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analog signal to matrix?
AnthonyM
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05-18-2005 05:39 PM
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I am on a Windows XP system with Labview 7.1 I will be making analog data from a PMT and using it to create an image. I will be doing this by Raster scanning a laser across my sample. How would I go about taking the analog data and putting it into matrix of say 256 samples across and 256 lines down? Also how would I then view this matrix as a topographic or intensity map? Ideally I would like to average about 10 data points per pixel and have a pause between pixels. I know this is large flowing please help me post, but I am lost. Sorry for the long post and thanks in advance for any feedback.
Anthony
Anthony
AnalogKid2Digit
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05-18-2005 05:53 PM
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I did a similar task using a diode laser, scanning polygon with F-Theta correction optics, collection optics, photodiode, transimpedance amp, SOS/EOS signals, and a Matrox frame grabber. Pretty cool to get 1000 to 10,000 pixels per line. Never used LabView for it, acquired 1st light within 2 months of picking up a soldering iron. For a picture of the prototype, see
http://lincolnlaser.com/products/opticsmodules.cfm
For a Labview approach, it may be handy to have SOS (start of scan) and EOS (end of scan) signals to start and stop the analog acquistion. You would need to set your sample rate accordingly to give you the proper number of data to average per scan line so that you end up with 256 'pixels' Did not understand pause between pixels, maybe you could oversample and then decimate the data?Then acquire 256 of the above 'lines' This should give you a data format (X, Y, and intensity) to display in an intensity chart.
You could possibly use a framegrabber like I did, would have preferred a National one, but they did not support custom camera formats like I needed.
http://lincolnlaser.com/products/opticsmodules.cfm
For a Labview approach, it may be handy to have SOS (start of scan) and EOS (end of scan) signals to start and stop the analog acquistion. You would need to set your sample rate accordingly to give you the proper number of data to average per scan line so that you end up with 256 'pixels' Did not understand pause between pixels, maybe you could oversample and then decimate the data?Then acquire 256 of the above 'lines' This should give you a data format (X, Y, and intensity) to display in an intensity chart.
You could possibly use a framegrabber like I did, would have preferred a National one, but they did not support custom camera formats like I needed.
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"It’s the questions that drive us.”
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"It’s the questions that drive us.”
~~~~~~~~~~~~~~~~~~~~~~~~~~
05-18-2005 06:10 PM
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I need time for my mirror to steer to the next point. I roughly calculate this to take microseconds. I am having a hard time just getting the data to be taken at microsecond intervals...
AnalogKid2Digit
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05-18-2005 06:14 PM
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What DAQ hardware are you using? That will determine your max sample rate. You may want to oversample (ie Nyquist) to obtain good signal fidelity. Have you also looked at the response time of the PMT? If it is too slow, you will not achieve your goal regardless of the sample rate.
~~~~~~~~~~~~~~~~~~~~~~~~~~
"It’s the questions that drive us.”
~~~~~~~~~~~~~~~~~~~~~~~~~~
"It’s the questions that drive us.”
~~~~~~~~~~~~~~~~~~~~~~~~~~
05-18-2005 10:57 PM
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I am on a board that can sample at 200kS/s and can write at 10kS/s so I think there I should be fine, I haven't looked too much into the PMT characteristics but that is a good idea, basically I am not sure how to even start the process.
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