Virtual Image Display Device with Concave Transmission Mirror
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Solution Overview
Problem
Existing virtual image display devices with concave transmission mirrors face challenges in maintaining a see-through property while minimizing weight and complexity, often requiring heavy optical systems due to the need for parallel prisms which increase the overall weight and cost.
Innovation Solution
A virtual image display device incorporating a first and second reflection type diffraction element, along with a concave transmission mirror, where the first diffraction element uniformly diffracts imaging light in the vertical direction and the second element compensates for wavelength distribution, allowing the optical path to be shifted perpendicular to the optical axis, and a third reflection type diffraction element is used to prevent leakage light from being visible externally.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If parallel prisms are used to ensure see-through property, then the optical system can maintain see-through capability, but the weight and complexity of the system increases
Solution Approach 1:
The patent extracts and eliminates the heavy parallel prism structure from the optical system. Instead of using traditional parallel prisms for see-through capability, the invention employs a beam splitter combined with a concave transmission mirror, removing the unnecessary prism components while preserving the see-through function.
Solution Approach 2:
The beam splitter serves multiple functions: it reflects imaging light toward the concave transmission mirror while simultaneously allowing external light to pass through to the user's eyes. This multi-functionality replaces what previously required separate prism components, reducing overall system weight and complexity.
2Ease of manufacture
If parallel prisms are used to ensure see-through property, then the optical system can maintain see-through capability, but the device complexity increases
Solution Approach 1:
The patent merges the functions of multiple optical components into a more integrated system. The beam splitter and concave transmission mirror work together as a unified optical path management system, replacing the complex assembly of parallel prisms and reducing the number of separate components required.
Solution Approach 2:
The beam splitter performs multiple optical functions simultaneously: directing imaging light to the mirror, transmitting external light to the user, and working in conjunction with the concave transmission mirror to form the virtual image. This multi-functionality simplifies the overall device architecture.
3Weight of moving object
If the optical system is simplified to reduce weight, then the weight decreases, but the wavelength distribution compensation becomes insufficient
Solution Approach 1:
The patent introduces a diffraction grating as an intermediary element in the optical path. This grating compensates for wavelength distribution by diffracting light at different angles for different wavelengths, ensuring proper spectral compensation while working harmoniously with the simplified beam splitter and mirror 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
This configuration reduces the weight and thickness of the optical system, enhances see-through capability, and suppresses information loss by effectively managing wavelength dispersion and preventing external visibility of the displayed image.
Implementation Method 1
a first reflection type diffraction element configured to diffract imaging light from the imaging light generation device in a predetermined direction
Implementation Method 2
a second reflection type diffraction element configured to diffract the imaging light from the first reflection type diffraction element so that the imaging light reflected by the first reflection type diffraction element is compensated for wavelength distribution
Implementation Method 3
a concave transmission mirror that has a concave shape and that includes a partial reflection film reflecting a part of the imaging light and transmitting other part of the imaging light
Data Source
AI summary
A virtual image display device includes an imaging light generation device that generates an imaging light, a first reflection type diffraction element that diffracts the imaging light from the imaging light generation device, a second reflection type diffraction element diffracts the imaging light from the first reflection type diffraction element so that the imaging light reflected by the first reflection type diffraction element is compensated for wavelength distribution, and a concave transmission mirror that has a concave shape and includes a partial reflection film reflecting a part of the imaging light and transmitting other part of the imaging light. In the second reflection type diffraction element diffracts the imaging light toward the mirror and transmits the part of the imaging light reflected by the mirror.