Patent ID: 7236250

Claim:
An apparatus for measuring a dynamic light scattering of particles in a sample medium using a phase modulation type interference method, comprising a low coherence light source, a light path dividing means for dividing light from the low coherence light source, an irradiating means for irradiating one of the lights divided by the light path dividing means to a sample medium, a phase modulation means for modulating the phase of the other of the lights divided by the light path dividing means, a spectrum measurement means for measuring the spectrum of the interference light between the phase-modulated reference light and scattered light outgoing from the sample medium, and an analyzing means for measuring the dynamic light scattering of particles of the sample medium based on a first order spectrum or a higher order spectrum corresponding to higher harmonics of a basic frequency of a phase-modulating signal appearing in the interference light spectrum measured by the spectrum measurement means, and an amount s/L obtained by normalizing a light path length s within the sample medium by a mean free path L of the particles being set to be not more than 3.