Hello Mike,
Just so you know, I'm an NI employee, so my response is subject to some inherent bias.
There are basically two modes within PatFind (aka FindPatterns): Area Model and Edge Model. The Area Model uses standard cross-correlation and relies on grayscale values to find matches in an image while the Edge Model uses edges, outlines and shapes to find matches. This is very similar to the two matching algorithms from NI: Pattern Matching and Geometric Matching. For most applications, Pattern Matching is often preferred because it is faster and more straightforward to configure. However Geometric Matching is very usefull for applications that have:
*Inconsistent lighting
*Objects that change size
*Occlusion or overlapping parts, and
*Perspective or nonlinear distortion
From my experience, the accuracy and reliability of the tools from NI and Cognex are quite similar, but you'll have to compare them side-by-side to determine which one is best for your application in terms of speed and ease-of-use. I recommend downloading and installing the 30 day evaluation of the NI Vision Development Module, which contains all the machine vision functions for LabVIEW and Visual Studio. It also includes an application called NI Vision Assistant which provides a nice way to prototype vision applications and test "what-if" conditions. From within Vision Assistant, either acquire an image from a camera or open an image from file. Then you can explore both the Pattern Matching and Geometric Matching algorithms from NI. (Be sure to use the Performance Meter to judge how many parts per second you can inspect with the tools.) Finally, once you've developed your inspection, Vision Assistant will automatically generate the LabVIEW, C or Visual Basic code for you.
With that said, if you have some images of what you are trying to inspect, I'd love to help you prototype the application.
Finally, I should mention that Cognex also has an algorithm called PatMax for off-the-wall applications, like finding patterns on crumpled pieces of paper and locating fiducials when the lights go out. I've never used it, but I've heard it can be expensive and is overkill for most vision applicaions. Even on their website, Cognex recommends customers start with PatFind.
Kyle V
