Currency validator

A method of deriving a classifying function for classifying items of currency, the method comprising deriving a plurality of measurements from at least one currency sensor and a plurality of items, and forming a set of data from the measurements, the elements of the data set corresponding to points in a first space, selecting a kernel function corresponding to a mapping of the first space to a second space, the method comprising selecting a subset of the data set where the subset is such that the image of the subset under the mapping in the second space is representative of the image of the data set under the mapping in the second space.

A method as claimed in any preceding claim wherein individual elements of the data set comprise a plurality of measurements corresponding to a plurality of characteristics of the sensed items.

A method as claimed in any preceding claim wherein the currency sensor is a document sensor.

A method as claimed in any preceding claim wherein the kernel function is a Gaussian, polynomial, sigmoid, hyperbolic tangent or spline kernel.

A method of deriving a function for a currency validator using at least one currency sensor, the method comprising deriving a plurality of measurements from at least one currency sensor and a plurality of items and forming a data set from the measurements, the elements of the data set corresponding to points in a first space, determining a further set of values corresponding to the measured values, choosing a kernel function corresponding to a mapping of the first space containing the measurements to a second space, and deriving an expression representing the function in terms of the kernel function.

A method of deriving a function for a currency validator using at least one currency sensor, the method comprising deriving a plurality of measurements from at least one currency sensor and a plurality of items and forming a set of the measurements, determining a further set of values corresponding to the measured values, wherein there is a non-linear relationship between the set of measurements and the further set of values, in a first space, and deriving an expression of the non-linear relationship in the first space by performing a regression on the image of the data under a mapping in a second space.

A method of adapting a currency validator comprising storing a classifying function involving constants representing regression and a kernel function.

A method of classifying a currency item in a currency classifier comprising deriving at least one measurement of the item from a currency sensor, and using an expression involving regression and a kernel function to classify the currency item.

A currency validator comprising means for sensing currency items to produce measured values representing characteristics of the items, means storing constants representing regression and a kernel function, which together represent a non-linear function.