Notes on finding the Apex Angle of an Axicon
For the handheld laser wire stripper project, I needed to find the Apex Angle of the axicon so I could place an order. As it turns out, different suppliers specify the Apex Angle differently, so it can be a bit confusing on how to order axicons.
For Thorlabs, if S1 is the apex side, let S2 be the reference–put the baseline of the protractor on this plane. Position the origin of the protractor at the top of the optic, and measure the slope of S1. Here’s a partial screenshot of the Thorlabs drawing:
Here’s my measurement, using the very handy on-screen protractor found here: http://osprotractor.sourceforge.net/Protractor.html :
For EKSMA, the angle lines are referenced to each other; draw two lines that extend the apex on the top and bottom, then measure the angle between them. Here’s a partial screenshot of the EKSMA drawing:
Here’s my measurement:
So, we see that the apex angle is measured differently. Still, the two angles complement each other, so if thou has one angle, perhaps from the EKSMA method, then thou shall also have the other, Thorlabs, angle (old English speak thanks to Grammarly).