Patent ID: 9632039
Date: 2017-04-25
CPC Classifications: G01B,G01N,G03F,G03H

Claim:
1. An inspection apparatus for measuring properties of a target structure, the apparatus comprising: a radiation source; and an image detector in combination with an optical system, the optical system defining the following beam paths: wherein the reference radiation is coherent with the scattered radiation so as to interfere with the scattered radiation and form an interference pattern at the image detector, wherein the image detector is configured to capture one or more images of said interference pattern, and a processor arranged (i) to receive image data representing said one or more captured images, (ii) to calculate from the image data and from knowledge of the reference radiation a complex field of the scattered radiation at the detector, (iii) to calculate from the complex field a synthetic radiometric image of radiation diffracted by a periodic structure within the target area.