I am developing an inspection station. I am using cameras to check some hole diameters and part features on a low speed conveyor line. I do need to inspect the diameter of a blind hole and cannot get the correct lighting for the camera to measure it. Can someone point me toward some other techniques that I might try to measure this diameter? I'm shooting to inspect between 20 and 40 parts/minute.

 

Try a ring light or low angle lighting and histogram in two directions after a threshold as a percentage of the average. Use the larger. A light area can bloom, but a black area won't. Polarizers can work too. You may need to use a very limited depth of field (small f stop) or a telecentric lens for high accuracy. Grab a frame and mail it and I could probably be more helpful. Your histograms should show you exactly what needs to be done.

Regards

cww

 

what material are you inspecting? you could angle the work and measure the width. or if the hole is in the same place, how about a retro reflective sensor adjusted to detect only the surface - or the bottom of the hole! the measure using the conveyor. for higher accuracy, what about laser sensors? for lower accuracy, how about a microswitch

marc sinclair

 

Maybe you could try a line light across the diameter. Angle the camera or the light off square so the line is broken in the image. There are inexpensive laser diodes available with line collimators.

Vince