Test deck of artificially soiled banknotes, manufacturing process and uses thereof

Abstract

The present invention relates to a method of producing a test deck of artificially soiled banknotes, a test deck of artificially soiled banknotes, a use of the inventive test deck of artificially soiled banknotes for calibrating and / or evaluating performance of fitness sorting of a sorting apparatus for banknotes , and a method for calibrating and / or evaluating performance of fitness sorting of a sorting apparatus for banknotes using the inventive test deck, respectively according to the independent claims.

Description

FIELD OF INVENTION

[0001] The present invention relates to a method of producing a test deck of artificially soiled banknotes according to the independent claim, a test deck of artificially soiled banknotes, wherein at least one of the artificially soiled banknotes comprises a soil pattern classified with a soiling level (SL) C1 "fit for further circulation" and at least one of the artificially soiled banknotes comprises a soil pattern classified with a soiling level (SL) C2 "unfit for further circulation", characterized in that the soil patterns classified C1 and C2 are independently from each other composed of one or more, the same or different soil templates, and in that the soil patterns classified C1 and C2 are different from each other and are respectively defined by colour spatial modulation / distribution of the colour constituents, optical density of the colour constituents, spectral properties of the colour constituents, and / or size of the respective soil pattern, preferably wherein the test deck is obtainable by a method according to the inventive production method, a use of the inventive test deck of artificially soiled banknotes for calibrating a sorting apparatus for banknotes, and a method for calibrating a sorting apparatus for banknotes using the inventive test deck.BACKGROUND

[0002] A banknote sorting apparatus in particular evaluates whether a circulated banknote is "fit for further circulation" or is "unfit for further circulation" (so called "fitness sorting", e.g. "soil fitness sorting"). This evaluation is in particular conducted based on respective parameters of the soil present on circulated banknotes, wherein values of the parameters are detected by the banknote sorting apparatus.

[0003] The banknote sorting apparatus compares the detected values with reference values and either i) categorizes the sorted banknote as being "fit for further circulation" and activates means to allow further circulation or ii) categorizes the sorted banknote as "unfit for further circulation" and activates means to prohibit further circulation.

[0004] Presently, the reference values are obtained from actually circulated banknotes exhibiting different soil levels which are either classified "fit for further circulation" or "unfit for further circulation". This means, that reference samples of soiled banknotes, have to be manually selected from actually circulated banknotes. These reference samples are then compiled to form a test deck of circulated banknotes exhibiting different soiling levels as reference values.

[0005] In view of the dependence on soil patterns of real circulated banknotes, it is apparent that the use of such a manually compiled soiled test deck is today limited by the availability of respective soil patterns on soiled circulated banknotes. Furthermore, the selection and compilation of soiled circulated banknotes forming a test deck is a time-consuming, therefore costly, in particular as it requires the contribution of experts to sort and classify the soiled circulated banknotes. In addition, as such manually selected test decks exhibit necessary variation / deviation in the soil pattern from one test deck to another, the reproducibility of the test decks is low. In view of these deviations in manually selected test decks, it is somehow difficult to distinguish if potential deviations of the sorting performances of banknote sorting apparatus' are coming from detectors / sensors or come from the reference samples of different test decks. This evaluation is even more complicated when evaluations are done in different places, with different equipment, and with different banknotes test decks.

[0006] Additionally, such test decks of soiled banknotes selected from circulated banknotes can only be used a limited number of times in sorting apparatus' due to fragility of unfit banknotes. In particular the poor process ability in sorting apparatus' of unfit banknotes may limit their applicability, as they may have weak mechanical properties induced in particular by folding lines, ruptures, holes, and crumples resulting from circulation stress.

[0007] Alternatively, CN 112950837 A relates to a banknote damage condition identification method and device based on deep learning. The method comprises steps of obtaining the image information of a banknote, and respectively intercepting a defect image block and a standard image block from the image information to generate defect data and defect-free data; filtering and / or amplifying the defect data and the defect-free data to generate a training image, calibrating the damaged position of the banknote in the defect data to generate defect type data, and generating training set data according to the training image and the defect type data; training a preset YOLOv3 network through the training set data to obtain a banknote detection model, and inputting a banknote image to be detected into the banknote detection model to obtain feature parameters; and calculating to obtain a banknote defect ratio according to the characteristic parameters, and comparing the banknote defect ratio with a preset threshold to obtain a banknote damage condition.

[0008] Thus, there exists a need to improve the calibration and / or evaluation performance of fitness sorting, in particular soil fitness sorting of a banknote sorting. Moreover, there exists a need to improve calibration and / or evaluation performance of the fitness sorting, in particular soil fitness sorting when comparing different banknote sorting apparatus' using the same or different test decks. Furthermore, there exists a need to increase the lifetime (number of sorting steps) of a test deck of soiled banknotes.SUMMARY OF INVENTION

[0009] The aforementioned one or more needs is / are attended to at least in part by means of the claimed inventive subject matter. Advantages (preferred embodiments) are set out in the detailed description hereinafter and / or the accompanying figures as well as in the dependent claims.

[0010] Accordingly, a first aspect of this invention relates to a method for producing a test deck of artificially soiled banknotes, wherein at least one of the artificially soiled banknotes comprises an applied soil pattern classified with a soiling level (SL) C1 "fit for further circulation" and at least one of the artificially soiled banknotes comprises an applied soil pattern classified with a soiling level (SL) C2 "unfit for further circulation", characterized in that the method comprises or consists of the following steps: a) providing two or more banknotes being non-circulated banknotes and / or banknotes classified with a soiling level (SL) C1 "fit for further circulation", b) applying to one or more of the banknotes of step a) one or more colour constituents to form a soil pattern classified with a soiling level (SL) C1 "fit for further circulation", and c) applying to one or more of the banknotes of step a) one or more colour constituents to form a soil pattern classified with a soiling level (SL) C2 "unfit for further circulation", and wherein the applied soil patterns classified C1 and C2 are independently from each other composed of one or more, the same or different soil templates, and wherein the applied soil patterns classified C1 and C2 are different from each other and are respectively defined by colour spatial modulation / distribution of the colour constituents, optical density of the colour constituents, spectral properties of the colour constituents and / or size of the respectively applied soil patterns.

[0011] In other words, the artificially soiled banknotes, may emulate soil, stain, graffiti, de-inked banknote, tear, hole, mutilation, repair, crumple, limpness, folding line and / or gloss on a banknote and their respective soiling levels resulting in classifications of being either fit or unfit for further circulation.

[0012] A second aspect of this invention relates to a test deck of artificially soiled banknotes, wherein at least one of the artificially soiled banknotes comprises an applied soil pattern classified with a soiling level (SL) C1 "fit for further circulation" and at least one of the artificially soiled banknotes comprises an applied soil pattern classified with a soiling level (SL) C2 "unfit for further circulation", characterized in that the applied soil patterns classified C1 and C2 are independently from each other composed of one or more, the same or different soil templates, and wherein the applied soil patterns classified C1 and C2 are different from each other and are respectively defined by colour spatial modulation / distribution of the colour constituents, optical density of the colour constituents, spectral properties of the colour constituents, and / or size of the respective soil template, preferably wherein the test deck is obtainable by the production method of the first inventive aspect.

[0013] A third aspect of this invention relates to the use of a test deck of artificially soiled banknotes according to the second inventive aspect characterized in that the test deck is used for calibrating and / or evaluating performance of fitness sorting of a sorting apparatus for banknotes.

[0014] A fourth aspect of this invention relates to a method for calibrating and / or evaluating performance of fitness sorting of a sorting apparatus for banknotes comprising or consisting of the following steps: a) providing a banknote sorting apparatus with a sorting device for sorting circulated banknotes into categories A1 "fit for further circulation" and A2 "unfit for further circulation", wherein the sorting device is in data communication with an evaluation device for evaluating whether a circulated banknote is fit or unfit for further circulation, wherein the evaluation device comprises a detector for detecting a parameter value representing the soiling level (SL) of the sorted banknote and a processing means for classifying the detected parameter value representing the soiling level of the sorted banknote into the category A1 or the category A2, b) providing a test deck of banknotes with two or more artificially soiled banknotes according to the second inventive aspect, wherein at least one of the artificially soiled banknotes comprises an applied soil pattern classified with a soiling level (SL) C1 "fit for further circulation" and at least one of the artificially soiled banknotes comprises an applied soil pattern classified with a soiling level (SL) C2 "unfit for further circulation", c) separately sorting the artificially soiled banknotes of the test deck of step b) with the banknote sorting apparatus of step a) and respectively detecting one or more parameter values representing the soiling level (SL) of the sorted artificially soiled banknotes with the detector of the evaluation device, and d) calibrating and / or evaluating performance of fitness sorting of the evaluation device by instructing the processing means to respectively correlate the detected one or more parameter values of the artificially soiled banknotes with a soiling level (SL) of a circulated banknote and to respectively categorize the detected one or more parameter values into category A1, in case the detected one or more parameter values correspond to a soil pattern classified C1, and to respectively categorize the detected one or more parameter values into category A2, in case the detected parameter values correspond to the soil pattern classified C2.

[0015] The scope of the invention is defined by the appended claims.BRIEF DESCRIPTION OF DRAWINGS

[0016] Further aspects, characteristics and advantages of the invention will ensue from the following description of the embodiments with reference to the accompanying drawings, wherein Figs. 1A) to 1E)represent images of modulation types of applied soil patterns, wherein soil pattern image 1A) shows no modulation relating to a low soil level, the soil pattern image 1B) (modulation type 1) shows an intermediate degree of modulation relating to an intermediate soil level, and the soil pattern 1C) (modulation type 2) shows a high degree of modulation relating to a high soil level; soil pattern image 1D) and 1E) represent halftoned images of a 50 % greyscale image, wherein the halftoned image in Fig. 1D) is prepared by error diffusion (modulation 2) and in Fig. 1E) is prepared by algorithm using a dithering pattern (modulation 3). FIGS. 2A) to 2Hrepresent images of four applied soil pattern images 2A) to 2D) for modulation type 1 and four soil pattern images 2E) to 2H) for modulation type 2 respectively exhibiting different ink coverage from low to high ink coverage representing low to high soil level. FIGS. 3A), 3B)represent images of two applied soil pattern images 3A) and 3B) respectively exhibiting a colour shade representing a low soil level Fig. 3A) and a colour shade representing a high soil level Fig. 3B). FIG. 4A) to 4D)represent four configurations for printing two respective soil patterns SP1 and SP2 using one or more soil templates (ST, ST1, ST2, ST3, ... STN) on a banknote substrate 1. FIG. 5represent a graph displaying soil parameters (y-axis) as a function of soil level (x-axis) of an inventive test deck with artificially soiled banknotes evaluated by a banknote sorting apparatus outlining a quasi-linear behaviour. FIG. 6represent a graph displaying soil parameter (y-axis) as a function of soil level (x-axis) of an inventive test deck with artificially soiled banknotes using UV inkjet printing evaluated by a banknote sorting apparatus during and after an endurance test. FIGS. 7A), 7B)represent a graph displaying L* coordinates of CIELAB coordinate system (y-axis) as a function of twelve soil levels (x-axis) of an inventive test deck with artificially soiled banknotes (Fig. 7A) and as a function of sorting machine soil parameter of a reference test deck extracted from circulation classified in 5 classes from super Fit to super Unfit (Fig. 7B). DETAILLED DESCRIPTION OF EMBODIMENTS

[0017] As set out in more detail hereinafter, the inventors of the different aspects of this invention provide herewith an inventive test deck of artificially soiled banknotes respectively with differently applied soil patterns representing different soiling levels, as a reliable and reproducible tool for calibrating and / or evaluating performance of fitness sorting of a banknote sorting apparatus.

[0018] Thus, basically, the present invention uses a test deck of artificially soiled banknotes for calibration of a banknote sorting machine, wherein one of the two or more, preferably twelve test banknotes exhibiting different soiling levels, is defined based on the parameters including optical properties, as "just unfit for circulation" (level N JustUnfit ), wherein the level N JustUnfit and higher soiling levels (N ≥ N JustUnfit ) are accordingly classified C2 "unfit for further circulation" and lower soiling levels (N < N JustUnfit ) are classified C1 "fit for further circulation". Accordingly, the soiling level N JustUnfit represents the soiling level with the lowest C2 classification and, thus, a threshold for discriminating between banknotes respectively fit or unfit for further circulations.

[0019] As a guideline, the soiling level N JustUnfit is generally to be defined considering one or more correlated parameters exhibited by the respective applied soil pattern, including optical properties of the colour constituents of the applied soil pattern, such as colour spatial modulation / distribution of the colour constituents, optical density of the colour constituents, spectral properties of the colour constituents, and / or size, in particular with respect to graffiti pattern, of the respective soil template. The soiling level N JustUnfit will generally be defined by the respective banknote issuing authorities in order to safeguard efficient banknote circulation.

[0020] In other words, the present invention provides a test deck of artificially soiled banknotes having a (continuous) distribution of different soil levels, from low soil level ("classified C1 "fit for further circulation") to high soil levels (classified C2 "unfit for further circulation"). The artificially applied soil patterns generally exhibit properties and a dynamic range equivalent to the fitness of banknotes encountered in circulation. This distribution of soiling levels may be covered by as much different artificially soiled banknotes exhibiting different applied soil patterns with different soiling levels.

[0021] In the context of the present invention, the expression "artificially soiled banknote" means, that a banknote including a so called "non-circulated" banknote (synonym: "genuine banknote") or a circulated banknote exhibiting a certain degree of soiling, but still classified C1 "fit for further circulation" is artificially treated with one or more colour constituents to form an artificially applied soil pattern on the front and / or reverse side of the banknote, which imitates and / or emulates the properties of a used banknote after circulation exhibiting a certain soiling level (SL). The fitness check is generally conducted using standards for automated fitness checking of banknotes by banknote handling machines, for example as set out for Euro Series 2 (ES2) or Euro Series 1 (ES1) banknotes under: https: / / www.ecb.europa.eu / euro / cashprof / cashhand / recycling / html / fitness.en.html

[0022] The fitness criteria mentioned under this link and incorporated herein at least in part below, may be subject to change.

[0023] Accordingly, a list of sorting criteria for automated fitness sorting comprises the following defects: 1. Soil, i.e. general distribution of dirt across the entire euro banknote; optical fitness classification is set out below. 2. Stain, i.e. localised concentration of dirt, e.g. for Euro banknotes with a localised concentration of dirt covering at least 9 mm by 9 mm in the non-printed area or at least 15 mm by 15 mm in the printed area are unfit; in case the applied soil pattern represents a stain soil feature, the optical fitness classification according to present invention can be used. 3. Graffiti, i.e. added image or lettering written or marked in any manner on a euro banknote, wherein the localized graffiti covering area to be regarded unfit is deinfed by every authority, generally, a graffiti covering area of at least 9 mm by 9 mm in the non-printed area or at least 15 mm by 15 mm in the printed area may be regarded unfit; in case the applied soil pattern represents a graffiti soil feature, the optical fitness classification according to present invention can be used. 4. De-inked note, i.e. lack of ink on part or whole of the euro banknote, e.g. a washed euro banknote; to be detected by image detectors or UV detectors, in case the applied soil pattern represents a de-inked soil feature, the optical fitness classification according to present invention can be used. 5. Tear, in order to be considered a banknote fit for further circulation, a tear with vertical direction may have a maximum width and length are 4 mm / 8 mm, or a tear with horizontal direction may have a maximum width and length are 4 mm / 15 mm, a tear with diagonal direction may have a maximum width and length are 4 mm / 18 mm; in case the applied soil pattern represents a tear as soil feature, the optical fitness classification according to present invention can be used. 6. Hole, in order to be considered a banknote fit for further circulation, the hole may not be greater than 10 mm 2< , in case the applied soil pattern represents a hole as soil feature, the optical fitness classification according to present invention can be used. 7. Mutilation, i.e. Euro banknotes with part(s) missing, along at least one edge (in contrast to holes); in order to be considered a banknote fit for further circulation, Euro banknotes may not have length reduced by 6 mm or more or widths reduced by 5 mm or more, respectively measured in comparison to nominal lengths and widths of the new euro banknotes; in case the applied soil pattern represents a mutilation as soil feature, the optical fitness classification according to present invention can be used. 8. Repair, i.e. parts of one or more euro banknotes joined together by tape or glue or other means; in order to be considered a banknote fit for further circulation the area covered by tape may not be greater than 10 mm by 40 mm and which is more than 50 µm thick; in case the applied soil pattern represents a repair as soil feature, the optical fitness classification according to present invention can be used. 9. Crumples, i.e. multiple random folds; in case the applied soil pattern represents crumples as soil feature, the optical fitness classification according to present invention can be used. 10. Limpness, i.e. structural deterioration resulting in a marked lack of stiffness; wherein limpness normally correlates with soiling, so that limp euro banknotes are generally also detected via soil sensors; in case the applied soil pattern represents a limpless soil feature, the optical fitness classification according to present invention can be used. 11. Fold; wherein folded euro banknotes because of their reduced length or width, can be detected by sensors checking the size of the banknotes, e.g. for Euro banknotes: folds leading to a reduction in length greater than 6 mm or a reduction in width greater than 5 mm are generally classified unfit for further circulation; in case the applied soil pattern represents a fold as soil feature, the optical fitness classification according to present invention can be used. 12. Folded corner; wherein for Euro banknotes, a folded corner with an area of more than 130 mm 2< and a length of the smaller edge greater than 10 mm is generally classified unfit for further circulation; in case the applied soil pattern represents a folded corner as soil feature, the optical fitness classification according to present invention can be used.

[0024] As an example, soil as general distribution of dirt across the entire banknote generally increases the optical density of banknotes. The following table specifies the maximum density increase of limit samples (threshold samples) compared to new Euro banknotes to be met so that the Euro banknote may still be classified C1 "fit for further circulation": Denomination-Series Maximum density increase of limit sample compared to new euro banknote Filter €5-ES2 0.04Magenta€10-ES2 0.04Magenta€20-ES2 0.07Magenta€50-ES2 0.07Magenta€100-ES2 0.07Magenta€200-ES2 0.07Magenta

[0025] Thus, the magenta optical density parameter may be used to classify whether an exemplary banknote, such as ES2, is to be classified C1 "fit for further circulation" or C2 "unfit for further circulation". In other words, in case the magenta optical density (measured according to the minimum standards for automated fitness checking of euro banknotes by banknote handling machines as set out above) of a banknote prior to or after artificial soiling is OD mag ≤ 0.04 for €5 / € 10 ES2 banknotes; or ≤ 0.07 for € 20 / € 50 / € 100 / € 200 ES2 banknotes; , then the banknote is classified C1 "fit for further circulation".

[0026] Euro banknotes not meeting these criteria are classified C2 "unfit for further circulation". The densitometric measurements of the reference euro banknotes are based on the following criteria. Standard for density measurements: ISO 5 parts 3 and 4 Standard for the filters: DIN 16536 Absolute measurements: standard calibration (white tile) Polarisation filter: on Aperture: 3 mm Illumination: D65 / 2 Background: white tile standard calibration

[0027] The density increase of a reference banknote is the highest value between the averages of at least four measurement points measured on the front and on the back of the banknote in the unprinted area and without any watermark modulation.

[0028] In the context of the present invention, the expression "soiling level" (synonym "SL" or "soil level") represents a discrete level of soiling represented on a banknote correlating with a respective parameter or parameter set of a soil pattern detected and evaluated by the banknote sorting apparatus and being classified as being "fit" (C1) or "unfit" (C2) for further circulation.

[0029] In the context of the present invention the expression "a soil pattern" / "an applied soil pattern" includes one or more, the same or different soil templates of colour constituents, wherein the soil pattern including all separate soil templates if applicable (synonym: "soil template" or "overall soil template") is generally applied to at least part of the surface of the front side of the banknote substrate and / or the reverse side of the banknote substrate. The applied soiling pattern and optionally the soil template as such may emulate any defect relevant for fitness sorting, such as stain, graffiti, de-inked banknote, tear, hole, mutilation, repair, crumple, limpness, folding line and / or gloss on a banknote and their respective soiling levels resulting in classifications of being either fit or unfit for further circulation. Preferably, the soil pattern is generally applied to 10 % to 100 %, in particular 20 %, 30 %, 40 %, 50 %, 60 %, 70 %, 80 %, 90 % or more respectively of the overall surface area or the unprinted watermark region of the front side of the banknote substrate and / or the reverse side of the banknote substrate.

[0030] In case a plurality of the same or different soil templates are used to form the applied soil pattern, two or more of the soil templates, preferably all soil templates forming the soil pattern may be applied to the substrate of the untreated banknote in continuous or discontinuous repetition mode. The soil templates may be the same or different. Multiplexing of different soil patterns can be achieved between two or more the different soil patterns with periodic or random order. In addition, an "unfit" soiling level C2 may be obtained by direct multilayer printing of the two or more soil templates, which - when used alone - would be classified C1 "fit for further circulation" in the following way: The soil template classified "fit" exhibiting a suitable low modulation and low optical density is used to make prints of the same template on the substrate by applying the soil template "fit" in register to increase the optical density. In addition or alternatively, the same soil template "fit" is printed introducing a micro shift in x and / or y direction (e.g., a ΔXY with an inkjet printer) between the respective soil template prints to increase and create a new modulation as well as an increased optical density, so that the applied soil pattern including the combination of the printed soil templates then is to be classified C2 "unfit for further circulation".

[0031] The inventive method generally defines respective specific soil templates associated to respective soil levels in order to emulate the different soil properties encountered in circulated banknotes.

[0032] Thus, the applied soil pattern exhibits one or more properties / parameters including colour spatial modulation / distribution of the colour constituents, optical density of the colour constituents, spectral properties / shade of the colour constituents, and / or size of the respectively applied soil patterns. Accordingly, the applied soil pattern of a distinct soil level in particular on a respective side of a banknote represents a unique combination of parameters controlled through the inventive artificial soiling process, based on printing technologies for example.

[0033] In the context of the present invention, the expression "test deck of artificially soiled banknotes" means, that at least one of the artificially soiled banknotes comprises an applied soil pattern classified with a soiling level (SL) C1 "fit for further circulation" and at least one of the artificially soiled banknotes comprises an applied soil pattern classified with a soiling level (SL) C2 "unfit for further circulation". In case the applied soil pattern is classified C1, a banknote sorting apparatus is calibrated and / or evaluated with the respective artificially soiled banknote to detect the applied soil pattern and evaluate the soil level to be "fit for further circulation". In other words, the banknote sorting apparatus is calibrated and / or evaluated with the artificially soiled banknote classified C1 to correlate the detected parameter values with the action category A1 "fit for further circulation", wherein generally suitable means are activated to allow further circulation of a respective banknote exhibiting the soil pattern classified C1. In case the applied soil pattern is classified C2, a banknote sorting apparatus is calibrated and / or evaluated with the respective artificially soiled banknote to detect the applied soil pattern and evaluate the soil level C2 to be "unfit for further circulation". In other words, the banknote sorting apparatus is calibrated and / or evaluated with the artificially soiled banknote classified C2 to correlate the detected parameter values with the action category A2 "unfit for further circulation", wherein generally suitable means are activated to prevent further circulation of a respective banknote exhibiting the soil pattern classified C2.

[0034] In the context of the present invention, the expressions "comprising" or "containing" shall be understood to have a broad meaning similar to the term "including" and will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. This definition also applies to variations on the term "comprising" such as "comprise" and "comprises" as well as variations on the term "containing" such as "contain" and "contains".

[0035] In comparison to the prior art, which uses manually extracted soiled banknotes from circulation, the test deck and production method thereof according to the first and second inventive aspects improve the calibration and / or evaluation performances of a banknote sorting apparatus, as artificially soiled banknotes of different test decks exhibiting the same soil pattern will also exhibit same parameter values for calibration and / or evaluation. Thus, the present invention reduces performance deviations in the prior art due to the inventive artificially soiled test deck used when performing calibration and / or evaluation on a banknote sorting apparatus. In other words, deviations, which may still be seen when using the inventive method, may then relate to the performance of the detector / sensor of the banknote sorting apparatus. Accordingly, the inventive test decks can thus be used to increase calibration and / or evaluation performances of different banknote sorting apparatus'.

[0036] Moreover, due to the fact, that the artificially soiled banknotes do not exhibit weak mechanical properties due to crumples, folding lines, or ruptures etc. upon circulation stress, the lifetime, i.e. the number of sorting / calibrating steps, of the inventive test deck can be increased in comparison to the prior art test decks using reference samples selected from circulated banknotes, which may comprise crumples, folding lines, or ruptures upon the circulation stress.

[0037] In order to provide a test deck according to the present invention, which is as close as possible to the soiled banknotes of the physical reality in circulation, the inventive production method generally provides an applied soil pattern, which emulates colour modulation (spatial distribution), optical density, and spectral properties (colour shade / luminance parameters) of the real soiled banknotes of circulation.

[0038] The applied soil pattern is generally generated by one or more, the same or different soil templates. In other words, in case the soil pattern is generated by the use of one soil template, the soil pattern and the soil template are equivalent. In case the soil pattern is generated by the use of two or more, the same or different soil templates, then each soil template forms a sub-part of the soil pattern. In case a plurality of soil templates are used to generate the soil pattern, one or more soil templates may be regarded as "fit for further circulation", but the combined arrangement of the soil templates may lead to classifying the soil pattern as C2 "unfit for further circulation". The use of more soil templates may be beneficial to imitate the natural soil pattern as close as possible. The banknote substrate may comprise two or more, the same or different soil templates in continuous or discontinuous repetition for forming the soil pattern.

[0039] In order to imitate different soiling conditions, the respectively applied soil patterns may comprise a uniform soiling pattern, i.e. the one or more colour constituents are uniformly applied within the area of the soil template, which relates to a lower soiling level generally being classified C1 "fit for further circulation" (so called first order soil pattern), and / or one or more second order soil patterns, which relate to an increased / higher soil level and may - dependent on the actual soiling pattern - be classified C2 "unfit for further circulation". The second order soil pattern may in particular include a gloss template, i.e. colour constituents are applied to imitate an optical gloss property, a template of nonuniform soiling, wherein the one or more colour constituents are non-uniformly applied within the area of the soil pattern, and one or more templates representing macroscopic objects, wherein the one or more colour constituents are applied in such a way that they imitate an optical property of soil, stain, graffiti, de-inked banknote, tear, hole, mutilation, repair, crumple, limpness, folding line and / or gloss.

[0040] Thus, using the inventive production method, the inventive test deck comprises certain predetermined applied soil patterns, which may not be present in a prior art test deck, in case no respective soiled banknote showing the respective soil pattern can be manually selected from circulated banknotes.

[0041] According to the first inventive aspect a method for producing a test deck of artificially soiled banknotes, wherein at least one of the artificially soiled banknotes comprises an applied soil pattern classified with a soiling level (SL) C1 "fit for further circulation" and at least one of the artificially soiled banknotes comprises an applied soil pattern classified with a soiling level (SL) C2 "unfit for further circulation", characterized in that the method comprises or consists of the following steps: Providing two or more banknotes classified C1, including non-circulated banknotes and banknotes classified fit for further circulation, wherein the banknote substrate can generally be any suitable substrate, in particular selected from paper, polymer, composite, etc., optionally wherein the banknotes classified C1 comprise a varnish coating on at least part of the substrate surface.

[0042] Applying to one or more of the banknotes of step a) one or more colour constituents to form a soil pattern classified with a soiling level (SL) C1 "fit for further circulation". The colour constituents can generally be selected from any suitable colour constituents and are described in more detail herein below. The applied soil pattern classified C1 is generally generated by the use of one or more, the same or different soil templates.

[0043] Applying to one or more of the banknotes of step a) one or more colour constituents to form a soil template classified with a soiling level (SL) C2 "unfit for further circulation". The colour constituents can generally be selected from any suitable colour constituents and are described in more detail herein below. The applied soil pattern classified C2 is generally generated by the use of one or more, the same or different soil templates.

[0044] The applied soil patterns classified C1 and C2 are independently from each other composed of one or more, the same or different soil templates, wherein the applied soil patterns classified C1 and C2 are different from each other and are respectively defined by colour spatial modulation / distribution of the colour constituents, optical density of the colour constituents, spectral properties of the colour constituents, and / or size of the respective soil pattern.

[0045] As also described above, the present invention uses a test deck of artificially soiled banknotes for calibration of fitness sorting performance of a banknote sorting machine, wherein one of the two or more, preferably twelve test banknotes exhibiting different soiling levels is to be defined based on the parameters including optical properties, as "just unfit for circulation" (level N JustUnfit ), wherein the level N JustUnfit and higher soiling levels (N ≥ N JustUnfit ) are accordingly classified C2 "unfit for further circulation" and lower soiling levels (N < N JustUnfit ) are classified C1 "fit for further circulation". As a guideline, the soiling level N JustUnfit is generally defined considering one or more correlated relevant parameters, including optical properties, such as colour spatial modulation / distribution of the colour constituents, optical density of the colour constituents, spectral properties of the colour constituents, and / or size of the respective soil template.

[0046] The inventive calibration method may generally use two or more, in particular six, seven, eight, nine, ten, eleven, twelve or more different soiling levels in the artificially soiled test deck. A more advanced calibration may be achieved by using a higher number of different soiling levels, such as nine levels or higher, or twelve levels or higher. Generally, the higher the number of different soiling levels, the better the calibration / control of the sorting machine, as it may additionally identify how far the detected parameters discriminate from the threshold level (N JustUnfit ). Moreover, the higher the number of soiling levels, the better the fine-tuning by a given reference case for the modification of the relevant parameters on the banknote sorting machine.

[0047] According to an additional or alternative embodiment of the present invention, the soiling level of the respectively applied soil patterns is further respectively defined by one or more macroscopic properties emulating soil, stain, graffiti, de-inked banknote, tear, hole, mutilation, repair, crumple, limpness, folding line and / or gloss of a circulated banknote as set out above with respect to the minimum standards for automated fitness checking of euro banknotes by banknote handling machines. As an example stained Euro banknotes with a localized concentration of dirt covering at least 9 mm by 9 mm in the non-printed area or at least 15 mm by 15 mm in the printed area are classified as C2 "unfit for circulation". Euro banknotes with tears which are open and not partly or fully covered by the machine's transport belt(s) are unfit if the size of the tear is greater than indicated above.

[0048] According to an additional or alternative embodiment of the present invention, the one or more colour constituents are applied to the banknotes classified C1 in step b) and / or c) by halftone application methods. Halftone is a reprographic technique that emulates a continuous-tone imagery by applying the colour constituents in dotted form. The dots may vary in particular in size and / or spacing and, thus, can generate a gradient-like effect. Example of half tone application methods include digital halftoning, and in particular inverse halftoning using spatial and / or frequency filtering, such as error diffusion methods and ordered dithering methods, as well as optimization-based filtering methods. Optionally suitable de-screening methods are applied.

[0049] According to an additional or alternative embodiment of the present invention, the one or more colour constituents are applied to the banknotes classified C1 in step b) and / or c) by a printing process, preferably by a digital printing process, such as inkjet printing process. In particular, the halftoning method is applied by a digital printing process, in particular an inkjet printing process.

[0050] According to an additional or alternative embodiment of the present invention, the one or more colour constituents in step b) and / or c) are represented by the constituents of a CMYK (cyan, magenta, yellow and key (black)) ink set. The CMYK colour model is in particular suitable for digital halftoning.

[0051] According to an additional or alternative embodiment of the present invention, the applied soil pattern is respectively defined by CMYK ink ratio, modulation type of CMYK inks on artificially soiled banknote and / or coverage of the CMYK inks on the substrate, and the ratio of CMYK inks on artificially soiled banknote. According to one example, the soil level is defined by CMYK ink ratio (respectively for each C, M, Y and K the ratio may be ≤ 25, wherein the C ratio may be preferably in the range of less than 5, more preferably in the range of 1 to 3; wherein the M ratio may preferably be less than 20, more preferably 1 to 15; wherein the Y ratio may preferably 3 to 25; and wherein the K ratio may be preferably ≤ 2, preferably between 0 and including 1); modulation type of CMYK inks on artificially soiled banknote, such as error diffusion algorithm or algorithm using a dithering pattern; and coverage of CMYK inks on artificially soiled banknote, preferably between 10 to 80 % , more preferably 20 to 70 % more preferably 30 to 60 %, respectively based on the surface area of the banknote substrate.

[0052] According to an additional or alternative embodiment of the present invention, the one or more colour constituents in step b) and / or c) further comprise one or more inks comprising a ultra-violet (UV) property and / or one or more inks comprising an infrared (IR) property. In this case, it may be beneficial to provide transparent inks exhibiting the UV and / or IR property. In particular a direct tint ink exhibiting the respective UV and / or IR properties may be used.

[0053] According to an additional or alternative embodiment of the present invention, in step b) two or more different soil patterns classified C1 are applied to two or more banknotes classified C1 and / or wherein in step c) two or more different soil patterns classified C2 are applied to two or more banknotes classified C1.

[0054] According to an additional or alternative embodiment of the present invention, the applied different soil patterns respectively represent different soil levels.

[0055] According to an additional or alternative embodiment of the present invention, the applied soil pattern of step b) and / or the applied soil pattern of step c) is / are formed by using one or more UV-curing ink constituents.

[0056] According to the second inventive aspect, a test deck of artificially soiled banknotes is provided, wherein at least one of the artificially soiled banknotes comprises an applied soil pattern classified with a soiling level (SL) C1 "fit for further circulation" and at least one of the artificially soiled banknotes comprises an applied soil pattern classified with a soiling level (SL) C2 "unfit for further circulation", characterized in that the applied soil patterns classified C1 and C2 are independently from each other composed of one or more, the same or different soil templates, and in that the soil patterns classified C1 and C2 are different from each other and are respectively defined by colour spatial modulation / distribution of the colour constituents, optical density of the colour constituents, spectral properties of the colour constituents, and / or size of the respective soil pattern, preferably wherein the test deck is obtainable by a method according to the first inventive aspect.

[0057] The applied soil pattern may be arranged on the front side and / or on the reverse side of the banknote substrate classified C1 to be artificially soiled. For the same soil level, the applied soil pattern comprising one or more soil templates applied to the front and / or reverse side of the banknote substrate may differ, in particular in relation to the surface area, surface condition and the dot gain of the ink.

[0058] The inventive artificially soiled test deck may also include one or more reference banknotes, which are not artificially soiled, preferably one or more non-circulated (synonym: "genuine") reference banknotes.

[0059] Details regarding suitable banknote substrate classified C1 to be artificially soiled, colour constituents and definitions of colour modulation of the colour constituents, optical density of the colour constituents, spectral properties of the colour constituents, and / or size in the respective soil template are disclosed in particular with respect to the first inventive aspect as well as in the detailed description herein below and in the figures.

[0060] The inventive test deck may generally comprise two or more, in particular eight, nine, ten, eleven, twelve or more artificially soiled banknotes respectively exhibiting different soiling levels. Generally, the higher the number of different soiling levels of artificially soiled banknotes in the inventive test deck, the better the calibration / control of the sorting machine, as the higher number allows identifying more precisely how far the detected parameters of a circulated banknote deviate from the threshold level (N JustUnfit ). Moreover, the higher the number of soiling levels of the artificially soiled banknotes, the better is the fine-tuning by a given reference case for the modification of the relevant parameters on the banknote sorting machine.

[0061] According to the third inventive aspect a use of a test deck of artificially soiled banknotes according to the second inventive aspect is provided, characterized in that the test deck is used for calibrating and / or evaluating performance of fitness sorting of a sorting apparatus for banknotes.

[0062] According to a fourth inventive aspect a method for calibrating and / or evaluating performance of fitness sorting of a sorting apparatus for banknotes comprising or consisting of the following steps is provided: e) providing a banknote sorting apparatus with a sorting device for sorting circulated banknotes into categories A1 "fit for further circulation" and A2 "unfit for further circulation", wherein the sorting device is in data communication with an evaluation device for evaluating whether a circulated banknote is fit or unfit for further circulation, wherein the evaluation device comprises a detector for detecting a parameter value representing the soiling level (SL) of the sorted banknote and a processing means for classifying the detected parameter value representing the soiling level of the sorted banknote into the category A1 or the category A2, f) providing a test deck of banknotes with two or more artificially soiled banknotes according to the second inventive aspect, wherein at least one of the artificially soiled banknotes comprises an applied soil pattern classified with a soiling level (SL) C1 "fit for further circulation" and at least one of the artificially soiled banknotes comprises an applied soil pattern classified with a soiling level (SL) C2 "unfit for further circulation", g) separately sorting the artificially soiled banknotes of the test deck of step b) with the banknote sorting apparatus of step a) and respectively detecting one or more parameter values representing the soiling level (SL) of the sorted artificially soiled banknotes with the detector of the evaluation device, and h) calibrating and / or evaluating performance of fitness sorting of the evaluation device by instructing the processing means to respectively correlate the detected parameter values of the artificially soiled banknotes with a soiling level (SL) of a circulated banknote and to respectively categorize the detected parameter value into category A1, in case the detected parameter value corresponds to a soil pattern classified C1, and to respectively categorize the detected parameter value into category A2, in case the detected parameter value corresponds to the soil pattern classified C2.

[0063] According to an additional or alternative embodiment of the present invention, the method for calibrating and / or evaluating performance of fitness sorting of the banknote sorting apparatus is further configured to detect a parameter value or a set of parameter values representing the soiling level of the artificially soiled banknotes, preferably selected from one, two, three or more parameters of the group consisting of colour modulation of the soil template, optical density of the soil template, spectral properties and / or size of the soil template.

[0064] According to an additional or alternative embodiment of the present invention, the method for calibrating and / or evaluating performance of fitness sorting of the banknote sorting apparatus is further configured to detect a parameter value or a set of parameter values further selected from one or more macroscopic properties of the applied soil pattern, wherein the one or more macroscopic properties emulate soil, stain, graffiti, de-inked banknote, tear, hole, mutilation, repair, crumple, limpness, folding line and / or gloss of a circulated banknote.

[0065] The present invention is described in the following based on exemplary embodiments, which merely serve as examples and which shall not limit the scope of the present protective right.DETAILED DESCRIPTION OF FIGURES

[0066] Further characteristics and advantages of the present invention will ensue from the following description of example embodiments of the inventive aspects with reference to the accompanying figures.

[0067] As already mentioned above, basically, the present invention uses a test deck of artificially soiled banknotes for calibration of a banknote sorting machine, wherein one of the two or more, preferably twelve test banknotes exhibiting different soiling levels is to be defined based on one or more parameters including optical properties, as "just unfit for circulation" (level N JustUnfit ), wherein the level N JustUnfit and higher soiling levels (N ≥ N JustUnfit ) are accordingly classified C2 "unfit for further circulation" and lower soiling levels (N < N JustUnfit ) are classified C1 "fit for further circulation". As a guideline, the soiling level N JustUnfit is generally to be defined considering one or more correlated relevant parameters, including optical properties, such as colour spatial modulation / distribution of the colour constituents, optical density of the colour constituents, spectral properties of the colour constituents, and / or size of the respective soil template.

[0068] According to an advanced embodiment the present invention provides a test deck of artificially soiled banknotes exhibiting a (continuous) distribution of soil levels, from brand new (classified C1 as "fit for further circulation") to super unfit banknotes (classified C2 "unfit for circulation"). The artificially soiled banknotes generally exhibit properties and a dynamic range equivalent to the applied soil pattern and, thus, the fitness encountered of a banknote in circulation. As disclosed above, the artificially soiled banknote test deck may also include one or more non-circulated reference banknotes.

[0069] According to the present invention, the distribution of soil levels is generally covered by as much application steps of colour constituents (synonym: "soil steps") as the method of producing the test deck according to the first inventive aspect requires in order to achieve a applied soil pattern (SP) with sufficient reproducibility.

[0070] According to an additional or alternative embodiment of the inventive production method, a predetermined applied soil pattern is correlated with a predetermined soil level, wherein the applied soil pattern emulates soil properties of a circulated banknote and is either classified C1 "fit for further circulation" (emulating a newly circulated banknote or a banknote still regarded suitable to be circulated) or classified C2 "unfit for further circulation" (emulating a circulated exhibiting a soil pattern, which renders the banknote unfit for further circulation).

[0071] According to the present invention, the applied soil pattern is respectively defined by colour modulation / spatial distribution of the colour constituents, optical density of the colour constituents, spectral properties of the colour constituents, and / or size in the respective soil template. The applied soil pattern may be generated by one or more, the same or different soil templates. In other words, in case the applied soil pattern is generated by the use of one soil template the soil pattern and the soil template are equal. In case the applied soil pattern is generated by the use of two or more, the same or different soil templates, then each soil template forms a sub-part of the applied soil pattern. In case a plurality of soil templates are used to generate the applied soil pattern, one or more soil templates may be regarded as "fit for further circulation", but the combined arrangement of the soil template(s) may lead to classifying the applied soil pattern C2 "unfit for further circulation".

[0072] According to an additional or alternative embodiment of the present invention, artificially soiled banknotes of a test deck may comprise the same or different soil templates on the front and / or the reverse side of the banknote substrate, but the applied soil patterns, i.e. the overall pattern of front and reverse side of the artificially soiled banknotes classified C1 and C2, differ for different soil levels. The applied soil patterns on the front and reverse side of one artificially banknote may differ with respect to the detectable parameter or set of parameters, in particular relating to the surface area, the surface condition and the dot gain of the ink.

[0073] According to an additional or alternative embodiment of the present invention, each soil level of the artificially soiled banknotes exhibits a predetermined applied soil pattern on a defined side, front or reverse side, of the artificially soiled banknote, wherein the applied soil pattern exhibits a predetermined, preferably unique combination of colour constituents forming a colour spatial modulation / distribution of the colour constituents, optical density of the colour constituents, colour shade of the colour constituents, and / or size in the respective soil pattern.

[0074] According to the present invention, the colour constituents forming the respectively applied soil patterns classified C1 "fit for further circulation" and "unfit for further circulation" are applied to the banknote substrate by suitable means, preferably by printing technology means. The application process of the colour constituents, may synonymously be called "(artificial) soiling process".

[0075] Preferably, digital printing, like inkjet printing, is used to apply the colour constituents, preferably inks, as these techniques do not require the manufacturing of specific printing tools making adjustments / fine tuning of the soil template easier and quicker (especially fine and customized pattern change to control soil reproduction accurately). In particular when using CMYK inkjet printing, the inventive production method to form the respective soil templates is generally controlled through CMYK ratio, modulation type and coverage of the CMYK ink set. Preferred embodiments of each parameter are disclosed under the first inventive aspect as well as in the following.

[0076] According to an additive or alternative embodiment of the present invention, the parameter of colour modulation introduced into the soil template may be generated from a suitable halftoning technique, in particular a suitable halftoning printing technique. Accordingly, halftoning algorithms may be generated as artificially generated templates based on soil patterns of circulated banknotes. Different halftoning methods, such as error diffusion, ordered dithering optimization-based filtering, may be selected according to certain banknote sorting apparatus response properties, including selectivity and sensibility of banknote sorting apparatus response. Specific halftoning methods (error diffusion, ordered dithering, optimization-based filtering) may be considered to emulate predetermined soil templates associated to the different soil levels.

[0077] In addition, an "unfit" soiling level may be obtained by direct multilayer printing of the same soil template classified "fit for further circulation" in the following way: The soil template classified "fit" exhibiting a suitable low modulation and low optical density is used to make prints of the same template on the substrate by applying the soil template "fit" in register to increase the optical density and to form the applied soil pattern. In addition or alternatively, the same soil template "fit" is printed introducing a micro shift in x- and / or y-direction (a ΔXY with an inkjet printer) between the respective soil template prints to increase and create a new modulation as well as to increase optical density, so that the applied soil pattern including the combination of the printed soil templates then may be classified "unfit for further circulation".

[0078] As illustrated in Figs. 1A) to 1C), three different levels of modulation of an applied soil pattern are shown (1A) no modulation, 1B) modulation type 1, 1C) modulation type 2). The soil pattern 1A) exhibits no modulation of colour constituents and, thus, forms a smooth colour image representing a low soil level, which may be classified C1 as "fit for further circulation". The soil pattern 1B) of "modulation type 1" exhibits an increased modulation in comparison to the soil pattern 1A) of "no modulation", but a decreased modulation in comparison to the soil pattern 1C) of "modulation type 2". In general, the higher the modulation / spatial distribution of colour constituents, the higher is the correlated soil level. In the present case, the soil pattern 1C) of "modulation type 2" may be classified as C2 "unfit for further circulation". Of course, intermediate modulation types, such as of "modulation type 1" may be used to represent an intermediate soil scale / soil level, which may be classified either "fit for further circulation" or "unfit for further circulation" optionally dependent on the further parameters of colour coverage and colour shade. As an example, modulation types can be selected from error diffusion algorithm or algorithm using a dithering pattern, the latter providing a higher modulation type and, thus, the higher the soil level of the respectively applied soil pattern the less fit is the respectively applied soil pattern to be classified. Generally, suitable ink constituents, such as ink constituents of CMYK ink sets or other direct tints can be used as colour constituents.

[0079] Figs. 1D) and 1E) represent halftoned images of a 50 % greyscale image are represented, wherein the halftoned image in Fig. 1D) is prepared by error diffusion (modulation 2) and in Fig. 1E) is prepared by algorithm using a dithering pattern (modulation 3).

[0080] A further parameter to be defined according to the inventive production method is the colour constituent coverage, which is preferably associated to a defined modulation type. Preferably the colour constituent is represented by an ink, in particular an ink of a CMYK ink set or alternatively by a direct tint. As an example, the coverage of CMYK inks on artificially soiled banknotes generally varies in the range of up to 80%, preferably 20 to 70 %, more preferably 30 to 60 %, respectively based on the surface area of the banknote substrate. Generally, the higher the coverage, the higher the soil level of the respectively applied soil pattern and the less fit is the respectively applied soil pattern to be classified.

[0081] In Figs. 2A) to 2H, simplified images of four different colour coverage applications 2A) to 2D) are shown in relation to the respective modulation type 1 and simplified images of four different colour coverage applications 2E) to 2H) are shown in relation to the respective modulation type 2. In general, the higher the ink coverage for a predetermined modulation type of an applied soil pattern, the higher the soil level of the respectively applied soil pattern and the less fit is the respectively applied soil pattern to be classified. A balance between ink coverage and modulation is preferably predetermined for each soil level to increase the calibration performance. For example, the coverage of CMYK inks on artificially soiled banknote may be in the range of 10 to 80 %, preferably 20 to 70 % more preferably 30 to 60 %, respectively based on the surface area of the banknote substrate.

[0082] The spectral properties (colour shade) is defined by the ratio of the colour constituents used, in particular, when using CMYK inkjet printing, by the CMYK ratio. The CMYK ink ratio may represent for each C, M, Y and K respectively a ratio of ≤ 25, wherein the C ratio may be preferably in the range of less than 5, more preferably in the range of 1 to 3; wherein the M ratio may preferably be less than 20, more preferably 1 to 15; wherein the Y ratio may preferably 3 to 25; and wherein the K ratio may be preferably ≤ 2, preferably between 0 and including 1. Generally, higher the respective C, M, Y, and K ratio the higher the soil level of the respectively applied soil pattern and the less fit is the respectively applied soil pattern to be classified.

[0083] The spectral properties (colour shade) of the applied soil pattern is generally attached to the modulation type and ink coverage balance of the soil pattern. As shown in Figs. 3A) and 3B), two applied different soil patterns are illustrated exhibiting a low soil level colour shade 3A) and a high soil level colour shade 3B). In general, the lighter the colour shade, the lower the soil level. Preferably, for each soil level the spectral properties have to balance the targeted soil parameter to be detected by the banknote sorting apparatus while at the same time aligning the spectral properties of the artificially soiled banknote with a soiled reference banknote out of circulation. The spectral properties are generally represented by CIELAB coordinates of the colour of the applied soil pattern.

[0084] According to an additional or alternative embodiment, additional colours, like light magenta and light cyan, may optionally be used to optimize light soil colour encountered at low soil levels if necessary. Accordingly, the colour shade can be adjusted by a ratio of six different inks (CMYKLcLm).

[0085] According to an alternative embodiment, a direct tint approach is also suitable to obtain the necessary spectral properties. This alternative requires a specific ink, which emulates spectral properties of an applied soil pattern of a circulated banknote representing the respective soil level.

[0086] According to an additive or alternative embodiment of the present invention, an infrared (IR) property of an applied soil pattern of a circulated banknote may be emulated using one or more inks, which is / are transparent in the visible range of a human eye, preferably in the range of 380 nm to 700 nm, or inks having properties in visible range, preferably in the range of 380 nm to 700 nm, and in infrared (IR) range, preferably > 700 nm, in particular 700 nm to 1 µm. As an example, a direct tint ink may be used to emulate the IR property of an applied soil pattern.

[0087] According to an additive or alternative embodiment of the present invention, the colour constituent resistance is sufficiently robust in view of banknote sorting apparatus processing, in particular when applying the soil pattern to different banknote substrates, such as paper substrate, polymer substrate, composite substrate, polymeric substrate, varnished substrate. To increase the resistance of the colour constituent, a UV-curable ink, preferably a UV-curable inkjet printing ink is preferably used.

[0088] Additionally or alternatively, a protective layer of a varnish, preferably a transparent varnish may be applied on top of the soil pattern. Such an embodiment may reduce otherwise known printing ink pollution, e.g. from intaglio prints, generated by means, such as belts of a sorting apparatus in particular after several runs. Such a printing ink pollution may negatively affect the colorimetric properties of a soil test.

[0089] The colour constituent modulation, colour constituent coverage and colour constituent shade (spectral property) of an applied soil pattern of an artificially soiled banknote of a test deck of the present invention is preferably adjusted to emulate the colour modulation, colour coverage and colour shade of a soil pattern of a circulated banknote as reference.Example 1

[0090] The method of producing a test deck comprising two or more artificially soiled banknotes according to the first inventive aspect is described in the following on the basis of applying an inkjet-printed soil pattern on banknotes classified C1, in the present case non-circulated euro banknotes, to form an inventive test deck of the second inventive aspect, called "Soil Test Decks (Soil-TDs)", exhibiting twelve banknotes respectively exhibiting a different soil level.

[0091] As example the following table provides information on an artificially soiled test deck of banknotes: Soil level in test deck Modulation type Coverage % C M Y K 1------223001303230135042302690523228130635026907350271208360281409360211190103603112001136031120112360314251

[0092] In the above case, the banknote of soil level 1 relates to an unsoiled reference banknote, preferably a non-circulated reference banknote. The inventive soil test deck, however, may alternatively exhibit two, three, four, five, six, seven, eight, nine, ten, eleven or more than twelve soil levels.

[0093] With increase in soil level, the classification C1 of "fit for further circulation" is more and more challenged. Taken into account sorting machines / apparatus, which are calibrated using a manually chosen test deck, the above artificially soiled banknotes are to be classified as follows: Generally, soil levels 1 to 4 of above table are still to be classified C1 "fit for further classification". The soil levels 5 to 7, however, form a transition range, wherein dependent on the calibrated sorting equipment used, the respective soil level 5 to 7 would either still be classified C1 "fit for further circulation" or already classified C2 "unfit for further circulation". Soil level 8 and higher of above table respectively form artificially soiled banknotes, which are to be classified C2 "unfit for further classification".

[0094] The parameter "modulation type 2" relates to the modulation type of CMYK inks of the respectively applied soil pattern on the banknote substrate created by error diffusion algorithm. The property "modulation type 3" relates to the modulation type of CMYK inks of the respectively applied soil pattern on the banknote substrate created by an algorithm using a dithering pattern, wherein a defined image is used for pattern definition.

[0095] The parameter of "coverage" relates to the greyscale level before dithering, e.g. for an 8-bit greyscale image 0 % correlates to 1 and 100 % correlates to 256. After dithering the parameter of "coverage" corresponds to the ink coverage, i.e. the amount and / or area of respective ink applied to the banknote substrate area.

[0096] The properties of "C", "M", "Y", and "K" relates to the respectively defined coverage ratio of CMYK inks on artificially soiled banknote.

[0097] Figs. 4A) to 4D) illustrate four configurations for (digitally) printing two respective soil patterns SP1 and SP2 using one or more soil templates (ST, ST1, ST2, ST3, ... STN) on a banknote substrate 1. Accordingly, in Fig. 4A) the same soil template (ST1) is continuously repeated (Rc) two or more times independently in x / y direction of the banknote substrate11 forming the applied soil pattern SP1. In Fig. 4C) multiple (N times) different soil templates (ST1, ST2, ST3) are applied using continuous repetition (RC) to form the applied soil pattern SP2.

[0098] Figures 4B) / 4D) differ from figures 4A) / 4C) in that a discontinuous repetition (Rd) is used to apply the separate soil templates (ST1, ST2, ST3) in order to respectively form the applied soil patterns SP1 or SP2 on the surface of the banknote substrate 1, wherein the distance (d1, d2) between the respective soil templates may be the same or different.

[0099] In other words a soil level, which corresponds to C1 or C2 classification may be obtained by one or more of the four applied different soil patterns as respectively shown in Figs. 4A), 4B), 4C) or 4D).

[0100] In addition, a soiling level classified C2 "unfit for further circulation" may be obtained by direct multilayer printing of the same soil template classified "fit for further circulation" in the following way: The soil template classified "fit" exhibiting a suitable low modulation and low optical density is used to make prints of the same template on the substrate by applying the soil template "fit" in register to increase the optical density to form the applied soil pattern. In addition or alternatively, the same soil template "fit" is printed introducing a micro shift (a ΔXY with an inkjet printer) between the respective soil template prints to increase and create a new modulation and including an increased optical density, so that the applied soil pattern including the combination of the printed soil templates then may be classified "unfit for further circulation".

[0101] Fig. 5 illustrates a graph representing mean soil parameter values of 50 artificially soiled banknotes (y-axis) evaluated from a banknote sorting apparatus (BPS ®< M7, Giesecke & Devrient GmbH) as a function of twelve soil levels (x-axis) of respective artificially soiled banknotes of an inventive test deck. The graph outlines a quasi-linear behavior. As can be seen from the graph in Fig. 5, the inventive method of producing a test deck comprising artificially soiled banknotes can be suitably fine-tuned regarding the applied soil patterns of each soil level to achieve a linear correlation to the soil level scale of the artificially soiled banknotes of an inventive test deck. In particular, the test deck can be further optimized to improve linearity behavior by fine-tuning levels 3, 5 and 7.

[0102] The soil parameter may be measured and calculated differently from one sorting machine to another one (depending on the supplier and the machine type). In fact, the soil parameter can be based on an optical and / or / physical property of the soil or can be calculated as a constitution of different optical and / or physical properties. Examples of properties suitable to be used for this purpose are listed below: Absolute optical density, C, M, Y or K optical density or a combination thereof, M and Y densities are preferably considered. RGB imaging, wherein the blue channel is preferably considered, Optical modulation of the soil, mainly after greyscale conversion: mean value of an image associated to its standard deviation for example.

[0103] The colour spatial modulation / distribution of the colour constituents, the optical density of the colour constituents, and the spectral properties of the colour constituents are considered to define the applied soil pattern. This applied soil pattern is in that respect adjustable for one or several sorting machines while being consistent with the optical properties encountered in circulation.

[0104] Fig. 6 illustrates a graph representing mean soil parameter values as a function of soil level (x-axis) of an inventive test deck with artificially soiled banknotes using UV inkjet printing evaluated from a banknote sorting apparatus (BPS ®< M7, Giesecke & Devrient GmbH) after an endurance test 1, 51, 101 and 131 sorting runs in one orientation. Each soil level represents an artificially soiled banknote exhibiting an applied unique soil pattern. This test shows, that each of the artificially soiled banknotes of the inventive test deck demonstrates robustness of the soil parameter even after endurance testing.

[0105] According to Fig. 7A), a graph is illustrated representing the L* coordinates (L (luminance parameter) of CIELAB coordinate system (y-axis) as a function of twelve soil levels (x-axis) of an inventive test deck with artificially soiled banknotes. The goal is to demonstrate that the method is able to produce a test deck with optical properties (luminance in this case) representative of banknotes encountered in circulation, while keeping the sorting machine soil parameter also consistent with the banknote coming from circulation. Measurements were conducted on ELREPHO SE 070 (Lorentzen & Wettre) spectrophotometer for front side of artificially soiled banknotes of levels 1 to 12, selected aperture diameter is 34 mm (measurement on 30 mm) and consists of assessing a ROI of 700 mm 2< , white standard ceramic tile is used as background. A soil level classified C1 generally exhibits a higher L* value, preferably an L* value of 88 or higher, more preferably 90 or higher. A soil level classified C2 generally exhibits a lower L* value, preferably an L* value of less than 88, more preferably less than 87.

[0106] In comparison thereto, Fig. 7B) illustrates a graph representing the L* coordinate of CIELAB coordinate system (y-axis) as a function of the sorting machine apparatus for the 5 soil levels of a reference test deck selected from circulated soiled banknotes of the prior art. Measurements were also conducted on ELREPHO SE 070 (Lorentzen & Wettre) spectrophotometer for front side of reference test deck comprising circulated soiled banknotes with eight soil levels, selected aperture diameter is 34 mm (measurement on 30 mm) and consists of assessing a ROI of 700 mm 2< , white standard ceramic tile is used as background. Accordingly, a consistent behavior of the luminance parameter of the soil patterns of reference test decks from circulated banknotes versus inventive test deck of artificially soiled banknotes is confirmed: similar value ranges and quasi-linear behaviour. In particular in view of the reduced deviations between the inventive test decks and the increased life time, the inventive test decks are advantageous over the prior art test decks using the manually selected test decks of soiled banknotes.

[0107] The inventive test decks of artificially soiled banknotes were also tested in other sorting machines, such as FS1200 (Toshiba, JP), CPS2000 (Cash Processing Solutions, UK) and USF-200 (Glory, UK) and demonstrated consistent behaviours, even if soil detection algorithms are different.

Claims

1. A method for producing a test deck of artificially soiled banknotes, wherein at least one of the artificially soiled banknotes comprises a soil pattern classified with a soiling level (SL) C1 "fit for further circulation" and at least one of the artificially soiled banknotes comprises a soil pattern classified with a soiling level (SL) C2 "unfit for further circulation", characterized in that the method comprises or consists of the following steps: a) providing two or more banknotes being non-circulated banknotes and / or banknotes classified C1 "fit for further circulation", b) applying to one or more of the banknotes of step a) one or more colour constituents to form a soil pattern classified with a soiling level (SL) C1 "fit for further circulation", and c) applying to one or more of the banknotes of step a) one or more colour constituents to form a soil pattern classified with a soiling level (SL) C2 "unfit for further circulation", and wherein the applied soil patterns classified C1 and C2 are independently from each other composed of one or more, the same or different soil templates, and wherein the applied soil patterns classified C1 and C2 are different from each other and are respectively defined by colour spatial modulation / distribution of the colour constituents, optical density of the colour constituents, spectral properties of the colour constituents, and / or size of the respectively applied soil pattern.

2. The method of producing the test deck of artificially soiled banknotes according to claim 1, wherein the soiling level of the respectively applied soil patterns is further defined by one or more macroscopic properties emulating soil, stain, graffiti, de-inked banknote, tear, hole, mutilation, repair, crumple, limpness, folding line and / or gloss of a circulated banknote.

3. The method of producing the test deck of artificially soiled banknotes according to claim 1 or 2, wherein the one or more colour constituents are applied to the banknotes in step b) and / or c) by halftone application.

4. The method of producing the test deck of artificially soiled banknotes according to any one of claims 1 to 3, wherein the one or more colour constituents are applied to the banknotes in step b) and / or c) by a printing process, preferably by a digital printing process, such as inkjet printing process.

5. The method of producing the test deck of artificially soiled banknotes according to claim 4, wherein the one or more colour constituents in step b) and / or c) are represented by the constituents of a CMYK ink set.

6. The method of producing the test deck of artificially soiled banknotes according to claim 5, wherein the applied soil pattern is respectively defined by CMYK ink ratio, modulation type of CMYK inks on artificially soiled banknote and / or coverage ratio of CMYK inks on artificially soiled banknote.

7. The method of producing the test deck of artificially soiled banknotes according to any one of claims 1 to 6, wherein the one or more colour constituents in step b) and / or c) further comprise one or more inks comprising a UV property and / or one or more inks comprising an IR property.

8. The method of producing the test deck of artificially soiled banknotes according to any one of claims 1 to 7, wherein in step b) two or more different soil patterns classified C1 are applied to the banknote and / or wherein in step c) two or more different soil patterns classified C2 are applied to the banknote.

9. The method of producing the test deck of artificially soiled banknotes according to claim 8, wherein the applied different soil patterns respectively represent different soil levels.

10. The method of producing the test deck of artificially soiled banknotes according to any one of claims 1 to 9, wherein the applied soil pattern of step b) and / or the applied soil pattern of step c) is / are formed by using one or more UV-curing ink constituents.

11. A test deck of artificially soiled banknotes, wherein at least one of the artificially soiled banknotes comprises an applied soil pattern classified with a soiling level (SL) C1 "fit for further circulation" and at least one of the artificially soiled banknotes comprises an applied soil pattern classified with a soiling level (SL) C2 "unfit for further circulation", characterized in that the applied soil patterns classified C1 and C2 are independently from each other composed of one or more, the same or different soil templates, and wherein the applied soil patterns classified C1 and C2 are different from each other and are respectively defined by colour spatial modulation / distribution of the colour constituents, optical density of the colour constituents, spectral properties of the colour constituents, and / or size of the respectively applied soil pattern, preferably wherein the test deck is obtainable by a method according to any one of claims 1 to 10.

12. Use of a test deck of artificially soiled banknotes according to claim 11 characterized in that the test deck is used for calibrating and / or evaluating a sorting apparatus for banknotes.

13. A method for calibrating and / or evaluating performance of fitness sorting of a sorting apparatus for banknotes comprising or consisting of the following steps: a) providing a banknote sorting apparatus with a sorting device for sorting circulated banknotes into categories A1 "fit for further circulation" and A2 "unfit for further circulation", wherein the sorting device is in data communication with an evaluation device for evaluating whether a circulated banknote is fit or unfit for further circulation, wherein the evaluation device comprises a detector for detecting a parameter value representing the soiling level (SL) of the sorted banknote and a processing means for classifying the detected parameter value representing the soiling level of the sorted banknote into the category A1 or the category A2, b) providing a test deck of banknotes with two or more artificially soiled banknotes according to claim 11, wherein at least one of the artificially soiled banknotes comprises an applied soil pattern classified with a soiling level (SL) C1 "fit for further circulation" and at least one of the artificially soiled banknotes comprises an applied soil pattern classified with a soiling level (SL) C2 "unfit for further circulation", c) separately sorting the artificially soiled banknotes of the test deck of step b) with the banknote sorting apparatus of step a) and respectively detecting one or more parameter values representing the soiling level (SL) of the sorted artificially soiled banknotes with the detector of the evaluation device, and d) calibrating and / or evaluating performance of fitness sorting of the evaluation device by instructing the processing means to respectively correlate the detected one or more parameter values of the artificially soiled banknotes with a soiling level (SL) of a circulated banknote and to respectively categorize the detected one or more parameter values into category A1, in case the detected one or more parameter values correspond to a soil pattern classified C1, and to respectively categorize the detected parameter value into category A2, in case the detected one or more parameter values correspond to a soil pattern classified C2.

14. The method for calibrating and / or evaluating performance of fitness sorting of a sorting apparatus for banknotes according to claim 13, wherein the apparatus is further configured to detect one or more parameter values representing the soiling level selected from one, two, three or more parameters of the group consisting of colour modulation, optical density, spectral properties and / or size of the respectively applied soil pattern.

15. The method for calibrating and / or evaluating performance of fitness sorting of a sorting apparatus for banknotes according to claim 13 or 14, wherein the apparatus is further configured to detect one or more parameter values representing one or more macroscopic properties of the applied soil pattern, wherein the one or more macroscopic properties emulate soil, stain, graffiti, de-inked banknote, tear, hole, mutilation, repair, crumple, limpness, folding line and / or gloss of a circulated banknote.

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