Symmetric Thermocentric Flexure Minimizes Yaw Error Motion

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Solution Overview

Problem

Existing optomechanical systems face challenges in distortion-free fixturing of optical flats due to thermal mismatch between fused silica or quartz flats and metal supporting structures, leading to surface distortions and warping, which affects pattern replication in micro/nano manufacturing applications.

Innovation Solution

A symmetric thermocentric flexure arrangement using a plurality of beam flexures around optical flats to minimize yaw error motion from thermal fluctuations, incorporating a double-parallelogram flexure design for enhanced radial compliance and minimal error motion, allowing for precise vertical guidance and angular alignment without friction or backlash.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If metal supporting structures are used to support optical flats, then mechanical strength and stability are improved, but thermal mismatch causes surface distortions and warping

Engineering Contradiction:

Improvemechanical strengthVSAvoidsurface planarity

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The patent changes the material parameter (thermal expansion coefficient) by using Invar alloy instead of conventional metal, and changes the structural parameter by implementing a symmetric flexure design with multiple support points, thereby achieving both mechanical strength and thermal compatibility

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite material strategy by combining Invar alloy (with thermal expansion coefficient matching optical flats) with flexible polymer materials in the fixturing system, creating a hybrid structure that provides both mechanical support and thermal compatibility

Inventive Principle:

Principle #40Composite materials

2Stability of the object's composition

If conventional metal fixturing is used, then structural stability is improved, but thermal expansion mismatch results in pattern replication errors

Engineering Contradiction:

Improvestructural stabilityVSAvoidpattern replication accuracy

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The patent changes the thermal parameter by selecting Invar alloy with matched thermal expansion coefficient, and changes the geometric parameter through symmetric arrangement of flexure elements, achieving both structural stability and pattern replication accuracy

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the harmful thermal expansion mismatch into a beneficial feature by using Invar alloy whose thermal expansion characteristics match the optical flats, allowing the structure to expand and contract together without inducing distortion

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Measurement precision

If rigid fixturing is used to constrain optical flats, then positioning accuracy is improved, but thermal fluctuations cause yaw error motion

Engineering Contradiction:

Improvepositioning accuracyVSAvoidangular alignment stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent transitions from rigid static fixturing to dynamic flexible fixturing using Invar alloy flexure elements that can adapt to thermal fluctuations while maintaining positioning accuracy through elastic deformation

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the mechanical parameter by using flexible Invar alloy structures with appropriate stiffness, allowing the system to maintain positioning accuracy while accommodating thermal-induced angular variations

Inventive Principle:

Principle #35Parameter changes

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 solution achieves distortion-free thermal expansion and minimizes yaw error motion, ensuring precise pattern transfer and replication in micro/nano manufacturing, with a 20 times larger vertical and angular range compared to conventional diaphragm flexures, while maintaining load capacity.

Implementation Method 1

A flexure arrangement includes a plurality of beam flexures arranged in a symmetric configuration around the one or more optical flats so as to minimize the error yaw motion (θz) from thermal fluctuations

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

A mismatch in the thermal coefficients of expansion of such flats and the rest of the supporting structure (made usually from metal) may result in surface distortions and warping

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS8795572B2Symmetric thermocentric flexure with minimal yaw error motion

Publication Date: 2014.08.05 MASSACHUSETTS INST OF TECH

AI summary

A stamping structure for imprinting micro-sized features is provided. The stamping structure includes one or more optical flats. A flexure arrangement includes a plurality of beam flexures arranged in a symmetric configuration around the one or more optical flats so as to minimize the error yaw motion (θz) from thermal fluctuations associated with fixturing the one or more optical flats.