Scanned Beam Eye Tracking with Photodetectors
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Solution Overview
Problem
Existing eye tracking systems for computing devices, particularly in augmented reality display systems, face challenges due to the expense of image sensors and the practicality of camera placement, which can impede mixed-reality displays and increase power consumption.
Innovation Solution
The use of scanned beam imaging with a plurality of photodetectors and a controllable pipeline configuration that differentiates between pupil and glint location processing, allowing for cost-effective detection of eye gaze direction without directly impeding the field of view and optimizing power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If image sensors are used for eye tracking, then measurement precision is improved, but device cost increases
Solution Approach 1:
The patent divides the eye tracking measurement task into two separate detection channels: one for detecting specular reflections (glints) and another for detecting pupil location. Each channel uses simple photodetectors instead of complex image sensors, achieving accurate eye tracking through segmented functional decomposition
Solution Approach 2:
The photodetectors serve multiple functions: they detect both specular reflections from the cornea and light scattered from the pupil through the same optical path. This multi-functionality eliminates the need for separate specialized sensors, reducing cost while maintaining measurement precision
2Measurement precision
If cameras are placed in the field of view for eye tracking, then measurement precision is improved, but the field of view is obstructed
Solution Approach 1:
The patent extracts the eye tracking detection function from the visual field path by using photodetectors positioned to receive light through the near-eye display optics rather than placing cameras in the user's field of view. This separates the measurement function from the display function, eliminating obstruction
Solution Approach 2:
The near-eye display optics serve as an intermediary element that allows photodetectors to detect eye features without being visible to the user. The optics mediate between the eye, the light sources, and the photodetectors, enabling measurement while preserving the clear field of view
3Measurement precision
If continuous eye tracking is performed, then measurement precision is maintained, but power consumption increases
Solution Approach 1:
The patent implements periodic scanning of the eye using the near-eye display optics to modulate light delivery to photodetectors at specific frame rates. This periodic action maintains measurement precision while allowing power consumption to be optimized by activating sensors only when needed rather than continuous operation
Solution Approach 2:
The system dynamically adjusts the operation of photodetectors and processing pipelines based on detected eye motion. When eye movement is detected, tracking updates are performed; when the eye is stationary, updates are reduced or suspended, optimizing power consumption while maintaining precision during active tracking
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 efficient and cost-effective eye tracking in augmented reality systems by using scanned beam imaging with photodetectors to determine pupil and glint locations, reducing power consumption and maintaining high-resolution gaze tracking without obstructing the user's view.
Implementation Method 1
Each photodetector is positioned to detect infrared light reflected from the user's cornea at a corresponding angle
Implementation Method 2
acquisition of pupil images from light that is diffusely scattered by a user's eye
Data Source
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AI summary
Examples are disclosed herein that are related to eye tracking using scanned beam imaging and multiple photodetectors. One example provides an eye tracking system, comprising an infrared light source, scanning optics configured to scan light from the infrared light source across a region comprising a user's cornea, and a plurality of photodetectors, each photodetector being configured to detect infrared light reflected from the user's cornea at a corresponding angle.