Biometric can be any information that is contained in a natural body. We select the types of biometric that is unique to each person and can be easily presented for security purposes.
Okay, that was a long way to saying things such as fingerprints, irises, veins, hand geometry, facial features, and the list goes on. Which biometric information shall we use and when shall we use it? That question has many answers, but here are some basic ideas based on our practical experience.
1) Fingerprints: for in-door, where lighting interference can be controlled, optical based fingerprint readers serve most purposes; for out-door, capacitance based fingerprint readers is better than their optical counterpart due to high lighting interference and the possibility of dirt scratches. Further more, fingerprint has a major advantage in alarm reporting when you are under duress. You can present your pre-configured duress fingerprint and report an alarm without alerting the criminal.
2) Irises: we did not have good experience with iris based biometric access device: a. the device needs an optimal distance between your eyes and the device, so in practice, we have to tilt our heads in order to gain access; b. people with glasses on will have a higher rate of false negative; c. the device is generally quite large and limits their application; d. expensive for no apparent advantages.
3) Veins: this type of device reads the shapes of the veins in your fore arm. We see no practical advantage over the above, and they are very expensive.
4) Hand geometry: this type of device reads the shape of your hand that is structured by your hand bones. The device is very large in size but is very good when the working environment is harsh. Such device is generally very durable and resistant to natural interference. One observed drawback, when applied in outdoor environment, would happen when the temperature of any given day is very cold or very hot. During those times, the hand geometry of a person changes slightly, and the device becomes prone to giving false negatives.
5) Facial features: face is not exactly unique due to the possibilities of identical twins. These devices are usually used for non-critical high traffic areas and when guards are present.
For other less commonly used biometric information, we need to discuss in-depth in order to justify its use.