Beam-Splitter Radiometric Calibration for Diffuser Degradation

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Solution Overview

Problem

Existing radiometric calibration methods for Earth Observation instruments face challenges due to bulky diffusers and mechanisms, which add mass and volume, and are prone to degradation under high-energy radiation, necessitating improved in-orbit measurement and calibration devices.

Innovation Solution

A method and device using a beam splitter to split object and calibration light beams into signal and reference paths, allowing for the determination of measurement values based on combined signals, including those from a diffuser with monitored diffusion characteristics, bypassing the need for large diffusers and mechanisms.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a large diffuser is used in the calibration subsystem, then the calibration accuracy is improved, but the instrument volume and mass increase significantly

Engineering Contradiction:

Improvecalibration accuracyVSAvoidinstrument volume

Core Design Contradiction:

Measurement precisionVSVolume of moving object

Solution Approach 1:

The calibration subsystem is divided into multiple smaller diffusers arranged in a specific configuration, replacing a single large diffuser. This segmentation maintains the required calibration accuracy while significantly reducing the overall volume occupied by the calibration unit.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The calibration subsystem components are nested within a compact housing structure, with diffusers and optical elements arranged in a space-efficient manner. This nesting approach maximizes the use of available space while maintaining calibration performance.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Measurement precision

If a large diffuser is used in the calibration subsystem, then the calibration accuracy is improved, but the instrument mass increases significantly

Engineering Contradiction:

Improvecalibration accuracyVSAvoidinstrument mass

Core Design Contradiction:

Measurement precisionVSWeight of stationary object

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The diffuser components are made from lightweight composite materials that maintain optical performance while reducing mass. This allows the calibration subsystem to achieve accurate calibration without the mass penalty of traditional large diffuser designs.

Inventive Principle:

Principle #40Composite materials

3Adaptability or versatility

If a diffuser mechanism is added to remove the diffuser from the optical path, then the calibration flexibility is improved, but the device complexity and reliability risks increase

Engineering Contradiction:

Improvecalibration flexibilityVSAvoidmechanism complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The diffuser is extracted from the main optical path and placed in a separate calibration position. This allows the diffuser to be easily inserted or removed without complex mechanisms, as it only needs to be positioned in an alternative location rather than moved along the primary optical path.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The calibration subsystem incorporates a simple movable element that allows the diffuser to be dynamically positioned between the calibration position and a storage position. This dynamic capability provides calibration flexibility while keeping the mechanism simple and reliable.

Inventive Principle:

Principle #15Dynamics

4Reliability

If a diffuser is used in the harsh space environment, then the calibration function is maintained, but the diffuser characteristics degrade due to high energy radiation

Engineering Contradiction:

Improvecalibration functionVSAvoiddiffuser lifetime

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The diffuser characteristics are measured and characterized before deployment in space. This preliminary characterization allows for the selection of diffusers with optimal radiation resistance and enables post-launch correction of any degradation effects through calibration algorithms.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The calibration subsystem includes feedback mechanisms that monitor diffuser performance over time. This feedback allows for the detection of degradation and triggers recalibration procedures or alerts for potential replacement, maintaining calibration reliability throughout the mission lifetime.

Inventive Principle:

Principle #23Feedback

5Duration of action of stationary object

If secondary diffusers are used to mitigate radiation degradation, then the diffuser lifetime is extended, but the mass and volume of the calibration unit increase

Engineering Contradiction:

Improvediffuser lifetimeVSAvoidcalibration unit mass

Core Design Contradiction:

Duration of action of stationary objectVSWeight of stationary object

Solution Approach 1:

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Inventive Principle:

Principle #1Segmentation

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

Enables precise and efficient radiometric calibration by canceling path responses and diffuser degradation effects, reducing bulkiness and maintaining calibration accuracy over the instrument's lifetime.

Implementation Method 1

a beam splitter configured to split the object light beam into a first light beam traveling along a signal path and a second light beam traveling along a reference path

Methodology Applied

Scientific EffectBeam splitting: Reflection

Implementation Method 2

the calibration light beam into a third light beam traveling along the signal path and a fourth light beam traveling along the reference path

Methodology Applied

Scientific EffectBeam splitting: Reflection

Implementation Method 3

a diffuser configured to diffuse the calibration light beam traveling along the reference path into a diffused calibration light beam with diffusion characteristics

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS12442685B2Radiometric calibration method and device

Publication Date: 2025.10.14 NEDERLANDSE ORG VOOR TOEGEPAST NATUURWETENSCHAPPELIJK ONDERZOEK TNO

AI summary

A method and device (10) for making a calibrated measurement of light from an object (E). In a first measurement window (W1), object light (LE) is received from the object (E) onto a beam splitter (11) which splits the light into a signal path (Ps) and a reference path (Pr). A first signal (S1=T·LE·Hs) is measured by a signal detection element (15s) in the signal path (Ps). A second signal (S2=R·LE·Hr) is measured by a reference detection element (15r) in the reference path (Pr). In a second measurement window (W2), calibration light (LC) is received onto the beam splitter (11). A third signal (S3=R·LC·Hs) is measured by the signal detection element (15s) in the signal path (Ps). A fourth signal (S4=T·LC·Hr) is measured by the reference detection element (15r) in the reference path (Pr). A measurement value of the object light (LE) is determined based on the measured signals (S1,S2,S3,S4).