WO2001099047A1

WO2001099047A1 - Bar code system

Info

Publication number: WO2001099047A1
Application number: PCT/GB2001/002720
Authority: WO
Inventors: Joseph Paul Mariette D'haens; Jan Jansen; Malcolm Reginald Hallas Bell
Original assignee: Money Controls Plc
Priority date: 2000-06-21
Filing date: 2001-06-20
Publication date: 2001-12-27
Also published as: EP1297490A1; EP1297490B1; AU2001274278A1; DE60143943D1; GB0015222D0; US20030121979A1

Abstract

A bar code comprises a data track (3; 104; 205; 304) and a clock track (4; 103; 204; 303). The separate clock track (4; 103; 204; 303) means that the sampling of the data track (3; 104; 205; 304) can be synchronised with the movement of the bar code. The addition of a reference track (5; 105; 206) enables the forming of the bar code into a ring containing a plurality of repetitions of the encoded data. The bar codes may form a continuous ring themselves or be discrete blocks arranged in a ring. Consequently, a coin-like object (1; 101; 201), such as a coin or a token, can be marked with the bar code and the bar code can be read as the coin-like object (1; 101; 201) falls past an optical sensing station (26, 27; 226, 227) with sensors for reading respectively the clock data and reference tracks.

Description

Bar Code System

Field of the Invention

The present invention relates to a method of bar coding an object comprising forming a data pattern on an object, and forming a clock pattern on the object, the clock pattern being aligned with the data pattern for providing a data pattern sampling signal and to a bar-coded object, e.g. a sheet or a coin-like object, having a data pattern and a clock pattern formed as concentric rings, the clock pattern being aligned with the data pattern for providing a data pattern sampling reference.

Background to the Invention

Bar codes are well known and are widely used for marking objects with machine- readable information. Everyone is familiar with the bar codes found on groceries for instance.

Conventional 1-dimensional bar codes suffer from the problem that the object carrying the bar code must be oriented correctly for a bar code scanner to be able to read the bar code. Consequently, bar codes have not been successfully used on objects that can have an arbitrary orientation during handling, for example tokens or coins in an acceptor, CDs and CD-ROMs, without special means being provided to put the object into the correct orientation for reading of the bar code. However, the provision of such special means is itself undesirable and a disincentive to the use of bar codes on arbitrarily orientable objects because of the mechanical complexity that would be introduced into the object handling apparatus.

A circular barcode including an inner data patter and an outer clock pattern is described in GB-A-1218349. However, the described bar code cannot be read at arbitrary orientations while moving linearly. Instead, the code must be rotated through 360°.

Summary of the Invention

A bar-coded object according to the present invention is characterised in that the data pattern comprises a plurality of repetitions of the same information arranged in a ring such that a complete instance of said information can be obtained from a single chordal scan through the data pattern without limitation on the direction of said scan.

Thus, since the clock pattern moves with the data pattern, it can be used to trigger sampling of the data pattern. Consequently, the process of reading of the data is not affected by variations in the speed of the object. Furthermore, the barcode can read regardless of the orientation of the object about the axis passing perpendicularly through the centre of the bar code rings.

The patterns are preferably optically readable. However, the patterns may be, for example, magnetically readable.

The data pattern elements are preferably binary in nature. However, a multilevel code could be used.

The clock pattern and the or each data pattern may be formed as concentric rings. In this case, the data pattern is preferably located inwards of the clock pattern and a substantially circular reference pattern is optionally formed concentric with the clock pattern, the reference pattern identifying the start of each repetition of said information. An alternative to the use of a reference pattern is the use of a charaαeristic "start" code at the beginning of each repetition of the data pattern. If a reference pattern is used, the data pattern is preferably located within the clock pattern and the clock pattern is preferably located inwards of the reference pattern. Alternatively, the clock pattern may be located within the data pattern and the data pattern is located inwards of the reference pattern.

The presence of some form of "start" making means that, as long as all of the elements required for one instance of the information are read, even if the end part is read before the beginning, the start of the information can be found when reading the data pattern and the information recovered.

The patterns need not themselves be ring-shaped. Instead, the each repetition of the information may lie on a chord of a ring, preferably parallel to and alongside the clock pattern. Advantageously, the start of each repetition is marked.

According to the present invention, there is provided a method of forming a coin-like object, e.g. a coin or a token, including bar coding the object by a method according to the present invention.

According to the present invention, there is provided a method of reading a bar-coded object according to the present invention, the method comprising scanning said patterns simultaneously and deterniining the values of data pattern elements at times defined by said clock pattern.

For coin-like or substantially disc-shaped objects, the reading method preferably comprises simultaneously scanning said patterns chordally and determining the values of the data pattern elements at times defined by said clock pattern.

According to the present invention, there is provided a bar code reading apparatus for reading a bar code on an object according to the present invention, the apparatus comprising scanning means for simultaneously scanning said patterns chordally and means for determining the values of data pattern elements at times defined by said clock pattern.

Processing means may be included for re-ordering said pattern element values to recover said information. In this case, the processing means is preferably configured for identifying a start position and, if necessary, moving one or more bits from before the start position to a position after the start position.

Preferably, another part of each of the patterns is simultaneously scanning chordally also, the values of the data elements obtained in each scanning of the data pattern are compared and an error condition is signalled if there is a mismatch between information represented by the values obtained from said scans of the data pattern. The or each scanning may be performed by guiding a bar-coded object past a fixed sensor station.

Preferably, a first sensor is used for sensing the data pattern, a second sensor is used for sensing the clock pattern and a third sensor is used for sensing a start position reference.

Processing means may be configured such that a representation of said information is built from the output of the first sensor and cleared in dependence on the output of the third sensor. Preferably, the processing means counts pattern elements during said building and resets the pattern element count in dependence on the output of the third sensor. More preferably, the processing means is configured to produce an output if said reference meets a predetermined criterion when the pattern element count is at a threshold value.

A bar code reading apparatus according to the present invention may be used in a validator for coin-like objects.

Brief Description of the Drawings

Figure 1 shows a first bar-coded object according to the present invention in a first orientation;

Figure 2 shows the first bar-coded object of Figure 1 in a second orientation;

Figure 3 is an exaggerated, partial sectional view of the object of Figure 1;

Figure 4 is a side sectional view of part of the coin path of a coin validator according to the present invention with a coin-like object present; Figure 5 is a side sectional view of part of the coin path of a coin validator according to the present invention without a coin-like object being present;

Figure 6 is a partially cut away front view of the coin validator of Figure 4;

Figure 7 is a block diagram of the optical signal processing circuitry of the coin validator of

Figure 4; Figure 8 is a set of flowcharts illustrating the operation of the bar code processing of the validator of Figure 4;

Figure 9 is a waveform diagram illustrating the operation of the circuit of Figure 7 with the object as shown in Figure 1; Figure 10 is a waveform diagram illustrating the operation of the circuit of Figure 7 with the object as shown in Figure 2;

Figure 11 shows a second bar-coded object according to the present invention;

Figure 12 is a waveform diagram illustrating the signals obtained by optically sensing the object of Figure 11;

Figure 13 shown a third bar-coded object according to the present invention in a first orientation;

Figure 14 shows the third bar-coded object of Figure 13 in a second orientation;

Figure 15 is a side sectional view of part of the coin path of a coin validator according to the present invention with a coin-like object present;

Figure 16 is a side sectional view of part of the coin path of the coin validator of Figure 15 without a coin-like object being present;

Figure 17 is a partially cut away front view of the coin validator of Figure 15;

Figure 18 is a block diagram of the optical signal processing circuitry of the coin validator of Figure 15;

Figure 19 is a set of flowcharts illustrating the operation of the bar code processing of the validator of Figure 18;

Figure 20 is a waveform diagram illustrating the operation of the circuit of Figure 18 with the third object as shown in Figure 13; and Figure 21 is a waveform diagram illustrating the operation of the circuit of Figure 18 with the third object as shown in Figure 14.

Detailed Description of Preferred Embodiments

Embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings.

Referring to Figures 1 and 2, a bar-coded token 1 according to the present invention comprises a disc-shaped substrate 2. Three rings of "light" and "dark" markings 3, 4, 5 are formed concentrically on the substrate 2. The inner ring 3 comprises a repeating pattern of dark markings 6, 7, 8 on a light background. The circumferential extent of each of the dark markings 6, 7, 8 is defined by a pair of radii of the inner ring 3 so that they taper towards its middle. In the present example, the inner ring 3 comprises sixteen repetitions of the binary code for "83". The middle ring 4 comprises 128 equispaced, dark radial bars 9 on a light background. The dark radial bars 9 are all the same size and significantly narrower than the widest part of the 1-bit dark markings 6, 7 in the inner ring 3. The purpose of the middle ring 4 is to provide a "clock" signal for the sampling of the bits of the inner and outer ring patterns 3, 5.

The outer ring 5 comprises 16 equispaced bars 10 which are broadened radial extensions of respective bars 8 of the middle ring 4. The purpose of the bars 10 in the outer ring 5 is to mark the start of each pattern repetition in the inner ring 3.

Referring to Figure 3, the "dark" markings (an outer ring marking 10 is shown) comprise depressions in the substrate 2, which in this example is metallic and therefore inherently reflective. These depressions are prism-shaped with their axes extending radially with respect to the substrate 2. The angles α, β, γ at the edges of the prism-shaped depressions are chosen so as to avoid retroreflection. In the example shown, angles α and γ are 30° and angle β is 120°. Consequently, a sensor positioned beside the source of a beam 11 incident perpendicularly on the substrate 2 will be avoided by the reflected beams 12, 13 from a depression.

Referring to Figures 4, 5 and 6, a validator for coin-like objects 1 has a vertical coin path 21 defined by front and back walls 22, 23 and first and second side walls 24, 25. Left and right sensor stations 26, 27 are mounted to the front wall 22. The left sensor station 26 is located at the left side of the front wall 22 and comprises three light emitting diode units 28a, 28b, 28c alternating with three photo-sensors 29a, 29b, 29c. The right sensor station 17 is located at the right side of the front wall and is similarly constructed with three light emitting diode units 30a, 30b, 30c and three photo-sensors 31a, 31b, 31c. It is preferred that at least the middle light emitting diode unit 28b, 30b of each sensor station 26, 27 emits a beam which is narrower than the circumferential width of the "dark" markings 9 of the middle ring 4. A laser diode may be usefully employed for this purpose, and indeed for the other light emitting diode units 28a, 28c, 30a, 30c. The narrower beam produces sharper transitions in the output signals of the corresponding photo-sensor. Sharp transitions are particularly desirable in the case of the clock markings in the middle ring because, as will be seen, it is the light-to-dark transitions of the clock ring 4 that trigger sampling of the photo-sensor signals for the inner and outer rings 3, 5.

A strip 32 of retroreflective material is affixed across the back wall 23 to reflect light from the light emitting diode units 28a, 28b, 28c, 30a, 30b, 30c back to the photo-sensor 29a, 29b, 29c, 31a, 31b, 31c in the absence of a coin-like object 1.

An infrared light-emitting diode (LED) 33 is mounted in the first side wall 24 and an infrared light sensor 34 is mounted in the second side wall 25 directly opposite the LED 33. The LED 33 and the light sensor 34 are for detecting the passage of a coin-like object 1 and are located above, the sensor stations 26, 27 such that the beam 35 from the LED 33 to the light sensor 34 ceases to be broken by a coin-like object 1 when the sensor stations 26, 27 can no longer properly detect the rings 3, 4, 5 on the coin-like object 1.

The coin path 21 is dimensioned so that it is just wide and thick enough for the coin-like object 1 to fall freely therein.

Referring again to Figures 1 and 2, the dashed lines indicate the "tracks" of the photo-sensors 29a, 29b, 29c, 31a, 31b, 31c as the coin-like object 1 falls past the sensor stations 26, 27.

Referring to Figure 7, the optical signal processing circuit of the validator comprises a microcontroller 41, seven signal conditioning circuits 42, ..., 48, four latches 49, 50, 51, 52 and an inverter 61. The microcontroller 41 has at least first to fourth 1- bit inputs 53, 54, 55, 56 and at least first to fourth rising edge triggered interrupt ports 57, 58, 59, 60.

The first signal conditioning circuit 42 is connected between the light sensor 34 and the first interrupt port 57. The output of the first signal conditioning circuit 42 is also connected to the input of the inverter 61. The output of the inverter 61 is connected to the fourth interrupt port 60. The first signal conditioning circuit 42 squares and inverts the output of the light sensor 34. A delay may need to be interposed between the inverter 61 and the fourth interrupt port 60 to ensure that processing is not terminated while the bar code patterns are still being sensed by the left and right sensor stations 26, 27.

The second signal conditioning circuit 43 is connected between the first photosensor 29a of the left sensor station 26 and the data input of the first latch 49. The output of the first latch 49 is connected to the first 1-bit input 53. The second signal conditioning circuit 43 squares and inverts the output of the first photosensor 29a of the left sensor station 26.

The third signal conditioning circuit 44 is connected between the second photosensor 29b of the left sensor station 26 and the second interrupt port 58. The output of the third signal conditioning circuit 44 is also connected to the clock inputs of the first and second latches 49, 50. The third signal conditioning circuit 44 squares and inverts the output of the second photo-sensor 29b of the left sensor station 26 before applying it to the second interrupt port 58.

The fourth signal conditioning circuit 45 is connected between the third photosensor 29c of the left sensor station 26 and the data input of the second latch 50. The output of the second latch 50 is connected to the second 1-bit input 54. The fourth signal conditioning circuit 45 squares and inverts the output of the third photo-sensor 29c of the left sensor station 26.

The fifth signal conditioning circuit 46 is connected between the first photo-sensor 31a of the right sensor station 27 and the data input of the third latch 51. The output of the third latch 51 is connected to the third 1-bit input 55. The fifth signal conditioning circuit 46 squares and inverts the output of the first photo-sensor 31a of the right sensor station 27.

The sixth signal conditioning circuit 47 is connected between the second photosensor 31b of the right sensor station 27 and the third interrupt port 59. The output of the signal conditioning circuit 47 is also connected to the clock inputs of the third and fourth latches 51, 52. The sixth signal conditioning circuit 47 squares the output of the second photo-sensor 31b of the right sensor station 27 before applying it to the third interrupt port 59.

The seventh signal conditioning circuit 48 is connected between the third photo- sensor 31c of the right sensor station 27 and the data input of the fourth latch 52. The output of the fourth latch 52 is connected to the fourth 1-bit input 56. The seventh signal conditioning circuit 48 squares and inverts the output of the third photo-sensor 3 lc of the right sensor station 27.

The microcontroller 41 also has a control output to an accept gate (not shown) of the validator.

The operation of the validator with the coin-like object 1 will now be described.

Figures 9(a) and 10(a) show the output of the first signal conditioning circuit 42 as the object 1 passes. Figures 9(b) and 10(b) show the output of the third signal conditioning circuit 44 as the object 1 passes, oriented as shown in Figures 1 and 2 respectively. Figures 9(c) and 10(c) show the output of the second signal conditioning circuit 43 as the object 1 passes, oriented as shown in Figures 1 and 2 respectively. Figures 9(d) and 10(d) show the output of the fourth signal conditioning circuit 45 as the object 1 passes, oriented as shown in Figures 1 and 2 respectively. Figures 9(e) and 10(e) show the data read in by the microcontroller 41 with the object 1 oriented as shown in Figures 1 and 2 respectively.

Referring to Figures 9 and 10, the microcontroller 41 is alerted to the coin-like object 1 being in the coin path 11 by the output of the first signal conditioning circuit 42 going high (see Figures 9(a) and 10(a)). The microcontroller 41 responds by performing a first interrupt routine (see Figure 8(a)). The first interrupt routine includes setting left and right counts to zero (steps si and s2) and setting left and right start and stop bit positions to a default value (99 in this case) (steps s3 and s4).

As the coin-like object 1 progresses down the coin path 11, it encounters the beams from the laser diode units 28a, 28b, 28c, 30a, 30b, 30c and reflects them to the respective photo-sensors 29a, 29b, 29c, 31a, 31b, 31c. Thus, reflections from the coin-like object 1 replace reflections from the retroreflective strip 32 (Figures 4 and

5)-

5 Until the output of the first signal conditioning circuit 42 changes state again, the operation of the circuit of Figure 7 is controlled by the outputs (Figures 9(b) and 10(b)) of the middle photo-sensors 29b, 31b of the left and right sensor stations 26, 27.

0 Considering the case of the left sensor station 26, each time the output of the second photo-sensor 29b goes low, the output of the third signal conditioning circuit 44 goes high. This causes the outputs of the second and fourth signal (Figures 9(c) and (d) and 10(c) and (d)) conditioning circuits 43, 45 to be loaded into the first and second latches 49, 50. The second interrupt port 58 detects the 5 rising edge as the output of the third signal conditioning circuit 44 goes high and initiates a second interrupt routine (Figure 8(b)). Latching the outputs (Figures 9(e) and 10(e)) of the second and fourth signal conditioning circuits 43, 45 ensures that the desired photo-sensor output values is maintained until the first interrupt routine has been able to read the first and second 1-bit ports 53, 54, irrespective of any 0 actual changes in the photo-sensor outputs.

In the second interrupt routine, the microcontroller 41 first reads (step sll) and stores (step si 2) the values (1 or 0) at the first and second 1-bit ports 43, 44. The first and second 1-bit ports 43, 44 may be elements of a single 8-bit port, in which -5 case reading these ports is a single operation.

After reading the first and second 1-bit ports 43, 44, the microcontroller 41 increments the left count (step si 3). If the first 1-bit port's value was 1 (step si 4) and the left start bit position (LeftStart) value is 99 (step sl5), the microcontroller 0 41 assigns the left count value to the left start bit position (step si 6). Otherwise, the first 1-bit port's value is assigned to the left stop bit position (LeftStop) (step sl7). The second 1-bit port's value is stored in the elements of an array indexed by the left count value (step si 8). Considering now the case of the right sensor station 27, each time the output of the second photo-sensor 31b goes high, the output of the sixth signal conditioning circuit 47 goes high. This causes the outputs of the fifth and seventh signal conditioning circuits 46, 48 to be loaded into the third and fourth latches 51, 52. The third interrupt port 59 detects the rising edge as the output of the sixth signal conditioning circuit 47 goes high and initiates a third interrupt routine (Figure 8(c)).

In the third interrupt routine, the microcontroller 41 first reads (step s21) and stores the values (1 or 0) at the third and fourth 1-bit ports 55, 56 (step s22).

After reading the third and fourth 1-bit ports 55, 56, the microcontroller 41 increments the right count (step s23). If the fourth 1-bit port's value was 1 (step s24) and the right stop bit position value is 99 (step s25), the microcontroller 41 assigns the right count value to the right stop bit position (RightStop) (step s26). Otherwise, the third 1-bit port's value is assigned to the right start bit position (RightStart) (step s27). The fourth 1-bit port's value is stored in the elements of another array indexed by the right count value (step s28).

When the coin-like object 1 completes its passage through the light beam 35, the light sensor 34 is again illuminated and the output of the first signal conditioning circuit 42 goes low, causing the output of the inverter 61 to go high. This triggers a fourth interrupt routine (Figure 8(d)).

In the fourth interrupt routine, the microcontroller 41 processes the signals from the sensor stations 26, 27.

Starting with the left sensor station 26, the microcontroller 41 determines whether a stop bit was detected by determining whether the stop bit value equals 99 (step s41). If not, i.e. a stop bit was found, as would be the case with the object shown in

Figure 1, the microcontroller 41 enters a loop (steps s42, s43 and s44) in which the data is reassembled thus: -

(pseudocode) for i := 0 to NumberOfDataBits - 1 do begin for j := 0 to i do

LeftResult := leftshift(DataArray[i]) end

Otherwise, for instance in the case of the object as shown in Figure 2, the microcontroller 41 enters another loop (steps s45, s46 and s47) in which the data is reassembled thus:- (pseudocode) for i := 0 to NumberOfDataBits - 1 do begin for j := 0 to i do

LeftResult := leftshift(DataArray[LeftStart - 4 + i]) end

After the data (LeftResult) from the left sensor station 26 has been reassembled, the microcontroller 41 reassembles the data (RightResult) from right sensor station 27. The microcontroller 41 determines whether a start bit was detected by determining whether the start bit value equals 99 (step s48). If not, i.e. a start bit was found, the microcontroller 41 enters a loop (steps s49, s50 and s51) in which the data is reassembled thus: -

(pseudocode) for i := 0 to NumberOfDataBits - 1 do begin for j := 0 to i do

RightResult := leftshift(DataArray[NumberOfDataBits - 1 - i]) end

Otherwise, the microcontroller 41 enters another loop (steps s52, s53 and s54) in which the data is reassembled thus:- (pseudocode) for i := 0 to NumberOfDataBits - 1 do begin for j := 0 to i do

RightResult := leftshift(DataArray[RightStop - 4 - (NumberOfDataBits - 1 - i)]) end

When the data (LeftResult and RightResult) from the left and right sensor stations 26, 27 has been recovered, the microcontroller 41 compares them (step s55) and, if they do not match, the microcontroller 41 logs a rejection (step s56) and exits the fourth interrupt routine. However, if they do match, the microcontroller 41 compares the recovered data with a reference value, "83" in this case, (step s57). If the recovered value does not match the reference value, the microcontroller 41 logs a rejection (step s58) and exits the fourth interrupt routine. However, if they do match, the microcontroller 41 sends a signal to open the accept gate of the validator (step s59) and exits the fourth interrupt routine.

It is to be understood that the signal for opening the accept gate may be produced subject to the coin-like object passing additional tests using, for example, electromagnetic sensors, as are well-known in the art.

A second embodiment of the present invention will now be described.

Referring to Figure 11, a bar-coded object 101 is substantially the same as that shown in Figure 1 save that the inner ring 103 holds the "clock" pattern and the middle ring 104 holds the data.

The validator shown in Figures 4, 5 and 6 can be used with the token of Figure 11 by the simple expedient of swapping the positions of the second and third photo-sensors 29b, 29c, 31b, 31c within each sensor station 26, 27. It will be appreciated that no changes are required to the circuit of Figure 7 if these sensors are swapped as described.

Figure 12(a) shows the output of the first signal conditioning circuit 42 as the object 101 passes. Figure 12(b) shows the output of the third signal conditioning circuit 44 as the object 101 passes, oriented as shown. Figure 12(c) shows the output of the fourth signal conditioning circuit 43 as the object 101 passes, oriented as shown. Figure 12(d) shows the output of the second signal conditioning circuit 45 as the object 101 passes, , oriented as shown. Figure 12(e) shows the data read in by the microcontroller 41 with the object 101 oriented as shown.

Referring to Figures 11 and 12, it can be seen that as the "track" 110 of the third photosensor 29b, now the furthest inboard, of the left sensor station 26 crosses the middle ring 104, the output of the third photo-sensor 29b changes, causing the microcontroller 41 to read the data and start bit values from the first and second latches 49, 50. In the example shown, the result is two extra 0s at the beginning of the read data. No unwanted samples are taken at the end because the beam 35 is no longer broken (Figure 12(a)). This is not a problem, because these bits will be ignored when the true data is located using the start bit position. However, care must be taken when designing the bar code to ensure that false clocking by the middle ring 104 does not result in the outer photo-sensors 29a, 31a detecting dark regions and a start or stop bit being falsely identified.

Since, the start bits are crucial in the first and second embodiments for locating the "good" data, the start bits should be in the outer ring to prevent the start bit photo-sensor having the possibility of sensing data in the wrong ring.

A third embodiment of the present invention will now be described.

Referring to Figures 13 and 14, a third bar-coded token 201 according to the present invention comprises a disc-shaped substrate 202. Eighteen barcode blocks 203 are arranged in a ring around the margin of the face of the substrate 202. Each barcode block 203 is aligned along a chord of the substrate and comprises outer, middle and inner tracks 204, 205, 206 comprising alternating light and dark regions. The outer track 204 of each block 203 comprises a clock pattern. The middle track 205 of each block 203 comprises a 5-bit data pattern. The inner track 206 of each block contains a start position marker. In the present example, the middle tracks 204 all comprise the binary code for " 13" .

Referring to Figures 15, 16 and 17, a validator for coin-like objects 201 has a vertical coin path 221 defined by front and back walls 222, 223 and first and second side walls 224, 225. Left and right sensor stations 226, 227 are mounted to the front wall 222. The left sensor station 226 is located at the left side of the front wall 222 and comprises three light emitting diode units 228a, 228b, 228c alternating with three photo-sensors 229a, 229b, 229c. The right sensor station 227 is located at the right side of the front wall and is similarly constructed with three light emitting diode units 230a, 230b, 230c and three photo-sensors 231a, 231b, 231c. It is preferred that at least the middle light emitting diode unit 228b, 230b of each sensor station 226, 227 emits a beam which is narrower than the circumferential width of the "dark" markings outer tracks 204. A laser diode may be usefully employed for this purpose, and indeed for the other light emitting diode units 228a, 228c, 230a, 230c. The narrower beam produces sharper transitions in the output signals of the corresponding photo-sensor. Sharp transitions are particularly desirable in the case of the clock patterns in the outer tracks 204 because, as will be seen, it is the light-to-dark transitions of these patterns that trigger sampling of the photo-sensor signals for the inner and middle tracks 205, 206.

The coin path 21 is dimensioned so that it is just wide and thick enough for the coin-like object 201 to fall freely therein.

Referring again to Figures 13 and 14, the dashed lines indicate the "tracks" of the photo-sensors 229a, 229b, 229c, 231a, 231b, 231c as the coin-like object 201 falls past the sensor stations 226, 227.

Referring to Figure 18, the optical signal processing circuit of the validator comprises a microcontroller 241, six signal conditioning circuits 243, ..., 247 and four latches 249, 250, 251, 252. The microcontroller 241 has at least first to fourth 1-bit inputs 253, 254, 255, 256 and at least first and second rising edge triggered interrupt ports 258, 259.

The first signal conditioning circuit 243 is connected between the second photosensor 229b of the left sensor station 226 and the data input of the first latch 249. The output of the first latch 249 is connected to the first 1-bit input 253. The first signal conditioning circuit 243 squares and inverts the output of the second photo- sensor 229b of the left sensor station 226.

The second signal conditioning circuit 244 is connected between the first photosensor 229a of the left sensor station 226 and the second interrupt port 258. The output of the second signal conditioning circuit 244 is also connected to the clock inputs of the first and second latches 249, 250. The second signal conditioning circuit 244 squares and inverts the output of the first photo-sensor 229a of the left sensor station 226 before applying it to the second interrupt port 258.

The third signal conditioning circuit 245 is connected between the third photosensor 229c of the left sensor station 226 and the data input of the second latch 250. The output of the second latch 250 is connected to the second 1-bit input 254. The third signal conditioning circuit 245 squares and inverts the output of the third photo-sensor 229c of the left sensor station 226.

The fourth signal conditioning circuit 246 is connected between the second photosensor 231b of the right sensor station 227 and the data input of the third latch 251. The output of the third latch 251 is connected to the third 1-bit input 255. The fourth signal conditioning circuit 246 squares and inverts the output of the second photo-sensor 241a of the right sensor station 227.

The fifth signal conditioning circuit 247 is connected between the first photo-sensor 231a of the right sensor station 227 and the third interrupt port 259. The output of the fifth signal conditioning circuit 247 is also connected to the clock inputs of the third and fourth latches 251, 252. The fifth signal conditioning circuit 247 squares the output of the first photo-sensor 231b of the right sensor station 227 before applying it to the third interrupt port 259.

The sixth signal conditioning circuit 248 is connected between the third photo- sensor 231c of the right sensor station 227 and the data input of the fourth latch 252. The output of the fourth latch 252 is connected to the fourth 1-bit input 256. The sixth signal conditioning circuit 248 squares and inverts the output of the third photo-sensor 231c of the right sensor station 227. The microcontroller 241 also has a control output to an accept gate (not shown) of the validator.

The operation of the validator shown in Figures 15 to 18 with the coin-like object 201 will now be described.

Figures 20(a) and 21(a) show the output of the second signal conditioning circuit 244 as the object 201 passes, oriented as shown in Figures 13 and 14 respectively. Figures 20(b) and 21(b) show the output of the first signal conditioning circuit 243 as the object 201 passes, oriented as shown in Figures 13 and 14 respectively. Figures 20(c) and 21(c) show the output of the third signal conditioning circuit 245 as the object 201 passes, oriented as shown in Figures 13 and 14 respectively. Figures 20(d) and 21(d) show the data read by the microcontroller 241 with the object 201 oriented as shown in Figures 13 and 14 respectively.

Referring to Figures 20 and 21, as the object 201 falls down the coin path 221, the second photo-sensor 229b of the left sensor station 226 and the the second photosensor 230b of the right sensor station 226 eventually detect the outer tracks 204 of barcode blocks 203.

Considering now the case of the left sensor station 226, when the output of the second signal conditioning circuit 244 goes high, the outputs of the first and third signal conditioning circuits 243, 245 are loaded respectively into the first and second latches 249, 250. At the same time, the microcontroller 241 responds to the rising edge on its first interrupt port 258 by performing a first interrupt routine (Figure 19).

In the first interrupt routine, the microcontroller 241 first reads the value at the second 1-bit port 254 (step s201). If this value is 0 (step s202), the microcontroller 241 increments a counter (step s203) and then left-shifts a single- ord output data variable (step s204). The microcontroller 241 then adds the value at the first 1-bit port to the output data variable (step s205). At this point, if the value in the counter is 5, i.e. the number of bits in the code to be read from the object 201, (step s206), the output data variable is compared with a reference value (step s207). If the output data variable and the reference value match (step s207), the microcontroller 241 outputs a signal to open the accept gate (step s208). In either case, the. counter is reset to 0 (step s209) and the output data variable is reset to 00000 (step s210).

If the answer at step s206 is no, the interrupt routine terminates.

If the input value is found to be 1 at step s202, the counter is reset to 0 (step s209) and the output data variable is reset to 00000 (step s210).

The processing in response to signals from the right sensor station 227 is performed by a second interrupt routine which is identical to the first except that the 5 -least significant bits of the reference value are reversed to reflect the different orders in which the bits are read. For example, if the reference value for the left sensor station 226 is 00001101, the reference for the right sensor station 227 will be 00010110.

A timer may be set in each of the interrupt routines. On expiry the timer triggers a third interrupt routine that resets the counters and output data variables. The timer period is preferably set to be slightly longer that the effective clock period set by the pitch of the outer tracks 204.

A monostable mulitvibrator may be included between the accept gate control output of the microcontroller 241 and the accept gate actuator to prevent the actuator only responds to the first accept gate open signal that the microcontroller 241 produces for the object 201 currently being analysed.

Many modifications may be made to the described embodiments. For instance, the data need not be a single number of character code and may represent a plurality of numbers or character codes. The discrete optical sensors at each sensor station for sensing the bar code elements may be replaced by a linear CCD optical sensor. If a linear CCD optical sensor is used, some elements may be masked to prevent cros/s-talk between the signals produced by the data, clock and start reference tracks. Also, the alternating emitter/sensor arrangement described above could be replaced by an arrangement wherein the row of emitters at a sensor station is arranged immediately above or below a row of sensors.

Claims

1. A method of bar coding an object comprising: forming a data pattern (3; 104; 205) on an object (1; 101; 201), and forming a clock pattern (4; 103; 204) on the object (1; 101; 201), the clock pattern

(4; 104; 204) being aligned with the data pattern (3; 103; 205) for providing a data pattern sampling signal, characterised in that the data pattern (3; 104; 205) comprises a plurality of repetitions of the same information arranged in a ring such that a complete instance of said information can be obtained from a single chordal scan through the data pattern without limitation on the direction of said scan.

2. A method according to claim 1, wherein the clock pattern (4; 103) and the data pattern (3; 104) are formed as concentric rings.

3. A method according to claim 2, wherein the data pattern (3) is located inwards of the clock pattern (4).

4. A method according to claim 2, including forming a substantially circular reference pattern (5; 105) concentric with the clock pattern (4; 103), the reference pattern identifying the start of each repetition of said information.

5. A method according to claim 4, wherein the data pattern (3) is located within the clock pattern (4) and the clock pattern is located inwards of the reference pattern (5).

6. A method according to claim 4, wherein the clock pattern (103) is located within the data pattern (104) and the data pattern (104) is located inwards of the reference pattern (105).

7. A method according to claim 1, wherein the clock pattern (204) comprises a plurality of repetitions of a straight clock pattern segment and each instance of the data pattern (205) is straight and has a clock pattern segment arranged in parallel alongside it.

8. A method according to claim 7, including marking the start of each instance of the data pattern.

9. A method of forming a coin-like object including bar coding the object by a method according to any one of claims 1 to 8.

10. A bar-coded object having a data pattern (3; 104, 205) and a clock pattern (4; 103; 204) formed as concentric rings, the clock pattern (4; 103; 204) being aligned with the data pattern (3; 104; 205) for providing a data pattern sampling reference, characterised in that the data pattern (3; 104; 205) comprises a plurality of repetitions of the same information arranged in a ring such that a complete instance of said information can be obtained from a single chordal scan through the data pattern (3; 104; 205) without limitation on the direction of said scan.

11. An object according to claim 10, wherein the data pattern (3; 104; 205) is located inwards of the clock pattern (4; 103; 204).

12. An object according to claim 10, including a substantially circular reference pattern (5; 105) concentric with the clock pattern (4; 103), the reference pattern (5; 105) identifying the start of each repetition of said information.

13. An object according to claim 12, wherein the data pattern (3) is located within the clock pattern (4) and the clock pattern (4) is located inwards of the reference pattern (5).

14. An object according to claim 12, wherein the clock pattern (103) is located within the data pattern (104) and the data pattern (104) is located inwards of the reference pattern (105).

15. An object according to claim 10, wherein the clock pattern (204) comprises a plurality of repetitions of a straight clock pattern segment and each instance of the data pattern information is straight and has a clock pattern segment arranged in parallel alongside it.

16. An object according to claim 15, including a marking (206) at the start of each instance of the data pattern.

17. A coin-like object according to any one of claims 10 to 16.

18. A method of reading a bar-coded object according to claim 10, the method comprising:- simultaneously scanning said patterns (3, 4, 5; 103, 104, 105; 204, 205, 206) chordally; and determining the values of data pattern elements at times defined by said clock pattern (4; 103; 204).

19. A method according to claim 18, including re-ordering said pattern element values to recover said information.

20. A method according to claim 19, wherein said re-ordering comprises identifying a start position and moving a bit from before the start position to a position after the start position.

21. A method according to claim 18, including: simultaneously scanning chordally another part of each of the patterns (3, 4, 5; 103, 104, 105; 204, 205, 206); comparing the values of the data elements obtained in each scanning of the data pattern; and signalling an error condition if there is a mismatch between information represented by the values obtained from said scans of the data pattern.

22. A method according to claim 18, wherein the data pattern (3; 104; 205), the clock pattern (4; 103; 204) and a start position reference pattern (5; 105; 206) are sensed by respective sensors (29a, 29b, 29c) along parallel chordal paths.

23. A method according to claim 22, wherein a representation of said information is built from the output of the data pattern sensor (29b; 29c) and cleared in dependence on the output of the start position reference pattern sensor (29a).

24. A method according to claim 23, including counting each bit as it is added to said representation, perforrning an action when the bit count reaches a predeterrnined value and resetting the bit count in dependence on the output of the start position reference pattern sensor.

25. A method according to claim 24, wherein said action is only performed if said representation meets a predetermined criterion.

26. A bar code reading apparatus for reading a bar code on an object according to claim 10, the apparatus comprising: scanning means (26; 226) for simultaneously scanning said patterns (3, 4, 5; 103, 104, 105; 204, 205, 206) chordally; and means (41; 241) for determining the values of data pattern elements at times defined by said clock pattern (4; 103; 204).

27. An apparatus according to claim 26, including processing means (41; 241) for reordering said pattern element values to recover said information.

28. An apparatus according to claim 27, wherein said re-ordering comprises identifying a start position and moving a bit from before the start position to a position after the start position.

29. An apparatus according to claim 26, including: means (27; 227) for simultaneously scanning chordally another part of each of the patterns (3, 4, 5; 103, 104, 105; 204, 205, 206); means (41; 241) for comparing the values of the data elements obtained in each scanning of the data pattern (3; 104; 205); and means (41; 241) for signalling an error condition if there is a mismatch between information represented by the values obtained from said scans of the data pattern (3; 104; 205).

30. An apparatus according to claim 26, 27 or 28, wherein the sensor means (26; 226) comprises a first sensor (29c; 29b; 229b) for sensing the data pattern (3; 104; 205), a second sensor (29b; 29c; 229a) for sensing the clock pattern (4; 103; 204) and a third sensor (29a; 229c) for sensing the start position reference pattern (5; 205; 206).

31. An apparatus according to claim 30, including processing means (41) configured such that a representation of said information is built from the output of the first sensor (29c; 29b) and cleared in dependence on the output of the third sensor (29a).

32. An apparatus according to claim 31, wherein the processing means (241) counts pattern elements during said building and resets the pattern element count in dependence on the output of the third sensor (229c).

33. An apparatus according to claim 32, wherein the processing means (241) is configured to produce an output if said reference meets a predetermined criterion when the pattern element count is at a threshold value.

34. A validator for coin-like objects including an apparatus according to any one of claims 26 to 33.

35. A method of bar coding an object comprising: providing an object having a substantially planar surface; forming a data pattern on said surface, and forming a clock pattern on said surface, the clock pattern being aligned with the data pattern for providing a data pattern sampling signal, wherein the data pattern comprises a plurality of repetitions of the same information arranged in a ring such that a complete instance of said information can be obtained from a single chordal scan through the data pattern without limitation on the direction of said scan.

36. A method according to claim 34, wherein the clock pattern and the data pattern are formed as concentric rings.

37. A method according to claim 35, wherein the data pattern is located inwards of the clock pattern.

38. A method according to claim 35, including forming a substantially circular reference pattern concentric with the clock pattern, the reference pattern identifying the start of each repetition of said information.

39. A method according to claim 38, wherein the data pattern is formed within the clock pattern and the clock pattern is formed inwards of the reference pattern.

40. A method according to claim 38, wherein the clock pattern is formed within the data pattern and the data pattern is located inwards of the reference pattern.

41. A method according to claim 35, wherein forming the clock pattern comprises forming a plurality of repetitions of a straight clock pattern segment and forming of each instance of the data pattern comprises forming a straight data pattern such that each data pattern instance has a clock pattern segment arranged in parallel alongside it.

42. A method according to claim 41, including marking the start of each instance of the data pattern.

43. A method according to claim 35, wherein providing said object comprises providing a coin-like object.

44. A bar-coded object having a data pattern and a clock pattern formed as concentric rings, the clock pattern being aligned with the data pattern for providing a data pattern sampling reference, wherein the data pattern comprises a plurality of repetitions of the same information arranged in a ring such that a complete instance of said information can be obtained from a single chordal scan through the data pattern without limitation on the direction of said scan.

45. An object according to claim 44, wherein the data pattern is located inwards of the clock pattern.

46. An object according to claim 44, including a substantially circular reference pattern concentric with the clock pattern, the reference pattern identifying the start of each repetition of said information.

47. An object according to claim 46, wherein the data pattern is located within the clock pattern and the clock pattern is located inwards of the reference pattern.

48. An object according to claim 46, wherein the clock pattern is located within the data pattern and the data pattern is located inwards of the reference pattern.

49. An object according to claim 44, wherein the clock pattern comprises a plurality of repetitions of a straight clock pattern segment and each instance of the data pattern is straight and has a clock pattern segment arranged in parallel alongside it.

50. An object according to claim 49, including a marking at the start of each instance of the data pattern.

51. A bar-coded coin-like object having a data pattern and a clock pattern formed as concentric rings, the clock pattern being aligned with the data pattern for providing a data pattern sampling reference, wherein the data pattern comprises a plurality of repetitions of the same information arranged in a ring such that a complete instance of said information can be obtained from a single chordal scan through the data pattern without limitation on the direction of said scan.

52. An object according to claim 51, wherein the data pattern is located inwards of the clock pattern.

53. An object according to claim 51, including a substantially circular reference pattern concentric with the clock pattern, the reference pattern identifying the start of each repetition of said information.

54. An object according to claim 53, wherein the data pattern is located within the clock pattern and the clock pattern is located inwards of the reference pattern.

55. An object according to claim 53, wherein the clock pattern is located within the data pattern and the data pattern is located inwards of the reference pattern.

56. An object according to claim 51, wherein the clock pattern comprises a plurality of repetitions of a straight clock pattern segment and each instance of the data pattern is straight and has a clock pattern segment arranged in parallel alongside it.

57. An object according to claim 56, including a marking at the start of each instance of the data pattern.

58. A method of reading a bar-coded object having a data pattern and a clock pattern formed as concentric rings, the clock pattern being aligned with the data pattern for providing a data pattern sampling reference and the data pattern comprises a plurality of repetitions of the same information arranged in a ring such that a complete instance of said information can be obtained from a single chordal scan through the data pattern without limitation on the direction of said scan, the method comprising:- simultaneously scanning said patterns chordally using sensor means; determining the values of data pattern elements at times defined by said clock pattern from the output of the sensor means; and outputting a value in dependence on the determined data pattern element values.

59. A method according to claim 58, including re-ordering said pattern element values to recover said information.

60. A method according to claim 59, wherein said re-ordering comprises identifying a start position and moving a bit from before the start position to a position after the start position.

61. A method according to claim 58, including: simultaneously scanning chordally another part of each of the patterns using sensor means; comparing the values of the data elements obtained in each scanning of the data pattern; and signalling an error condition if there is a mismatch between information represented by the values obtained from said scans of the data pattern.

62. A method according to claim 58, wherein the data pattern, the clock pattern and a start position reference pattern are sensed by respective sensors, comprises in said sensor means, along parallel chordal paths.

63. A method according to claim 62, wherein a representation of said information is built from the output of the data pattern sensor and cleared in dependence on the output of the start position reference pattern sensor.

64. A method according to claim 63, including counting each bit as it is added to said representation, performing an action when the bit count reaches a predetermined value and resetting the bit count in dependence on the output of the start position reference pattern sensor.

65. A method according to claim 64, wherein said action is only performed if said representation meets a predetermined criterion.

66. A bar code reading apparatus for reading a bar code on an object having a data pattern and a clock pattern formed as concentric rings, the clock pattern being aligned with the data pattern for providing a data pattern sampling reference and the data pattern comprises a plurality of repetitions of the same information arranged in a ring such that a complete instance of said information can be obtained from a single chordal scan through the data pattern without limitation on the direction of said scan,, the apparatus comprising: scanning means for simultaneously scanning said patterns chordally; means for deteπnining the values of data pattern elements at times defined by said clock pattern in dependence on the output of the scanning means; and outputting a code value in dependence on said determined data pattern values.

67. An apparatus according to claim 66, including processing means for re-ordering said pattern element values to recover said information.

68. An apparatus according to claim 67, wherein said processing means is configured such that said re-ordering comprises identifying a start position and moving a bit from before the start position to a position after the start position.

69. An apparatus according to claim 66, including: means for simultaneously scanning chordally another part of each of the patterns; means for comparing the values of the data elements obtained in each scanning of the data pattern; and means for signalling an error condition if there is a mismatch between information represented by the values obtained from said scans of the data pattern.

70. An apparatus according to claim 66, wherein the sensor means comprises a first sensor for sensing the data pattern, a second sensor for sensing the clock pattern and a third sensor for sensing a start position reference pattern.

71. An apparatus according to claim 70, including processing means configured such that a representation of said information is built from the output of the first sensor and cleared in dependence on the output of the third sensor.

72. An apparatus according to claim 71, wherein the processing means counts pattern elements during said building and resets the pattern element count in dependence on the output of the third sensor.

73. An apparatus according to daim 72, wherein the processing means is configured to produce an output if said reference meets a predetermined criterion when the pattern element count is at a threshold value.

74. An apparatus according to daim 67, wherein the sensor means comprises a first sensor for sensing the data pattern, a second sensor for sensing the clock pattern and a third sensor for sensing a start position reference pattern.

75. An apparatus according to claim 74, including processing means configured such that a representation of said information is built from the output of the first sensor and cleared in dependence on the output of the third sensor.

76. An apparatus according to claim 75, wherein the processing means counts pattern elements during said building and resets the pattern element count in dependence on the output of the third sensor.

77. An apparatus according to claim 76, wherein the processing means is configured to produce an output if said reference meets a predetermined criterion when the pattern element count is at a threshold value.

78. An apparatus according to claim 68, wherein the sensor means comprises a first sensor for sensing the data pattern, a second sensor for sensing the clock pattern and a third sensor for sensing a start position reference pattern.

79. An apparatus according to claim 78, including processing means configured such that a representation of said information is built from the output of the first sensor and cleared in dependence on the output of the third sensor.

80. An apparatus according to claim 79, wherein the processing means counts pattern elements during said building and resets the pattern element count in dependence on the output of the third sensor.

81. An apparatus according to claim 80, wherein the processing means is configured to produce an output if said reference meets a predetermined criterion when the pattern element count is at a threshold value.

82. A validator for validating a coin-like object having a data pattern and a clock pattern formed as concentric rings, the clock pattern being aligned with the data pattern for providing a data pattern sampling reference and the data pattern comprises a plurality of repetitions of the same information arranged in a ring such that a complete instance of said information can be obtained from a single chordal scan through the data pattern without limitation on the direction of said scan, the apparatus comprising: scanning means for simultaneously scanning said patterns chordally; means for deteπnining the values of data pattern elements at times defined by said clock pattern in dependence on the output of the scanning means; and outputting a valid/invalid signal for the coin-like object in dependence on said determined data pattern values.

83. A validator according to claim 82, including processing means for re-ordering said pattern element values to recover said information.

84. A validator according to claim 83, wherein said processing means is configured such that said re-ordering comprises identifying a start position and moving a bit from before the start position to a position after the start position.

85. A validator according to claim 82, including: means for simultaneously scanning chordally another part of each of the patterns; means for comparing the values of the data elements obtained in each scanning of the data pattern; and means for signalling an error condition if there is a mismatch between information represented by the values obtained from said scans of the data pattern.

86. A validator according to claim 82, wherein the sensor means comprises a first sensor for sensing the data pattern, a second sensor for sensing the clock pattern and a third sensor for sensing a start position reference pattern.

87. A validator according to claim 86, including processing means configured such that a representation of said information is built from the output of the first sensor and cleared in dependence on the output of the third sensor.

88. A validator according to claim 87, wherein the processing means counts pattern elements during said building and resets the pattern element count in dependence on the output of the third sensor.

89. A validator according to claim 88, wherein the processing means is configured to produce an output if said reference meets a predetermined criterion when the pattern element count is at a threshold value.

90. A validator according to claim 83, wherein the sensor means comprises a first sensor for sensing the data pattern, a second sensor for sensing the clock pattern and a third sensor for sensing a start position reference pattern.

91. A validator according to claim 90, including processing means configured such that a representation of said information is built from the output of the first sensor and cleared in dependence on the output of the third sensor.

92. A validator according to claim 91, wherein the processing means counts pattern elements during said building and resets the pattern element count in dependence on the output of the third sensor.

93. A validator according to claim 92, wherein the processing means is configured to produce an output if said reference meets a predetermined criterion when the pattern element count is at a threshold value.

94. A validator according to claim 84, wherein the sensor means comprises a first sensor for sensing the data pattern, a second sensor for sensing the clock pattern and a third sensor for sensing a start position reference pattern.

95. A validator according to claim 94, including processing means configured such that a representation of said information is built from the output of the first sensor and cleared in dependence on the output of the third sensor.

96. A validator according to claim 95, wherein the processing means counts pattern elements during said building and resets the pattern element count in dependence on the output of the third sensor.

97. A validator according to claim 96, wherein the processing means is configured to produce an output if said reference meets a predetermined criterion when the pattern element count is at a threshold value.