Biometric systems can seem complicated, but they all use the same three steps. The first time you use a biometric system, it records basic information about you, like your name or an identification number. It then captures an image or recording of your specific trait. Then the system analyzes your trait and translate it into a code or graph. The next time you use the system, it compares the trait you present to the information on file. Then, it either accepts or rejects that you are who you claim to be.
Fingerprint Recognition involves taking an image of a person's fingertips and records its characteristics like whorls, arches, and loops along with the patterns of ridges, furrows, and minutiae.
Vascular Pattern Identification uses a nonharmful near infrared light to produce an image of one's vein pattern in their face, wrist, or hand, as veins are relatively stable through one's life. It is a non-invasive, computerized comparison of shape and size of subcutaneous blood vessel structures. The vein "tree" pattern, picked up by a video camera, is sufficiently idiosyncratic to function as a personal code that is extremely difficult to duplicate or discover.
Face recognition technique records face images through a digital video camera and analyses facial characteristics like the distance between eyes, nose, mouth, and jaw edges. These measurements are broken into facial planes and retained in a database, further used for comparison. Face recognition offers advantages in terms of convenience and hygiene. Nowadays it is very reliable.
Iris recognition analyzes features like rings, furrows, and freckles existing in the colored tissue surrounding the pupil. The scans use a regular video camera and works through glasses and contact lenses. The image of the iris can be directly taken by making the user position his eye within the field of a single narrow-angle camera. This is done by observing a visual feedback via a mirror. The isolated iris pattern obtained is then demodulated to extract its phase information. As far as known this technique cannot be manipulated.