Multi-Wavelength Image Light Guide for Eyebox Expansion
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Solution Overview
Problem
Conventional image light guides in Head-Mounted Displays (HMDs) face challenges such as constrained eyebox size, uneven light distribution leading to hot spots, and increased size and complexity due to beam management functions, which limit movement and device placement.
Innovation Solution
An image light guide with a substrate featuring an in-coupling diffractive optic and an out-coupling diffractive optic, each with specific periodic structures, to angularly encode and decode image-bearing light beams, expanding the eyebox in two dimensions while maintaining image integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If beam management functions including beam expansion and light distribution are added to the waveguide, then light distribution uniformity is improved, but the size and manufacturing complexity of the waveguide increase
Solution Approach 1:
The patent combines multiple beam management functions (beam expansion, light distribution, and hot spot reduction) into a single integrated diffractive optic structure. The diffractive optic incorporates multiple diffractive elements that simultaneously perform these functions, eliminating the need for separate beam management components and reducing overall device complexity while maintaining uniform light distribution.
Solution Approach 2:
The diffractive optic is designed to perform multiple functions simultaneously: it expands the beam, distributes light uniformly across the waveguide, and reduces hot spots through its multi-diffractive element structure. This multi-functional design eliminates the need for separate dedicated components for each function, thereby reducing manufacturing complexity.
2Illumination intensity
If beam management functions are added to the waveguide, then light distribution uniformity is improved, but the overall size of the waveguide increases
Solution Approach 1:
By merging beam expansion, light distribution, and hot spot reduction functions into a single diffractive optic component, the patent eliminates the need for separate beam management components that would increase waveguide volume. The integrated structure achieves uniform light distribution without adding significant size.
3Illumination intensity
If conventional beam management components are used, then light distribution is improved, but manufacturing cost increases
Solution Approach 1:
The patent merges multiple beam management functions into a single diffractive optic that can be manufactured as one integrated component. This reduces the number of separate parts that need to be manufactured, assembled, and aligned, thereby reducing manufacturing cost while achieving improved light distribution.
Solution Approach 2:
The multi-functional diffractive optic performs beam expansion, light distribution, and hot spot reduction simultaneously, eliminating the need for multiple separate components. This reduction in component count directly lowers manufacturing cost while maintaining effective light distribution.
4Volume of moving object
If the eyebox size is constrained, then device compactness is improved, but movement tolerance and viewing comfort are reduced
Solution Approach 1:
The diffractive optic is designed with multiple diffractive elements that create multiple light paths and expand the effective eyebox. This segmentation of the optical function allows the system to maintain compactness while providing a larger effective viewing area and greater movement tolerance through the distributed light paths.
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 solution provides improved diffraction efficiency and uniform light distribution across the output aperture, reducing hot spots and enhancing the eyebox size and flexibility in HMD designs.
Implementation Method 1
An in-coupling diffractive optic is formed along the substrate and is operable to diffract image-bearing light beams from an image source into the substrate in an angularly encoded form
Implementation Method 2
An out-coupling diffractive optic is formed along the substrate, wherein the out-coupling diffractive optic is operable to diffract the image-bearing light beams from the substrate in an angularly decoded form
Data Source
AI summary
An image light guide for conveying a virtual image including a substrate operable to propagate image-bearing light beams along a length thereof. An in-coupling diffractive optic is formed along the substrate and is operable to diffract image-bearing light beams from an image source into the substrate in an angularly encoded form. An out-coupling diffractive optic is formed along the substrate, wherein the out-coupling diffractive optic is operable to diffract the image-bearing light beams from the substrate in an angularly decoded form. The in-coupling diffractive optic has three pluralities of periodic diffractive structures symmetric about three equidistant axes and the out-coupling diffractive optic has two pluralities of periodic diffractive structures having a periodicity equivalent to two of the three pluralities of periodic diffractive structures of the in-coupling diffractive optic. The two pluralities of periodic diffractive structures of the out-coupling diffractive optic are also parallel with two of the three pluralities of periodic diffractive structures of the in-coupling diffractive optic.