Grating scattering BRDF and imaging performances: A test survey performed in the frame of the flex mission

Abstract

Key components in optical spectrometers are the gratings. Their influence on the overall infield straylight of the spectrometer depends not only on the technology used for grating fabrication but also on the potential existence of ghost images caused by irregularities of the grating constant. For the straylight analysis of spectrometer no general Bidirectional Reflectance Distribution Function (BRDF) model of gratings exist, as it does for optically smooth surfaces. These models are needed for the determination of spectrometer straylight background and for the calculation of spectrometer out of band rejection performances.

Performance of silicon immersed gratings: measurement, analysis, and modeling

“…In the figure, we compare the measurement with simulated profiles of mirrors with different surface roughness according to an adaptation of the Wein model [11,12,13] . The calculated mirror BRDF is given by Equation 2 where θ in is the input and θ s the scattering angle, σ the surface roughness (rms height) and k the wavenumber k = 2π/λ.…”

Overview on grating developments at ESA

“…----mirror 2.7 nm RMS @ 325nm 24) with a rather large aspect ratio of almost 7. The grating specifications are reported in Table 4 and straylight measurements of an early development have been published [6]. For this full size grating breadboard development IOF successfully took various measures to reduce the ghosts originating from the e-beam writing process.…”

All-dielectric prism-grating-prism component realized by direct hydrophilic bonding technology for optical applications in space

“…The blue/red (cyan/orange) curves correspond to two different measurement positions on the grating surface. The black curves show the ARS of an equivalent plane mirror with RMS roughness 1nm and 2nm, respectively according to Wein's formula7 .…”