Titanium Optical Insert for Spherically Mounted Retroreflector
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Solution Overview
Problem
Spherically mounted retroreflectors (SMRs) in laser tracker systems face challenges in precision centering and thermal expansion issues due to material coefficients of thermal expansion (CTEs), leading to inaccurate measurements and increased costs in manufacturing.
Innovation Solution
The use of a titanium optical insert with a smaller geometry and varying thickness between the cavity and the body, which reduces material usage and minimizes thermal distortion, while maintaining structural integrity and ergonomic benefits for larger SMRs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional materials (stainless steel) are used for the optical insert, then structural strength is sufficient, but thermal expansion causes apex position changes and measurement inaccuracies
Solution Approach 1:
The patent changes the material parameter from stainless steel to titanium, specifically selecting titanium for its lower coefficient of thermal expansion. This parameter change directly addresses the thermal expansion issue while maintaining structural integrity, allowing the optical insert to remain stable across temperature variations and prevent apex position shifts.
Solution Approach 2:
The patent employs a composite structure consisting of a titanium optical insert housed within a spherical body. This composite material approach combines the low thermal expansion properties of titanium with the structural requirements of the overall SMR assembly, creating a system that mitigates thermal distortion while maintaining mechanical strength.
2Adaptability or versatility
If larger SMR sizes are used, then measurement range is improved, but weight increases and ergonomics deteriorate
Solution Approach 1:
The patent changes the material density parameter by substituting stainless steel with titanium, which has approximately half the density. This parameter change enables larger SMR sizes to be used for extended measurement ranges while the weight increase is mitigated, improving ergonomics for operators handling larger retroreflectors.
3Strength
If more material is used in the optical insert, then structural integrity is improved, but thermal distortion increases and manufacturing cost increases
Solution Approach 1:
The patent changes the material's thermal properties parameter by selecting titanium, which has a lower coefficient of thermal expansion than stainless steel. This allows the optical insert to achieve the necessary structural integrity with optimized material usage, reducing thermal distortion while maintaining strength requirements.
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 solution enhances the precision and accuracy of SMRs by reducing thermal expansion issues and material usage, improving the overall performance and reducing the weight of SMRs, especially for larger sizes, thereby enhancing the reliability and cost-effectiveness of laser tracker systems.
Implementation Method 1
contrasting coefficients of thermal expansion (CTEs)
Implementation Method 2
whether do to internal geometry of the SMR or contrasting coefficients of thermal expansion (CTEs)
Data Source
AI summary
A spherically mounted retroreflector (SMR) includes a spherical body and an optical insert made of titanium to provide increased performance and lighter weight. The increased strength of titanium allows an optical insert with a smaller geometry that uses less material. The use of titanium for an optical insert also allow the thickness between the cavity of the body and the insert to vary. Titanium is lighter weight than SS which is more ergonomic for an operator. This is important for larger sizes of SMRs, such as approximately 1.5 to 3 inches in diameter.