Method and apparatus for currency discrimination

• US 7,248,731 B2
• Filed: 03/18/2003
• Issued: 07/24/2007
• Est. Priority Date: 05/19/1992
• Status: Expired due to Fees

• Current Assignee: Cummins-Allison Corporation (Crane Company)
• Original Assignee: Cummins-Allison Corporation (Crane Company)
• Inventors: Bauch, Aaron M., Graves, Bradford T., Stromme, Lars R., Raterman, Donald
• Primary Examiner(s): Tran; Phuoc
• Application Number:
  US10/391,111
• Publication Number:
  US 20030174874A1
• Time in Patent Office: 1,589 Days
• Field of Search: 382/135, 382/218, 382/321, 382/323, 250/556, 250/372, 209/534
• US Class Current: 382/135
• CPC Class Codes: B65H 2301/541 Counting
• CPC Class Codes: B65H 2557/514 ultraviolet
• CPC Class Codes: B65H 2701/1912 Banknotes, bills and cheques or the like
• CPC Class Codes: B65H 3/063 separating from the bottom of pile B65H3/0615, B65H3/0623 take precedence
• CPC Class Codes: G06Q 20/18 involving self-service terminals [SST], vending machines, kiosks or multimedia terminals
• CPC Class Codes: G07D 11/50 Sorting or counting valuable papers
• CPC Class Codes: G07D 7/12 Visible light, infrared or ultraviolet radiation
• CPC Class Codes: G07D 7/1205 Testing spectral properties
• CPC Class Codes: G07D 7/121 Apparatus characterised by sensor details
• CPC Class Codes: G07D 7/162 Length or width
• CPC Class Codes: G07D 7/20 Testing patterns thereon G07D7/004, G07D7/005 take precedence
• CPC Class Codes: G07D 7/205 Matching spectral properties
• CPC Class Codes: G07F 19/20 Automatic teller machines [ATMs]
• CPC Class Codes: G07F 7/04 by paper currency

Abstract

An improved method and apparatus for discriminating between currency bills of different denominations uses an optical sensing and correlation technique based on the sensing of bill reflectance characteristics obtained by illuminating and scanning a bill along one of its dimensions. A series of detected reflectance signals are obtained by sampling and digitally processing, under microprocessor control, the reflected light at a plurality of predefined sample points as a currency bill is moved across an illuminated strip with a preselected dimension parallel to the direction of transport of the bill. The sample data is subjected to digital processing, including a normalizing process, whereby the reflectance data represents a characteristic pattern that is unique for a given bill denomination and incorporates sufficient distinguishing features between characteristic patterns for discriminating between different currency denominations. A plurality of master characteristic patterns are generated and stored using original bills for each denomination of currency to be detected. The pattern generated by scanning a bill under test and processing the data samples is compared with each of the prestored master patterns to generate, for each comparison, a correlation number representing the extent of similarity between corresponding ones of the plurality of data samples for the compared patterns. Denomination identification is based on designating the scanned bill as belonging to the denomination corresponding to the stored master pattern for which the correlation number resulting from pattern comparison is determined to be the highest, subject to a bi-level threshold of correlation.

Claims

1. An improved method for discriminating between currency bills of different denominations comprising the acts of:

illuminating a predetermined section of a currency bill by focusing at least one strip of light thereupon;

detecting the light reflected off said illuminated section of said bill to generate an analog reflectance signal;

generating relative lateral displacement between said strip of light and said bill so as to illuminate and optically scan successive sections of said bill along a predetermined dimension thereof;

obtaining a series of analog reflectance signals corresponding to light reflected from each of said successive bill sections;

digitizing and processing said series of analog reflectance signals to yield a set of digital data samples which, in combination, represent a data pattern characteristic of the currency denomination of said bill;

generating and storing a set of master characteristic patterns corresponding to optical scanning of original bills of each of the different currency denominations to be discriminated;

dividing at least one of (1) said data pattern and (2) said master characteristic patterns into a plurality of sections, and shifting selected ones of said sections relative to each other, and

comparing said data pattern for said scanned currency bill to each of said stored master patterns to determine the degree of correlation therebetween, and thereby to identify the denomination of said currency bill.

2. The method of claim 1, wherein said dividing act includes shifting different ones of said sections relative to each other by different amounts.

3. The method of claim 2, wherein said dividing act includes progressively shifting samples in successive ones of said sections.

4. The method of claim 3, wherein if said degree of correlation fails to meet a predetermined threshold, said dividing act is repeated using a progressively increasing number of sections in said plurality of sections.

5. The method of claim 1, wherein said dividing act includes measuring shrinkage of said bill, the number of sections in said plurality of sections being directly proportional to the measured shrinkage.

6. The method of claim 1, wherein said dividing act includes dividing each of said master characteristic patterns into a progressively increasing number of sections, progressively shifting samples in successive ones of said sections for each of said number of sections to generate a plurality of shifted patterns for each of said master characteristic patterns, and storing in a memory said plurality of shifted patterns for each of said master characteristic patterns.

7. The method of claim 6, wherein said comparing act includes comparing said data pattern for said scanned currency bill to each of said stored master patterns and said stored plurality of shifted patterns to determine the degree of correlation therebetween.

8. The method of claim 6, wherein each of said plurality of shifted patterns correspond to different degrees of shrinkage for said bill, and wherein said comparing act includes comparing said data pattern for said scanned currency bill to said stored patterns corresponding to a measured degree of shrinkage for said bill.

9. The method of claim 1, further including the act of positively identifying said scanned bill as having the denomination corresponding to the stored master pattern for which the degree of correlation is found to be the highest and at least equal to a predefined correlation threshold.

10. An improved method for discriminating between currency bills of different denominations comprising the acts of:

illuminating a predetermined section of a currency bill by focusing at least one strip of light thereupon;

detecting the light reflected off said illuminated section of said bill to generate an analog reflectance signal;

generating relative lateral displacement between said strip of light and said bill so as to illuminate and optically scan successive sections of said bill along a predetermined dimension thereof;

obtaining a series of analog reflectance signals corresponding to light reflected from each of said successive bill sections;

digitizing and processing said series of analog reflectance signals to yield a set of digital data samples which, in combination, represent a data pattern characteristic of the currency denomination of said bill;

generating and storing a et of master characteristic patterns corresponding to optical scanning of original bills of each of the different currency denominations to be discriminated;

generating and storing a set of shifted patterns by dividing each of said master characteristic patterns into a plurality of sections and by shifting selected ones of said sections relative to each other; and

comparing said data pattern for said scanned currency bill to selected ones of said stored master characteristic patterns and said stored shifted patterns to determine the degree of correlation therebetween, and thereby to identify the denomination of said currency bill.

11. The method of claim 10, wherein said act of generating and storing a set of shifted patterns includes dividing each of said master characteristic patterns into a progressively increasing number of sections, progressively shifting samples in successive ones of said sections for each of said number of sections to generate a plurality of shifted patterns for each of said master characteristic patterns, and storing said plurality of shifted patterns for each of said master characteristic patterns.

12. The method of claim 10, wherein each of said shifted patterns correspond to different degrees of shrinkage for said bill, and wherein said comparing act includes comparing said data pattern for said scanned currency bill to said stored patterns corresponding to a measured degree of shrinkage for said bill.

13. A currency evaluation device for receiving a stack of currency bills, rapidly evaluating all the bills in the stack, and then re-stacking the bills, said device comprising;

a feed mechanism for receiving a stack of currency bills and feeding said bills in the direction of a predetermined dimension of the bills, one at a time, to a feed station

a bill transport mechanism for transporting bills at a first operating speed, in the direction of the predetermined dimension of the bills, from said feed station to a stacking station;

a stationary optical scanning head located between said feed and stacking stations for scanning a preselected segment of a central portion of each bill transported between said stations by said transport mechanism, said scanning head including at least one light source for illuminating a strip of said preselected segment of a bill, and at least one detector for receiving reflected light from the illuminated strip on the bill and producing an output signal representing variations in the intensity of the reflected light;

means for sampling said output signal at preselected intervals as a bill is moved across said scanning head in the direction of the predetermined dimension of the bill;

a memory for storing characteristic signal samples produced by scanning said preselected segments of bills of different denominations with said scanning head and sampling said output signal at said preselected intervals;

signal processing means for receiving said signal samples and determining the denomination of each scanned bill by comparing said stored signal samples with said output signal samples produced by the scanning of each bill with said scanning head; and

means, responsive to said signal processing means failing to determine the denomination of a particular scanned bill, for decelerating said bill transport mechanism from said first operating speed to a second operating speed such that during the deceleration of said bill transport mechanism, said particular scanned bill is transported to said stacking station and a next upstream bill from said particular scanned bill is scanned by said scanning head.

14. The currency evaluation device of claim 13, wherein said decelerating means decelerates said bill transport mechanism to said second operating speed at such a rate that said scanning head completes scanning said next upstream bill prior to said bill transport mechanism reaching said second operating speed.

15. The currency evaluation device of claim 13, wherein said second operating speed is approximately one-third of said first operating speed.

16. The currency evaluation device of claim 13, wherein said decelerating means decelerates said bill transport mechanism from said second operating speed to a third operating speed after said next upstream bill is scanned by said scanning head.

17. The currency evaluation device of claim 13, wherein said decelerating means decelerates said bill transport mechanism from said second operating speed to a complete halt prior to a bill located upstream from said next upstream bill being scanned by said scanning head.

18. The currency evaluation device of claim 13, wherein each of said output signal samples and said stored signal samples is proportional to the intensity of the light reflected from a different strip of said preselected segment of a bill.

19. A currency evaluation device for processing a stack of currency bills, said device comprising:

a feed mechanism for receiving a stack of currency bills and feeding said bills, one at a time, to a bill transport mechanism, said bill transport mechanism transporting bills at a first operating speed from said feed mechanism to a stacking station;

a scanning head located between said feed mechanism and said stacking station for scanning a segment of each bill transported between said feed mechanism and said stacking station by said transport mechanism, said scanning head producing an output signal representing variations in characteristic information along said segment of each bill;

a memory for storing characteristic information produced by scanning bills of different denominations;

a processor adapted to receive said output signal and determine the denomination of scanned bills by comparing said stored characteristic information with informatiion derived from said output signal produced by scanning bills with said scanning head; and

a processor adapted to control the operation of said bill transport mechanism and adapted to decelerate said bill transport mechanism from said first operating speed to a second operating speed such that during the deceleration of said bill transport mechanism a particular scanned bill is transported to said stacking station and a next upstream bill from said particular scanned bill is scanned by said scanning head.

20. The currency evaluation device of claim 19, wherein said decelerating means decelerates said bill transport mechanism to said second operating speed at such a rate that said scanning head completes scanning said next upstream bill prior to said bill transport mechanism reaching said second operating speed.

21. The currency evaluation device of claim 19, wherein said second operating speed is approximately one-third of said first operating speed.

22. The currency evaluation device of claim 19, wherein said decelerating means decelerates said bill transport mechanism from said second operating speed to a third operating speed after said next upstream bill is scanned by said scanning head.

23. The currency evaluation device of claim 19, wherein said decelerating means decelerates said bill transport mechanism from said second operating speed to a complete halt prior to a bill located upstream from said next upstream bill being scanned by said scanning head.

24. The currency evaluation device of claim 19, wherein each of said output signal samples and said stored signal samples is proportional to the intensity of the light reflected from a different strip of said preselected segment of a bill.

25. An improved method for discriminating between currency bills of different denominations comprising the acts of:

illuminating a predetermined section of a currency bill with at least one strip of light;

detecting the light reflected off said illuminated section of said bill to generate a reflectance signal;

generating relative lateral displacement between said strip of light and said bill so as to illuminate and optically scan successive sections of said bill along a predetermined dimension thereof;

obtaining a reflectance signal corresponding to light reflected from each of said successive bill sections;

processing said reflectance signal to yield a set of digital data samples which, in combination, represent a data pattern characteristic of the currency denomination of said bill;

retrieving from a memory a set of master characteristic patterns corresponding to optical scanning of bills of each of the different currency denominations to be discriminated;

dividing at least one of (1) said data pattern and (2) said master characteristic patterns into a plurality of sections, and shifting selected ones of said sections relative to each other to generate at least one of (1) a shifted data pattern and (2) shifted master characteristic patterns;

comparing at least one of (1) said shifted data pattern for said scanned currency bill to each of said stored master patterns and (2) said data pattern for said scanned bill and said shifted master characteristic patterns; and

determining the denomination of said currency bill based on the act of comparing.

26. The method of claim 25, wherein said dividing act includes shifting different ones of said sections relative to each other by different amounts.

27. The method of claim 26, wherein said dividing act includes progressively shifting samples in successive ones of said sections.

28. The method of claim 27, wherein if said comparing fails to permit the denomination to be determined, said dividing act is repeated using a progressively increasing number of sections in said plurality of sections.

29. The method of claim 25, further comprising measuring shrinkage of said bill and wherein the number of sections in said plurality of sections of said dividing act is directly proportional to the measured shrinkage.

30. The method of claim 25, wherein said dividing act includes dividing each of said master characteristic patterns into a progressively increasing number of sections, progressively shifting samples in successive ones of said sections for each of said number of sections to generate a plurality of shifted patterns for each of said master characteristic patterns, and storing in a memory said plurality of shifted patterns for each of said master characteristic patterns.

31. The method of claim 30, wherein said comparing act includes comparing said data pattern for said scanned currency bill to each of said stored master patterns and said stored plurality of shifted patterns to determine a degree of correlation therebetween.

32. The method of claim 30, wherein each of said plurality of shifted patterns correspond to different degrees of shrinkage for said bill, and wherein said comparing act includes comparing said data pattern for said scanned currency bill to said stored patterns corresponding to a measured degree of shrinkage for said bill.

33. The method of claim 25, further including an act of positively identifying said scanned bill as having the denomination corresponding to the stored master pattern for which a degree of correlation is found to be the highest and at least equal to a predefined correlation threshold.

34. An improved method for discriminating between currency bills of different denominations comprising the acts of:

illuminating a predetermined section of a currency bill with at least one strip of light;

detecting light reflected off said illuminated section of said bill to generate a reflectance signal;

generating relative lateral displacement between said strip of light and said bill so as to illuminate and optically scan successive sections of said bill along a predetermined dimension thereof;

obtaining a reflectance signal corresponding to light reflected from each of said successive bill sections;

digitizing and processing said analog reflectance signal to yield a set of digital data samples which, in combination, represent a data pattern characteristic of the currency denomination of said bill;

retrieving from a memory a set of master characteristic patterns corresponding to optical scanning of bills of each of the different currency denominations to be discriminated;

retrieving from a memory a set of shifted master patterns which were generated by dividing each of said master characteristic patterns into a plurality of sections and by shifting selected ones of said sections relative to each other;

comparing said data pattern for said scanned currency bill to selected ones of said stored master characteristic patterns and said stored shifted patterns; and

determining the denomination of said currency bill based on the act of comparing.

35. The method of claim 34, wherein said set of shifted master patterns were generated by dividing each of said master characteristic patterns into a progressively increasing number of sections, progressively shifting samples in successive ones of said sections for each of said number of sections to generate a plurality of shifted patterns for each of said master characteristic patterns, and storing said plurality of shifted patterns for each of said master characteristic patterns.

36. The method of claim 34, wherein each of said shifted patterns correspond to different degrees of shrinkage for said bill, and wherein said comparing act includes comparing said data pattern for said scanned currency bill to said stored patterns corresponding to a measured degree of shrinkage for said bill.