Abstract: The coherent imaging process of particles and the determination of particle size from their coherent images are discussed in this paper. An experimental investigation on the characteristics of coherent images of particles has been taken. It is concluded that when recording far-field number is small, the size of the particle can be measured directly by its coherent image. Using two dimensional discrete Fourier transform (DTF), a theoretical calculation of the intensity of the coherent image of a particle has been taken. Depending on the experimental and calculated results, it is found that when recording far-field number is less than 0.3 the particle size can be determined directly by the coherent images.

Key words: laser, coherent imaging of particle, photogram