Curved Diffractive Optical Combiner for Head-Mounted Displays
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Solution Overview
Problem
Conventional optical combiners for head-worn displays are expensive, difficult to mass produce, and have limited lifespan due to environmental factors, and existing solutions are bulky and not suitable for compact designs, limiting their adoption outside niche markets.
Innovation Solution
A curved diffractive optical combiner that uses a partially reflective diffractive optical element with a curvature to direct image light into an eyebox area, correcting for astigmatism and providing a compact, lightweight, and durable solution for head-worn displays, utilizing a partially reflective diffraction grating that operates in both reflection and transmission modes to overlay images on the external scene without optical distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If holographic combiners are used to provide high quality HUD, then image quality is improved, but manufacturing cost increases and mass production becomes difficult
Solution Approach 1:
The patent uses a diffractive optical element that acts as a simplified copy or alternative to the complex holographic structure. Instead of using expensive holographic media that requires precise laser interference patterns, the invention employs a diffractive element with microstructures that can be manufactured using standard semiconductor fabrication techniques, achieving similar optical combining functionality at lower cost and with better scalability for mass production
Solution Approach 2:
The diffractive optical element can be manufactured using cost-effective processes such as photolithography and etching on glass or plastic substrates. These elements can be produced as disposable or replaceable components, eliminating the need for expensive, delicate holographic media that degrades over time due to environmental factors
2Illumination intensity
If angled transparent substrate combiners are used to present HUD information, then visibility is improved, but device size increases due to bulky external lenses
Solution Approach 1:
The patent combines the functions of the transparent substrate, diffractive optical element, and magnification into a single integrated combiner component. The diffractive optical element is applied directly to the transparent substrate, eliminating the need for separate bulky external lenses and reducing the overall device volume while maintaining the required magnification and visibility functions
Solution Approach 2:
The diffractive optical element introduces optical power through its microstructure design, allowing the combiner to have curvature or optical focusing capability without requiring large external lenses. This enables compact arrangements suitable for head-mounted displays while maintaining proper image magnification and focus
3Measurement precision
If flat substrates are used for combiners to avoid distortion, then image distortion is reduced, but field of view becomes limited and device becomes bulky
Solution Approach 1:
The diffractive optical element provides the necessary optical power and focusing capability, allowing the use of curved or angled substrates without introducing excessive distortion. The diffractive microstructures compensate for the distortion that would normally result from curvature, enabling a wider field of view in a compact configuration
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 curved diffractive optical combiner provides a high-quality, compact, and durable solution for head-worn displays, correcting astigmatism and allowing for a wider adoption of head-mounted displays by being cost-effective and environmentally resilient.
Implementation Method 1
A curved diffractive optical combiner that uses a partially reflective diffractive optical element with a curvature to direct image light into an eyebox area
Implementation Method 2
utilizing a partially reflective diffraction grating that operates in both reflection and transmission modes to overlay images on the external scene
Data Source
AI summary
An optical apparatus includes a first optical element having an eye-ward facing surface and an external world facing surface substantially opposite of the eye-ward facing surface. The optical apparatus also includes a diffractive optical element (“DOE”) disposed to substantially follow a curvature of the eye-ward facing surface of the first optical element. The DOE includes a partially reflective diffraction grating configured to direct a portion of image light in an eye-ward direction where the image light is incident through an eye facing side of the DOE. The curvature of the eye-ward facing surface of the first optical element has an optical power configured to collimate the image light within an eyebox sized area.