We propose a technique to manufacture Fresnel lenses where the grooves are phase-synchronized at a given wavelength. This means that the light from different grooves will superpose coherently at the focal point at the specified wavelength. The focusing performance of such a “tuned” Fresnel lens will be better than that of ordinary Fresnel lenses by orders of magnitude and can, in principle, equal the performance of a conventional lens of the same diameter (diffraction limit). In optical communication systems, which use mostly narrowband light sources (lasers, LEDs), tuned Fresnel lenses may offer a lower cost alternative to conventional lenses without sacrificing focusing performance.
© 1986 Optical Society of America
Giovanni Vannucci, "A “tuned” Fresnel lens," Appl. Opt. 25, 2831-2834 (1986)