See-through HMD optics stray light suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Head-mounted displays (HMDs) with see-through capabilities suffer from stray light issues, which reduce image sharpness and contrast by causing black areas to appear gray, affecting the quality of both the displayed digital content and the environmental view.
Innovation Solution
The implementation of an optical system that includes a DLP-based upper optical module with a polarized light source, reflective polarizer, and a quarter-wave retarder film to manage stray light by directing 'off' pixel reflections away from the optical axis, utilizing a TIR wedge and corrective wedge to trap dark state light, and incorporating a combiner element for clear environmental viewing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a see-through optical system is used in HMDs, then environmental visibility is improved, but stray light increases causing reduced image contrast and sharpness
Solution Approach 1:
The patent extracts and removes stray light from the optical path using dedicated light-trapping structures. Black coatings and light-absorbing materials are applied to internal surfaces to capture and eliminate stray light reflections, separating the harmful stray light from the useful transmitted environmental light and displayed image light.
Solution Approach 2:
The patent converts the harmful stray light into a beneficial effect by using the same optical surfaces to both transmit environmental light and trap stray light. The black coatings and light-trapping structures that eliminate stray light also help define the boundaries of the displayed image, improving contrast while maintaining environmental visibility.
2Loss of information
If black areas are displayed in HMDs, then image contrast is improved, but see-through view quality deteriorates due to gray appearance
Solution Approach 1:
The patent applies different optical properties to different regions of the optical system. Black coatings are selectively applied only to surfaces where stray light trapping is needed, while other surfaces maintain high transmission for environmental visibility. This localized treatment ensures black areas appear truly black in the displayed image without affecting the see-through view quality.
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 enhances image contrast and sharpness by effectively suppressing stray light, allowing for high-brightness, deep blacks, and maintaining a clear see-through view of the environment, improving the overall display quality of HMDs.
Implementation Method 1
a polarized light source, reflective polarizer, and a quarter-wave retarder film to manage stray light
Implementation Method 2
utilizing a TIR wedge and corrective wedge to trap dark state light
Implementation Method 3
incorporating a combiner element for clear environmental viewing
Data Source
AI summary
Aspects of the present invention relate to providing see-through computer display optics.