IR Light Source Switching for Eye Tracking Glint Separation
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Solution Overview
Problem
Ambient light interference complicates eye-tracking in head-mounted displays (HMDs) by creating ambient glints that can be mistaken for controlled glints, leading to inaccurate eye-tracking data.
Innovation Solution
Implementing a system where three or more IR light sources are arranged to reflect light off the eye, with a predetermined pattern of switching them on and off, allowing for the differentiation between controlled and ambient glints by analyzing frame differences in the infrared image data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ambient light is present during eye-tracking, then the imaging device captures both controlled and ambient glints, but the accuracy of eye-tracking deteriorates due to inability to distinguish between controlled and ambient glints
Solution Approach 1:
The patent applies periodic action by switching the IR light sources on and off in a predetermined pattern during image capture. Specifically, multiple IR light sources are alternately activated and deactivated between frames, creating periodic illumination cycles. This allows the system to capture images with controlled glints (when lights are on) and without controlled glints (when lights are off), enabling differentiation from ambient glints through frame subtraction techniques.
Solution Approach 2:
The patent extracts the controlled glint signal from the combined ambient and controlled glint data by using frame subtraction. By capturing a first frame with controlled glints and a second frame without controlled glints (by switching off the IR light sources), the system subtracts the second frame from the first to isolate and remove the ambient glint component, leaving only the controlled glint information for accurate eye-tracking.
2Reliability
If multiple IR light sources are switched on and off according to a predetermined pattern, then controlled glints can be differentiated from ambient glints, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the set of IR light sources into individually controllable units that can be switched on and off independently according to a predetermined pattern. Instead of controlling all light sources simultaneously, the system segments them into groups or individuals that are activated in sequence, allowing systematic capture of controlled glints while managing the complexity through structured control patterns.
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 enhances the accuracy of eye-tracking by effectively distinguishing controlled glints from ambient glints, thereby improving the reliability of eye movement detection in HMDs.
Implementation Method 1
three or more IR light sources are arranged to reflect light off the eye
Data Source
AI summary
Methods and systems are described for determining eye position and/or for determining eye movement based on glints. An exemplary computer-implemented method involves: (a) causing a camera that is attached to a head-mounted display (HMD) to record a video of the eye; (b) while the video of the eye is being recorded, causing a plurality of light sources that are attached to the HMD and generally directed towards the eye to switch on and off according to a predetermined pattern, wherein the predetermined pattern is such that at least two of the light sources are switched on at any given time while the video of the eye is being recorded; (c) analyzing the video of the eye to detect controlled glints that correspond to the plurality of light sources; and (d) determining a measure of eye position based on the controlled glints.