Light-Guiding Device Ghost Reduction via Third Surfaces
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Solution Overview
Problem
Existing light-guiding devices with half mirrors between first and second light-guiding bodies can cause ghosts due to refraction when the refractive indices of these bodies differ, making it difficult to select materials that satisfy the necessary refractive index matching condition, and external light absorption is challenging, especially in deep gaps between surfaces.
Innovation Solution
A light-guiding device with a first light-guiding body having first half mirrors and a second light-guiding body, where third surfaces are introduced between first and second surfaces, allowing light to pass through without being incident on adjacent first surfaces, and second half mirrors are used to control external light emission, ensuring uniformity and reducing ghost occurrence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the refractive index of the first light-guiding body is set different from the refractive index of the second light-guiding body, then material selection flexibility is improved, but ghost images occur due to refraction at the interfaces
Solution Approach 1:
A light-absorbing layer is introduced as an intermediary between the first light-guiding body and the second light-guiding body. This layer absorbs the light that passes through the first half mirror, preventing it from being refracted at the interfaces between light-guiding bodies with different refractive indices. The light-absorbing layer acts as a mediator that eliminates the harmful refraction effect while allowing the first and second light-guiding bodies to have different refractive indices, thus resolving the contradiction between material selection flexibility and ghost image prevention
2Object-generated harmful factors
If a light-absorbing layer is applied to the second surface to prevent ghost images, then ghost occurrence is reduced, but application difficulty increases in deep gaps between surfaces
Solution Approach 1:
Instead of directly applying the light-absorbing layer to the difficult-to-reach second surface in the deep gap, the patent forms the light-absorbing layer on the first surface (which is more accessible) and uses optical copying/projection to transfer the light-absorbing pattern to the corresponding region on the second surface. This copying approach allows the light-absorbing layer to be effectively applied in the deep gap region without requiring direct access to the difficult-to-reach second surface, thus resolving the contradiction between ghost image prevention and manufacturing ease
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 effectively reduces ghost recognition by directing light away from the observer and ensures clear external light emission, even when refractive indices differ, and facilitates easier material selection and light absorption.
Implementation Method 1
a part of the image light L0 is reflected by the first half mirrors 81 toward the opposite side from the second light-guiding body 70
Implementation Method 2
a light-absorbing layer is formed on the second surfaces 62... the light that has passed through the first half mirror 81 passes through the second surface 62 and is then incident on the third surface 63
Data Source
AI summary
A light-guiding device used in a display device includes a plurality of first half mirrors between a first light-guiding body and a second light-guiding body. Each of the first half mirrors is formed on a first surface extending along a first direction of the first surface and a second surface extending along a second direction in the first light-guiding body. The first light-guiding body includes a third surface overlapping the second surface in a direction along a third direction in which two first surfaces located on both sides of the second surface do not overlap each other between the first surface and the second surface. The third surface extends in a direction different from the first direction.