SHEET RECOGNITION SYSTEM

A system within a self-service deposit terminal is arranged to recognize different denominations of bank notes. The system scans each side of a deposited note and produces a diffraction pattern of first one side and then the other side of the note. The diffraction pattern is compared against reference matched spatial filters associated with different denominations that are loaded into a Vander Lugt optical correlator. If the diffraction pattern and the matched spatial filter match then a correlation dot is produced, and if this occurs for both sides of a note then a denomination value can be assigned to that note. Reference matched spatial filters for all denominations of notes to be expected are first produced on a recording system and stored in a storage device which the self-service deposit terminal can access.