Iris Recognition

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Iris Recognition

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John Daugman

• There is only one iris recognition algorithm in
  use
• The algorithm was developed mainly by John
  Daugman, PhD, OBE
• www.CL.cam.ac.uk/users/jgd1000/
• It is owned by the company Iridian Technologies

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Advantages of Iris Recognition

• Irises do not change with age unlike faces
• Irises do not suffer from scratches, abrasions,
  grease or dirt unlike fingerprints
• Irises do not suffer from distortion unlike
  fingerprints

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Finding the Iris in the Image

• It is easy to find the circular boundaries of the
  iris

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Masking

• The boundaries of the eyelids can be found
• Eyelashes and specularities (reflections) can be
  found
• These areas can be masked out

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Gabor Wavelets
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Gabor Wavelets

• Gabor Wavelets filter out structures at different
  scales and orientations
• For each scale and orientation there is a pair of
  odd and even wavelets
• A scalar product is carried out between the
  wavelet and the image (just as in the Discrete
  Fourier Transform)
• The result is a complex number

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Phase Demodulation

• The complex number is converted to 2 bits
• The modulus is thrown away because it is
  sensitive to illumination intensity
• The phase is converted to 2 bits depending on
  which quadrant it is in

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IrisCodes

• This process is carried out at a number of points
  throughout the image.
• The result is 2048 bits which describe each iris
  uniquely
• Two codes from different irises can be compared
  by finding the number of bits different between
  them this is called the Hamming distance
• This is equivalent to computing an XOR between
  the two codes. This can be done very quickly
• To allow for rotation of the iris images the
  codes can be shifted with respect to each other
  and the minimum Hamming distance found

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Hamming Distance
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Binomial Distribution

• If two codes come from different irises the
  different bits will be random
• The number of different bits will obey a binomial
  distribution with mean 0.5

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Identification

• If two codes come from the same iris the
  differences will no longer be random
• The Hamming distance will be less than expected
  than if the differences were random
• If the Hamming distance is lt 0.33 the chances of
  the two codes coming from different irises is 1
  in 2.9 million
• So far it has been tried out on 2.3 million
  people without a single error

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More Advantages of IrisCodes

• IrisCodes are extremely accurate
• Matching is very fast compared to fingerprints or
  faces
• Memory requirments are very low only 2048 bits
  per iris

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• Disadvantages of the Iris for Identification
• Small target (1 cm) to acquire from a distance (1
  m)
• Moving target ...within another... on yet another
  
• Located behind a curved, wet, reflecting surface
• Obscured by eyelashes, lenses, reflections
• Partially occluded by eyelids, often drooping
• Deforms non-elastically as pupil changes size
• Illumination should not be visible or bright
• Some negative (Orwellian) connotations

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Fake Iris Attacks
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Fake Iris Fourier Spectrum

• Due to the dot matrix grid the Fourier Spectrum
  of the fake iris has 4 extra points

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