A localized dynamic light scattering measurement system comprising:
- a two-frequency laser source for producing an input laser beam propagating along an optical axis and composed of orthogonal linearly polarized first and second beam components with slightly different frequencies;
- a beam splitter disposed on the optical axis for transmitting a portion of the input laser beam produced by said two-frequency laser source such that the portion of the input laser beam transmitted by said beam splitter serves as an incident beam;
- a beam displacer for splitting the incident beam into orthogonal linearly polarized first and second output beams corresponding respectively to the orthogonal linearly polarized first and second beam components, the orthogonal linearly polarized first and second output beams being parallel to the incident beam and being spaced apart from each other by a predetermined spacing upon exiting said beam displacer;
- a focusing lens unit for focusing the orthogonal linearly polarized first and second output beams onto an object to be measured and collecting light backscattered from the object upon the orthogonal linearly polarized first and second output beams striking the object;
- an iris disposed between said beam splitter and said beam displacer, and having an opening aligned with the optical axis for permitting the incident beam to pass through to limit a spot size of the incident beam;
- wherein said beam displacer serving as a polarization gate cooperates with said iris serving as a spatial filter gate to collect and recombine scattering beams each reversely backscattered at 180 degrees from the object and corresponding to a specific portion of the light collected by said focusing lens unit, so as to form a signal beam to be detected that passes through said opening in said iris;
- a polarizer for polarizing the signal beam from said iris to produce, along a polarization axis of said polarizer, first and second polarization components with common polarization;
- a photo detecting unit receiving the first and second common polarization components from said polarizer to detect and generate a heterodyne interference signal associated with the first and second common polarization components, and converting the heterodyne interference signal into an electrical signal;
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- a signal processing unit connected electrically to said photo detecting unit for receiving the electrical signal therefrom, said signal processing unit being operable to analyze the electrical signal received thereby to generate power spectrum data and autocorrelation data corresponding to the heterodyne interference signal and obtain measurement data on the object based on the power spectrum data or the autocorrelation data.