1. A method for detecting an extent of deterioration of a bill, comprising: generating at least one transmitted light image and at least one reflected light image of the bill; determining at least one disorder curve length for at least some of the at least one transmitted light image and at least some of the at least one reflected light image; determining at least one evaluation factor for at least some of the at least one transmitted light image and at least one evaluation factor for at least some of the at least one reflected light image based on the determined disorder curve lengths; and determining the extent of deterioration of the bill based on at least some of the determined evaluation factors.