Introduction

ScanImage 2016 can use photon counting modules instead of standard PMTs. A photon counting head / module consits of a PMT and a subsequent photon counting circuit. This circuit generates a TTL pulse of a defined duration when a photon is detected. ScanImage samples this TTL pulse using the auxiliary digital inputs PFI0-3 of the NI 573x digitizer modules.

Configuration

To configure photon counting for ResScan, add the following entries to the Machine Data File:

%% ResScan
% the features 'Aux Triggering' 'I2C' and 'Photon Counting' are mutually exclusive
I2CEnable = false;
auxTriggersEnable = false;
 
photonCountingEnable = true; % enable photon counting feature
photonCountingDisableAveraging = true; % disable averaging of samples into pixels; instead accumulate samples
photonCountingScaleByPowerOfTwo = 0;   % if photonCountingDisableAveraging == false scale count before averaging to avoid loss of precision by integer division
photonCountingDebounce = 0; % [s] time the TTL input needs to be high before a pulse is registered

The setting photonCountingDebounce can be used to clean up a noisy signal. The delay introduced by photonCountingDebounce can be eliminated by adjusting the value for the scan phase in Configuration Controls.

Limitations