|A||Wait for trigger||Starts image acquisition on TTL Trigger|
|B||Send Trigger Output Type||Choose between Frame Clock, continuous pulses, single pulses or no trigger.|
|C, C1||Pulse Duration||Duration for TTL signal to be set to High, always set in milliseconds.|
|D, D1||Initial Delay||Delay from start of acquisition to rising edge of first pulse, specified in milliseconds or in number of frames.|
|E, E2||Pulse frequency |
|Frequency of pulse train in continuous pulse mode, specified in either Hz or number of frames.|
|F||Frames/ms(Hz) switch||Choose between setting trigger output parameters in numbers of frames or in milliseconds and Hz|
Triggering SciScan from an external device
The WAIT FOR TRIGGER from external device option on the Trigger tab (A in the diagram above) allows users to initiate an acquisition with a TTL trigger. Whenever the box WAIT FOR TRIGGER from external device is ticked the system will wait for a TTL signal (rising edge) on the external.start.trigger.channel before executing the RECORD (or Focus) function. Please consult Knowledge Base articles on wiring your DAQ for setting up the input channel.
As default the external start trigger is Dev1/PFI3. If you would like to use an analogue signal to trigger the image acquisition simply wire PFI3 to one of the user ports on the spring-block terminal. The external.start.trigger.channel can be specified in the DAQ Settings section of the .ini file.
Once you are satisfied that the trigger is wired properly and the tick box is selected, press the RECORD button. Pressing RECORD will prep the system for imaging and launch a popup to indicate that the system is waiting for a trigger. If a TTL pulse triggers the acquisition, a frame scan as specified in the 2D Frame scan tab will start immediately. You can press Cancel in the popup to return to normal operation if the trigger does not arrive.
Please note: Triggered acquisitions can also be set up within SciScript (if the box is ticked when configuring your scan), allowing you to configure sequential triggered acquisitions.
Triggering from SciScan
In addition to being able to be triggered from an external device, SciScan can also output triggers to external devices or provide timing signals for synchronisation with other equipment in a few different formats.
- Sample Clock – Available on PFI7, this channel will output a pulse with each acquired sample. The rate of this signal depends on the rate of the acquisition card being used (eg. 5 MHz on a PCI-6110).
- Internal start trigger – SciScan passes a single start trigger pulse between PFI2 and PFI6 to start an acquisition. This signal can be split off and be used as a precise marker of when the acquisition started.
Please Note: the internal start trigger is about 50ns wide and cannot be modified, this many not trigger all types of equipment.. If the start trigger cannot trigger your equipment reliably, please use the frame pulser signal where necessary
Selectable and Customisable Triggers
The trigger tab now provides you with four options for customisable triggers, as default these triggers will appear on PFI13 unless otherwise stated. Select the type of trigger to output from the dropdown box marked B in the image above. Pulse parameters can be set either in milliseconds or in the number of frames by flipping a switch (F).
- Legacy frame pulser – this was available in previous versions of SciScan and was always active by default. In order to maintain backwards compatibility this frame pulser is still available, but it must now be selected from the dropdown menu. This will output a Frame Clock signal on The Frame Clock output is derived from the frame rate that you are scanning with and operates with a 50% duty cycle with the rising edge corresponding to the first pixel acquired in a given frame.
- Continuous Pulses – available on PFI13, the continuous pulse mechanism allows you to specify the parameters of a continuous pulse train which will output during image acquisition. Pulse parameters are adjusted using the controls on the tab and outlined in the table above.
- Single Pulse – available on PFI13, the single pulse option allows you to specify a single pulse to be output after a user-specified delay (D,D1) and for a user-specified duration (C,C1)
- Trigger off – no trigger used
Please note: a warning will appear if desired pulse parameters are out of range.
SciScan 1.4 only
Line Clock Trigger Feature (Galvos Only)
This feature is implemented in the trigger option for our galvo scanners. It works for acquisitions with fill fractions below 100% and can be used for both bidirectional and unidirectional scans. By default, the acquisition is triggered during high clock trigger input. However, an inversed version of this function is also available and can be found in the trigger tab as ‘Inverted Line Clk (PFI 12)’.
An example: A projection stimulation used during the fly back of the galvo mirrors during which the image is not being recorded, therefore the projector light is not affecting the data acquisition.
Below, an oscilloscope traces show the feature for galvo scans of 80% fill fraction for both bidirectional and unidirectional scans in their normal and inverted forms (Blue – Line Clock Trigger, Yellow – Galvo Mirror Command).