Abstract: A plasmon resonance sensor has an optically transparent body, a reflective layer on its one face and having a surface sensitive to molecules, a light source for emitting a divergent light through the body onto an inner face of the layer, and a detector assigned to an emerging beam path reflected by the layer and registering an angle of incidence of the light changing as a result of molecule buildups, wherein the light source is assigned a non-pointlike emission face with an extent of at least 10 &mgr;m, and a collimation lens is arranged in the emerging beam path between the optically transparent body and the detector.

Abstract: The invention relates to a plasmon resonance sensor that comprises a glass prism (1) with a gold film (2), and a light source with a non-punctiform radiating surface (5), as well as a detection optics in the form of a collimation lens (10) in the divergent beam path downstream of the reflecting gold film (2), and a detector (11). The planar radiation of light has the effect that the angle of light incidence at which the reflected light is weakened as a result of the plasmon resonance, is distributed across a stretch of the gold film, thereby preventing the gold film from being locally heated up and distorting the measurement, and reducing local inhomogeneities of the gold film. The detector (11) is all the same provided with a precise measuring signal since the collimation lens (10) collects the beams incident on the gold film with the same angle of incidence and focuses them onto the detector (11).