Scattering from reflective diffraction gratings: the challenges of measurement and verification

Kroneberger, Monika; Mezger, Andreas; Volatier, Jean-Baptiste

doi:10.1117/12.2312099

Cited by 3 publications

(1 citation statement)

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“…In our case, we are interested in the near angle signature, which includes aberration and stray light from the scatterometer optics. There are two ways to obtain the near angle signature in a focused configuration (detailed discussion in [8]):…”

Section: Albatrossttmentioning

confidence: 99%

Straylight of curved gratings: an interlaboratory comparison

Kroneberger

Tomuta

Mezger

2019

International Conference on Space Optics — ICSO 2018

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The accurate simulation of stray light is essential for the verification of the contrast requirements in optical instruments. In a spectrometer, the scattering from reflective gratings is difficult to characterize while contributing significantly to the overall system stray light and reduction of the spectrometer contrast.Curved gratings also introduce higher straylight and difficulties in the verification of their straylight compliance. Scatterometers have to be adapted to the grating curvature and thus loose some of their performance.While measuring a curved sample, this becomes part of the optical system of the scatterometer. For the AlbatrossTT and the CASI the system considering the curved sample has to be adapted to refocus the beam onto the detector. Additional aberrations modify the near angle limit, i.e. the smallest angle where the measured BRDF is higher than the system signature. Theoretical analysis of the scatterometer becomes necessary because the signature of the system is no longer directly measureable.In addition, 2D BRDF measurement is adequate for characterization of a high polished optical surface or black coatings but deems to be insufficient to characterize all features of the grating scatter function.3D measurement is essential to verify compliancy in all angular directions.Small errors in the measurement procedure or measurement setup can lead to different results. Also every scatterometer setup has its own design driven limitations effecting near angle limit and resolution. To create reasonable results those limitations have to be carefully considered.We present a set of measurements in two different laboratories with different scatterometers.

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Section: Albatrossttmentioning

confidence: 99%

Straylight of curved gratings: an interlaboratory comparison

Kroneberger

Tomuta

Mezger

2019

International Conference on Space Optics — ICSO 2018

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Computer modeling of stray light for high-resolution spectrometer

Zhang,

Wang,

Wang

et al. 2023

2023 8th International Conference on Intelligent Computing and Signal Processing (ICSP)

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Stray light and ghosts in catadioptric spectrometers: incorporating grating scatter measurements into simulations and ghost sensitivity into system design

Kroneberger

Mezger

Becker

2018

Advanced Optical Technologies

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The accurate simulation of stray light is essential for the verification of the contrast requirements in optical instruments. In a spectrometer, the scattering from reflective gratings is difficult to characterize while contributing significantly to the overall system stray light and reduction of the spectrometer contrast. In addition, the multiple diffraction orders create a ghost sensitive environment, which must be considered in the design of the instrument. In this article, we present an experimental setup for, and measurement results from, the characterization of the bidirectional scattering distribution function (BSDF) of a holographic grating for a spectrometer applied in a typical earth observation mission with demanding stray light requirements. We observed distinct stray light peaks out of the diffraction plane, which are called ‘satellites.’ The main challenges in the measurement of grating BSDFs arise from the near angle limit, the determination of the instrument signature and the selection of the appropriate sampling (2D or 3D). Following the grating characterization, the next step is to introduce these measured BSDFs into stray light simulation. We have done that by fitting appropriate functions to the measured BSDF and defining them in the optical analysis software ASAP as a user-defined BSDF. Ghost analysis is done at the spectrometer level as a sensitivity analysis of the tilts of the optical elements. Due to the ghosting of higher diffraction orders of the grating, a high sensitivity to the tilts of some of the optical elements can be seen.

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Scattering from reflective diffraction gratings: the challenges of measurement and verification

Cited by 3 publications

References 1 publication

Straylight of curved gratings: an interlaboratory comparison

Straylight of curved gratings: an interlaboratory comparison

Computer modeling of stray light for high-resolution spectrometer

Stray light and ghosts in catadioptric spectrometers: incorporating grating scatter measurements into simulations and ghost sensitivity into system design

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