Virtual Image Display Device Astigmatism Reduction
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Solution Overview
Problem
Existing head-up display technologies require a large viewing distance to minimize double images, which is not ideal and can be improved regardless of the viewing distance to enhance virtual image visibility.
Innovation Solution
A virtual image display device with a display unit positioned nearer the focal point within the meridional plane of a composite optical system formed by the projection optical system and the virtual image presentation plate, utilizing a combination of a convex lens and a concave mirror to align light paths and reduce astigmatism, thereby eliminating double images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a large viewing distance is used to reduce double images, then double image occurrence is reduced, but the viewing distance requirement becomes excessive and visibility is compromised
Solution Approach 1:
The patent changes the optical parameters by positioning the display unit at a specific location between the meridional and sagittal focal points, and by adjusting the curvature radius of the concave mirror, to eliminate double images without requiring excessive viewing distance
Solution Approach 2:
The patent uses a virtual image presentation plate (windshield) to create a virtual image that appears at a comfortable viewing distance, effectively copying the display content to a position where double images are eliminated while maintaining visibility
2Object-affected harmful factors
If the display unit is positioned at the focal point to eliminate double images, then double image occurrence is reduced, but astigmatism increases and visibility deteriorates
Solution Approach 1:
The patent applies different optical characteristics to different regions by positioning the display unit at a specific point between the meridional and sagittal focal points, creating a localized optimal viewing zone that reduces both double images and astigmatism
Solution Approach 2:
The patent introduces asymmetric positioning relative to the two focal points (meridional and sagittal) to balance the optical path differences, thereby reducing astigmatism while eliminating double images
3Object-affected harmful factors
If conventional optical arrangements are used, then the system is simple, but double images occur and visibility is poor
Solution Approach 1:
The patent employs a concave mirror with a specific curvature radius to focus light and eliminate double images, using curved optical surfaces to achieve better image quality without excessive system complexity
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 reduces the occurrence of double images and improves the visibility of virtual images, allowing for clearer presentation of information at any viewing distance without the need for expensive wedge glasses, while maintaining high resolution and reducing astigmatism.
Implementation Method 1
a projection optical system that includes at least a concave mirror (18) for reflecting the image display light toward a virtual image presentation plate (22)
Data Source
Figure 1~2
Figure 3~4
AI summary
A virtual image display device 10 includes: a display unit 14 that generates an image display light L by modulating an illumination light; and a projection optical system 16 that includes at least a concave mirror 18 for reflecting the image display light L toward a virtual image presentation plate 22. The display unit 14 is provided at a position nearer a focal point 26m within a meridional plane of a composite optical system 20 formed by the virtual image presentation plate 22 and the projection optical system 16 than a focal point 26s within a sagittal plane of the composite optical system 20.