HMD Eyepiece Diffraction Gratings for Extreme-Angle Eye Tracking
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Solution Overview
Problem
Existing eye tracking systems in virtual and mixed reality headsets suffer from reduced detection accuracy of eye features at extreme gaze angles, distortion in captured images, and require increased spacing between eyepieces and display panels due to the use of hot mirrors or direct viewing through eyepieces.
Innovation Solution
Integrating transmissive or reflective diffraction gratings in the eyepieces of head-mounted displays (HMDs) to redirect infrared light towards eye tracking cameras, allowing for improved viewing angles and reduced spacing, while minimizing distortion and enabling camera placement at the sides of the user's face.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hot mirrors are used to redirect infrared light towards eye tracking cameras, then eye tracking functionality is enabled, but the spacing between eyepieces and display panels must be increased
Solution Approach 1:
The patent extracts the infrared light redirection function from a separate hot mirror component and integrates it directly into the eyepiece structure. This eliminates the need for additional spacing between the eyepiece and display panel, as the infrared redirection capability is built into the eyepiece itself rather than requiring a separate optical path modification.
Solution Approach 2:
The patent combines multiple functions into the eyepiece: visible light transmission for display viewing and infrared light reflection for eye tracking. By merging these functions into a single integrated component, the design eliminates the need for additional spacing that would be required if separate components were used for each function.
2Reliability
If infrared light is reflected directly through eyepieces to eye tracking cameras, then eye tracking is enabled, but distortion occurs in captured images at extreme gaze angles
Solution Approach 1:
The patent applies different optical properties to different regions of the eyepiece. The central region transmits visible light for display viewing, while specific zones within the eyepiece are designed to reflect infrared light at controlled angles. This localized functional differentiation allows the system to maintain image quality across various gaze angles by directing infrared light through optimized paths rather than relying on direct transmission through the entire eyepiece structure.
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
Enhances eye tracking accuracy by reducing distortion and enabling more direct viewing of the user's pupils, even at extreme gaze angles, while minimizing the physical space required between eyepieces and display panels.
Implementation Method 1
transmissive or reflective diffraction gratings integrated in the eyepieces... configured to redirect (transmissive gratings) or reflect (reflective gratings) at least a portion of the IR light received at the eyepieces towards the IR cameras
Implementation Method 2
an illumination source (e.g., an IR light source) that emits light (e.g., IR light) towards the user's eyes
Implementation Method 3
A portion of the IR light is reflected off the user's eyes to the eye-facing surfaces of the eyepieces of the HMD
Data Source
AI summary
An eye tracking system for detecting position and movements of a user's eyes in a head-mounted display (HMD). The eye tracking system includes at least one eye tracking camera, an illumination source that emits infrared light towards the user's eyes, and diffraction gratings located at the eyepieces. The diffraction gratings redirect or reflect at least a portion of infrared light reflected off the user's eyes, while allowing visible light to pass. The cameras capture images of the user's eyes from the infrared light that is redirected or reflected by the diffraction gratings.