KNOW YOUR IRIS
The human Iris is an internal organ of the eye, protected by the eyelid, cornea and the aqueous humour. The iris is a thin circular diaphragm, which lies between the cornea and the lens of the human eye. The iris is perforated close to its centre by a circular aperture known as the pupil. The function of the iris is to control the amount of light entering through the pupil, and this is done by the sphincter and the dilator muscles, which adjust the size of the pupil. The average diameter of the iris is 12 mm, and the pupil size can vary from 10% to 80% of the iris diameter.
Iris is part of the middle coat of the eye and lies in front of the lens. It is the only internal organ of the body that is normally visible externally. Iris is considered the most unique and data rich physical structure on the human body. One of the key characteristics of iris is that the iris features remain constant throughout the years. The iris is composed from several layers. The lowest layer, epithelium layer, contains dense pigmentation cells. Next layer, stromal layer, contains blood vessels, pigment cells and the two iris muscles. The density of stromal pigmentation determines the colour of the iris. Among the visible features of an multi-layered iris are two zones, which often differ in colour. An outer ciliary zone and an inner pupillary zone, and these two zones are divided by the collarette – which appears as a zigzag pattern.
Because every iris is unique and it remains unchanged in clinical photographs. It was proposed to use the iris of the eye as a kind of optical fingerprint for personal identification. It works even when people wear sunglasses or contact lenses.
Some of the properties of the iris that enhance its suitability for use in automatic identification are:
· Immunity from the external environment
· Impossibility of surgically modifying without the risk of vision
· Physiological response to light
· Ease of registering its image at some distance
Images of the iris adequate for personal identification with very high confidence can be acquired from distances of up to about 3 feet (1 meter). The striated anterior layer covering the trabecular meshwork creates the predominant texture seen with visible light, but all of these sources of radial and angular variation taken together constitute a distinctive “fingerprint” that can be imaged from some distance.
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