Illumination Waveguide for Uniform Display Lighting
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Solution Overview
Problem
Current projection image displays, particularly in head-mounted displays (HMDs), face challenges in achieving uniform illumination distribution, which affects the quality of virtual and augmented reality experiences by introducing crosstalk and varying luminance, impacting user situational awareness and image clarity.
Innovation Solution
The implementation of a source illumination distributor with an illumination waveguide that uses a series of partially reflective surfaces, or Optical Folding Elements (OPFEs), to internally direct and deflect light uniformly across the image display device, ensuring consistent illuminance and reducing crosstalk by configuring the optical elements to allow specific polarization components to pass through without additional deflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional illumination methods are used in projection displays, then the system structure is simple, but the illumination distribution is non-uniform causing crosstalk and varying luminance
Solution Approach 1:
An illumination waveguide is introduced as an intermediary component between the light source and the image display device. The waveguide contains a series of partially reflective surfaces that act as intermediate optical elements to redistribute light uniformly across the display device, eliminating the need for complex illumination homogenization systems while achieving uniform illumination.
Solution Approach 2:
The illumination waveguide is segmented into multiple sections, each containing partially reflective surfaces that sequentially redirect portions of the light. This segmentation allows the light to be distributed in controlled increments across different regions of the image display device, achieving uniform illumination through progressive light redistribution.
2Illumination intensity
If uniform illumination is achieved through multiple optical elements, then illumination uniformity improves, but the system size and complexity increase
Solution Approach 1:
The illumination waveguide structure integrates multiple optical functions within a single compact component. The partially reflective surfaces are nested within the waveguide body, allowing the light to undergo multiple redirections and redistributions within a confined volume, achieving uniform illumination without proportionally increasing system size.
Solution Approach 2:
The illumination waveguide utilizes the third dimension (depth/thickness of the waveguide) to achieve light redistribution. By arranging partially reflective surfaces at different positions and orientations within the waveguide volume, the system achieves uniform 2D illumination across the display device while keeping the overall footprint compact.
3Ease of operation
If polarizing beam splitters are used to control light distribution, then illumination control improves, but crosstalk increases due to reverse deflection of image-bearing light
Solution Approach 1:
Different regions of the illumination waveguide have different optical properties. The partially reflective surfaces are strategically positioned and oriented to reflect illumination light toward specific regions of the image display device while being transparent to image-bearing light traveling in the reverse direction. This local differentiation allows precise light distribution control without causing crosstalk.
Solution Approach 2:
The illumination waveguide creates separate optical paths for illumination light and image-bearing light. By using the waveguide structure with controlled partial reflectivity, the system effectively copies the light distribution function of complex polarizing beam splitter systems while avoiding the harmful reverse deflection effect through proper optical path design.
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 uniform illumination distribution across the image display device, reducing crosstalk and enhancing the clarity and consistency of virtual and augmented reality experiences by ensuring that image-bearing light is projected with desired luminance and polarization characteristics.
Implementation Method 1
an illumination waveguide having a front surface and a back surface opposite the front surface and configured to internally direct light along a main direction
Implementation Method 2
the illumination waveguide comprises a plurality of partially reflective surfaces configured to let pass therethrough a portion of waveguide-propagating illumination light along the main direction and further configured to reflect a portion of waveguide-propagating illumination light
Data Source
AI summary
Aspects of embodiments pertain to a display illumination optics for illuminating an image display device of an image generation apparatus, the display illumination optics comprising: a source illumination distributor that includes an illumination waveguide having a front surface and a back surface opposite the front surface and configured to internally direct light along a main direction, wherein the illumination waveguide is configured to distribute the luminance of input illumination light along the main direction of the display illumination optics to obtain, along the main direction, output illumination light of desired luminance.