Virtual-Image Display With Polarized Diffraction Lenses
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Solution Overview
Problem
Existing virtual-image display devices face challenges in reducing thickness due to optical systems that bend light paths twice, leading to limitations in further miniaturization and the need for mechanisms to pass ambient light directly.
Innovation Solution
A virtual-image display device incorporating a first and second polarized-light diffraction lens with positive power for circularly polarized light, allowing for image light to be focused while ambient light is transmitted directly, using a switching half-wave plate to switch between image and ambient light modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If an optical system with a lens and half mirror is used to bend the optical path twice, then the thickness of the virtual-image display device is reduced, but the thickness cannot be reduced further due to the reverse direction light travel section
Solution Approach 1:
The patent replaces the traditional mechanical optical system (lens + half mirror) with a polarized-light diffraction lens that integrates both imaging and polarization control functions. This substitution eliminates the need for separate components and reduces the overall thickness while maintaining the virtual image display function.
Solution Approach 2:
The polarized-light diffraction lens performs multiple functions simultaneously: it focuses light to form virtual images, controls polarization states, and enables see-through display mode. This multi-functionality reduces the number of components needed, thereby reducing thickness without sacrificing performance.
2Adaptability or versatility
If an optical system bending the optical path twice is used, then image light can be focused, but ambient light cannot be passed through directly
Solution Approach 1:
The patent applies different polarization control characteristics to different regions of the optical path. By controlling the polarization state of light at specific locations using the polarized-light diffraction lens, it enables selective transmission of image light while allowing ambient light to pass through directly in see-through mode.
Solution Approach 2:
The system changes the polarization parameter of light dynamically. By switching between different polarization states (e.g., using a liquid crystal variable retarder), the same optical system can adapt to handle both image light focusing and ambient light transmission without requiring additional mechanical components.
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
Enables thinner form factors and seamless see-through display by superimposing image light and ambient light in a time-division manner, enhancing user experience and device compactness.
Implementation Method 1
a first polarized-light diffraction lens disposed so as to be opposed to the display section and having a positive power for the image light of circularly polarized light
Implementation Method 2
polarized-light diffraction lens
Implementation Method 3
using a switching half-wave plate to switch between image and ambient light modes
Data Source
AI summary
A virtual-image display device or an optical unit includes: a display section configured to output image light; a first polarized-light diffraction lens disposed so as to be opposed to the display section and having a positive power for the image light of circularly polarized light; and a second polarized-light diffraction lens disposed so as to be opposed to the display section with the first polarized-light diffraction lens being interposed between the second polarized-light diffraction lens and the display section, the second polarized-light diffraction lens having a positive power for the image light of circularly polarized light that passes through the first polarized-light diffraction lens.