| abstract |
Light, pulsed or continuous at a particular wavelength (e.g. 780 nm), fluoresces a specimen. The specimen may be combinations of an antigen (e.g. rubella) labelled with a fluorescent dye, unlabeled antigen or hapten and an antibody reactive with the antigen or hapten. The light polarized in a first direction (e.g. z-axis) parallel to the electric field of the incident light and in a second direction (e.g. x-axis) perpendicular to the first direction is measured. A second specimen is then provided with the antigen and the antibody but without the dye. The same light as discussed above excites the second specimen and polarizes the light. The light polarized in the first (z-axis) and second (x-axis) directions in the second specimen is measured. These measurements are processed in a microprocessor with the measurements in the z and x directions in the first specimen to identify the antigen or, when the antigen is known, to identify the concentration of the antigen in the first specimen. When the light is pulsed, the measurements are made in a time window beginning after the initiation, and terminating before the end, of the fluorescence of the combination of the dye, the antibody and the antigen. Determinations as discussed above but without unlabeled antigen or hapten may be made of the antibody instead of the antigen. When the light is continuous, it is modulated. Measurements are made of the phase shifts in the polarized light in the z and x directions as a result of the light modulations and the decay of the fluorescence. |