EP1065631B1 - Method and device for reading record carrier shaped like a sheet - Google Patents

Abstract

A transmitter (3) is placed below a recording medium (1) like a bank note. A reading station (2) tests transmission from the bank note. The transmitter consists of an illuminating device (5) and an illuminating slit diaphragm lens (6). A receiver (4) consists of a measuring sensor (7) and a sensor lens (8) connected in series. The bank note is passed between the transmitter and the receiver. An illuminated column of a specific width shows on the bank note.

Description

The present invention relates to a method and an apparatus for reading sheet-shaped recording medium during a relative movement relative to a reading station, which at least one transmitter for sequentially emitting at least two signals of different signal type, a common receiver for the different signal types for detecting these modulated by the record carrier signals and has an evaluation unit for the detected signals. This reading station detects at any time on the recording medium a "measuring surface" with a certain length in the direction of relative movement. Due to the relative movement of a clockwise scanning of the recording medium per clock a "raster element" of the recording medium is detected, which is greater than the measuring surface of the reading station. The size of the raster element increases with the relative speed and the duration of a signal emission ("signal clock").

Such methods or devices are used, for example, to determine the currency and the value of banknotes and to check their authenticity or validity. In addition, of course, a use for reading and checking any other record carriers, such as certificates, ID cards, etc. possible.

A corresponding apparatus for reading and verifying the authenticity of banknotes is in EP 0 537 513 A1 described. In this case, the banknotes are guided past a reading station, which consists of several transmitters for emitting light of different colors or of infrared signals and a common receiver. During the relative movement the banknote opposite the reading station, the different signals are emitted sequentially on the banknote. The receiver intercepts the signal reflected by the banknote or transmitted by the banknote and consequently modulated by the banknote. This signal is then evaluated.

By means of the different transmitters and the common detector several physical properties of the banknote are checked. For this purpose, the signals are emitted from the individual transmitters one after the other in a sequence and at the same time the banknote continues in its relative movement. This inevitably creates gaps in terms of the different images resulting for each signal type. These gaps are disadvantageous if structures occur on the recording medium that are of the same order of magnitude as the gaps. Repeated measurements may lead to quite large variations in the measured values.

In the GB-A-2 107 911 a bank note tester is described, which scans the passing banknote only in three, transversely to the direction of movement adjacent short sections with different types of signals. Here, multiple oversampling is performed on each section. This results in a very large amount of measured data and a slow conveying speed in relation to the sampling frequency. In addition, only certain, strip-shaped areas of the banknote surface are scanned in this way.

The invention has for its object to provide a method and an apparatus in which a full-surface scanning of the recording medium with respect to at least two physical properties is possible at the largest possible conveying speed.

This object is achieved by a method and by a device according to the independent claims.

According to the invention in this method or the device by a suitable design of the transmitter and / or receiver geometry of the reading station and by an appropriate choice of the relative speed and the cycle times ensured that the length of the detected by the reading station measuring surface for each of the signal types exactly Path length corresponds to the record carrier moves from the beginning of the emission in one signal type until the beginning of the next radiation in the same signal type ("period"). The cycle times are influenced by the length of the individual signal clocks of the different signal types as well as by the intervals of the signal clocks to each other. In other words, the geometric parameters of the reading station and the time parameters of the sampling are selected so that the length of the detected by the reading station measuring surface exactly corresponds to the spatial distance of the beginning or end of two signal clocks of the same signal type at successive signal clocks of different signal type. The spatial distance of two signal clocks is thus determined by the time interval of the clocks, i. the duration of a period multiplied by the relative velocity. In this way, occurrence of gaps is avoided.

Since the banknote continues to move during a signal clock, the measuring area detected by the reading station shifts relatively over the record carrier during the signal clock. It is therefore also scanned in this process during the clock, a raster element on the recording medium, which is longer in the direction of movement than the detected by the reading station measuring surface. This results in an overlap of the sampled raster elements, ie a partial double sampling.

However, because of the particularly selected geometry and time parameters, the double-scanned areas are only the edge areas of the raster elements which "run out" or fall into the measurement area during one cycle from the measurement area detected by the read station and which therefore are not be detected by the reading station over the entire cycle time, as is the case with the other areas of the raster element. This "underrepresentation" of the edge regions within a signal clock is exactly compensated by the double sampling in two successive signal clocks. Consequently, since the areas on the record carrier are completely detected with high read reliability without being read multiple times, on the one hand a high throughput is possible and on the other hand the processing and storage effort for the measurement data is relatively low.

The transmitter may, for example, be a transmitter with different illumination systems which differ in wavelength, that is, which emit light of different colors or infrared signals. Preferably, at least one of the signals is an infrared signal and at least one further signal is a light signal of a specific wavelength in the visible range.

In an alternative preferred embodiment, the sampling is performed at least with a bright field signal and a dark field signal. However, there are also other distinguishing features, such as the polarization of the light possible.

Furthermore, it is advantageous if the transmitter or the receiver are formed so that the grid element extends in a line across the relative relative movement over the entire recording medium. This can, for example, by a strip-shaped transmitter in the form of a lighting device be realized with a slit, and a correspondingly arranged strip-shaped CCD receiver or other transducer with a corresponding upstream optics, such as a rod lens. With such a system, the entire surface of the recording medium can be detected and read easily and quickly.

Fig. 1

eine schematische Darstellung der Vorrichtung (mit nur einem Sender),

Fig.2a

die Lage des Beleuchtungsspalts (Beleuchtungsintensität 1 = 100%) auf dem Aufzeichnungsträger zu Beginn eines Signaltaktes,

Fig.2b

die Lage des Beleuchtungsspalts gemäß Fig. 2a auf dem Aufzeichnungsträger zum Ende des Signaltaktes,

Fig. 3

die Lage zweier aufeinanderfolgender in einer Signalart abgetasteten Rasterelemente mit der innerhalb des Signaltaktes bezüglich der jeweiligen Orte im Rasterelement vorliegenden Dosisverteilung auf dem Aufzeichnungsträger,

Fig. 4

eine Darstellung einer zeitlichen Abfolge und Dauer von Signaltakten dreier verschiedener Signalarten (oberer Teil) mit der zugehörigen Lage und der örtlichen Dosisverteilung der einzelnen Rasterelemente jeder Signalart auf dem Aufzeichnungsträger (unterer Teil), und

Fig. 5

eine schematische Darstellung der Lage und Erstreckung von Meßflächen (Pixeln) unterschiedlicher Signalart auf einem Aufzeichnungsträger (zur Verdeutlichung sind nur zwei Meßflächen der einen Signalart dargestellt).

The method and the device according to the invention are explained in more detail below with reference to an embodiment with reference to the accompanying drawings. Show it:

Fig. 1

a schematic representation of the device (with only one transmitter),

2a

the position of the illumination gap (illumination intensity 1 = 100%) on the recording medium at the beginning of a signal cycle,

2b

the position of the lighting gap according to Fig. 2a on the record carrier at the end of the signal clock,

Fig. 3

the position of two successive raster elements scanned in a signal type with the dose distribution present on the record carrier within the signal clock with respect to the respective locations in the raster element,

Fig. 4

a representation of a temporal sequence and duration of signal clocks of three different signal types (upper part) with the associated position and the local dose distribution of the individual raster elements of each signal type on the recording medium (lower part), and

Fig. 5

a schematic representation of the position and extent of measuring surfaces (pixels) of different signal type on a recording medium (for clarity, only two measuring surfaces of a signal type are shown).

FIG. 1 shows a schematic representation of a reading station 2, wherein for the sake of simplicity, only one transmitter 3 is shown, which is located below the recording medium 1, here a banknote 1. At this reading station 2, the transmission of the banknote 1 is checked.

The transmitter 3 consists of a lighting device 5 and an illumination optical unit 6 in the form of a slit diaphragm. The receiver 4 consists of a transducer 7 and an upstream pickup optics 8, here a rod lens.

Between the transmitter 3 and the receiver 4, the banknote 1 is passed in the transport direction R. By appropriate selection and arrangement of the illumination device 5, the illumination optics 6, the pickup optics 8 and the transducer 7 results in a specific lighting characteristic on the banknote 1 with an illumination gap of a certain width. This gap width corresponds exactly to the length s _B of the measured surface detected by the reading station 2 during a specific time in the direction of movement R.

As in the FIGS. 2a and 2b is within the illumination gap, ie within the measuring surface, approximately an illumination intensity 1 of 100% before, whereas outside the illumination gap, the illumination intensity 1 is almost zero. Of course, in reality, in general, the boundaries are not as sharp as shown in the figures.

Furthermore, the show FIGS. 2a and 2b the changing position of the measuring surface on the banknote 1 under the movement along the transporting direction R. Fig. 2a shows the position at the beginning of an exposure time with a certain signal, ie at the beginning of a signal clock, and Fig. 2b at the end of this exposure time, ie at the end of the bar. During this signal clock, the banknote 1 has been moved at a constant relative speed exactly by the distance l ₁ in the transport direction R. As can be seen from the figures, the points A and D on the banknote 1 are outside the measuring area during the entire exposure time. By contrast, points B and C are within the measurement area during the entire exposure time. The points in the range between B and C therefore contribute maximally to the measured value. The points between A and B and between C and D, however, contribute only partially to the measured value, since they push into the measuring surface during the exposure time or move out of the measuring surface.

Overall, a measured value of a particular signal clock contains information from all points on banknote 1 between points A and D. The distance between A and D is therefore the extent of the scanned raster element in the direction of movement. The contribution of the respective points A to D to the measured value corresponds to dose P, which is determined by the intensity 1 of the signal multiplied by the time that the point in question is within the measuring surface during the signal clock. For a uniform movement and a rectangular lighting profile as in the Figures 2 a and 2 b, the contribution of the points between A and B on the banknote 1 increases linearly, between C and D it decreases linearly. It follows therefore between the points A and D, the in Fig. 3 shown dose distribution. The illumination gap width is denoted by s _B and the raster element length by s _R. The maximum dose P is again 100%.

The length of the ramps AB or DC of the dose distribution depends on the duration of the signal pulses for a given measuring surface geometry and given relative speed. It corresponds exactly to the path length l ₁ , which covers the banknote 1 during the cycle time T ₁ . It is therefore essential that during a signal clock, the banknote 1 covers only a path l ₁ , which is smaller than the length s _{B of} the measuring surface. In order to achieve a complete scanning of the banknote, it is sufficient if the following signal clock of the same signal type restarts when the point located at the beginning of the measuring area in the transport direction R at the beginning of the first clock (in FIG FIG. 2a the point B) has reached the end of the measuring surface. Exactly then, the raster elements are completely relative to each other so that only the areas between the points A and B and C and D of two successive raster elements of length s _R overlap. Due to the uniform velocity and the resulting linear increase or decrease of the dose P in these regions, the dose of these points detected in the adjacent raster elements again adds up to exactly 100% ( Fig. 3 ). This means that every point on the record carrier is viewed with the same sensitivity. His information is therefore always scanned to 100%. However, it can be distributed over two adjacent measured values. This is independent of the bar length.

The time between two signal clocks of a signal type Q ₁ , that is the duration T of the period minus the clock duration T ₁ , can now be used to scan the banknote 1 with signals of another signal type Q ₂ , Q ₃ ( Fig. 4 ). By a corresponding width of the illumination gap for these further signals, that is, a corresponding length s _{B of} the measuring surfaces with respect to this signal type, a seamless scanning can be achieved in the same way for this purpose. In the in Fig. 4 illustrated example, the illumination gap width or length s _{B of} the measuring surfaces is identical.

Fig. 4 shows, on the basis of three different signal types Q ₁ , Q ₂ , Q ₃ , how a period of successive signals can be arbitrarily divided into periods T ₁ , T ₂ , T ₃ and T ₀ in which the individual signal systems are active. Here, only the prerequisite must be satisfied that for all types of signals Q ₁ , Q ₂ , Q _3, the length s _{B of} the measuring surface is equal to the product of the relative velocity and the duration T of the period, so that for all signal channels always a complete scanning of the Banknote 1 in the desired manner results. The distance traveled during the individual time intervals T ₁ , T ₂ , T ₃ , T ₀ distances l ₁ , l ₂ , l ₃ , l ₀ add up again exactly to the length s _{B of} the measuring surface, ie to the width of the illumination gap on.

Fig. 4 also shows that the individual signal durations T ₁ , T ₂ , T _{3 of} different signal types Q ₁ , Q ₂ , Q ₃ do not necessarily have to sum up to 100% within the period T. In principle, the individual signal durations T ₁ , T ₂ , T _{3 can} also be different, so that, for example, one signal type Q ₁ within a period has a shorter signal duration T ₁ and the other signal types Q ₂ , Q _{3 have} a longer signal duration T ₂ , T ₃ . For example, a free time T ₀ within the period of signals may be used to read the transducers or perform calibration measurements or the like.

In FIG. 5 is the position of the measuring surfaces 10, 20 for two different signal types, here measuring surfaces 10 of a red color signal and measuring surfaces 20 of an infrared signal represented. As can be seen, lie in the inventive method, the measuring surfaces 10, 20 of the two types of signals, mutually shifted on the banknote 1. Because of the better recognizability here measuring surfaces 10, 20 are shown, which do not extend over the entire width of Banknote 1 extend. In addition, only two measuring surfaces 10 of the red light signal are shown. The dashed line shows, by way of example, the overlap region or the length s _{R of} the raster element at a number of measuring surfaces 20 of the infrared signal.

In a preferred embodiment, not shown, the measuring surfaces extend transversely to the transport direction R over the entire width of the banknote.

The inventive method provides a gapless, full-surface scanning of the bill at high banknote throughput. Here, the measurement data only a small processing and storage effort is necessary. Of course, as already mentioned above, the invention is not limited to the reading and checking of banknotes, but can also be used for any other record carrier.

Claims (8)

1. A method for reading sheet-shaped recording media (1) during a relative motion with respect to a reading station (2) which has at least one transmitter (3) for sequentially, periodically emitting at least two signals of different signal types (Q₁, Q₂, Q₃) with periods of equal duration (T), a common receiver (4) for the different signal types (Q₁, Q₂, Q₃) for detecting said signals modulated by the recording medium (1), and an evaluation unit for the detected signals, wherein a certain illumination characteristic results on the recording medium (1) with an illumination slit having a certain slit width, wherein the slit width corresponds precisely to the length (s_B) of the measuring area in the moving direction (R) as detected by the reading station (2) during a certain point in time, wherein grid elements having a certain extension (s_R) along the relative moving direction (R) are scanned cyclically in each of the signal types (Q₁, Q₂, Q₃) by means of the reading station (2) and, in so doing, a measuring area having the certain length (s_B) in the relative moving direction (R) is detected on the recording medium (1) at each point in time of a cycle, characterized in that the length (s_B) of the measuring area detected by the reading station (2) is chosen for each signal type (Q₁, Q₂, Q₃) to be equal to the path length (1) which the recording medium (1) moves along relative to the reading station (2) at a given relative speed during the duration (T) of a period of two successive signals of a signal type (Q₁, Q₂, Q₃).
2. The method according to claim 1, characterized in that a scanning is effected at least with an infrared signal and at least with a light signal of a certain wavelength in the visible range.
3. The method according to claim 1 or 2, characterized in that a scanning is effected at least with a bright-field signal and at least with a dark-field signal.
4. The method according to any of claims 1 to 3, characterized in that the measuring area extends over the total recording medium in the form of lines perpendicular to the relative motion.
5. An apparatus for reading sheet-shaped recording media (1) during a relative motion with respect to a reading station (2) which has at least one transmitter (3) for sequentially, periodically emitting at least two signals of different signal types (Q₁, Q₂, Q₃) with periods of equal duration (T), a common receiver (4) for the different signal types (Q₁, Q₂, Q₃) for detecting said signals modulated by the recording medium (1), and an evaluation unit for the detected signals, wherein a certain illumination characteristic results on the recording medium (1) with an illumination slit having a certain slit width, wherein the slit width corresponds precisely to the length (s_B) of the measuring area in the moving direction (R) as detected by the reading station (2) during a certain point in time, wherein the reading station (2) scans grid elements having a certain extension (s_R) along the relative moving direction (R) cyclically in each of the signal types (Q₁, Q₂, Q₃) and, in doing so, detects on the recording medium (1) at each point in time of a cycle a measuring area having the certain length (s_B) in the relative moving direction (R), characterized in that the transmitter geometry and/or receiver geometry of the reading station (2) is configured, and the relative speed and the cycle times selected, such that the length (s_B) of the measuring area detected by the reading station (2) is for each signal type (Q₁, Q₂, Q₃) equal to the path length (1) which the recording medium (1) moves along relative to the reading station (2) at the given relative speed during the duration (T) of a period of two successive signals of a signal type (Q₁, Q₂, Q₃).
6. The apparatus according to claim 5, characterized by at least one infrared transmitter and at least one transmitter for generating a light signal of a certain wavelength in the visible range.
7. The apparatus according to claim 5 or 6, characterized by at least one transmitter for generating a bright-field signal and at least one transmitter for generating a dark-field signal.
8. The apparatus according to any of claims 5 to 7, characterized in that the transmitter or transmitters and/or the receiver are configured and/or disposed such that the measuring area extends over the total recording medium in the form of lines perpendicular to the relative motion.

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