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 (54, 56) 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 (54, 56) 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.