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Time-resolved imaging is a valuable tool for biomedical applications such as Diffused Optical Tomography (DOT) and Fluorescence Lifetime Imaging (FLIM). The first one characterizes and localizes absorption/scattering heterogeneities, which can be representative of tumors, and is routinely used for brain functional imaging. FLIM provides relevant information (e.g. pH, ion concentration and FRET) in cell biology and find application in molecular imaging for preclinical studies in small animals. Beyond biomedical applications, time-resolved imaging is exploited for environmental monitoring, LIDAR and characterization of combustion processes.
Structured light illumination and compressive-sensing detection have been recently proposed as new strategies to preserve information content while significantly reducing the number of measurements. One possible implementation of this approach is the Single Pixel Camera (SPC), where the inner product between the image of the subject and appropriate patterns is measured by using a spatial modulator (e.g. DMD, SLM) and focusing the light on a single pixel detector.
In this work, we present a time-resolved imaging system for DOT applications based on structured light illumination and SPC detection, implementing an adaptive scheme based on Singular-Value Decomposition for optimal generation of input/output patterns. Moreover, a novel scheme of time-resolved camera, with ps temporal resolution, is proposed and experimentally validated. The device consists of a high-density matrix of single photon detection elements which can be selectively enabled/disabled. Spatial modulator and detector are combined into a single chip improving cost and compactness. In conclusion, the proposed time-resolved imaging approach can have significant impact on biomedical, environmental and LIDAR applications as an alternative to gated cameras or scanning systems.
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