Patent ID: 8586287

Claim:
A fabrication method of a cylindrical grating at a circularly cylindrical surface of an element, characterized by the following steps: providing a annular phase mask formed by a plane radial grating; coating said circularly cylindrical surface with a photoresist layer; arranging said circularly cylindrical surface relative to said annular phase mask so that the central axis of this circularly cylindrical surface comprises the center of the annular phase mask, so that said central axis is substantially perpendicular to the plane defined by said annular phase mask, and so that a medium or media between this annular phase mask and the photoresist layer on the circularly cylindrical surface is transparent at least for a given wavelength; exposing said annular phase mask with a light wave at said given wavelength and under substantially normal incidence, said plane radial grating having a period selected so as to have the +1 st and −1 st diffraction orders (Tr +1 and Tr −1 ) propagating in said medium or media between the annular phase mask and the photoresist layer and giving rise to an interferogram in said photoresist layer; developing the photoresist layer resulting in a circularly cylindrical photoresist corrugation grating ( 9 ) having lines parallel to said central axis.