 reaches a predetermined light receiving amount, the light to the sensor array 1 is changed. It is also effective to use a method of shutting off the light and terminating the light reception of the sensor. It goes without saying that the discrimination accuracy is further improved by using both of them.

[0031]

Effects of the Invention According to the present invention, setting the determination area
And the absolute difference in output between adjacent pixels for each discrimination area.
Find the sum of the logarithmic value or the squared value, and use the sum
Section "and a plurality of determination areas
Set a group consisting of "forgery" within that group
Paper forgery paper sheets according to the percentage of the discrimination area
By discriminating whether or not there is , set a group,
Since the determination for each determination area is integrated, the influence of partial dirt, pain, and the like is reduced, the possibility of erroneous identification is reduced, and the reliability of the sheet identification apparatus is improved. Also,
Since various groups can be set, it is possible to cope with all types of spliced fake paper sheets, and it is possible to quickly cope with the emergence of new types of spliced fake paper sheets.

Furthermore, since the absolute value <br/> have with the difference in output between the neighboring pixels using a two-square value, even if the received light level fluctuates, stable in comparison with the case of using the sensor output as it Contrast can be evaluated quantitatively, authenticity discrimination is stable,
The possibility of erroneous discrimination is reduced, and the reliability of the paper sheet discriminating apparatus is improved.

Further, since the discrimination data is obtained as the sum of the absolute value or the square value in the discrimination area , the influence of the transfer position shift and the pattern print position shift is reduced, and the possibility of misidentification due to the position shift is reduced. Thus, the reliability of the paper sheet discriminating apparatus is improved.

Further, each time light reception (scanning) is performed, when the light reception amount of one or more pixels of the linear image sensor reaches a predetermined light amount, the light reception of the linear image sensor at that time is performed. Is terminated, the maximum value of the amount of light received by the sensor is controlled, so that light source output adjustment and light reception level correction processing to prevent fluctuations in the light reception level of the sensor due to changes in the light source, etc. There is no need to add a function, and it is possible to read the pattern of paper sheets stably with an inexpensive and simple configuration.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a sensor position and a sensor output for explaining a second embodiment.

FIG. 2 is a diagram showing a relationship between a sensor position and a sensor output for explaining a first embodiment;

FIG. 3 is a conceptual diagram showing an example of division for explaining third and fourth embodiments.

FIG. 4 is a conceptual diagram showing groups for explaining a fifth embodiment;

FIG. 5 is a conceptual diagram showing a configuration of a paper sheet discriminating apparatus using a point sensor and a scanning area.

FIG. 6 is a conceptual diagram showing a configuration of a paper sheet discriminating apparatus using a photosensor array.

FIG. 7 is a diagram showing a relationship between a sensor position and a sensor output in FIG. 6, showing a case where a black line and a blue line can be distinguished.

FIG. 8 is a diagram showing a case where a black line and a blue line cannot be distinguished;

FIG. 9 is a diagram showing a shading state;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensor array 2 Illumination light source 3 Paper sheet 4 Imaging lens 5 Discrimination area 6 1st group 7 2nd group 8 3rd group 9 Magnetic sensor 10 Optical sensor 11 Magnetic sensor scanning area 12 Optical sensor Scanning area 13 Light source for optical sensor 1a Portion where black line is detected 1b Portion where blue line is detected

Claims (3)

(57) [Claims] And 1. A light receiving portion having a linear image sensor comprising a plurality of pixels arranged in the conveying direction and perpendicular direction of the paper sheets to be conveyed, a light source for illuminating the paper sheet, from the paper sheet has an imaging lens for imaging the reflected light or the transmitted light on said linear image sensor, the reading sensor made of, the paper sheet every fixed time interval during transport of
The light from the paper sheet by receiving scanned by the light receiving portion to obtain et al
The paper sheet based on the output pixel data of the light receiving unit
In the paper sheet discriminating apparatus for discriminating the pixel data,
One scan consists of a plurality of pixel data.
Divided into multiple parts, and the transport direction is further divided by multiple scans.
Matrix divided into multiple parts of pixel data
-Shaped discrimination areas are set, and adjacent to each of these discrimination areas
Find the absolute value of the difference in output between pixels or the sum of the squared values,
When it is determined whether or not it is a “forged part” based on the sum,
A group consisting of a plurality of the determination areas is set,
The discrimination area determined to be a "counterfeit part" in the group
A sheet discriminating apparatus for discriminating whether or not the sheet is a counterfeit sheet according to the ratio of the sheet . 2. A method according to claim 1, wherein said discrimination area has a part different from each other.
Claims that are duplicated in the group
2. The paper sheet discriminating apparatus according to 1. To 3. A each time the light scanning, when the received light quantity of one or one or more pixels of the linear image sensor has reached a predetermined amount, reception of said linear image sensor for that time claim 1, characterized in that but is terminated
Alternatively, the paper sheet discriminating apparatus according to claim 2 .