Crossed In-Coupling Optics for Wide FOV Waveguides
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Solution Overview
Problem
Head-Mounted Displays (HMDs) face challenges in achieving a wide field of view (FOV) and sufficient brightness while maintaining a small form factor, which is essential for viewer comfort and practicality.
Innovation Solution
The implementation of an image light guide system with in-coupling and out-coupling diffractive optics, featuring zones with specific diffractive features, allows for the propagation and expansion of image-bearing light, thereby increasing the FOV and brightness while maintaining a compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional single-zone in-coupling diffractive optic is used, then the device complexity is low, but the field of view and brightness are insufficient
Solution Approach 1:
The in-coupling diffractive optic is divided into multiple zones (first zone and second zone), each with different diffractive features optimized for specific angular bands. This segmentation allows each zone to handle a portion of the field of view, collectively achieving a wider FOV and improved brightness without requiring a single overly complex optic
Solution Approach 2:
Different zones of the in-coupling diffractive optic are assigned different local properties (diffractive features) tailored to their specific functional requirements. The first zone has features optimized for its angular band while the second zone has features optimized for its angular band, allowing each region to perform at its optimal capability
2Illumination intensity
If the waveguide size is increased to achieve wider FOV and better brightness, then the optical performance improves, but the form factor increases reducing wearing comfort
Solution Approach 1:
The patent utilizes the angular dimension by dividing the field of view into different angular bands handled by different zones. This allows the system to achieve a wide FOV through angular multiplexing rather than requiring a physically larger waveguide, maintaining a compact form factor while improving optical performance
3Ease of manufacture
If a single-zone in-coupling optic is used, then the manufacturing is simpler, but the angular bandwidth is limited
Solution Approach 1:
The in-coupling diffractive optic is segmented into multiple zones, each handling a specific angular band. This segmentation approach maintains manufacturing feasibility by using standard diffractive fabrication techniques on each zone while collectively achieving a broader angular bandwidth than a single-zone design could provide
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 effectively doubles the effective angular bandwidth of the diffractive optics, resulting in a significantly wider FOV and improved brightness, while keeping the waveguide's footprint small, thus enhancing viewer comfort and practicality.
Implementation Method 1
an in-coupling diffractive optic arranged along the first surface and/or the second surface, wherein the in-coupling diffractive comprises a first zone having a first set of diffractive features and a second zone having a second of diffractive features
Implementation Method 2
an image light guide for conveying a virtual image including a first surface and a parallel second surface
Implementation Method 3
an out-coupling diffractive optic arranged along the first surface and/or the second surface, wherein the out-coupling diffractive optic comprises a first area having two or more zones and a second area having two or more zones
Data Source
AI summary
An image light guide for conveying a virtual image including a first surface and a parallel second surface, an in-coupling diffractive optic arranged along the first surface and/or the second surface, wherein the in-coupling diffractive comprises a first zone having a first set of diffractive features and a second zone having a second of diffractive features, and an out-coupling diffractive optic arranged along the first surface and/or the second surface, wherein the out-coupling diffractive optic comprises a first area having two or more zones and a second area having two or more zones. Wherein an imaginary axis is oriented along a centerline of the out-coupling diffractive optic, image-bearing light in-coupled into the waveguide by the first zone of the in-coupling diffractive optic is operable to propagate across the imaginary axis to the first area of the out-coupling diffractive optic, and image-bearing light in-coupled into the waveguide by the second zone of the in-coupling diffractive optic is operable to propagate across the imaginary axis to the second area of the out-coupling diffractive optic.