Particle identifying apparatus

• Main Authors: NEWMAN; CATHY D, DEVOLK; BURTON, ALLEN; FRITZ, FRAATZ; ROBERT J
• Format: Patent
• Language: English
• Published: 04.09.1990
• Subjects: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIRCHEMICAL OR PHYSICAL PROPERTIES; MEASURING; PHYSICS; TESTING

Apparatus for identifying a particulate substance in suspension based on the radiation scattering behavior of the substance, which apparatus includes a source of a collimated beam of substantially monochromatic radiation which is linearly polarized along a first polarization axis, at least two modulators disposed in the path of the polarized beam for effecting polarization modulation of the polarized beam about respective dynamic axes at respective modulation frequencies, a sample of the substance being held in the path of the beam between the modulators so that radiation is scattered by the substance in a scattering plane, a polarizing device disposed in the scattering plane for passing that portion of the scattered radiation which is parallel to a second polarization axis, and a signal processing device for producing an indication of the intensity of the radiation emerging from the polarizing device at frequencies corresponding to selected elements of a Mueller matrix which characterizes the scattering properties of the substance, the Mueller matrix being a 4x4 matrix composed of elements fij, where i and j are the row and column numbers, respectively, of each element. The signal processing device derives indications of the intensity of the received radiation corresponding to element f11 of the Mueller matrix and to selected frequency components of the received radiation, which components have amplitudes corresponding to elements f12, f34 and f44 of the Mueller matrix, and the axes are oriented for causing the radiation to contain the selected frequency components.