GB2132756A

GB2132756A - Paper sheet discriminating apparatus

Info

Publication number: GB2132756A
Application number: GB08333413A
Authority: GB
Inventors: Yoshinobu Oka
Original assignee: Laurel Bank Machine Co Ltd
Current assignee: Laurel Bank Machine Co Ltd
Priority date: 1982-12-17
Filing date: 1983-12-15
Publication date: 1984-07-11
Also published as: JPS59111589A; DE3345251A1; JPH0236996B2; GB8333413D0

Abstract

In a paper sheet discriminating apparatus, an array of photosensitive diodes, ph1 to phn, is arranged perpendicular to a transfer path and adapted to be friction engaged with bank notes during their passage. A predetermined weight is given to the output of each photosensitive element by respective operational amplifiers 5-1 to 5-n. The weighted outputs of the operational amplifiers are summed at 6 to provide a basis for discrimination eg to detect soiling, holes or tears in bank notes, or whether the notes are genuine <IMAGE>

Description

SPECIFICATION Paper sheet discriminating apparatus This invention relates to a paper sheet discriminating apparatus which optically detects characteristics such as printed patterns of transferred paper sheets.

Paper sheet discriminating apparatuses for discriminating whether, for example, bank notes are genuine or counterfeit and for discriminating the kinds of bank notes have been widely used. As a method of discrimination, it has been popular to illuminate a moving bank note with light, detect the light reflected from or transmitted through the bank note, and discriminate the detected printed pattern.

However, in such conventional bank note discriminating apparatus, the transmitted or reflected light is locally detected by using one or a number of photosensitive elements. Because of this, detection errors occur when the moving bank notes are offset in position. In order to avoid offset of the bank notes, it is necessary to provide guide plates or to selectively switch photosensitive elements. However, in the case where guide plates are provided, it is difficult for the user to insert the bank notes into the bank note discriminating apparatus. In case where photosensitive elements are switched the construction of the bank note discriminating apparatus becomes complex.On the other hand, there is a method in which a partial image of the moving bank note is focused by optical lenses on the photosensitive elements in an appropriately blurred manner so as to eiiminate the effects of position offset of the bank note or deviation of the moving bank notes. In such a method, however, the optical system tends to be affected by dust etc., and it is difficult to make the apparatus compact since the distance between the optical lenses and the photosensitive elements becomes long.

According to one aspect of the present invention, there is provided a paper sheet discriminating apparatus in which moving sheets such as bank notes are illuminated and are discriminated by the transmitted light thus obtained, which comprises a transfer path for the sheets; an array of photosensitive elements for receiving the transmitted light and arranged transverse to the transfer path; weight setting means for providing a predetermined weight to the output signal of each photosensitive element; and total detecting means for totalling the output signals of the weight setting means.

The present invention also provides apparatus for paper sheets, comprising a transfer path for the sheets, a plurality of sensors arranged to sense a characteristic of the sheet in areas disposed along a line extending transversely across the transfer path, means for preferentially weighting the outputs of the sensors and means responsive to a sum of the weighted outputs to provide a basis for discrimination.

These and other objects as well as the advantages of the present invention will be clear from the following description of a preferred embodiment of the present invention with reference to the accompanying drawings, wherein: Figure 1 is a top plan view showing a main portion of the bank note discriminating apparatus according to one embodiment of the invention; Figure 2 is a diagrammatic side view showing the relationship in position between an array of photodiodes and a light source; Figure 3 is a diagram showing an electrical circuit according to the embodiment; Figure 4a is a view showing positions of photodiodes phl-phn arranged in the width direction of a transferring path; and Figure 4b is a view showing weights corresponding to photodiodes phl-phn.

In Fig. 1, bank notes are transferred along a transfer path from left to right in the drawing.

A photodiode array (hereinafter referred to as an "array") 2 comprises a plurality of photodiodes phl-phn arranged linearly. The array has the same length as the width of the transfer path 1 and is disposed to be perpendicular to the transfer path 1. Fig. 2 diagrammatically shows the relationship in position among the array 2, a bank note 3 and a light source 4. As shown in Fig. 2, light from the light source 4 is received by the array 2 after transmitting through the bank note 3, which is adapted to be transferred over the upper surface of the array 3. Furthermore, the light source 4 is adapted to uniformly illuminate the bank note 3.

The Fig. 3 shows an electrical circuit according to the embodiment.

In Fig. 3, operational amplifiers 5-1 to 5-n have their inversion input terminals connected to photodiodes phl to phn at their anodes with the cathodes of the photodiodes being grounded to earth. The inversion input terminals of the operational amplifiers are also connected to the output terminals thereof through resistors ral to ran. The non-inversion input terminals of the operational amplifiers are grounded to earth. In this case, the output voltages V, to V, of the operational amplifiers 5-1 to 5-n are represented by the following formula: Vi = - li.rai . (1) wherein 1, to In are photocurrents output from photodiodes phl to phn, and i = 1, 2... n.

The voltages V1 to V, are applied to the inversion input terminal of an operational amplifier 6 through resistors rbl to rbn. The operational amplifier 6 has its non-inversion input terminal grounded to earth and its inver sion input terminal connected to its output terminal through a resistor rc. The output terminal of the operational amplifier is connected to a terminal 7. The output voltage V0 of the operational amplifier 6 is represented by the following formula:

In the embodiment, output signals Ii to I, (photocurrents) of the photodiodes phl to phn are given weights, for example, as shown in Figs. 4a and 4b.Fig. 4a shows the positions in which the photodiodes ph1 to phn are arranged in the width direction of the transfer path 1 and Fig. 4 shows weights corresponding to position of the photodiodes ph1 to phn shown in Fig. 4a. As shown in Figs. 4a and 4b, the weights near the center of the transfer path in the width direction are made large and the weights gradually become smaller from center of transfer path towards the opposite sides thereof. The setting of the weights can be made by properly setting the values of the resistors ral to ran or the resistors rbl to rbn, as is clear from the formula (2) and Fig. 3.

In the case where the weights at the center of the transfer path are set to be larger than those at the opposite ends has only a slight effect on the output voltage V0 since the weights given to the photodiodes at the opposite sides are small even when the bank notes being transferred vary in position in the width direction. For this reason the output voltage V0 varies very little as a result of position offset and the position offset of the bank note can be substantially neglected. Furthermore,in the ease where a piece is torn out of the bank note at the side, the fluctuation in the output voltage V0 caused by this missing piece is similarly very small.Consequently, the output voltage V0 is not affected by the status of transfer of the bank notes and, therefore, is exactly determined by the printed pattern of the bank notes.

Moreover, in the embodiment, since the bank notes are transferred on the array 2 in friction relationship therewith as shown in Fig.

2, the array 2 (that is, the photodiodes phl and phn) are self-cleaned by the bank notes 3 and, therefore are not affected by dust, etc.

whereby they are always able to provide precise detection.

Furthermore, since the weighted pattern in the embodiment (Fig. 4b) can be optionally varied by changing the values of the resistors ral to ran or rbl or rb2. For example, in a case where it is desired to detect any hole in the bank note, the photodiodes corresponding to the portion of the bank note which tends to develop a hole easily are greatly weighted so that emphasis can be put on hole detection.

Consequently holes can be detected easily. In case where dirt on the bank notes is desired to be detected, the photodiodes disposed on the opposite sides of the transfer path 1 are weighted greatly. This is because the unprinted opposite sides of the bank notes are white, meaning that if emphasis is put on the light transmitted through these portions, the dirt on the bank notes can be detected with priority.

Moreover, the arrangement of weights in the embodiment is also applicable to a paper sheet discriminating apparatus which utilizes magnetic sensors.

It will be undestood that the array of sensors may be arranged either directly or effectively transverse the transfer path.

Claims

1. A discriminating apparatus in which moving sheets are illuminated and are discriminated by the transmitted light thus obtained, which comprises: a transfer path for the sheets; an array of photosensitive elements for receiving the transmitted light and arranged transverse to the transfer path; weight setting means for providing a predetermined weight to the output signal of each photosensitive element; and total detecting means for totaling the output signals of the weight setting means.

2. An apparatus as set forth in claim 1, wherein each photosensitive element comprises a photodiode.

3. An apparatus as set forth in claims 1 or 2, wherein said array of photosensitive elements is arranged so that the bank notes are transferred on said array in friction relationship therewith.

4. An apparatus as set forth in any previous claim wherein said weight setting means comprises an operational amplifier having one of its input terminals connected to said photosensitive element and a resistor connected between its input and output terminals.

5. An apparatus as set forth in any previous claim wherein said total detecting means comprises another operational amplifier having one of its input terminals connected to the outputs of the operational amplifiers as weight setting means.

6. A discriminating apparatus for paper sheets, comprising a transfer path for the sheets, a plurality of sensors arranged to sense a characteristic of the sheet in areas disposed along a line extending transversely across the transfer path, means for preferentially weighting the outputs of the sensors and means responsive to a sum of the weighted outputs to provide a basis for discrimination.