Virtual Image Display Optical System with Folding Mirror
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Solution Overview
Problem
Existing virtual image display apparatus with semi-transmissive reflective surfaces and concave mirrors face issues of increased weight and size due to the need for parallel prism members and protruding optical systems, which compromise see-through properties and overall compactness.
Innovation Solution
The virtual image display apparatus incorporates a folding mirror disposed between the semi-transmissive reflective surface and the concave mirror, optimizing the angle of the semi-transmissive reflective surface to less than 45 degrees, allowing for a more compact design by preventing the folding mirror from overhanging and reducing the thickness of the optical system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the semi-transmissive reflective surface is inclined at 45 degrees or greater to reduce prism member width, then the thickness in the thickness direction can be made small, but two prism members need to be affixed together to ensure see-through properties, increasing weight and requiring the concave mirror to be thickened and bulged
Solution Approach 1:
The patent extracts the folding mirror function from the prism member structure. Instead of using two prism members affixed together to achieve both folding and see-through properties, the invention uses a separate folding mirror disposed between the semi-transmissive reflective surface and the concave mirror. This separation allows each component to be optimized independently, reducing the overall weight while maintaining the thickness reduction benefit of the 45-degree inclined semi-transmissive reflective surface.
2Length of moving object
If the semi-transmissive reflective surface is inclined at 45 degrees or greater to reduce prism member width, then the thickness can be minimized, but the projection optical system and prism mirror protrude to the forehead side, enlarging the entire optical system
Solution Approach 1:
The invention extracts the folding mirror as a separate component positioned between the semi-transmissive reflective surface and the concave mirror. This extraction allows the projection optical system and folding mirror to be arranged without protruding to the forehead side, as the folding mirror is integrated into the space between the semi-transmissive reflective surface and concave mirror rather than being attached to the external side.
Solution Approach 2:
The patent repositions the folding mirror in a different spatial arrangement - between the semi-transmissive reflective surface and the concave mirror rather than on the external side. This dimensional reorganization allows the optical system to maintain compactness in the forehead direction while still achieving the thickness reduction benefit of the inclined semi-transmissive reflective surface.
3Ease of operation
If a prism mirror of optical path bending mirror is provided separately from the prism member, then the folding function is achieved, but the projection optical system and prism mirror must be arranged protruding to the forehead side, enlarging the optical system
Solution Approach 1:
The invention extracts the folding mirror as a separate component and positions it between the semi-transmissive reflective surface and the concave mirror. This extraction allows the folding function to be achieved without requiring the projection optical system and prism mirror to protrude to the forehead side, as the folding mirror is integrated into the internal space of the optical system.
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 minimizes the overall size of the optical system, enhances compactness, and maintains see-through properties, resulting in a more lightweight and aesthetically pleasing virtual image display apparatus.
Implementation Method 1
a folding mirror configured to reflect the image light from the projection optical system in an intersection direction
Implementation Method 2
a semi-transmissive reflective surface configured to reflect a part of the image light from the folding mirror
Implementation Method 3
a concave mirror configured to reflect the image light reflected by the semi-transmissive reflective surface toward the semi-transmissive reflective surface forming an exit pupil
Data Source
AI summary
A virtual image display apparatus 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 in an intersection direction, a semi-transmissive mirror configured to reflect a part of the image light from the folding mirror, and a concave mirror configured to reflect the image light from the semi-transmissive mirror forming an exit pupil, in which the folding mirror is disposed between the semi-transmissive mirror and the concave mirror when viewed in a first direction, provided that the first direction is a direction from an intersection point between a projection optical axis that is an optical axis of the projection optical system and the folding mirror toward an emission optical axis that is an optical axis from the concave mirror toward the exit pupil.