Light-Guide Eye Tracking Optics for Unobstructed Gaze Sensing
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Solution Overview
Problem
Existing optical systems for near-eye displays and head-up displays face challenges in accurately tracking the gaze direction of the observer's eye due to the proximity of the eye to the optical components, which obstructs the natural view and complicates imaging, and existing eye-tracking solutions are either inefficient or obstructive.
Innovation Solution
An optical system that utilizes a light-guide optical element with a light redirecting arrangement to image the eye via reflected light, redirecting it towards an optical sensor using unguided light, suitable for near-eye displays, head-mounted displays, and head-up displays, employing illumination sources with non-overlapping wavelength ranges to enhance eye-tracking accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a camera is deployed directly in front of the eye to image the eye within the EMB, then high-quality EMB imaging is enabled, but the viewer's natural view is obscured
Solution Approach 1:
The patent uses the light-guide optical element as an intermediary to capture eye reflections. The LOE is transparent to the viewer's natural view while containing reflective surfaces that redirect eye reflection light to the sensor, enabling eye tracking without obstructing the viewer's field of view
Solution Approach 2:
The patent positions the sensor in a different spatial dimension relative to the eye, using the LOE to redirect light at oblique angles. This allows the sensor to capture eye reflections from a position that does not block the viewer's direct line of sight
2Measurement precision
If the eye is imaged within the EMB via the LOE by coupling reflected light into the LOE, then eye tracking is enabled, but the system complexity increases due to the need for additional optical configurations
Solution Approach 1:
The LOE serves multiple functions: it acts as the display waveguide for projecting images to the viewer, and simultaneously serves as the eye tracking optical element by containing reflective surfaces that capture and redirect eye reflection light to the sensor
Solution Approach 2:
The patent combines the eye tracking optical path with the display optical path by integrating the reflective surfaces within the LOE structure, allowing both functions to share the same optical component rather than requiring separate systems
3Ease of manufacture
If peripheral portions of the mechanical body are used to deploy cameras for EMB imaging, then the device structure is maintained, but imaging difficulty increases due to the relatively large keystone angle
Solution Approach 1:
The LOE acts as an optical intermediary that enables the sensor to capture eye reflections from a position that would otherwise be too far off-axis, effectively reducing the keystone angle issue by providing a controlled optical path through the transparent substrate
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
Enables accurate gaze direction tracking without obstructing the viewer's natural view, suitable for augmented and virtual reality applications, by using a light-guide optical element with a light redirecting arrangement to capture eye reflections effectively.
Implementation Method 1
The coupled-in image propagates along the substrate by repeated internal reflection from the faces
Implementation Method 2
part of the image intensity is reflected so as to be coupled out of the substrate toward the pupil of an eye
Implementation Method 3
redirects light reflected from the eye, in response to illumination of the eye, toward an optical sensor as unguided light
Data Source
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AI summary
A light-transmitting substrate has at least two major surfaces and is deployed with a first of the major surfaces in facing relation to an eye of a viewer. A light redirecting arrangement is associated with the light-transmitting substrate and deflects light from the eye toward an optical sensor that senses light, such that the light deflection occurs at the light-transmitting substrate and the deflected light that reaches the optical sensor is unguided by the light-transmitting substrate. A processor derives current gaze direction of the eye by processing signals from the optical sensor.