Abstract: An optical biosensor system using internal reflection versus angle of incidence determination for the detection of biomolecules, the system comprising a sensor unit (10) with at least two sensing surfaces (39A-D), a source of light (1), and lens means (2) for forming a convergent beam of light which is focused in wedge-shape fashion to form a streak of light (5) extending transversely over all the sensing surfaces; a photodetector device (7) in the form of a two-dimensional matrix of individual photodetector; optical imaging instrumentation in the form of an anamorphic lens system (6) for the purpose of imaging rays of reflected light from the sensing surfaces on each its own column of photodetectors, so that for each sensing surface there is a corresponding set of columns of photodetectors; and an evaluation unit (8) for determining the minimum reflectance or the resonance angle at each of the sensing surfaces.