Eye Tracker Sequential Illumination for Pupil Contrast
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Solution Overview
Problem
Existing eye tracking systems face challenges in capturing both bright pupil (BP) and dark pupil (DP) images simultaneously, leading to poor contrast and motion-related errors, and simultaneous illumination from multiple light sources can result in hybrid effects that obscure the pupil edge, affecting the accuracy of eye tracking algorithms.
Innovation Solution
An eye/gaze tracker with an image sensor using multiple photodiodes and charge storages, controlled by a unit that selectively illuminates the eye with different light sources during distinct intervals, allowing for simultaneous image capture without interference, and a data processor that generates output signals based on high-quality image data exceeding predetermined quality thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If simultaneous illumination from two or more light sources is used to obtain multiple glint signals, then the ability to calculate cornea radius and distance is improved, but hybrid DP/BP effect occurs causing poor pupil/iris contrast
Solution Approach 1:
The patent implements time-sequential illumination where the first light source illuminates during a first time interval and the second light source illuminates during a second time interval, rather than simultaneous illumination. This periodic activation pattern prevents hybrid DP/BP effects while still enabling multiple glint signal acquisition for accurate cornea radius and distance calculation.
Solution Approach 2:
The illumination process is segmented into distinct time intervals with the first light source operating during the first interval and the second light source operating during the second interval. This temporal segmentation prevents overlapping light effects that would create hybrid DP/BP patterns, maintaining clear pupil/iris contrast in each captured image.
2Adaptability or versatility
If two cameras are used to capture both BP and DP images, then the ability to handle different subject types is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes a single camera system universal by enabling it to capture both BP and DP images through sequential illumination with different light sources. The image registering means alternates between capturing BP images (when first light source is active) and DP images (when second light source is active), eliminating the need for separate dedicated cameras for each imaging mode.
Solution Approach 2:
The system dynamically switches between BP and DP imaging modes by controlling which light source is active during each time interval. This dynamic reconfiguration of the illumination system allows a single static camera to perform multiple imaging functions that would otherwise require separate camera systems.
3Adaptability or versatility
If two images separated in time are captured to obtain both BP and DP modes, then the ability to handle different subject types is improved, but motion-related errors increase
Solution Approach 1:
The patent uses rapid periodic illumination switching between the first and second light sources, capturing BP and DP images in quick succession. This fast temporal cycling minimizes the time window for subject motion to occur between captures, reducing motion-related errors while still enabling both imaging modes to be obtained.
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 high-quality, robust eye/gaze tracking by avoiding hybrid effects and ensuring accurate pupil edge detection, improving tracking robustness across various subjects and environments.
Implementation Method 1
an image sensor with a plurality of photodiodes. Each photodiode is here associated with first and second charge storages configured to store electric charges based on an amount of light reaching the photodiode
Data Source
AI summary
An eye/gaze tracker with first and second light sources each configured to illuminate an eye of a subject and controlled to selectively emit light towards the eye in such a manner that within an operation sequence the eye is illuminated by the first light source during at least one first interval and by the second light source during at least one second interval. An image sensor has a plurality of photodiodes each of which is associated with first and second charge storages configured to store electric charges based on an amount of light reaching the photodiode. At least one switch of the image sensor is controlled such that the electric charges are stored in the first charge storage as a result of the illumination during the at least one first interval and in the second charge storage as a result of the illumination during the at least one second interval.