Virtual Image Display Device with Stepped Light-Guiding Member
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing virtual image display devices face challenges in widening the angle of view without increasing the overall size, as the surface reflecting the image light becomes wider, leading to a larger light-guiding member and a less compact design that fits the observer's head.
Innovation Solution
A virtual image display device with a light-guiding member that includes a step portion creating a difference in thickness between adjacent surfaces, allowing for a more compact design while maintaining a wide angle of view, achieved by configuring the light-guiding member with specific thickness ratios and surface orientations to guide video image light effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the light-guiding member is designed with a conventional uniform thickness to guide image light, then the angle of view can be widened, but the overall size of the light-guiding member increases
Solution Approach 1:
The light-guiding member employs varying thickness across different regions: a first thickness in the region between the incident-side light-guiding surface and the opposing light-guiding surface, and a second thickness (greater than the first) in the region between the emission-side light-guiding surface and the opposing light-guiding surface. This local differentiation allows the incident-side surface to be positioned closer to the opposing surface, shortening the light guide length and reducing overall device size, while the emission-side surface maintains adequate distance for wide angle of view performance
Solution Approach 2:
The invention transitions from a conventional uniform-thickness design to a stepped thickness configuration, effectively utilizing the thickness dimension to resolve the contradiction. By creating a step portion where the thickness changes from the first region to the second region, the design achieves compactness in the incident-side region while preserving optical performance in the emission-side region
2Volume of moving object
If the light-guiding member is made compact to fit the observer's head, then the overall size is reduced, but the angle of view becomes limited
Solution Approach 1:
The emission-side light-guiding surface is positioned at a greater distance from the opposing light-guiding surface (second thickness) compared to the incident-side surface distance (first thickness). This local quality differentiation ensures that the emission region maintains sufficient space for wide angle of view light guidance, while the incident region is compact
3Adaptability or versatility
If the surface reflecting image light is widened to increase angle of view, then the angle of view is improved, but the light-guiding member becomes larger
Solution Approach 1:
The incident-side light-guiding surface is positioned closer to the opposing light-guiding surface, creating a shorter light guide length in the incident region. This local thickness differentiation allows the reflecting surface area to be increased for wider angle of view without proportionally increasing the overall device length
Solution Approach 2:
By utilizing the thickness dimension to create a stepped configuration, the invention allows the light-guiding member to have a larger surface area for image reflection (improving angle of view) while maintaining a compact overall length through the varied thickness profile
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 solution enables a compact shape that fits the observer's head while achieving a wide angle of view, ensuring reliable image formation and see-through functionality without excessive size increase.
Implementation Method 1
a light-guiding member configured to guide video image light from the video image element by reflection and transmission at a plurality of light-guiding surfaces
Implementation Method 2
a light-guiding member configured to guide video image light from the video image element by reflection and transmission at a plurality of light-guiding surfaces
Data Source
AI summary
A virtual image display device includes a video image element that displays an image, and a light-guiding member that guides video image light from the video image element by reflection and transmission at a plurality of light-guiding surfaces. Among the plurality of light-guiding surfaces, with respect to an incident-side light-guiding surface and an emission-side light-guiding surface that are adjacent to each other, and an opposing light-guiding surface that faces the incident-side light-guiding surface and the emission-side light-guiding surface, a thickness from the incident-side light-guiding surface to the opposing light-guiding surface is caused to be smaller than a thickness from the emission-side light-guiding surface to the opposing light-guiding surface.