Biometrics is a method to verify the identity of a person based on psychological characteristics or behavioral characteristics. Examples of biometrics are fingerprints, iris, face, ear, voiceprint, palm print, signature, and handwriting or keystrokes patterns. Biometric systems are classified into two types: (1) Unimodal biometric system (2) Multimodal biometric system. There is a limited accuracy in the unimodal biometric system. Accuracy can be improved by using multimodal biometric system. Two or more biometric traits are used in multimodal biometric system. Here we present characteristics of biometrics, comparison of biometric modalities, difference between unimodal and multimodal biometrics, limitations of unimodal biometrics, fusion levels in biometrics.

Keywords : Biometrics, Unimodal biometrics, Multimodal biometrics, Fusion levels, Recognition methods.