Simultaneous measurement of velocities and size distribution of fine atmospheric aerosols based on image processing and PTV techniques

An integrated measurement system was developed using high-speed photography, image recognition and PIV/PTV techniques to simultaneously measure the velocities and size distributions of fine atmospheric aerosols. The photographic system included a high-power (25 W) continuous laser, a microscope and a high-speed CCD camera (30–10,000 fps) could capture successive particle images on a microsecond time scale and micron space scale. The software system integrates improved image recognition algorithms for circular particles, various image-processing algorithms and advanced PIV/PTV algorithms. The information is extracted from the images in three steps: image preprocessing, particle recognition from images to obtain the diameters and positions of the particles, and the velocity vector calculation using PIV/PTV techniques. The system was tested using a computer-generated image. The results show that the particle extraction algorithms are robust and accurate. The system was also used to effectively measure fine atmospheric particles in the smoke from burning incense. Some problems are identified for future improvements.