Time-resolved multispectral fluorescence imaging system based on compressed sensing (Conference Presentation)

Time-resolved multispectral imaging has recently found many applications ranging from biomedical to environmental field. Multidimensional approach measuring spectral and ultrafast temporal dynamics of fluorescence signal combined with spatial information (imaging) allows one to characterize biological processes at both microscopic and macroscopic level, representing a fundamental step towards development of diagnostic strategies. Long acquisition time is the main drawback of multidimensional approach because it is not compatible with biological system dynamics. In order to reduce the measurement times, it is necessary to parallelize the acquisition (hardware level) and to optimize the acquisition strategy to reduce the measurements number while preserving the information content. In this work we have developed a time-resolved multispectral fluorescence imaging system based on a spad array combined with compression techniques which allows to reduce the number of time-resolved acquisitions by a factor < 70%. The system is based on a double DMD configuration (excitation and detection) coupled to a 32x1 SPAD array, each one with its own TCSPC circuit, placed after an imaging spectrometer. This allows one to use the spatial modulation of the excitation/detection light to acquire images at different wavelengths following the single pixel camera (SPC) scheme. In order to compress the number of acquisitions, a CW fluorescence image is acquired through a CCD and Hadamard transform is applied to select most significative coefficients. The patterns related to these coefficients are subsequently used for SPC acquisition for time and spectral resolution. A Total-Variation based algorithm is used for the reconstruction of the 4D images.