Thursday, May 10, 2012

Throw away your darkfield lights

Back in Vision School I was taught that the way to find dents in metal was darkfield lighting. Light directed along the surface the metal will reflect up from edges, creating bright lines in a dark image. Unfortunately, one of the weaknesses of this lighting strategy is that it’s seldom possible to quantify the size of a dent. (A second problem is that the edge intensity is a function of surface or dent geometry.)

But there is now a better way: 3D.

3D camera systems produce z-axis data, making it possible to quantify the area and depth of indentations. Several companies make 3D imaging systems, but one of the easiest to use, in my humble opinion, is the IVC-3D smart camera from SICK.

If you’re interested in learning more, I suggest you visit the website of integrator Cimtec. On a page titled “Sick IVC 3D Demo setup” they have links to a couple of movies showing the system in operation. The movies are pretty high quality and give a good overview of what the system can do.

Surprisingly though, Cimtec overlook the weaknesses of the IVC-3D. (I can’t think why they would do that!) In a nutshell, these are speed and resolution. Much as I like the product, it’s not a universal solution. In other words, evaluate your application, or have someone who knows the IVC-3D do an evaluation, and find out if it might work for you.

And if not, there are lots of other 3D inspection options out there.

1 comment:

Anonymous said...

Shiny surfaces are problem for laser triangulation method. And z-resolution isn't good enough to find scratches etc. Also I'm not fan of the user interface for programming, but that's easily fixed :)