Thermal-Compensated Spacer Assembly for Optical Alignment Stability
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Solution Overview
Problem
Optical elements in systems exposed to varying temperatures experience significant thermal stress and misalignment due to mismatched thermal expansion coefficients between materials, leading to deformation and vibration, particularly in airborne systems.
Innovation Solution
A temperature-compensated spacer assembly using a frame with differing thermal expansion materials and geometries to achieve a high effective thermal expansion coefficient, maintaining rigidity and accommodating thermal deformation through resilient members and flexible elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If flexible elements are used to accommodate dimensional variations, then thermal expansion mismatch is reduced, but vibration of components increases
Solution Approach 1:
The spacer employs a frame structure with specific geometry (diamond-shaped opening with diagonals at right angles) made from material with high thermal expansion coefficient. The frame is designed so that its thermal expansion along the first diagonal compensates for the dimensional changes between the optical element and support structure, maintaining stable spacing without flexible elements that would cause vibration.
Solution Approach 2:
The spacer combines materials with different thermal expansion coefficients - the frame uses high expansion material (such as aluminum or aluminum alloy) while the optical element uses low expansion material (such as fused silica). This composite approach allows the spacer to bridge the thermal mismatch between components, accommodating expansion differences while maintaining rigidity.
2Object-affected harmful factors
If rigid mounting is used to prevent vibration, then component stability is improved, but thermal stress and deformation increase
Solution Approach 1:
The spacer design changes the thermal expansion parameter by using high expansion material for the frame and designing the geometry such that the effective expansion along the first diagonal matches the required compensation. The right-angled diagonals and specific arm configurations allow the structure to expand in a controlled manner, converting thermal stress into useful dimensional compensation.
Solution Approach 2:
The frame's thermal expansion is harnessed to compensate for the mismatch between optical element and support structure. By designing the frame with high expansion material and specific geometry, the spacer actively expands or contracts with temperature changes to maintain proper spacing, preventing both vibration and excessive thermal stress.
3Adaptability or versatility
If frame geometry is optimized for thermal compensation, then effective thermal expansion coefficient increases, but manufacturing complexity increases
Solution Approach 1:
The frame employs asymmetric geometry with a diamond-shaped opening where the two diagonals have different lengths and serve different functions. The first diagonal (longer) provides thermal compensation, while the second diagonal (shorter) provides structural support. This asymmetric design allows optimization of thermal compensation performance while maintaining manufacturability through clear geometric definitions.
Solution Approach 2:
The frame is segmented into four arms extending from corner regions, with each arm having specific dimensional relationships (width at least 5 times greater than thickness). This segmentation allows independent optimization of each arm's thermal and mechanical properties, simplifying manufacturing while achieving the desired thermal compensation through the collective behavior of the segmented structure.
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
The spacer assembly effectively compensates for thermal expansion, minimizing stress and misalignment, ensuring precise alignment and stability across temperature variations.
Implementation Method 1
there is a significant mismatch between the coefficients of thermal expansion between the mirror and the support, potentially leading to stress and possible deformation of the optical element
Implementation Method 2
providing a frame element which undergoes deformation, typically to reduce the magnitude of thermal expansion or contraction
Data Source
Figure 1~2
Figure 3A~3B
Figure 4~5
AI summary
A temperature compensated spacer includes first and second anchoring configurations for anchoring the spacer relative to first and second elements, and a frame providing a mechanical connection between the anchoring configurations. The frame has a polygonal opening with a first diagonal extending across the width of a gap between the elements and a second diagonal extending transversely to the first diagonal. A crossbar is associated with the polygonal opening so as to span the second diagonal. The frame and the crossbar are formed from materials having differing coefficients of thermal expansion. The crossbar is deployed so as to determine a length of the second diagonal such that variation in temperature causes deformation of the frame, thereby varying a length of the first diagonal.