3D Pupil Steering via Light Field Directional Backlighting
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Solution Overview
Problem
Conventional pupil steering methods in head-mounted display (HMD) devices are limited by mechanical adjustments, which result in image quality degradation and insufficient light efficiency due to pupil movements.
Innovation Solution
The implementation of a micro lens array (MLA) based light field directional backlighting system, which enables three-dimensional (3D) pupil steering without mechanical adjustments, by digitally modifying the illumination pattern and using a transmissive display element as the main display panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If mechanical pupil steering methods are used, then the eye box can be steered to maintain alignment with a moving eye, but image quality degrades and light efficiency decreases
Solution Approach 1:
The patent replaces mechanical pupil steering mechanisms with a light field directional backlighting system that uses a micro lens array (MLA) and directional backlight units. Instead of physically moving components to track eye movement, the system dynamically adjusts the illumination pattern through the MLA to steer the eye box in 3D space, eliminating mechanical complexity and image quality degradation while maintaining precise pupil alignment
Solution Approach 2:
The patent transitions from traditional 2D pupil position adjustment to 3D pupil steering by incorporating depth information through the light field approach. The directional backlighting system with MLA creates controllable light fields that can be steered along multiple axes (x, y, and z), enabling three-dimensional eye box tracking that maintains image quality while adapting to natural eye movements in 3D space
2Adaptability or versatility
If mechanical pupil steering components are used, then pupil alignment can be maintained, but device complexity and weight increase
Solution Approach 1:
The patent eliminates mechanical pupil steering components by implementing a purely optical solution using light field directional backlighting with a micro lens array. The system uses electronically controlled illumination patterns instead of mechanical moving parts, significantly reducing device complexity while maintaining the ability to steer the eye box and track pupil position dynamically
Solution Approach 2:
The light field directional backlighting system serves multiple functions simultaneously: it provides illumination for the display, enables pupil steering, and allows 3D eye box tracking. This multi-functionality is achieved through the micro lens array that can dynamically shape and direct light fields, replacing what would traditionally require separate mechanical steering mechanisms
3Illumination intensity
If traditional backlighting is used, then the display can be illuminated, but light efficiency and image quality are compromised due to pupil movements
Solution Approach 1:
The patent implements local quality by using a micro lens array to create directional light fields that are precisely targeted to the user's pupil position. Instead of uniform omnidirectional backlighting, the system dynamically adjusts the illumination direction and concentration based on tracked pupil position, ensuring light is delivered exactly where needed and minimizing energy waste from light that would otherwise miss the pupil
Solution Approach 2:
The system employs feedback through eye tracking to continuously monitor pupil position and dynamically adjust the light field direction. The directional backlighting units receive real-time position information and modify their illumination patterns accordingly, ensuring optimal light efficiency by directing light precisely at the moving pupil while maintaining consistent illumination intensity
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
This solution achieves efficient pupil steering along multiple axes, reduces the thickness and weight of the display stack, lowers power consumption, and enhances light efficiency and image quality.
Implementation Method 1
A light field directional backlighting unit may include an array of light sources and an array of modulators. By digitally modifying the illumination pattern on the array of light sources and diffracting light beams by the array of modulators, a light field may be created
Data Source
AI summary
A head-mounted display device employs light field directional backlighting to provide three-dimensional (3D) pupil steering without mechanical adjustment while maintaining a compact form factor and performance. An example light field directional backlighting unit includes two substantially flat components: an array of light sources and an array of modulators (e.g., a micro lens array (MLA), a stack of transmissive display elements, a pinhole array, and similar ones). By digitally modifying the illumination pattern on the array of light source and pairing to the light field directional backlighting unit to an extra transmissive display element as the main display panel and one or more viewing optical elements, a light field created by the light field directional backlighting unit is moved in three-dimensional (3D) space to correspond to pupil shift without interfering with the display content.