Virtual Image Display Device with Wavelength-Selective Concave Mirror
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing virtual image display devices with transmissive reflective surfaces and concave mirrors suffer from image leakage, where the displayed image can be seen from the outside, due to incomplete reflection of image light by the concave transmissive mirror.
Innovation Solution
A virtual image display device incorporating a concave transmissive mirror with a partial reflective film that has varying reflectance properties based on wavelength, ensuring high reflectance in the display wavelength region while minimizing reflectance in other regions to prevent image leakage and enhance see-through capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If a transmissive reflective surface and concave mirror are used to guide image light, then the virtual image can be displayed, but the image can be seen from the outside causing information leakage
Solution Approach 1:
The patent applies local quality by making different regions of the reflective surface have different properties. The mirror surface is divided into a first reflective surface for reflecting image light and a second reflective surface with different reflectance characteristics. This local differentiation allows the system to reflect image light effectively while preventing external observation of the displayed image, thus resolving the contradiction between information security and display function.
Solution Approach 2:
The patent employs asymmetry by creating unequal reflectance properties between the first and second reflective surfaces. The first reflective surface has high reflectance for image light, while the second reflective surface has lower reflectance to prevent external viewing. This asymmetric design ensures that image light is properly directed for display while the asymmetric reflectance characteristics prevent the image from being seen from outside, thereby maintaining both display reliability and information security.
2Adaptability or versatility
If a transmissive mirror is used to allow external light transmission, then see-through capability is improved, but image light reflection is insufficient causing image leakage
Solution Approach 1:
The patent applies local quality by creating distinct optical properties in different regions of the mirror surface. The first reflective surface maintains high reflectance for image light while the second reflective surface has reduced reflectance to allow external light transmission. This local differentiation enables the mirror to simultaneously provide see-through capability and prevent image leakage by directing image light appropriately.
Solution Approach 2:
The patent segments the reflective surface into functionally distinct first and second reflective surfaces. This segmentation allows each region to perform its specific function: the first surface for image light reflection and the second surface for allowing external light transmission with reduced image leakage. By dividing the mirror surface into these segments, the system achieves both see-through capability and image protection.
3Reliability
If a prism member with total reflection surface is used, then image light guidance is improved, but the displayed image can be observed from outside
Solution Approach 1:
The patent extracts the problematic total reflection surface from the traditional prism member design and replaces it with a mirror surface having controlled reflectance properties. By taking out the total reflection mechanism and substituting it with a mirror that has specific reflectance characteristics, the system maintains effective image light guidance while preventing external observation of the displayed image, thus resolving the information leakage issue.
Solution Approach 2:
The patent applies parameter changes by modifying the reflectance parameter of the reflective surface. Instead of using total reflection (100% reflectance), the system employs a mirror surface with controlled reflectance parameters that allow for image light guidance while preventing external viewing. This parameter modification enables the system to maintain guidance reliability while eliminating the image visibility problem from outside.
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 leakage by reflecting image light within the intended wavelength range while allowing external light to pass through, ensuring that the displayed image is not visible from the outside and maintaining a see-through property.
Implementation Method 1
the partial reflective film has different reflectance according to wavelength
Implementation Method 2
the partial reflective film has different reflectance according to wavelength
Data Source
AI summary
An image light generation device generating image light, a semi-transmissive tilted mirror reflecting the image light from the image light generation device, and a concave semi-transmissive mirror reflecting, toward the semi-transmissive tilted mirror, the image light reflected by the semi-transmissive tilted mirror to form an exit pupil are provided, and the concave semi-transmissive mirror includes a partial reflective film having different reflectance according to wavelength, the semi-transmissive tilted mirror reflects the image light toward the partial reflective film.