Optical Range Finders for Low-Power Gaze Tracking Circuitry
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Solution Overview
Problem
Challenges exist in designing gaze tracking circuitry for head-mounted devices that provide accurate measurements while minimizing power consumption and performance limitations.
Innovation Solution
Incorporating a hybrid gaze tracking system that combines phase-based optical coherence tomography with a camera and light source, using wavelength-tunable lasers to determine eye distance and gaze direction, and employing power-saving strategies based on range finder detections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional gaze tracking circuitry is used, then gaze direction can be tracked, but measurement accuracy is insufficient and power consumption is excessive
Solution Approach 1:
The system implements periodic action by selectively activating the range finder at specific intervals or trigger events rather than continuous operation. The camera and light source operate periodically to capture eye images, while the range finder provides periodic distance measurements. This periodic operation pattern significantly reduces power consumption compared to continuous operation while maintaining adequate gaze tracking accuracy through timely updates.
Solution Approach 2:
The range finder serves a dual purpose: it provides distance information for accurate gaze calculation and simultaneously triggers the camera to capture eye images when eye distance changes are detected. This self-service mechanism allows the system to optimize power usage by having the range finder's distance measurement function automatically initiate the more power-intensive camera operation only when necessary, rather than continuous camera operation.
2Measurement precision
If all gaze tracking components are activated continuously, then accurate gaze measurements can be obtained, but power consumption increases
Solution Approach 1:
The system applies partial action by using the range finder to provide only the necessary distance information required for accurate gaze calculation, rather than using excessive components continuously. The camera captures only the essential eye images needed for gaze determination, and the light source illuminates only when camera capture is required. This partial operation of components maintains measurement accuracy while reducing overall power consumption compared to full continuous operation of all components.
Solution Approach 2:
The camera and light source operate periodically based on trigger events such as detected eye distance changes or at scheduled intervals, rather than continuously. The range finder operates periodically to provide distance updates. This periodic activation pattern ensures that power-intensive components are active only when needed for accurate gaze measurement, significantly reducing average power consumption while maintaining measurement precision through timely data capture.
3Measurement precision
If range finder is used to determine eye distance, then gaze tracking accuracy is improved, but device complexity increases
Solution Approach 1:
The range finder is integrated into the existing gaze tracking system and serves multiple functions: it provides eye distance measurements for accurate gaze calculation, triggers camera capture when distance changes occur, and potentially provides depth information for enhanced eye feature analysis. By making the range finder a multi-functional component that serves both distance measurement and system triggering purposes, the patent reduces the need for separate dedicated components, thereby managing device complexity while improving measurement precision.
Solution Approach 2:
The patent merges the range finder functionality with the camera-based gaze tracking system. The distance information from the range finder is combined with the image data from the camera to calculate accurate gaze direction. This merging of multiple measurement modalities (optical coherence tomography for distance and image analysis for eye position) into a unified gaze tracking system improves precision while avoiding the complexity of completely separate systems operating independently.
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
Enhances gaze tracking accuracy with reduced power consumption by utilizing fewer glints and optimizing power usage through selective activation of components.
Implementation Method 1
The range finder may use phase-based optical coherence tomography to determine eye distance. The signal light specularly reflects off of the eye (creating an eye glint) and the reflected signal light combines with the reference light, creating an interference pattern that can be captured by the image sensor and analyzed to determine glint location, eye distance, eye velocity, and eye acceleration.
Implementation Method 2
The reflected signal light combines with the reference light, creating an interference pattern that can be captured by the image sensor and analyzed to determine glint location, eye distance, eye velocity, and eye acceleration.
Implementation Method 3
The lasers may emit infrared light of known, time-dependent wavelength into a beam splitter that splits the light into signal light that travels a free space path length to the eye and reference light that travels a fixed reference path length towards multiple image sensors.
Data Source
AI summary
Eyewear such as a head-mounted device may include adjustable prescription lenses and/or may include displays. The eyewear may include gaze tracking circuitry that tracks a gaze direction of a user. The gaze tracking circuitry may include a range finder that uses phase-based optical coherence tomography to determine eye distance. The range finder may include one or more emitters such as lasers that emit infrared light into a beam splitter that splits the light into signal light that travels a free space path to the eye and reference light that travels a fixed reference path towards multiple image sensors located around the periphery of the eye. The signal light specularly reflects off of the eye (creating an eye glint) and the reflected signal light combines with the reference light, creating an interference pattern that can be detected by the image sensors and analyzed to determine eye distance.