Waveguide Eye Tracking with 1D Diffractive IR Emitter Line
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Solution Overview
Problem
Components used in electronic devices for displaying images near the eyes of a user can be bulky and do not exhibit desired levels of optical performance, potentially obstructing the user's view and reducing the effectiveness of optical systems in devices like virtual or augmented reality headsets.
Innovation Solution
An optical system is designed with a waveguide that includes one-dimensional diffractive gratings and optical emitters to emit infrared light at different angles, allowing for accurate gaze tracking and measurement of the eye's horizontal position without obstructing the user's view, using a combination of collimated and divergent light paths to replicate a line of infrared emitters outside the user's field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If traditional display components are used near the user's eyes, then image display function is achieved, but the components become bulky and obstruct the user's view
Solution Approach 1:
The patent transitions from traditional bulky display components to a waveguide-based system that propagates light through a thin planar structure. The waveguide uses total internal reflection to guide image light and infrared light through its thickness, enabling a transition from three-dimensional bulky components to a two-dimensional thin-film architecture that does not obstruct the user's view.
Solution Approach 2:
The patent employs a waveguide as a thin film structure that can be positioned close to the user's eye without causing obstruction. The waveguide's thin-film architecture allows it to maintain mechanical integrity while providing sufficient optical path length for image projection and infrared light guidance, resolving the contradiction between display functionality and view obstruction.
2Measurement precision
If infrared emitters are placed inside the field of view for gaze tracking, then accurate eye tracking is achieved, but the emitters obstruct the user's view
Solution Approach 1:
The patent extracts the infrared emitter from the visible field of view by positioning it outside the user's viewing area. The waveguide then transports infrared light from this external position to the eye box region, allowing gaze tracking to occur without the physical presence of emitters in the user's line of sight, thereby eliminating view obstruction while maintaining tracking accuracy.
Solution Approach 2:
The waveguide acts as an intermediary that transfers infrared light from emitters positioned outside the field of view to the eye box region. This mediator enables the separation of the infrared light source from the viewing area, allowing accurate gaze tracking through the waveguide's light guidance while keeping the emitter itself invisible to the user.
3Measurement precision
If multiple infrared emitters are arranged in a line for comprehensive eye tracking, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent creates a virtual copy of a linear array of infrared emitters by using a single physical emitter combined with a diffractive optical element. The DOE diffracts the infrared light to produce multiple virtual emitter positions that replicate the functionality of a physical linear array, achieving comprehensive eye tracking coverage without the complexity of multiple physical emitters and their associated control systems.
Solution Approach 2:
The patent replaces the mechanical system of multiple physical infrared emitters arranged in a line with an optical system using a diffractive optical element. The DOE uses diffraction to spatially distribute a single emitter's light output to create multiple virtual source positions, substituting mechanical complexity with optical functionality to achieve the same measurement precision with reduced device complexity.
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 solution enables robust and accurate gaze tracking while maintaining a clear field of view, allowing for seamless integration of virtual and real-world content in augmented reality systems.
Implementation Method 1
The waveguide may propagate the infrared light via total internal reflection
Implementation Method 2
The waveguide may include overlapping one-dimensional diffractive gratings having parallel periodic structures
Implementation Method 3
A projector may generate image light. An input coupler may couple the image light into the waveguide
Data Source
AI summary
A display may use a waveguide to provide image light to an eye box. An emitter may emit infrared light collimated at different angles relative to a collimated axis and divergent along an orthogonal axis. The waveguide may propagate the infrared light and may include overlapping one-dimensional diffractive gratings with parallel periodic structures. Each grating may diffract, towards the eye box, a respective portion of the infrared light from a respective incident angle onto a respective output angle relative to the collimated axis. A camera may capture glints of the infrared light as reflected off a user's eye at the eye box for performing gaze tracking. The emitter and the gratings may effectively form a one-dimensional line of infrared emitters overlapping the eye box while allowing the optical emitter to remain invisible to a user.