Virtual Image Display Device See-Through Transmittance
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Solution Overview
Problem
Existing see-through type virtual image display devices suffer from decreased see-through transmittance near the center of the visual field due to the processing of dots and scattering materials on the light-emitting region, requiring additional optical systems for high see-through transmittance, which increases device size.
Innovation Solution
A virtual image display device incorporating a light modulation element with a liquid crystal pixel, a light-blocking member, a light-guiding member, a first polarizing plate to restrict light to a specific polarization direction, a second polarizing plate to polarize image light differently, and a polarization separation lens element with refractive power to selectively act on polarized image light, allowing for improved see-through transmittance and reduced device size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If processing such as formation of dots and application of a scattering material is performed on the light-emitting region of the light-guiding plate, then image light emission is improved, but see-through transmittance decreases in the vicinity of the center of the visual field
Solution Approach 1:
The light-guiding plate is divided into two distinct regions: a light-emitting region with processed surfaces (dots and scattering materials) for image light generation, and a light-transmitting region with unprocessed smooth surfaces for high see-through transmittance. This segmentation allows each region to optimize its specific function without compromising the other.
Solution Approach 2:
Different surface qualities are applied to different regions of the light-guiding plate. The light-emitting region has processed surfaces with dots and scattering materials to enhance image light emission, while the light-transmitting region maintains smooth unprocessed surfaces to maximize see-through transmittance. This local differentiation resolves the contradiction between image quality and see-through performance.
2Reliability
If an optical system with high see-through transmittance is separately required to achieve see-through display with high see-through transmittance in the vicinity of the center of the visual field, then see-through transmittance is improved, but device size increases
Solution Approach 1:
The light-guiding plate performs multiple functions within a single component: it guides backlight for image display, emits image light through the light-emitting region, and transmits ambient light for see-through display through the light-transmitting region. This multi-functionality eliminates the need for separate optical systems, maintaining high see-through transmittance without increasing device size.
Solution Approach 2:
The patent combines the image display function and see-through display function into a single integrated light-guiding plate structure. By merging these functions into one component with regionally differentiated properties, the system achieves both high image light emission and high see-through transmittance without requiring additional separate optical systems.
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 enhances see-through transmittance while maintaining a compact device form factor by selectively polarizing and refracting light, enabling effective superimposition of image and external light for clear virtual image display.
Implementation Method 1
a first polarizing plate arranged between the light-guiding member and the light modulation element and configured to restrict light incident on the liquid crystal pixel and the light-transmitting region to polarized light in a first polarization direction
Implementation Method 2
a second polarizing plate arranged at a face side of the light modulation element and including a polarizing region provided corresponding to the liquid crystal pixel, the polarizing region being configured to restrict image light emitted from the liquid crystal pixel to polarized light in a second polarization direction different from the first polarization direction
Implementation Method 3
a polarization separation lens element arranged at a face side of the second polarizing plate and having refractive power configured to selectively act on polarized light of the image light
Data Source
AI summary
A virtual image display device includes: a light modulation element including a liquid crystal pixel and a light-transmitting region, a light-blocking member arranged at the external side of the light modulation element, a light-guiding member arranged between the light-blocking member and the light modulation element , a first polarizing plate arranged between the light-guiding member and the light-transmitting region to polarized light in a first polarization direction, a second polarizing plate arranged at the face side of the light modulation element and including a polarizing film as a polarizing region provided corresponding to the liquid crystal pixel, the polarizing film being configured to restrict image light emitted from the liquid crystal pixel to polarized light in a second polarization direction, and a polarization separation lens element arranged at the face side of the second polarizing plate that functions with respect to polarized light of the image light.