METHOD AND APPARATUS FOR QUANTITATIVE FLUORESCENCE MEASUREMENTS

Measurement of the fluorescence of a layer of cells, disposed in a well, with supernatant liquid thereabove, is greatly enhanced in sensitivity by illuminating the cell layer with a beam of light incident thereupon at a first angle and detecting fluorescence emitted by the cells with a detector which views the illuminated cells at a second angle, wherein at least one of the first or second angles is oblique to the cell layer. By so controlling the geometry of the system, the contribution to background fluorescence by the supernatant liquid is greatly minimized. Sensitivity of the technique is further enhanced by restricting the portion of the illuminated cell layer which is viewed by the detector. The technique may be applied to an apparatus for rapidly scanning the fluorescence of a plurality of samples in a multiple well plate.