Iris Imaging Focus via Corneal Glint Curve Fit
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Solution Overview
Problem
Existing iris imaging systems face challenges in quickly focusing on the iris for biometric identification, particularly with uncooperative subjects, due to the need for complex image analysis algorithms and high computational resources, which can lead to recaptures caused by blinking or movement.
Innovation Solution
A method and system that rapidly calculate an estimated focal point for the iris by capturing test images at various measurement positions, using a curve fit to defocus measurements, and focusing on the corneal glint as a primary feature, allowing for quick and efficient image capture without intensive processing, utilizing a liquid lens for fast focus adjustment and infrared illumination for enhanced resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex image analysis algorithms are used to focus on the iris, then focusing accuracy is improved, but processing time increases and productivity decreases
Solution Approach 1:
The patent extracts and isolates the corneal glint as a specific feature from the entire iris image. By focusing only on the corneal glint position rather than analyzing the entire iris structure, the system achieves accurate focusing without requiring complex image analysis algorithms, thus resolving the contradiction between focusing accuracy and processing speed
Solution Approach 2:
The system performs preliminary detection of the corneal glint position before final image capture. By pre-identifying the corneal glint as the reference point for focusing, the system eliminates the need for complex post-capture analysis, enabling both rapid processing and accurate focusing
2Measurement precision
If complex image analysis algorithms are used to focus on the iris, then focusing accuracy is improved, but computational resources increase
Solution Approach 1:
The patent extracts and isolates the corneal glint as a specific feature from the entire iris image. By focusing only on the corneal glint position rather than analyzing the entire iris structure, the system achieves accurate focusing without requiring complex image analysis algorithms, thus resolving the contradiction between focusing accuracy and processing speed
Solution Approach 2:
The system uses a simple, computationally inexpensive method (corneal glint detection) instead of expensive complex algorithms. The corneal glint serves as a temporary reference point that is easily detected and discarded after focusing, requiring minimal computational resources
3Illumination intensity
If multiple illumination sources are used to flood the ocular area, then illumination uniformity is improved, but system complexity increases
Solution Approach 1:
The patent applies illumination with specific local quality characteristics - using infrared wavelength illumination that is optimized for penetrating iris pigmentation. This targeted approach achieves uniform illumination of the ocular area while maintaining relatively simple system architecture, as the illumination properties are optimized for the specific imaging goal rather than using complex multi-source arrangements
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables rapid capture of focused iris images in approximately 0.3 to 1.2 seconds, regardless of subject distance or cooperation, reducing the need for recaptures and minimizing computational resources, while maintaining high spatial resolution for biometric identification.
Implementation Method 1
utilizing a liquid lens for fast focus adjustment
Implementation Method 2
utilizing a liquid lens for fast focus adjustment and infrared illumination for enhanced resolution
Implementation Method 3
focusing on the corneal glint as a primary feature
Data Source
AI summary
Methods and systems describe calculating an estimated focal point for a feature of interest within an ocular area of a subject using acquired test images and focal points. A curve is approximately fit to the defocus measurements located at different focal points. A maximum of the curve is identified that corresponds to an estimated focal point of the subject's iris. An image capture device can then record an approximately focused image of the iris using the estimated focal point. This reduces the time and computing resources needed to capture an image iris that is in focus where the subject may be located at a variable, unknown standoff distance. These methods and systems can be used for biometric identification using iris imaging, among other applications where quickly focusing an imaging system is advantageous.