Virtual Image Display Device Optical Axis Intersection
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Solution Overview
Problem
Existing virtual image display devices with semi-transmissive reflection surfaces and concave surface mirrors face challenges in size reduction and stylish design due to the need for multiple prisms and adjustments to correct image inclination, leading to increased weight and optical system complexity.
Innovation Solution
A virtual image display device with an image light generation device, a projection optical system, a folding mirror, a semi-transmissive mirror, and a concave surface mirror, where the optical axis of the projection optical system intersects with the optical axes of the folding and concave mirrors, and the display region is inclined to compensate for image inclination, allowing for flexible optical path design and reduced thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two prisms are bonded to form a prism member with parallel surfaces, then the optical system can guide image light properly, but the device weight increases and the concave surface mirror part bulges out with large thickness
Solution Approach 1:
The patent extracts the parallel surface requirement from the prism member design. By allowing the first and second surfaces of the prism member to have different inclinations relative to the optical axis, the patent eliminates the need for bonding two prisms together, thereby reducing device weight while maintaining proper optical path guidance through the folded mirror configuration
Solution Approach 2:
The patent changes the dimensional arrangement by folding the optical path using mirrors. Instead of extending the optical system linearly with thick prism members, the optical axis is folded back, allowing the concave surface mirror to be positioned closer to the prism member and reducing the overall thickness in the optical path direction
2Shape
If the semi-transmissive reflection surface inclination is adjusted or the projection optical system optical axis is bent to intersect the concave surface mirror center optical axis, then stylish appearance and size reduction are achieved, but image light inclination or rotation is caused requiring correction
Solution Approach 1:
The patent applies preliminary action by pre-inclining the display region of the image light generation device in the optical path direction. This anticipates the image light inclination that will occur due to the folded optical path, and compensates for it in advance, eliminating the need for additional correction mechanisms while maintaining a compact device shape
Solution Approach 2:
The patent introduces asymmetry by inclining the display region at a specific angle relative to the optical axis. This asymmetric arrangement of the display region compensates for the asymmetric folding of the optical path, ensuring that image light is properly aligned without requiring the semi-transmissive reflection surface to be adjusted or additional correction optics
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 enables a compact, stylish, and effective virtual image display device that compensates for image inclination, improving design flexibility and reducing the overall thickness of the optical system while maintaining image quality.
Implementation Method 1
a folding mirror configured to reflect the image light from the projection optical system
Implementation Method 2
a semi-transmissive mirror configured to reflect or transmit part of the image light from the folding mirror
Implementation Method 3
a concave surface mirror configured to reflect, toward the semi-transmissive mirror, the image light from the semi-transmissive mirror to form an exit pupil
Data Source
AI summary
A virtual image display device includes an image light generation device, a projection optical system configured to project image light emitted from the image light generation device, a folding mirror configured to reflect the image light from the projection optical system, a semi-transmissive mirror configured to reflect part of the image light from the folding mirror, and a concave surface mirror configured to reflect, the image light reflected by the semi-transmissive mirror to form an exit pupil, wherein an optical axis of the projection optical system is arranged in a direction intersecting a reference plane including an optical axis extending from the folding mirror to the semi-transmissive mirror and an optical axis extending from the concave surface mirror to the exit pupil, and a display region of the image light generation device is arranged inclined in accordance with inclinations of the folding mirror and the semi-transmissive mirror that are arranged.