Using time-correlated single-photon counting technique on SPAD sensors to enhance acquisition time and dynamic range

In modern single pixel microscopy techniques, like Nano-Illumination Microscopy, long measurement times can become a major issue, especially when imaging biological tissues with large field of view. Usually, light intensity measurements are performed with CMOS pixel cameras, with typical integration times around tens of milliseconds. In this work, we propose to obtain light intensity data indirectly by applying statistical techniques to the photon arrival times measured with a SPAD photodetector. We will present how the different statistical measurements can be used to minimize the total acquisition time and minimize also the hardware required. In this work, with only 256 Single Photon Avalanche Diode (SPAD) measurements, the exposure time is reduced from 50 ms to 140 us. The dynamic range is extended by combining statistical techniques with standard intensity measurements. Standard intensity acquisitions are used to obtain low light intensity data, and, when the SPAD sensor is in saturation range, the time information obtained by the distribution of the photons allows to determine light intensity. This paves the way to practical Nano-Illumination Microscopy and other single pixel microscopy techniques.