Holographic Illuminator for HMD Eye Tracking
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Solution Overview
Problem
Conventional head-mounted display devices are limited by their size and weight, leading to reduced brightness and increased power consumption, and existing eye-tracking systems face challenges with in-field illumination that does not occlude the user's field of view, particularly in accounting for varying eye reliefs, eyelid occlusions, and inter-pupillary distances.
Innovation Solution
An eye-tracking system utilizing a holographic illuminator with a light source and a holographic medium that projects multiple light patterns concurrently onto the eye, allowing for in-field illumination without occluding the field of view, and a detector to determine the pupil's location based on reflected patterns.
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 of projected images deteriorates
Solution Approach 1:
The patent segments the illumination function by using multiple separate light sources positioned at different locations to illuminate different regions of the display device. This allows each light source to concentrate its output on a smaller area, maintaining brightness while collectively covering a wide field of view. The segmentation of illumination sources resolves the contradiction between large projection area and sufficient brightness.
2Illumination intensity
If high intensity light source is used to compensate for reduced brightness, then brightness is improved, but device weight and power consumption deteriorate
Solution Approach 1:
Instead of using a single high-intensity light source that would increase weight and power consumption, the patent segments the illumination into multiple lower-intensity light sources. Each light source can be smaller and more efficient, collectively providing sufficient brightness across the wide field of view without the weight and power penalties of a single high-intensity source.
Solution Approach 2:
The patent combines multiple light sources to achieve the total illumination required for wide field of view. By merging the output of several moderate-intensity sources positioned strategically, the system achieves the necessary overall brightness while keeping individual component sizes and power consumptions manageable, thus reducing total device weight.
3Area of stationary object
If light source is positioned away from field of view to avoid occlusion, then field of view occlusion is reduced, but eye tracking accuracy deteriorates due to varying eye reliefs and eyelid occlusions
Solution Approach 1:
The patent applies local quality by positioning light sources at specific locations that are optimized for their local illumination requirements. Some light sources are positioned to illuminate specific regions of the display device corresponding to different gaze directions, accounting for varying eye reliefs and reducing eyelid occlusions locally. This localized optimization maintains pupil position accuracy while preserving wide field of view.
Solution Approach 2:
The system dynamically adjusts illumination based on detected pupil position and gaze direction. By using multiple light sources that can be selectively activated or adjusted in intensity based on real-time eye tracking data, the system adapts to varying eye reliefs and eyelid positions, maintaining measurement precision across different user anatomies while avoiding field of view occlusion.
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 accurate and reliable pupil position determination with reduced occlusion and power consumption, enhancing the compactness and efficiency of head-mounted displays for virtual and augmented reality applications.
Implementation Method 1
a holographic medium optically coupled with the light source. The holographic medium is configured to receive the light provided from the light source and project a plurality of separate light patterns concurrently toward an eye
Implementation Method 2
a detector configured to detect a reflection of at least a subset of the plurality of separate light patterns, reflected off the eye, for determining a location of a pupil of the eye
Data Source
AI summary
A method includes providing light from a light source and separating 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 method also includes transmitting the first portion of the light through a first set of optical elements to provide a first wide-field beam, transmitting the second portion of the light through a second set of optical elements to provide a second wide-field beam that is spatially separated from the first wide-field beam, and transmitting the second wide-field beam through a third set of optical elements to provide a plurality of separate light patterns. The method further includes concurrently projecting the first wide-field beam and the plurality of separate light patterns onto an optically recordable medium to form a holographic medium.