**2. Recognition by iris**

The *iris* is the colored part of the eye that we can see in others at a glance. The iris controls the amount of light that enters the eye, resembling a camera aperture that has the task of controlling the amount of light passing through the lens. The black hole in the center of the iris is called *pupil*. The iris is associated with fine muscles that either enlarges or narrows the iris. The color, texture, and pattern of the iris are different for each person, which is analogous to fingerprints, for example. However, the likelihood of finding two identical irises is much smaller than fingerprints.

The *clamping muscle* lies along the edge of the iris and pulls the iris in a stronger light. The *stretching muscle* lies transversely, similar to the bicycle strand, and stretches the iris when in dimmer illumination. The iris is flat and divides the eye into the front and back parts. **Figure 1** shows the anatomy of the human eye and the location of its individual parts.

The color of the iris is caused by a pigment called *melanin*. It is located between the pupil and the eye sclera. The size of the iris is about 11 mm. Its visual texture originates from the third month

**Figure 1.** Anatomy of the human eye [2].

• The *front chamber* is filled with intraocular fluid, which is constantly refreshed.

rows/enlarges the pupil.

8 Machine Learning and Biometrics

• The *vitreous* fluid fills the inside of the mesh.

the eye.

the front.

a camera.

(CNS).

**2. Recognition by iris**

• The *iris* has the shape of an annulus, and it is a circularly arranged musculature that nar-

• The *pupil* is an opening in the middle of the iris, regulating the amount of light coming into

• The *lens* is suspended on the ciliary body and has the ability to bend and thereby change the refractive index. If the lens loses this ability, the eye cannot accommodate (focus).

• *Sclera* is a white visible layer covering the entire eyeball, which passes into the cornea in

• The *retina* is the inner part containing cells sensitive to light. It shows the image, much like

• The *optic nerve* carries a large number of nerve fibers that enter the central nervous system

There are two scientific lines that deal with eye characteristics—those are *ophthalmology* and *biometrics*. *Ophthalmology* is a medical discipline aimed at analyzing and treating the health of the eye and its associated areas. The concept of *iridology* (the branch of alternative medicine that deals with the diagnosis of a person's health according to the image of the eye iris) is given only for completeness. In the field of *biometrics* (recognizing a person based on the unique biometric characteristics of the human body), the unique properties of the eye are not subject to change in time, and they are also so unique that it is possible to unequivocally identify two

distinct individuals apart from each other in order to verify the identity of that person.

The *iris* is the colored part of the eye that we can see in others at a glance. The iris controls the amount of light that enters the eye, resembling a camera aperture that has the task of controlling the amount of light passing through the lens. The black hole in the center of the iris is called *pupil*. The iris is associated with fine muscles that either enlarges or narrows the iris. The color, texture, and pattern of the iris are different for each person, which is analogous to fingerprints, for example. However, the likelihood of finding two identical irises is much smaller than fingerprints.

The *clamping muscle* lies along the edge of the iris and pulls the iris in a stronger light. The *stretching muscle* lies transversely, similar to the bicycle strand, and stretches the iris when in dimmer illumination. The iris is flat and divides the eye into the front and back parts. **Figure 1**

The color of the iris is caused by a pigment called *melanin*. It is located between the pupil and the eye sclera. The size of the iris is about 11 mm. Its visual texture originates from the third month

shows the anatomy of the human eye and the location of its individual parts.

of pregnancy and forms during the first 2 years of life [4]. The basic structure remains unchanged during life, and even in twins, the iris is unique. The structure of the iris is shown in **Figure 2**.

The surface of the iris is quite complex. John Daugman described the 250 features that the iris contains. The most important of which for identification are the following:

