Particle sizing from Fraunhofer diffraction pattern using a digital micro-mirror device and a single photodiode

In this paper, a particle sizing method using a digital micro-mirror device (DMD) and a single photodiode was proposed. Firstly, the Fraunhofer diffraction pattern was projected onto the DMD. The integral intensity of the pattern along each line array of the DMD, referred to be a projection, was captured by the photodiode line by line at the aid of a focusing lens. Secondly, the inverse Abel transform was implemented to precisely retrieve the diffraction pattern from the projections. Thirdly, the particle size distribution was reconstructed from the diffraction pattern from the integral inversion. In addition, as only one photodiode was employed, distortions caused by the non-uniformity of multiple detectors were avoided. The center of Fraunhofer diffraction pattern could be automatically located by a hierarchical searching method. Experiments were carried out to validate the proposed method on a commercial particles plate and polystyrene latex spheres. The results demonstrated that the proposed method is effective to retrieve the diffraction pattern and particle sizes.