Spectrometer Phase Mask Defocusing Tolerance

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Solution Overview

Problem

Current spectrometers on satellites face stability issues due to defocusing caused by mechanical deformations and thermal variations, leading to complex and costly design constraints to maintain a stable Instrument Spectral Response Function (ISRF).

Innovation Solution

Introducing a Wave Front Error (WFE) shape into the spectrometer using a phase mask to minimize sensitivity to defocus and other optical aberrations, thereby increasing tolerance and simplifying the instrument's design by relaxing mechanical and thermal constraints.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If strong optical, mechanical and thermal constraints are implemented to ensure ISRF stability, then the stability of the instrument response is improved, but the device complexity and manufacturing cost increase

Engineering Contradiction:

ImproveISRF stabilityVSAvoidinstrument design complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the optical parameter by introducing a phase mask that modifies the wavefront shape. This phase mask intentionally introduces controlled optical aberrations (parameter change) that make the ISRF insensitive to defocusing, thereby maintaining stability without requiring complex mechanical and thermal constraints

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the harmful effect of optical aberrations into a benefit. By intentionally introducing a specific wavefront error through the phase mask, the system becomes insensitive to defocusing. What would normally be considered a defect (optical aberration) is transformed into a protective feature that stabilizes the ISRF

Inventive Principle:

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

2Temperature

If strong thermal regulation strategies are implemented to control thermal variations, then the thermal stability is improved, but the manufacturing cost and design complexity increase

Engineering Contradiction:

Improvethermal stabilityVSAvoidmanufacturing cost

Core Design Contradiction:

TemperatureVSEase of manufacture

Solution Approach 1:

The patent changes the optical response characteristics by introducing a phase mask with a specific wavefront shape. This parameter change in the optical domain makes the system insensitive to thermal-induced defocusing, eliminating the need for costly thermal regulation strategies

Inventive Principle:

Principle #35Parameter changes

3Reliability

If mechanical structures are designed with high stability to guarantee performance, then the ISRF stability is improved, but the device complexity and manufacturing difficulty increase

Engineering Contradiction:

ImproveISRF stabilityVSAvoidmechanical stability requirement

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent changes the optical parameter (wavefront shape) through the phase mask to make the ISRF insensitive to mechanical defocusing. This allows for relaxed mechanical stability requirements, reducing manufacturing precision demands while maintaining ISRF stability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts mechanical defocusing, which would normally degrade performance, into a non-issue by introducing a phase mask that makes the optical response insensitive to such movements. The mechanical instability is effectively neutralized through optical design

Inventive Principle:

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

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 the sensitivity of the spectrometer's ISRF to defocusing, allowing for a more robust and simplified design with improved performance and reduced thermal regulation costs.

Implementation Method 1

Introducing a Wave Front Error (WFE) shape into the spectrometer using a phase mask to minimize sensitivity to defocus and other optical aberrations

Methodology Applied

Scientific EffectPhase mask wavefront modulation:

Implementation Method 2

a spectral dispersion grating and a photosensitive matrix detector

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentEP3564634B1Method for desensitisation of a spectrometer to defocusing by phase mask for built-in observation instruments

Publication Date: 2021.02.17 THALES SA

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AI summary

The field of the invention relates to methods for calculating the optical architecture of an observation instrument comprising a spectrometer, said instrument being subjected to a perturbation degrading its optical architecture. The spectrometer comprises an entrance slit (21), a phase mask defined by a parameter (α), and a spectral dispersion grating (23). The method according to the invention operates as follows: A maximum deviation (εFWHM) is defined as a function of the optical resolution of the spectrometer with and without the phase mask; a shape error is also defined as a function of the minimum resolution and the degraded resolution of the spectrometer comprising the phase mask. In an optimization step, the minimum of this shape error is calculated by varying the parameter (α) under the constraint that the maximum deviation εFWHM remains below a given threshold.The parameter (αMIN) corresponding to the optimum of this optimization problem is retained for the development of the phase mask.