GB2369710A

GB2369710A - Coin Identification

Info

Publication number: GB2369710A
Application number: GB0029563A
Authority: GB
Inventors: Ezio Panzeri
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-12-04
Filing date: 2000-12-04
Publication date: 2002-06-05
Anticipated expiration: 2020-12-04
Also published as: GB2369710B; GB0029563D0

Abstract

An apparatus for identifying coins 8 comprises a coin path having a free fall portion 10, coins to be detected being in free fall whilst traversing said free fall portion 10 and an optical sensor 12 which is operable to detect opposite edges of a coin 8 traversing said free fall portion 10 to obtain dimensional characteristics of the coin 8 that may be used to identify it. The dimensional characteristics may include a diameter of the coin 8. The dimensional characteristics may include the presence of milling on both said opposite edges of the coin 8 and may also include a groove spacing value of the milling. The optical sensors 12 may comprise two CMOS linear array sensors 12 illuminated by one or more light sources. The coin path may include a stabiliser 6 in the from of two flexible wings which serve to guide said coin 8 to follow a predetermined path through said free fall portion 10. The apparatus may also include an inductive sensor 14 and a capacitive sensor. In an alternative embodiment the invention comprises a method of identifying coins 8.

Description

COIN IDENTIFICATION

This invention relates to the field of coin identification. More particularly, this invention relates to the identification of coins in free fall.

It is known to provide coin identification systems, such as that described in European Patent EP-B-0, 900, 431, that use optical sensors to identify a coin. One possible arrangement for such a system has the coin in free fall as it passes in front of the optical sensors.

An advantage in using a free fall coin identification system is that such systems are well suited to provide fast identification/detection as is required in applications such as gaming and amusement machines. In such systems a user may rapidly insert a stream of coins and the coin identification/detection mechanism should be able to correctly identify/detect these coins and reduce the likelihood of a coin jam occurring due to the inability of a large number of coins to pass through the mechanism in a short period of time. Typical known systems may involve a coin rolling along a ramp or channel past mechanical, optical or other types of sensors. In such systems the rate at which coins may be detected is limited by the speed with which they are able to pass along the ramp or channel together with the need to provide an appropriate spacing between coins as they pass through the system. Free fall systems struggle to accurately identify/detect a large number of different types of coins.

Viewed from one aspect the present invention provides an apparatus for identifying coins, said apparatus comprising: a coin path having a free fall portion, coins to be detected being in free fall whilst traversing said free fall portion; and an optical sensor operable to detect opposite edges of a coin traversing said free fall portion to obtain one or more dimensional characteristics of said coin that may be used to identify said coin.

The invention recognises that in a free fall system there may be a significant variation in the position of coins as they pass through the system, i. e. they are not

sliding along or rolling along a fixed ramp or channel. In order to cope with such variation the invention provides an optical sensor that is operable to detect opposite edges of a coin in free fall past the sensor. Thus, a dimensional characteristic of the coin sufficient to identify the coin may be detected reliably despite variation in the absolute position of the coin passing in front of the sensor.

It will be appreciated that the dimensional characteristic detected could take various forms. One particularly effective form is to detect the diameter of the coin.

Another particularly effective dimensional characteristic is the presence of milling on both of the opposite edges of the coin. The detection of milling on opposite edges of the coin has the significant advantage that whilst roughness or damage at one particular portion on the edge of a coin that may have the appearance of milling at that position, this will be less likely to be falsely detected as milling since the opposite edge is unlikely to show the same characteristics. This significantly enhances the reliability of coin identification based upon milling characteristics.

In more sophisticated identification systems, the groove spacing of milling or the groove depth of milling may be used as a way of identifying particular coins.

Whilst it is possible that the optical sensor may take many different forms, such as a large single sensor allowing detection over a size greater than the maximum size of the coins to be identified, preferred embodiments of the invention utilise two linear array sensors illuminated by one or more light sources with the coin in the free fall portion acting to block light reaching at least some pixels of both linear array sensors such that the shadow cast by the coin can be used to give an indication of a dimensional characteristic of the coin.

Linear array sensors, particularly CMOS sensors are able to provide a high degree of dimensional accuracy in the detection they yield and a high sampling rate.

In order to use the linear array sensors to good effect they are preferably arranged substantially perpendicular to the direction of free fall of the coins.

The performance of the system may be further improved by providing a stabiliser acting to guide the coins to follow a predetermined path through the free fall portion. Whilst such a stabiliser may not be able to remove all the variation in position of the coins, it will at least reduce this variation to a degree that eases the constraints placed upon the rest of the system.

A preferred form of stabiliser is flexible wings, preferably formed of a low friction material such as PTFE, that extend into the coin path and between which the coin passes before entering the free fall portion.

In order to improve the identification accuracy of the system an inductive sensor may be used to detect an inductive characteristic of the coin in addition to the dimensional characteristic detected by the optical sensor. A particularly convenient arrangement for this is to provide the inductive sensor between the two linear array sensors such that the inductive sensor is positioned proximal to the centre of the coin where an accurate inductive characteristic may be more readily obtained.

In preferred embodiments a metal sensor in the form of capacitor plates positioned between the sensor arrays may also be used to measure the capacitance of coins passing through the detector. This may be used instead of or as well as the inductive sensor.

The optical sensor could take various different forms. However, a particularly preferred form of optical sensor includes a source of collimated light including a light source, an aspherical cylindrical lens and a parabolic reflector. This compact arrangement is able to provide a collimated beam of light well suited for detecting a dimensional characteristic using a relatively small number of optical components that may be readily manufactured or are already part of some of the components, such as the light source having a built-in aspherical cylindrical lens.

The light source could take various forms. In some embodiments where dimensional accuracy is not too critical, then a light source such as an LED may be acceptable. However, for improved dimensional accuracy it is preferred that the light source is a laser light source, such as a laser diode.

A particular advantage of optical sensors that may be exploited by the present invention is that it is that they may more readily be provided in the form of waterproof sealed units than electromechanical sensors. Such waterproof sealed units tend to have a higher degree of reliability and allow the flexibility for use of the coin identification mechanisms in relatively harsh environments.

It will be appreciated that the form of the coins identified will typically be currency coins of the type issued by Government Mints. However, the coin could also be in the form of a token coin, such as a gaming token that might be issued in a Casino or a token coin issued as a form of voucher for a product or service to be dispensed under control of the coin mechanism.

Viewed from another aspect the invention provides a method of identifying coins, said method comprising the steps of : providing a coin path having a free fall portion, coins to be detected being in free fall whilst traversing said free fall portion; and detecting opposite edges of a coin traversing said free fall portion using an optical sensor to obtain one or more dimensional characteristics of said coin that may be used to identify said coin.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure I is a side view schematic cross section through a coin detecting/identifying mechanism; Figure 2 is a top view of the system of Figure 1 ; Figure 3 illustrates the detection of milling characteristics on opposite edges of a coin ; Figure 4 illustrates the dimensional characteristics of milling on a coin edge that may be detected;

Figure 5 is a perspective view of a portion of an optical sensor ; and Figure 6 shows plan, cross section and end views of the portion of the optical sensor of Figure 5.

Figure 1 shows a coin identifying/detecting mechanism 2. A coin path through the mechanism 2 follows a coin path as it passes between side walls 4. A stabiliser is formed of PTFE wings 6 extending from the side walls 4 into the coin path and having a gap therebetween. In use a coin 8 (which may be a currency coin or a token coin) pushes between the wings 6 to enter a free fall portion 10 as it passes in front of two CMOS linear array optical sensors 12. An inductive sensor 14 is provided between the two linear array sensors 12 and serves to detect an inductive characteristic of the coin 8 approximately at its core as it passes in front of the inductor sensor 14. A metal sensor (not shown) in the form of capacitor plates positioned between the sensor arrays may also be used to measure the capacitance of coins passing through the detector. This may be used instead of or as well as the inductive sensor 14.

The signals from the linear array sensors 12 are supplied to a microprocessor (not illustrated) operating under computer program control that serves to analyse "shadow"cast by the coin on the linear array sensors 12 to determine a dimensional characteristic of the coin 8. This type of processing is substantially in line with that described in the above mentioned European Patent EP-B-0, 900, 431. One difference from the processing described in this reference is that both edges of the coin 8 are detected by the shadow that they cast. The sum of the pixels upon which a shadow is cast for both of the linear array sensors 12 gives an indication of the diameter of the coin along the line between the two sensors at the position to which the coin has currently fallen. It will be appreciated that as the coin falls past the linear array sensors 12, the detected dimension will increase up to a maximum value corresponding to the full diameter of the coin 8 and then decrease again. The high spatial resolution and high sampling rate provided by the linear array sensors 12 allows variations in the diameter due to milling on the coin edge to be detected as will be discussed later. Such milling detection is a highly useful supplementary

dimensional characteristic to detect in combination with the diameter of the coin to aid identification of a particular coin.

Figure 2 is a top view of the mechanism 2 of Figure 1. Figure 2 additionally shows the light sources 16 that are used to provide collimated beams of laser light 18 that are incident upon the linear array sensors 12. As the coin passes in front of the linear array sensors 12, this collimated light beam is partially interrupted and a shadow whose size may be detected from both edges is cast upon the linear array sensors.

Figure 3 schematically illustrates the detection of milling characteristics at opposite edges of the coin 8. As these characteristics are detected at opposite edges, an increased resistance to false milling measurements is achieved because damage/roughness at one edge portion that may give rise to erroneous readings at that edge portion is highly unlikely to be repeated at the opposite edge portion.

Accordingly, accurate milling dimensional characteristics may be detected when the characteristics are found to substantially match at each edge.

Figure 4 schematically illustrates how the groove spacing W and the groove depth H of milling features on the edge of a coin 8 may be detected by the highly accurate high speed linear array sensors 12. A combination of the coin diameter, the milling spacing and the milling depth together can provide a highly accurate identification of a particular coin and allow a large number of coins to be discriminated between.

Figure 5 schematically illustrates in perspective view the source of collimated light 16 both exploded and assembled. This comprises a laser diode 20, a housing 22, a lens 24 and a prism 26. The front of the laser diode 20 includes an aspherical cylindrical lens that co-operates with a parabolic reflecting surface 28 to produce a collimated beam of laser light. The prism 26 effectively serves to tap off a portion of the laser light such that this may be directed across the coin in a direction parallel to the major surface of the coin to detect the coin thickness if required. The light source illustrated in Figure 5 may be made as a waterproof sealed unit to increase the reliability and longevity.

Figure 6 shows the light source of Figure 5 in plan, back and cross sectional views.

Claims

1. Apparatus for identifying coins, said apparatus comprising : a coin path having a free fall portion, coins to be detected being in free fall whilst traversing said free fall portion; and an optical sensor operable to detect opposite edges of a coin traversing said free fall portion to obtain one or more dimensional characteristics of said coin that may be used to identify said coin.

2. Apparatus as claimed in claim 1, wherein said one or more dimensional characteristics include a diameter of said coin.

3. Apparatus as claimed in any one of claims 1 and 2, wherein said one or more dimensional characteristics include the presence on milling on both said opposite edges of said coin.

4. Apparatus as claimed in claim 3, wherein said wherein said one or more dimensional characteristics include a groove spacing value of said milling.

5. Apparatus as claimed in any one of claims 3 and 4, wherein said wherein said one or more dimensional characteristics include a groove depth value of said milling.

6. Apparatus as claimed in any one of the preceding claims, wherein said optical sensor comprises two linear array sensors illuminated by one or more light sources, said coin in said free fall portion acting to block light reaching at least some pixels of each linear array sensor such that said dimensional characteristic can be detected from a sum of blocked pixels for said two linear array sensors.

7. Apparatus as claimed in claim 6, wherein each of said linear array sensors is disposed with pixels arranged substantially horizontally such that said coin in said free fall portion has a path substantially perpendicular to said pixel arrangements.

8. Apparatus as claimed in any one of claims 6 and 7, wherein said linear array sensors are CMOS sensors.

9. Apparatus as claimed in any one of the preceding claims, wherein said coin path includes a stabiliser serving to guide said coin to a follow a predetermined path through said free fall portion.

10. Apparatus as claimed in claim 9, wherein said stabiliser comprises two flexible wings extending into said coin path and having a gap therebetween, said coin pushing said flexible wings aside to pass through said gap and enter said free fall portion.

11. Apparatus as claimed in any one of claims 9 and 10, wherein at least those portions of said stabiliser which contact said coin are formed of PTFE.

12. Apparatus as claimed in any one of the preceding claims, comprising an inductive sensor for detecting an inductive characteristic of said coin.

13. Apparatus as claimed in claim 6, wherein said inductive sensor is disposed between said two linear array sensors and is arranged to measure said inductive characteristic substantially at a centre point of said coin.

14. Apparatus as claimed in any one of the preceding claims, comprising a metal sensor in the form of capacitor plates to measure the capacitance of the coin.

15. Apparatus as claimed in claim 14, wherein said metal sensor is disposed between said two linear array sensors.

16. Apparatus as claimed in claim 1, wherein each of said optical sensor includes a source of collimated light including a light source, an aspherical cylindrical lens and a parabolic reflector.

17. Apparatus as claimed in claim 16, wherein said light source is a laser light source.

18. Apparatus as claimed in any one of claims 16 and 17, wherein each of said at least two optical sensors are formed as waterproof sealed units.

19. Apparatus as claimed in any one of the preceding claims, wherein said coin is a currency coin or a token coin.

20. A method of identifying coins, said method comprising the steps of : providing a coin path having a free fall portion, coins to be detected being in free fall whilst traversing said free fall portion; and detecting opposite edges of a coin traversing said free fall portion using an optical sensor to obtain one or more dimensional characteristics of said coin that may be used to identify said coin.

21. Apparatus for identifying a coin substantially as hereinbefore described with reference to the accompanying drawings.

22. A method of identifying a coin substantially as hereinbefore described with reference to the accompanying drawings.