Measuring dynamic light scattering of particles by using a phase modulation interferometric method

摘要

An apparatus 1 for measuring dynamic light scattering of particles using a phase modulation interference method comprising: a low coherence light source 2 such as a super luminance diode; one measuring light path 4a, 4c, irradiating the particles in a sample medium 9 and a reference light path 4b. A phase modulating means, such as a mirror 7 vibrated by a piezoelectric-transducer 8 modulates the phase of the reference beam. A spectrum measurement means 12 measures the spectrum of the interference light between the phase modulated reference beam and scattered light outgoing the sample medium. An analyser measures scattering of the particles of the sample based on at least any one order number of the order spectrums or higher order spectra corresponding to the basic frequency of the phase-modulator 7. The ratio of normalising light path, s, to mean free path, L of the particles is set to be not more than 3. The phase modulation means may modulate the physical path of light by less than the coherence length of the light source.