Light Director Assembly for HMD Eye Box Alignment
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Solution Overview
Problem
Head-mounted displays (HMDs) face inefficiencies in light distribution due to fixed viewing angles, leading to wasted light and brightness degradation, as much of the light emitted by electronic displays falls outside the user's eye box, and high brightness settings can degrade the display over time.
Innovation Solution
A light director assembly is introduced, comprising individual light directors for each subpixel to control and tune the angular distribution and primary emission angle of light, ensuring that light is focused and directed efficiently to the user's eye box, reducing waste and maintaining display quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the electronic display emits light with a wide viewing angle, then the light can reach a broader area, but much of the light falls outside the user's eye box causing brightness loss and wasted light
Solution Approach 1:
The patent divides the display into individual subpixels and places a dedicated light director over each subpixel. This segmentation allows independent control of light direction for each subpixel, enabling precise routing of light from each subpixel directly into the eye box region, thereby reducing light waste while maintaining the ability to serve multiple viewing positions
Solution Approach 2:
The light directors are configured with specific geometric shapes and optical properties tailored to direct light from each subpixel location to the appropriate region of the eye box. Each light director has localized optical characteristics that optimize light direction for its specific position, ensuring that light is efficiently directed where needed rather than uniformly in all directions
2Illumination intensity
If the HMD uses high brightness settings to compensate for light loss, then the perceived brightness improves, but the display degrades over time
Solution Approach 1:
The patent converts what would normally be wasted light (the harmful factor of light falling outside the eye box) into beneficial light by using light directors to redirect it into the eye box. This allows the system to achieve high perceived brightness using the existing light output from the display, eliminating the need to increase display brightness and thereby preventing accelerated display degradation
3Adaptability or versatility
If the user gazes across a scene with fixed display optics, then the field of view expands, but the perceived brightness changes as the eye position changes
Solution Approach 1:
The light directors enable dynamic light direction that adapts to different viewing angles. As the user gazes across the scene and their eye position changes within the eye box, the light directors continue to route light appropriately to maintain consistent brightness perception across the entire field of view, rather than having fixed brightness characteristics
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 light director assembly increases peak intensity by five to ten times, improving brightness and reducing light waste, while maintaining display quality and preventing brightness degradation.
Implementation Method 1
A light director assembly is introduced, comprising individual light directors for each subpixel to control and tune the angular distribution and primary emission angle of light
Data Source
AI summary
A head mounted display (HMD) includes an electronic display and a light director assembly. The electronic display includes a region of subpixels that are configured to emit light. The light director assembly is coupled to receive the light and to direct the light to an optical assembly of the HMD. The light director assembly includes a plurality of light directors configured to reduce an angular distribution of the light emitted from corresponding subpixels included in the region of subpixels.