WO2002024561A1

WO2002024561A1 - Document handling apparatus

Info

Publication number: WO2002024561A1
Application number: PCT/GB2001/003562
Authority: WO
Inventors: Anthony Philip Thompson
Original assignee: De la Rue International Ltd
Current assignee: De la Rue International Ltd
Priority date: 2000-09-21
Filing date: 2001-08-07
Publication date: 2002-03-28
Anticipated expiration: 2003-03-21
Also published as: GB0023223D0; AU2001276543A1

Abstract

Document handling apparatus comprises a transport system (1) for transporting documents along a transport path (4). A document detection system has at least two detector arrangements (6, 7), each detector arrangement comprising a linear array (9) of radiation sources or radiation detectors, and at least one radiation detector (10) or radiation source respectively. The sources and detectors (9, 10) are located so that radiation emitted by a radiation source is detected by a corresponding detector after being transmitted through a document on the transport path (4), the two detector arrangements being spaced apart in a direction transverse to the transport direction. A control system (11) selectively controls each detector arrangement to detect different width radiation beams.

Description

DOCUMENT HANDLING APPARATUS

The invention relates to document handling apparatus, for example document sorting, dispensing or accepting apparatus .

It is a common requirement in document handling apparatus to ensure that single documents only are transported and multiple documents or so-called "doubles" are detected. It is also a common requirement, particularly in the case of banknote handling equipment, to provide means for determining the overall length of a document in the transport direction so as to enable the detection of half-length documents and strings of documents . Two technologies have been developed for detecting doubles. In mechanical arrangements, the deflection of a feeler or roller is monitored but this has the drawback that jamming can occur under some circumstances.

In an optical approach, the attenuation of light transmitted through the document is monitored and a double fed document is sensed when the attenuation exceeds a predetermined threshold.

The problem with conventional, optical arrangements is that the degree of attenuation can vary significantly from document to document, particularly where the documents carry varied printing or are soiled (as in the case of banknotes) making it difficult to set an acceptable threshold which accurately detects doubles without rejecting single documents. It is also a common requirement to detect the location of a document being fed along a transport path and this is typically achieved by detecting the presence of the leading edge of the document. This requires the use of a narrow radiation beam. In accordance with the present invention, document handling apparatus comprises a transport system for transporting documents along a transport path, and a document detection system having at least two detector arrangements, each detector arrangement comprising a linear array of radiation sources or radiation detectors, and at least one radiation detector or radiation source respectively, the sources and detectors being located so that radiation emitted by a radiation source is detected by a corresponding detector after being transmitted through a document on the transport path, the two detector arrangements being spaced apart in a direction transverse to the transport direction; and a control system for selectively controlling each detector arrangement to detect different width radiation beams.

With this new invention, we provide two detector arrangements, each arrangement being controllable to detect different width radiation beams. This enables each detector arrangement to be set initially to detect relatively narrow width radiation so as to detect a leading edge of the document and then to be set to detect relatively wide width radiation transmitted through a relatively wide portion of a document for the purpose of detecting doubles. By using a wide width beam area in the second stage and then averaging over a number of samples within the wider width portion of the document, the discrepancies caused by significant and localised document density variations, pattern variations, metal threads, holes and the like are removed. However, the use of a relatively narrow width allows the leading edge of a document to be accurately detected. Further, by providing at least two such detector arrangements, skew can also be determined and thus an accurate determination of document length can be made.

Typically, the linear arrays are rectilinear and in that case, the arrays preferably extend in a direction substantially orthogonal to the transport direction. However, other forms of linear array such as curved linear arrays are possible while the linear array may form part of a larger two-dimensional array. Preferably, the detector arrangements are substantially symmetrically located about a centre line of the transport path. This assists in downstream signal processing when handling a skew fed document . Conveniently, each detector arrangement has the same construction although this is not essential. Thus, in a preferred approach, each detector arrangement comprises a linear array of radiation sources and a single or more than one radiation detector, the sources being controllable so that one or a few of the sources in the linear array are activated to generate the relatively narrow width beam or all the sources are illuminated to generated the relatively wide beam.

Of course, the arrangements may comprise a linear array of detectors and a single source, the detectors being selectively controllable in a similar way to the sources of the previous example .

Preferably, the sources of the detector arrangements are located on the same side of the transport path although in some cases the source (s) of one detector arrangement may be located on the same side of the transport path as the detector (s) of the other detector arrangement.

Typically, the radiation will be visible light although radiation outside the visible wavelength range, for example in the infrared or ultraviolet, could also be used.

As mentioned above, the invention is particularly suited for use with banknote handling apparatus such as banknote dispensers, sorters and acceptors but is equally applicable to other types of document handling apparatus.

An example of a banknote transport apparatus according to the invention will now be described with reference to the accompanying drawings, in which: -

Figure 1 is a schematic, side view of the apparatus; Figure 2 is a block diagram of part of the detection system; and, Figure 3 is a plan view showing the location of the radiation source arrays.

The apparatus shown in Figure 1 comprises a transport system 1 illustrated diagrammatically by a pair of feed belts 2,3 which are operated to transport documents along a feed path 4 in the direction of an arrow 5. Of course, other feed arrangements could be used such as vacuum based systems .

A pair of detector arrangements 6,7 (Figure 3) are located on either side of a centre line 8 of the feed path 4, one of the detector arrangements 6 being shown in Figure 1. The two detector arrangements 6,7 have an identical construction so the detector arrangement 6 will be described. The detector arrangement 6 comprises a rectilinear array of LEDs 9 positioned above the transport path 4 and a single photodiode 10 located below the transport path 4 in alignment with the central LED of the array 9.

The array 9 and the photodiode 10 are connected to a control system 11 which monitors the output of the photodiode 10 and controls a solenoid 12 accordingly. The solenoid 12 is coupled to a diverter 13 which can be moved between its solid line position shown in Figure 1 where banknotes are fed to a dispense outlet 14 and the position shown in dashed lines in which the banknotes are fed to a cull pocket 15.

The control system 11 is shown in more detail in Figure 2. The control system comprises a microprocessor 16 connected to each detector arrangement 6,7. The connections to the detector arrangement 6 are shown in more detail. Thus, the microprocessor 16 is connected to a set of LED drivers 17 which in turn are connected to individual LEDs in the array 9. The photodiode 10 is connected to an analogue-to-digital converter 19 whose output is connected to an input of the microprocessor 16. Similar connections are made to the components of the detector arrangement 7. In operation, the microprocessor 16 activates the central LED only of each array 9, indicated at A in Figure

3. This results in a narrow radiation beam being generated which is detected by the corresponding photodiodes 10. When the leading edge of a banknote 20 cuts one of these beams, the radiation reaching the photodiode will be significantly attenuated and this will be detected by the microprocessor 16 as indicating the arrival of the leading edge 21 of the banknote. As will be apparent from Figure 3, if the banknote 20 is skew fed (as shown) then the leading edge will be detected at different times by the two detector arrangements 6,7 and the difference in timing will provide an indication of the degree of skew assuming the note speed is known.

Once the detector arrangement has detected the leading edge, the microprocessor 16 will turn on all the LEDs in the appropriate array 9 so that a relatively wide strip of the banknote 20 is illuminated. To a first order approximation, the level of transmission through the banknote is an inverse log function of the thickness of the paper and this is monitored by the microprocessor 16 by sampling the output from the photodiodes 10. These samples can then be averaged and translated to a thickness value using a look-up table based on the inverse log function mentioned above. If the determined thickness exceeds a predetermined threshold corresponding to a single note, a double is indicated and the microprocessor 16 will activate the solenoid 12 so that the diverter 13 moves to its dashed line position and the doubles are supplied to the cull pocket 15.

When working with known single denomination currency, the full arrays can be turned on some time after the leading edge is detected and turned off before the trailing edge of the note is reached, thus removing the possibility of saturation degrading the average density reading. The pair of single LED sources A can then be used to detect the overall length of the note. This provides an additional check on the validity of the note being fed as mentioned above .

Although two detector arrangements have been described, more than two could be used. Furthermore, each array could form part of a single much larger array.

Claims

1. Document handling apparatus comprising a transport system for transporting documents along a transport path, and a document detection system having at least two detector arrangements, each detector arrangement comprising a linear array of radiation sources or radiation detectors, and at least one radiation detector or radiation source respectively, the sources and detectors being located so that radiation emitted by a radiation source is detected by a corresponding detector after being transmitted through a document on the transport path, the two detector arrangements being spaced apart in a direction transverse to the transport direction; and a control system for selectively controlling each detector arrangement to detect different width radiation beams.

2. Apparatus according to claim 1, wherein the linear arrays are rectilinear.

3. Apparatus according to claim 2, wherein the linear arrays extend in a direction substantially orthogonal to the transport direction.

4. Apparatus according to any of the preceding claims, wherein the detector arrangements are substantially symmetrically located about a centre line of the transport path.

5. Apparatus according to any of the preceding claims, wherein the detector arrangements have the same construction.

6. Apparatus according to any of the preceding claims, wherein the sources of the detector arrangements are located on the same side of the transport path.

7. Apparatus according to any of the preceding claims, wherein the sources comprise light emitting diodes.

8. Apparatus according to any of the preceding claims, wherein the detectors comprise photodiodes.

9. Banknote handling apparatus according to any of the preceding claims.