Optical System Light Guide Dividing Diffraction Structure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical systems for head-mounted displays face challenges in reducing the area of the field of view where no pupil of an image light ray is located and improving the usage efficiency of image light rays, while also aiming to lower manufacturing costs.
Innovation Solution
An optical system comprising a light guide with a plate-shaped body, an in-coupling region, and a reproduction region that includes a dividing diffraction structure with first and second diffraction structure regions on opposing surfaces, allowing image light rays to be propagated and expanded into multiple rays that travel towards the field of view, with the first field of view angle being larger than the second, and the exit diffraction structure allowing these rays to reach the user efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional light guide structure is used, then the manufacturing cost is lower, but the area of the field of view region where no pupil of an image light ray is located is larger and the usage efficiency of image light ray is reduced
Solution Approach 1:
The light guide body is divided into functionally distinct regions: an in-coupling region for receiving image light rays, a reproduction region with a dividing diffraction structure for splitting light rays, and an exit diffraction structure for directing rays to the field of view. This segmentation allows each region to be optimized for its specific function, improving overall light ray usage efficiency while maintaining manufacturing feasibility through standardized manufacturing processes for each region
Solution Approach 2:
The patent employs diffraction structures with specific periodic patterns and geometric parameters to control the propagation and distribution of image light rays. By optimizing the parameters of the dividing diffraction structure (such as groove depth, width, and spacing), the system achieves improved pupil distribution and light ray utilization efficiency without requiring complex manufacturing processes
2Loss of energy
If the light guide structure is optimized to improve image light ray usage efficiency, then the usage efficiency improves, but the device complexity increases
Solution Approach 1:
The in-coupling region, reproduction region with dividing diffraction structure, and exit diffraction structure are integrated into a single light guide body, eliminating the need for separate optical components. This merging approach maintains functional complexity while simplifying the overall device structure and reducing the number of assembly steps
Solution Approach 2:
The light guide body serves multiple functions simultaneously: it acts as a structural support element, a light propagation medium, a diffraction element for pupil expansion, and a directional control component. This multi-functionality reduces the need for additional specialized components, thereby limiting the increase in device complexity
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 reduces the area of the field of view where no pupil is located, enhances image light ray usage efficiency, and decreases manufacturing costs by optimizing the optical system's design and structure.
Implementation Method 1
a reproduction region formed at the body and including a dividing diffraction structure dividing an image light ray propagating in a first propagation direction intersecting the thickness direction of the body into a plurality of image light rays propagating in a second propagation direction intersecting the first propagation direction
Implementation Method 2
a light guide for guiding an image light ray which is output from a display element and forms an image, to a field of view region of a user as a virtual image
Data Source
AI summary
The optical system includes a light guide including a reproduction region including a dividing diffraction structure dividing an image light ray propagating in a first propagation direction intersecting a thickness direction of a body, into image light rays propagating in a second propagation direction intersecting the first propagation direction, in the first propagation direction and including first and second diffraction structure regions formed respectively at first and second surfaces in the thickness direction to face each other, and an exit diffraction structure allowing the image light rays propagating in the second propagation direction to travel toward a field of view region. When first and second field of view angles in first and second directions of the virtual image are denoted by FOV1 and FOV2, a relation of FOV2/FOV1<0.5 is satisfied. The first propagation direction in the reproduction region corresponds to the first direction in a virtual image.