Fresnel Diffraction at a Pinhole

This sequence of pictures shows the pattern on a distant screen as light diverging from a single-mode fiber passes through a 100 micron dia. pinhole from various distances, that increase in steps of 5 mils, or 127 microns. (The step size for the final few pictures is double this.) In the first picture the fiber is so close that the light doesn't see the pinhole. Far away the light reaching the pinhole looks like a plane wave, so one just sees a small Airy disk. (The usual rings are there as well, but are too faint to see on the image.) Click on an image to see the full-size version. Click here to cycle through each picture and view its fiber-aperture distance. Click here to return to the main page.




Diffraction patterns calculated in Mathematica for fiber-aperture distances of 0.01, 0.5, 1.0, 1.7, 5.0 and 20.0 mm (left to right, top to bottom).