Eye Tracking Illumination Power Reduction via Rolling Shutter Synchronization
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Solution Overview
Problem
Current eye-tracking technologies in mobile devices face significant power consumption issues due to the need for high illumination, especially in outdoor conditions, leading to inefficient battery life and potential device overheating, as traditional LEDs are inefficient and require constant activation to capture images effectively.
Innovation Solution
The method involves dynamically controlling illumination power and beam shape using electronically controllable optical elements, such as MEMS arrays and liquid crystal phase modulators, to minimize power usage by adjusting the duration, intensity, and direction of infrared light based on the estimated distance and location of the eyes, as well as ambient light conditions, thereby optimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If traditional LEDs are used to illuminate the eye for eye tracking, then sufficient illumination is achieved, but power consumption increases significantly and device heating occurs
Solution Approach 1:
The patent implements periodic illumination by activating LEDs only during specific integration periods rather than continuously. The system synchronizes LED activation with the sensor's integration windows, turning LEDs on only when needed for illumination and off during other periods, thereby reducing overall power consumption while maintaining sufficient illumination intensity during active periods.
Solution Approach 2:
The patent dynamically adjusts LED activation based on real-time conditions including integration period timing, ambient light levels, and tracking state. The system transitions between different illumination states (active/inactive) based on operational requirements, optimizing the balance between illumination intensity and power consumption adaptively rather than using a fixed illumination regime.
2Reliability
If LEDs are activated continuously to ensure proper eye tracking, then tracking reliability is maintained, but battery life is reduced and device overheating occurs
Solution Approach 1:
The system employs periodic LED activation synchronized with sensor integration periods, activating illumination only during necessary time windows rather than continuously. This periodic operation maintains tracking reliability during active periods while extending battery life by eliminating unnecessary illumination during inactive periods, directly addressing the contradiction between reliability and duration.
3Measurement precision
If high power illumination is used to combat environmental reflections outdoors, then eye tracking accuracy is improved, but power consumption increases
Solution Approach 1:
The system dynamically adjusts illumination power and activation timing based on ambient light conditions and tracking requirements. During outdoor conditions with strong environmental reflections, the system activates LEDs at higher power during critical integration periods to maintain eye tracking accuracy, while reducing or eliminating illumination during non-critical periods to manage power consumption, achieving a dynamic balance between precision and energy use.
Solution Approach 2:
The system performs preliminary assessment of ambient light conditions and predicts required illumination levels before activation. By pre-evaluating environmental factors and preparing appropriate illumination strategies, the system can activate high-power illumination only when and where needed to combat environmental reflections, rather than continuously, thereby maintaining accuracy while controlling power consumption.
Data Source
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AI summary
A method of reducing the illumination power requirements for an object tracking system, the method including the steps of: (a) determining a current location of the object within a scene; (b) for a future frame: determining a band around the object of interest; determining a start and stop time for when the rolling shutter detector will be sampling the band; and illuminating the object only whilst the rolling shutter detector is sampling the band; (c) for a future frame predicting the location of the object relative to the tracking system; determining the ambient light levels; and illuminating the object with the minimum optical power required for the object to be imaged suitably for tracking.