result according to the invention optical components such as lenses screens or filters can be used fig3 shows the principle of the measuring device according to the invention as used with a pressure sensor 62 the pressure sensor 62 comprises a housing 64 with a pressure connection inlet and or outlet 66 in the housing 64 a movable membrane 68 which has an area 70 of which the shape is stable said area 70 being attached to the housing 64 via flexible areas 72 74 so that it is sealed but displaceable is arranged the membrane 68 delimits a pressure chamber 76 the membrane 68 is prestressed into an initial position via a compression spring 78 into the pressure chamber 76 on its side facing away from the pressure chamber 76 it has a scattering reflecting surface 78 on the side of the membrane 68 facing away from the pressure chamber 76 on the housing 64 a module 80 with a pair of light source and light receiver is arranged and as described in relation to fig2 it emits a light beam to the membrane and receives scattered reflected light from the membrane the distance d which is given by the measurement result which the module 80 determines regarding the light intensity describes the present compression state of the compression spring 78 relative to an initial state d from this taking account of the known spring constant c of the compression spring 78 according to hooke 39 s law f c d u2212 d the spring force f which is exerted on the compression spring 78 can be calculated directly once the movable area a of the membrane 68 is also known the pressure p in the pressure chamber 76 can be calculated directly.