Yes, I do have an idea of where the focus is because I already plotted a curve of the focal length response to current just by using an IR card (by hand) to find the focal point.
Any suggestions to improve my method?
I think I may have it: measuring in two spots fairly close together so as not to bypass the focal point would allow me to determine theta, the divergence, and if I know the beam width at the lens, then I can use f=d/theta to find the focal length! Does this sound plausible?
Yes, I can. Ok, so the focal point would be closer to the second position than the first, but based on that information you still couldn't say whether it was between the two positions or past the second.
UltrafastPED: I do already know how to use the BPC with the laser beam alone.
Simon: without a BPC, measuring the focal length would consist of using an IR card to see where the beam is most focused. The BPC tells me the dimensions of the beam and its intensity throughout the profile, so the...
I really don't know; it has something to do with the Gaussian intensity function. As in I take 2 images and somehow that parameterizes the equation and I can solve for focal length, I guess? I'm not sure. Grad students in my lab know it is possible but aren't sure how either, so of course the...
Hello all,
My lab recently purchased a deformable lens, which can change its focal length from 140 mm to 40 mm and anywhere in between, based on current applied to it.
I'm wondering how to use a beam profiling camera to measure the focal length of this lens at various current levels. We...