Light Guide Diffraction Layout for Finite Virtual Image Distance
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Solution Overview
Problem
Existing display devices, such as those described in PTL 1, suffer from reduced visibility due to infinite display distance caused by uniform diffraction of image light, leading to inadequate divergence angles.
Innovation Solution
The display device incorporates a light guide body with an optical element along its emission surface, which diffracts image light to vary emission angles based on location, allowing for a finite display distance and improved visibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform diffraction is used in the optical element, then the manufacturing process is simple, but the display distance becomes infinite and visibility is reduced
Solution Approach 1:
The optical element is divided into multiple regions with different diffraction characteristics. Each region has a specific diffraction angle designed to direct light from corresponding display content to the user's eyes. This local differentiation of diffraction properties resolves the contradiction by maintaining manufacturing simplicity while achieving proper light distribution for visibility.
Solution Approach 2:
The diffraction angle parameter is varied across different regions of the optical element. By changing the diffraction angle parameter locally rather than uniformly, the system achieves finite display distance and improved visibility while maintaining a relatively simple manufacturing process using conventional diffractive optical element fabrication techniques.
2Device complexity
If a single diffraction angle is used for all regions, then the optical element structure is simple, but the image clarity is reduced due to inadequate divergence
Solution Approach 1:
The optical element employs local quality by assigning different diffraction angles to different regions. This allows each region to optimize light divergence for its specific function, maintaining image clarity while keeping the overall structure relatively simple and manufacturable.
Solution Approach 2:
The optical element is segmented into multiple functional regions, each with tailored diffraction properties. This segmentation enables precise control of light divergence for different parts of the display, improving image clarity without requiring a completely complex optical system.
3Device complexity
If divergent light emission is not implemented, then the optical system is simple, but the display distance becomes infinite and visibility is compromised
Solution Approach 1:
The system changes the emission angle parameter across different regions of the optical element to achieve divergent light emission. This creates a finite display distance that improves visibility, while the overall optical system remains relatively simple by using a single integrated optical element rather than multiple complex components.
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
By varying the divergence angle of image light across different regions of the optical element, the display device achieves a finite display distance, enhancing visibility and inhibiting reduction in image clarity.
Implementation Method 1
an optical element that is disposed along the emission surface and that diffracts the image light to emit a portion of the image light at a predetermined emission angle
Data Source
AI summary
A light guide body in a display device includes a first incident surface on which an image light is incident, and a second emission surface from which the image light is emitted. The light guide body includes a second emission optical element that diffracts the image light to emit a portion of the image light at a predetermined emission angle every time the image light enters the second emission optical element from a predetermined direction. The image light is diverged by being emitted from the second emission optical element such that the predetermined emission angle varies in accordance with a location in one predetermined region included in a plurality of predetermined regions of the optical element. The degree of divergence varies between the one predetermined region and other predetermined region included in the plurality of predetermined regions in accordance with the location of the virtual image.