Diffractive Holographic Eye Tracking for Wide-FOV HMDs
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Solution Overview
Problem
Conventional head-mounted displays are bulky and heavy due to the need for high-intensity light sources to compensate for reduced brightness, and existing eye-tracking systems face challenges with occlusion and variability in eye features, limiting their application in virtual and augmented reality.
Innovation Solution
In-field illumination using a holographic illuminator with a holographic medium positioned near the eye, projecting non-visible light patterns for accurate pupil tracking without occluding the field of view, combined with an IR detector array for precise pupil location determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If images are projected over a large area to provide wide field of view, then field of view is improved, but brightness is reduced
Solution Approach 1:
The patent applies local quality by projecting images selectively only to the pupil region rather than uniformly across the entire eye. The light projection is localized to where it is most needed (the pupil), concentrating optical energy in a specific area to maintain brightness while reducing overall light consumption.
Solution Approach 2:
The patent changes the parameter of light projection from wide-area diffuse illumination to focused pupil-targeted illumination. By adjusting the projection parameters to target specifically the pupil area, the system achieves efficient light utilization, allowing for lower intensity light sources that consume less power and reduce heat generation.
2Illumination intensity
If high intensity light source is used to compensate for reduced brightness, then brightness is improved, but device weight and power consumption increase
Solution Approach 1:
The patent fundamentally changes the illumination parameter from high-intensity wide-area lighting to low-intensity focused pupil lighting. This parameter change allows the use of compact, lightweight light sources with low power consumption, directly resolving the contradiction between brightness and device weight.
3Area of stationary object
If light source is positioned away from field of view to illuminate eye surface, then field of view occlusion is reduced, but eye tracking accuracy is affected by eye feature variability
Solution Approach 1:
The patent applies local quality by positioning the light source and projection system to illuminate only the pupil region rather than the entire eye surface. This localized illumination approach maintains an unobstructed field of view while improving eye tracking accuracy by focusing on the pupil's position and movements, which are less affected by variations in eye features like iris size or eyelid position.
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
Enables compact, lightweight head-mounted displays with efficient power consumption and accurate eye-tracking, allowing for enhanced virtual and augmented reality experiences by projecting images directly to the pupil while maintaining an unobstructed field of view.
Implementation Method 1
a diffractive optical element modulates light from a light source to generate a pattern of light spots
Implementation Method 2
detect reflections of the illuminated patterns off the surface of the eye
Implementation Method 3
an IR detector array for precise pupil location determination
Data Source
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AI summary
A system for making a holographic medium for use in generating light patterns for eye tracking includes a light source configured to provide light and a beam splitter configured to separate the light into a first portion of the light and a second portion of the light that is spatially separated from the first portion of the light. The system also includes a first set of optical elements configured to transmit the first portion of the light for providing a first wide-field beam onto an optically recordable medium and one or more diffractive optical elements configured to receive the second portion of the light and project a plurality of separate light patterns onto the optically recordable medium for forming the holographic medium.