Polarization-Selective Lens for Compact See-Through Displays
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Solution Overview
Problem
Existing virtual image display devices face challenges in achieving both video observation and external light observation due to the large size of the optical system when a geometric phase element is positioned outside the see-through region, as seen in systems with polarization conversion using a geometric phase element and a retarder element.
Innovation Solution
A virtual image display device incorporating a polarization-selective lens composed of a polarizing diffractive lens and an auxiliary lens, which has a positive refractive power for video light and a negative refractive power for external light, allowing for a compact design that enables both video and external light observation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a geometric phase element is disposed outside the see-through region to enable video observation, then video observation is achieved, but the optical system becomes large and external light observation is compromised
Solution Approach 1:
The patent combines the geometric phase element with the see-through region by disposing the geometric phase element inside or overlapping with the see-through region. This merging allows the optical system to maintain a compact size while achieving both video observation and external light observation functions simultaneously, resolving the contradiction between video observation capability and optical system size.
Solution Approach 2:
The geometric phase element is designed to serve multiple functions: it acts as both a video light condensing element and allows external light to pass through the see-through region. By making the optical element universal, the system achieves both video observation and external light observation without requiring separate components, thereby maintaining compact dimensions.
2Reliability
If a geometric phase element is disposed outside the see-through region, then video light can be condensed, but external light observation is blocked and the device complexity increases
Solution Approach 1:
The patent merges the geometric phase element with the see-through region, eliminating the need for separate disposal locations. This single integrated component performs both video light condensing and external light transmission, reducing device complexity and avoiding the need for complex multi-component configurations.
Solution Approach 2:
The geometric phase element is designed with universal functionality to handle both video light and external light. It condenses video light while simultaneously allowing external light to pass through the see-through region, thereby reducing the number of required components and simplifying the overall optical system configuration.
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 allows for a thinner and more compact virtual image display device that can effectively superimpose video and external light, providing clear virtual and real-world views simultaneously.
Implementation Method 1
a polarizing diffractive lens having a positive refractive power with respect to the video light that is circularly polarized light and having a negative refractive power with respect to external light that is circularly polarized light
Implementation Method 2
a polarization-selective lens that is disposed facing the display and that has a refractive power that selectively acts on polarized light of the video light
Data Source
AI summary
A virtual image display device or an optical unit includes a display configured to emit video light, and a polarization-selective lens that is disposed facing the display and that has a refractive power that selectively acts on polarized light of the video light. The polarization-selective lens includes, in order from a display side, a polarizing diffractive lens having a positive refractive power with respect to the video light that is circularly polarized light and having a negative refractive power with respect to external light that is circularly polarized light, and an auxiliary lens having a positive refractive power equivalent to a refractive power of the polarizing diffractive lens.