Iris recognition

Iris recognition is a method of biometric authentication that uses pattern recognition techniques based on high-resolution images of the irides of an individual's eyes. Iris recognition uses camera technology, with subtle IR illumination reducing specular reflection from the convex cornea, This create images of the detail-rich, intricate structures of the iris. Converted into digital image, these images provide mathematical representations of the iris that yield unambiguous positive identification of an individual.
In Iris Scan Retinal scanning is actually done. Although retinal patterns may be altered in cases of diabetes glaucoma, retinal degenerative disorders or cataracts, the retina typically remains unchanged from birth until death. Due to its unique and unchanging nature, the retina appears to be the most precise and reliable biometric. Advocates of retinal scanning have concluded that it is so accurate that its error rate is estimated to be only one in a million.
The blood vessels within the retina absorb light more readily than the surrounding tissue and are easily identified with appropriate lighting. A retinal scan is performed by casting an undetectable ray of low-energy infrared light into a person’s eye as they look through the scanner's eyepiece. This beam of light outlines a circular path on the retina. Because retinal blood vessels are more sensitive to light than the rest of the eye, the amount of reflection fluctuates. The results of the scan are converted to computer code and stored in a database.

The idea for retinal identification was first conceived by Dr. Carleton Simon and Dr. Isodore Goldstein and was published in the New York State Journal of Medicine in 1935 . but in 1976, Robert "Buzz" Hill formed a corporation named EyeDentify, Inc., made a full-time effort to research and develop such a device. In 1978, the idea of a retinal scanner was patented, followed by a practical working prototype in 1981.

WORKING

An iris-recognition algorithm first has to identify the approximately concentric circular outer boundaries of the iris and the pupil in a photo of an eye. The set of pixels covering only the iris is then transformed into a bit pattern that preserves the information that is essential for a statistically meaningful comparison between two iris images. The mathematical methods used resemble those of modern lossy compression algorithms for photographic images.
Suppose in the case of Daugman's algorithms, a Gabour wavelet transform is used in order to extract the spatial frequency range that contains a good best signal-to-noise ratio considering the focus quality of available cameras. The result are a set of complex numbers that carry local amplitude and phase information for the iris image. In Daugman's algorithms, all amplitude information is discarded, and the resulting 2048 bits that represent an iris consist only of the complex sign bits of the Gabor-domain representation of the iris image. Discarding the amplitude information ensures that the template remains largely unaffected by changes in illumination and virtually negligibly by iris color, which contributes significantly to the long-term stability of the biometric template. To authenticate via identification (one-to many template matching) or verification (one-to one template matching) a template created by imaging the iris, is compared to a stored value template in a database. If the Hamming distance is below the decision threshold, a positive identification has effectively been made.
A practical problem of iris recognition is that the iris is usually partially covered by eye lids and eyelashes. In order to reduce the false-reject risk in such cases, additional algorithms are needed to identify the locations of eye lids and eyelashes, and exclude the bits in the resulting code from the comparison operation.

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Advantages

• It is an internal organ that is well protected against damage and wear by a highly transparent and sensitive membrane the CORNEA. This distinguishes it from fingerprints, which can be difficult to recognize after years of certain types of manual labor.
• The iris is mostly flat and its geometric configuration is only controlled by two complementary muscles (the sphincter pupillae and dilator pupillae), which control the diameter of the pupil. This makes the iris shape far more predictable than, for instance, that of the face.
• Some argue that a focused digital photograph with an iris diameter of about 200 pixels contains much more long-term stable information than a fingerprint.
• The iris has a fine texture that – like fingerprints – is determined randomly during embryonic gestation. Even genetically identical individuals have completely independent iris textures, whereas DNA (genetic "fingerprinting") is not unique for the about 1.5% of the human population who have a genetically identical monozygoic twin.
• An iris scan is similar to taking a photograph and can be performed from about 10 cm to a few meters away. There is no need for the person to be identified to touch any equipment that has recently been touched by a stranger, thereby eliminating an objection that has been raised in some cultures against finger-print scanners, where a finger has to touch a surface, or retinal scanning, where the eye can be brought very close to a lens.
• While there are some medical and surgical procedures that can affect the colour and overall shape of the iris, the fine texture remains remarkably stable over many decades. Some iris identifications have succeeded over a period of about 30 years.

Though this has many Limitations tooo

Limitations

• Iris recognition is very difficult to perform at a distance and if the person to be identified is not cooperating by holding the head still and looking into the camera.
• As with other photographic biometric technologies, iris recognition is susceptible to poor image quality.