4.3.   RIfS Sensor Array

The Reflectometric Interference Spectroscopy (RIfS), which was initially proposed by Gauglitz and Nahm [175], evaluates the interference pattern of light, which is reflected at thin transparent films. The interference is caused by different partial beams, which are reflected in a different way at the film interfaces depending on the wavelength. Changes of the optical thickness nd of the sensitive layer can be detected as shifts of the maxima and minima of the interference pattern [176].

The RIfS sensor array shown in figure 12 contains 7 sensors allowing the application of 7 sensitive layers. The configuration of the sensor array is based on a white light source. The light is transmitted through a lens and filter system via polymer fibers to the glass substrates with 7 different polymer layers. The reflected light is transmitted to an optical multiplexer, which is directly connected to a diode array spectrometer. More details can be found else­where [177].

figure 12:  Schematic of the RIfS array setup. The yellow bubbles show the effects when analyte sorbs into the polymer layer (green before sorption of analyte, magenta after sorption of analyte).