Eye-safe NIR Illumination Control for Biometric Imaging
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Solution Overview
Problem
Current NIR imaging technologies for biometric identification, such as iris recognition, face recognition, and combined systems, face challenges in ensuring eye safety while maintaining effective illumination, as high-intensity NIR light can damage retinal cells and existing systems often require subjects to be within close proximity and directly aligned, limiting distance and comfort.
Innovation Solution
An eye-safe NIR optical imaging method that determines the maximum permissible illumination level based on captured images, using a controller to adjust NIR light pulses to ensure safe intensity and duration, allowing for longer imaging distances and preventing accidental exposure to high-intensity NIR light, while also detecting potential risks and adjusting illumination accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high-intensity NIR light is used for illumination, then imaging distance and signal quality are improved, but eye safety is compromised due to retinal damage risk
Solution Approach 1:
The system dynamically adjusts NIR illumination intensity based on real-time detection of subject presence, eye orientation, and pupil size. The controller modulates the illumination intensity to provide maximum permissible eye-safe illumination, allowing high intensity when safe and reducing it when risk is detected, thus resolving the contradiction between imaging quality and eye safety
Solution Approach 2:
The system changes the parameter of illumination intensity from fixed high intensity to variable intensity based on safety calculations. By calculating the maximum permissible illumination level using the formula E_max = (E_retinal_max × A_pupil) / (A_retina × M^2), the system optimizes illumination parameters to achieve both effective imaging and eye safety
2Measurement precision
If NIR illumination intensity is increased to improve imaging at longer distances, then signal-to-noise ratio is improved, but the risk of accidental exposure to harmful levels increases
Solution Approach 1:
The system implements continuous feedback by monitoring subject presence, eye orientation, and pupil size through imaging, then using this feedback to adjust illumination intensity in real-time. This closed-loop control ensures the system maintains optimal signal-to-noise ratio while preventing accidental exposure by reducing intensity when safety conditions are not met
Solution Approach 2:
The system performs preliminary detection of subject presence and eye orientation before activating high-intensity NIR illumination. By assessing safety conditions in advance and calculating the maximum permissible illumination level before illumination occurs, the system prevents accidental exposure while maintaining imaging effectiveness
3Object-affected harmful factors
If the system requires direct alignment and close proximity for safe imaging, then eye safety is maintained, but ease of operation and user comfort are reduced
Solution Approach 1:
The system dynamically adapts illumination intensity based on the subject's distance and eye orientation rather than requiring fixed positioning. This allows imaging at longer distances with reduced intensity, improving ease of operation while maintaining eye safety through real-time parameter adjustment
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
This approach reduces noise in captured images, enables imaging at greater distances, ensures eye safety by constraining NIR illumination to safe levels, and prevents accidental exposure to high-intensity light, thereby improving the effectiveness and safety of NIR imaging systems.
Implementation Method 1
imaging human irises for biometric identification purposes usually requires that the subject's iris be illuminated in near-infrared (NIR) wavelengths just beyond those of visible red light
Implementation Method 2
it passes through the cornea and lens of the eye, where it is magnified by a varying amount, dependent primarily on the pupil size, and focused on the retina
Implementation Method 3
Optical gain of a retina with a dilated iris can increase the incident optical power on the central high-acuity cells of a fovea by a factor of 100×
Data Source
AI summary
A method and system for eye-safe near infra-red (NIR) optical imaging illumination. An eye of an intended subject are imaged with visible light or NIR light at an unconditionally eye-safe illumination level and the maximum permissible eye-safe NIR illumination that can be applied to the eye is determined from the captured images. The eye of the intended subject can then be illuminated with at least one substantially maximal NIR light pulse having a pulse intensity and duration selected to provide the substantially maximum permissible eye-safe NIR illumination intensity at the eye. NIR light pulse illumination can be inhibited in response to detection of other subjects either within the vicinity of a volume extending between an NIR illuminator illuminating the eye and the intended subject. The likelihood that an intended subject has been recently illuminated can also be determined and statistical measures can be used to avoid re-illuminating subject unnecessarily.