JPS6245591B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a paper sheet recognition device, and more particularly to a paper sheet recognition device for detecting the edge position of a paper sheet or the like.

(2) Prior art and problems Detecting the edge position of a translucent sheet-like object such as a sheet of paper is difficult to detect, for example, in a terminal device for determining denominations of an automatic banknote deposit machine, where banknotes of different sizes are detected for each denomination. This is important when handling

For this reason, conventionally, a facing illumination type edge detection device as shown in FIG. 1 is used. The figure shows a light source array 2a consisting of light emitting diodes and the like arranged oppositely.
2b, sensor arrays 3a and 3b comprising, for example, photodiodes, and the paper sheet 1 to be detected. The light source drive circuit 4 uniformly lights up a plurality of light emitting diodes arranged in the light source arrays 2a and 2b, and the opposing photodiode receives the light emitted from the light emitting diodes, converts it into a corresponding electric signal, and applies it to the decoding circuit 5. The decoding circuit 5 decodes the input electrical signal and generates an edge detection signal based on the electrical signal from each photodiode of the sensor arrays 3a and 3b.
Output Se.

As the paper sheet 1 advances in the direction of the arrow, it blocks light from the light emitting diodes of the light source arrays 2a and 2b to the photodiodes of the sensor arrays 3a and 3b.
The mounting pitch of each of the photodiodes of the sensor arrays 3a and 3b is known in advance, and the edge detection signal changes depending on the degree to which the amount of light received by the photodiode is blocked by the paper sheet 1. The edges and width of can be detected.

However, the conventional device as described above has the following problems.

The first problem is that the above-mentioned apparatus cannot uniquely and precisely determine the width of the sheet to be passed. The sheet of paper 1 is semi-transparent and cannot completely block the light from the light source array 2a, and the transmitted light is incident on the photodiode at the bottom of the sheet of paper 1. This is because this transmitted light is greatly influenced by the pattern and coloring of the paper sheet 1. Also, the light from only one light emitting diode is not received by a single photodiode placed opposite to each other at the bottom, but instead is received by direct light from multiple light emitting diodes or by superimposing transmitted light that changes as described above. This is because it receives light.

This makes it difficult to accurately measure the width of paper sheets with various paper qualities and patterns.
The types of paper sheets that can be detected are limited.

The second problem is that there are variations in the amount of light emitted by the light sources in the light source array, in this example the light emitting diodes, so the accuracy of the edge detection signal is further reduced, usually by around ± several percent, in addition to the first problem. do.

Eliminating variations in the amount of light emitted from the light source requires the light source drive circuit 4' to be considerably complicated, and this adjustment is also considerably complicated.

A third problem is that the detection accuracy may vary depending on the position where the paper sheet passes. A passage area for the paper sheet is determined assuming the maximum width of the paper sheet to be detected, and the paper sheet passes through the passage area with some degree of freedom. In other words, it may shift to the right or to the left. The sensor array used is a long, integrated type, but its dimensions are limited (generally, the maximum length is about 25 mm). Therefore, if a sheet of paper passes beyond the width of the sensor array, it goes without saying that edge detection will not be possible, but one photodiode will superimpose direct light and transmitted light from multiple light sources. The detection signal differs depending on the position it passes through.

This means that the reproducibility is not good. To avoid such an effect, it is possible to use a longer sensor array, but there is a problem that the longer the sensor array is, the lower the accuracy is.

Measures the width of sheets of paper with various textures and patterns, regardless of variations in the amount of light emitted by the light source, the area through which the sheet passes, and without being affected by sensor size constraints or detection sensitivity. The apparatus shown in Fig. 2 has been proposed by the same applicant as an apparatus capable of performing high precision and reproducibility (Patent Application No. 1987-
93046).

In FIG. 2, a light source array 2 consisting of a plurality of light sources, for example light emitting diodes, which can be blinked independently.
A sensor array 3 consisting of a plurality of optical sensors, such as phototransistors, each capable of taking out a signal independently, is installed facing each other, and the paper sheet 1 is passed between them.

A light source selection circuit 6 that independently blinks each light source of the light source array 2 is provided between the light source drive circuit 4 and the light source array 2. A circuit example of the light source selection circuit 6 is shown in FIG. The selection signal S1 is sent to the signal identification circuit 6
1 and FET1 as a switching element.
Outputs a gate signal to one of FETn, and outputs a gate signal to one of FETn.
Power supply V _CC from the light source drive circuit 4 is passed through the FET to light one of the light emitting diodes LED1 to LEDn connected in series with the one FET. Resistor R
1 is a protective resistance.

A sensor selection circuit 7 is connected to the sensor array 3 for selecting and extracting one of the individual sensors of the sensor array 3 . A circuit example of the sensor selection circuit 7 is shown in FIG. The collector sides of each of the phototransistors PT1 to PTn of the sensor array 3 are connected in common and connected to the power supply V _CC via a resistor R2. In addition, the emitter side of the phototransistor PT is connected to a series resistor r1 to rn independently for each phototransistor.
one of the series resistors is connected and the other of the series resistors is grounded. A common connection point between the emitter of the phototransistor PT and the series resistor r is independently connected to a switching circuit 71 provided with a plurality of switching elements, such as analog switches. Therefore, when the switching circuit 71 receives the selection signal S1, the aforementioned light emitting diode is switched on.
Only the electric signal received and generated by the phototransistor PT facing the LED is output as the light reception signal S2.

Light emitting diodes LED1 to LEDn of light source array 2
and phototransistor PT1 of sensor array 3
It is provided in a one-to-one relationship with PTn.

A control device 8 that sends out the selection signal S1 mentioned above, receives the light reception signal S2 mentioned above, and processes the signal.
is provided. In the example shown in FIG. 2, the control device 8 includes a control calculation circuit 81, a storage circuit 82, an amplifier 83, an analog/digital converter, an output circuit 86, and a signal bus 85.

The operation of the apparatus shown in FIG. 2 will be described below.

First, when the paper sheet 1 is not present between the light source array 2 and the sensor array 3, a signal for selecting the first light emitting diode and the first phototransistor is sent from the control calculation circuit 81 via the signal bus 85 as the selection signal S1. The signal is sent to the light source selection circuit 6 and the sensor selection circuit 7. As a result, only the first light emitting diode LED1 lights up, and a light reception signal S2, which is received by the first phototransistor PT1 facing the LED1 and converted into an electric signal, is output from the sensor selection circuit 7.

The output of the light reception signal S2 from the sensor selection circuit 7 is a stable output determined based on the operating characteristics of the light emitting diode, the operating characteristics of the phototransistor, and the operating characteristics of the switching elements and circuit elements in the circuits 6 and 7. This will be done taking into consideration the timing when the results will be obtained.

The light reception signal S2 is amplified by an amplifier 83, converted to a digital value by an analog-to-digital converter 84, and input to the control calculation circuit 81 via a signal bus 85. Furthermore, the digital light reception signal inputted to the control calculation circuit 81 is stored in the storage circuit 82.
is stored in a predetermined area.

Next, the same operation as above is performed sequentially from the second to the nth.

By the above-described one-cycle scanning from the 1st to the nth cycle, the light-emitting/light-receiving characteristic data in the case where the sheet 1 of the opposing light emitting diode and phototransistor pair does not exist is stored in the storage circuit 82.

Next, a case where the paper sheet 1 exists between the light source array 2 and the sensor array 3 will be described. In this case as well, as in the case where there is no paper sheet 1, the operation of lighting one of the light emitting diodes and storing the light reception signal of the phototransistor provided oppositely in the memory circuit 82 is sequentially performed.

When the above operations are completed, calculate the ratio of each pair of light emission and light reception characteristic data when a paper sheet is present to each pair of light emission and light reception characteristic data when there is no paper sheet, which is stored in the memory circuit 82. , is determined by the control calculation circuit 81. If this ratio is approximately 1, it indicates that there is no sheet of paper between the light emitting diode and the phototransistor. Furthermore, if the ratio is considerably smaller than 1, for example 0.5 or less, the presence of the paper sheet will significantly reduce the light output from the light emitting diode and only the so-called transmitted light will be received by the photodiode. This indicates that there is a sheet of paper between the light emitting diode and phototransistor.

Although FIG. 2 only shows the light source array and sensor array on the right side edge, the light source array and sensor array on the left side edge are also operated simultaneously in the same manner as described above.

Since the spacing between the left and right sensor arrays and the mounting pitch of the phototransistors of the sensor arrays are known in advance, the control calculation circuit 81 can easily calculate the paper width of the passing paper sheet, and outputs the result through the output circuit 86. , subsequent equipment (not shown)
It is output as signal S0.

During the above operations, the amplifier 84 as a common element
The error fluctuations in the analog-to-digital converter 84, the quantization error fluctuations in the analog-to-digital converter 84, etc. can be considered to be approximately constant or negligibly small.

The light emission/light reception characteristic data for each pair may vary in terms of absolute values due to differences in the light output of the light emitting diodes, the sensitivity of the phototransistors, and the like. However, in the present invention, the presence or absence of a paper leaf is determined using the ratio of the light reception signal when a paper leaf exists for each pair to when a paper leaf does not exist, that is, the relative value. There is no problem even if there are such variations. In addition to light emitting diode variations, there are also problems in which the amount of light decreases relatively quickly over time, such as when an incandescent lamp is used as a light source. Since this is a relative ratio to the light emission/light reception characteristic data when a leaf is present, the edge of the paper leaf can be detected without any problem, and the width of the paper leaf can be calculated.

Furthermore, the ratio of the above-mentioned light emission/light reception characteristic data is approximately 1 when there is no paper sheet, and is considerably different when there is a sheet of paper. Therefore, even if there are differences in patterns on the same paper quality, they can be easily detected in a binary manner, improving the discrimination ability. This also applies to cases where there are differences in paper quality, and the range of types of paper sheets that can be reliably identified is expanded.

In this device, the position of the edge of the paper sheet, that is, the width of the paper sheet, can be detected up to the mounting pitch of each phototransistor of the sensor array 3. Further, the power supply capacity of the light source driving circuit can be reduced to one light source.

In the device shown in FIG. 5, the sensor array 3' is provided opposite the light source array 2, shifted by half a pitch P/2 from that in the device shown in FIG.
57-093046).

The other device elements are almost the same as those of the device shown in FIG. 2, but the control calculation circuit 81' of the control device 8 is different.

First selection signals S30 to S39, collectively referred to as S3, and second selection signals S40 to S4 when ten light emitting diodes of the light source array 2 and ten phototransistors of the sensor array 3' are provided.
The operation of the apparatus shown in FIG. 5 will be described below with reference to FIG. 6 which shows a timing chart of 9, collectively referred to as S4.

When the control calculation circuit 81' of the control device 8 receives a start signal St from a device (not shown) and a paper sheet passage signal Sm from a device (not shown), the logic of the gate signal Sg is set to "0" after a certain period of time TD (second This is also done in the operation of the drawing apparatus prior to scanning.)

A selection signal S30 for lighting the first light emitting diode and a selection signal S for accepting the signal of the first phototransistor from the control calculation circuit 81'.
40, the light source selection circuit 6 and the sensor selection circuit 7
Send to. Once the light reception signal of the phototransistor is stored in the storage circuit 82, the process is repeated sequentially up to the 10th light emitting diode and the 10th phototransistor.

Next, regarding the second pair with the light emitting diode shifted by one and the first phototransistor,
Scanning is performed sequentially up to the 10th light emitting diode and 9th phototransistor pair.

With the above one period PERIOD scanning, except for the 10th phototransistor, for example, the light receiving element of the 5th phototransistor receives light from the 5th light emitting diode and light from the 6th light emitting diode. Two types are obtained.

The light reception signal obtained in this way when the paper passes is divided by the light reception signal obtained for one period PERIOD before the paper passes, and the edge of the paper is detected in the same way as in the apparatus shown in FIG.

The directivity of the light emitting diode in the FIG. 5 device surrounds two opposing phototransistors that are offset by half a pitch with respect to the light emitting diode.

In the device shown in FIG. 5, the phototransistor is shifted by half a pitch with respect to the light emitting diode, and the light from two opposing light emitting diodes is received by one phototransistor. Detection accuracy can be doubled.

However, even in the device shown in FIG. 5, the accuracy was limited to 1/2 (±1/4) of the pitch of the edge sensor.

(3) Object of the Invention In view of the above-mentioned conventional drawbacks, it is an object of the present invention to provide a paper sheet recognition device that can double the accuracy of measuring the position of the edge of a paper sheet.

(4) Configuration According to the present invention, this object is provided with a light source array made up of a plurality of light sources and a photosensor array made up of a plurality of photosensors disposed opposite to the light source array. The light source array and the sensor array are shifted by half a pitch from each other and face each other, and the pair combinations of the light source of the light source array and the sensor of the sensor array are alternately shifted by one pitch for each scan, so that the plurality of A light source and a light sensor are selectively driven as a set, and the output of each light sensor when there is no object to be detected between the light source array and the light sensor array and the corresponding output of each light sensor when there is an object to be detected are determined. In a paper sheet recognition device that detects the edge of a paper sheet by comparing the optical sensor output with This is achieved by providing a paper sheet recognition device characterized in that the width of the paper sheet is shifted by ±1/4 pitch with respect to the sum of the width of the paper sheet and an integral multiple of the sensor pitch.

(5) Examples Examples of the present invention will be described in detail below with reference to FIG.

FIG. 7 is an explanatory diagram of the arrangement of the apparatus shown in FIG. 5 to further improve the measurement accuracy by a factor of two.

FIG. 7 clarifies the interrelationship between the pitch P of the light source array 2 and the sensor array 3, and the width l of the paper sheet 1. In Fig. 7, a and b are the left and right measurement reference points, L is the distance between the left and right measurement reference points, l is the width of the sheet, P is the pitch of the sensor and array, Δl is the increment in the width of the sheet series, m , n is an integer, then
In the present invention, the following relationship is established between these. That is, L=(l+mp)±P/4 P=Δl/n In other words, the distance L between the left and right mounting standards is shifted by ±1/4 pitch from the sum of the width L of the sheet and the integral multiple of the sensor pitch. The measurement accuracy can be improved by 1/4 pitch (±1/8
Pitch).

(6) Effects of the invention Conventionally, the left and right edge sensors in the light source array and sensor array were arranged irrespective of the width of the sheet, so the edge reading accuracy at the conveyance position was dependent on the arrangement pitch of the sensor array. 1/
However, according to the present invention, the accuracy of measuring the width of a paper sheet remains the same as before, but the accuracy of measuring the conveyance position can be improved to 1/4 pitch (±1/8 pitch).

[Brief explanation of the drawing]

1 and 2 are diagrams showing an example of a conventional paper sheet recognition device, FIG. 3 is a light source selection circuit in the device in FIG. 2, and FIG. 4 is a sensor selection circuit in the device in FIG. Fig. 5 is a diagram of a conventional example that is an improved version of the device shown in Fig. 2, Fig. 6 is an operation timing signal characteristic diagram of the device shown in Fig. 5, and Fig. 7 is a diagram of the measurement reference point, light source array, and sensor of the device shown in Fig. 2. FIG. 3 is a diagram showing the interrelationship of the pitch of the array and the width of the sheet according to the present invention. In FIG. 7, 1 is a paper sheet, 2 is a light source array,
3 is the sensor array, 4 is the pitch, l is the width of the paper sheet,
a and b indicate the left and right measurement reference points, and L indicates the interval between the measurement reference points, respectively.

Claims (1)

[Claims] 1 A light source array consisting of a plurality of light sources and an optical sensor array consisting of a plurality of optical sensors arranged opposite to the light source array are provided, and the light source array and the sensor array are arranged half-pitch with respect to each other above and below a paper sheet travel path. the light sources of the light source array and the sensors of the sensor array are alternately shifted by 1 pitch for each scan, and the plurality of light sources and photosensors are selectively driven in pairs. , by comparing the output of each of the optical sensors when there is no detected object between the light source array and the optical sensor array and the corresponding output of each of the optical sensors when the detected object is present. In a paper sheet recognition device that detects the edges of paper sheets, when edge sensors are arranged on both sides of the paper sheet travel path, the interval between the measurement reference points of the left and right edge sensors is set to an integral multiple of the width of the paper sheet and the sensor pitch. A paper sheet recognition device characterized by shifting the sum by ±1/4 pitch.