MRI Head-Up Display Eye-Tracker Using Beam Splitter and RF Blocking
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Solution Overview
Problem
Current technologies for displaying visual stimuli and recording eye movements in functional MRI applications are limited by the strong magnetic field and high-energy radio frequency signals, leading to interference and difficulties in maintaining accurate eye tracking due to the need for mesh shielding and complex camera setups.
Innovation Solution
A heads-up display and eye-tracker system that uses relay optics and beam splitters to block RF energy, eliminating the need for mesh shielding and allowing for continuous eye tracking with higher resolution and adjustable field of view, enabling clearer images and more accurate data collection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If mesh shielding is used to block RF emission from the display, then interference to the MRI signal is reduced, but the visual effect of the display is disturbed
Solution Approach 1:
The patent introduces a specialized transparent conducting oxide coating as an intermediary layer between the display and the MRI environment. This coating acts as a selective barrier that blocks RF signals while remaining transparent to visible light, thus protecting the MRI signal without compromising display visibility
Solution Approach 2:
The patent modifies the optical and electromagnetic parameters of the display system by applying transparent conducting oxide coatings with specific electrical conductivity and optical transparency properties. This changes the RF shielding mechanism from using opaque mesh to using a transparent layer that maintains visual quality while providing electromagnetic shielding
2Measurement precision
If a video-based eye tracker with camera outside the bore is used, then eye movement recording is possible, but the setup time becomes very long and calibration is sensitive to head movement
Solution Approach 1:
The patent embeds the eye tracker camera and illumination system within the MRI head coil assembly itself, nesting the eye tracking components inside the existing MRI hardware structure. This eliminates the need for external camera setups and reduces calibration complexity
Solution Approach 2:
The patent integrates multiple functions into the head coil assembly, making it serve both as an MRI radiofrequency coil and as a mounting structure for the eye tracker. This multi-functionality reduces the number of separate components and simplifies the overall setup procedure
3Ease of operation
If the camera is fixed to look at the eye from an angle not perpendicular to the eye, then the eye can be viewed, but the eye tracker loses track as the eye moves away from the center
Solution Approach 1:
The patent makes the eye tracker camera and illumination system adjustable and repositionable relative to the display, allowing dynamic optimization of the viewing angle. This enables the system to maintain perpendicular alignment with the eye across different positions, improving tracking accuracy while keeping setup simple
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 system provides robust eye tracking with reduced setup time, minimizes repeat scans, and delivers clearer images by eliminating mesh interference and allowing for adjustable field of view, enhancing the accuracy and efficiency of fMRI data collection.
Implementation Method 1
A beam splitter assembly in the optical path between the display and the observer's eye reflects visible image light from the display to the observer's eye, and allows energy from the observer's eye to pass through to the camera sensor
Implementation Method 2
relay optics housing for the display used as a waveguide to block the emission of the RF to the outside and cause interference to the MRI signal
Data Source
AI summary
A head-up display and eye-tracker system, suitable for use with a patient in an MRI tube during an MRI procedure. An electronic display assembly includes an outer display tube housing for housing an electronic display device for generating images, the outer tube housing fabricated of an electrically conductive, non-ferrous material. An eye-tracker camera assembly includes an outer camera tube housing for housing an electronic camera sensor, the outer tube camera housing fabricated of an electrically conductive, non-ferrous material. An eyepiece assembly includes an outer housing. A beam splitter assembly includes a beam splitter block having a receptacle holding a beam splitter, the block formed of an electrically conductive, non-ferrous material. The beam splitter reflects light from the display onto the patient's eye, and allows light reflected from the patient's eye to pass to the camera sensor. In another embodiment as a display system, the eye-tracker camera assembly is omitted.