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Thread: Delayed capturing after hardware trigger

  1. #1
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    Sep 2017
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    Delayed capturing after hardware trigger

    Hello

    We use lots of imaging source cameras (DMK23G274 for example), and we have a problem in almost all of them. Sometimes when I send a hardware trigger, the camera doesn't start capturing right away. According to the datasheet, after the trigger it takes 4.8 microseconds (at most) to start the exposure but the image is taken more than 200 milliseconds after the trigger (I found that by looking at the scene in the image). I set the exposure on 1 milliseconds and the image is good but it's taken many milliseconds after the trigger. What is the problem?!

    Thanks.

  2. #2
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    Re: Delayed capturing after hardware trigger

    Hello

    In case you use a clean trigger signal, the camera starts to expose and send an image in regularly without waiting.

    Which frame rate do you use?
    Do you trigger in regular intervals?
    Best regards
    Stefan
    IC Imaging Control Support

  3. #3
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    Re: Delayed capturing after hardware trigger

    Thank you for your response

    I work with windows and c++. I send a command by serial port to a PIC microcontroller and that send the trigger to the camera. I do some processes for each frame and when the process finishes I send a new trigger so my intervals are not exactly equal. Usually the trigger is sent every 60 to 80 milliseconds so the fps is less than 13.

  4. #4
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    Re: Delayed capturing after hardware trigger

    Well, that means, you do not know exactly, when the micro controller gets the command and sends the trigger.
    Do you have an LED or something else in you scene, that does something on the trigger, so you can see that in the image and get a good timing relation?

    Also it may happen, you have a frame dropped, because the computer does not handle all image data packages, so a frame is dropped. This can be reduced by using lower frame rates.
    Best regards
    Stefan
    IC Imaging Control Support

  5. #5
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    Re: Delayed capturing after hardware trigger

    Hi again

    Yes I don't know the exact time of the trigger but it is limited into a few milliseconds not such long time. It also can not be a frame drop because if a frame drops, we have not any image to discuss and if we don't have image, I don't do trigger again so I will not have a wrong image.

    Thanks.

  6. #6
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    Re: Delayed capturing after hardware trigger

    I wonder, whether you have a frame drop. And therefore you do not get an image after triggering.

    On most trigger pulses you get an image?
    Best regards
    Stefan
    IC Imaging Control Support

  7. #7
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    Sep 2017
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    Re: Delayed capturing after hardware trigger

    Hi again

    Let me explain more, I send a trigger for an image, when the image comes, I do some processes, when its done, I send another trigger. If the process finishes so soon, I wait a few millisecond according to maximum FPS, then I send the trigger. Between this procedure, sometimes I send a trigger and start waiting for the image, but the image will be captured so late, It isn't dropped, It comes to me but late. I don't send another trigger until I get the last image.

    thanks.

  8. #8
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    Re: Delayed capturing after hardware trigger

    And you are sure, the camera waits? For handling the trigger? As far as I know, it is technically not possible, and I never saw that issue. You are also sure, the sending of the trigger pulse is not delayed by the computer ?
    Best regards
    Stefan
    IC Imaging Control Support

  9. #9
    Join Date
    Sep 2017
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    Re: Delayed capturing after hardware trigger

    Of course I'm not sure. It's not the computer because micro controller sends the trigger directly to the camera (It just gets the permission from the computer) and I get the capturing time, directly from micro controller. I checked everything and it seems that there is an evil ghost in camera . Anyway thank you for your cooperation. I let you know If I find the real problem.

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