Light Guide Plate with Angled Reflection Units for Virtual Image Display
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Solution Overview
Problem
In virtual image display apparatuses, such as head-mounted displays, the existing light guide plates suffer from low light use efficiency due to image light with large total reflection angles not being effectively utilized, leading to luminous flux loss and reduced image formation efficiency.
Innovation Solution
A light guide plate design featuring a light incident part, a light guide part with total reflection surfaces, and an image extraction part with strategically arranged reflection units that have a first and second reflection surface forming a predetermined angle, where the distance between these surfaces and the light exiting surface is narrower on the reflected light incident part side, allowing more image light to be efficiently extracted and directed towards the observer's eyes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the light guide plate uses a conventional reflection layer with sawtoothed cross section, then the structure is simple and easy to manufacture, but image light with large total reflection angles cannot be made incident on the reflection layer and passes through without being used, lowering light use efficiency
Solution Approach 1:
The image extraction part is divided into multiple reflection units arrayed in a predetermined direction. Each reflection unit has first and second reflection surfaces forming a predetermined angle, creating segmented reflection zones that can capture and redirect image light at different angles, thereby improving light use efficiency while maintaining manufacturing feasibility
Solution Approach 2:
The light guide plate employs different structures in different regions: the light guide part has total reflection surfaces for guiding light, while the image extraction part has reflection units with specific angled reflection surfaces. This local differentiation allows each region to perform its function optimally, capturing image light that would otherwise be lost
2Loss of energy
If the space between the first and second reflection surfaces of the reflection units and the light exiting surface is made narrow on the reflected light incident part side, then more image light with large total reflection angles can be made incident on the image extraction part and efficiently extracted, but the structure becomes more complex
Solution Approach 1:
The distance from the first and second reflection surfaces to the light exiting surface varies along the arraying direction of the reflection units. This dynamic spatial arrangement allows the structure to adapt to different light paths, capturing image light with large reflection angles more effectively while managing structural complexity through a systematic gradient design
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 design enhances light use efficiency by ensuring that image light with large total reflection angles is effectively bent and extracted, improving image formation and reducing luminance unevenness, thereby increasing the overall brightness and uniformity of the virtual images displayed.
Implementation Method 1
a light guide part which has first and second total reflection surfaces extending to face each other and guides the image light taken in from the light incident part by total reflection on the first and second total reflection surfaces
Implementation Method 2
an image extraction part which includes plural reflection units arrayed in a predetermined arraying direction and having a first reflection surface and a second reflection surface forming a predetermined angle with the first reflection surface, and which enables extraction of the image light to outside by bending an optical path in the reflection units so that the image light guided by the light guide part is reflected by the first reflection surface and the image light reflected by the first reflection surface is further reflected by the second reflection surface
Data Source
AI summary
Since a distance from an image extraction part to a light exiting surface is shorter downstream in an optical path than upstream in the optical path in relation to Z direction that is an arraying direction of reflection units, image light that propagates to pass between the image extraction part and the light exiting surface without becoming incident on the reflection units and therefore cannot be extracted to outside can be reduced. That is, since image light having a large total reflection angle in a light guide plate can be securely made incident on the image extraction part and efficiently extracted from the light exiting surface, light use efficiency in image formation can be enhanced. Thus, a virtual image display apparatus with brightness and high performance can be provided.