US Patent 8739954 Characterizing items of currency

Characterizing an item of currency employs a validation apparatus that includes at least three specified light sources for illuminating the item of currency. Each of the specified light sources has an emission spectrum similar to an approximating function for reconstructing a predetermined set of spectrum. At least one receiver receives light emitting from the at least three specified light sources. A transportation unit transports the item of currency within the validation apparatus. The light received by the receiver is at least one of light reflected by or light transmitted through the item of currency.