Light Guide Dispersion Elimination for Compact Virtual Image Displays
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Solution Overview
Problem
Virtual image display apparatuses face challenges in reducing size while maintaining optical accuracy, as Fresnel-shaped light guide systems often lead to image deterioration due to dispersion and chromatic aberrations caused by refractive index differences.
Innovation Solution
A light guide apparatus with a dispersion elimination section, having the same refractive index as the image extraction section, is integrated to cancel angular changes in optical paths, ensuring high-quality video light guidance and reducing apparatus thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a Fresnel-shaped member is used to guide light, then the thickness of the light guide optical system is reduced, but image deterioration occurs due to dispersion and chromatic aberrations
Solution Approach 1:
A dispersion elimination section is introduced as an intermediary component between the light source and the Fresnel-shaped member. This section is made of a material having the same refractive index as the Fresnel-shaped member to cancel angular changes in optical paths caused by dispersion, thereby preventing image deterioration while maintaining the thin profile enabled by the Fresnel structure.
2Manufacturing precision
If the refractive index of the dispersion elimination section differs from the Fresnel-shaped member, then dispersion can be eliminated, but angular changes in optical paths are not fully canceled, resulting in residual image deterioration
Solution Approach 1:
The dispersion elimination section is made of a material having the same refractive index as the Fresnel-shaped member. This homogeneity in refractive index ensures that angular changes in optical paths are fully canceled, achieving both dispersion elimination and high optical path accuracy without residual image deterioration.
3Device complexity
If a conventional light guide system is used without dispersion elimination, then the apparatus structure is simpler, but image deterioration occurs due to wavelength dispersion
Solution Approach 1:
The light guide optical system is segmented into distinct functional sections: a light incident section, a light guide section with parallel reflection surfaces, an image extraction section with Fresnel-shaped reflection surfaces, and a dispersion elimination section. This segmentation allows each section to perform its specific function optimally, achieving both structural organization and high image quality.
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 suppresses image deterioration from dispersion, allowing for a compact virtual image display apparatus with high-quality video light guidance and reduced size.
Implementation Method 1
a light guide section that has reflection surfaces facing each other and extending in parallel to each other and reflects and guides the video light acquired through the light incident section
Implementation Method 2
an image extraction section that is provided on the light exiting section and includes Fresnel-shaped reflection surfaces that deflect the video light from the light guide section to extract the video light out of the apparatus
Implementation Method 3
a dispersion elimination section that is provided in correspondence with the image extraction section and eliminates wavelength dispersion that occurs in the image extraction section
Implementation Method 4
the dispersion elimination section is made of a material having the same refractive index of the image extraction section and has reflection surfaces inclining with respect to a surface on which the video light is incident by the same angle by which the Fresnel-shaped reflection surfaces of the image extraction section incline
Data Source
AI summary
Providing an image extraction section with a plurality of video light reflection surfaces that are Fresnel-shaped reflection surfaces allows reduction in the thickness of a light guide apparatus and hence the thickness and size of a virtual image display apparatus. In particular, providing a dispersion elimination section for eliminating wavelength dispersion in correspondence with the image extraction section suppresses image deterioration resulting from dispersion (chromatic aberrations) on a wavelength band basis.