Head-Worn Eye Tracking Optics Without Fixation Points
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Solution Overview
Problem
Existing eye movement recording devices suffer from light leakage and reflection issues, leading to inaccurate pupil tracking and reduced image information, especially when detecting torsional eye movements, due to variations in facial shapes and the need for infrared illumination.
Innovation Solution
A head-mounted device with a chamber made of cloudy and translucent material, featuring an edgeless inner surface and infrared mirrors, allows daylight and infrared light to enter, eliminating fixation points and enabling accurate eye movement detection using visible light and improved image processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a complete light seal is provided by diving goggles to prevent light leakage, then light blockage is improved, but lens fogging occurs rapidly
Solution Approach 1:
The patent applies local quality by making only the peripheral sealing areas opaque while keeping the central viewing areas transparent. This allows light blockage at the edges to prevent fixation points while maintaining central visibility for the subject, avoiding complete fogging of the lenses.
Solution Approach 2:
The cover is segmented into opaque peripheral sealing portions and transparent central viewing portions. This segmentation allows different regions to serve different functions: the opaque edges block light to prevent fixation, while the transparent centers allow vision and prevent fogging.
2Measurement precision
If infrared illumination is used to illuminate the eyes, then eye tracking is enabled, but reflection in the pupil obscures the pupil edge and impairs tracking accuracy
Solution Approach 1:
The patent extracts and removes the infrared illumination source from the system. Instead of using active infrared LEDs that cause reflections, the invention relies on passive ambient infrared radiation from the environment, eliminating the harmful reflection problem while still enabling infrared eye tracking.
Solution Approach 2:
The patent introduces an intermediary approach by using ambient infrared radiation from the environment as a mediator between the eye and the infrared camera. This indirect illumination source avoids the direct reflection issue that occurs with active infrared LEDs positioned near the eye.
3Object-affected harmful factors
If the chamber is completely enclosed to block light, then fixation suppression is improved, but ventilation is reduced leading to fogging
Solution Approach 1:
The patent applies local quality by making the peripheral sealing areas opaque to block light and prevent fixation, while incorporating transparent or vented regions that allow air circulation. This localized differentiation resolves the contradiction between light blockage and ventilation.
Solution Approach 2:
The patent uses flexible transparent sealing films or membranes that can provide light blockage while allowing vapor transmission and air circulation. These flexible films prevent fixation points while maintaining ventilation to avoid fogging.
4Measurement precision
If grayscale image recording is used for infrared illumination, then infrared eye tracking is enabled, but image information is reduced compared to color representation
Solution Approach 1:
The patent substitutes the mechanical/optical system of active infrared illumination with a passive optical system that captures ambient infrared radiation. This substitution enables the use of color cameras to record both visible and infrared information simultaneously, preserving full color image information while still enabling eye tracking.
Solution Approach 2:
The patent makes the imaging system universal by using a color camera that can capture both visible light and infrared radiation simultaneously. This multi-functional approach allows the same device to perform both color imaging and infrared eye tracking, eliminating the need for separate grayscale infrared recording.
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 device provides enhanced detection of torsional eye movements with increased image detail and reduced risk of retinal damage by eliminating the need for infrared illumination, ensuring accurate and comfortable eye tracking.
Implementation Method 1
at least one infrared mirror transparent in the visible spectrum for reflecting infrared light onto at least one infrared camera
Implementation Method 2
the spectacle body and the cover are made of a cloudy and translucent material... so that while light enters the interior of the device, the subject cannot find any fixation points inside
Data Source
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AI summary
Head-mounted devices for recording eye movements during video oculography are already known in the art. In these known methods, an infrared image is captured in a darkened chamber formed by a spectacle-like body of the device. The darkening is intended to prevent the subject's eye from fixating, but this is unsatisfactory because the required seal between the contact edges and the subject's face is rarely achieved, and light entering through remaining openings promotes fixation. The invention provides for allowing ambient light to enter through a opaque, translucent material, but rounding the edges and corners on one viewing side to such an extent that fixation is prevented despite the incoming light.This also makes it possible to carry out further, more light-intensive measurements and evaluations, which were not feasible in the darkness of known chambers.