A method for measuring particle size in overlapped particle images

This paper describes a new method to measure the sizes of particles and their probability distribution function by image processing. In the present research, an image with heavily overlapped particles was processed. The edges of the particles in the image are detected by Canny's method, and the contours are linked from the pixels in the edges by using chain-coding. The contours are subsequently segmented according to the curvature. Constant curvature segments are clustered according to some relations among contour segments which are likely to represent the same circle. The Least Squares Method which provides an accurate parameter estimation is performed to find out the parameters of a circle. The present method can recover most of particles even in a heavily overlapped particle image; It provides a useful way of investigating the structure of material or counting particles in many fields of engineering. Another advantage of the present method is its short computational time. All the computations in this paper were carried out on a personal computer, and the computational rime of processing one image was between 4-10sec on the personal computer (Pentium II, 300 MHz), which depended on the number of particles in the image. It is clear that the present research can be extended to the real-time processing of particle-detecting and particle-measuring in the future.