Photon counting electronics and method that allow for counting single
photons with sensitivity, linearity, and accuracy. The method for
accurately counting photon numbers entering a photon multiplier tube
comprising the steps of counting the number of the electrical pulses
generated by photons; measuring the duration of the electrical pulses
with a timing clock, wherein the timing clock can count the number of
temporally overlapped photons; measuring the intensity of the electrical
pulses with an intensity discriminator, wherein the intensity
discriminator can count the number of intensity-overlapped photons; and
summing the number of the electrical pulses, the number of temporally
overlapped photon, and the number of intensity-overlapped photons, that
is equal to the total number of photons.