Talbot effect and Cornu's spiral.

Cornu's spiral is used in the testing and extension of a recent explanation of the Talbot effect, which occurs in the Fresnel domain. The results confirm all parts tested. They also indicate that each band of a Talbot plane is controlled primarily by light from only a few slits of the grating, contrary to earlier assumptions. Increases in slit width are found to limit the number of Talbot planes that can be observed.