Sensor arrangement with: a housing with an opening in which a window transparent to electromagnetic waves is mounted, a light source , arranged in the housing , for generating electromagnetic waves, and a detector , arranged in the housing , for detecting electromagnetic waves coming in through the window , which have fallen from the light source through the window onto a sample adjacent to the window and have been reflected by the sample, wherein a first, circular-cylindrical chamber is arranged between the light source and the window and a second, circular-cylindrical chamber is arranged between the window or the first chamber and the detector , characterized in that within the housing on the wall of the first chamber and on the wall of the second chamber a toothing is arranged in each case, which is configured to reduce stray light travelling from the light source to the detector , in that the toothing of the first chamber is arranged in such a way that it reflects stray light in the direction of the light source , for which purpose the toothing of the first chamber comprises a multiplicity of annular teeth with surfaces which are oriented transversely to the optical axis of the light source and face the light source , and surfaces which extend obliquely outward and face the window , and in that the toothing of the second chamber is arranged in such a way that it reflects stray light in the direction of the window , for which purpose the toothing of the second chamber comprises a multiplicity of annular teeth with surfaces which are oriented transversely to the optical axis of the detector and face the window , and surfaces which extend obliquely outward and face the detector . a housing with an opening in which a window transparent to electromagnetic waves is mounted, a light source , arranged in the housing , for generating electromagnetic waves, and a detector , arranged in the housing , for detecting electromagnetic waves coming in through the window , which have fallen from the light source through the window onto a sample adjacent to the window and have been reflected by the sample, wherein a first, circular-cylindrical chamber is arranged between the light source and the window and a second, circular-cylindrical chamber is arranged between the window or the first chamber and the detector , characterized in that within the housing on the wall of the first chamber and on the wall of the second chamber a toothing is arranged in each case, which is configured to reduce stray light travelling from the light source to the detector , in that the toothing of the first chamber is arranged in such a way that it reflects stray light in the direction of the light source , for which purpose the toothing of the first chamber comprises a multiplicity of annular teeth with surfaces which are oriented transversely to the optical axis of the light source and face the light source , and surfaces which extend obliquely outward and face the window , and in that the toothing of the second chamber is arranged in such a way that it reflects stray light in the direction of the window , for which purpose the toothing of the second chamber comprises a multiplicity of annular teeth with surfaces which are oriented transversely to the optical axis of the detector and face the window , and surfaces which extend obliquely outward and face the detector . <EOS>