Study on the New Fine Particle Size Measurement Technique With Laser Interference Fringes

We propose one fine partice size measurement technique with laser interference fringes which is expected to achieve both non-contact and in-line measurement of the diameter of several hundred nano meter particles. However, the principle of this measurement technique with laser interference fringes is not clear and applicability of fine particle size measurement is unclear. The objective of this study is to examine the principle of this measurement technique with laser interference fringes and evaluate its applicability. We measure the flow structure in a flow cell which is the test section with Particle Image Velocimetry (PIV) to optimize the setting of the flow cell in the measurement system. From the velocity profile along the flow cell, 20 mm downward from the inlet is set as the measurement point. Next, we visualize the laser interference fringes formed with a high-speed video camera to identify the appearance and the behavior of the laser interference fringes through fine particles in the flow cell. Finally, we measure both the time variation of the intensity of the laser interference fringes and the intensity of the scattering light with photodiodes. Passage time of a particle in the laser beam and the voltage intensity have correlation each other. The effect of particle sizes on the laser signal is discussed.