With NI-IMAQ (now up to version 2.6) you are able to acquire, display, and save images. With IMAQ Vision, you'll be able to very accurately measure the thickness of the needle. If you attach an image to this post, I should be able to tell you just how accurate IMAQ Vison can be. You can find out more about IMAQ Vision (which is a component of the Vision Development Module for LabVIEW) here, http://sine.ni.com/apps/we/nioc.vp?cid=2881〈=US
The other route (aka, the free one) is to convert the image into a 2D array of pixel values. From this array, you may be able to measure the thickness of the needed by writing your own algorithm. It most likely won't be as precise as the IMAQ Vision tools (which give you real world measurements down to the 0.1 pixels).
The Vision Development Module will work with LabVIEW 6i, so there is no requirement to upgrade to LabVIEW 7 Express. But in case you're curious, the new LabVIEW is really something. www.ni.com/labview is the place for more info.
Kyle V.
