Using RSTI to synchronize IMAQ and motion control

[Peter_UW]

I'm a new student working in my professor's research lab. We are doing OCT (Optical Coherence Tomography). We have the following equipment:

NI Motion PCI-7342

NI-DAQmx PCI-6221

NI-IMAQ 1428

The motion control is hooked up to a couple of mirrors that direct the laser beam. The idea is to start the mirrors moving, then start imaging (for a total of about 1000 images) after the mirrors get to constant velocity, and have all 1000 images done before the mirrors start to deaccelerate again. I tried using the "RSTI with IMAQ (breakpoint-snapshot)" example, but it appears that my system is not sending back position or velocity information. I think this is because the motors are not hooked directly into the NI motion card, instead being hooked into two MicroMax 671 motion controllers, which are then hooked into the motors. So the mirrors move over a breakpoint, but the breakpoint is never triggered. Changing the wiring is not really an option, so I need to synchronize using some other method.

Here is what I am planning to do:

Initialize everything and then have the DAQ card trigger the motion, wait a precise amount of time (calculated to be until the mirrors have stopped accelerating), and then have the DAQ trigger the IMAQ imaging. The imaging would then be on a sequence, taking all 1000 images. Everything would reset after this, and wait for the DAQ to trigger them again (we are doing multiple passes).

Will this work? Can anyone think of a better solution using this equipment?

Thank you very much,

Peter

[VuD]

Hi Peter,

Based on what you are describing, it appears that your solution should work.  If I understand you correctly, you will move the mirrors accordingly, halt motion, and then trigger image acquisition.  Are your devices are all connected via RTSI?  Is there a way for you to route the feedback directly to the NI motion controller as well (i.e. split the wire)?  If not, then the work around you have provided will suffice.   Please let us know if you would like further assistance.

Vu

[billings11]

Peter,

I am an engineer for Cambridge Technology Inc.  We make your 671 micromax cards and galvanometers.  Those 671 cards are actually high bandwidth analog motion control cards.  They are their own motion control, so you don't need to use an NI motion controller.  Actually an NI motion controller (or any off the shelf motion controller) would not be anywhere close to fast enough to drive our galvanometers.  If I am not mistaken NI's 734X line can only go 62.5us.  (I use them here for much larger motion control systems).  You would need PID loop rates faster than about 10us to implement digital motion control on our galvos.  So the purpose of the 671 micromax controller is to do all that high speed servoing for you.

All you need to do to drive the 671's is generate an analog waveform.  Just provide an analog waveform to the input of the 671 card, and the card will servo the motors to closely follow that waveform for you.  We use NI equipment here with labview to do a lot of testing of our motors.  I would recommend any M-Series card with an analog output sample rate faster than 100kHz.  This way you can generate a nice, densely sampled analog waveform to drive our galvos.  We use NI PCI-6251's primarily for testing within CTI.  But the analog outputs of your 6221 will do the trick very nicely.  You can use one analog output for each 671.  You can also use an analog input to acquire the position monitor signal of the 671, so you can see exactly what the actual position waveform looks like.

If you have any more questions about how to set up your application please post on this thread.  Also you can email me at devin@camtech.com.

[kamalm2]

Hello Peter

Can you please shear your VI's for OCT scanning

thanks