| abstract |
An optical sensor device uses surface plasmon resonance to detect the presence of a specific material e.g. antigen in blood. A transparent body 12 is coated with a thin gold film 14 which film may be coated e.g. with an antibody material. A divergent light beam is internally reflected at the face coated with the gold film to a photodiode array 16. The dielectric conditions adjacent the gold film 14 determine the reflection angle(s) at which surface plasmon resonance resonance in the gold film reduces the intensity of reflected light to produce a dark band(s) on the otherwise uniformly illuminated detector array 16. The intensity at each detector in the array is determined, a polynomial corresponding to the light intensity distribution is calculated, and the angle of reflection for which the reflected light is a minimum is determined from the polynomial. <IMAGE> |