Flexure Mounting for Optical Detectors to Manage Thermal Stress

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Solution Overview

Problem

Cooled infrared cameras face challenges in reaching cryogenic temperatures quickly due to long thermal paths and stress caused by thermal expansion mismatches between optical filters and detectors, leading to prolonged cooldown times and reduced operational lifespan.

Innovation Solution

Direct mounting of optical components using flexible flexures that deform to accommodate thermal expansion differences, reducing the thermal path length and mass to be cooled, while maintaining structural rigidity and accommodating CTE mismatches.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If optical components are directly mounted to optical detectors using rigid mounting, then structural stability is improved, but thermal expansion mismatch causes stress and reduces operational lifespan

Engineering Contradiction:

Improvestructural stabilityVSAvoidoperational lifespan

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent employs flexures—flexible mechanical elements—that allow relative movement between the optical component and optical detector to accommodate differential thermal expansion. These flexures maintain structural stability while permitting stress-free adjustment during temperature changes, thereby resolving the contradiction between rigid structural stability and operational reliability under thermal cycling.

Inventive Principle:

Principle #30Flexible shells and thin films

2Reliability

If optical components are mounted away from optical detectors, then thermal expansion stress is reduced, but thermal path length increases and cooldown time is prolonged

Engineering Contradiction:

Improvestress reductionVSAvoidcooldown time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

By using flexures to enable direct mounting of optical components close to the optical detector, the patent achieves both short thermal paths for rapid cooldown and stress accommodation through flexible movement. This resolves the contradiction between proximity (fast cooling) and stress reduction.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The flexure design allows the mounting structure to change its physical parameters (flexibility, deformation) in response to temperature changes, enabling direct mounting without stress while maintaining short thermal paths.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If optical components are directly mounted to optical detectors, then cooldown time is reduced, but thermal expansion mismatch creates stress on the detector

Engineering Contradiction:

Improvecooldown speedVSAvoidthermal stress

Core Design Contradiction:

ProductivityVSStress or pressure

Solution Approach 1:

The flexure elements provide a compliant mounting solution that maintains direct physical contact for efficient heat transfer (fast cooldown) while allowing differential thermal expansion through controlled deformation, thereby eliminating thermal stress on the detector.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The flexure acts as an intermediary element between the optical component and detector, mediating the thermal and mechanical interaction. It provides both thermal conduction path and stress relief mechanism simultaneously.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 approach significantly reduces cooldown time by improving thermal conductivity and minimizing stress on the optical detector, thereby enhancing the operational lifespan and efficiency of infrared cameras.

Implementation Method 1

Each flexure is configured to deform in response to expansion or contraction of at least one of the optical component and the optical detector

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

The cold finger is configured to be cooled in order to remove heat from the platform and thereby cool the optical detector, the optical component, and the cold shield

Methodology Applied

Scientific EffectHeat removal: Heat Sink

Data Source

PatentUS11002607B2Direct mounting of filters or other optical components to optical detectors using flexures

Publication Date: 2021.05.11 RAYTHEON CO

AI summary

An apparatus includes an optical detector configured to detect at least a portion of incoming radiation. The apparatus also includes an optical component configured to provide at least the portion of the incoming radiation to the optical detector. The apparatus further includes at least one flexure that mounts the optical component to the optical detector. Each flexure is configured to deform in response to expansion or contraction of at least one of the optical component and the optical detector. Each flexure may include a side surface that is flexible in a first dimension and rigid in second and third dimensions, where the dimensions are orthogonal to each other. The optical component may include at least one of a filter, a lens, a polarizer, an aperture, and a cover.