Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Matlab Image Acquisition Problem

  1. May 28, 2008 #1
    I'm working on a laser microscopy setup and am having issues with Matlab image acquisition. I'm using an AVT Pike-032B CCD camera that is a 1394 camera. Most importantly, I'm interfacing to it using the CMU 'dcam' library, which provides pretty nice control through a program "1394 Camera Demo".

    The camera does indeed work in Matlab, using the following lines to initialize and capture:
    > vidobj=videoinput('dcam',1);
    > snapshot=getsnapshot(vidobj);
    > imagesc(snapshot);

    However, I am not able to find a command or parameter that specifically sets the exposure time for the frame capture or shutter speed. It seems as if one of the properties of the triggering should be able to do this.

    Does anyone know if it's possible, and if so how, to trigger a camera through the dcam driver for a specific exposure?

    The Motivation: I've got 2 lasers at different intensities that are coupled into my microscopy system. My plan is to automate the system such that one laser turns on, two images are acquired, and then the other laser turns on (the first turns off), and two more images are snapped. rinse, rinse, repeat. Unfortunately, the laser sources are different enough power levels that with the auto-shutter on (as it seems to be right now), it takes a couple captures for the exposure level to set properly. I need to be able to specify an exposure time that will look good on the first capture for each laser.

  2. jcsd
  3. May 29, 2008 #2
    I've found the answer to my question. In case anyone else has similar issues:

    You've got to get to the Device Specific Parameters. This is accessed by 1) creating a videoinput object; 2) creating a source object attached to the video input; and 3) asking nicely :p. See below:


    ** this returns something like:
    General Settings:
    Parent = [1x1 videoinput]
    Selected = on
    SourceName = input1
    Tag =
    Type = videosource

    Device Specific Properties:
    AutoExposure = 125
    Brightness = 16
    Gain = 0
    GainAbsolute = 0
    GainControl = relative
    GainMode = auto
    Gamma = 0
    NormalizedBytesPerPacket = 256
    Shutter = 2289
    ShutterMode = manual

    At this point, simply use:


    le fin
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Matlab Image Acquisition Problem