If
I wanted to measure the size of a through hole I’d start out by
using a backlighting. Providing I was careful not to saturate the
“hole” area of the image that would work pretty well. If I needed
greater accuracy I might go with a telecentic lens and telecentric or
collimated lighting as that would help me avoid any edge effects. But
what if I wanted to know if the hole was clear?
I’ve
actually encountered this problem. Sometimes in machining chips will
get stuck in a drilled hole. Backlighting will show me the hole but
may not reveal a little curl of metal that could cause a problem when
the part goes in to service.
“Beam
profiling finds use in industrial parts inspection”,
(Laser Focus World, August 13th,
2013,) discusses an interesting example of such a challenge. In this
case the hole was very small and backlighting wasn’t enough to
check that the hole was clear.
The
solution was to look at how much light came through the hole. How?
Well the title of the article gives you a clue, but for more details
you’ll need to click the link.
It’s
an interesting solution, but I can’t help wondering if there’s an
easier way to do this. If you’ve ever dealt with such a problem,
perhaps you could share your solution.
1 comment:
If you have ever used a telecentrically collimated back light with a telecentric lens you would know that detecting small burrs is not a problem. In fact they show up quite well; even if they are very thin.
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