Method and apparatus for the determination of classification parameters for the classification of bank notes

1. A method for the determination of a set of classification parameters for the classification of bank notes in different classes by means of a bank note processing apparatus, wherein the method comprises the following steps:

sensing measurement data for a plurality of reference bank notes having known properties by means of a sensor device of the bank note processing apparatus, at least some of the reference bank notes being provided with at least one adhesive strip, wherein the at least one adhesive strip has a color different from at least one color of a background of one of the plurality of reference bank notes in the surrounding of the at least one adhesive strip, such that a color of the at least one adhesive strip corresponds to a known adhesive strip size;

determining a set of classification parameters;

ascertaining the distribution of the plurality of reference bank notes over the different classes on the basis of the measurement data of the reference bank notes and the set of classification parameters;

comparing the distribution over the different classes, which was determined for the plurality of reference bank notes, with the optimal distribution of the reference bank notes over the different classes, which was ascertained from the known properties of the plurality of reference bank notes; and

if the two distributions deviate from each other, adjusting the set of classification parameters until the distribution of the plurality of reference bank notes over the different classes, which was determined on the basis of the measurement data of the reference bank notes and the changed set of classification parameters, and the optimal distribution of the reference bank notes over the different classes, which was ascertained from the known properties of the plurality of reference bank notes, no longer deviate from each other or the deviation between these distributions is acceptable.

2. The method according to claim 1 , wherein for the determination of the deviation between the distribution of the plurality of reference bank notes over the different classes, which was determined on the basis of the measurement data of the reference bank notes and the set of classification parameters, and the optimal distribution of the reference bank notes over the different classes, which was ascertained from the known properties of the plurality of reference bank notes, there is employed a distance measure which must be minimized.

3. The method according to claim 1 , wherein the measurement data sensed for a plurality of reference bank notes by the sensor device of the bank note processing apparatus comprise both optical measurement data, in particular image data, of the reference bank notes, which were sensed by means of an optical sensor unit of the sensor device, and measurement data sensed by means of an ultrasonic sensor unit of the sensor device.

4. The method according to claim 1 , wherein the reference bank notes provided with an adhesive strip are configured such that these reference bank notes contain additional information items for the determination of a classification parameter relating to the measurement data of an ultrasonic sensor unit, which information items can be ascertained by means of the optical sensor unit and can be employed for the determination of the classification parameter relating to the measurement data of the ultrasonic sensor unit.

5. The method according to claim 4 , wherein the adhesive strips on the reference bank notes are configured occupying different areas on the reference bank notes and having different colors, so that between the area and the color of an adhesive strip there exists a unique assignment which is employed for deriving the area of an adhesive strip due to its color.

6. The method according to claim 4 , wherein the reference bank notes with an adhesive strip have the additional information items for the determination of a classification parameter relating to the measurement data of the ultrasonic sensor unit, which information items can be ascertained by means of the optical sensor unit and can be employed for the determination of the classification parameter relating to the measurement data of the ultrasonic sensor unit, in the form of a numeric string, a denomination, a graphical motif, a barcode, or the like.

7. The method according to claim 4 , wherein the additional information items for the determination of a classification parameter relating to the measurement data of the ultrasonic sensor unit, which are deposited on the reference bank notes such that these can be ascertained by means of the optical sensor unit and can be employed for the determination of the classification parameter relating to the measurement data of the ultrasonic sensor unit, contain information items about the area, the position, the thickness, the extension, the form of an adhesive strip and/or the number of adhesive strips on a reference bank note.

8. A method for classifying bank notes, wherein the method comprises the following steps:

determining at least one quantitative property of a bank note to be classified; and

classifying the bank note to be classified on the basis of the quantitative property of the bank note to be classified and of classification parameters, the classification parameters having been determined with the method according to claim 1 .

9. An apparatus for processing value documents, in particular bank notes, wherein the apparatus comprises:

a sensor device for generating measurement data for a plurality of reference bank notes having known properties, at least some of the reference bank notes being provided with at least one adhesive strip, wherein the at least one adhesive strip has a color different from at least one color of a background of one of the plurality of reference bank notes in the surrounding of the at least one adhesive strip, such that a color of the at least one adhesive strip corresponds to a known adhesive strip size;

a control and evaluation device, wherein the control and evaluation device is configured to carry out the following steps:

determining a set of classification parameters;

ascertaining the distribution of the plurality of reference bank notes over the different classes on the basis of the measurement data of the reference bank notes and the set of classification parameters;

comparing the distribution over the different classes, which was determined for the plurality of reference bank notes, with the optimal distribution of the reference bank notes over the different classes, which was ascertained from the known properties of the plurality of reference bank notes; and

if the two distributions deviate from each other, adjusting the set of classification parameters until the distribution of the plurality of reference bank notes over the different classes, which was determined on the basis of the measurement data of the reference bank notes and the changed set of classification parameters, and the optimal distribution of the reference bank notes over the different classes, which was ascertained from the known properties of the plurality of reference bank notes, no longer deviate from each other or the deviation between these distributions is acceptable.