Low Profile HMD Eye Tracker Using Visor Reflection
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Solution Overview
Problem
Current helmet-mounted displays (HMDs) face challenges in extending their field of view and incorporating eye tracking functionality without obstructing the pilot's vision or adding excessive weight, especially in high-stress aircraft operating environments.
Innovation Solution
A low-profile eye tracking system for off-visor HMDs that uses IR light sources and cameras to track the pilot's eye movement by reflecting light off the visor's interior surface, determining azimuth and elevation without interfering with the HMD optics or field of view, and includes modular components that can be attached or detached as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional eye tracking components are incorporated into HMD, then eye tracking functionality is achieved, but the pilot's field of view is obstructed and optics efficiency is inhibited
Solution Approach 1:
The eye tracking illuminators and camera are nested within the existing HMD optical structure. The illuminators are positioned at the terminal component of the optical chain, and the camera is integrated into the HMD housing, allowing eye tracking functionality to be embedded without adding external components that would block the pilot's field of view.
Solution Approach 2:
The system uses the reflective property of the visor's interior surface to redirect light from the illuminators through a different spatial path. The illuminators emit light that reflects off the visor interior to illuminate the pilot's eye, while the camera captures the reflected eye image through a separate optical path, effectively utilizing the third dimension (reflection angle) to avoid FOV obstruction.
2Adaptability or versatility
If traditional eye tracking components are incorporated into HMD, then eye tracking functionality is achieved, but excessive weight is added to the system
Solution Approach 1:
The HMD's existing optical components serve multiple functions. The visor's interior reflective surface, originally designed for displaying imagery, is also utilized as a mirror to reflect illuminator light onto the pilot's eye and to provide a reflection path for the eye tracking camera. This multi-functionality eliminates the need for separate dedicated eye tracking optical components, thereby reducing weight.
Solution Approach 2:
The system uses the HMD's own visor reflective surface to perform the eye illumination and imaging functions that would otherwise require separate dedicated components. The visor serves its primary display function while simultaneously providing the optical pathway for eye tracking, making the system self-sufficient and avoiding additional weight from redundant components.
3Measurement precision
If head tracking system is used to extend field of view, then tracking capability beyond FOV is improved, but the orientation of pilot's eyes relative to head must be determined with high precision
Solution Approach 1:
The eye tracking system is merged with the existing head tracking system. Both systems share the same camera platform and processing electronics. The camera is positioned to capture images through the HMD optical path, and the same image processing algorithms used for head tracking are extended to extract eye position and orientation data, thereby achieving high-precision tracking without proportionally increasing system complexity.
Solution Approach 2:
The system uses feedback from the captured eye images to continuously refine the determination of eye orientation relative to the head. By analyzing the position of reflective features in the eye (such as the corneal reflection), the system provides real-time feedback to adjust the tracking calculations, enabling high-precision measurement of eye orientation that complements the head tracking data.
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 tracking functionality for health monitoring and expanded field of view without obstructing the pilot's vision or adding significant weight, providing precise tracking of eye movement relative to the HMD optics.
Implementation Method 1
the IR light sources bounce IR light off the reflective inner surface of the HMD visor and into the pilot's eye
Implementation Method 2
capturing images of the illuminated eye reflected in the HMD visor
Data Source
AI summary
A low-profile eye-tracking system for an off-visor helmet-mounted display (HMD) includes annular illuminators clipped to, and aligned with, the terminal component (e.g., the emitter or combiner) of the HMD optical chain. The illuminators include visible-light or IR light sources mounted around the circumference of the illuminator for bouncing light off the visor's inner surface and into the pilot's left or right eye (the HMD may include separate eye-tracking systems for each eye). Image sensors are positioned to sequentially capture images of the illuminated eyes reflected off the visor surface. HMD onboard electronics analyze the captured image sequence to determine the azimuth and elevation of the pilot's eye relative to the centerline of the HMD optics.