kScion Framegrabber Interface

Brief documentation

• You should have a device called /dev/lg3-0 which is enabled by the scionlg3 drivers.
• Start up the program and press Start Capture. If all is well, you will see the image from your camera in the main window.
• Moving the two sliders to the left of the main image window sets the vertical region which is averaged into the intensity plot below.
• There are several controls on the right side:
  • The White Level and Black Level controls change their settings on the LG3 card (read the LG3 documentation for information about this)
  • Clicking the Time Average check box and increasing its value will cause successive frames to be averaged together, which is great for removing noise.
  • Clicking Grab Ground Frame will copy the current visible frame to a buffer, which will be subtracted from the current frame if Subtract Ground is checked.
  • The Invert, Log, and Average controls will change the shape of the intensity plot.
• The Grab Scale button has one of the most powerful features; it automatically computes the scale of the image you are looking at. It does require a few steps to set it up properly, however:
  • Place a ruler horizontally in front of your camera so that the tick marks are clearly visible.
  • Set the upper and lower plot boundaries to cover, for example, only the millimeter marks. Now the profile of the tick marks should be clearly visible in the plot window.
  • Here's the weird part; you need to tell kScion where each tick mark begins by drawing a line through the middle of the plot so that it intersects every oscillation in the middle.
  • Set Plot Average Type to Mid, set the Plot Average Width to approximately the number of pixels between two peaks on the plot, and click Grab Trigger Profile.
  • Now set Plot Average Type back to None and you should see a green line that runs roughly through the center of your plot.
  • Click Grab Scale and the program will compute the average distance between tick marks to determine the scale.
• When you Save Plot from the File menu, you get a text file with two columns; intensity vs x position. The x position is a value from 0 to 1 if you have not used Grab Scale, or in the units of your scale if you have.