Virtual Image Display With Asymmetric Curved Optics for Less Vignetting
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Solution Overview
Problem
Existing virtual image display devices of the light guide type face challenges in enhancing light use efficiency due to vignetting and light loss, particularly when using non-telecentric collimator optical systems that cause light to diverge away from the observer's eye, limiting the vertical visual field and reducing overall brightness.
Innovation Solution
Incorporating optical members with a curved surface shape that is non-rotationally symmetric into the propagation optical system, allowing for better control of light direction and reducing aberrations, thereby enhancing light use efficiency and enabling a wider viewing angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a non-telecentric collimator optical system is used to make light converge toward the observer's eye, then the vertical visual field is improved, but light loss due to vignetting increases
Solution Approach 1:
The patent introduces optical members with curved surfaces (specifically aspherical surfaces) into the propagation optical system. These curved surfaces redirect light beams that would otherwise be blocked by the light guide member's aperture, allowing them to reach the observer's eye. This resolves the vignetting problem caused by the non-telecentric collimator system while maintaining the improved vertical visual field.
Solution Approach 2:
The patent employs optical members with non-rotationally symmetric curved surfaces that are optimized for different directions. The asymmetric design allows for differential correction of light paths in the vertical versus horizontal directions, enabling the system to maintain wide vertical visual field while minimizing light loss through targeted redirection of only the necessary light beams.
2Illumination intensity
If multiple mirrors or microstructures are provided in the light guide member to extract images, then the viewing angle is improved, but the device complexity increases
Solution Approach 1:
The patent combines the functions of image extraction and light direction control into a single integrated light guide member design. Rather than adding separate mirrors or microstructures, the invention uses the light guide member's own geometry and the propagated light's characteristics to achieve both wide viewing angle and simplified structure.
Solution Approach 2:
The patent extracts only the necessary light beams for image formation by optimizing the propagation optical system to direct light efficiently into the light guide member. This selective extraction approach achieves wide viewing angle without requiring additional complex extraction structures within the light guide member.
3Illumination intensity
If the optical pupil position is extended to make light converge, then the vertical visual field is improved, but the aperture region for light passage becomes narrower
Solution Approach 1:
The curved surface optical members expand the effective aperture region by redirecting light beams that would otherwise pass outside the narrow aperture region. The curved surfaces act as additional light pathways, effectively increasing the usable aperture area without changing the physical dimensions of the light guide member.
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 improves light use efficiency by directing more light towards the observer's eye, resulting in a brighter and wider-angle virtual image display, while also reducing the device's thickness and weight, enhancing user comfort.
Implementation Method 1
an optical member having a curved surface shape that is non-rotationally symmetric with respect to an optical axis is inserted in the propagation optical system
Implementation Method 2
guides the propagated image light with the light guide member to emit the image light toward an observer as reflected light
Data Source
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Figure 3A
AI summary
A virtual image display device includes: an image display element that displays an image to be displayed as a virtual image; a propagation optical system that propagates light from the image display element; and a light guide member that guides the light propagated by the propagation optical system. The light guide member includes: a light beam incident part that introduces light including image information from the propagation optical system into the light guide member; an image extractor that extracts the light including image information from an inside of the light guide member; and an image emitter that emits the light including image information to an outside of the light guide member. The propagation optical system includes one or more optical members each having a curved surface shape that is non-rotationally symmetric with respect to an optical axis.