How to photograph a profile?

[patta]

At work, check how 3D printed screw threads comes out, what starting geometry and printing parameters give the best fit. In this case, should be an ISO thread with 0.75mm pitch, the one we use most!
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[Chris S.]

Patta,

Thanks for sharing your clever profiling rig! Your use of the old film camera, as a lens-holder and light diffuser, makes me smile—though of course this is far less important than your implementation of telecentric optics on both lighting and image-taking stages.

I also like your demonstration of the profiler’s usefulness in adjusting 3D printed threads. It's easy to see how adjusting the print based on observed example lets one make better threads.

See also the 10 yrs old post about M26 threads, with well-made diffuse illumination and higher magnification and NA
Nikon and Mitutoyo objectives have different M26 threads

I was the fellow who made those M26 thread images, more than ten years ago. As you say, I had the advantage of using a high-NA objective (with its correspondingly thin depth of field). For the diffuse illumination, IIRC, I just bounced light off of paper or white foam core, placed a couple of inches behind the threads. I recall being pleasantly surprised how well the high NA worked for showing the thread profiles.

Your profiling rig, I think, is more versatile. But perhaps anyone with a macro rig that can handle reasonably high NA objectives and diffuse light coming from behind the subject, can do well enough for some useful work.

Cheers!

--Chris S.