Multiplexed multiple-{\tau} auto- and cross- correlators on a single   FPGA
  Fluorescence correlation and cross-correlation spectroscopy (FCS, FCCS) are widely used techniques to study the diffusion properties and interactions of fluorescent molecules. Autocorrelation (ACFs) and cross-correlation functions (CCFs) are typically acquired with fast hardware correlators. Here we introduce a new multiple-{\tau} hardware correlator design for computing ACFs and CCFs in real time. A scheduling algorithm minimizes the use of hardware resources by calculating the different segments of the correlation function on a single correlator block. The program was written in LabVIEW, enabling computation of two multiple-{\tau} ACFs and two CCFs on a National Instruments FPGA card (NI 7833R) in real time with a minimal sampling time of 400 ns. Raw data are also stored with a time resolution of 50 ns for later analysis. The design can be adapted to other FPGA cards with only minor changes and extended to evaluate more inputs and correlation functions. 
G\'abor Mocs\'ar, Bal\'azs Kreith, Jan Buchholz, Jan Wolfgang Krieger,   J\"org Langowski and Gy\"orgy V\'amosi
physics.optics cs.AR physics.ins-det