If using a line camera, a line light on either side works great. For area scan cameras, you need to uniformly light the area with diffuse light. For a small area, you can use something like the CDI (cloudy day illuminator). For a large area, you could make your own dome like surface and point some lights into it. For one project I did many years ago, we built a square pyramid shaped dome, painted it white, and put a linear bar along each edge pointing up at the dome. It wasn't perfect, but it did the job. The important thing is to point your light at a large white surface, and let the reflection of that light illuminate the part. You might be able to do it by putting some fluorescent lights behind a large diffuser panel.
Bruce
Bruce Ammons
Ammons Engineering
