Integro-Differential Operator
Definition
Daugman's boundary-detection method: it maximises the magnitude of the line-integral intensity gradient around circular paths, locating the pupillary and limbic boundaries of the iris in near-infrared eye images.
- Author
- John Daugman
- Function
- Locates pupillary and limbic iris boundaries
- Method
- Maximises line-integral intensity gradient over circular paths
- Input imagery
- Near-infrared eye images
- Used in
- Aadhaar and DOD iris deployments
Common questions
Why does the operator search over circular paths instead of straight edges?+
The pupil and iris boundaries are approximately circular, so testing circular contours of varying radius and centre lets the operator find the exact circle where the intensity gradient jumps most sharply, marking the true boundary.
What happens if eyelids or lashes occlude part of the boundary?+
Partial occlusion can bias the fitted circle if not handled. Practical implementations mask occluded regions before or after boundary fitting so eyelid and eyelash interference does not distort the located pupillary or limbic circle.
Related terms
- DOD ABIS
- US Department of Defense Automated Biometric Identification System, administered by the Defense Forensics and Biometrics Agency, holding iris, fingerprint, face and DNA...
- Hamming Distance (HD)
- The fraction of bit positions where two IrisCodes disagree, computed only over mutually unmasked bits. Genuine pairs centre around HD 0.10-0.15; impostor...
- HIIDE
- Hand-held Interagency Identity Detection Equipment: a handheld iris and fingerprint capture device used by US military forces in Iraq and Afghanistan for...
- IrisCode
- The 2048-bit binary template produced by quantising the phase of 2D Gabor wavelet responses across the normalised iris strip. Phase encoding provides...
- NIST IREX
- NIST Iris Exchange: the series of iris recognition algorithm evaluations conducted by the National Institute of Standards and Technology since 2009, providing...
- Puttaswamy V. Union of India (2018)
- Supreme Court of India judgment upholding Aadhaar's constitutional validity while classifying iris and other biometric data as sensitive personal information within the...
- Rubber-Sheet Model
- The coordinate transform that maps the annular iris region (between pupillary and limbic circles) to a normalised rectangular strip of fixed dimensions,...
- UIDAI
- Unique Identification Authority of India, the statutory body created by the Aadhaar Act 2016 that operates the world's largest biometric identity system,...
- Usable Bit Fraction
- The proportion of IrisCode bits not masked for eyelid, eyelash, or specular reflection occlusion. Values below 0.7 reduce match confidence; values below...