Coin discriminating apparatus

• US 6,340,082 B1
• Filed: 10/22/1999
• Issued: 01/22/2002
• Est. Priority Date: 10/22/1999
• Status: Expired due to Fees

• Current Assignee: Japan Tobacco Inc.
• Original Assignee: Japan Tobacco Inc.
• Inventors: Davis, Richard J., House, Larry J.
• Primary Examiner(s): Bartuska, F. J.
• Application Number:
  US09/422,801
• Time in Patent Office: 823 Days
• Field of Search: 194/317, 194/318, 194/328, 194/330
• US Class Current: 194/317
• CPC Class Codes: G07D 5/005 Testing the surface pattern, e.g. relief
• CPC Class Codes: G07D 5/08 Testing the magnetic or electric properties

Abstract

A coin discriminating apparatus which permits easy and reliable determination and identification of coins with the use of eddy currents induced in coins by an electromagnetic field. The electromagnetic field varies depending on the material, thickness, etc. of the coin, and the impedance of the coil varies under the influence of the induced eddy current. Eddy current induction coils are successively excited to apply a high-frequency electromagnetic field to the coin over an entire surface thereof, and impedances of the eddy current induction coils, which vary under the influence of the eddy current induced in the coin by the high-frequency electromagnetic field, are measured to obtain information on surface displacement irregularities of a stamp pattern on the coin surface. Also, a low-frequency electromagnetic field is applied to the coin by using the eddy current induction coils, and impedances of the individual coils, which vary under the influence of the eddy current induced in the coin by the low-frequency electromagnetic field, are measured to obtain information on the material of the coin and to perform coin discrimination. Features of the stamp pattern in particular, which are represented by surface displacement irregularities, are acquired in the form of a histogram showing impedance along the abscissa and the numbers of coils along the ordinate with outputs in specified ranges along the ordinate.

Claims

1. A coin discriminating apparatus for discriminating denominations of coins, comprising:

a plurality of eddy current induction coils arranged two-dimensionally so as to face a surface of a coin;

high-frequency exciting means for exciting said eddy current induction coils at high frequency to apply a high frequency electromagnetic field locally to the coin and thereby induce eddy current in the coin;

low-frequency exciting means for exciting said eddy current induction coils at low frequency to apply a low-frequency electromagnetic field to the coin and thereby induce eddy current in the coin;

impedance measuring means for detecting impedances of said eddy current induction coils applying the electromagnetic field to the coin, the impedances varying depending on the eddy current induced in the coin;

material determining means for comparing the impedances of said eddy current induction coils detected when said eddy current induction coils are excited at low frequency with a standard impedance value obtained in advance using a true coin, to determine a material of the coin;

feature extracting means for obtaining information on surface displacement irregularities of a stamp pattern on the surface of the coin, based on the impedances of said eddy current induction coils detected when said eddy current induction coils are excited at high frequency, wherein said feature extracting means comprises histogram creating means for creating, based on the impedances of said eddy current induction coils detected when said eddy current induction coils are excited at high frequency, a histogram showing distribution of the impedances as feature information indicative of the information on irregularities of the stamp pattern on the surface of the coin; and

pattern determining means for comparing the information on surface displacement irregularities of the stamp pattern obtained by said feature extracting means with information on irregularities of a stamp pattern of a true coin obtained beforehand, to identify a denomination of the coin.

2. The coin discriminating apparatus according to claim 1, wherein said plurality of eddy current induction coils are arranged on a plane in a rectangular grid or other suitable geometry form to constitute a coil array,

said high-frequency exciting means successively excites all said eddy current induction coils constituting the coil array at high frequency, thereby scanning the entire surface of the coin, and said low-frequency exciting means excites only specified ones of said eddy current induction coils in the coil array at low frequency.

3. The coin discriminating apparatus according to claim 2, wherein said specified eddy current induction coils excited at low frequency comprise a predetermined number of eddy current induction coils located approximately in a central portion of the matrix constituted by said plurality of eddy current induction coils.

4. The coin discriminating apparatus according to claim 1, further comprising coin diameter measuring means for measuring a diameter of the coin based on the impedances of said eddy current induction coils detected when said eddy current induction coils are excited at high frequency.

5. The coin discriminating apparatus according to claim 1, wherein said plurality of eddy current induction coils comprise a coil array of high frequency-excited eddy current induction coils and a low frequency-excited eddy current induction coil arranged side by side with respect to the coil array.

6. The coin discriminating apparatus according to claim 1, wherein said plurality of eddy current induction coils comprise a coil array of high frequency-excited eddy current induction coils and a low frequency-excited eddy current induction coil arranged face to face with respect to the coil array.

7. The coin discriminating apparatus according to claim 1, further comprising coin thickness measuring means for measuring a thickness of the coin based on the impedances of said eddy current induction coils detected when said eddy current induction coils are excited at high frequency.

8. The coin discriminating apparatus according to claim 1, further comprising image processing means for acquiring the information on irregularities of the stamp pattern on the surface of the coin as a two- or three-dimensional image, based on the impedances of said eddy current induction coils detected when said eddy current induction coils are excited at high frequency.

9. The coin discriminating apparatus according to claim 1, wherein said high-frequency exciting means excites said eddy current induction coils at a frequency of about 700 kHz to 1 MHz to produce a high-frequency electromagnetic field, and said low-frequency exciting means excites said eddy current induction coils at a frequency of about 10 to 100 kHz to produce a low-frequency electromagnetic field.

10. The coin discriminating apparatus according to claim 1, wherein said high-frequency exciting means and said low-frequency exciting means are constituted by a voltage-controlled controlled oscillator which oscillation frequency is variably controlled by a control voltage externally applied thereto, and

the control voltage is varied to switch the frequency for exciting said eddy current induction coils, thereby making the voltage-controlled oscillator function as said high-frequency exciting means or said low-frequency exciting means.

11. The coin discriminating apparatus according to claim 1, wherein said plurality of eddy current induction coils are selectively oscillated by being applied with an output from a voltage-controlled oscillator via a multiplexer, and

the multiplexer scans said eddy current induction coils to be applied with the output of the voltage-controlled oscillator at high speed.

12. The coin discriminating apparatus according to claim 1, wherein the eddy current induction coils excited at low frequency are separate from the eddy current induction coils excited at high frequency.

13. The coin discriminating apparatus according to claim 1, wherein said low-frequency exciting means selectively excites said eddy current induction coils at a plurality of different frequencies close to 100 kHz or continuously varies an excitation frequency for said eddy current induction coils within a frequency range close to 100 kHz, to produce a low-frequency electromagnetic field to be applied to a plurality of portions of the coin.

14. The coin discriminating apparatus according to claim 1, wherein said plurality of eddy current induction coils are arranged on a plane in matrix form to constitute a coil array, and

the coil array includes two coil arrays arranged so as to face obverse and reverse surfaces of the coin, respectively.

15. A coin discriminating apparatus for discriminating denominations of coins, comprising:

a plurality of eddy current induction coils arranged two-dimensionally so as to face a surface of a coin;

high-frequency exciting means for exciting said eddy current induction coils at high frequency to apply a high frequency electromagnetic field locally to the coin and thereby induce eddy current in the coin;

low-frequency exciting means for exciting said eddy current induction coils at low frequency to apply a low-frequency electromagnetic field to the coin and thereby induce eddy current in the coin, and wherein said plurality of eddy current induction coils are arranged on a plane in a rectangular grid or other suitable geometric form to constitute a coil array, said high-frequency exciting means successively excites each of said eddy current induction coils constituting the coil array at high frequency, thereby scanning the entire surface of the coin, and said low-frequency exciting means excites only specified ones of said eddy current induction coils in the coil array at low frequency;

impedance measuring means for detecting impedances of said eddy current induction coils applying the electromagnetic field to the coin, the impedances varying depending on the eddy current induced in the coin;

material determining means for comparing the impedances of said eddy current induction coils detected when said eddy current induction coils are excited at low frequency with a standard impedance value, obtained in advance using a true coin, to determine a material of the coin;

feature extracting means for obtaining information on surface displacement irregularities of an embossing on the surface of the coin, based on the impedances of said eddy current induction coils detected when said eddy current induction coils are excited at high frequency; and

pattern determining means for comparing the information on surface displacement irregularities of the embossing obtained by said feature extracting means with information on irregularities of an embossing of the true coin obtained beforehand, to identify a denomination of the coin.

16. The coin discriminating apparatus according to claim 15, wherein said high-frequency exciting means and said low-frequency exciting means are constituted by a voltage controlled oscillator which oscillation frequency is variably controlled by a control voltage externally applied, thereto, and the control voltage is varied to switch the frequency for exciting said eddy current induction coils, thereby making the voltage-controlled oscillator function as said high-frequency exciting means or said low-frequency exciting means.

17. The coin discriminating apparatus according to claim 15, wherein said plurality of eddy current induction coils are selectively oscillated by being applied with an output from a voltage-controlled oscillator via a multiplexer, and

the multiplexer scans said eddy current induction coils to be applied with the output of the voltage-controlled oscillator at high speed.

18. The coin discriminating apparatus according to claim 15 further comprising at least one of the following elements:

coin diameter measuring means for measuring a diameter of the coin based on the impedances of said eddy current induction coils detected when said eddy current induction coils are excited at high frequency; and

coin thickness measuring means for measuring a thickness of the coin based on the impedances of said eddy current induction coils detected when said eddy current induction coils are excited at high frequency.

19. The coin discriminating apparatus according to claim 15, further comprising image processing means for acquiring the information on irregularities of the stamp pattern on the surface of the coin as a two- or three dimensional image, based on the impedances of said eddy current induction coils detected when said eddy current induction coils are excited at high frequency.

20. The coin discriminating apparatus according to claim 15, wherein each of said plurality of eddy current induction coils has a size smaller than outer diameters of the coin, and said plurality of eddy current induction coils are arranged at a pitch smaller than the outer diameter of the coin to from a coil array having a size larger than the outer diameter of the coin.