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
Photon Counting Modules that output a TTL pulse for each detected photon are connected to the digital I/O port on the NI573x digitizer module using a NI SCB-19 breakout box.
