Iris is the pigmented screen present in front of the lens of eye. The black melanin pigment in it prevents the entry of harmful rays and restricts the entry of light into the retina. The melanin in the iris consists of two distinct macro molecules called Eumelanin which is brown black in colour and Phenomelanin which is yellow-reddish in colour. The pattern in the Iris is complex and unique that can be used as an identity mark. Biometric method of identification uses the Iris recognition system to record the image of the Iris. The system uses infrared illumination to acquire images of the detailed rich intricate patterns of the iris. Digital template obtained from the iris pattern through mathematical and statistical algorithms allow the identification of an individual because iris pattern is more unique than the finger print.
Iris is the most suitable part of the body to use to prove the identity because it is a well protected part and has unique pattern and is flat in shape. The Iris has a fine texture that like fingerprints is genetically determined and form during development. The fine texture of iris never changes for years so that once the biometric is taken, that can be used for many years.
The Iris scanner uses a CCD (Charge Coupled Device) digital camera that uses both visible and near infrared rays. It takes a clear and high contrast image of the iris. When using near infrared, the pupil appears as dark so that the iris can be easily distinguished by the computer. When we look into the biometric camera, it focuses automatically and the connected computer will locate the center of pupil, edge of the pupil, edge of the iris etc. From the image, the computer will make a digital image of the iris. The Iris recognition system is then used to identify the person through the iris image.
Most of the biometric system used for Iris recognition takes the image of the iris using visible light rays or near infrared of 700 to 900 nanometers. Each wavelength of Near Infrared (NIR) and visible light distinguishes the features of the iris like texture, pigment pattern, amount of pigment etc. Most of the Iris recognition system uses Infrared spectrum because the IR ray can penetrate the heavily pigmented iris of majority of populations. Infrared also reduces the chance of corneal reflection of light.
In the operation, the system uses Algorithm to localize the inner and outer boundaries of the Iris in an image of the eye. Secondly, it excludes the other parts of the eye except the iris. The set of pixels containing the iris pattern is then analyzed to extract the bit pattern encoding the information necessary for comparing two iris.