Mirror Mounting Structure With Segmented Supports for Surface Smoothness
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Solution Overview
Problem
Large mirrors in scientific instruments face challenges due to physical stresses induced by mounting structures, leading to irregularities on the reflecting surface, particularly when temperature varies or adhesives dry, which is exacerbated by thin mirror faceplates aiming to minimize weight.
Innovation Solution
A support structure with ribs extending perpendicular to the mirror faceplate, featuring spaced projections or mesas with distal ends that engage and secure the bottom surface, ensuring the stress-inducing area is less than the faceplate thickness to prevent deformation from reaching the reflective surface, using adhesives with compatible thermal expansion coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the mirror faceplate thickness is reduced to minimize weight, then the weight of the mirror is reduced, but the mirror becomes more susceptible to stress-induced irregularities on the reflecting surface
Solution Approach 1:
The continuous rib structure is segmented into discrete projection elements spaced apart from each other. This segmentation reduces the cumulative stress on the thin faceplate while maintaining support, as the stress from individual small-area projections does not accumulate across the entire mirror surface as it would with a continuous rib structure.
Solution Approach 2:
The support structure transitions from a uniform continuous rib to localized projections with specific geometric properties. Each projection has a distal end area specifically designed to be less than the faceplate thickness, creating localized support points that minimize stress propagation to the reflecting surface while providing adequate structural support.
2Strength
If continuous ribs are used to support the mirror faceplate, then the structural support is improved, but stress-induced irregularities on the reflecting surface increase
Solution Approach 1:
The continuous rib is divided into multiple discrete projections spaced apart along the rib length. This segmentation maintains structural support through distributed point contacts while reducing stress-induced irregularities by eliminating the continuous stress distribution that occurs with unsegmented ribs.
Solution Approach 2:
Material is removed from the continuous rib structure to create spaced projections, extracting only the essential support function while eliminating the harmful continuous stress field. The projections represent the minimum necessary support contact areas to maintain structural integrity without causing surface irregularities.
3Stability of the object's composition
If the area of support contact is increased to reduce stress, then the structural stability is improved, but stress formations reach the reflective surface causing irregularities
Solution Approach 1:
The support contacts are designed with specific local geometric properties where the distal end area of each projection is controlled to be less than the faceplate thickness. This local quality control ensures that while individual contact areas are small, the distributed arrangement provides overall structural stability without creating stress formations that reach the reflective surface.
Solution Approach 2:
The solution moves from considering only the area dimension of support contacts to incorporating the thickness dimension as a critical parameter. By designing projections where the distal end area is less than the faceplate thickness, the invention creates a three-dimensional stress distribution that decays before reaching the reflective surface, adding the thickness dimension as a protective buffer zone.
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 effectively minimizes stress-induced deformations, maintaining the smoothness of the reflective surface by limiting stress formations to beneath the reflective surface, thus enhancing the optical performance of large mirrors in instruments like telescopes.
Implementation Method 1
Each distal end defines an area with a numerical value that is less than the thickness of the planar faceplate measured in the same measurement units as the area to limit any stress formations induced in the planar faceplate
Implementation Method 2
Some irregularities in the reflecting face of the mirror may be caused by physical stresses induced by the mirror mounting structure, e.g. dimensional changes of the mirror mounting structure with temperature variation
Data Source
AI summary
An exemplary support structure for a planar faceplate includes ribs extending substantially perpendicular to a bottom surface of the planar faceplate. Spaced apart projections extend from the ribs towards the bottom surface of the planar faceplate and have distal ends that engage and are secured to the bottom surface. Each distal end defines an area with a numerical value that is less than the thickness of the planar faceplate measured in the same measurement units as the area to limit any stress formations induced in the planar faceplate due to thermal changes from reaching a top surface of the planar faceplate. Alternatively, the projections may be spaced apart mesas extending outward from a rigid material.