Virtual Image Display Device Semi-Transmissive Mirror Optical Path
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Solution Overview
Problem
Existing virtual image display devices with semi-transmissive reflection surfaces and concave surface mirrors face challenges in reducing size and weight while maintaining see-through properties, often requiring multiple prism members that increase the optical system's size and weight.
Innovation Solution
A virtual image display device configuration that includes an image light generating device, a projection optical system, a folding mirror, a semi-transmissive mirror, and a concave surface mirror, where the entrance pupil is formed between the projection optical system and the semi-transmissive mirror, allowing for a reduced size and weight by optimizing the angles and positions of these components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If two prism members are attached to each other to secure see-through property, then see-through property is improved, but weight of the optical system increases
Solution Approach 1:
The patent extracts the semi-transmissive reflection surface from the prism member structure, placing it as a separate optical element. This allows the prism member to be eliminated entirely, reducing weight while maintaining the see-through function through the semi-transmissive mirror's selective light reflection and transmission properties.
Solution Approach 2:
The semi-transmissive mirror serves multiple functions: it reflects image light toward the concave mirror while simultaneously transmitting external light to the user's eye. This multi-functionality replaces the need for multiple prism members, reducing overall system weight while preserving see-through capability.
2Ease of manufacture
If two prism members are attached to each other to secure see-through property, then see-through property is improved, but size of the optical system increases
Solution Approach 1:
By extracting the semi-transmissive reflection surface as a separate element and eliminating the prism member, the patent reduces the volumetric space required for the optical system while maintaining the see-through function through the semi-transmissive mirror's optical properties.
Solution Approach 2:
The patent reconfigures the optical path using the semi-transmissive mirror and concave mirror arrangement, changing the spatial dimensionality of light propagation. This allows for a more compact optical system layout that reduces overall size while preserving see-through capability.
3Length of moving object
If the semi-transmissive reflection surface is oriented at an angle equal to or more than 45 degrees, then width of the prism member is reduced, but weight and size of the optical system increase due to required parallel flat surfaces
Solution Approach 1:
The patent removes the prism member entirely, eliminating the constraint of requiring parallel flat surfaces for see-through property. The semi-transmissive mirror is positioned and oriented independently to achieve the desired optical effects without the structural limitations of a prism member.
Solution Approach 2:
The patent changes the orientation parameter of the semi-transmissive mirror to optimize the optical path. By adjusting the angle of the semi-transmissive mirror, the system achieves compact dimensions without requiring the rigid structural constraints of traditional prism members, thereby reducing overall weight.
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 overall size and weight of the virtual image display device while maintaining effective see-through properties and image quality, allowing for a more compact and stylish design.
Implementation Method 1
a folding mirror configured to reflect, in an intersecting direction, the image light from the projection optical system
Implementation Method 2
a semi-transmissive mirror configured to reflect a portion 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 reflected at the semi-transmissive mirror to form an exit pupil
Data Source
AI summary
A virtual image display device is provided. Included in the virtual image display device are: an image light generating device; a projection optical system configured to project image light emitted from the image light generating device; a folding mirror configured to reflect, in an intersecting direction, the image light from the projection optical system; a semi-transmissive mirror configured to reflect a portion of the image light from the folding mirror; a concave surface mirror configured to reflect, toward the semi-transmissive mirror, the image light reflected at the semi-transmissive mirror to form an exit pupil, in which an entrance pupil is formed between the projection optical system and the semi-transmissive mirror.