Zoom optical system

Abstract

A zoom optical system is provided which has a lens system which comprises a first lens which is arranged to provide a continuously variable focus for a beam of radiation. The lens system further comprises a switchable optical element including a first fluid, a second fluid and a wavefront modifier having a part through which said radiation beam is arranged to pass. In a first mode the switchable optical element has a first fluid configuration with said part being substantially covered by the first fluid, and in a second mode the switchable optical element has a second, different, fluid configuration with said part being substantially covered by the second fluid.

1 . A zoom optical system comprising a lens system which is arranged to provide a variable zoom setting for a beam of radiation, wherein the lens system comprises a switchable optical element having a first mode and a second mode,
 characterised in that the element includes a first fluid, a second fluid and a wavefront modifier having a part through which said radiation beam is arranged to pass, wherein
 in the first mode the switchable optical element has a first fluid configuration in which said part is substantially covered by the first fluid, and 
 in the second mode the switchable optical element has a second, different, fluid configuration in which said part is substantially covered by the second fluid 
   
     
     
         2 . A zoom optical system according to  claim 1 , wherein the first fluid is a liquid and the second fluid is gaseous. 
     
     
         3 . A zoom optical system according to  claim 1 , wherein the switchable optical element comprises a common first fluid electrode, a second, different, fluid electrode and a third, different, fluid electrode, wherein
 in the first fluid configuration the element is arranged to provide switchable electrowetting forces by applying a first voltage across said first and second fluid electrodes, and   in the second fluid configuration the element is arranged to provide different switchable electrowetting forces by applying a second, different, voltage across said first and third fluid electrodes.   
     
     
         4 . A zoom optical system according to  claim 1 , wherein the switchable optical element comprises a further wavefront modifier having a different part through which said radiation beam is arranged to pass, wherein
 the wavefront modifier is adapted to perform a first wavefront modification and the further wavefront modifier is adapted to perform a second, different, wavefront modification which is arranged to complement the first wavefront modification.   
     
     
         5 . A zoom optical system according to  claim 1 , wherein the wavefront modifier has a face, wherein said face is substantially spherical or aspherical, and said part is on said face. 
     
     
         6 . A zoom optical system according to  claim 1 , wherein said first lens is a fluid meniscus lens which comprises different fluids separated by a fluid meniscus having a curvature,
 wherein the optical system further comprises a control system and the variable focus comprises variations in the fluid meniscus curvature, wherein the control system is arranged to control the variable focus using meniscus electrowetting forces.   
     
     
         7 . A zoom optical system according to  claim 6 , wherein the fluid meniscus lens further comprises a first electrode and a second, different, electrode and the control system is arranged to apply a voltage across said first and second meniscus electrodes to provide said meniscus electrowetting forces. 
     
     
         8 . A zoom optical system according to  claim 1 , wherein the lens system comprises a solid lens capable of being arranged at varying spatial positions relative to the switchable optical element. 
     
     
         9 . A zoom optical system according to  claim 1 , wherein said lens system comprises a liquid crystal lens having a varying optical power. 
     
     
         10 . Image capturing apparatus comprising a zoom optical system according to  claim 1 , wherein with the optical system being in said first mode, the apparatus is adapted to capture an image with a first zoom setting, and with the optical system being in said second mode, said apparatus is adapted to capture an image with a second, different, zoom setting. 
     
     
         11 . Image capturing apparatus according to  claim 10 , wherein said image capturing apparatus further comprises a digital zoom system arranged to introduce a digital zoom factor to an image captured in the first mode and/or an image captured in the second mode.