I too am in search of an inspection system which has the capability of detecting .0005 scratches on a shiny metal surface. The problem is compounded in that the surface is a soft aluminum alloy which can be scratched very easily. This makes the ideal system one that does not come in contact with the surface. The system would be required to be remote and perform the job in East Tennessee.Does anyone have any ideas or contact info for such an inspection system? The subject parts are 20" wide x 72" long.

 

http://www.cognex.com, the best system I have used.

 

Try an array of laser diodes.
Uncolumnated, no focus lens.
Bounce the light off the surface to be inspected.
Any small scratches should appear as black lines due to wave cancelation. Probably any vusion system can be used as a detector.
I proposed such a system for motion picture film inspection.

 

I suggest using a portable profilometer which uses a diamond stylus .000080 radius to trace the scratch and print a graphic strip chart showing depth and width of scratch.