Light-Guide Optical Eye Tracking via Unguided Light Deflection
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Solution Overview
Problem
Existing optical systems for near-eye displays and head-up displays face challenges in accurately tracking eye gaze direction due to the proximity of the eye to the optical components, which obstructs natural view and complicates imaging, and existing solutions for eye tracking are either obstructive or difficult to implement.
Innovation Solution
An optical system utilizing a light-guide optical element with a light redirecting arrangement that deflects light from the eye towards an optical sensor without guiding it through the substrate, allowing for unguided light propagation to the sensor for accurate gaze direction tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a camera is deployed directly in front of the eye to enable high-quality eye motion box imaging, then measurement precision is improved, but the camera obstructs the viewer's natural view
Solution Approach 1:
The patent uses the light-guide optical element's internal reflection surfaces as an intermediary to capture eye reflection images. Instead of placing a camera directly in front of the eye, the system utilizes the existing optical paths and reflection surfaces within the light-guide substrate to indirectly image the eye, thereby maintaining viewing quality while enabling accurate eye tracking
Solution Approach 2:
The patent creates optical copies of the eye reflection by utilizing multiple internal reflection paths within the light-guide optical element. The reflection surfaces generate multiple images of the eye at different positions, allowing the system to capture eye gaze information without requiring a direct line-of-sight camera placement that would obstruct the viewer's natural view
2Device complexity
If optical components are placed close to the eye for compact device design, then device complexity is reduced, but imaging the eye becomes difficult due to large keystone angle
Solution Approach 1:
The patent transitions from direct frontal imaging to side-angle imaging by utilizing the lateral reflection surfaces of the light-guide optical element. This dimensional change in the imaging path allows the system to capture eye images from oblique angles through the side surfaces of the substrate, avoiding the keystone distortion that would result from direct frontal imaging in a compact configuration
3Device complexity
If peripheral portions of mechanical body are used for camera deployment, then device compactness is improved, but eye motion box imaging becomes difficult due to large keystone angle
Solution Approach 1:
The patent makes the light-guide optical element multi-functional by using its internal reflection surfaces for both their primary function of guiding display light and as imaging surfaces for eye tracking. This eliminates the need for separate camera deployment on peripheral mechanical portions, achieving both compactness and high-quality eye imaging through the universal use of the light-guide 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 near-eye displays and head-up displays, by using a light redirecting arrangement to deflect light from the eye to an optical sensor for processing.
Implementation Method 1
a light-transmitting substrate having two mutually parallel major external surfaces... configured to guide light by internal reflection between the two major surfaces
Data Source
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.