Light-Guide Optical Element Coupling for Compact Waveguide Filling
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Solution Overview
Problem
Existing optical systems face challenges in efficiently filling near-eye displays, particularly in waveguides, where the incorporation of beam splitters and mixers adds significantly to the dimensions of the waveguides, and the integration of beam splitter requires greater accuracy in production.
Innovation Solution
The optical system employs a light-guide optical element with a coupling-in aperture, comprising a coupling-in reflector, and a coupling-out arrangement for coupling-out the image towards a user, with a coupling-in aperture, and a coupling-out arrangement for coupling-out the image towards an eye of the user, utilizing a beam multiplier and a coupling-in reflector to redirect the collimated image and its conjugate image into the waveguide without extending its dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a beam splitter or mixer is incorporated into the waveguide to generate conjugate images, then the waveguide can be filled more effectively, but the dimensions of the waveguide increase significantly
Solution Approach 1:
The patent extracts the beam splitter functionality from the waveguide structure itself and places it in a separate coupling-in optical element. This allows the waveguide to maintain its compact dimensions while still achieving effective filling through the external beam splitter that directs light into the waveguide at the appropriate angles.
Solution Approach 2:
The patent introduces a coupling-in optical element as an intermediary between the image source and the waveguide. This intermediary contains the beam splitter and performs the function of generating conjugate images before coupling them into the waveguide, thereby avoiding the need to increase waveguide dimensions.
2Reliability
If a beam splitter is integrated into the waveguide with high precision parallelism to major surfaces, then image conjugate generation is improved, but manufacturing complexity and precision requirements increase
Solution Approach 1:
The beam splitter is extracted from the waveguide and placed in a separate coupling-in optical element. This eliminates the need for high-precision parallelism between the beam splitter and waveguide major surfaces, as the beam splitter is now independently positioned and aligned in the coupling element rather than being integrated into the waveguide structure.
Solution Approach 2:
The optical system is segmented into separate functional components: the waveguide for light propagation and the coupling-in optical element for image conjugate generation. This segmentation allows each component to be manufactured and aligned independently, reducing the overall manufacturing precision requirements compared to an integrated approach.
3Ease of operation
If a coupling-in prism is used to direct rays into the waveguide at shallow angles, then image injection is achieved, but the input aperture and projector size must be larger
Solution Approach 1:
The patent uses a beam splitter arranged at a 45-degree angle to the waveguide axis, changing the dimensional approach from shallow-angle injection to perpendicular injection. This allows the input aperture to be smaller because the light enters the waveguide at a more favorable angle, improving the aperture-to-size ratio.
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 optical system achieves efficient and compact image projection, enhancing the waveguide with a coupling-in aperture, utilizing a beam multiplier and a coupling-in reflector to redirect the collimated image and its conjugate image into the waveguide without extending its dimensions.
Implementation Method 1
a light-guide optical element (LOE) formed from transparent material and having first and second mutually-parallel major external surfaces for supporting propagation of an image by internal reflection at the first and second major external surfaces
Implementation Method 2
utilizing a beam multiplier and a coupling-in reflector to redirect the collimated image and its conjugate image into the waveguide
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3
AI summary
An optical system (100) for directing an image towards a user for viewing includes a light-guide optical element (LOE) (10) having parallel major external surfaces (11a, lib) for supporting propagation of an image by internal reflection, a coupling-out arrangement for coupling out the image towards an eye of the user, and a coupling-in aperture. An image projector (114) includes an image generator (32) for generating an image, collimating optics (31) for collimating the image, and an image conjugate generator (20, 33, 34). The image projector is coupled to the coupling-in aperture so as to introduce both the collimated image and its conjugate image into the LOE prior to the images impinging on either of major external surfaces. The image conjugate generator may be a second image generator (33), or may employ one or more reflecting surface (22, 23, 24, 34) non-contiguous with the major external surfaces of the LOE.