Iris Scanning

Iris Scanning

Iris is the colored portion of the eye consists of over 400 distinguishing characteristics that can be used to identify an individual. However only 260 of these characteristics, like contraction furrows, filaments, striations, crypts, freckles, etc. captured in iris identification process can be used.

The properties of iris that enhance its suitability for use in identification system are:

* Its inherent isolation and protection from external environment.

* Impossibility of surgical modification.

* Response to light (Providing natural test against artifice).

Iris scanning is the less intrusive of the eye related biometrics. It utilizes a conventional camera element and requires no intimate contact between user and reader.

Fig: 1 Iris: Anatomy and Properties

Iris scan's strengths:

* It also has the potential for higher than average template matching performance.

* It has been demonstrated to work with spectacles in place and with a variety of ethnic groups and is one of the few devices that can work well in identification mode.

* It has potential for exceptionally high levels of accuracy.

* It maintains stability of characteristics over a lifetime.

* Individual's right and left eyes are different and that patterns are easy to capture making iris scan resistant to false matching and fraud

Iris Scan's Weaknesses:

* Acquisition of the image requires moderate training and attentiveness.

* It has propensity for false rejection.

* Proprietary acquisition device is necessary for deployment

* There is some user discomfort with eye based technology

Iris Scan: Working

The iris eye processing proceeds with taking a photograph from a specialized camera. The camera is placed at a distance of approximately 3ft. and uses infrared imager to illuminate the eye and capture a very high-resolution photograph.

Eyeglasses and contact lenses present no problems to the quality of the image and the iris scan systems and the live eye by checking for the normal continuous fluctuations in the people's eye.

In identifying one's iris, there are 2 types of methods that are used: passive and active. The active iris requires the user to move back and forth so that the camera can adjust and focus in on the user's iris.

The passive iris system is different in that it incorporates a series of cameras that locate and focus on the iris. This method provides a much more user-friendly experience.

After the iris system has one's iris in focus, it overlays a circular grid on the image of the iris and identifies where areas of light and dark fall. The purpose of overlaying the grid is so that the iris systems can recognize a pattern within the iris and to generate 'points' within the pattern into an 'eye print'. Finally, the captured image is checked against a previously stored reference template in the database.

Image Processing

The inner edge of the iris is located by the iris scan algorithm, which maps the iris' distinct patterns and characteristics. once the parameter of the iris have been defined, a black and white image of the iris is used for feature extraction. The area used for feature extraction is a horizontal band extending from the far left to the far right of the iris.

Distinctive features

The patterns that constitute the visual component of the iris are surprisingly distinctive. A primary visible characteristic is known as the trabecular meshwork, a tissue that gives the appearance of dividing the iris in a radial fashion.

Iris scan algorithms map segments of the iris into hundreds of independent vectors. The characteristics from iris features are the orientation and the spatial frequency of distinctive areas along with the position of these areas

Template Creation

The vectors located by the iris scan algorithm are used to form enrollment and match templates, which are generated in hexadecimal format.

Template Matching

Iris scan solutions generally perform identification as opposed to verification, meaning that the match template is compared against all system enrollments to find the best match

References

· Biometrics By:-

Samir Nanavati, Michael Thieme, Raj Nanavati

· www.ieee.org