AR Optical Element With Support Substrate for Wider FOV
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Solution Overview
Problem
Augmented reality devices suffer from decreased light transmittance due to absorption by the lightguide, leading to reduced image quality and field of view.
Innovation Solution
Optical elements comprising a lightguide and a support substrate with optimized refractive indices, where the relationship nS≥2·nL·a-b1+b+1 is satisfied, ensuring light propagation in both components under total internal reflection (TIR) to enhance transmittance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If light propagates through the lightguide via total internal reflection, then light guidance is achieved, but light absorption by the lightguide material decreases transmittance
Solution Approach 1:
The patent introduces an exit light-coupling element as an intermediary component between the lightguide and the observer's eye. This diffraction grating couples light out of the lightguide with enhanced efficiency, compensating for the absorption losses that occur during propagation through the lightguide, thereby maintaining both energy efficiency and image quality
Solution Approach 2:
The patent optimizes the refractive index of the lightguide material and adjusts the thickness of the lightguide to minimize absorption losses. By carefully selecting materials with appropriate optical parameters and controlling the geometric parameters, the patent reduces the impact of material absorption on overall transmittance while maintaining effective light guidance
2Strength
If the lightguide thickness is increased to improve structural stability, then mechanical strength is enhanced, but light absorption increases and transmittance decreases
Solution Approach 1:
The patent identifies and optimizes the thickness parameter of the lightguide to achieve the minimum required structural stability while minimizing light absorption. By precisely controlling the thickness within an optimized range, the patent balances mechanical strength requirements with optical performance, ensuring sufficient transmittance for high-quality images
3Adaptability or versatility
If the field of view is expanded to provide broader viewing angle, then observer coverage is improved, but optical path length increases leading to greater light absorption
Solution Approach 1:
The exit light-coupling element acts as an intermediary that efficiently couples light out of the lightguide across a broad angular range. This diffraction grating is designed to extract light for wide viewing angles while compensating for the increased absorption that occurs in longer optical paths, thereby maintaining both expanded field of view and adequate transmittance
Solution Approach 2:
The patent designs the optical system to dynamically adapt to different viewing angles through the use of diffraction-based coupling elements. The exit light-coupling element is configured to efficiently direct light across a range of angles, allowing the system to maintain high transmittance performance across the entire field of view rather than being optimized for a single angle
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
Increased light transmittance and improved image quality by minimizing absorption within the lightguide and support substrate, particularly for blue wavelength light, resulting in a broader field of view.
Implementation Method 1
The entrance light-coupling element couples the imaging light into the lightguide whereupon it is transmitted within the lightguide
Implementation Method 2
The mechanism of propagation within the lightguide is typically via total internal reflection (TIR), wherein the light is continuously reflected within the lightguide
Implementation Method 3
an optical element that comprises an incoupling grating coupled to a lightguide and a support substrate, the incoupling grating being configured to guide light into the lightguide and the support substrate
Data Source
AI summary
An optical element that includes an incoupling grating coupled to a lightguide and a support substrate, the incoupling grating being configured to guide light into the lightguide and the support substrate, and the following relationship being satisfied:nS≥2·sin(FOV2)+1,wherein nS is the refractive index of the support substrate and POV is the field of view (degrees) of the optical element.