Several stages of processing occur once you capture image. The second stage is to identify the fingerprint from a database. Each sensor vendor uses various proprietary algorithms, but the basic process is to compare templates and look for a best match. Because of the varying conditions under which they are captured, images do not perfectly match the minutiae characteristics saved in the database for each person who is to be recognized. Therefore, each algorithm usually has a parameterized tolerance for error that allows you to set the level of security.
Security is measured as false accepts and false rejects.
A false accept is when a system recognizes a person's fingerprint it shouldn't have or when it recognizes the fingerprint as belonging the wrong person. A false reject is when a system rejects a valid fingerprint. The fewer the false accepts, the greater the number of false rejects. This relationship occurs because, to prevent false accepts, you must tighten tolerances, and captured images must more closely match the saved signature template in the database. The tightened tolerances, however, tend to cause the system to fail to recognize valid prints.