Figure 2
Histogram for photon number thresholds. (a) Spatial histogram taken for the region of interest used with the sensor illuminated by a LED source over 100,000 frames. The dashed lines indicate regions where the events with ADU signal outputs between the dashed red lines may be labelled as one-photon events and ADU signal outputs between the green dashed lines may be labelled as two-photon events. The peak preceding to the red dashed line represents pixels for which zero-photon events are detected and is present due to an offset and a non-zero readout noise. Further peaks beyond the green dashed line are present representing > two-photon events. (b) A selection of histograms for individual pixels from the above dataset. Histograms generated using frames obtained under a level of illumination greater than that under which the imaging data was obtained.
