WO2002071344A1

WO2002071344A1 - Detector system and method

Info

Publication number: WO2002071344A1
Application number: PCT/GB2002/000980
Authority: WO
Inventors: Steven Micheal Hosking; Bryan James Christophersen; Graham Ronald Morgans; Peter Mclean Henderson
Original assignee: De La Rue International Limited
Priority date: 2001-03-06
Filing date: 2002-03-06
Publication date: 2002-09-12
Also published as: GB0105509D0

Abstract

A method of detecting a characteristic of an article using a detector system, a transport (50) for transporting articles along a feed path; and a detector assembly including a characteristic sensor (14) for sensing a characteristic of the articles, the characteristic sensor being mounted to a support (15) to enable the sensor to be moved in a direction transverse to the feed path so as to be able to view laterally offset portions of an article. The method comprises moving the characteristic sensor (14) transverse to the feed direction when the article is located at a position at which it is expected that the characteristic will be sensed ; and monitoring output signals from the characteristic sensor. The article is stopped or moved more slowly while the characteristic sensor (914) is moved.

Description

DETECTOR SYSTEM AND METHOD

The invention relates to a detector system and method for detecting a characteristic of an article. It is common to provide articles with tags, authenticity characteristics and other features to enable the articles to be identified and/or noted as genuine. An important field in this area is that of security documents or documents of value such as banknotes, store vouchers and the like. Such documents typically carry authenticity characteristics such as metal threads, fluorescent or other covert features which need to be detected to confirm that the document is genuine. Furthermore, it is often a requirement to be able to identify the document by some characteristic feature, such as its denomination. For example, pattern recognition is currently achieved by passing a document at known speed across a detector head, which is normally as wide as the document being processed.

Metal threads are conventionally positioned perpendicular to the long edge of the document but may be variably positioned from either short edge of the document, particularly when dealing with documents from different countries or, if of the same country, of different denominations . Originally, the thread carried no data and its mere presence confirmed the security of the document. However, a recent innovation is to encrypt data along the length of the thread, which can be magnetically read by the passage of a suitable head along the length of the thread. See for example EP-A-0493438.

Conventionally, there are two philosophies for document handling in a transport, that involving a long edge input (i.e. long edge leading) and that of short edge input (i.e. short edge leading). Both techniques have their advantages and their disadvantages from the point of view of detecting characteristics such as security threads. Long Edge Transportation

Advantages

Provided the security thread can be positioned relative to a datum prior to the input of the document into the transport the data encrypted on the thread can be read by a single magnetic head.

Disadvantages

Single head reading cannot be achieved unless the documents are accurately orientated and the position tolerance of the thread with respect to a datum edge is within the range of the head scanning width.

Short Edge Transportation

Advantages

The presence of a magnetic thread can be detected by a single magnetic head regardless of orientation and size.

Disadvantages

Regardless of alignment, it is impossible to read encrypted data from the thread without the use of multiple heads since the direction of the data is perpendicular to the direction of travel of the document.

In the case of pattern recognition, it is also typical to use a large detector head which can incur high cost.

Examples of known scanning systems are described in US-A-5867589, US-A-5540425 and EP-A-0903701. These rely on multiple sensors or a flat bed scanner which are expensive and complex.

In accordance with the present invention, a method of detecting a characteristic of an article using a detector system a transport for transporting articles along a feed path; and a detector assembly including a characteristic sensor for sensing a characteristic of the articles, the characteristic sensor being mounted to a support to enable the sensor to be moved in a direction transverse to the feed path so as to be able to view laterally offset portions of an article comprises feeding an article to the detector system; moving the characteristic sensor transverse to the feed direction when the article is located at a position at which it is expected that the characteristic will be sensed; and monitoring output signals from the characteristic sensor; and is characterised in that movement of the article is stopped or moved more slowly than its initial feed speed while the characteristic sensor is moved.

With this invention, we make use of a movably mounted characteristic sensor which is moved when the article is stationary. This enables us to take advantage of short edge transportation systems but overcome the disadvantage of such systems when attempting to detect security threads.

In contrast to the prior art described above, in which an array of sensors is provided across the document path, the present invention utilizes a single characteristic sensor which outweighs the apparent disadvantage of stopping or slowing down the article while scanning takes place .

Furthermore, in the case of a banknote in which a security thread is located extending across the short edge dimension, the prior art again needs the array of sensors located across the full width of the document, with the note being fed by its long edge, in order to guarantee locating, and reading, the thread. In the present invention, if the note is fed by its short edge, again only one sensor is needed to read the thread. Moreover, if the system knows roughly where the thread is located, a reduced number of scans is then needed because the transport can be advanced quickly to the earliest expected position, then more slowly whilst the scanning sensor is detecting the thread, then accelerate again once it has been read.

The invention is also advantageous in the case of pattern recognition and the detection of other features such as infrared, ultraviolet, fluorescent characteristics and the like as it simplifies and thus reduces the high cost of the detector or sensor required.

There are two approaches to using a detector system according to the invention. In the first approach, the article is stopped to enable the sensing process to be undertaken while in the second approach detection is carried out while the article is moving more slowly than the speed at which it was delivered to the detector assembly.

In either case, the characteristic sensor can be moved either manually or automatically using a drive system. Where a drive system is utilized, the rate of traverse and hence the rate of scan can be adjusted to match the optimum scanning speed of the attached sensor (hence the optimum data gathering conditions) . Likewise, the automatic drive system speed can be programmed to match the requirements of the fitted sensor.

Conveniently, the support is mounted so as to enable the characteristic sensor to move at an acute angle relative to the feed path direction. This is particularly advantageous for use when attempting to detect a security thread which is typically arranged orthogonal to the long edge direction of the document being transported. In the case where the document is stopped prior to the sensing step, if the security thread is not aligned exactly with the starting point of the characteristic sensor then by moving the characteristic sensor at an acute angle relative to the feed path direction, it is likely that the security thread will be detected.

In some cases, the expected location of the security thread or other characteristic feature can be predicted by reference to the speed at which the article is fed by the transport. Preferably, however, a position sensor is provided for determining the position of an article along the feed path. This may typically be an optical sensor but could, in fact, be constituted by the characteristic sensor itself. In the case of detection of a magnetic security thread, this would be possible if the transport could be stopped almost immediately that the magnetic thread was detected so as to enable it to be scanned by the characteristic sensor. Alternatively, if the characteristic sensor was adapted to sense another type of characteristic such as an optical characteristic, then it could be used to sense the arrival of the leading edge of the article allowing time for the article to be positioned correctly relative to the sensor for subsequent scanning. The invention is applicable in a wide variety of fields as mentioned above but a particularly important application is that of document handling apparatus in which a controller is provided responsive to output signals from the characteristic sensor to control subsequent handling of the article. Examples of such apparatus include document sorting, dispensing and accepting apparatus, particularly for banknotes. In the simplest implementation, the controller may increment a count in response to the detection of the characteristic. In more sophisticated applications, either instead of or in addition to incrementing a count, the controller may cause an article to be sorted to a particular output location in response to the detection of the characteristic. The invention may be utilised with a wide variety of articles such as but is particularly suited for use with documents of value such as banknotes, vouchers, travellers cheques, bankers drafts and giro cheques.

Some examples of detector systems according to the present invention will now be described with reference to the accompanying drawings, in which :-

Figures 1A and IB are a side view and plan respectively of a detector system in which a document is stopped for the scanning process; Figure 2 is a plan view of a detector system in which a document is scanned while it moves through the system;

Figure 3 is a block diagram of the control components shown in Figure 1; and,

Figure 4 is a block diagram of document handling apparatus utilising the system of Figure 1.

The apparatus shown in Figure 1 comprises an input bezel 1 which optimises the human interface to the rest of the system and guides the document towards a transport pinch 3. Incorporated in the input bezel 1 is a document sensor 2, for example an opacity detector of conventional form. This can be used simply to detect the arrival of a document for future timing control of the transport or additionally to detect the feeding of multiple documents so as to flag this occurrence enabling the system to take appropriate action.

The transport pinch 3 comprises a number of sets of pinch rollers 4 mounted non-rotatably on a drive shaft 4a and a driven shaft 4b. These define the entrance to a transport 50 and accept a document supplied through the input bezel 1.

The transport 50 has an exit transport pinch 5 defined by pinch rollers 52 mounted respectively on a drive shaft 5a and a driven shaft 5b but they are capable of freewheeling in a forward direction by virtue of the presence of a freewheel clutch 6 mounted in a drive pulley 6a. The freewheel element is provided in order that there is a smooth transistion between the transport 50 and the next downstream transport system. However, the freewheel clutch is not essential.

The transport 50 further includes a motor 7 supported one of a pair of side plates 54 of the system and which drives a belt 9 via a drive pulley 8. The belt 9 is entrained around a drive pulley 9a non-rotatably mounted to the drive shaft 4a. The drive shaft 4a is also non- rotatably connected to a drive pulley 10 about which is entrained a belt 11. The belt 11 extends around a further drive pulley 11a non-rotatably connected to a drive shaft lib. The drive shaft lib carries pinch rollers lie which cooperate with pinch rollers lid on a driven shaft lie.

The drive shaft lib also carries a drive pulley 56 non-rotatably about which is entrained a drive belt 58 entrained around the drive pulley 6. The motor 7 can be operated in both directions so that in this way the transport 50 can be reversed. An alternative to a belt drive would be the use of a rack and pinion or a worm drive but a belt is preferable due to its lateral flexibility offering the scanning head the advantage of maintaining contact with a document surface and reducing the requirement for flexible guides under the document .

A timing disk or encoder 19 may be fitted to the transport (as shown) in order to optimise speed control.

Typically, guides will be provided to assist progress of the document along the transport 50 although these have not been shown in Figure 1 for reasons of clarity.

An optical sensor 12 is mounted towards the exit pinch

5 for sensing the arrival of a document security thread at a scanning area 13 and/or for sensing the leading edge of a document. This sensor can also act as an exit sensor by sensing the document's trailing edge.

A magnetic head 14 is mounted to a scanning belt 15 entrained around pulleys 15a, 15b, the belt 15 extending across a sufficient width of the transport 50 to enable the full width of a document to be scanned. The belt 15 is driven by a motor 18 via the pulley 15a.

The magnetic head 14 is suitably shaped or guided so that it can move smoothly across closely adjacent or contacting the surface of a document without any risk of "pick-up" or jamming and in this example is initially parked out of the document path awaiting a command to scan signed by a system controller (not shown in Figure 1) upon receiving data from the scanning sensor 12.

If the system uses the document leading edge as a trigger to initiate scanning, then in order to overcome tolerance variations there may be a requirement for multiple magnetic heads mounted serially or for a special wide head.

As explained above, the main problem in detecting a magnetic thread is one of consistently positioning the thread beneath the magnetic head 14. Since typically the position or tolerance of a thread with respect to the document on which it is carried is very open, using the document as a datum for thread positioning may place it beyond the width range of a standard magnetic head. The apparatus shown in Figure 1 can be implemented in a number of ways in order to overcome these problems.

In a first approach, the document is incremented by the transport 50 until its leading edge is sensed by the optical sensor 12. The document is then further indexed by an amount which has been predefined by the distance from the edge to the security feature (or thread) so as to position the thread nominally in the path of traverse of the magnetic head 14. The motor 18 is then activated to cause the magnetic head 14 to scan across the thread. Any deviation from the nominal position of the thread (if outside the width range of the head 14) can be dealt with by the use of either an extra wide magnetic head or by multiple overlapping heads.

In a second approach, the leading edge of the document is again sensed by the sensor 12 but in this case the document is further indexed by an amount defined by the minimum distance from the thread to the leading edge. The document is then scanned by the magnetic head 14 and if the thread is not detected, the document is indexed further and rescanned. This process is repeated until the thread is detected or the document is outside the positional tolerance band of the thread in which case the document will be perceived as counterfeit through the lack of a security thread.

In a third approach, the leading edge of the document does not serve as a datum. Instead, the magnetic head 14 itself serves a dual function, one of flagging the position of the thread and then one of scanning the information. In this example, the magnetic head 14 is initially positioned so that the thread can pass underneath it . The passage of a thread across the magnetic head 14 signals its presence to the control system and the transport is halted immediately (or within the detection range of the magnetic head) . With the document stationary under the magnetic head, the lateral motion of the head scans the thread.

The third approach is considered to be the most preferable since it incurs the least system cost and as the thread is directly detected can be universal for all thread positions provided that they are parallel with the line of scan of the head and within its traverse range. However, in some cases the use of the leading edge sensor is preferred so that the magnetic head 14 is not in the transport path initially.

Figure 3 illustrates a system controller 100 connected to the motors 7,18 for controlling operation of those motors and for receiving signals from the encoder 19,20, the sensor 12 and the magnetic head 14. Following scanning of the note by the magnetic head 14, the system controller 100 will determine whether or not the note is acceptable and generate a suitable output. Figure 4 illustrates the system of Figure 1 at 110 and as can be seen in Figure 4, documents are fed from the system 110 towards a diverter 115. The position of the diverter is controlled by the system controller 100 so as to feed documents in one of two directions. The decision will be made by the system controller 100 depending upon the outcome of the scan by the magnetic head 14. In other cases, however, the system controller may cause the overall transport of the document to stop if the document is found to be unacceptable or may simply flag its unacceptability via a display or the like.

Figure 2 illustrates a second form of system for detecting magnetic threads on documents without stopping the documents. As can be seen, the components of the system in Figure 2 are largely the same as those in the Figure 1 example and only the part of the transport 50' which differs from that shown in Figure 1 is shown in Figure 2. The difference is that the magnetic head 14 is arranged to scan across documents in a direction at an acute angle or diagonally with respect to the feed direction. In all other respects, the components of Figure 2 are the same as those shown in Figure 1 and they have been given the same reference numerals.

In operation, the scanning sensor 12 senses the arrival of the security thread at the scanning area 13 by monitoring the arrival of the leading edge of the document . The system controller 100 responds to the detection of the leading edge to activate the motor 18 at a suitable time such that the magnetic head 14 is scanned across the document. This will typically occur while the document is stationary but could also be done while the document is moving slowly while the head 14 is scanned to and fro as the document is being transported and will detect the passage of a magnetic thread (if correctly present) .

The angle at which the magnetic head 14 is driven across the transport is determined by resolving the relative transport speed to the optimum scanning speed. The optimum scanning speed is obtained by varying the scanning speed and/or transport speed to achieve the optimum scanning rate for the sensor mounted within the scanning head. As before, this mechanism is intended for short edge fed documents in which the thread is parallel to the short edge .

As mentioned above, the magnetic head 14 could be replaced by any other type of sensor such as an infra-red or ultraviolet sensor depending upon the characteristic which is to be sensed.

Claims

CLAIM

1. A method of detecting a characteristic of an article using a detector system; a transport for transporting articles along a feed path; and a detector assembly including a characteristic sensor for sensing a characteristic of the articles, the characteristic sensor being mounted to a support to enable the sensor to be moved in a direction transverse to the feed path so as to be able to view laterally offset portions of an article, the method comprising feeding an article to the detector system; moving the characteristic sensor transverse to the feed direction when the article is located at a position at which it is expected that the characteristic will be sensed; and monitoring output signals from the characteristic sensor, characterised in that movement of the article is stopped or moved more slowly than its initial feed speed while the characteristic sensor is moved.

2. A method according to claim 1, wherein the characteristic sensor is manually moved.

3. A method according to claim 1 or claim 2, further comprising monitoring the position of the article along the feed path and controlling the transport to stop when the article is positioned such that it is expected that the characteristic will be detected by the sensor.

4. A method according to claim 3, wherein the position of the article is monitored by monitoring for the leading edge of the article.

5. A method according to any of the preceding claims, wherein if the characteristic is not sensed, the method further comprises indexing the transport to move the article and then repeating the characteristic sensor movement .

6. A method according to any of the preceding claims, wherein the article comprises a security document such as a banknote .

7. A method according to claim 6, wherein the document carries a magnetically detectable feature such as a security thread.

8. A method according to claim 7, wherein the document carries a security thread defining a code .

9. A method according to any of the preceding claims, wherein the support is mounted so as to enable the characteristic sensor to move at an acute angle relative to the feed path direction.

10. A method according to any of the preceding claims, further comprising a position sensor for determining the position of an article along the feed path.

11. A method according to claim 10, wherein the position sensor is an optical sensor.

12. A method according to claim 10, wherein the position sensor is constituted by the characteristic sensor.

13. A method according to any of the preceding claims, wherein the sensor further comprises a control system for stopping the transport when an article is located at a position at which it is expected that the characteristic will be sensed by the characteristic sensor.

14. A method according to claim 13, wherein the control system is adapted to index the transport if the characteristic sensor is unable to detect a characteristic.

15. A method according to any of the preceding claims, wherein the characteristic sensor comprises one of a magnetic, visible, infra-red or ultraviolet sensor.

16. A method according to claim 15, wherein the characteristic sensor comprises a single magnetic head.