As part of my PhD research, I am working on extending the depth-of-field of iris recognition cameras. In a series of blog posts (in the near future) I would like to share some of the things that I have learnt during the project. This post, the first one in the series, is an introduction to iris recognition biometric technology. I believe the material presented here could benefit someone new to iris recognition get a quick yet comprehensive overview of the field. In the following paragraphs, I have described the iris anatomy, and what makes it so special as a biometric technology, followed by the general basis of iris based verification, and the four major constituents of a general iris recognition system.
The human iris is the colored portion of the eye having a diameter which ranges between 10 mm and 13 mm [1,2]. The iris is perhaps the most complex tissue structure in the human body that is visible externally. The iris pattern has most of the desirable properties of an ideal biomarker, such as uniqueness, stability over time, and relatively easy accessibility. Being an internal organ, it is also protected from damage due to injuries and/or intentional fudging . The presence or absence of specific features in the iris is largely determined by heredity (based on genetics); however the spatial distribution of the cells that form a particular iris pattern during embryonic development is highly chaotic. This pseudo-random morphogenesis, which is determined by epigenetic factors, results in unique patterns of the irises in all individuals including that of identical twins [2,4,5]. Even the iris patterns of the two eyes from the same individual are largely different. The diverse microstructures in the iris that manifest at multiple spatial scales  are shown in Figure 1. These textures, unique to each eye, provide distinctive biometric traits that are encoded by an iris recognition system into distinctive templates for the purpose of identity authentication. It is important to note that the color of the iris is not used as a biomarker since it is determined by genetics, which is not sufficiently discriminative.