Abstract: An optical probe for analyzing a sample illuminated by a laser includes an input optical fiber operably connectable to the laser where the input optical fiber has an entrance end and an exit end. The probe also includes a first beam splitter where the first beam splitter is adapted to transmit an alignment portion of a light beam from the input fiber exit end and to reflect a homodyning portion of the light beam from the input fiber. The probe also includes a lens between the input fiber exit end and the first beam splitter and a first and a second output optical fiber, each having an entrance end and an exit end, each exit end being operably connectable to respective optical detectors. The probe also includes a second beam splitter which is adapted to reflect at least a portion of the reflected homodyning portion into the output fiber entrance ends and to transmit light from the laser scattered by the sample into the entrance ends.

Abstract: A method and apparatus for analyzing a fluid containing light scattering components. The apparatus includes a laser adapted to direct abeam of light into the fluid such as a liquid containing particles, and at least two detectors to receive light scattered by the fluid, which received light is used to calculate a physical property of the fluid. A focusing lens may be used to focus the light beam to a focal waist in the fluid to enhance the degree of spatial coherence of the scattered light. The two detectors are aligned onto the focal waist and are adapted to send a signal to a data processor which correlates the signal received from said two detectors. The two detectors are spaced a substantially equal distance from the focal waist and are oriented at substantially the same angle with respect to the direction of propagation of the incident beam. The data processor is adapted to cross-correlate the signals received from the two detectors.

Abstract: Method and apparatus for determining the concentration of any of a wide range of antigen or antibody molecules with a high degree of specificity, accuracy and sensitivity. Antigen or antibody concentration is determined by effecting an agglutination reaction between carrier particles in a liquid medium, exposing the liquid medium to a beam of light, and measuring the ratio of the intensities of light scattered at two different angles as a function of antigen or antibody concentration. The unknown concentration of antibody or antigen is determined by comparison with similar measurements of the anisotropy ratio using known concentrations of the molecule being tested for. The agglutination reaction is performed using carrier particles coated with an agglutinant. The carrier particles should be fairly uniform in size and their diameter can be less than or comparable to the wavelength of light.