Monolithic Eyepiece Diffractive Optical Element Head Mounted Display
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Solution Overview
Problem
Conventional head-mounted display eyepieces face challenges in achieving a large field of view and long eye relief while operating over the full color spectrum, requiring multiple optical elements that increase cost and complexity due to chromatic aberration issues.
Innovation Solution
A monolithic eyepiece design incorporating a diffractive optical element on at least one surface, combined with a reflective folding surface, allows for a single optical substrate material to function over a broad color spectrum with limited distortion, eliminating the need for exterior corrector elements and enabling a 'see-through' optical path without additional optical power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple optical elements are used to correct chromatic aberration, then color correction performance is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines multiple optical elements (refractive lens, reflective surface, and diffractive optical element) into a single monolithic eyepiece structure. This integration maintains the chromatic aberration correction capabilities of multiple elements while eliminating the complexity of assembling and aligning separate components. The diffractive optical element is embedded within the same substrate as the refractive and reflective components, achieving color correction without requiring multiple discrete optical elements.
Solution Approach 2:
The patent employs a composite optical structure that integrates refractive, reflective, and diffractive properties within a single element. The monolithic eyepiece combines materials or structures that exhibit both refractive index variations and diffractive patterns, allowing simultaneous correction of chromatic aberration through multiple optical mechanisms without requiring separate components for each function.
2Manufacturing precision
If a reflective optical design is used to eliminate chromatic aberration, then color correction is improved, but the ability to image a wide field of view deteriorates
Solution Approach 1:
The patent creates a composite optical element that combines reflective and diffractive properties in a single structure. The diffractive optical element works in conjunction with the reflective surface to broaden the field of view while maintaining chromatic aberration correction. The diffractive patterns are designed to compensate for the field-of-view limitations inherent in pure reflective designs, achieving both color correction and wide angular coverage simultaneously.
Solution Approach 2:
The patent applies different optical properties to different regions of the eyepiece element. The diffractive optical element is positioned and designed to specifically address off-axis rays that would otherwise suffer from aberrations, while the central region maintains the reflective optical path for on-axis imaging. This localized optimization allows the system to achieve wide field of view without sacrificing chromatic correction performance.
3Device complexity
If a monolithic single-element design is used, then device complexity and cost are reduced, but the ability to provide both wide field of view and long eye relief deteriorates
Solution Approach 1:
The patent utilizes the third dimension (depth within the monolithic structure) to accommodate multiple optical functions. By embedding the diffractive optical element and reflective surface at different depths and positions within the single eyepiece substrate, the design achieves wide field of view and long eye relief characteristics that would normally require spatially separated components. The dimensional arrangement within the monolithic structure allows light to traverse multiple optical paths without requiring multiple discrete elements.
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 design achieves a wide field of view and long eye relief with minimal distortion, providing excellent optical imaging performance and full color correction in a compact, cost-effective, and manufacturable single-element package.
Implementation Method 1
a diffractive optical element is provided on at least one of the first surface or the second surface
Implementation Method 2
a reflective folding surface is located optically between the first surface and the second surface. The reflective folding surface folds an optical path between the first surface and the second surface
Data Source
AI summary
A monolithic optical element for an eyepiece in a head mounted display system has a body, in which a first surface of the body receives light from a display device, the light passes through a second surface of the body to an eye of a user, and a reflective folding surface is located optically between the first surface and the second surface. The reflective folding surface folds an optical path between the first surface and the second surface. Finally, a diffractive optical element is provided on at least one of the first surface or the second surface. The use of the diffractive optical surface enables the eyepiece element to be constructed of a single optical substrate material, yet function over a broad color spectrum with superior resolution and minimal distortion over a large field of view.