JP2903557B2 - Duplicate feed detection method for paper sheets - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a double feed of a paper sheet, and more particularly, to detecting a double feed of a paper sheet by a double feed detection device using an optical sensor including a light emitting element and a light receiving element. It is about the method.

[Conventional technology]

In devices that separate paper sheets from multiple paper sheets one by one and send them into the device, such as optical character reading devices and automatic certificate issuing devices, and perform character reading and printing processing, etc. If no abnormality is detected, only one of the stacked sheets is processed, and the other sheets are subjected to data evaporation, which is an extremely serious obstacle. For this reason, there is a demand for a sheet overlap detection device having high detection performance.

As a conventional sheet overlap detection method, the amount of light passing through a sheet is checked using an optical sensor combining a light emitting element and a light receiving element, and one or two sheets set in advance are checked. A method of detecting a double feed of a sheet by comparing with a threshold value for discrimination has been often used. As a method of determining the above-described threshold, for example, as disclosed in Japanese Patent Application Laid-Open No. 56-82989, the threshold is determined at the time of transaction, A method has been proposed in which the output when one sheet of paper is passed through an optical sensor for the first time is read, and a decision is made using the result of this reading.

Another method is to read the actual optical sheet by reading the optical sensor output in the absence of a paper sheet before the transaction and multiplying by the light transmittance of the set and read sheet. There is also known a method of estimating an output at the time of passing through an optical sensor and determining a threshold value for determining one sheet or two sheets.

[Problems to be solved by the invention]

In the former technique of the prior art, that is, the first sheet of paper is passed through an optical sensor at the time of transaction, and the threshold is determined from the output of the optical sensor at this time. Leaves must not be sent in duplicate, so they should be held in the equipment in a different way than normal and fed, or they should be hand-operated optically before trading. There is a problem that means such as passing through a sensor is required. In the case where a plurality of sheets are continuously processed, the temperature gradually increases, and the characteristics of the optical sensor change. Therefore, the threshold value obtained by reading the first sheet by the optical sensor is used. , An error occurs, and the performance of the double feed detection deteriorates.

Also, in the latter of the above-mentioned prior arts, that is, by reading the output of the optical sensor in a state where there is no paper before the transaction, and multiplying by a preset light transmittance of one paper, the actual paper Even in the method of estimating the output when one sheet is passed through the optical sensor, when the output light amount of the light emitting element changes due to the above-mentioned temperature fluctuation, the relationship between the light receiving amount at the light receiving element and the output level is generally Is non-linear, the output of the light-receiving element without a sheet and the output of the light-receiving element when one sheet of paper actually passes through are not the same in the rate of change due to temperature fluctuations. However, even if the output of the optical sensor in the absence of a sheet is multiplied by the preset light transmittance of one sheet, the output of the optical sensor in one sheet cannot be correctly estimated. was there. FIG. 4 (a) shows an outline of the temperature dependence of the characteristics of the light emitting element.
(B) shows an outline of the temperature dependence of the characteristics of the light receiving element.

The present invention has been made in view of the above circumstances, and an object of the present invention is to solve the above-described problems in the related art, and to improve the detection performance even when the characteristics of the optical sensor change due to temperature fluctuation or the like. It is an object of the present invention to provide a method for detecting a double feed of a paper sheet without lowering the paper feed.

[Means for solving the problem]

The object of the present invention is to provide an apparatus for detecting the amount of transmitted light of a sheet using a light-emitting element and a light-receiving element, thereby detecting a double-feed of a sheet. The amount of light received by the light receiving element when transmitted,
So that the amount of light received without paper is the same level
A light-emitting element drive current control means for controlling the light emission amount of the light-emitting element is provided, and the light-emitting element drive current control means sets the drive current of the light-emitting element to a low level before the transaction, thereby reducing the amount of paper. The output of the light receiving element in the absence state, when the drive current of the light emitting element is set to a high level side,
As an estimated value at any time of the output of the light receiving element in the state where the predetermined sheet is present, using the estimated value, determine a threshold value required to detect the overlap feed of the predetermined sheet, The present invention is also achieved by a method of detecting a double feed of a paper sheet, which is updated as needed.

[Action]

The amount of light received by the light-receiving element when one sheet of a predetermined type is inserted between the optical sensors is smaller than the amount of light received by the light-receiving element without the sheet. Decrease at a rate corresponding to the rate. When the light emission amount of the light emitting element is reduced at the rate at which the light reception amount decreases, the light reception amount of the light receiving element becomes
This decreases at the same rate as when a single sheet having the above-described light transmittance is inserted in a pseudo manner.

Since the light emission amount of the light emitting element has a characteristic proportional to the amount of current for driving the light emitting element under a normal use condition,
The drive current of the light emitting element is reduced at the same rate as the rate at which the amount of light received by the light receiving element is reduced by inserting one sheet of the predetermined type of paper, and the output of the light receiving element at that time is:
It is possible to estimate the output of the light receiving element in a state where one sheet of the predetermined type is inserted when the driving current of the light emitting element is restored.

In the sheet overlap feed detecting device according to the present invention, based on such a principle, the output of the light receiving element in one sheet is estimated at any time based on such a principle, so that one sheet in accordance with the amount of the fluctuation is estimated. In this case, the estimated value of the output of the light receiving element can be followed. By estimating the output of the light receiving element on a single sheet in such a manner, the detection performance of the double feed of the sheet is not affected at all by the characteristics of the light receiving element, and due to temperature fluctuation or the like. It is possible to prevent a decrease.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a diagram showing a hardware configuration of a sheet overlap feed detecting apparatus according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a light emitting element capable of controlling the amount of emitted light by the amount of current for driving the same. Under normal use conditions, a light emitting element having a linear relationship between the amount of emitted light and the drive current is used. Reference numeral 2 denotes a light-emitting element drive current switching circuit which can arbitrarily set and switch the drive current of the light-emitting element 1 and includes a D / A converter, a comparator, a transistor, and the like. After D / A conversion of bit information, voltage / current conversion is performed. A light receiving element 3 detects the amount of light emitted from the light emitting element and the amount of transmitted light transmitted through the paper sheet without the paper sheet.

Reference numeral 4 denotes a paper sheet whose light transmittance (light transmission light amount / incident light amount) for each type and paper thickness is known. Reference numeral 5 denotes an amplifier circuit that performs current / voltage conversion and amplification of the output of the light receiving element 3.
Reference numeral 6 denotes an A / D converter, which digitizes the output of the amplifier 5. In the following description, this digitized result is called a sensor output. Reference numeral 7 denotes a control unit which performs reading of sensor output by the A / D converter 6, setting of the light emitting element driving current switching circuit, light emitting element driving current control means 2, determination processing of paper sheet overlap feed detection, and the like.

Next, the operation will be described with reference to the flowchart of FIG.

First, in step 10, before a transaction requiring a process of feeding out a paper sheet, information on the type of the paper sheet used in this transaction (for example, the light transmittance of the paper sheet: M) is transmitted from a higher-level device or an operator. Is input to the control unit 7 by key input or the like. In step 11, the drive current of the light emitting element 1, the drive current switch circuit 2, for example, set to an initial value I ₀ shown in FIG. 3 (a). As the current I _0, it should be selected having a relatively low level.

Next, at step 12, takes in the driving current of the light emitting element 1, in a state of setting the initial value I ₀ of the above, the sensor output in the absence of paper in the control unit 7. Then, the sensor output at this time, the paper sheet one that is used in this transaction holds as an estimate D ₀ of the sensor output when passing between the light emitting element 1 and the light receiving element 3.

Next, in step 13, after incorporation of the estimated value D _0,
The drive current of the light emitting element 1, the drive current switch circuit 2, to switch set to the current I ₁ at the time of monitoring the feed state of the paper at the time of the transaction. At this time, the current I ₁
Is determined in accordance with the type information of the paper sheet taken in (1), and in the present embodiment, is determined by the calculation of I ₁ = I ₀ / M (see FIG. 3 (a)). Here, M indicates the light transmittance of the above-described paper sheet.

In step 14, after the drive current of the light emitting element 1 has been set as described above, to start the transaction, capturing sensor output D ₁ of the when the feeding of the paper is being performed in the control unit 7.

In the control unit 7, the estimated value D ₀ of the sensor output at the paper piece taken in the sensor output D ₁ and above, to detect duplicate feed of paper, performs a predetermined determination process in step 15 . Here, .alpha.D ₀ the lower limit of determining the sensor output D ₁ and one paper, the upper limit value and beta-D _0, the sensor output D ₁ is assumed to determine that the case overlap feed below this limit value. Here, α and β are coefficients set in consideration of sheet thickness variations and the like.

After performing the above determination, when performing a plurality of determinations for one sheet, that is, when performing multiple point measurement,
To step 14, in order to follow the temperature change, when updating the estimated value D ₀ of the paper a single sensor output, to the processing of step 11, also the type of paper to be used in the transaction In the case of changing, the process returns to the process of step 10.

According to the above-described embodiment, for each overlap detection device for paper sheets,
Even if the characteristics of the light-emitting element 1 and the light-receiving element 3 vary, the characteristic changes due to characteristic deterioration or temperature fluctuation, it is easy to update the estimated value of the sensor output per sheet according to these fluctuation amounts. And it is possible to prevent the double feed detection performance from being lowered.

In the above embodiment, as shown in FIG. 3A, the control of the light emission amount of the light emitting element by the light emitting element drive current switching circuit is performed by controlling the light reception amount by the light receiving elements corresponding to a plurality of types of paper sheets. Although an example is shown in which the received light amount in the state without the presence of the light is the same level, the present invention is not limited to this, and as shown in FIG. The amount of light received by the light receiving element may be adjusted so that the amount of light received in a state with a paper sheet is the same level.

Further, in the above-described embodiment, the example has been described in which the driving current of the light emitting element 1 is switched to the light transmittance of the sheet to estimate the sensor output for one sheet. Estimating the lower limit value of the sensor output for determining a single sheet by changing the switching ratio of the current in the circuit 2 based on the coefficient determining the lower limit value of the sensor output for determining the single sheet. Is also possible. Similarly, it is also possible to estimate the upper limit value of the sensor output for determining two sheets.

Further, in the above-described embodiment, an example in which the light transmittance of the sheet is used as the type information of the sheet has been described. However, the light transmittance is different from the sensor output in the absence of the sheet and the sheet output. When the drive current of the light emitting element 1 is switched so that the sensor output on the sheet becomes the same level, it can be easily determined by the ratio of the two drive currents. It can be done easily. The light emitting element drive current switching circuit 2 may be any circuit that switches the current in accordance with the number of types of paper sheets to be used, and may be configured using, for example, an analog switch.

〔The invention's effect〕

As described above in detail, according to the present invention, in the sheet overlap feed detecting apparatus, even if the characteristic of the optical sensor changes due to a change in the ambient temperature or the like, the sheet is not present at any time. The output of the optical sensor of one sheet can be estimated from the output of the optical sensor, and the threshold value of one sheet or two sheets is determined and updated as needed according to the output. Even if the characteristics of the sensor change, an effect of realizing a double-feed detection method of the paper sheet without lowering the detection performance can be achieved.

[Brief description of the drawings]

FIG. 1 is a flow chart for detecting a double feed of a paper sheet according to one embodiment of the present invention, FIG. 2 is a hardware configuration diagram of the apparatus for detecting a double feed of a paper sheet according to the embodiment, and FIG. 3 is an operation of a drive current switching circuit. FIG. 4 is a diagram showing an outline of the temperature dependence of the characteristics of the light emitting element and the light receiving element. 1: light emitting element, 2: light emitting element drive current switching circuit, 3: light receiving element, 4: paper sheet, 5: amplifier circuit, 6: A / D converter, 7: control unit.

Claims (4)

(57) [Claims] An apparatus for detecting overlapped feed of a sheet by examining the amount of light transmitted through the sheet using a light emitting element and a light receiving element, the apparatus detects a double feed of the sheet and transmits a predetermined sheet. Light emitting element driving current control means for controlling the amount of light emitted by the light emitting element so that the amount of light received by the light receiving element at the time and the amount of light received without a sheet are the same level; By the drive current control means, when the drive current of the light emitting element is set to the low level side before the transaction, the output of the light receiving element in the absence of a paper sheet, the drive current of the light emitting element to the high level side When the setting is made, the output of the light receiving element in the presence of the predetermined sheet is an estimated value at an arbitrary point in time, and the estimated value is used to detect the overlap feed of the predetermined sheet. Special thresholds and updating them as needed. Duplicate feed detection method of the paper to be. Means for setting the type of paper sheet to be used, and means for determining two drive currents to be switched by the light emitting element drive current control means in accordance with the type of paper sheet;
2. The method according to claim 1, wherein a plurality of types of paper sheets can be handled. 3. The method according to claim 2, wherein the low-level value of the drive current of the light emitting element corresponding to the plurality of types of paper sheets is a common value. . 4. A lower limit value of a light receiving amount of a light receiving element for judging that a predetermined sheet is a single sheet, a switching ratio between a high level and a low level of the driving current by the light emitting element driving current control means, and The ratio with the light receiving amount in the absence state, the threshold value can be estimated from the output of the light receiving element in the state without the paper sheet, The threshold according to any one of claims 1 to 3, Duplicate feed detection method for paper sheets.