Virtual Image Display Ghost Light Suppression via Asymmetric Reflective Surfaces
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Solution Overview
Problem
Existing virtual image display apparatuses suffer from ghost light issues due to unintentional reflection of outside light within the light guide member, particularly at the connection portions of adjacent reflective surfaces, which affects image visibility and size reduction constraints.
Innovation Solution
The virtual image display apparatus incorporates a light guide member with specific reflective surface configurations, where the first reflective surface protrudes beyond the second reflective surface at the connection portion, or forms an inclined connection surface, to direct outside light reflections away from the optical path downstream, preventing ghost light formation and ensuring satisfactory image visibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the light guide member uses adjacent reflective surfaces to guide video light, then the apparatus achieves compact size, but outside light is unintentionally reflected and guided causing ghost light that degrades image visibility
Solution Approach 1:
The first reflective surface is designed to protrude beyond the second reflective surface at the connection portion, creating an asymmetric configuration. This asymmetry ensures that the connection portion extends from a side close to the observer toward a side away from the observer, causing reflected outside light to be directed outward or upstream rather than downstream where it would create ghost light. This resolves the contradiction by maintaining compact size while eliminating the symmetric connection that causes harmful reflections.
Solution Approach 2:
Instead of having the connection portion extend in the conventional direction (from upstream to downstream), the invention inverts the extension direction by making the first reflective surface protrude beyond the second. This inversion changes the reflection geometry so that outside light reflected at the connection portion is directed away from the optical path downstream, preventing ghost light formation while maintaining the compact light guide structure.
2Ease of manufacture
If the connection portion of adjacent reflective surfaces is designed conventionally, then manufacturing is simplified, but outside light reflection creates ghost light reducing image visibility
Solution Approach 1:
The asymmetric design where the first reflective surface protrudes beyond the second reflective surface provides a straightforward manufacturing approach. The connection portion naturally extends in a specific direction (from observer-close side to observer-far side), which can be achieved through standard fabrication processes. This asymmetric configuration simultaneously prevents ghost light by directing reflections away from the optical path, thus maintaining both ease of manufacture and image visibility reliability.
3Object-affected harmful factors
If the first reflective surface protrudes beyond the second reflective surface, then ghost light is suppressed, but the light guide member structure becomes more complex
Solution Approach 1:
The asymmetric configuration where the first reflective surface protrudes beyond the second reflective surface is implemented as a simple geometric modification rather than a complex multi-component structure. The connection portion between adjacent reflective surfaces is designed to extend in a specific direction, which can be achieved through straightforward fabrication processes. This approach suppresses ghost light effectively while minimizing structural complexity, as it modifies the existing light guide geometry rather than adding separate 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
This configuration effectively suppresses ghost light generation, enhancing image visibility and allowing for a more compact design by controlling the optical path of outside light reflections within the light guide member.
Implementation Method 1
a light guide member which has a plurality of reflective surfaces, guides video light from the video element by reflecting video light by an inner surface thereof
Implementation Method 2
allows an observer to visually recognize an outside world image
Data Source
AI summary
In a connection portion connecting a first reflective surface and a second reflective surface, the first reflective surface positioned relatively on an incidence side of video light is made to protrude toward an observer side beyond the second reflective surface positioned relatively on an emission side of video light, and a connection surface which is a surface of the connection portion is shaped to extend from a side close to the observer toward a side away from the observer between the first reflective surface and the second reflective surface.