Plasmon resonance sensor

A plasmon resonance sensor for biological, biochemical or chemical tests, with an optically transparent body (1, 17), in particular a glass prism, a reflective metal layer (5) or semiconductor layer which is applied to one face (4) of the body (1, 17) and has a surface (6) sensitive to molecules to be detected in a sample, which forms a measurement cell in conjunction with a cuvette, a monochromatic light source (7, 15, 34 to 37, 51 to 54), in particular a laser diode, for emitting a divergent light pencil or beam path (9, 26 to 29, 39 to 42, 59 to 62) through the optically transparent body (1, 17) onto the inner face of the layer (5), and a detector (8, 22 to 25, 43 to 46, 63 to 66) which is assigned to the emerging beam path (11) reflected by the layer (5) and registers as a function of time the light emergence angle, which changes as a result of molecule buildup on the sensitive surface (6), at which an emerging light intensity minimum occurs owing to resonance, characterized in that collimation optics (13, 16, 38, 55 to 58), which collimate the incident beam path (10) perpendicularly to the incidence plane (12) but still leave it divergent in the incidence plane (12), are arranged between the light source (7, 15, 34 to 37, 51 to 54) and the optically transparent body (1, 17).