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Weird spectrum obtained when programming Andor EMCCD

Hi all, I am using Labview to communicate with Andor's EMCCD. I use Andor SDK as the basic frame, and also control a 2D scanning mirror. Basically, the CCD takes one spectrum when the mirrors steer the light one step. CCD has USB driver; scanning is controlled via analog output of a DAQ board.

 

However, the spectrum between 700 to 1024 pixels is always truncated. (See image1) It does not happen when I use the SDK (image2).

 

I was wondering why this would happen, since I just add something but do not change the basic code.  I would appreciate your help, thanks!

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Message 1 of 13
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I did not quite understand the setup, but are you sure this is not a settings problem? The a/d converter in these cameras are 16-bit and saturate at 65535 counts so you may just be seeing the lower intensity features across your full scale while the intense peaks are saturated. Possible settings include: EM Gain, gain in the digitizer, integration time, using em channel and conventional analog channel, different ROIs, etc.

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Thanks for your reply very much. It would probably not be a setting problem. I tried various samples, also varied the exposure time, the spectrum was still truncated. It was not totally flat though, the characteristic peaks disappeared.

A stupid solution I found is to run the original SDK and my code simultaneously, and then close the original one. After that my code performs well. It seems like the original SDK serves as a bbq lighter...

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Message 3 of 13
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Can you show spectra taken with the two methods that are not at saturation (i.e. any counts over 65535)?

 

Thanks

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Just to clarify:

 

Case 1) you are using Andor's prebuilt LabVIEW SDK for development.

Case 2) you are talking directly to their low level driver.

 

Is this the setup? I use primarily Princeton Instrument's stuff, where they have a low level driver that is well documented for development with and a LabVIEW SDK built on top of that driver. I am not sure if the Andor situation is the same.

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Hi, here they are. Image 1 is using my code.

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Message 6 of 13
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I am using LabVIEW SDK. Each icon is a sub vi, and it calls functions in a dll from C. I have not learnt how to use the low level driver yet.

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Can you please clarify what is the difference in the LabVIEW and the hardware setup between case 1 and 2?

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Message 8 of 13
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Thanks, but I don't quite understand your question. For the prebuilt SDK they wrote nice subVis to call the functions in C via dll. I do not have the permission to write to the containing LLB. So I just drag those modules in my code, and run each module in a sequence.

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Message 9 of 13
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Back to your original question, I am still unsure what you are doing different in the two experiments. When you say prebuilt SDK, do you mean that they have some example LabVIEW code that you are using to take a spectrum and in the other case, you are using their SDK in your own application?

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