F. Imager Lag
In order to measure the lag, the imager is exposed to a LED
with a constant illumination. the imager exposure time is set
to 50ms and each pixel is read 2 times. Each line readout
takes 20μs. The signal from the second readout of the pixel
comes from the electrons left in the PPD after the charge
transfer in the first readout. The lag is obtained by dividing
the signal from second readout over the one from the first
readout. The lag was measured with different input light levels.
When the PPD accumulates about 2500 photo-electrons the
average measured lag was 0.1%. For an average number of
accumulated electrons around 5000 the obtained lag increases
to about 1%.