Bank Note Testing Apparatus

Abstract

A process and an apparatus for testing bank notes for their genuineness, particularly for automatic vending machines, wherein the bank note is illuminated from one side from a light source through a mask. The printed image on one side of the bank note is divided by the mask into several test fields. The reflected light from each test field is received by one of a plurality of large area photoelectric cells, which are so connected that departures from a given value are added together to form an error signal.

Description

This invention relates to a process or method for testing the genuineness of bank notes, particularly for automatic vending machines, and to a bank note testing apparatus using the process.

BACKGROUND OF THE INVENTION

Vending machines which are operated by coins have been known for a long time. The inserted coins are tested therein by test devices, for example in terms of diameter, thickness, weight or metal alloy, in order to separate genuine and false coins.

With increasingly high sale prices of goods sold by such machines or of travel tickets, and for purposes of universal application, the need arose of being able to use not only coins but also bank notes for the purchase. If a vending machine can be made to accept bank notes, then the range of wares or tickets can extend to units of higher value, and the choice of materials suitable for automatic sale can be substantially broadened.

If bank notes are to be accepted by automatic machines, then, in similar fashion to coin checking, these must be tested for genuineness. Bank notes are essentially printed pieces of paper; compared to coins they have wholly different recognition features, and as a result, require different testing methods.

It has already been suggested to test the printed image on bank notes for genuineness at several individually chosen places about of the size of a pencil lead cross section by photoelectric means by light transmitted through the bank note. However this does not always give satisfactory results since in the case of bank notes which have been much used, substantial differences between bank notes are present and difficulty arises due to the fact that the light transmission of bank note paper undergoes large variations. On careful comparison of a large number of bank notes of the same value, both differences of paper format and differences in the fitting of the various printing inks can be found of an order of size of about 2-3mm. On top of this there are color changes which can arise if bank notes are manufactured in printing series separated from one another in time.

One must therefore start with the fact that even new bank notes have no ideal test properties. Once these bank notes have been in circulation then, by virtue of this use, they become dirty, creased and are otherwise worn. At least 90 percent of the real bank notes in circulation should be adjudged as genuine by the test apparatus, i.e. accepted, and yet forgeries should be rejected with certainty.

If bank notes are illuminated from one side with light and on the other side there are arranged in irregular order a plurality of photocells, which measure the light values transmitted, which are each different according to the bank notes image printed on both sides thereon, then the defects of bank notes mentioned above, such as format and printed image deviations or spots, already give substantial differences from the expected value, which according to the adjusted error tolerance field would in many cases lead to non acceptance of the bank note by the testing apparatus, although it was genuine.

It is an object of the present invention to provide a bank note testing method and device in which the inherent defects in the bank notes have only little a very small effect on the measuring result in a photoelectric sensing system, but which nevertheless gives a high reliability for the genuineness testing.

SUBJECT MATTER OF THE PRESENT INVENTION

Briefly, the bank note is illuminated from one side from a light source through a mask, whereby the printed image on the bank note is divided by the mask into several test fields, the reflected light from each test field is evaluated to form an electrical measured value. The departures from the expected measured value are then added to give an error signal.

The apparatus comprises a light source, a mask for dividing the printed image on the bank note into a plurality of test fields. Value generators are associated with each test field and receive reflected light from the image on the bank note for the purpose of forming a measured value, the measured value generators being so connected that departures from a given value are added together to form an error signal, so that a high certainty of judgement can be obtained in respect of the bank notes to be tested, but wherein the insufficiences of bank notes only have a very small effect on the test result and on the other hand variations determined by the addition nevertheless give a very high certainty of the genuineness testing.

The invention will be better understood, and objects other than those set forth above will become apparent, when consideration is given to the following detailed description thereof.

The invention will be described by way of example, with reference to the accompanying drawings, wherein:

FIG. 1 is a view of a bank note, divided by a mask into four equally sized testing areas,

FIG. 2 is a view from the top of the bank note testing device according to the invention, in schematic illustration,

FIG. 3 is an electric circuit diagram of the testing device,

FIG. 4 is a detail of the electric circuit of a discriminator,

FIG. 5 is a side view of the apparatus, and

FIG. 6 is a front view of the apparatus shown in FIG. 5.

Referring to the drawings, a bank note 1 to be tested is divided by means of a mask or grate into four equally sized test areas a, b, c and d, as can be seen in FIG. 1. The central crossing dashed lines 2 show the normal folds present in used bank notes. These folds, as well as the two narrow edges of a bank note are more liable to damage and are covered over for the measurement by means of a mask 6 having the form of a frame or grid with crossed strips of about 6-10mm width. The thus remaining four surfaces a, b, c and d of the bank note image which are used for the measurement are shown hatched in FIG. 1 and together form a surface, which in comparison to the whole of the surface of the bank note amounts to at least 50 percent, preferably at least 75 percent, thereof. These surfaces a, b, c and d are used for one sided photoelectric testing by reflected light.

The photocells 10 used have a relatively large surface area, preferably of the type of silicon photo elements, which receive the light reflected from the bank note paper without optical aids such as lenses or the like, and which generate the measured value.

The bank note 1 to be tested arrives from above via a funnel 52 (FIGS. 4, 5) into the testing apparatus behind a glass window 7. By two electromagnets 49, the bank note 1 is pressed by a plate 48 against the receptor surface of the glass plate or window 7. Adjacent glass window 7 but on the other side from bank note 1 there is the mask 6 which bears thick walled, horizontal frame plates 3, 5, 8 (FIG. 1) and a vertical frame plate 15 of opaque plastics material, which separate the four test fields a, b, c and d of the bank note from one another. The center vertical frame plate 15 is provided on both sides with cavities in each of which in depressed position a photocell 10 or another light-sensitive organ lies. Thus this plate 15 of the mask 6 is provided in all with four photocells 10 which lie opposite one another in pairs and right-angled to the bank note 1 (FIG. 2). The photocells 10 are constructed as comparatively thin discs and are arranged in such a fashion that light beams 13, 14 coming from an electrical glow lamp 11 do not fall directly onto these photocells 10. Onto these photocells 10 which act as value generators there thus falls only the diffuse light reflected at an angle from the bank note fields a, b, c and d. In the beam of glow lamp 11, a filter glass 12 is provided which stops the infra-red portion of light so that the bank note 1 is really only illuminated with the visible part of the spectrum. The reflected light from the bank note which falls on the photocells 10 gives, according to the printed image and the printed colors, an electric signal which can be evaluated as a measured value.

As is evident from FIG. 3, to each of the photocells 10 belonging to bank notes fields a, b, c and d, an amplifier 18, 19, 20, 21 is connected. The outputs are processed in pairs by differentially measuring discriminators 25, 26, 27, 28, 29 and 30.

The outputs of these discriminators are again combined additively with one another, i.e. connected in parallel electrically, so that a relatively high number of logical results are obtained concerning the test result of the bank note, although in all only four fields are measured.

Thereby, since for the differential measurement always two photocells are combined together in pairs, there arises in total a combination of six connection pairs. Each connection pair is fed to a differentially working discriminator 25-30. Since the four photocell amplifiers 18-21 are each provided with a trim potentiometer, the amplifier outputs which are generated when an average bank note is laid in the testing device can be adjusted against a fixed reference voltage to a null value. The differential evaluation has the advantage that a regular use of the bank note or regular coloration changes will not be noted as an error for all the four fields. By this also, better stability is imparted to the device itself against external influences, such as ageing of the glow lamp 11 of or the photocells 10.

The outputs of the six discriminators 25-30 are connected together in parallel and this connection is fed across an adjustable resistance 35, an amplifier stage 33 and a switching stage 34. This switching stage 34 can either be a relay, an electromagnet or a transistor for accepting of rejecting a bank note after testing. The sensitivity of acceptance of the device can be adjusted by altering the variable resistance 35 within fixed limits, since the differential devices work as current generators and give a current proportional in size to the faults of the bank note present, which is translated to a voltage by resistance 35.

If this voltage rises to a given or predetermined value then the threshold of the amplifier is exceeded and this then operates the switching stage 34 which leads by further means the switch tongue 37 to the acceptance or rejection of the bank notes submitted. In the simplest case even the difference between a single pair of photocells 10 can be so great that the current is sufficient to make the device respond and to reject the bank note. It can however also be that several pairs each register relatively small deviations and this results in the individual error currents being relatively small. These partial currents add, however, in their path through resistance 35 to a height of the threshold voltage which likewise leads to rejection of the bank note. Since each of the bank note fields, a, b, c and d is combined or compared with each of the others, it is possible to stop attempts at cheating with substantial security; on the other hand at least 90 percent of the genuine bank notes in circulation of the chosen value will be accepted by the testing device.

In FIG. 4 the components used in a discriminator and the corresponding circuit are described in more detail. Only a single discriminator 25 having a pair of photocells connected thereto with the circuit means as illustrated will be described; the other discriminators 26-30 are likewise constructed.

As is already evident from FIG. 3, each of the photocells 10 is connected to an amplifier 18-21. One amplifier 18 is connected via a lead 38 with the base of a transistor 39. The collector of this transistor is connected via a lead 40 to the lead 32 common to all discriminators. The emitter of this transistor 39 is connected via a lead 42 to the output 23 of the other amplifier 19, with the interposition of a resistance 43. This amplifier output 23 of the second amplifier 19 is connected to the base of a second transistor 44, the collector of which is connected via a lead 45 with the lead 32. The emitter of this second transistor 44 is connected via a lead 46 in which is located a resistance 47 to the first amplifier output 38.

If a bank note 1 is pushed by hand in direction of arrow D into the funnel 52 (FIGS. 5, 6), it falls by gravity along a vertical channel 54 into the testing apparatus behind a glass window 7. The channel 54 is laterally limited by guide plates 69 and at the bottom by a stop member 59. A pair of upper and a lower light barriers 55, 56 and 57 are arranged in the path of motion of the bank note 1, with the effect that the two electromagnets 49 are energized if the light beams of the light barriers are interrupted. Each of the electromagnets 49 -- which are acting parallel -- are connected by rod 50 with a pressure plate 48 so that the bank note 1 is pressed against the glass window 7 after moving the pressure plate 18 in direction of arrow C. The bank note 1 pushes with the lower narrow edge 16 against the stop member 59 which is a part of a rocker or switch tongue 58 pivotally supported by a horizontal pin 60. This switch tongue 58 is connected by a push rod 61 with two electromagnets 62, 63 acting in opposite direction each other. Depending on the result of the testing operation of the testing device described, the switching stage 64 acts in such manner that either electromagnet 62 or electromagnet 63 is energized. If electromagnet 62 is energized the switch tongue is pivoted in direction of arrow A and the bank note 1 is falling by gravity along a sheet metal guide 67 into a magazine or cashbox 65 arranged inside the apparatus. If one the other hand the electromagnet 63 is energized, the switch tongue 58 is swivelled in direction of arrow B if the bank note 1 is to be rejected. In this case the bank note 1 is falling into the return channel 64 after the pressure plate 48 has released the bank note 1.

While there is shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practised within the scope of the following claims.

Claims

What I claim is:

1. A Bank note testing apparatus comprising a light source (11);

means (7, 48) holding the Bank note in a predetermined plane;

masking means (6) covering a minor portion of the illuminated surface area of the Bank note and dividing the Bank note into a plurality of test fields, said test fields comprising at least 50 percent of the illuminated surface area of the Bank note, said masking means including opaque, sheet-like elements (3, 5, 8, 15) projecting from the plane of the Bank note in the direction towards the light source;

a plurality of large area-type photo-sensitive means (10) having photo-sensitive surfaces located at an angle with respect to the surface plane of the Bank note and to receive reflected light from the test fields of the Bank note, at least one each photo-sensitive means being associated with a test field and responsive, selectively, to reflected light therefrom, said sheet-like elements shielding the photo-sensitive means with respect to reflected light from adjacent fields;

and logic circuit means (25-30) logically interconnecting the output from any one of all of said photo-sensitive means with the output from any other one of the photo-sensitive means to provide a composite output signal representative of predetermined logic interrelationship of light values reflected from the test fields of the Bank notes.

2. Apparatus according to claim 1 wherein the photo-sensitive means are located at essentially right angles with respect to the plane of the Bank note.

3. Apparatus according to claim 1 wherein the masking means extends essentially perpendicular from the plane of the Bank note and the photo-sensitive means are located parallel to the masking means.

4. Apparatus according to claim 3 wherein the photo-sensitive means are located adjacent to and secured to the masking means.

5. Apparatus according to claim 1 wherein the masking means are arranged to cover the normal fold regions of the Bank note.

6. Apparatus according to claim 1 wherein the masking means are arranged to cover at least some of the edges of the Bank note.

7. Apparatus according to claim 1 wherein the light source comprises a source which has essentially no linear extent transverse to the sheet-like elements of the masking means so that said masking means will have shaded sides;

and wherein the area-type photo-sensitive means are located on said shaded sides.

8. Apparatus according to claim 1 wherein the length of the photo-electric means is approximately that of an associated test field.

9. Apparatus according to claim 1 wherein the logic circuit means comprises amplifier means (18-21) connected to each said light sensitive means (10);

a group of discriminator means (25-30), the output from each amplifier means being connected to selected ones of said discriminator means of said group to compare the output of any one amplifier means with that from any other amplifier means to derive said composite output signal.

10. Apparatus according to claim 9 wherein the outputs of the discriminator means are connected in parallel, said parallel connection having said composite output signal appear thereon;

a single variable resistance to set a predetermined level;

a second amplifier (33) and a switching stage (34) connected to said second amplifier, and means connecting the parallel connected discriminators to said single variable resistor (35) and the second amplifier, the output from said amplifier being connected to and controlling the operation of said switching stage (34).

11. Apparatus according to claim 9 wherein each discriminator (25-30) comprises two transistors (39, 44) and two resistors (42, 47), the base of any one transistor being connected to the output of one amplifier (18-21) and the emitter of said one transistor being connected over one of said two resistors to the output of another one of said amplifiers.

12. Apparatus according to claim 1 wherein the test field comprises about at least 75 percent of one surface of the Bank note.

13. A method of testing Bank notes for genuineness comprising the steps of

illuminating the Bank note from one side;

dividing the Bank note into a plurality of test fields which comprise, overall, at least 50 percent of the plane area of the Bank note, by masking strip-like portions of said Bank note, at least one of said strip-like portions dividing the Bank note in half to cover expected fold lines in used Bank notes;

evaluating the reflected light from each test field to form an electrical measured value;

and comparing said electrical measured values from any one of all said test fields with electrical measured values of any other one of said said other test fields, and deriving a composite output signal.