Design of Multiple-Tau Photon Correlation System Implemented by FPGA

The photon correlation spectroscopy (PCS) experiment can measure the distribution of particle sizes by measuring dynamic fluctuations of intensity of scattered light. A way to analyse particle sizes from PCS is to calculate the auto-correlation function of the detected intensity. In order to get accurate result, we need a photon correlator with small sampling time and large-scale dynamic range. This paper presents not only a linear photon correlator but also a multiple-tau correlator implemented by high performance Xilinx field programmable gate array (FPGA). In the photon correlator, the works of counting, delaying, multiplying and accumulating are all completed in one FPGA chip. The Verilog-HDL is adopted in the design of FPGA modules. Experimental results indicate that this correlator can be applied in the analysing of ultra-fine particle sizing.