Patent ID: 9141004
Filing Date: 2015-09-22
Classification: G03F

Abstract:
1. A lithographic apparatus comprising: a deformation sensor configured to determine a deformation of an object of the lithographic apparatus, wherein the deformation sensor comprises at least one optical fiber arranged on or in the object, the optical fiber comprising at least one Bragg grating, and an interrogation system configured to interrogate the at least one Bragg grating, wherein the interrogation system is configured to analyze a light beam comprising one or more signals each with its own wavelength, and comprises: an entrance selector configured to receive and pass at least part of said light beam; a first diffractor arranged to receive at least part of said beam and to diffract in a first direction each of said signals at an angle dependent on said wavelength in a first plane of diffraction; and a second diffractor arranged to receive the diffracted signals and to diffract in a second direction each of said signals at an angle dependent on said wavelength in a second plane of diffraction, wherein said first plane of diffraction and second plane of diffraction are non-parallel to each other, a detector comprising a plurality of detector elements arranged to receive the diffracted signals of the second diffractor and to generate one or more detector output signals in dependence on the diffracted signals, and a processor connected to said detector to receive said detector output signals and determining the wavelength of each of said signals.