DE69703103T2 - Device and method for checking coins - Google Patents

Description

The present invention relates to a device for testing coins and a method of recognizing coins.

Coin test systems or coin validators are used, for example, in vending machines and telephones to detect and evaluate different coins. Various electromechanical and electromagnetic coin validators are available and are used for different purposes, for example in vending machines, public and private telephones; etc. Such validators can be used in many types of vending machines or vending machines, for example in airports, railway stations, gaming machines, businesses, shops, hospitals, hotels or offshore or drilling platforms.

Such coin graders used in vending machines and telephones are generally very limited in terms of the number of different coin types that can be graded.

Published British Patent Application GB-A-2,212,313 shows a coin sorting device in which a beam of light is directed at an angle to the edge of a coin. If the coin is of the correct diameter, part of the beam of light passes in a straight line through a first detector and part of the beam of light is reflected (scattered) to a second detector which is not on the straight path. The system of GB-A-2,212,313 relies on some light being received by both detectors to confirm that the coin is just the right diameter to partially reflect the beam of light. If no light is received by either detector or all of the light is received by the straight line detector, the coin does not have the desired diameter. The system suggests a laser diode as a possible light source.

Published European patent application EP-A-0.629.979 shows a system that ensures that new coins fed in are of the correct size by using a light flux and a linear sensor arrangement.

Summary of the invention

According to a first aspect of the present invention there is provided a method of testing coins, in which a laser beam is directed at a side of a coin and a laser detector is used to obtain an indication of dimensional characteristics of the surface of the coin, characterized in that the laser detector detects where the laser beam is interrupted and where the laser beam is not interrupted by the coin.

The length of at least a portion of at least one elongated strip on the surface of the coin can be determined or detected.

The lengths of at least parts of a plurality of elongated stripes on the surface of the coins can be determined or detected.

The beam can scan the strips or at least the mentioned parts of them one after the other.

The beam may have a fan-like shape so as to impinge on the whole strip or on each of the strips or on a part of it simultaneously.

The laser detector can have a plurality of pixels arranged next to one another, each of which is individually capable of detecting laser radiation.

The beam is preferably stationary and the coin moves past the beam. The coin may rotate as it moves past the beam.

The coin can move along a guide as it moves past or through the beam.

The coin may be in free fall as it passes through the beam.

One end of the strip or each of the strips may be located on one edge of the coin and another end of the strip may be located at a predetermined location that is not on the edge of the coin.

A second laser beam can be directed at an edge or rim of the coin and detected to determine a characteristic of the rim and/or the thickness of the coin.

A characteristic dimensional property of the groove or channel and/or a rib on the edge of the coin can be determined or recorded.

The number of grooves or ridges at a predetermined distance on the edge of the coin can be counted.

The second laser beam can be branched off from the first-mentioned laser beam.

The second laser beam can be branched off from the first-mentioned laser beam by means of a prism which redirects a part of the first-mentioned laser beam. Preferably, at the point of interruption of the laser beam by the coin, the coin is aligned absolutely perpendicular to the laser beam.

At the point where the laser beam is interrupted by the coin or at the point where the coin and laser beam meet, the laser beam can essentially have the shape of a thin plane of laser radiation.

According to a second aspect of the present invention there is provided an apparatus for testing coins comprising:

a laser source designed and arranged to direct a laser beam onto a surface of a coin,

a laser detector and

a signal processor designed and arranged to receive from an output of the laser detector an indication of a dimensional property of the surface of the coin, characterized in that the laser detector is designed and arranged to detect where the laser is interrupted by the coin and where the laser is not interrupted by the coin.

Preferably, the device is designed to determine or detect the length of at least a portion of at least one elongated strip of the coin.

The device may be designed to determine or detect the lengths of at least parts of a plurality of elongated strips of the coin.

The beam may be designed to scan the strips or the mentioned parts thereof one after the other.

The beam may have a fan-like shape so as to impinge on the entire strip or on each strip or on a part of it simultaneously.

Preferably, the laser source and hence the beam is stationary and the device is designed to cause the coin to move past or through the beam.

The device may include a guide for the coin to move along as it moves through the beam.

The device may be designed so that the coin is in free fall while it moves along or through the beam.

In use, one end of the or each of the strips may be located on an edge of the coin and another end of the strip may be located at a predetermined position that is not on the edge of the coin.

The device may comprise means for directing a second laser beam at an edge of the coin, means for detecting whether the second beam is intercepted by the coin, and means for determining therefrom a characteristic property of the edge and/or the thickness of the coin.

The device may comprise means for branching the second laser beam from the first-mentioned laser beam.

The means for branching the second laser beam from the first-mentioned laser beam may comprise a prism which redirects a portion of the first-mentioned laser beam.

The laser detector can have many pixels arranged next to each other, each of which is individually capable of detecting laser radiation.

According to a third aspect of the invention there is provided a coin testing apparatus comprising:

a laser source designed and arranged to direct a laser beam onto a surface of a coin,

a laser detector designed and arranged to detect where the laser is interrupted or intercepted by the coin and where the laser is not interrupted or intercepted by the coin,

a coin guide arranged to allow the coin to travel along a specific path, the coin being able to interrupt or intercept a portion of a laser beam traveling between the laser source and the laser detector along this path, and

a signal processor designed and arranged to receive an output of the laser detector,

wherein the portion of the laser beam which is intercepted or interrupted provides at least a measure of a geometric dimension of the coin, the coin being recognizable by comparing this measure of the coin with corresponding dimensions of a number of known coins.

At least one measure may consist of a geometric dimension on the surface of the coin and another measure may consist of the thickness of the coin, in order to compare these surface and thickness measures with corresponding measures of a number of known coins.

A range of geometric dimensions may be repeatedly measured to provide an integrated area measurement of a surface area of a coin, the coin being identifiable by comparing the area measurement of the coin with corresponding area measurements of a number of known coins.

A dimensional property of a groove or a ridge on the edge of the coin can be determined or recorded.

The number of grooves and/or ridges at a predetermined distance on the edge of the coin can be counted.

The measure of the geometric measurement of the coin and the corresponding measures of the number of known coins may all refer to measurements of coins that are smaller than the diameter or, in the case of irregularly shaped coins, smaller than the maximum cross-section or diameter of any corresponding coin.

The laser beam that passes between the laser source and the laser detector can run along a circumstantial or winding non-direct path.

The laser beam can be guided along the winding, non-direct path through one or more mirrors or prisms.

The path may comprise a passage having a lower boundary along which the coin can pass through the device while being continuously supported at its peripheral edge by said lower boundary of the passage.

The laser source may be mounted to direct a laser beam from one side of a portion of the passage to the other, substantially perpendicular to the main plane of the coin in the passage so that it is interrupted by upper portions of the coin as it passes through that portion or section of the passage.

The laser detector can have a linear arrangement of many pixels arranged next to one another, each of which is individually capable of detecting laser radiation.

The array may extend substantially parallel to the main plane and perpendicular to the direction of travel of the coin along the portion of the passageway and may have a lower end spaced a first distance from the lower boundary, said first distance being less than the minimum diameter of the plurality of coins, and an upper end spaced a second distance from the lower boundary, said second distance being greater than the maximum diameter of the plurality of coins, the laser detector being operable to produce an output value in dependence on the number of pixels for which the laser beam is blocked during a plurality of successive scans by a coin traveling along said portion of the passageway, so that the output value can be compared with predetermined reference data records to determine which of those records correspond to that output value.

The coin can travel along the path in such a way that the coin is absolutely perpendicular to the laser beam at the point of interruption.

Preferably, the laser beam intercepted by the coin has substantially the shape of a thin plane of laser radiation at the point of interruption.

According to a fourth aspect of the invention there is provided a coin testing device comprising:

a coin guide defining a coin passage with a lower boundary along which a coin can pass through the device while being continuously supported at its peripheral edge by said lower boundary,

a laser source mounted to direct a laser beam from one side of a portion of said passage to the other, substantially perpendicular to the principal plane of the coin in the passage, so as to be intercepted by upper portions of the coin as it passes through that portion of the passage, and

a laser detector having on the other side of said portion of the passage a linear array of laser pickup locations, said array extending substantially parallel to said main plane and transversely with respect to the direction of travel of the coin along said portion of the passage, and having a lower end spaced a first distance from said lower boundary, said first distance being less than said minimum diameter of a number of coins with which the device is to be used and having an upper end spaced a second distance from the lower limit, the second distance being greater than the maximum diameter of the number of coins, the laser detection means being operable to produce an output dependent on the number of laser pickup locations from which the laser beam is blocked or intercepted in a plurality of successive scans by a coin passing along that portion of the passageway, so that the output can be compared with predetermined reference data records to determine which of those records correspond to the output.

The device may have more than one laser source and more than one laser detector.

According to a fifth aspect of the invention, there is provided a method of detecting a coin comprising the steps of:

i) performing a coin movement along a predetermined path so that the coin interrupts a portion of a laser beam extending between a laser source and the laser detector,

ii) measuring the portion of the laser beam which is interrupted or intercepted as a means of determining at least one measure of a geometric dimension of the coin,

iii) Comparing the size or dimension of the coin with the corresponding size of a number of known coins to identify the coin.

The at least one measurement may consist of a geometric dimension on the surface of the coin, the method further comprising the step of determining the thickness of the coin to compare these measurements with corresponding measurements of the number of known coins.

The method may further comprise the step of determining the measure of a number of geometric dimensions of the coin to provide an integrated area measurement of a surface area of the coin, the coin being recognizable by comparing the area measurement of the coin with corresponding area measurements of the number of known coins.

The method may further comprise the step of determining or detecting a characteristic dimensional property of a groove and/or a rib on the edge of the coin.

The method may further comprise the step of counting the number of grooves and/or ridges at a predetermined distance on the coin.

In this specification and the appended claims, the terms "laser source" and "laser detector" are intended to encompass any device or combination of devices that performs the function of providing a source of laser radiation or detecting the laser radiation, respectively. The laser source and the laser detector may each be a single component, a portion of a component, or an assembly of parts, provided that each performs the function of enabling the operation of the invention as claimed.

Further preferred features of the invention are set forth in the claims appended hereto, and the content of the claims is hereby incorporated into the description.

drawings

In order that the invention may be better understood, embodiments of the invention will be described by way of example only with reference to the accompanying drawings in which:

Fig. 1 shows a side sectional view of a first embodiment of a coin testing device,

Fig. 1A shows components of the first embodiment in their relative orientation to each other,

Fig. 1B shows, for illustrative purposes, a side sectional view of a housing used in the embodiment of Fig. 1, without the internal components,

Fig. 1C shows an external side view of the housing of Fig. 1B,

Fig. 1D shows a perspective view of the housing of Fig. 1B,

Fig. 2 shows a side sectional view of a second embodiment of a coin testing device,

Fig. 2A shows components of the coin testing device of the second embodiment of Fig. 2 in their relative arrangement to each other,

Fig. 2B is a perspective three-dimensional view of components of the second embodiment shown in Figs. 2 and 2A,

Fig. 2C shows another view of the second embodiment of Figs. 2, 2A and 2B, shown with a coin rolling from right to left through the diagram,

Fig. 2D illustrates the coin guide of Fig. 2A installed in a tilted orientation

Fig. 2E shows an arrangement for measuring the coin thickness,

Fig. 3 is a diagram using the letters X, Y and Z to mark the location of three linear arrays used in another embodiment,

Fig. 4 is an illustration of a third embodiment in which the coin interrupts the laser beam when it is in free fall. An arrow is used to mark the direction of fall of the coin,

Figures 5 and 6 are schematic diagrams of alternative embodiments which serve to illustrate that the invention can also incorporate laser sources and laser detectors that are not positioned perpendicular to the main plane of the coin,

Fig. 7 shows a laser unit used in the first embodiment of Fig. 1

Fig. 7A shows the use of a Powell lens to focus the laser beam,

Fig. 7B shows a plan view of the laser beam of Fig. 7A, illustrating that the laser beam formed by the Powell lens has the shape of a plane or line of laser radiation,

Fig. 8 shows various views of a sensor unit used in the embodiments of Figs. 1 and 2,

Fig. 9 shows an electrical block diagram of the internal parts of the sensor unit shown in Fig. 8,

Fig. 9A is a timing diagram of a linear array in parallel connection showing the pulses related to the sensor unit of Figs. 8 and 9,

Fig. 10 is a circuit diagram used in the first generation electronics used in the embodiment of Fig. 1,

Fig. 10A shows a block diagram of a clock signal generating circuit used in the embodiments of Figs. 1 and 2,

Fig. 10B shows a "Power on" circuit,

Fig. 11 is a circuit diagram of the laser power supply,

Fig. 11A shows the connections of a Y-Z sensor arrangement used in the device of Figs. 1 and 2,

Fig. 11B is a diagram explaining the pixel layout,

Fig. 11C shows three level converters for analog to digital conversion,

Fig. 12 shows a block circuit diagram of a counter circuit used in the embodiments of Figs. 1 and 2,

Fig. 12A shows two circuits of self-holding switches,

Fig. 12B shows a block diagram of two buffer memory interfaces,

Fig. 12C shows a block circuit diagram of a main control circuit used in the embodiments of Figs. 1 and 2,

Fig. 12D shows two static RAM memory circuits,

Fig. 12E shows a flash EEPROM memory circuit,

Fig. 12F shows an LCD driver, a relay and a phototransistor driver,

Fig. 12G shows a relay PIN driver and PIN photosensors,

Fig. 12H and 12I show printed circuit boards used in the circuits of the embodiments,

Fig. 13 is a graph showing on an X-Y axis the function of an algorithm used for the calculations performed in an embodiment of the invention,

Fig. 13A illustrates an embodiment in which the coin is identified by reference to characteristics of the grooves in the edge of the coin,

Fig. 14 is a block diagram illustrating the components of the embodiments of the invention in relation to the electrical components.

The drawings are for illustration purposes only and therefore not necessarily to scale.

For the sake of illustration, similar components in the embodiments are numbered with the same numbers. For example, the laser radiation sources in each embodiment are identified with the same reference number, but this does not imply that the embodiments are identical.

Description of the embodiments First embodiment

In Fig. 1, a first embodiment of the invention is shown in the form of a coin testing device 20. The device 20 has a housing 5.

A laser source in the form of a cylindrical laser unit 1 is slidably accommodated in a cylindrical cavity 51 in the housing 5.

This unit 1 comprises a conventional laser diode 11 and groups of lenses (both groups are indicated by the number 12). The laser diode 11 produces a laser beam 13 (shown in dotted lines in Fig. 1). The lens groups 12 are able to transform the laser beam 13 into a shape so that the beam is in a fan-like shape when it leaves the tip of the laser unit 1. The laser beam emanates from the laser diode 11 as a point source and is spread out in a fan-like manner by the lens groups 12 so that the beam can be used to impinge on larger sections of the coin simultaneously.

The shape of the laser beam 13 is one that spreads out in the form of a fan-shaped laser beam. In order to generate this laser beam spread out in a plane, two lines sets of lenses with different characteristics are used. A first group of lenses 12 acts to highly collimate the laser beam with a rectangular cross section. Another group of cylindrical lenses 12 causes the cross section of the laser beam to be stretched so that the cross section becomes an elongated rectangle almost a line. The laser beam 13 from the laser diode 11 passes through these lenses. The fan-shaped laser beam in Fig. 1 is focused using the lenses 12 in the laser unit 1 and by slidably adjusting the position of the laser unit 1 in the hole 51.

The coin testing device 20 further comprises a coin guide including a channel 61 having a lower limit or stop 62 and an upper passage 52 in which a coin 4 is shown. The coin is inserted into the passage 52 via a coin insertion opening 63 (best seen in Fig. 1D). The channel 61 guides the coin 4 along the passage. The coin passage 52 extends across the housing part 5. The coin 4 is continuously held at its outer edge by the lower limit 62 of the coin guide. The coin 4 moves through the device in a direction perpendicular to the plane of Fig. 1.

On the side of the channel 61 remote from the laser source 11, the housing 5 contains a laser detector in the form of a sensor array unit 3. The array unit 3 comprises many individual high-speed charge collectors and pixels arranged side by side (not shown separately). These charge collectors include pixels that are sensitive to laser radiation and are capable of detecting and measuring laser radiation energy levels. The pixels are arranged in a linear array, in a linear or grid-like orientation, to form a contiguous array of pixels. Each charge collector, in its uncharged state, is capable of being charged when the beam of a laser beam 13 is incident on the individual pixel. The pixels are sufficiently sensitive to detect photons, which are an elementary component of the laser beam. The sensor arrangement unit 3 also has connectors or plugs 19 which are intended to connect the sensor arrangement unit 3 to an electrical circuit which is described below.

The laser beam 13 generated by the laser diode 11 is directed at the sensor array unit 3. In the embodiment of Fig. 1, after the laser beam exits the laser diode 11, the laser beam 13 is aligned to form a fan-like planar beam shape. The term fan-like refers to the spreading of the laser beam as it exits the laser diode. The term planar beam refers to the formation of a thin line or linear area of laser beam radiation. The plane of this fan-like beam of radiation is generally aligned with the center of the linear array.

The laser beam 13 passes between the laser diode 11 and the linear array of sensors 3. The laser beam 13 is aligned axially along the bore 51 and across the passage 52. The axis of this laser beam 13 is substantially perpendicular to the main plane of the coin in the passage. The laser beam 13 is directed at a face of the coin 4 to be checked. The coin 4 covers a portion of this laser beam 13 that passes between the laser diode 11 and the sensor array unit 3. In the present embodiment, the beam is stationary and the coin moves past the laser beam. A circular coin rotates as it moves through the laser beam, while a non-circular or polygonal shaped coin would slide through the beam.

The sensor arrangement 3 is able to detect where the laser is blocked by the coin and where the laser is not blocked by the coin, since those pixels irradiated by the laser beam cause the charge collectors to be charged, while those pixels blocked by the coin do not cause the charge collectors to be charged. The information of the charged and uncharged collectors is used to obtain an indication of a characteristic of the area of the coin, as will be described below.

Referring to Figure 9, the pixels and charge collectors operate on a saturation basis by measuring the minimum and maximum absorbable quantum energy of the laser beam. When a pixel is excited to a level of about half its maximum saturation charge, the pixel's control logic is able to determine the exact amount of energy received by the pixel from the laser beam. The control logic then determines whether the charge collector is considered a "0" for an uncharged state or a "1" for a charged state.

In the present embodiment, the plane of the linear sensor array unit 3 extends substantially parallel to the main plane of the coin 4 in the passage 52 and transversely with respect to the direction of travel of the coin along that passage. The lower end of the array 3 is spaced from the lower boundary 22 by a first distance d in Fig. 1, the first distance d being less than the minimum diameter of the coins used with the device. The upper end of the array 3 is spaced from the lower boundary 62 by a second distance D, the second distance D being greater than the maximum diameter of a coin. The laser beam 13 is therefore interrupted by upper portions of the coin 4 as it moves along the passage.

Preferably, the upper regions of the coin 4 are allowed to interrupt the laser beam 13 in order to perform measurements of the upper region of the coin. Alternatively, measurements may be performed in other regions of the coin 4, such as side portions.

However, when the coin is in contact with the lower limit 62 of the coin guide, such contact makes it difficult to make an accurate measurement for those parts of the coin that are in contact with the lower limit 62.

Measurements of the coin do not need to be taken for the entire diameter or, in the case of irregular coins, for the maximum cross-section. By avoiding readings of the diameter or maximum cross-section, the problems associated with measuring the section where the coin contacts the rolling surface are minimised.

The sensor unit of the linear array 3 produces electrical output values at successive sampling times which depend on the number of pixels blocked by the coin and the number of pixels not blocked. This signal is preferably sampled many times as the coin moves past the linear array 3, as will be described in more detail below.

The sensor unit of the linear array 3 is connected to a signal processor which processes these outputs to identify the coin in question. The signal processor takes the form of a microcontroller 14, shown in Figures 12C and 14. The microcontroller 14 includes comparison means for determining whether and which of a plurality of predetermined reference data entries correspond to the processed outputs. The processed outputs from the linear array 3 are compared, for example, with data entries of a large number of known coins. The coin 4 is identified by matching the processed output obtained from the linear sensor with the corresponding data entry of the known coin.

The housing part 5 is made of a material having good absorption properties of scattered laser light, for example a black polycarbonate material. The external aspects of the housing 5 are illustrated in Figures 1C and 1D. Other constructions may be selected depending on the particular environments in which they are to be installed. Moreover, in other embodiments of the invention it is possible for various components of the coin testing device to be manufactured integrally as part of the device in which it is used, for example a vending machine or a telephone, rather than the coin testing device being installed in its own housing. In these embodiments the coin guides are provided as part of the component of the particular device. It is envisaged that the coin guides need not be a separate identifiable component. In such embodiments, any feature of the overall device that serves to guide the coin that intercepts the laser beam can be considered to fulfill the function of coin guidance.

The various structural components of the coin testing device may, in other embodiments, be molded in one piece. For example, mirrors and prisms may be formed from the same material as the housing and coin guide. An advantage of molding as a manufacturing process may be used to reduce the cost of the device.

Fig. 7 shows an alternative embodiment for the construction of the lens groups. The desired shape of the laser beam 13 is produced by the use of a collimator lens 75 and a line producing lens 72 through which the laser beam from the laser diode passes. The fan-shaped beam is focused using the second series of lenses 12 in the laser unit 1 and by adjusting the axial position of the laser unit in the aperture 51. By rotating a front element assembly 73, the beam is focused and collimated as shown in Fig. 7. A locking ring 74 is used to secure the final position. The lens assembly can be rotated using a key supplied with the laser diode module to produce the best line of incidence of the laser beam 13 on the linear array 3. The greater the working distance, the longer and thicker the line.

Second embodiment

A second embodiment of the invention is shown in Figures 2, 2A and 2B. This second embodiment is similar to the first embodiment except that the laser detector comprises two linear arrays 3Y, 32. (For the sake of illustrating concepts, X and Y refer to the orthogonal X and Y axis terminology used in the art.)

A laser beam 13 emanates from the laser diode 11 and is refracted by the lens 12a and further refracted by the lens 12b.

Focusing the laser beam into a line is achieved by using a "Powell" lens. Lines of laser radiation focused by Powell lenses have the special property of having a uniform intensity along the entire length of the line. The spreading effect of the laser beam is illustrated in Fig. 7. Fig. 7A shows the use of a Powell lens 12 for expanding the angle of the laser beam 13. Fig. 7B is a top view of the laser beam shown in Fig. 7A, illustrating that the laser beam formed by the Powell lens has the shape of a narrow plane of laser radiation.

Until the laser beam reaches the interception point with the coin 4, the laser beam 13 is directed along a path substantially perpendicular to the main plane of the coin 4. A portion of the laser beam is directed to an edge of the coin 4 and is reflected by the peripheral edge or the edge of the coin 4. Parts of the remainder of the laser beam hit the linear array 3Y. The linear array 3Y is therefore able to determine a characteristic of the edge and/or the thickness of the coin 4. Fig. 2C shows a side view of the coin 4 rolling past the linear arrays 3Y, 32.

At the same time, a portion of the laser beam 13 is redirected by a prism 12c. Mirrors can be used instead of the prisms. The prism 12c redirects the beam vertically, so that the beam is directed to hit the edge of the coin. Only a portion of the downward beam hits the other linear array 32. Thus, two linear arrays are used to measure different portions of the face and edge of the coin 4.

An advantage of the beam being absolutely or at least substantially perpendicular to the main plane of the coin 4 at the critical point of beam interruption by the coin is that the beam will subsequently impinge directly on the linear sensor without any further deflection. The measurement taken on the linear sensor will thus be an accurate measurement of the actual coin.

In contrast, in Fig. 4, if the laser beam detects the coin at an acute angle, the measurement taken on the linear sensor will be somewhat larger than the actual size dimension of the coin. However, the coin testing apparatus would still operate effectively provided that the data measurements of known coins are calculated taking this factor into account. It is thus advantageous to the invention in its broadest aspect but not absolutely necessary that the beam be absolutely perpendicular to the plane of the coin at the critical point of detection.

However, an advantage of aligning the coin perpendicularly with the laser beam at the point of detection is that the use of a right angle beam makes it possible to take into account the deviations resulting from the grooves in the edge of the coin. It can be appreciated that if the beam interrogates the edge of the coin at a substantially acute angle, the beam will be blind to the undulation of the grooves. The acutely angled beam will only encounter a smooth perimeter free of grooves or ridges.

In the second embodiment of Fig. 2, both the first laser beam directed at the face of the coin and the second laser beam directed at the edge of the coin are derived from the same beam emanating from the single laser diode 11. The second laser beam is diverted from the first laser beam by means of a prism which redirects a portion of the first laser beam. In other embodiments of the invention However, separate laser beams can be generated from separate laser sources. Multiple laser diodes can be used.

Preferably, the coin guide of the device is arranged such that in use the coin guide is tilted. This tilted orientation of the coin guide is shown in Fig. 2D. The degree of tilt of the coin guide minimises the risk of the coin wobbling as it moves along the coin guide. There would be a risk of wobbling if the coin was oriented on edge as it moved along the coin guide. The ability of the device to distinguish sizes on the order of a few micrometres means that any small misalignment of the coin in the coin guide will affect the accuracy of the device. One approach to ensuring a degree of stability is to stop the coin before it passes the linear array and then release the coin to allow it to pass the linear array.

Third embodiment - free fall embodiments

The invention may include embodiments in which coins do not have to be continuously supported by a coin guide. For example, the coin guide may be in contact with the coin only up to the point before the coin interrupts the laser beam. At the moment of interruption of the laser beam, the coin may be in free fall. Preferably, the coin traverses the laser beam before it begins to lose its original orientation in its fall through free space. During free fall, measurements may be made on all parts of the surface or edge of the coin. Compared to systems that do not use laser radiation, coin measurements using lasers can be made sufficiently quickly that it becomes possible to make measurements of a coin while the coin is in free fall.

Fig. 4 is an illustration of a third embodiment in which the coin interrupts the laser beam when the coin is in free fall. In this embodiment a long linear sensor 3 is used. The use of a long sensor array allows the entire area and diameter to be measured as the coin falls past the sensor array 3. The lens in this third embodiment is selected to provide a wide fan-shaped area. The large angle of the laser beam and the long linear sensor together enable measurements of the coin to be made over a longer distance of the coin's path. This is particularly useful since the free-falling coin will be moving faster than a coin rolling over a coin guide. The laser beam 13 strikes the top edge of the coin at an acute angle. A measurement is made with respect to the front face of the coin. As mentioned above, the acuteness of the angle means that the spreading of the beam must be taken into account during the measurement.

Alternative embodiments

The invention is not limited to the presence of laser source and laser detector aligned perpendicular to the main plane of the coin.

In the alternative embodiments shown in Figures 5 and 6, mirrors and/or prisms 12c are used to redirect the laser beam 13. In these alternative arrangements, the laser beam 13 is still able to traverse the plane of the coin in a perpendicular manner.

In certain embodiments, optical fibers may be used to transmit the laser radiation to the laser radiation detector. Optical fibers may be used to direct the laser radiation along paths that require complex arrangements of lenses and/or prisms. The optional use of mirrors, prisms and/or optical fibers to redirect the laser beam may result in compact arrangements of the coin testing device.

Laser

A laser radiation source, such as a laser diode, is particularly suitable for such a coin testing device because a laser is a coherent and highly directed radiation source. All other non-laser radiation and light are incoherent. The unique characteristics of laser radiation arise from a process known as stimulated emission of radiation, whereas normal light arises from spontaneous emission. Laser radiation arises from stimulated emission of a confined beam of photons and atoms in a single quantum state.

A laser is also particularly suitable due to the long lifetime of such sources. (Current typical values of laser sources are 10,000 to 80,000 hours, 1 to 9 years. - Other estimates of the lifetime of laser diodes suggest a lifetime of 500,000 hours.)

Devices of embodiments of the invention may use a range of laser diode systems designed for original equipment manufacturer (OEM) use, with output powers set in accordance with SD(EN)6082. When these are incorporated into the above-mentioned device, it may be necessary to provide additional safety features to ensure that the equipment fully complies with the standard. However, the invention in its broadest aspect is not strictly limited to the inclusion of such safety features.

The area of the laser beam output from the laser diode 11 is in a practical embodiment of the invention (height x width) 2.5 mm x 1 mm with an extended area upon reaching the linear arrangement 3 of 30.0 mm x 1.2 mm.

The laser unit is operated at a positive voltage and comes from an unregulated supply in the range between 5 and 6 V. However, it is preferable that a lower voltage is used since the generation of a lower amount of heat results in an extension of the expected life of the equipment. In the circumstances, a 4.5 V supply shown in Fig. 11, regulated within ±5%, is used to power the laser unit. The housing of the laser module is preferably insulated from the voltage supply.

A practical embodiment of the invention uses a laser diode 11 which generates laser radiation with a wavelength in the range 635 nm to 840 nm, depending on the normalized response of the sensor unit 3. The wavelength of the laser radiation is selected to maximize the response of the sensor unit 3, so that the performance of the device is increased. However, the invention is not limited to the use of a specific wavelength of laser radiation and a range of laser sources can be used, for example from 330 nm to 1500 nm, covering the near UV to near infrared spectral range.

A TTL turn-off function is available for laser modules that operate with a negative supply voltage. An input between +4 and +7 V applied to the TTL turn-off input will turn the laser off and an input of 0 V will turn it on. When not in use, this input can be left floating. The laser can be operated pulsed at a frequency of 10 Hz or more using this input. However, continuous excitation of the laser diode is preferable in the practical embodiment mentioned above, as this tends to give the diode a longer lifetime.

If the laser in the above-mentioned practical embodiment is operated at a voltage above the minimum supply voltage and/or at a temperature of more than 60ºC above the ambient temperature, an additional heat sink should be used. If the temperature of the laser diode housing were to exceed its maximum specification, premature or even catastrophic failure could occur. To assist in the dissipation of heat from the laser module, the laser unit 1 preferably has a cylindrical housing that holds the laser diode and the lenses for focusing the beam (Fig. 1). The housing is made of PMMA (poly-methyl-methacrylate), but can be made of other materials, such as aluminum.

Linear sensor arrangement

The laser detectors used in the exemplary embodiments are in the form of linear sensor array units 3. The sensor array unit 3 is provided in Fig. 8 by a linear sensor array manufactured in an integrated CMOS process with holding circuitry as shown in Figs. 8 and 9. Such a sensor comprises a linear array 81 with 256 x 1 pixel array sensors (each 63.5 µm x 55 µm with 8.5 µm spacing between pixels), each of which produces a signal dependent on the amount of laser radiation received by the relevant pixel. However, other embodiments of the invention may advantageously accommodate linear arrays having a much larger number of pixel sensors. A larger number of pixel sensors would, for example, enable a larger amount of information to be obtained during the coin measuring process. Increasing the amount of information would therefore increase the accuracy of the measurement, especially in those embodiments that require the integration or summation of measurements, as will be described later.

It goes without saying that the smaller and more densely packed the pixels are, the greater the accuracy of the coin detection results.

The array is formed by two parallel connected arrays of 128 pixels as shown in Fig. 9. Each of the 128 pixels is controlled by a 128 bit shift register which includes switch control logic, charge collectors and an output amplifier which regulates the data chain from the pixels.

The outputs of the individual pixels, determined for each sampling period by a pulse input SI, as described below, are transmitted from terminals 4 and 8 (AO1 and AO2) to the sensor unit 3 in the form of a digital pulse train. As can be seen in Fig. 9, the sensor array unit 3 has a clock input CLK, an external trigger pulse input SI1 and SI2, and outputs AO1 (pixels 1-128) and AO2 (pixels 129-256). The array connection can also be serial.

The array 81 in Fig. 8 of two hundred and fifty-six sensor elements provides two hundred and fifty-six discrete pixels. Laser radiation energy striking a pixel creates electron-hole pairs in the region beneath the pixel. The field created by the bias voltage on the pixel causes the electrons to collect in the element, as the holes travel into the substrate. The amount of charge collected in each element is directly proportional to the amount of incident laser radiation and the interrogation time.

The use of laser radiation is an important feature of the invention. Previous devices not using laser radiation will not achieve the full benefits of the present invention. The pixels measure 63.5 µm by 55 µm with 63.5 µm spacing from center to center. All pixels are separated by a spacing of 8.5 µm. Due to the use of laser radiation, the system is able to detect changes in the dimensions of the coin in increments of about ±1 pixel, i.e. about 63.5 µm. This is because laser radiation consists of a single wavelength and there is minimal scattering of the laser beam compared to the light scattering associated with optical light. This property of laser radiation enables extremely small differences in the dimensions of the coins to be identified. The wavelength of the laser radiation source used in the present embodiment is λ = 670 nm, although it is to be understood that the invention is not limited to any specific wavelength of laser radiation. As a result, differences between coins as small as 1 pixel, i.e. 63.5 µm or 0.0635 mm, can be identified by using the apparatus of the present invention.

Fortunately, in cases where the diameter of different currency coins differs by only 1 pixel, these coins differ significantly in the measurement of their thickness. For example, the US and Canadian 1 cent coins each have essentially the same diameter, but they also differ in thickness by about 160 µm or 0.16 mm. Therefore, although the diameter of the Canadian and US 1 cent coins differs by one pixel, these coins can be identified by differences in their thickness. Preferably, therefore, in addition to measurements of the surface of the coin, measurements of the thickness of the coin are also taken. However, testing of the coins may be based on the measurement of a dimension if a limited number of coins are to be accepted and within such a number of coins the differences between the coins are significant.

As shown in Fig. 9A, the operation of the 256 x 1 array sensor is characterized by two time intervals: an integration interval tint (the previously mentioned sampling interval) during which charge is generated by the bias voltage in the pixels, and an output interval tot during which a sequence of digital output signals for one sampling period is transmitted from the common outputs AO1 and AO2. The integration interval is determined by the interval tint between successive control pulses SI applied to terminal 2 (SI1) and terminal 10 (SI2) of unit 3. The required length of the integra The duration of the pulse interval depends on the amount of incident laser radiation and the desired output signal level.

The sensor in the embodiment consists of 256 pixels arranged to form a linear array. When laser radiation energy hits each pixel, a photocurrent is generated. This current is then integrated by an active integration circuit connected to the pixel.

During the integration period, a sampling capacitance is connected to the output of the integrator via an analog switch. The amount of charge collected at each pixel is directly proportional to the laser energy on that pixel and the integration time.

The output and reset of the integrators in Fig. 11A is controlled by a 256-bit shift register and reset logic. An output cycle is initiated by clocking a logic 1 on SI1 (pin 2) and on SI2 (pin 10). Another signal called hold is generated by the rising edge of SI1 and SI2 and transmitted simultaneously to sections 1 and 2. This causes all 256 sense capacitances to be disconnected from their respective integrator and starts an integrator reset period. When the SI pulse is clocked through the shift register, the charge stored on the sense capacitances is sequentially connected to a charge-coupled output amplifier which produces a voltage on the analog output AO. The integrator reset period ends 18 clock cycles after the SI pulse is clocked in. Then the next integration period starts. With the rising edge of the 128th clock, the SI1 pulse is clocked out to the SO1 pin 13 (section 1). The rising edge of the 129th clock cycle ends the SO1 pulse and returns the analog output AO1 of section 1 to the high impedance state. Similarly, SO2 is clocked out with the 256th clock pulse. A 257th clock pulse is required to end the SO2 pulse and return AO2 to the high impedance state.

AO is driven by a source follower, which requires an external dropout resistor. When the output is not in output phase, it is in a high impedance state. The output is normally 0V for no power input and 2V for a nominally full-scale output.

In further embodiments, the laser detector may comprise a number of linear sensor array units arranged in a matrix orientation. The advantage of using such a matrix sensor is that the laser detector is provided with a larger surface area.

First generation electronics

The clock signal CLK and the control signal 51 can be produced by any suitable timing circuit, for example that shown in Fig. 10, in which a 555 timer circuit 101 generates the clock signal CLK, while an 8-bit counter 74LS590 and a Schmitt trigger 74LS221, referred to as circuits 102, generate the control signal.

The sensor array unit 3 transmits the digital output pulse train to, for example, a counter circuit as shown in Fig. 10, which comprises a series of three 4-bit 74LS160 counters connected together to form a single 12-bit counter 92. This counter 92 receives a signal from an AND gate 91, which gate connects a clock signal CLK and the digital serial output signal of the sensor unit 3. As each charge collector signal, which may have the values "1" or "0", is produced by the pixels in the linear array unit 3, it is clocked into the counter input by the clock signal CLK. A charge collector signal equal to "1" increments the counter.

When all 256 bits relating to the 256 receiving pixels in the sensor array unit 3 have been transmitted from the sensor unit 3, a signal SO2 from the sensor array unit 3 triggers a set of latching switches 93, 74LS373 so that the result of the counting of the 256 pixels is held on the outputs thereof. These outputs are then decoded by 7-segment display drivers 74LS48 shown as digit 94 in the drawings to produce a three-digit number on 7-segment LED displays 95. This number corresponds to the specific area of the coin in question being examined.

The outputs from the sensor array unit 3 are also provided as inputs to a main control comparison circuit (Fig. 14) which compares the outputs with predetermined reference values stored in a data library 16 corresponding to the number of coins the device is to identify. The data library is in the form of a flash RAM. The comparison circuit 15, in the form of an EEPROM, is shown in Fig. 14. The comparison circuit provides an output signal SC which identifies the coin being tested.

Second generation electronics

The following is a description of the second generation of electronics used in the embodiments of the invention obtained through further research and development.

Y-sensor arrangement:

As shown in Fig. 2D, this sensor indirectly measures the area, radius and diameter of the coin 4. It can detect the presence of grooves and ridges on the side of the coin and count them.

The sensor array consists of two narrow arrays YH and YL. Each consists of 128 pixels. The design of these pixels is explained in a schematic form in Fig. 11B. During each scan, the electronics will generate a number Y, which is defined as follows: if (number of exposed pixels) = 0, then let Y = 0, otherwise let Y = (number of exposed pixels) - 1.

The sensor, operating at a clock frequency of 2 MHz, can output all 128 pixels of each array in 64.5 ns. The maximum possible sampling rate is therefore 15,503 samples per second, or 4 million digits of "0" or "1" per second. If a coin passes through an array at 1 m per second, each mm of the coin will be sampled approximately 16 times. This is sufficient to determine the minimum value of Y as the coin passes through the array. The minimum value of Y corresponds to the diameter of the coin. During each sampling, the SI pulse generated by U204 will initiate the shiftout cycle at each pixel in YL and YH. U301 will begin counting the number of "high" pixels in either YL or YH. Pixels exposed to the laser L will give "high" outputs, while pixels covered by a coin or not exposed to the laser will give "low" outputs. Once the first "low" pixel is hit, U301 stops counting.

If the coin covers the YH array behind it, the first pixel of YH is "low". The value of Y will be less than 128, i.e. Y7 = 0. U301 will count the "high" pixels only in the YL array.

If the coin does not cover the YH array behind it, the first pixel of YH is "high". All pixels of YL will be exposed and Y will therefore be greater than 127, i.e. Y7 = 1.

U301 will count the "high" pixels only in the YH array. At the end of the shiftout cycle, the count values of U301 and Y7 are held at U205 as Y value and subsequently read by the PC or microcontroller.

The first SI pulse to the Y sensor array is generated by the two power-on reset pulses PUR1 and PUR2 to initiate the first shiftout cycle. At the end of the shiftout cycle, the sensor array generates an SO pulse that is used to recover the SI pulse. In this way, the sensor samples data and shifts it through indefinitely at its maximum rate.

Z-sensor array

This sensor array directly measures the thickness of the coin. Only the first half (ZL) of the array is used.

In Fig. 2E, a window opening B allows a certain number of pixels of the ZL array to be exposed to the laser L'. When a coin passes through the window, the number of pixels covered by the coin is directly proportional to the thickness of the coin. Knowing the center-to-center distance between the pixels, the actual thickness on the coin can be calculated.

The Z sensor array works in parallel with the Y sensor array and uses the same 2 MHz clock and SI pulse.

In contrast to U301, U302 only counts the number of "high" pixels in the ZL array. At the end of the shiftout cycle, the count value of U302 is held in U206 as a Z value and subsequently read out by the microcontroller U101.

In Fig. 10A, a clock distributor U101 generates a frequency of 4 MHz. The clock distributor uses a 74LS74D type flip-flop U102A to halve the frequency to 2 MHz. The flip-flop is used in conjunction with Schmitt triggers to provide the timing for the microelectronics of the circuit used in the device.

In Fig. 10B, a circuit is shown that sets the logic from a "power off" state to a "power on" state. The setting logic circuit includes two 74ALS74, a switch and a number of Schmitt triggers.

Fig. 11 shows a laser power supply equipped with a current driver. The current driver is used to protect against variations in the drive current that would lead to a subsequent failure of the diode.

In Fig. 11A, analog signals are transmitted from the output terminals of the linear array to the level converter 17 as shown in Fig. 11C.

In Figs. 11C and 14, the level converter 17 converts the analog signals into a digital form. The digital signals are sent to the counter in Fig. 12 U204.(PAL 22V10). The counter counts the pixels that are in an excited state and those that are not in an excited state. The digital count of the pixels is then processed by the two latching switches U205, U206 (74ALS374) shown in Fig. 12A. The digital count The signal is sent individually to two separate buffers which operate in conjunction with each other, as shown in Fig. 12B. The buffers (U301, U302) form an interface between the controller and the linear arrays YZ.

In Fig. 12C, an Intel 196NU controller is used to read the data obtained from the buffer memory. The controller controls the algorithm and instructions stored in the static RAM and EEPROM during processing where the coin passes the linear array. During this process, the data obtained from the linear arrays is compared with the data information stored in the flash memory.

Following digitization of the flow data information obtained from the linear array, the digitized information is stored in two static RAM memories shown in Fig. 12D until the microcontroller is able to accept the data for analysis.

In Fig. 12E, an EEPROM flash memory is used to store instructions for the controller. These instructions include calibration data concerning the calibration of the device, data from known coins, and also include values of constants used in the mathematical algorithms.

A circuit for an intelligent LCD display driver U401 is shown in Figs. 12F and 14 (as number 18). The display driver is an A25510. In Fig. 12F, the driver also drives relays that are used to open and close two branch elements (shown in Fig. 12G). Two photosensors, also controlled by the driver, are used to detect the entry and exit of the coin into the passage 52.

Figures 12H and 12I show examples of printed circuit boards that can be used in the circuits of the embodiments.

Coin identification

When the coin 4 blocks part of the laser beam 13 from falling on the linear sensor array 3, the linear array 3 detects where the laser is interrupted by the coin and where the laser is not interrupted by the coin. This information is used to obtain an indication of a feature of the surface of the coin.

In simple embodiments of the invention, the length of at least a part of at least one elongated strip on the surface of the coin is determined or detected. This elongated For example, the stripe may be the diameter of a round coin or the maximum cross-section of a non-round coin, or it may be a portion of these measurements. Obtaining this information enables the coin to be identified by comparing this information with corresponding data from known coins. The present invention uses lasers to obtain this information and is therefore faster and is able to distinguish a larger number of coins compared to previous devices and methods.

In further embodiments of the invention, the lengths of at least parts of a plurality of elongated stripes on the surface of the coin are determined or detected.

The stripe or stripes start at an edge of the coin and extend to a predetermined point on the coin. For example, in Fig. 13, the area of the coin being scanned includes a number of stripes of width s. One end 70 of each stripe is located at an edge of the coin and another end 71 of each stripe extends to the diameter of the coin. However, the stripe or stripes may extend from the edge of the coin to any predetermined location that is not an edge of the coin, but which is not necessarily the diameter.

The laser beam interrogates the stripes or parts of the stripes, preferably one at a time. In the embodiment shown in Figure 13, a number of interrogation lines, each 63.5 µm wide (that is the width of the individual pixels in the linear array sensor 3) are used to make a series of measurements corresponding to the interrogated portions of the coin. The process can therefore be combined with a process of integrating segments of area measurements which are summed to give an indication of a property of the coin. Unusually shaped coins, such as the British 50p coin which is polygonal, are easily identified by measuring surface areas.

Such a system may operate at a rate between 10 Hz and 500 kHz, with a typical clock signal being 500 kHz. Improved systems using newer components may operate between 5 kHz and 2000 kHz, with a preferable clock signal of 2 MHz. A practical embodiment as mentioned above may produce between 39 and 15,000 measurements per second as the coin rolls past the linear array 3. These results are then summed in a known manner to produce a measure of the total area sampled by the system. It can be imagined that future developments in OEM hardware may lead to components allowing a higher number of measurements per second. These improvements in the speed of the components would nonetheless be within the scope of the prior underlying invention and it is anticipated that future advances in electronics will allow the invention to operate more efficiently.

In the iteration sequence used in the present embodiment, each query line has an area:

A = yδθ,

where y = the height of the strip

and δθ = the width of the sensor element.

It follows:

the total area of the queried lines = yδθ + y₁δθ + y₂δθ + y₃δθ + y₃δθ ...

The above functional formula is shown in a graph shown in Fig. 13. In Fig. 13, the height of each stripe is referred to as the Y value. Once the Y values are obtained by scanning the coin, various dimensions of the coin can be calculated by a variety of mathematical algorithms. One such algorithm is known as the trapezoid rule or Simpson's rule by applying the mean ordinate measure. Details of this algorithm are given only as an example and the invention is not limited to any specific mathematical algorithm.

Consider a half rotation of a coin with a periodic function of period π. The coin is theoretically divided into n stripes, each of equal width. The width s of each stripe is equal to π/n. The ordinates are denoted by y0, y1, y2, ... yn-1, yn as shown in Fig. 13.

A ∼ 1/2(y0 + y1)s + 1/2(y1 + y2)s + ... + 1/2(yn-2 + yn-1)s + 1/2(yn-1 + yn)s

∼ 1/2s{(y 0 + y 1 ) + (y 1 + y 2 ) + ... + (yn-2 + yn-1) + (yn-1 + yn)}

∼ s{1/2(y0 + yn) + y1 + y&sub2; + ... + yn-1}

Now, since f(x) = f(x + π), yn = y&sub0;

A = f(x)dx ...

f(x)dx ∼s{y�0; + y�1; + y₂; + ... + yn-1} where n = the number of strips of equal width

s = the width of each strip.

Note that the series inside the brackets ends at yn-1. The expression yn is considered to be the first ordinate of the next cycle.

The values of y₀, y₁, y₂, .... are available as given array values at regular intervals. If the function values are not given at regular intervals, a graph of Y versus X can be plotted and a new set of values of y at regular intervals of x etc. read out, i.e.

When the coin is interrogated at a very high rate, the need for compensation circuitry to compensate for differences in the speed or acceleration of the coin during the test is minimized.

In the present embodiment, therefore, the coin testing device is not only capable of measuring geometric distances such as radius, diameter and thickness. The high rate of interrogation, due in part to the fast response time of the laser beam, allows the coin testing device to iteratively measure a range of geometric dimensions. Each of these measurements is iteratively integrated to provide an area measurement of a surface region of the coin. The coin is recognized by comparing this area measurement to corresponding area measurements of other known coins.

The use of an iterative sequence of integration to obtain surface areas of coins is a far more accurate means of coin identification since it avoids the problem caused by variations in diameters and radii due to edge grooves of the coins. In those embodiments of the invention which measure geometric dimensions of coins, e.g. diameter, local variations due to grooves can affect the overall diameter measurement depending on whether the measurement has been made at a location where a groove exists or not. In contrast, those embodiments which rely on comparisons of surface areas as a basis for coin identification are less affected by local differences resulting from the existence of grooves. The variations due to grooves are taken into account in the measurements of larger areas of the coin surface.

The use of a laser beam system coupled to a laser detector having a multitude of tiny laser detecting pixels means that extremely small dimensions can be measured. As a result, measurements will differ from each other depending on whether the measurement was taken near a groove or away from a groove. These differences in measurements mean that relying on just a single diameter or radius measurement introduces uncertainty into the identification of coins if it is not certain whether the measurement was taken near a groove or away from a groove. When integration of a range of measurements is performed to provide a surface area measurement, comparisons between coins are made by comparing integrated areas of surface areas. The local variations in dimensions around the groove do not cause such significant variation in the overall surface of the integrated region.

With a speed control, the sum of the scanned images can reflect the actual size of the coin being measured. This speed control can be achieved by using a slot that stops the coin before free fall or rotation occurs.

Furthermore, the use of area measurements as a basis for identifying coins is particularly advantageous when measuring coins that are not round, such as polygonal shaped coins. For such non-round coins, transverse measurements would result in vastly different values depending on which part of the coins the measurements are taken on. However, surface area measurements of areas on such coins provide area measurements that can be consistently used as a basis for comparing these coins with other known coins.

Coin identification by counting grooves

Coins are usually provided with grooves along the peripheral edge and in some cases on edges of internal holes found in coins of some currencies. These grooves lead to ridges on the edge of the coin.

In embodiments where a plurality of stripes of a coin are read, the resolution of the sensor array unit 3 is such that the device is able to identify grooves that have been altered into the edge of the coin, such as in Fig. 13A. The identification of grooves may be used in conjunction with the identification of other geometric features as already described, or may be used as the sole means of coin identification. The detection of grooves enables the device to distinguish between different coins without the need for any further comparisons, e.g. of weight or diameter or the induction method used. For example, the cross-sectional area of a typical groove is generally in the range of 0.01 mm² to 0.04 mm², which is approximately three to eleven times the size of each detection pixel. The area of individual grooves can thus be clearly resolved by such an array sensor 3.

Even in the rare case where a pair of coins have identical diameters, thicknesses and/or surfaces, it is unlikely that these otherwise identical coins also have the same groove sizes. Identifying the groove characteristics of a groove is therefore a very accurate means of identifying a large number of coins, even those coins that have very similar geometric dimensions.

It is also possible to count the number of grooves occurring at a predetermined distance x on the edge of a coin, as illustrated in Fig. 13A. An advantage of identifying coins by counting the number of grooves at a predetermined distance is that the apparatus and method are less affected by size differences in coins resulting from wear and/or damage. Even if the physical dimensions of a coin are slightly changed due to wear, the number of grooves within a predetermined distance will remain constant. Furthermore, if the damage to a coin is localized to a small portion, the coin can still be identified provided that the apparatus reads an undamaged edge of the coin.

In further embodiments it is possible to generate a digitally defined image of the profile of the coin in question by analyzing the complete set of outputs from the interrogation operation. It is then possible to compare this measured image with a number of previously stored digital images to identify the coin in question. Processing means are provided to compensate for areas of damaged ridges on the coin. Such compensation may be achieved, for example, by analyzing the regular shape of the undamaged ridges. The device may be set to reject all coins that deviate from the stored images by more than a predetermined percentage. Such variations may occur, for example, due to the effect of wear on the coin.

In another embodiment, the laser radiation detector may comprise a linear sensor array consisting of eight sections of 128 pixels forming an array of 1024 x 1 pixels. It will be appreciated that wide planes of linear sensor arrays may be used. However, such variations of the embodiments of the invention will depend on technological developments in the construction of linear arrays.

Embodiments of the invention may be used in a wide variety of coin or token operated devices such as vending machines, telephones, locks, gaming machines and automated money changing machines. It will be appreciated that embodiments may be used in a money receiving apparatus so that the value of the coins may be credited to a credit card or other account.

Such coin testing devices can be constructed to detect a large number of metallic coins from currencies all over the world. Non-metallic coins can also be tested, since the invention does not rely on magnetic induction methods. The device can also be used to detect non-currency tokens.

Coins of the world's currencies are struck extremely finely and, most importantly, with reproducible tolerance. Some currencies may differ only to the order of a few micrometers. A particular coin can thus be identified by obtaining a measurement of a geometric dimension and/or region of the coin measured at a level of a few micrometers and then comparing the measurement(s) with data records of measurements of known coins. This level of precision means that the present invention is able to distinguish sets of coins which could not previously be easily distinguished using previous devices and methods. This also means that a device according to the invention is able to be used for a larger number of coins. Previous coin testing devices which do not seek to discriminate such small tolerances as, for example, on the order of micrometers, would all be useful only for a limited set of currencies, for example the coins of a single country, where the dimensions would vary substantially from coin to coin. These previous devices are less likely to be used effectively for a large set of coins where different coins may vary in dimension by only a few micrometers. For example, a device of the present invention has been able to successfully discriminate a set of over a hundred different coins in experiments and the invention is capable of discriminating much larger sets of different coins.

The embodiments have been given by way of example only and modifications are possible within the scope of the appended claims.

Claims (64)

1. A method of testing coins, in which a laser beam (13) is directed at a side of a coin (4) and a laser detector (3) is used to obtain an indication of characteristic dimensional properties of the surface of the coin, characterized in that the laser detector (3) detects where the laser beam (13) is intercepted or interrupted by the coin (4) and where the laser beam (13) is not interrupted by the coin (4). 2. Method according to claim 1, wherein the length of at least a portion of at least one elongated strip (71) on the surface of the coin is determined or detected. 3. A method according to claim 1, wherein the lengths of at least parts of a plurality of elongated strips (71) on the surface of the coin are determined or detected. 4. A method according to claim 3, wherein the beam scans the strips (71) or at least the mentioned parts thereof one after the other. 5. A method according to any one of claims 2 to 4, wherein the beam (13) has a fan-like shape so as to impinge on the whole strip or on each of the strips or on a part thereof simultaneously. 6. Method according to one of the preceding claims, wherein the laser detector (3) has a multiplicity of pixels arranged next to one another, each of which is individually capable of detecting laser radiation. 7. Method according to one of claims 1 to 6, wherein the beam (13) is stationary and the coin (4) moves past the beam. 8. A method according to claim 7, wherein the coin (4) rotates as it moves past the beam. 9. A method according to claim 7 or 8, wherein the coin (4) moves along a guide (61) while moving past or through the beam. 10. A method according to claim 7, wherein the coin (4) is in free fall as it passes towards and through the beam (13). 11. Method according to one of claims 2 to 5 or according to one of claims 6 to 10, as far as they are dependent on one of claims 2 to 5, wherein one end of the strip or each of the strips (7) is located at an edge of the coin (4) and another end of the strip is located at a predetermined location which is not located at the edge of the coin (4). 12. Method according to claim 3 or according to one of claims 4 to 11, insofar as they are dependent on claim 3, wherein a characteristic dimensional property (x) of a groove or channel and/or a rib on the edge of the coin (4) is determined or detected. 13. Method according to claim 3 or according to any one of claims 4 to 12, as far as they are dependent on claim 3, wherein the number of grooves or ribs at a predetermined distance on the edge of the coin (4) are counted. 14. Method according to one of claims 1 to 13, wherein a second laser beam is directed onto an edge of the coin (4) and detected in order to determine a characteristic property of the edge and/or the thickness (Z) of the coin (4). 15. The method of claim 14, wherein the second laser beam is derived from the first-mentioned laser beam (13). 16. A method according to claim 15, wherein the second laser beam is derived from the first-mentioned laser beam by means of a prism (12c) which redirects a part of the first-mentioned laser beam (13). 17. A method according to any preceding claim, wherein at the point of interruption of the laser beam by the coin, the coin is aligned absolutely perpendicular to the laser beam. 18. Method according to one of the preceding claims, wherein at the point of interruption of the laser beam by the coin or at the point of convergence of the coin and the laser beam, the laser beam has substantially the shape of a thin plane of laser radiation. 19. Device for testing coins, comprising: a laser source (11) designed and arranged to direct a laser beam (13) onto a surface of a coin (4), a laser detector (3) and a signal processor (14) designed and arranged to receive from an output of the laser detector (3) the indication of a dimensional property of the surface of the coin (4), characterized in that the laser detector (3) is designed and arranged to detect where the laser is interrupted or intercepted by the coin (4) and where the laser is not interrupted or intercepted by the coin (4). 20. Device according to claim 19, which is designed to determine or detect the length of at least a part of at least one elongated strip (71) of the coin (4). 21. Device according to claim 20, which is designed to determine or detect the lengths of at least parts of a plurality of elongated strips (71) of the coin (4). 22. Device according to claim 21, wherein the beam (13) is designed to scan the strips or the mentioned parts thereof one after the other. 23. Device according to one of claims 20 to 22, wherein the beam (13) has a fan-like shape so as to impinge on the entire strip (71) or on each strip or on a part thereof simultaneously. 24. Device according to one of claims 19 to 23, wherein the laser source (11) and thus the beam (13) are stationary and the device is designed to cause the coin (4) to move past or through the beam. 25. Apparatus according to claim 24, including a guide (61) for the coin to move along as it moves through the beam (13). 26. Device according to claim 24, which is designed so that the coin (4) is in free fall while it moves along or through the beam (13). 27. Apparatus according to any one of claims 20 to 23 or any one of claims 24 to 26 when dependent on any one of claims 20 to 23, wherein in use one end of the or each of the strips (71) is located at an edge of the coin (4) and another end of the strip (71) is located at a predetermined position not located at the edge of the coin (4). 28. Device according to claim 21 or according to one of claims 22 to 27, insofar as they are dependent on claim 21, wherein a characteristic dimensional property (X) of a groove and/or a rib on the edge of the coin (4) is determined or detected. 29. Device according to claim 21 or any of claims 22 to 28 as dependent on claim 21, wherein the number of grooves and/or ribs is counted at a predetermined distance on the edge of the coin (4). 30. Device according to one of claims 19 to 29, which has means for directing (12c) a second laser beam onto an edge of the coin (4), with means for detecting whether the second beam is intercepted by the coin, and with means for determining therefrom a characteristic property of the edge and/or the thickness (Z) of the coin (4). 31. Apparatus according to claim 30, comprising means for deriving the second laser beam from the first-mentioned laser beam (13). 32. Apparatus according to claim 31, wherein the means for diverting the second laser beam from the first-mentioned laser beam comprises a prism (12c) which diverts a portion of the first-mentioned laser beam. 33. Device according to one of claims 19 to 32, wherein the laser detector has many pixels arranged next to one another (3), each of which is individually capable of detecting laser radiation. 34. Device according to one of claims 19 to 33, wherein at the point of interruption of the laser beam by the coin (4), the coin is aligned absolutely perpendicular to the laser beam. 35. Apparatus according to any one of claims 19 to 34, wherein at the point of interception of the laser beam by the coin, the laser beam is substantially in the form of a thin plane of laser radiation. 36. Device according to claim 19, comprising: a coin guide (61) arranged to allow the coin (4) to travel along a specific path, the coin (4) being able to interrupt or intercept a portion of a laser beam (13) passing between the laser source (11) and the laser detector (3) along this path, and wherein the portion of the laser beam (13) which is intercepted or interrupted provides at least a measure of a geometric dimension (Y, Z) of the coin (4), wherein the coin (4) is recognizable by comparing this measure of the coin (4) with corresponding measures of a number of known coins. 37. A coin testing device according to claim 36, wherein at least one measurement consists of a geometric dimension (Y) on the surface of the coin (4) and another measurement consists of the thickness (Z) of the coin (4) to compare these surface and thickness dimensions with corresponding dimensions of a number of known coins. 38. A coin testing device according to claim 36 or 37, wherein a range of geometric dimensions are repeatedly measured to provide an integrated area measurement of a surface area of a coin, the coin being recognizable by comparing the area measurement of the coin with corresponding area measurements of the number of known coins. 39. Coin testing device according to claim 38, wherein a dimensional property (X) of a groove and/or a rib on the edge of the coin (4) is determined or detected. 40. A coin testing device according to any one of claims 38 or 39, wherein the number of grooves and/or ridges on the edge of the coin is counted at a predetermined distance. 41. A coin testing device according to any one of claims 36 to 40, wherein the measure of the geometric dimension of the coin and the corresponding measures of the number of known coins all refer to measurements of coins which are smaller than the diameter or, in the case of irregularly shaped coins, the maximum cross-section or diameter of each respective coin. 42. Coin testing device according to one of claims 36 to 41, wherein the laser beam which passes between the laser source (11) and the laser detector (3) runs along an angled or curved, non-direct path therebetween. 43. Coin testing device according to claim 42, wherein the laser beam (13) is guided along the curving, non-direct path through one or more mirrors or prisms (12c). 44. A coin testing device according to any one of claims 36 to 43, wherein the path comprises a passageway having a lower boundary (62) along which the coin (4) can pass through the device while being continuously supported at its peripheral edge by said lower boundary of the passageway. 45. A coin testing device according to claim 44, wherein the laser source (11) is mounted to direct a laser beam (13) from one side of a portion of the passage to the other, substantially perpendicular to the main plane of the coin in the passage, so that it is interrupted by upper portions of the coin as it passes through that portion of the passage. 46. Coin testing device according to one of claims 36 to 45, wherein the laser detector (3) has a linear field of many pixels arranged next to one another, each of which is individually capable of detecting laser radiation. 47. Coin testing apparatus according to claim 46 when dependent on claim 45, wherein the array extends substantially parallel to the main plane and perpendicular or transverse to the direction of travel of the coin (4) along the portion of the passageway and has a lower end spaced a first distance from the lower limit (62), this first distance being less than the minimum diameter of the number of coins, and an upper end spaced a second distance from the lower limit, this second distance being greater than the maximum diameter of the number of coins, the laser detector (3) being operable to produce an output value dependent on the number of pixels for which the laser beam is interrupted or blocked, during a plurality of successive scans by a coin traveling along this portion of the passageway, so that the output value can be compared with predetermined Reference data records to determine which of these records correspond to this baseline value. 48. A coin testing device according to any one of claims 46 or 47, wherein each of the pixels is part of a charge collector or charge detector. 49. A coin testing device according to any one of claims 36 to 48, wherein the coin (4) travels along the path such that the coin is aligned absolutely perpendicular to the laser beam (13) at the point of interruption. 50. Coin testing device according to one of claims 36 to 49, wherein the laser beam (13) intercepted by the coin (4) has substantially the shape of a thin plane of laser radiation at the point of interruption. 51. Device according to claim 19, comprising: a coin guide (61) defining a coin passage with a lower limit along which a coin (4) can pass through the device while being continuously supported at its peripheral edge by said lower limit, and the laser source (11) is mounted to direct a laser beam (13) from one side of a portion of said passage to the other, substantially perpendicular to the main plane of the coin (4) in the passage, so as to be intercepted by upper portions of the coin as it passes through said portion of the passage, and wherein the laser detector (3) on the other side of said portion of the passage comprises a linear array of laser pick-up locations, the array extending substantially parallel to the main plane and transversely with respect to the direction of travel of the coin along said portion of the passage, and having a lower end spaced a first distance from the lower limit, said first distance being less than the minimum diameter of a number of coins with which the device is to be used, and an upper end spaced a second distance from the lower limit, said second distance being greater than the maximum diameter of the number of coins, the laser detection means being operable to produce an output dependent on the number of laser pick-up locations from which the laser beam is blocked during a plurality of successive scans by a coin travelling along said portion of the passage, so that the output can be compared with predetermined reference data records, to determine which of these records correspond to the output value. 52. A coin testing device according to any one of claims 36 to 51, wherein the coin testing device is designed to be operated with a coin that is a token that does not represent currency. 53. A coin testing device according to any one of claims 36 to 52, wherein the device comprises more than one laser source and more than one laser detector. 54. Use of a coin testing device as claimed in any one of claims 36 to 53 in a device operable with coins or tokens (tokens). 55. Device operable with coins or tokens, comprising a coin testing device according to one of claims 36 to 53. 56. The method of claim 1, comprising: i) allowing the coin (4) to travel along a predetermined path so that the coin interrupts part of a laser beam (13) extending between a laser source (11) and the laser detector (3), ii) measuring the portion of the laser beam which is interrupted or intercepted as a means of determining at least one measure of a geometric dimension of the coin (4), iii) comparing the size or dimensions of the coin (4) with the corresponding size of a number of known coins in order to recognise the coin (4). 57. A method according to claim 56, wherein the at least one measurement consists of a geometric dimension (Y) on the surface of the coin (4), the method further comprising the step of determining the thickness measurement (Z) of the coin (4) in order to compare these measurements with corresponding measurements of the number of known coins. 58. A method according to claim 56 or 57, the method further comprising the step of determining the measure of a number of geometric dimensions of the coin (4) to provide an integrated area measurement of a surface area of the coin (4), wherein the coin (4) is recognizable by comparing the area measurement of the coin (4) with corresponding area measurements of Athe number of known coins. 59. The method of claim 58, further comprising the step of determining or detecting a characteristic dimensional property (X) of a groove and/or a rib on the edge of the coin. 60. A method according to any one of claims 58 or 59, further comprising the step of counting the number of grooves and/or ridges at a predetermined distance on the coin. 61. Method according to one of claims 56 to 60, wherein the laser detector (3) has at least one linear pixel field or pixel array, each of which is individually capable of detecting laser radiation. 62. The method of claim 61, wherein the at least one array comprises an array of charge collectors or charge detectors. 63. Method according to one of claims 56 to 62, wherein the coin (4) is allowed to run along the path in such a way that the coin is aligned absolutely perpendicular to the laser beam at the point of interruption. 64. A method according to any one of claims 56 to 63, wherein the value of the coin is credited to a credit card or account.