Diffractive Eye-Imaging Optics for Wide-FOV Gaze Tracking
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Solution Overview
Problem
Challenges exist in imaging the eye for gaze tracking and biometric identification in virtual and augmented reality systems due to the need for a large field of view and high pixel resolution, often obstructing the user's view and causing image distortions.
Innovation Solution
An imaging system using off-axis camera assemblies with coupling optical elements that direct light from the eye into a substrate, allowing for total internal reflection and redirection to a camera assembly without obstructing the user's view, utilizing diffractive optical elements for efficient image capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a direct-view camera assembly is used to capture eye images, then image quality and resolution can be improved, but the camera assembly obstructs the user's view
Solution Approach 1:
The camera assembly is repositioned from a direct-view configuration to an off-axis configuration, utilizing a third dimension (lateral offset) to resolve the contradiction. The optical device redirects light from the eye at an angle to the off-axis camera, allowing the camera to be positioned without obstructing the user's direct view while still capturing high-resolution eye images.
2Measurement precision
If the field of view is increased to improve gaze tracking accuracy, then measurement precision improves, but the device complexity increases
Solution Approach 1:
The optical device performs multiple functions: it redirects light to the off-axis camera for eye imaging, guides display light to the user's eye, and enables a wide field of view for gaze tracking. By integrating these functions into a single optical component, the system achieves high measurement precision without proportionally increasing device complexity.
3Object-affected harmful factors
If coupling optical elements are used to redirect light to an off-axis camera, then view obstruction is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The coupling optical elements are integrated into a single monolithic optical device rather than being separate components. This merging reduces the number of interfaces and alignment points, thereby reducing manufacturing precision requirements while still achieving effective light redirection to the off-axis camera.
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 eye imaging with a larger field of view and higher pixel resolution without obstructing the user's view, facilitating effective gaze tracking and biometric identification.
Implementation Method 1
The first coupling optical element may be configured to deflect light at an angle to totally internally reflect (TIR) the light between the proximal and distal surfaces and toward the second coupling optical element
Implementation Method 2
In some embodiments, at least one of the first and second coupling optical elements include a plurality of diffractive features
Data Source
AI summary
Examples of eye-imaging apparatus using diffractive optical elements are provided. For example, an optical device comprises a substrate having a proximal surface and a distal surface, a first coupling optical element disposed on one of the proximal and distal surfaces of the substrate, and a second coupling optical element disposed on one of the proximal and distal surfaces of the substrate and offset from the first coupling optical element. The first coupling optical element can be configured to deflect light at an angle to totally internally reflect (TIR) the light between the proximal and distal surfaces and toward the second coupling optical element, and the second coupling optical element can be configured to deflect at an angle out of the substrate. The eye-imaging apparatus can be used in a head-mounted display such as an augmented or virtual reality display.