GB1600962A - Apparatus for checking documents - Google Patents

Description

(54) APPARATUS FOR CHECKING DOCUMENTS (71) We, ARAL AUSTRIA GESELL SCHAFT m.b.H. an Austrian Company of Favoritenstrasse 36, A-1040, Vienna IV, Austria, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to apparatus for checking documents, such as banknotes.

Austrian Patent Specification 311,097 discloses a method of measuring the soiling of bank notes in which a light ray is directed to selected portions of the edge of a bank note and the scattered light which emerges at an angle is applied to a detector and the (luminance) signal which is generated by the detector is fed to an evaluating circuit. The measurement is taken at the edge of the bank note because the check should not be affected by the print. The printed publication mentioned above teaches that it is not desirable to evaluate the soiling of the bank note in dependence on its transmittance or reflection of light because of the tolerances which are inevitable in the production of paper.The known method is based on the fact that the signal which corresponds to the brightness of the paper is composed of a constant component which is proportional to the reflectivity of the paper, and an alternating component, which represents the soiling of the paper. For this reason a constant signal is combined with the amplified signal of the photocell in such a manner that the constant component of the photocell signal is compensated. The known method cannot be used to check bank notes for genuineness because the print is not checked at all.

It is known from Austrian Patent Specification 321,619 to detect a spectral reflection of coloured surfaces in order to check the genuineness of bank notes. To enable a statement regarding the genuineness of a bank note, the reflectivity at a specific point of a bank note to be checked is compared with a measured reference value. That comparison is performed in accordance with a quotient method so that the influence of soiling is eliminated. The method cannot be expected to give satisfactory results because in view of the natural variation of transmittance and of the position of the print of bank notes the selected tolerances must be so large that the bank notes cannot be reliably distinguished from simple counterfeits.

In other known apparatus for genuineness checks, the light reflected by the bank note or the light transmitted through the bank note is sensed and evaluated. U.S. Patent Specification 3,220,549 discloses apparatus which in checking the genuineness of bank notes relies only on reflected light, which is subjected to a spectral analysis for measurement and evaluation.

Printed German Specification 1,524,627 discloses apparatus for automatically checking and counting bank notes. In that apparatus, newly printed bank notes are checked for soiling by a first detector system, which scans one side of the bank note and the other and rejects soiled bank notes. The bank notes are also checked for eccentricities of the print by a photoelectric second detector system which comprises for each side of the bank note a detector for checking the bright edge portion of the bank note at a reference point of measurement at one edge of the bank note and two detectors for scanning the bright edge portion of the bank note along the adjacent edge thereof.In accordance with that disclosure, the variation of the voltage delivered by the detectors as a function of the luminance of the reflected light during the scanning of the three reference points of measurement is considered as the actual value. That voltage is then compared with a desired value and a bank note will be rejected when the difference between the actual and the desired values exceeds a certain value. It is apparent that the known apparatus substantially relies on the reflection of light by the bank note for measuring the actual value. All apparatus described hereinbefore have the disadvantage that the means for evaluating the actual value are extremely complicated and expensive and liable to be deranged or do not operate with satisfactory accuracy.

It is an object of the invention to provide apparatus which serves for checking documents and which has a checking mechanism that is structurally simple but sufficiently accurate. According to the present invention, in apparatus for checking documents, such as bank notes, a document is moved by a transport mechanism in a single direction in the plane of the document, beneath a light ray directed perpendicularly towards the document at selected portions thereof which exhibit a print, and the scattered light emerging at a predetermined angle is applied to a detector, the (luminance) signal which is generated by the detector being fed to an evaluating circuit, in which the signal generated by the detector in response to the scattered light which emerges at the predetermined angle is compared with a standard value signal obtained when an original or speciment document is checked under the same conditions at the corresponding portions, and the detector for scattered light is connected to modules in the form of sample and hold circuits, equal in number to the number of selected portions, and connected in parallel with each other and having control inputs connected to a sequence controller, which is responsive to output signals of a timer or of a position signal generator which in turn is responsive to the operation of the transport mechanism, each module being connected to a comparator to enable its output to be compared with the afore-mentioned value, the outputs of the comparators being connected respectively to the inputs of a common AND-gate which has an output for controlling the further transport of the document.

Conveniently transmitted light emerging from the document on the opposite side to the light source is applied to a further detector, the signal generated thereby being fed to an evaluating circuit for comparison with an appropriate standard-value signal obtained under the same conditions at a corresponding selected portion of the original or specimen document, the further detector also being connected to further modules arranged, functioning and connected as the originally-mentioned modules.

Amplifiers may be interposed between the or each detector and the associated modules.

Preferably, the output signal of the timer or of the position signal generator is applied to a counter connected to a length comparator, the output of which is fed to one on the inputs of the AND-gate. The entire checking mechanism is greatly simplified because the actual-value signals generated by the detector are specifically evaluated in the apparatus according to the invention in response to the output signal generated by a timer or of the output signal generated by a position signal generator in response to the operation of the transporting mechanism.

The transporting means must be provided in any case for the continued transport of the documents to be tested and may be utilized, in accordance with the invention, for an additional function, namely, for the control of a position signal generator. It is desired to sense particularly the scattered light which emerges at angles between 300 and 60 or at a selected angle in that range. Desirable values for Austrian bank notes (100, 500 and 1000 Austrian schillings) will be measured at an angle of 45". That angle need not be exactly adhered to and different angles of measurement may be desirable for other bank notes.

The invention will now be explained further by way of example with reference to the accompanying drawings, in which Figure 1 is an enlarged view which illustrates the conditions which prevail during the irradiation of a document (bank note); Figure 2 illustrates the light path; Figure 3 is a diagrammatic view which illustrates the conditions which result during the irradiation of a bank note; Figure 4 shows diagrammatically the quantitative distribution of light during the irradiation of a bank note (4A for a bright portion and 4B for a dark portion), of white paper, (4C) and of dull black paper (4D); Figure 5 shows diagrammatically a measuring system for checking documents (bank notes) according to the invention; and Figure 6 is a block circuit diagram of the checking system.

Figure 1 shows the light conditions which are obtained during the check of a used document (bank note) 9 of paper of paper or a similar translucent material. The document 9 is disposed above a wall 12 and is provided on both sides with printed coloured layers 10. Used bank notes have on each side also a soil layer 11.

It is assumed that a light source L emits monochromatic light, particularly red light (635 nm) of constant luminance. The measurement is improved by the use of monochromatic rather than ordinary light, although the use of monochromatic light is not essential. As is diagrammatically indicated in Figure 3, the light is substantially separated into three components, the mag nitude and angular distribution of which depend in different degrees on the nature of the document. The first component consists of the reflected light which is thrown back from the surface into the light source L by direct reflection. That component is indicated in Figure 3 by the arrow P1 and is only of indirect significance for the measurement. The second component consists of the transmitted light which emerges from the rear side of the document after having been attenuated by absorption in the document 9.

This component is indicated by the arrow P2 in Figure 3 and sensed by a detector D2 and may be utilized for controlling the measuring operation, for length measurement and for a coarse evaluation of the quality of the paper and of the print. The third component is the scattered light which emerges in all directions and is indicated by the arrow P3 in Figure 3 and used in part for an exact evaluation of the document 9. The scattered light is sensed by a detector D1, which is disposed on the same side of document 9 as light source L and at an angle a = 45" to the primary ray.The rays which are included in the scattered light (P3) are identified in Figure 1 as follows: 1) light scattered by the soil layer 11 facing the light source L; 2) light scattered by the coloured layers 10 facing the light source L; 3) light scattered by the texture of that surface of the base material of the document 9 which faces the light source L; 4) light scattered by the bulk of the base material of the document 9; 5) light scattered by the texture of that surface of the base material of the document 9 which faces the detector D2 for transmitted light 6) light scattered by the coloured layers 10 which face the detector D2; 7) light scattered by the soil layer 11 facing the detector D2; 8) light which has been diffusely reflected by the base 12 which is opposite to the light source L.

As is shown more in detail in Figure 2, stops 13 and optical lenses (not shown) are provided, which serve to direct the rays.

These elements may be incorporated in the light source L and detectors D1 and D2 or may be separate from them.

Figures 4A to 4D represent the quantitative distribution of light. The length of the arrows P1, P2 and P3 represents, respectively, the quantity of reflected light, the quantity of transmitted light and the quantity of scattered light. These are represented in Figures 4A and 4B for a bright portion and for a dark portion of a document 9, in Figure 4C for white paper and in Figure 4D for dull black paper.

In accordance with Figure 5, conveyor belts 19, 14, 15 are provided for the transport of the document 9. The document 9 is moved with one of its side edges in contact with a guiding surface 16 for lateral guidance. It is assumed that all points of measurement to be utilized for a comparison of an actual value and a desired value lie on a straight line (measuring trace) 17 so that one transducer head 18 will be sufficient. It is assumed that a measurement at three points I, II, III is sufficient for a genuineness check. As the document 9 is moved by the belt conveyors 19, 14, 15 in the direction of the arrows P4, the points of measurement III, II, I are moved in succession to a position under the transducer head 18 so that the scattered light from each point of measurement and, if desired, also the transmitted light can be sensed and evaluated.It will be understood that the measurement may be effected in a plurality of measuring traces and at more than three points and may also be effected continuously if this is desired. The length of the note may also be detected as an additional criterion of genuineness.

In the block circuit diagram shown in Figure 6 it is assumed that the check relies not only on the measurement of scattered light but also on the transmitted light at the selected points of measurement I, II and III for the comparison of the actual and desired values and that a check of the length of the document is also provided for. Figure 6 shows a timer ZG for generating pulses at a constant rate. As an alternative, the pulse rate may be derived from the transport mechanism. To check the length of a document, these pulses are counted by a counter ZA as long as the gate G is held open by an output signal of the detector D2 for transmitted light.The number of pulses which have been counted is proportional to the length of the document when the document is transported past the optical transducer head at a constant velocity or when timer ZG is replaced by a position signal generator, which is coupled to the transporting mechanism. The measured value is compared in the digital comparator DCO with the desired length, which has been stored.

When the actual length of the document agrees with the desired length or the deviation from the desired length is within a permissible tolerance, the digital comparator DCO delivers a signal to an AND-gate 20.

The transmitted light and the scattered light are sensed by detectors D2 and D1, which may consist of photodiodes or phototransistors. Signals representing the sensed luminance are delivered by the detectors D2 and D1 to respective amplifiers V2, V1, which are connected to modules in the form of sample-and-hold circuits SH. The latter are connected to comparators C, the outputs of which are connected to the ANDgate 20. The latter delivers at its output an E/F a signal which gives an indication "genuine" or "counterfeit".

The measurement is performed as follows: As soon as the leading edge of a document 9 to be checked appears under the transducer head 18, the sequence controller A is started, e.g. by the detector D2 for transmitted light. The sequence controller is connected to the control inputs of the modules SH and triggers the modules SH, which are associated with respective points of measurement at adjustable times, e.g. at three times, corresponding to the number of points of measurement. Each of the output signals generated by the detectors D1, D2 at the times at which the modules SH are triggered is fed to the associated comparator C and is compared therein with the desiredvalue signal. A signal is applied to the AND -gate only when the actual value is within the acceptable tolerance (or window).

WHAT WE CLAIM IS: 1. Apparatus for checking documents, such as bank notes, in which a document is moved by a transport mechanism in a single direction in the plane of the document, beneath a light ray directed perpendicularly towards the document at selected portions thereof which exhibit a print, and the scattered light emerging at a predetermined angle is applied to a detector, the (luminance) signal which is generated by the detector being fed to an evaluating circuit, in which the signal generated by the detector in response to the scattered light which emerges at the predetermined angle is compared with a standard-value signal obtained when an original or specimen document is checked under the same conditions at the corresponding portions, and wherein the detector for scattered light is connected to modules in the form of sample and hold circuits, equal in number to the number of said selected portions, and connected in parallel with each other and having control inputs connected to a sequence controller, which is responsive to output signals of a timer or of a position signal generator which in turn is responsive to the operation of the transport mechanism, each module being connected to a comparator to enable its output to be compared with the aforementioned value, the outputs of the comparators being connected respectively to the inputs of a common AND-gate which has an output for controlling the further transport of the document.

2. Apparatus as claimed in claim 1 in which transmitted light emerging from the document on the opposite side to the light source is applied to a further detector, the signal generated thereby being fed to an evaluating circuit for comparison with an appropriate standard-valve signal obtained under the same conditions at a corresponding selected portion of the original or specimen document, the further detector also being connected to further modules arranged, functioning and connected as the originally-mentioned modules.

3. Apparatus as claimed in claim 1 or 2 wherein amplifiers are interposed between the or each detector and the associated modules.

4. Apparatus as claimed in claim 1, 2 or 3 wherein the output signal of the timer or position signal generator is applied to a counter connected to a length comparator, the output of which is fed to one of the inputs of the AND-gate.

5. Apparatus for checking documents, substantially as described hereinbefore with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. are connected to comparators C, the outputs of which are connected to the ANDgate 20. The latter delivers at its output an E/F a signal which gives an indication "genuine" or "counterfeit". The measurement is performed as follows: As soon as the leading edge of a document 9 to be checked appears under the transducer head 18, the sequence controller A is started, e.g. by the detector D2 for transmitted light. The sequence controller is connected to the control inputs of the modules SH and triggers the modules SH, which are associated with respective points of measurement at adjustable times, e.g. at three times, corresponding to the number of points of measurement. Each of the output signals generated by the detectors D1, D2 at the times at which the modules SH are triggered is fed to the associated comparator C and is compared therein with the desiredvalue signal. A signal is applied to the AND -gate only when the actual value is within the acceptable tolerance (or window). WHAT WE CLAIM IS:

1. Apparatus for checking documents, such as bank notes, in which a document is moved by a transport mechanism in a single direction in the plane of the document, beneath a light ray directed perpendicularly towards the document at selected portions thereof which exhibit a print, and the scattered light emerging at a predetermined angle is applied to a detector, the (luminance) signal which is generated by the detector being fed to an evaluating circuit, in which the signal generated by the detector in response to the scattered light which emerges at the predetermined angle is compared with a standard-value signal obtained when an original or specimen document is checked under the same conditions at the corresponding portions, and wherein the detector for scattered light is connected to modules in the form of sample and hold circuits, equal in number to the number of said selected portions, and connected in parallel with each other and having control inputs connected to a sequence controller, which is responsive to output signals of a timer or of a position signal generator which in turn is responsive to the operation of the transport mechanism, each module being connected to a comparator to enable its output to be compared with the aforementioned value, the outputs of the comparators being connected respectively to the inputs of a common AND-gate which has an output for controlling the further transport of the document.

2. Apparatus as claimed in claim 1 in which transmitted light emerging from the document on the opposite side to the light source is applied to a further detector, the signal generated thereby being fed to an evaluating circuit for comparison with an appropriate standard-valve signal obtained under the same conditions at a corresponding selected portion of the original or specimen document, the further detector also being connected to further modules arranged, functioning and connected as the originally-mentioned modules.

3. Apparatus as claimed in claim 1 or 2 wherein amplifiers are interposed between the or each detector and the associated modules.

4. Apparatus as claimed in claim 1, 2 or 3 wherein the output signal of the timer or position signal generator is applied to a counter connected to a length comparator, the output of which is fed to one of the inputs of the AND-gate.

5. Apparatus for checking documents, substantially as described hereinbefore with reference to the accompanying drawings.