by Scott Prahl
A basic collection of routines to ray trace through graded index (GRIN) lenses with a parabolic radial profile.
Example Light paths in a 0.25 pitch GRIN lens from an ancient Melles Griot Catalog:
import pygrin n = 1.608 gradient = 0.339 length = 5.37 diameter = 1.8 pitch = pygrin.period(gradient, length) ffl = pygrin.FFL(n,pitch,length) efl = pygrin.EFL(n,pitch,length) na = pygrin.NA(n,pitch,length,diameter) angle = pygrin.max_angle(n,pitch,length,diameter) print('expected pitch = 0.29, calculated %.2f' % pitch) print('expected FFL = 0.46 mm, calculated %.2f' % ffl) print('expected NA = 0.46, calculated %.2f' % na) print('expected full accept angle = 55°, calculated %.0f°' % (2*angle*180/np.pi)) print('working distance = %.2f mm'%(efl-ffl))
expected pitch = 0.29, calculated 0.29 expected FFL = 0.46, calculated 0.47 expected NA = 0.46, calculated 0.46 expected full accept angle = 55°, calculated 55° working distance = 1.43 mm
But the real utility of this module is creating plots that show the path of rays through a GRIN lens. For examples, see <https://pygrin.readthedocs.io>
Source code is available at <https://github.com/scottprahl/pygrin> or the module can be installed using pip:
pip install --user pygrin
pygrin is licensed under the terms of the MIT license.