APODISED ZONE PLATE AND NONLINEAR CHIRP SIGNAL

摘要

A zoned radiation device for converging radiation of a wavelength ? to a focus at distance b, the device comprising a first set of zones and a second set of zones, wherein the first set of zones have a different characteristic to the second set and wherein the area of the zones decrease as their distance from a predetermined point increases, and one or more zone distances at which a zone of the first set with a first characteristic switches to a second zone with a second characteristic are configured such that the device can focus the radiation with wavelength ? at a distance b with an autocorrelation/point spread function that is sharper than the autocorrelation/point spread function produced by zones configured to a Fresnel zone construction.