Retinal Projection Gaze Tracking for Stable Eye Box Alignment
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Solution Overview
Problem
Retinal projection displays face challenges in maintaining precise alignment between the display and the eye due to changes in gaze direction, necessitating accurate gaze tracking to ensure continuous image projection onto the retina.
Innovation Solution
A retinal projection display system incorporating an infrared light source, scanning mirror, reflective surface, and infrared photodetectors to determine gaze direction, with a hardware computation module that aligns the visible light image projection based on gaze direction and pupillary distance alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the eye box area is kept small for retinal projection, then the system achieves high resolution and direct retinal imaging, but precise alignment between the RPD and the eye becomes difficult to maintain
Solution Approach 1:
The system employs infrared photodetectors to continuously detect the user's gaze direction and provides feedback to the control module, which adjusts the scanning mirror position accordingly. This closed-loop feedback mechanism ensures precise alignment is maintained dynamically as the user moves their eyes, resolving the contradiction between small eye box precision and alignment maintenance ease.
Solution Approach 2:
The system transitions from a static alignment approach to a dynamic one by continuously tracking gaze direction using infrared photodetectors and adjusting the scanning mirror in real-time. This dynamic adaptation allows the system to maintain precise image projection onto the retina even as the user's eye position changes, solving the alignment maintenance problem.
2Adaptability or versatility
If gaze direction changes during usage, then the user experiences natural eye movement, but the eye box location changes requiring continuous realignment
Solution Approach 1:
Infrared photodetectors continuously monitor gaze direction and provide feedback to the control module, which adjusts the scanning mirror to maintain precise eye box alignment. This feedback loop allows the system to adapt to natural gaze changes while preserving manufacturing precision requirements.
Solution Approach 2:
The system performs preliminary calibration by projecting alignment patterns and detecting their reflection from the user's eye to establish the initial gaze direction and eye box position. This preliminary action creates a reference frame that enables subsequent dynamic tracking and alignment maintenance during normal operation.
3Measurement precision
If infrared light is projected over a large field of view, then gaze tracking accuracy is improved, but the amount of infrared light required increases
Solution Approach 1:
The system projects infrared light over the entire field of view of the scanning mirror (excessive action) to ensure complete coverage for accurate gaze tracking, accepting the increased energy consumption as necessary for achieving high measurement precision in the gaze direction.
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
Ensures continuous and jitter-free image projection onto the retina by dynamically adjusting the image position according to gaze direction changes, maintaining alignment despite eye movements.
Implementation Method 1
infrared light from an infrared light source is projected onto the reflective surface using the scanning mirror... reflected infrared light that reflects off of the eye of the user is received at the at least one infrared photodetector
Implementation Method 2
A retinal projection display system incorporating an infrared light source, scanning mirror, reflective surface, and infrared photodetectors to determine gaze direction
Data Source
AI summary
A retinal projection display system includes at least one visible light source for projecting a visible light image, a scanning mirror having a field of view larger than the visible light image, a reflective surface on which the visible light image is projected at least partially towards an eye of a user, wherein the reflective surface is larger than the visible light image, and a hardware computation module comprising a processor and a memory, the hardware computation module configured to determine a gaze direction of the user, the hardware computation module further configured to coordinate operation of scanning mirror and the at least one visible light source for projecting the visible light image onto the reflective surface based on the gaze direction such that the visible light image is projected into a retina of the user.