Varifocal Projection Display for HMDs
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Solution Overview
Problem
Existing head-mounted display (HMD) focusing systems face challenges with power consumption, size, weight, and accuracy due to the need to move large displays or lenses to focus virtual images, which are inefficient and imprecise.
Innovation Solution
A varifocal projection system that adjusts a smaller, lighter lens assembly of a projector based on eye-tracking data from a camera, using a polarized beam splitter and infrared illumination to focus on the user's gaze direction, reducing power consumption and focusing time while improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large displays or lenses are moved to focus virtual images in HMDs, then focusing capability is achieved, but power consumption increases and device weight increases
Solution Approach 1:
The patent implements a dynamic focusing system that adjusts the lens assembly position based on real-time eye-tracking data. The lens assembly is moved only when and where needed to match the user's gaze direction, rather than continuously or over large ranges. This dynamic adjustment reduces power consumption while maintaining focusing capability.
Solution Approach 2:
The patent replaces traditional mechanical display positioning mechanisms with an optical approach using a movable lens assembly. Instead of moving heavy displays mechanically, a lighter lens assembly is positioned using precision actuators guided by eye-tracking data, reducing both power consumption and mechanical complexity.
2Reliability
If large displays or lenses are moved to focus virtual images in HMDs, then focusing capability is achieved, but device weight increases
Solution Approach 1:
The patent extracts the focusing function from the entire display system and isolates it to a specific lens assembly. This allows the focusing mechanism to be implemented with a smaller, lighter optical component rather than moving the entire display assembly, thereby reducing device weight while preserving focusing capability.
Solution Approach 2:
The system uses dynamic eye-tracking to determine when and where focusing adjustment is needed, allowing the lens assembly to be smaller and lighter because it only needs to cover the relevant focal range for the user's current gaze direction, rather than accommodating the full display range.
3Reliability
If large displays or lenses are moved to focus virtual images in HMDs, then focusing capability is achieved, but focusing time increases
Solution Approach 1:
The patent uses eye-tracking to predict where the user is looking and pre-positions the lens assembly accordingly. By anticipating the user's gaze direction and adjusting the focus in advance, the system eliminates delays associated with reactive focusing, thereby reducing focusing time while maintaining accurate focus capability.
Solution Approach 2:
The system implements a feedback loop using eye-tracking data to continuously monitor user gaze direction and dynamically adjust the lens assembly position. This real-time feedback enables rapid focusing adjustments that match the user's visual attention, reducing perceived focusing time and improving responsiveness.
4Reliability
If large displays or lenses are moved to focus virtual images in HMDs, then focusing capability is achieved, but measurement precision of gaze direction decreases
Solution Approach 1:
The patent introduces an intermediary optical system consisting of a beam splitter and camera that enables precise eye-tracking measurement. This intermediary setup allows the system to accurately measure gaze direction by capturing eye position through the optical path, providing high-precision feedback for lens assembly positioning without interfering with the user's view.
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 efficiently and accurately focuses virtual images on the user's gaze direction, reducing power usage and weight, and enhancing focus adjustment speed and precision.
Implementation Method 1
A camera positioned to image an eye of a user of HMD may capture one or more images
Implementation Method 2
using a polarized beam splitter and infrared illumination to focus on the user's gaze direction
Implementation Method 3
A lens assembly of a projector may be adjusted to focus on the viewing portion of the virtual scene that the user is looking at
Data Source
AI summary
A virtual scene may be projected onto a two-dimensional screen of a head mounted display. The two-dimension screen may be substantially perpendicular to a visual axis of a user wearing the head mounted display. A lens assembly of the projector may be adjusted to focus on a viewing portion of the virtual scene on the screen.