A study of particle diffraction patterns using image processing techniques

A prototype microcomputer-based digital image processing diffractometer was constructed and tested for simultaneous measurement of a single particle's diameter and shape. The instrument used an extremely low light sensitive ({dollar}sim{dollar}2 {dollar}times{dollar} 10{dollar}sp{lcub}-6{rcub}{dollar} lux) silicon intensified target (SIT) camera to capture a particle's light diffraction pattern.; Computer programs were developed to acquire and process the particle's diffraction pattern, which was used to calculate the particle diameter. Then, a subroutine utilized a two-dimensional fast Fourier transform (FFT) algorithm to reconstruct the particle shape from its intensity diffraction pattern.; Theoretical computer simulations indicated this technique could produce simultaneous measurement of diameter and shape of a single particle. Experimental results reflected that the particle diameter could be measured. Also, particle shape reconstruction was derived experimentally by using an intensity spatial function. The reconstructed shape, while different from the original shape, retains key characteristics that can be used to recognize different particle shapes in a look-up table of shape categories. Due to the comparatively low intensity resolution of an 8-bit gray scale frame grabber, the higher intensity components of the signal were clipped. This clipping can be reduced if a spatially variant calibrated logarithmic neutral density filter is used to logarithmically compress the dynamic intensity range of the diffraction pattern.