Strobed Illumination for Eye Imaging Safety
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Solution Overview
Problem
Existing imaging systems face challenges in capturing accurate images of the human eye without causing damage due to excessive illumination, as conventional methods reduce signal-to-noise ratio and exceed safe irradiance limits, especially in biometric applications like iris recognition and pupillometry.
Innovation Solution
A method and apparatus utilizing synchronized strobed illumination sources and cameras to capture images of the eye, optimizing light intensity and duration to maintain signal quality while keeping average irradiance below safety thresholds, allowing for accurate biometric data collection without harming the subject.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the exposure time is reduced using electronic shutter to avoid motion blur, then image sharpness is improved, but signal-to-noise ratio deteriorates
Solution Approach 1:
The illumination source is modulated to provide periodic strobed illumination synchronized with the camera frame rate. This allows the camera to capture images during brief illumination intervals, maintaining short effective exposure times for sharpness while the periodic nature enables signal accumulation across multiple frames to improve signal-to-noise ratio.
Solution Approach 2:
The system changes the temporal parameters of illumination by switching from continuous to pulsed/strobed illumination. By controlling the duty cycle, pulse width, and synchronization with camera exposure, the system optimizes both image sharpness (through short effective exposure) and signal-to-noise ratio (through controlled illumination intensity during exposure windows).
2Loss of information
If scene irradiance is increased to compensate for reduced signal-to-noise ratio, then signal quality is improved, but object damage risk increases
Solution Approach 1:
The illumination is delivered in periodic pulses synchronized with camera exposure rather than continuously. This allows high peak irradiance during brief illumination windows to maintain signal quality, while the low average irradiance between pulses prevents thermal damage to the eye. The duty cycle is controlled to stay below safety thresholds.
Solution Approach 2:
The system maintains continuous camera operation and continuous subject presence in the field of view, with illumination and image capture occurring continuously in synchronized cycles. This ensures that useful imaging action continues without interruption while the periodic illumination pattern maintains safety by allowing thermal dissipation between pulses.
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 enables clear and accurate capture of eye images, reducing motion blur and maintaining signal quality while ensuring safe exposure, thereby facilitating effective iris recognition and pupillometry without risking eye damage.
Implementation Method 1
The object is illuminated at least in part by photons from the strobed illumination source while the camera captures images of the object
Data Source
AI summary
A method and apparatus for strobed image capture includes stroboscopic illumination synchronized with one or more cameras to improve a signal to noise ratio, reduce motion blur and avoid object damage in sensor systems used to analyze illumination sensitive objects.