Patent ID: 7515349

Claim:
Optical apparatus for modifying a radiation beam, said apparatus including: a) a variable focus lens ( 1 ) comprising a first fluid (A) having a first refractive index and a second fluid (B) having a second, different, refractive index, wherein said fluids are immiscible and are separated from each other by a fluid meniscus ( 6 ; 106 ; 206 ; 306 ) which is configurable into a configuration which is arranged to modify a predetermined vergence of an input radiation beam ( 15 ; 32 ; 33 ), whereby said configuration determines a focal power of said lens; and b) a focus control system ( 8 ; 108 ; 208 ; 308 ) arranged to control said focal power by variation of the configuration of said fluid meniscus, characterised in that the optical apparatus comprises a first redirector arranged to redirect said radiation beam, after having passed once through said fluid meniscus, back towards said fluid meniscus, and a second redirector arranged to further redirect said radiation beam, after having passed twice through said meniscus, back towards said fluid meniscus, wherein said configuration is arranged to further modify the vergence of said radiation beam following each of said redirections, said further modifications being arranged to provide said variable focus lens with an amplified focal power.