Patent ID: 7715100

Claim:
A method of generating a polarized light beam to be projected onto an object plane ( 46 ) comprising the steps of: generating a converging or diverging light beam ( 18 ); projecting the converging or diverging light beam through a member ( 22 , 52 ) comprising a uniaxial birefringent material, the uniaxial birefringent material having a symmetry axis essentially parallel to the optical axis ( 12 ) of the light beam, and the member being placed at a distance from the object plane, wherein light that traveled through the uniaxial birefringent material comprises an extraordinary mode ( 24 ) and an ordinary mode ( 26 ), the modes having different focal points ( 28 , 30 ), characterized in that a spatial filter ( 32 , 38 ) is provided for substantially blocking one of these modes.