Waveguide Imaging System for Eye Tracking and Display Ghost Reduction
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Solution Overview
Problem
Conventional eye tracking systems in artificial reality devices suffer from limited tracking range and accuracy due to out-of-field imaging, which degrades when the eye moves or rotates, and are prone to rainbow effects from real-world light dispersion in waveguide displays.
Innovation Solution
A waveguide-based imaging system that uses infrared light and a waveguide assembly with in-coupling and out-coupling elements to guide light through total internal reflection, providing a virtual direct view of the eye for enhanced tracking and incorporating optical filters to reduce rainbow effects by deflecting real-world light at specific angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional out-of-field imaging is used for eye tracking, then the device structure is simple, but the tracking accuracy and range degrade when the eye moves or rotates
Solution Approach 1:
A waveguide is introduced as an intermediary component between the optical sensor and the eye. The waveguide receives infrared light reflected from the eye through its surface, guides the light internally via total internal reflection, and directs it to the optical sensor. This intermediary structure enables accurate eye tracking regardless of eye position or rotation while maintaining a compact device form factor.
Solution Approach 2:
The waveguide serves multiple functions simultaneously: it acts as a light guide for infrared tracking light, maintains optical path stability, and enables the optical sensor to capture eye images accurately across various eye positions. This multi-functionality resolves the contradiction by providing robust tracking accuracy without proportionally increasing device complexity.
2Area of stationary object
If waveguide display is used to expand effective pupil area, then the field of view and pupil area are improved, but rainbow effects occur due to real-world light dispersion
Solution Approach 1:
Optical filters are applied locally at specific regions of the waveguide where real-world light enters. These filters are positioned to selectively block dispersed wavelengths that cause rainbow effects while allowing the desired infrared tracking light and visible display light to pass through. This localized application resolves the rainbow effect problem without compromising the expanded effective pupil area.
Solution Approach 2:
The waveguide structure that causes light dispersion and rainbow effects is transformed into a beneficial element by strategically placing optical filters. The filters convert the harmful dispersion into a controlled filtering effect, where the waveguide's light-guiding properties are preserved and enhanced while the unwanted rainbow effects are eliminated. The dispersion that would normally be harmful is now managed to improve overall image quality.
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
The system achieves improved eye tracking accuracy and range by maintaining clear imaging of the eye regardless of its position and reduces rainbow effects, enhancing user experience and image quality in augmented and mixed reality applications.
Implementation Method 1
a waveguide configured to guide an image light to propagate inside the waveguide via total internal reflection
Implementation Method 2
The optical filter is configured to deflect a light from a real-world environment incident onto the optical filter at an incidence angle greater than or equal to a predetermined angle back to the real-world environment
Data Source
AI summary
A system is provided. The system includes a light source configured to emit a infrared (“IR”) light for illuminating an object. The system also includes a waveguide imaging assembly including a waveguide, an in-coupling element disposed at a first portion of the waveguide, an out-coupling element disposed at a second portion of the waveguide, and an optical sensor disposed facing the out-coupling element. The in-coupling element is configured to couple the IR light reflected by the object into the waveguide, the waveguide is configured to guide the IR light to propagate toward the out-coupling element through total internal reflection, and the out-coupling element is configured to couple the IR light out of the waveguide toward the optical sensor. The optical sensor is configured to generate a tracking signal of the object based on the IR light output from the waveguide.