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 Advantages |
A person's iris is fully
developed within 18 months after birth, and is protected by
eyelashes, eyelids and the retina. Its shape hardly changes so
that it has higher consistency compared to other biometric
characteristics.
Its higher uniqueness in shape than a
face or fingerprints ensures that an authentication system
using the iris is immensely reliable. |
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| Disadvantages |
- Invasive method.
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Equipment for scanning is costly. |
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| Personal identification using the iris is composed of two
parts: obtaining the iris image and recognizing it. Firstly,
the system performs the function of obtaining the iris image
suitable to iris recognition. The second part is comprised of
two stages: extracting the iris area from the image and
creating an iris code, and perform a match based on the iris
characteristics. |
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| Figure 4.2 above, briefly shows the process of extracting
the iris area from the eye image, splitting it, and creating
an iris code. |
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| Iris
Input Device |
| Obtaining an eye image from an
input device is the first stage of personal identification
using the iris. The device is comprised of a camera to capture
the image and lighting & image sensors to grab correct
iris patterns. In particular, the device is closely related to
the system's overall performance. General iris input devices
are using multi-wavelength infrared rays to prevent iris
patterns from being affected by external light. Unlike face
recognition, close-up photographing is required to obtain
appropriate resolution of the eye image since an eye is
smaller than a face. In the case of close-up photographing, it
is difficult to set a clear focus due to low depth of field.
To obtain a clear image, the shutter speed of a camera and
capture speed of an image sensor should be fast. The infrared
rays used to capture the iris image have low intensity, and
are known to be non-harmful to humans. The rays can be
usefully employed in the iris recognition system after
multiple trainings. However, from the users' point of view,
having their sensitive eyes scanned through the device could
be psychologically offensive. |
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| Iris
Area Extraction |
After capturing the eye image,
the iris area should be correctly extracted from it. Detecting
the inner boundary of the iris against the pupil and the outer
border of the iris against the sclera finishes the
process.
Both borders of the iris are determined by
approximating them into a circle based on the premise that
they are circle-shaped. For the circle detection, extract the
inner/outer boundaries of the iris after performing the
preprocessing on the eye image, or change "hoop
transformation" that is widely used for the detection of the
same-shape line. In general, a Circular Edge Detector is
commonly used. However, the outer boundary of the iris could
have a non-circular shape. At present, various kinds of
techniques are being used for more accurate detection of the
iris, and are being introduced in dissertations. |
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| Extraction and Matching of Iris
Features |
| The extraction of iris features
means capturing ring-shape patterns around the iris area.
Various extraction methods of iris-features were developed.
The feature extraction method using the Gabor Wavelet
transformation, which is commercialized and recognized for its
good performance, is introduced here. After the iris area is
extracted, the area is divided into 8 small ring areas as
shown in Figure 4.2. The gray values of the iris patterns are
calculated clockwise or counter-clockwiseand the iris feature
data in actual use can be obtained through the Gabor Wavelet
Transformation of the value. |
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