JPH10312481A - Paper sheet authenticity discriminating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the cost to be reduced and discrimination time to be shortened for discerning the authenticity paper sheets. SOLUTION: A light receiving part 3 consists of a linear image sensor, which is placed in the direction vertical to the transportation direction, and an image formation lens, which forms an image of an output light 2a from the light source 2 that transmits paper sheets 1 on the linear image sensor. A surface pattern sensor 4 is composed of the light source 2 and the light receiving part 3. A pattern detection means 5, according to the transportation of paper sheets 1, scans the linear image sensor in the light receiving part 3 at a fixed time interval and intermittently detects the surface pattern of paper sheets 1. Then, an approach detection means 6 obtains output differences between each pixel within the specified range of the linear image sensor, the absolute value or square total value of each output difference. Based on this total value, it is detected that a leading part 1a of paper sheets 1 approaches a scanning line of the surface pattern sensor 4.

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 authenticity of a sheet, and more particularly to a sheet discriminating apparatus having a function of measuring a timing of detecting a conveyed 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. It is difficult to detect the forged spliced paper sheet by partial linear scanning with a point-type sensor, and it is necessary to use a surface pattern sensor that can read the pattern of the surface of the paper sheet. It is effective for discriminating cut and forged paper sheets. For this reason, a high-precision and high-performance paper sheet discriminating unit uses a surface pattern sensor to read the pattern of the entire surface of the target paper sheet.

In some cases, a contact type linear image sensor type or a lens reduction type linear image sensor type is used as the surface pattern sensor.

FIG. 6 is a conceptual diagram showing a conventional configuration example of a surface pattern sensor of a lens-reduced linear image sensor type. FIG. 6A is a diagram viewed from a direction perpendicular to the paper sheet transport direction, and FIG. () Is a diagram viewed from the transport direction. The surface pattern sensor 60 mainly includes a linear image sensor 61 arranged in a direction perpendicular to the transport direction of the paper sheet 64, a light source 62 for illuminating the paper sheet 64, and linearly transmitting light from the paper sheet 64. And an imaging lens 63 that forms an image on the image sensor 61.

Immediately before the surface pattern sensor 60, a position detection sensor 65 is provided to measure the timing at which the conveyed paper sheet 64 enters the scanning line of the surface pattern sensor 60. The position detection sensor 65 detects the presence or absence of the target paper sheet 64. The surface pattern sensor 60 starts scanning by the linear image sensor 61 in response to a signal from the position detection sensor 65. Thus, the discrimination of the pattern on the surface of the paper sheet 64 is executed.

On the other hand, there is a method of detecting the position of a paper sheet without using the position detection sensor 65 and discriminating the pattern of the surface of the paper sheet 64. According to this method, when a sheet is inserted into the insertion port of the discriminator, the insertion of the sheet is detected by a sheet insertion detection sensor near the insertion port, and a conveyance roller, a conveyance belt, or the like is detected. The transport mechanism is driven to start transporting the sheets. At the same time or delayed by an appropriate time, in any case, the scanning of the surface pattern sensor is started before the paper sheet enters the scanning line of the surface pattern sensor.

However, in this case, since the surface pattern sensor starts scanning before the paper sheet enters the scanning line, image data of the background and the paper sheet are fetched without distinction. Therefore, this image data is temporarily stored in a memory, the outer edge portion of the paper sheet is extracted by special image processing, and the paper sheet portion or a part thereof is extracted from the captured image data. Used as authenticity discrimination data.

[0008] As an example using such a discriminating means,
Japanese Patent Application No. 8-17446 filed by the present applicant.
There is No. 5. Here, the output difference between adjacent pixels is obtained for each scan of the surface pattern sensor, and the absolute value or the square value is obtained. That is, the image data for one scan is differentiated in the arrangement direction of the pixels, and the absolute value or the square value of the value is obtained. Hereinafter, the value obtained by differentiating and squaring is referred to as “differential squared value”.

FIG. 7 is a diagram showing the relationship between the output of the surface pattern sensor and the differential square value. In the figure, a characteristic M10 is an output of the surface pattern sensor. In this example, a sheet in which a black line and a blue line are written on a white sheet is used. As shown in the characteristic M10, the output value of the pixel detecting the blank portion hardly changes. The output of the pixel detecting the black line is greatly reduced as in the portion M10a. Further, the pixel detecting the blue line is reduced by an intermediate size between the portion M10a and the blank sheet detecting portion as in the portion M10b.

The characteristic L10 on the lower side of FIG.
Is obtained and the result is expressed in a graph. In this case, the differential square value is almost “0” in the portion where blank paper is detected. On the other hand, the part M10a and the part M10
The differential square value of b is the characteristic L10a and the characteristic L10, respectively.
As shown in FIG. 10b, there is a large difference in the values. As described above, the change in the pattern can be clearly discriminated by obtaining the differential square value.

However, if pattern matching is performed based only on the differential square value, erroneous discrimination may be performed due to a slight displacement of the object if the resolution of the linear image sensor is high. Therefore, Japanese Patent Application No. 8-1744
In No. 65, image data is divided into regions having an arbitrary size, and the sum of differential square values included in each region is calculated. Hereinafter, this total value is referred to as differential sum of squares. By calculating the differential sum of squares, it is possible to quantitatively evaluate the contrast of the image in the area,
In addition to reducing erroneous discrimination due to misregistration of the object, when the contrast is high such as black and white copy, the differential square sum becomes a large value. On the other hand, when the contrast is low such as blank paper, Has a small differential sum of squares, and can be distinguished from genuine paper sheets.

[0012]

However, the above-mentioned conventional method has the following disadvantages. (1) First, as shown in FIG. 6, when one or several position detection sensors are used to detect a sheet entering a scanning line of a surface pattern sensor, the number of parts is reduced by including a detection circuit and the like. And the cost increases. (2) On the other hand, in Japanese Patent Application No. 8-174465, image data including the background is temporarily stored in the memory because the sheet starts scanning before the sheet enters the scanning line of the surface pattern sensor. In addition, it is necessary to extract the outer edge portion of the paper sheet by image processing or the like at a later stage. For this reason, there is a problem that the image data to be handled becomes large, the load on the extraction processing of the outer edge part also becomes large, and the processing time becomes long, or a high-speed high-performance processor or the like is required, and the cost is increased.

The present invention has been made in view of the above points, and has as its object to provide a paper sheet discriminating apparatus which is inexpensive and can shorten the discrimination time.

[0014]

According to the present invention, there is provided a sheet discriminating apparatus for discriminating the authenticity of a sheet, the linear disc being arranged in a direction perpendicular to a conveying direction of the sheet. A surface pattern sensor having an image sensor, a light source that radiates transmitted light to the paper sheet, and an imaging lens that forms an image of transmitted light from the paper sheet on a linear image sensor; Pattern detecting means for scanning the linear image sensor at regular time intervals in accordance with the conveyance of the sheet to detect a pattern on the surface of the sheet, and obtaining an output difference between pixels of the linear image sensor for each predetermined scan. Based on the absolute value or the sum of the squares of the respective output differences, an entry detecting means for detecting that the leading portion of the conveyed paper sheet has entered the scanning line of the surface pattern sensor, Characterized by having Paper sheet discriminating apparatus is provided.

In such a paper sheet discriminating apparatus, when the pattern detection means scans the linear image sensor at regular time intervals as the paper sheet is conveyed and detects the pattern on the surface of the paper sheet, the entrance detection is performed. Means for obtaining an output difference between the pixels of the linear image sensor for each predetermined scan, and, based on the absolute value of each output difference or the total value of the square values, a leading portion of the conveyed paper sheet has a surface pattern. It detects that it has entered the scanning line of the sensor.

That is, before the sheet enters the scanning line, the light source is directly viewed, so that the value of the output difference between the pixels of the linear image sensor for each scan increases, and the absolute value of the output difference or The sum of the squares also increases. On the other hand, in the scan immediately after the paper sheet has entered the scanning line, the outer edge of the paper sheet is read. At this time, since there is usually no pattern at the outer edge, and light is scattered and uniformly incident on the linear image sensor, the value of the output difference between pixels becomes small, and the absolute value of the output difference or the sum of the square values is obtained. The value also gets smaller.

By detecting the difference between the output differences in this manner, it is possible to detect that the outer edge of the paper sheet has entered the scanning line of the surface pattern sensor without using a position detection sensor as in the related art. Therefore, the structure is simplified.

Further, there is no need to perform complicated processing such as temporarily storing image data including a background in a memory and extracting an outer edge portion of a sheet by image processing or the like.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram of the functions of the paper sheet discriminating apparatus of the present embodiment. A light source 2 is provided below the transport surface of the sheet 1.
Is provided. The light source 2 irradiates the sheet 1 with output light 2a. On the other hand, above the transport surface, a light receiving unit including a linear image sensor arranged in a direction perpendicular to the transport direction and an imaging lens for forming an output light 2a transmitted through the paper sheet 1 on the linear image sensor. 3 are provided. The light source 2 and the light receiving unit 3 constitute a surface pattern sensor 4.

The pattern detecting means 5 intermittently detects the pattern on the surface of the sheet 1 by scanning the linear image sensor in the light receiving section 3 at regular time intervals as the sheet 1 is conveyed. Then, the entry detecting means 6 obtains an output difference between each pixel within a predetermined range of the linear image sensor for each predetermined scan, and obtains an absolute value or a sum of square values of each output difference.
Then, based on this total value, it is detected that the leading portion 1 a of the conveyed paper sheet 1 has entered the scanning line of the surface pattern sensor 4.

FIG. 2 is a diagram showing a schematic configuration inside the paper sheet discriminating apparatus of the present embodiment. Here, an example in which bills are discriminated as paper sheets will be described. An LED array 12 as a light source is provided below the transport surface of the bill 11.
On the other hand, above the transport surface, a linear image sensor (not shown) arranged in a direction perpendicular to the transport direction, and an imaging lens (not shown) for imaging the light 12a transmitted through the bill on the linear image sensor. Is provided. The LED array 12 and the light receiving unit 13 constitute a surface pattern sensor 14.

The control device 15 is composed of a processor, a memory, and the like.
Perform 1 discrimination. When a detection signal is sent from the insertion detection sensor 16 provided at the bill insertion slot of the paper sheet discriminating apparatus, the control device 15 operates a transport mechanism (not shown). At the time when the banknote 11 is inserted, the banknote 11 has not yet reached the position of the surface pattern sensor 14.
Starts sensing by the surface pattern sensor 14. However, the image data is not written to the memory until the leading portion 11a of the bill 11 is detected by a method described later.

The control device 15 detects the output of each pixel of the built-in linear image sensor from the surface pattern sensor 14 at the same time as the start of sensing. And the control device 15
Calculates the square value of the output difference between adjacent pixels from the output value for each scan. That is, the image data for one scan is differentiated in the pixel arrangement direction, and the square value of the value is obtained. Hereinafter, the value obtained by differentiating and squaring is referred to as “differential squared value”.

Further, the control device 15 obtains the sum of the differential square values for the pixels for one scan or the pixels in a limited portion. Hereinafter, this sum is referred to as a differential sum of squares. Then, the leading portion 11a of the bill 11 is detected based on the differential sum of squares.

Next, the leading outer edge portion 11 of the bill 11
A specific method for detecting a will be described. First, before the banknote 11 enters on the scanning line of the surface pattern sensor 14, the linear image sensor in the light receiving unit 13
The output light of the LED array 12 is viewed directly. FIG.
FIG. 4 is a diagram illustrating output characteristics of the linear image sensor when the output light of the LED array 12 is directly viewed. here,
The characteristic M1 indicates an actual output from the linear image sensor. Further, the characteristic L1 indicates a differential square value of the output from the linear image sensor. Here, 50 pixel data are shown, but actually, the linear image sensor is provided with more, for example, 178 pixels.

In the characteristic M1, portions M1a, M1b and M1c projecting downward (brighter) are portions at which the output light of the LED array 12 is directly viewed. This part M
Differential square values of 1a, M1b, and M1c are large values different from other portions as seen in corresponding portions L1a, L1b, and L1c of the characteristic L1.

The controller 15 sums up the differential square values obtained by the characteristic L1 for one scan or a limited portion of pixels to obtain a differential square sum. here,
The differential sum of squares is determined for the illustrated pixels (0 to 50), and the differential sum of squares at this time is 27112. Note that the value of the differential sum of squares shown here is a value obtained by calculating the output of the pixel based on digital data (for example, 8-bit data).

On the other hand, FIG.
FIG. 7 is a diagram illustrating output characteristics of the linear image sensor when the light beam enters the scanning line of FIG. The leading portion 11a of the bill 11 is
Usually it is a blank space. That is, as shown in FIG.
Since the bill 11 has a margin 11c at the periphery of the pattern surface 11b, the output light of the LED array 12 is scattered by the margin 11c and uniformly enters the light receiving unit 13. Therefore,
When the banknote 11 enters the scanning line of the surface pattern sensor 14, the output of the linear image sensor is the characteristic M of FIG.
2, the output difference between the pixels is small. As a result, as seen from the characteristic L2, the differential square value is not “0” due to variations in sensor sensitivity and non-uniformity of the light source. However, when the light source is viewed directly, or when the pattern surface 11b is scanned. The value is extremely close to “0” as compared with the case where The differential sum of squares in this case is, for example, 63.

Each time the control unit 15 obtains the differential sum of squares, it compares the value with a preset threshold value,
If the sum of the squares is smaller than a threshold value (for example, 1000), it is determined that the margin 11c has been detected. That is,
The control device 15 determines that the leading portion 11a of the bill 11 has entered the scanning line of the surface pattern sensor 14 when the differential square sum changes from 27112 to 63.

When the leading portion 11a of the bill 11 is thus detected, the control device 15 thereafter starts storing image data in the memory. Thus, the detection of the pattern surface 11b is performed. The method of discriminating the banknote 11 by detecting the pattern surface 11b may be the same as the conventional method.

As described above, in the present embodiment, the differential square value between adjacent pixels is obtained from the output value for each scan, the differential square sum is obtained, and the differential square sum is calculated based on the differential square sum value. Since the leading portion 11a of the bill 11 is detected, a position sensor for detecting the position of the bill 11 is not required, and image data is stored in the memory before the bill 11 enters the scanning line of the surface pattern sensor 14. It is possible to detect the leading portion 11a of the bill 11 without performing. Therefore, the number of parts can be reduced, and the cost is reduced. Further, since the image data to be handled can be reduced, the memory capacity can be reduced, the cost can be reduced, the load on data processing can be reduced, and the processing time can be shortened.

In the present embodiment, the differential sum of squares is obtained, but the sum of the absolute values of the differential values may be used. Also,
In this embodiment, the output light 12a of the LED array 12 is
1 and is received by the light receiving unit 13.
The ED array 12 is provided on the same side as the light receiving unit 13, the output light 12 a is reflected on the bill 11, and the reflected light is reflected on the light receiving unit 1.
3 may be received. However, in this case, a reflection plate having an appropriate high-contrast pattern (for example, a barcode having a resolution of about the surface pattern sensor 14) is provided on the back surface of the bill 11, or the output light of the LED It is necessary to provide something that directly reflects 12a.

In the present embodiment, the bill 11 is used as a paper sheet.
Although the example of discriminating is shown, it is also possible to discriminate securities and the like. Furthermore, in this embodiment, the differential sum of squares is obtained for each scan, but the present invention is not limited to this, and it may be obtained for each of two or more scans.

[0034]

As described above, according to the present invention, the linear image sensor is scanned at regular time intervals as the paper sheet is conveyed to detect the pattern on the surface of the paper sheet, and the linear image sensor is scanned every predetermined scan. The output difference between the pixels of the sensor is obtained, and it is detected that the leading portion of the conveyed paper sheet has entered the scanning line of the surface pattern sensor based on the total value of the absolute value or the square value of each output difference. Therefore, it is possible to detect that the outer edge of the paper sheet has entered the scanning line of the surface pattern sensor without using a position detection sensor. Therefore, the structure is simplified and the cost is reduced.

Further, there is no need to perform complicated processing such as temporarily storing image data including a background in a memory and extracting an outer edge portion of a sheet by image processing or the like.
Therefore, the discrimination time is reduced.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating functions of a paper sheet discriminating apparatus according to an embodiment.

FIG. 2 is a diagram showing a schematic configuration inside a paper sheet discriminating apparatus of the present embodiment.

FIG. 3 is a diagram illustrating output characteristics of a linear image sensor when the output light of an LED array is directly viewed.

FIG. 4 is a diagram showing output characteristics of a linear image sensor when a bill enters a scanning line of a surface pattern sensor.

FIG. 5 is a diagram showing a schematic configuration of a face of a bill.

FIG. 6 is a conceptual diagram showing a conventional configuration example of a lens pattern reduction linear image sensor type surface pattern sensor, and FIG.
FIG. 3 is a view as seen from a direction perpendicular to the transport direction of the paper sheet, and FIG. 3B is a view as seen from the transport direction.

FIG. 7 is a diagram showing a relationship between an output of a surface pattern sensor and a differential square value.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sheet 1a Head part 2 Light source 2a Output light 3 Light receiving part 4 Surface pattern sensor 5 Pattern detecting means 6 Entry detecting means 11 Banknote 11a Head part 12 LED array 12a Output light 13 Light receiving part 14 Surface pattern sensor 15 Control device

Claims (4)

[Claims] 1. A sheet discriminating apparatus for discriminating authenticity of a sheet, a linear image sensor disposed in a direction perpendicular to a conveying direction of the sheet, and a light source for irradiating the sheet with transmitted light. And a surface pattern sensor having an imaging lens that forms an image of transmitted light from the paper sheet on a linear image sensor; andscanning the linear image sensor at regular time intervals with the conveyance of the paper sheet. Pattern detection means for detecting a pattern on the surface of the paper sheet, and calculating an output difference between pixels of the linear image sensor for each of the predetermined scans, and calculating an absolute value or a square value of the output differences A paper sheet discriminating apparatus, comprising: an entrance detecting unit configured to detect that a leading portion of the conveyed paper sheet has entered a scanning line of the surface pattern sensor based on the above. 2. The paper sheet discriminating apparatus according to claim 1, wherein said approach detecting means is configured to obtain said output difference for each one of said scans. 3. The paper sheet discriminating apparatus according to claim 1, wherein the paper sheets are bills. 4. A sheet discriminating apparatus for discriminating authenticity of a sheet, a linear image sensor arranged in a direction perpendicular to a conveying direction of the sheet, and a light source for irradiating the sheet with light. A surface pattern sensor having an imaging lens that forms an image of reflected light from the paper sheet on a linear image sensor; and a rear surface side of the paper sheet viewed from the light source, and a high contrast suitable A reflector having a simple pattern or a surface that directly reflects light from the light source, and scanning the linear image sensor at regular time intervals along with the transport of the paper sheet, and the surface of the paper sheet A pattern detecting means for detecting a pattern; calculating an output difference between pixels of the linear image sensor for each of the predetermined scans; and conveying the output based on a total value of absolute values or square values of the output differences. The top of the paper is And entry detection means for detecting that it has entered the scan line of the serial surface pattern sensor, a paper sheet discriminating apparatus characterized by having a.