Matlab code for control of a resonant scanning microscope

For control of resonant scanning 2P microscopes, my host lab uses a software that I have written in Matlab. Due to some coincidences, the software is based on Scanimage 4.2, a version developed few years ago for an interface with a Thorlabs scope and Thorlabs software (DLLs). I basically threw out the whole Thorlabs software parts, rewrote the core processing code, but kept the program structure and the look-and-feel (see a screenshot below: looks like Scanimage, but it isn’t). For anybody interested, I uploaded the code to Github on my Instrument Control repository. The program’s name is scanimageB, to make clear that it is based on scanimage, but different at the same time.

guiAs hardware, the system is based on an Alazar 9440 DAQ board for 80 MHz acquisition with 2+ channels, where I was inspired by Dario Ringach’s Scanbox blog. Everything apart from acquisition is done using NI DAQ 6321 boards as in the original scanimage 4.2. Those boards are the cheapest X series DAQ boards. Some more details on the design are in this paper.

The software does not aim to be any kind of competitor for scanimage, scanbox, helioscan, sciScan, MScan or others. I do not even want other labto use this software for their microscopes. Instead, I’m hoping that people will find code snippets in the repository that might be useful for their own projects.
The code is not fully self-explanatory, and some core features (data acquisition) are partly dependent on the Alazar source developmental kit (ATS-SDK), which is cheap, but not open software. But if you are interested in a specific microscope control problem, send me a message, so that I can point you to the relevant code snippet which I used to solve this particular problem. Just let me know below in the comments or via eMail —

Here are some of the more interesting sections of the software:

  • MEX/C-code that uses native windows threads in C for parallelization and speeding up processing inside of Matlab. I use it to convert the 80 million data points per second per channel into pictures of arbitrary binning. Most other 2P resonant scanning microscopes do this task on (expensive) FPGAs.
  • In one of the main m-files, search for scanphaseAdjust(obj). This is an algorithm that I’m using for automated scan phase adjustment for bidirectional scanning. The implementation is not designed for speed, but it features sub-pixel precision alignment by very simple means.
  • In another big Matlab file which I repurposed from something written by Thorlabs, you can find how I implemented the integration of the Alazar 9440 DAQ board into Matlab using Alazar’s SDK, e.g. in the function PRinitializeAlazar(obj). When I started, I did not find any Matlab code online for controling this board, so this might serve as a starting point for other people as well.
  • If you want to use retriggerable tasks for X-Series NI DAQ boards, you can search for the key words Task( and retriggerable in this code. Retriggerable tasks are important to understand if you want to synchronize devices on a sub-microsecond timescale using NI DAQ boards. This code snippets will give you a good idea how this can be done using the open DABS library (a Matlab instrument control library written by the Scanimage programmers). It works basically as in Labview, but the code can be understood more easily afterwards and by others.

Precise synchronization and reliable fast triggering is – in my opinion – the most challenging part of writing a control software for resonant scanning microscopes. Non-resonant galvo-based microscopes work with frame rates of typically

To this end, I’m using the internal memory of the programmable X series NI DAQ boards to overcome these fast timescales (thereby following Scanimage 4.2 and 5.0). But the complex interdependence of triggers for laser pulses, lines, frames, laser shutters and pockels cells, together with the synchronization of external hardware makes things complicated and difficult to debug. If you are facing similar challenges of implementing complex triggering tasks, I would be glad to point you to sample code or give you some hopefully helpful advice —

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