Bright Pupil Eye-Tracking Using Infrared Light Source Array
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Solution Overview
Problem
Existing eye-tracking systems face challenges in accurately determining the gaze direction and position of the eye, especially in near-eye applications such as head-mounted displays, due to limitations in pupil illumination and image processing.
Innovation Solution
The proposed eye-tracking system employs an array of light sources emitting non-visible light, such as infrared, which are individually enabled to illuminate the eye. The system uses beam shaping optics and an optical combiner to direct the light to the pupil and capture reflected light with a camera, analyzing images to detect a bright pupil condition and determine eye position and gaze angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If infrared illuminators are positioned above or behind a combiner to illuminate the eye, then the illumination area is increased, but the alignment precision with the pupil decreases
Solution Approach 1:
The system segments the illumination function by using multiple individual light sources arranged in an array rather than a single illuminator. Each light source can be independently controlled and targeted at the pupil, allowing the system to maintain precise alignment while collectively covering a broader illumination area through coordinated activation of multiple sources.
Solution Approach 2:
The system introduces a camera as an intermediary device to detect the pupil position and provide feedback for adjusting the light source activation pattern. This intermediary enables the system to dynamically determine which light sources should be active based on real-time pupil location, thereby maintaining alignment precision across different eye positions while utilizing multiple light sources for adequate illumination coverage.
2Area of stationary object
If multiple light sources are activated simultaneously, then the illumination coverage is improved, but the difficulty of determining pupil alignment increases
Solution Approach 1:
The system employs periodic or sequential activation of light sources rather than simultaneous continuous activation. By activating light sources in sequences or patterns, the system can illuminate different regions of the eye over time while the camera captures images during each activation phase. This periodic approach maintains comprehensive illumination coverage while simplifying alignment detection by creating distinct temporal patterns that are easier to analyze.
Solution Approach 2:
The system implements feedback through camera-based pupil detection that monitors the eye's response to light source activation. The camera captures images of the pupil under illumination from activated light sources, and the system analyzes these images to determine which light sources are properly aligned with the pupil. This feedback mechanism resolves the ambiguity that would arise from simultaneous multi-source activation by providing real-time information about actual alignment status.
3Measurement precision
If light sources are positioned coaxially with the gaze direction, then the alignment detection accuracy is improved, but the device complexity increases
Solution Approach 1:
The system makes the camera serve multiple functions: it acts as both the gaze direction sensor for determining alignment and the pupil position detector for tracking eye movements. By using a single camera for both purposes rather than requiring separate sensors, the system achieves high alignment detection accuracy through coaxial positioning while avoiding the increased device complexity that would result from adding additional dedicated sensors.
Solution Approach 2:
The system merges the light source array with the camera system by positioning the light sources in close proximity to the camera and coordinating their operation. This merging allows the illumination and detection functions to work together from a common optical axis, achieving coaxial alignment for improved detection accuracy while reducing overall device complexity by integrating rather than separating the illumination and detection subsystems.
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 precise eye-tracking by accurately determining the alignment of the eye with the light sources, allowing for effective adjustment of content presentation in near-eye displays, such as HMDs, to enhance user experience.
Implementation Method 1
an array of light sources are individually enabled to emit non-visible light, such as infrared, to illuminate an eye
Implementation Method 2
capture reflected light with a camera
Implementation Method 3
uses beam shaping optics and an optical combiner to direct the light to the pupil
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
An eye-tracking method includes enabling at least one light source of an array of light sources to emit non-visible light to illuminate an eye. The method also includes obtaining at least one image of the eye while the at least one light source is enabled. A position of the eye may then be determined based on a position of the at least one light source within the array of light sources in response to determining that the at least one image indicates a bright pupil condition when the at least one light source was enabled.