Symmetrical Beam Multiplier for Uniform Waveguide Illumination
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Solution Overview
Problem
Existing optical display systems using light-guide optical elements face challenges in achieving uniform image illumination due to design limitations related to the size of the image projector and optical design, leading to non-uniform light distribution when the image and its conjugate do not fully fill the waveguide.
Innovation Solution
A light-guide optical system with a symmetrical beam multiplier region containing internal planar beam splitters that subdivides the waveguide thickness into equal layers, allowing for the propagation and coupling of image illumination to achieve uniform filling by either filling multiple layers with the image or its conjugate, or both, within the waveguide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the waveguide is designed to be uniformly filled with projected image and its conjugate image, then uniformity of the viewed image is achieved, but design limitations are imposed on the size of the image projector and optical design
Solution Approach 1:
The waveguide thickness is subdivided into multiple layers by beam splitters, creating distinct propagation channels. This segmentation allows the image illumination to be distributed across multiple layers, achieving uniform filling without requiring a larger image projector or complex optical design.
Solution Approach 2:
Beam splitters are introduced as intermediary elements within the waveguide to redirect and distribute image illumination between different layers. These intermediaries enable uniform image distribution while maintaining a compact image projector design, resolving the contradiction between illumination uniformity and device complexity.
2Volume of moving object
If the image projector size is reduced, then device compactness is improved, but uniform filling of the waveguide with image and conjugate image becomes difficult to achieve
Solution Approach 1:
The problem of uniform illumination is solved by transitioning from a two-dimensional filling problem to a three-dimensional solution. Beam splitters create multiple layers within the waveguide thickness, allowing image illumination to be distributed across the z-dimension (thickness direction). This enables a compact image projector to achieve uniform filling by exploiting the third dimension of waveguide thickness.
3Illumination intensity
If multiple beam splitters are used to subdivide waveguide thickness into layers, then uniform distribution of image illumination is achieved, but device complexity increases
Solution Approach 1:
The optical parameters of the beam splitters are optimized to achieve uniform illumination distribution. By carefully selecting the reflectivity and transmissivity parameters of each beam splitter, the system achieves uniform image filling across multiple layers without requiring an excessive number of beam splitters, thus balancing illumination uniformity with device complexity.
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 symmetrical beam multiplier region ensures rapid and uniform distribution of image and conjugate illumination across the waveguide, overcoming non-uniformity issues and enabling compact and efficient optical system design.
Implementation Method 1
a light-guide optical element (LOE) having two planar major external surfaces that are parallel so as to support propagation of image illumination within the LOE by internal reflection at the major external surfaces
Implementation Method 2
the symmetrical beam multiplier region having n internal planar beam splitters, where n is a positive integer, each beam splitter being internal to the LOE and parallel to the major external surfaces
Data Source
AI summary
An optical system for displaying an image includes a waveguide (10) having two major surfaces (12, 14) that support propagation of image illumination by internal reflection. A coupling-out configuration (16, 18) couples out image illumination towards the eye of the user. An image projector (20) is coupled so as to introduce image illumination into the waveguide so as to propagate by internal reflection. The waveguide also contains a symmetrical beam multiplier region, distinct from the coupling-out region, having one or more beam splitters (24) internal to the waveguide and parallel to its major surfaces. The symmetrical beam multiplier may be used to fill in a conjugate image after a compact coupling-in configuration, and/or may be used to fill the waveguide with the image as an intermediate stage (36) between two optical aperture expansion configurations (32, 34).