Specifications

Table Of Contents
Version 1.1 rev Jan 2013
Page 84
iXon Ultra
, Features and Functionality
To successfully photon count with EMCCDs, there has to be a signicantly higher probability of seeing a ‘photon spike’
than of seeing a dark current / CIC ‘noise spike’. The lower the contribution of this ‘spurious’ noise source to a single
exposure within the accumulated series, the lower the detection limit of photon counting and the cleaner the overall
image will be, as demonstrated in Figure 37 below:
Figure 37: ‘Photon Counting’ vs. ‘Standard EM-on’ Imaging for very weak signals.
Images A, B and C were recorded under identical illumination conditions, identical exposure times and each with EM
Gain set at x1,000. The benet of photon counting under conditions of low clock induced charge (CIC) is evident.
Images D and E are derived from a larger number of accumulated images, in order to yield a greater measurable Signal
to Noise ratio. An identically positioned Region of Interest on each image was used to determine S/N of 3.86 and 6.02
for standard and photon counted images respectively. This factor improvement is in accordance with the theory of
Photon Counting circumventing the inuence of multiplicative noise (noise factor) in EMCCD signals.