Coin-validation arrangement

• US 20040084278A1
• Filed: 02/28/2003
• Published: 05/06/2004
• Est. Priority Date: 02/09/2000
• Status: Active Grant

• Current Assignee: Marconi UK Intellectual Property Limited (Marconi Holdings Company Limited)
• Original Assignee: Marconi UK Intellectual Property Limited (Marconi Holdings Company Limited)
• Inventors: Churchman, James, Harris, Jeffrey A, Sharman, Darren
• Granted Patent: US 7,243,772 B2
• Time in Patent Office: Days
• US Class Current: 194/302
• CPC Class Codes: G07D 5/00 Testing specially adapted to determine the identity or genuineness of coins, e.g. for segregating coins which are unacceptable or alien to a currency
• CPC Class Codes: G07D 5/08 Testing the magnetic or electric properties

Abstract

A coin-validation arrangement in which a wavelet analysis is used to derive accurate information from signals related to coin sensors placed in the path of an input coin, this information being compared with corresponding information relating to sample coins, the result of the comparison giving rise to a “pass/fail” validation decision on the input coin. The information may be derived from a sampling of the sensor-related signal, a measurement of signal amplitudes for each point and a correlation of each amplitude with the corresponding amplitude of one or more preselected wavelets to provide a set of correlation coefficients. In an alternative embodiment the sampled sensor-related signal is subjected to a discrete wavelet transform operation using high-and low-pass filtering and subsequent subsampling stages, thereby producing a set of DWT coefficients. In either case the number of coefficients used in the comparison process may be reduced, thereby saving processing power.

Claims

1. Coin validation arrangement comprising a coin-guide means for guiding an input coin (14, 16) along a predetermined coin path, one or more coin sensors (L1-L3) disposed in the path of the input coin, a circuit means for sensing the effect of the input coin on the parameter of the one or more sensors and providing an input-coin signal representative of said effect, and means for sampling the input-coin signal to produce a sequence of sample values, characterised in that the arrangement comprises means for multiplying respective values of a plurality of detection waveforms characteristic of a particular coin, each detection waveform comprising a sequence of numerical values, by those of the input-coin signal, and for summing the products to produce an evaluation value corresponding to each detection waveform, and means for determining whether each of the evaluation values falls within predetermined limits, in order to validate the coin.

2. Validation arrangement as claimed in claim 1, wherein the one or more detection waveforms each satisfy the condition

3. Validation arrangement as claimed in claim 2, wherein the one or more detection waveforms each satisfy the condition

4. Validation arrangement as claimed in any one of the preceding claims, wherein the one or more detection waveforms comprise a single first detection-waveform defined by a first sequence of numerical values and a plurality of detection waveforms defined by respective sequences of numerical values, the respective sequences being shorter than the first sequence.

5. Validation arrangement as claimed in claim 4, wherein the plurality of detection waveforms comprises two second detection-waveforms having respective second sequences shorter than the first sequence and four third detection-waveforms having respective third sequences shorter than the second sequences.

6. Validation arrangement as claimed in claim 5, wherein the second sequences are equal to each other and the third sequences are equal to each other.

7. Validation arrangement as claimed in claim 6, wherein the second sequences are one-half the length of the first sequence and the third sequences are one-half the length of the second sequences.

8. Validation arrangement as claimed in claim 7, wherein the second sequences follow directly on from each other and the third sequences follow directly on from each other.

9. Validation arrangement as claimed in any one of claims 4 to 8, wherein one or more of said sequences is extended such that it contains a number of values equal to the number of samples in the sampled input-coin signal, those values lying outside the core of values which define the particular detection waveform having a value of zero.

10. Validation arrangement as claimed in any one of the preceding claims, wherein the one or more detection waveforms are chosen such as to provide a strong correlation with the sampled input-coin signal.

11. Validation arrangement as claimed in any one of the preceding claims, wherein an amplitude of the signal is sampled at a plurality of points in time to form a signal vector, the signal vector is correlated with one or more detection vectors associated with respective said one or more detection waveforms thereby to provide respective correlation vectors, one or more of which are used to provide said validation indication.

12. Validation arrangement as claimed in claim 11, wherein coefficients of the one or more correlation vectors are compared with corresponding coefficients of respective reference vectors associated with a sample input coin or set of coins, a result of this comparison being used to provide said validation indication.

13. Validation arrangement as claimed in claim 12, wherein said respective reference vectors are associated with a plurality of sample input coins or set of coins, thereby to determine an acceptable spread of allowable comparison values.

14. Validation arrangement as claimed in claim 11, wherein coefficients of each of the one or more correlation vectors are processed to provide one or more evaluation coefficients, said one or more evaluation coefficients being used to provide said validation indication.

15. Validation arrangement as claimed in claim 14, wherein said one or more evaluation coefficients are compared with corresponding coefficients associated with a sample input coin or set of coins, a result of this comparison being used to provide said validation indication.

16. Validation arrangement as claimed in claim 15, wherein said corresponding coefficients are associated with a plurality of sample input coins or set of coins, thereby to determine an acceptable spread of allowable comparison values.

17. Validation arrangement as claimed in any one of claims 14 to 16, wherein said correlation coefficients are processed to provide a single evaluation value.

18. Validation arrangement as claimed in claim 17, wherein said processing of the correlation coefficients comprises the summing together of the correlation coefficients.

19. Validation arrangement as claimed in any one of claims 15 to 18, wherein said validation indication is provided on the basis of a function involving said evaluation coefficients and said sample-coin coefficients.

20. Validation arrangement as claimed in claim 19, wherein said function is expressed as:

ƒ

=w₁(Ai₁−

As₁)²+W₂(Ai₂−

As₂)²+ . . . +w_n(Ai_n−

As_n)²

where Ai_1-n are n evaluation coefficients of the input coin, As_1-n are n sample-coin coefficients and w_1-n are n weighting factors associated with the respective evaluation and sample-coin coefficients.

21. Validation arrangement as claimed in any one of claims 1 to 20, in which the detection waveforms are wavelets.

22. Validation arrangement as claimed in any one of the preceding claims, wherein one or more of the coin sensors are inductive and the parameter is inductance.

23. Validation arrangement as claimed in any one of the preceding claims, wherein one or more of the coin sensors are capacitive and the parameter is capacitance.

24. Validation arrangement substantially as shown in, or as hereinbefore described with reference to, Table 1 and FIG. 6 of the drawings, or FIG. 10 of the drawings.

25. Method for validating a coin inserted into a coin mechanism having a coin-guide means for guiding an input coin along a predetermined coin path and one or more coin sensors disposed in the path of the input coin, the method comprising sensing the effect of the input coin on the parameter of the one or more sensors and providing an input-coin signal representative of said effect, and sampling the input-coin signal to produce a sequence of sample values, characterised by the step of multiplying respective values of a plurality of detection waveforms characteristic of a particular coin, each detection waveform comprising a sequence of numerical values, by those of the input-coin signal, and of summing the products to produce an evaluation value corresponding to each detection waveform, and determining whether each of the evaluation values falls within predetermined limits, in order to validate the coin.

26. Method as claimed in claim 25, in which the detection waveforms are wavelets.

27. Method as claimed in claim 26, wherein the input-coin signal is subjected to a discrete wavelet transform (DWT) process which yields a set of transform coefficients, said transform coefficients are compared with a corresponding set of coefficients relating to a sample coin or set of coins, and said decision is made on the basis of this comparison.

28. Method as claimed in claim 27, wherein the input-coin signal is sampled, the sampled signal is subjected to low-pass and high-pass filtering and subsequent subsampling by a factor of 2, and the subsampled results of the high-pass filtering form part of the set of transform coefficients, the low-pass subsampled values being subjected to similar low-pass and high-pass filtering and subsequent subsampling, the results of that subsampled high-pass filtering likewise forming a part of the transform coefficient set, and so on for a given number of filtering and subsampling operations.

29. Method as claimed in claim 28, wherein the final filtering and subsampling operation occurs when the subsampled high-pass filtering for that stage yields only one coefficient.

30. Method as claimed in claim 28 or claim 29, wherein the filtering and subsampling operations are performed in software.

31. Method for validating a coin substantially as shown in, or as hereinbefore described with reference to, FIG. 6 and Table 1, or FIG. 10 of the drawings.