Projection Optical System with Composite Refractive-Reflective Element
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Solution Overview
Problem
In projection optical systems, as the projection distance shortens, the reflecting mirror at the magnification side of the intermediate image tends to grow in size, leading to increased complexity and size requirements, which is not efficiently addressed by existing technologies.
Innovation Solution
A projection optical system comprising a first refracting optical system and a second optical system with a reflecting surface having a concavely curved shape and a second transmission surface with a convexly curved shape protruding towards the magnification side, allowing for a compact design and preventing the growth of the reflecting surface when shortening the projection distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a reflecting mirror with a concave shape is used at the magnification side of the intermediate image, then the projection distance can be shortened, but the reflecting surface grows in size
Solution Approach 1:
The patent combines the reflecting mirror with a transmissive optical element to form an integrated optical system. The reflecting surface and transmissive surfaces are merged into a single component that performs both reflection and transmission functions, allowing the reflecting surface area to remain compact while achieving short projection distance through the combined optical effects.
Solution Approach 2:
The optical element uses composite structure with different refractive index portions (first member portion and second member portion) bonded together. This composite design allows precise control of light paths through refraction at the bonding interface, enabling the reflecting surface to maintain small area while achieving the required optical power for short projection distance.
2Speed
If the intermediate image is tilted to shorten projection distance, then the projection distance decreases, but the intermediate image enlarges requiring larger reflecting surface
Solution Approach 1:
The patent changes the optical parameters by introducing refraction at the bonding interface between portions with different refractive indices. This refraction effect modifies the light path geometry, allowing the intermediate image to remain compact while achieving short projection distance, thereby preventing image enlargement that would otherwise require larger reflecting surface area.
3Device complexity
If only a reflecting mirror with concave shape is used, then the optical system is simple, but the reflecting mirror grows in size when shortening projection distance
Solution Approach 1:
The patent merges the reflecting mirror function with a transmissive optical element, creating an integrated component that performs both functions. This combination maintains relative simplicity of the optical system while preventing the reflecting surface area from growing, as the transmissive portion contributes additional optical power that reduces the burden on the reflecting surface.
Solution Approach 2:
The optical element serves multiple functions simultaneously: it acts as both a reflecting element (through the reflecting surface) and a transmissive element (through the first and second transmission surfaces with different refractive indices). This multi-functionality allows a single compact component to achieve what would otherwise require separate, larger 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
This configuration enables a compact projection optical system that maintains image quality and prevents the reflecting surface from enlarging, allowing for shorter projection distances without increasing the size of the reflecting surface, thus improving system efficiency and reducing aberrations.
Implementation Method 1
the optical element has a first member portion and a second member portion different in refractive index on an optical path of a ray passing through the optical element
Implementation Method 2
the reflecting surface has a concavely curved surface shape
Data Source
AI summary
A projection optical system has a first optical system and a second optical system. The first and second optical systems are disposed in order from a demagnification side toward a magnification side. An intermediate image is formed between a demagnification-side imaging surface and a magnification-side imaging surface. The second optical system is an optical element having a first transmission surface, reflecting surface, and second transmission surface in order from the demagnification side toward the magnification side. The first transmission surface and reflecting surface are located at one side, and the second transmission surface is located at the other side with respect to the optical axis. The reflecting surface has a concavely curved surface shape. The second transmission surface has a convexly curved surface shape protruding toward the magnification side. The optical element has a first member and a second member different in refractive index.