Variable Radius Mirror With Stepped Face And Curved Cooling Channels
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Solution Overview
Problem
Existing variable radius mirrors (VRMs) face challenges in achieving a large curvature range while maintaining structural integrity, efficient heat dissipation, and avoiding material corrosion and stress distortions, with complex 3D curves being difficult to manufacture and verify for dimensional accuracy.
Innovation Solution
The VRM design incorporates a deformable face with a protruding ring, recessed steps, and a cooling cavity with curved manifolds and channels, made from a metal with an elastic modulus less than 100 GPa, such as aluminum, to allow for greater deformation, stress distribution, and efficient cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the deformable face is made thinner to achieve a large curvature range, then the curvature adjustment range is improved, but the structural integrity and manufacturing precision deteriorate
Solution Approach 1:
The patent applies local quality by creating a stepped structure on the back surface of the deformable face, where different regions have different depths. This localized variation in geometry allows the thin deformable face to maintain spherical bending characteristics across the entire surface while compensating for edge effects, thereby achieving large curvature range without sacrificing manufacturing precision
Solution Approach 2:
The stepped structure is pre-formed on the back surface of the deformable face during manufacturing. This preliminary geometric configuration compensates for anticipated edge effects and stress distributions, ensuring that when pressure is applied, the deformable face bends uniformly in a spherical manner from the center to the edges, maintaining dimensional accuracy throughout the large curvature range
2Strength
If conventional materials like copper alloys and stainless steel are used, then the stiffness to yield strength ratio is improved, but the mass and corrosion resistance deteriorate
Solution Approach 1:
The patent changes the material parameter by selecting aluminum or aluminum alloys instead of conventional copper alloys or stainless steel. Although aluminum has a lower stiffness to yield strength ratio, this parameter change reduces the mass of the VRM significantly while still achieving the required performance through optimized geometric design and controlled deformation
3Strength
If conventional materials like copper alloys and stainless steel are used, then the stiffness to yield strength ratio is improved, but the corrosion resistance deteriorates
Solution Approach 1:
The patent changes the material parameter from copper alloys or stainless steel to aluminum or aluminum alloys. This material substitution eliminates the galvanic potential issue that causes corrosion and scale buildup in cooling channels, significantly improving reliability and corrosion resistance while maintaining adequate structural performance through design optimization
Solution Approach 2:
The patent employs composite construction by combining the aluminum mirror element with separate cooling channels and mounting structures. This composite approach allows each component to be optimized independently - the aluminum mirror element provides corrosion resistance, while other materials can be selected for structural support and cooling functions
4Temperature
If cooling channels are placed close to the mirror surface to increase heat transfer, then the heat dissipation efficiency is improved, but thermal gradients and surface irregularities worsen
Solution Approach 1:
The patent applies local quality by positioning cooling channels at different locations and depths within the mirror element structure, not uniformly close to the surface. This localized cooling approach targets specific thermal zones while minimizing thermal gradients that would cause surface irregularities, balancing heat dissipation efficiency with surface uniformity
Solution Approach 2:
The patent moves the cooling channels from a two-dimensional planar arrangement close to the surface into a three-dimensional configuration within the bulk of the mirror element. This dimensional transition allows cooling channels to be positioned at optimal depths and angles, improving heat transfer while reducing direct thermal impact on the reflective surface
5Manufacturing precision
If sharp outer edges are machined on the VRM, then the manufacturing precision is improved, but the stress concentration and service life worsen
Solution Approach 1:
The patent applies spheroidality by replacing sharp outer edges with curved or rounded edge profiles on the VRM. This curvature eliminates stress concentration points that would form at sharp corners, significantly extending the service life of the mirror element while maintaining sufficient edge definition for optical performance through controlled curvature rather than abrupt angles
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 design enables a larger curvature range with full elastic recovery, reduced weight, and prevents corrosion, while ensuring precise laser beam control and focus without thermal irregularities.
Implementation Method 1
A VRM is configured to vary a radius of curvature of a reflective mirror surface by deflecting or flexing a deformable face having the mirror surface via selective actuation of an actuator, such as via delivery of pressurized air to a cavity behind the mirror surface
Implementation Method 2
Conventional VRMs are typically made from copper alloys and/or stainless steel. These materials are selected for their ratio of stiffness to yield strength, which determines a degree to which the deformable face can be deformed while still showing a full elastic recovery
Implementation Method 3
Cooling channels are provided as close as possible to the mirror surface in order to increase heat transfer
Implementation Method 4
VRMs used in high power laser optics systems need to dissipate heat efficiently from the mirror surface
Implementation Method 5
A variable radius mirror (VRM) is a form of an adaptive optic element used in industrial laser applications to control the convergence and/or divergence of a laser beam
Data Source
AI summary
A variable radius mirror includes a mirror element having a deformable face with an outer surface incorporating a reflective element. The deformable face is deformable in response to a pressure applied by a pressure medium acting on an inner surface of the deformable face. A ring extends around a perimeter of the deformable face and protrudes from the inner surface of the deformable face. The mirror element further includes at least one of a plurality of steps recessed at different depths into the inner surface of the deformable face, a cooling cavity having a pair of manifolds between the outer surface and the inner surface of the deformable face, and a sidewall of the ring having a curved inner surface and a curved outer surface.