Miniature three-mirror telescope for the thermal infrared

Abstract

In this contribution we will present different methods for analyzing straylight measurements in spectrometer gratings. For this purpose two different but very common types of gratings are investigated: a binary high resolution littrow grating and a silicon-crystel echelle reflection grating. We will present several measurements and simulations on such gratings. The focus lies in particular on the difference between grating ghosts and homogeneous scattering background. It is worked out, that the homogenous background must be evaluated by the well-established concept of "angle resolved scattering". Though, it is advantegeous to use the concept of "angle resolve efficiency" for ghost analysis. Further, a simulation method is presented that allows to calculate straylight in diffraction gratings. The method is applied for ghost and background analysis and it is shown that not only the particular type of disturbance but also the grating geometry itself affects the straylight level and distribution.