Digital correction of residual straylight in FLEX images

Abdon, Sylvain; Armand, D.; Laurent, Florence; Barillot, Marc; D’Ottavi, A.; Coppo, P.; Luca, Emanuele De; Gabrieli, Riccardo; Bouvet, Marc; François, M.; Taccola, Matteo

doi:10.1117/12.2536079

Cited by 8 publications

(12 citation statements)

References 4 publications

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“…Previously, the Earth observation instrument POLDER [8] had a similar optical configuration and also required an algorithm to decrease the SL. With the trend of users requiring always higher performing instruments, it is likely that SL correction algorithms will become the norm in the near future of Earth observation missions (e.g., FLEX [9], ALTIUS [10], etc.). Furthermore, many other applications can benefit from this type of algorithm, including non-space optical systems.…”

Section: Introductionmentioning

confidence: 99%

Stray Light Correction Algorithm for High Performance Optical Instruments: The Case of Metop-3MI

2022

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Stray light is a critical aspect for high performance optical instruments. When stray light control by design is insufficient to reach the performance requirement, correction by post-processing must be considered. This situation is encountered, for example, in the case of the Earth observation instrument 3MI, whose stray light properties are complex due to the presence of many ghosts distributed on the detector array. We implement an iterative correction method and discuss its convergence properties. Spatial and field binning can be employed to reduce the computation time but at the cost of a decreased performance. Interpolation of the stray light properties is required to achieve high performance correction. For that, two methods are proposed and tested. The first interpolate the stray light in the field domain while the second applies a scaling operation based on a local symmetry assumption. Ultimately, the scaling method is selected and a stray light reduction by a factor of 58 is obtained at 2σ (129 at 1σ) for an extended scene illumination.

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Section: Introductionmentioning

confidence: 99%

Stray Light Correction Algorithm for High Performance Optical Instruments: The Case of Metop-3MI

2022

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“…As Fig 3 shows, the residual error at iteration p=1 increases when the initial SL level increases. A quadratic dependance is found between d𝑆𝐿 1 and the initial SL level, which can also be deduced directly from equation (9). In each case, the residual error decreases linearly on a semilog scale, characteristic of an inverse power law or an exponential decay.…”

Section: Convergence Of the Iterative Methodsmentioning

confidence: 64%

“…The residual SL error at first iteration is not always negligible, as opposed to what some authors state [9,16,17]. At convergence (𝑝 = ∞), 𝐼 𝑆𝐿,𝑝 = 𝐼 𝑆𝐿 and 𝐼 𝑐𝑜𝑟𝑟,𝑝 = 𝐼 𝑚𝑒𝑠 .…”

Section: Convergence Of the Iterative Methodsmentioning

confidence: 79%

“…At convergence (𝑝 = ∞), 𝐼 𝑆𝐿,𝑝 = 𝐼 𝑆𝐿 and 𝐼 𝑐𝑜𝑟𝑟,𝑝 = 𝐼 𝑚𝑒𝑠 . By mathematical induction, we find that the residual convergence error Δ𝑆𝐿 𝑝 at iteration p is given by equation (9). The error alternates between positive and negative values.…”

Section: Convergence Of the Iterative Methodsmentioning

confidence: 99%

“…Previously, the Earth observation instrument POLDER [8] had a similar optical configuration and also required an algorithm to decrease the SL. With the trend of users requiring always higher performing instruments, it is likely that SL correction algorithms will become the norm in the near future of Earth observation missions (e.g., FLEX [9], ALTIUS [10], etc.). Furthermore, many other applications could benefit from this type of algorithms, including non-space optical systems.…”

Section: Introductionmentioning

confidence: 99%

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Stray Light Correction Algorithm For High Performance Optical Instruments: The Case Of Metop-3MI

Clermont¹,

Michel²,

Stockman³

2022

Preprint

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Stray light is a critical aspect for high performance optical instruments. When stray light control by design is insufficient to reach the performance requirement, correction by post-processing must be considered. This situation is encountered for example in the case of the Earth observation in-strument 3MI, whose stray light properties are complex due to the presence of many ghosts dis-tributed on the detector array. We implement an iterative correction method and discuss its con-vergence properties. Spatial and field binning can be employed to reduce the computation time but at the cost of a decreased performance. Interpolation of the stray light properties is required to achieve high performance correction. For that, two methods are proposed and tested. The first interpolate the stray light in the field domain while the second applies a scaling operation based on a local symmetry assumption. Ultimately, the scaling method is selected and a stray light reduction by a factor of 58 is obtained at 2σ (129 at 1σ) for an extended scene illumination.

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Unlocking stray light mysteries in the CoRot baffle with the time-of-flight method

Clermont,

Blain,

Khaddour

et al. 2024

Sci Rep

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Stray light (SL) has emerged as a primary limiting factor for space telescopes. Pre-launch testing is essential for validating performance and identifying potential issues. However, traditional methods do not enable the decomposition and identification of individual SL contributors. Consequently, when problems arise, resolving them often involves a cumbersome and risky trial-and-error approach. The time-of-flight (ToF) method was recently introduced, employing a pulsed laser source and ultrafast sensor to characterize individual SL contributors. A proof of concept was achieved using a simple three-lens system. In this paper, we apply the ToF method to a real space optical system: the spare model of the CoRoT baffle. We successfully measured individual SL contributors over a dynamic range of 10−11, identifying direct scattering on vane edges and two-step scattering paths. Our results provide a performance breakdown, differentiating intrinsic baffle SL from contributions arising from experimental conditions. Notably, the ToF method allowed us to discriminate air scattering, eliminating the need for expensive vacuum testing. The ToF provides unparallel insights, including defects identification. For instance, we identified the presence of localized dust particles causing significant SL. These results confirm the utility of the ToF method even for the most challenging space systems.

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Digital correction of residual straylight in FLEX images

Cited by 8 publications

References 4 publications

Stray Light Correction Algorithm for High Performance Optical Instruments: The Case of Metop-3MI

Stray Light Correction Algorithm for High Performance Optical Instruments: The Case of Metop-3MI

Stray Light Correction Algorithm For High Performance Optical Instruments: The Case Of Metop-3MI

Unlocking stray light mysteries in the CoRot baffle with the time-of-flight method

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