Dynamic Polarization Gaze Tracking for Glasses Reflections
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Solution Overview
Problem
Gaze tracking systems face accuracy issues when users wear glasses due to specular reflections from lenses causing glares that occlude corneal reflection glints and pupils, degrading the system's ability to determine gaze direction and location.
Innovation Solution
The system dynamically polarizes light between a random polarization phase and a single polarization phase at a rate of at least 60 Hz, filtering out glares during random phases and capturing pupil and glint images at high rates to accurately determine gaze locations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light is shone to illuminate the eye for gaze tracking, then the system can capture images of the eye and determine gaze direction, but specular reflections from glasses lenses cause glares that occlude corneal reflection glints and pupils, degrading measurement accuracy
Solution Approach 1:
The system dynamically changes the polarization state of light over time, switching between different polarization phases (e.g., horizontal, vertical, circular) at frequencies above the flicker fusion threshold. This dynamic modulation allows the system to differentiate between glares from glasses lenses and corneal reflections by analyzing temporal patterns in the reflected light, thereby maintaining measurement accuracy despite the presence of specular reflections.
Solution Approach 2:
The system modifies the polarization parameter of the illumination light to resolve the contradiction. By varying polarization angles and states, the system can selectively enhance or suppress reflections from different surfaces (glasses lenses vs. cornea), enabling accurate gaze tracking even when the user wears glasses. This parameter modulation allows differentiation between harmful glares and useful corneal reflection signals.
2Reliability
If polarization filtering is applied to remove glares, then glares reflected from glasses are filtered out, but the system must rapidly switch between polarization phases at high rates to maintain both pupil and glint image capture
Solution Approach 1:
The system employs periodic modulation of light polarization at specific frequencies (e.g., 60 Hz or higher), creating distinct temporal patterns for different reflection sources. By analyzing these periodic patterns, the system can reliably distinguish between glares from glasses and corneal reflections, improving detection reliability. The periodic nature of the modulation simplifies the control mechanism compared to aperiodic or random switching approaches.
Solution Approach 2:
The polarization state acts as an intermediary parameter that mediates between the illumination source and the image capture device. By modulating this intermediary parameter, the system can selectively pass or block different reflection components without requiring complex mechanical filters or multiple light sources. The polarization modulation serves as a simple yet effective control mechanism that enhances reliability while minimizing device complexity.
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 effectively filters out glares and allows for accurate detection of gaze locations at high rates, improving the system's accuracy and reliability even when users wear glasses.
Implementation Method 1
the light is dynamically polarized in a polarization pattern that repeatedly switches between a random polarization phase and a single polarization phase
Implementation Method 2
light from the light source may cause specular reflections from a lens of the glasses. Such specular reflections may cause glares that can occlude corneal reflection glints and images of the pupil
Data Source
AI summary
Embodiments that relate to determining gaze locations are disclosed. In one embodiment a method includes shining light along an outbound light path to the eyes of the user wearing glasses. Upon detecting the glasses, the light is dynamically polarized in a polarization pattern that switches between a random polarization phase and a single polarization phase, wherein the random polarization phase includes a first polarization along an outbound light path and a second polarization orthogonal to the first polarization along a reflected light path. The single polarization phase has a single polarization. During the random polarization phases, glares reflected from the glasses are filtered out and pupil images are captured. Glint images are captured during the single polarization phase. Based on pupil characteristics and glint characteristics, gaze locations are repeatedly detected.