Light Guide Diffraction Angles for Efficient Image Ray Extraction
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Solution Overview
Problem
Existing display systems, such as those described in patent literature 1, face inefficiencies in utilizing image light rays from display elements, particularly in terms of diffraction efficiency and light usage within the optical system.
Innovation Solution
The proposed optical system includes a light guide with a body, an incident region, an auxiliary extension region, and an exit extension region. The exit extension region features a diffraction structure that divides image light rays into multiple rays, with specific conditions on refractive indices and angles to optimize diffraction efficiency and reduce unnecessary light production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a diffraction structure is used to change the traveling direction of light in the light guide, then the light can be directed to the field of view region, but the usage efficiency of image light rays from the display element deteriorates due to insufficient diffraction efficiency and production of unnecessary light
Solution Approach 1:
The patent optimizes the diffraction structure by carefully controlling the incident angle range (θ_in) and exit angle (θ_out) parameters. Specifically, it sets θ_in to be greater than θ_out by 14° or more, with θ_out between 15°-45°, to maximize diffraction efficiency and minimize unnecessary light production, thereby resolving the contradiction between light direction control and light usage efficiency
Solution Approach 2:
The patent introduces an auxiliary extension region with a diffraction structure that dynamically adjusts the light path by dividing image light rays into multiple rays with different propagation directions. This dynamic light manipulation enables flexible direction control while maintaining high usage efficiency through optimized diffraction parameters
2Ease of manufacture
If the incident angle and exit angle are not optimized, then the diffraction structure is simpler to design, but unnecessary light is produced and diffraction efficiency decreases
Solution Approach 1:
The patent establishes specific parameter ranges for incident angle (θ_in) and exit angle (θ_out) to optimize diffraction performance. By setting θ_in > θ_out + 14° and θ_out = 15°-45°, the design achieves high diffraction efficiency while minimizing unnecessary light, balancing manufacturing simplicity with optical performance
Solution Approach 2:
The auxiliary extension region acts as an intermediary component between the light guide body and the field of view region. It mediates the light path by introducing controlled diffraction with optimized angle parameters, thereby reducing unnecessary light production while maintaining design feasibility
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 configuration enhances the usage efficiency of image light rays by optimizing diffraction efficiency and minimizing unnecessary light production, thereby improving the overall performance of the image display device.
Implementation Method 1
an exit extension region formed at the body and including a diffraction structure dividing an image light ray propagating in a first propagation direction intersecting a thickness direction of the body, into a plurality of image light rays propagating in a second propagation direction intersecting the first propagation direction
Data Source
AI summary
A light guide includes an exit extension region including a diffraction structure dividing an image light ray propagating in a first direction intersecting a thickness direction of a body, into image light rays propagating in a second direction intersecting the first direction, in the first direction, and allowing them to emerge therefrom. At least one part of the region satisfies that when refractive indices of media on individual incident and exit sides of a ray relative to the region are assumed to be equal to each other, an exit angle θ_out of a ray emerging from the region at the highest diffraction efficiency in a plane including a normal line of the region is not smaller than 15° and is not greater than 45°, and an incident angle θ_in of a ray incident on the region in the plane is greater than θ_out by 14° or more.