Patent ID: 9719859
Date: 2017-08-01
CPC Classifications: G01B,G01J,G01N,G03F

Claim:
1. An interferometer comprising: an illumination source for generating an illumination beam, an illumination system for projecting the illumination beam emitted from the illumination source onto a sample so as to illuminate two areas of the sample where the two areas are laterally shifted from each other by a given distance, a detector for receiving radiation beams reflected by the two areas of the sample, and an imaging system for directing the radiation beams reflected by the two areas of the sample onto the detector, wherein said illumination system includes a first diffraction grating for diffracting the illumination beam emitted from the illumination source to produce first and second diffraction beams, wherein said two areas of the sample are illuminated by the first and second diffraction beams, respectively, and wherein said imaging system includes a second diffraction grating for diffracting the first and second diffraction beams reflected by the sample to produce a third and a fourth diffraction beams which are laterally shifted from each other, and wherein an interference image consisting of the third and fourth diffraction beams is formed on the detector, wherein said first and second diffraction gratings each comprise a phase diffraction grating for producing at least two higher order diffraction beams higher than zero-th beam, wherein said phase grating includes a grating pattern defined by two spatial frequency components, and wherein said grating pattern is defined by logical sum of the two spatial frequency components.