Light-Guide Optical Element Production with Inactive Region Control
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Solution Overview
Problem
Existing methods for producing light-guide optical elements (LOEs) are inefficient in creating optical aperture expansion, particularly for near-eye displays, as they do not effectively manage inactive regions that can cause ghost images and optical aberrations.
Innovation Solution
A method involving bonding parallel-faced plates with reflective coatings, cutting and polishing to form boundary planes, and bonding transparent material to create a precursor structure, followed by slicing to produce LOEs with active and secondary regions, ensuring partial reflection and minimizing inactive areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing methods are used to produce light-guide optical elements, then production can be achieved, but optical aperture expansion is inefficient and ghost images and optical aberrations occur
Solution Approach 1:
The light-guide optical element is divided into distinct active and inactive regions. The inactive regions are intentionally designed to terminate before the edge of the light-guide, creating a clear spatial separation that prevents ghost images and optical aberrations while maintaining production efficiency.
Solution Approach 2:
Different regions of the light-guide optical element are assigned different functional properties. The active region contains the partially reflecting surfaces for optical aperture expansion, while the inactive region is designed without these surfaces to eliminate harmful optical effects. This local differentiation ensures high image quality in the active region while preventing artifacts in the inactive region.
2Ease of manufacture
If inactive regions are not managed properly, then production is simpler, but ghost images and optical aberrations are generated
Solution Approach 1:
The inactive regions are pre-designed and pre-formed during the manufacturing process, with their boundaries clearly defined before the light-guide optical element is completed. This preliminary structuring of inactive regions prevents ghost images from forming, while maintaining a straightforward manufacturing process that does not require complex additional steps.
3Reliability
If the light-guide optical element uses total internal reflection for image propagation, then image guidance is achieved, but inactive regions cause optical aberrations
Solution Approach 1:
The problematic inactive regions are extracted or removed from the optical path by designing them to terminate before the edge of the light-guide. This extraction eliminates the source of optical aberrations while preserving the total internal reflection mechanism in the active region for effective image guidance.
Solution Approach 2:
The light-guide optical element features localized functional zones where the active region maintains total internal reflection for image guidance, while the inactive region is deliberately designed without partially reflecting surfaces to prevent optical aberrations. This local quality differentiation resolves the contradiction between effective image guidance and avoidance of aberrations.
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 method enhances optical aperture expansion by reducing ghost images and optical aberrations, providing efficient production of LOEs suitable for near-eye displays with improved image quality.
Implementation Method 1
a transparent block bounded by two parallel major external surfaces configured to support propagation of light rays therebetween via total internal reflection (TIR)
Implementation Method 2
having a set of mutually-parallel partially-reflecting internal surfaces (or 'facets') located between, and non-parallel to, the major external surfaces
Data Source
Figure 1A~1B
Figure 2A
Figure 2B
AI summary
A method for producing light-guide optical elements (LOEs) (16, 18, 56, 58) each having a set of mutually-parallel partially -reflecting surfaces (17) located between, and oriented non-parallel to, a pair of major external surfaces, and at least one region (30a, 30 b, 30c) without partially-reflecting surfaces. The method includes bonding together parallel-faced plates (4) at interfaces to form a stack (42) of plates with partially- reflecting coatings between them. The stack is cut and polished to form a boundary plane (48, 48a, 48 b) intersecting the interfaces, and a block (50, 50a, 50 b) of transparent material is bonded to the stack. The resulting precursor structure (52, 52') is sliced along parallel planes to form slices, each containing a part of the stack for the active region of the LOE and a part of the block.