Retinal Illumination Alignment for Eye Tracking
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Solution Overview
Problem
Existing eye-tracking techniques lack efficiency and accuracy due to misalignment of illumination with the camera's optical axis, especially when pupil openings are small, leading to inadequate retinal imaging and reduced tracking capabilities.
Innovation Solution
The use of diffuse light directed from positions closer to the optical axis than the lens aperture radius, combined with a scattering optic to produce polarized light that minimizes glint reflections, enables better alignment and retinal imaging, even with varying pupil sizes and orientations, using devices with modular camera attachments for efficient eye tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light is directed from positions outside the lens aperture radius (conventional technique), then the device structure is simpler, but the retinal imaging accuracy deteriorates especially when pupil openings are small
Solution Approach 1:
A scattering optic is introduced as an intermediary element between the light source and the retina. This scattering optic diffuses the light and redirects it toward the optical axis, enabling retinal illumination from positions within the lens aperture radius without requiring direct alignment of the light source with the optical axis. The scattering optic acts as a mediator that transforms the light path to achieve both simplicity and accuracy.
2Area of stationary object
If a larger scattering optic is used to produce diffuse light, then the illumination coverage is improved, but the device size increases which is problematic for head-mounted devices
Solution Approach 1:
The position parameter of the scattering optic is optimized to be within the lens aperture radius from the optical axis. By changing the positional parameter and utilizing the optical properties of the lens system, the patent achieves efficient light diffusion and redirection with a compact scattering optic, avoiding the need for larger illumination components while maintaining adequate retinal coverage.
3Measurement precision
If conventional eye-tracking illumination is used, then the device structure is simpler, but the tracking accuracy deteriorates due to misalignment with the camera optical axis
Solution Approach 1:
The illumination system is merged with the camera optical path by positioning the scattering optic within the lens aperture radius. This merging allows the illumination light to be redirected through the same optical path as the camera, ensuring automatic alignment between illumination and capture without requiring separate alignment mechanisms. The illumination and imaging functions are combined in a unified optical pathway.
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
This approach enhances the accuracy and efficiency of eye tracking by improving the alignment of illumination and camera capture, allowing for more precise determination of eye position and orientation across a broader range of pupil sizes and orientations, particularly suitable for mobile and head-mounted devices.
Implementation Method 1
a scattering optic configured to produce diffuse light by scattering the light produced by the light source, where at least some of the diffuse light is directed from a position around the optical axis and closer to it than the aperture radius
Implementation Method 2
a camera having a chamber with an aperture fitted with a lens through which captured light is received to form images that are projected onto a surface for recording
Data Source
AI summary
Various implementations disclosed herein include devices, systems, and methods that capture images of an illuminated retina and perform eye tracking using the images. For example, a newly capture image may be compared with a previously-captured image or model of the retina to determine a three dimensional (3D) position or orientation of the eye, relative to the camera/tracking system. Diffuse light is directed towards the retina to produce reflections that are captured by the camera. The diffuse light is directed from positions that better aligned with the camera than prior retinal-imaging techniques. For example, at least some of the diffuse light may be directed towards the retina from one or more positions that are less than the camera lens' aperture radius distance from the camera lens' optical axis.