Shearing interferometer with dynamic pupil fill

Abstract

A wavefront measurement system includes a source of electromagnetic radiation. An illumination system delivers the electromagnetic radiation to an object plane. A source of a diffraction pattern is in the object plane. A projection optical system projects the diffraction pattern onto an image plane, which includes a mechanism (e.g., a shearing grating) to introduce the lateral shear. A detector is located optically conjugate with the pupil of the projection optical system, and receives an instant fringe pattern, resulting from the interference between sheared wavefronts, from the image plane. The diffraction pattern is dynamically scanned across a pupil of the projection optical system, and the resulting time-integrated interferogram obtained from the detector is used to measure the wavefront aberration across the entire pupil.

1 . A wavefront measurement system comprising: 
 a source of electromagnetic radiation;    an illumination system that directs said electromagnetic radiation to an object plane;    an object in the object plane producing a diffraction pattern;    a projection optical system that projects an image of said object onto an image plane; and    a detector that receives a fringe pattern from said image plane,    wherein the diffraction pattern is scanned across a pupil of said projection optical system.    
   
   
       2 . The system of  claim 1 , wherein the object includes a tiltable mirror for scanning the diffraction pattern across the pupil.  
   
   
       3 . The system of  claim 1 , wherein the object includes a diffraction grating with variable pitch for scanning the diffraction pattern across the pupil.  
   
   
       4 . The system of  claim 1 , wherein the object includes a refractive prism with a varying wedge angle for scanning the diffraction pattern across the pupil.  
   
   
       5 . The system of  claim 1 , wherein the object includes a spatial light modulator for scanning the diffraction pattern across the pupil.  
   
   
       6 . The system of  claim 1 , wherein the object generates a non-linear phase variation across to scan the diffraction pattern across the pupil.  
   
   
       7 . The system of  claim 1 , wherein the object comprises a stress-birefringent material to scan the diffraction pattern across the pupil.  
   
   
       8 . The system of  claim 1 , further comprising reflective optics for scanning the diffraction pattern across the pupil.  
   
   
       9 . The system of  claim 1 , further comprising refractive optics for scanning the diffraction pattern across the pupil.  
   
   
       10 . The system of  claim 1 , wherein the object includes a movable mirror with a variable surface slope for scanning the diffraction pattern across the pupil.  
   
   
       11 . The system of  claim 1 , wherein the diffraction pattern is dynamically scanned across a pupil of said projection optical system.  
   
   
       12 . The system of  claim 1 , wherein the detector is located in a plane that is optically conjugate with the pupil.  
   
   
       13 . The system of  claim 1 , further comprising a grating in the image plane to generate the fringe pattern.  
   
   
       14 . A wavefront measurement system comprising: 
 an illumination system that delivers electromagnetic radiation to an object plane;    an object in the object plane that generates a beam of the electromagnetic radiation;    a projection optical system that projects the beam onto an image plane; and    a detector that receives a fringe pattern of the beam from the image plane,    wherein the beam is scanned across a pupil of the projection optical system.    
   
   
       15 . The system of  claim 14 , wherein the object includes a tiltable mirror for scanning the beam across the pupil.  
   
   
       16 . The system of  claim 14 , wherein the object includes a diffraction grating with variable pitch for scanning the beam across the pupil.  
   
   
       17 . The system of  claim 14 , wherein the object includes a refractive prism with a varying wedge for scanning the beam across the pupil.  
   
   
       18 . The system of  claim 14 , wherein the object includes a spatial light modulator for scanning the beam across the pupil.  
   
   
       19 . The system of  claim 14 , wherein the source of the diffraction pattern generates a non-linear phase variation across to scan the diffraction pattern across the pupil.  
   
   
       20 . The system of  claim 14 , wherein the source of the diffraction pattern includes a stress-birefringent material for scanning the beam across the pupil.  
   
   
       21 . The system of  claim 14 , further comprising reflective optics for scanning the beam across the pupil.  
   
   
       21 . The system of  claim 14 , further comprising refractive optics for scanning the beam across the pupil.  
   
   
       22 . The system of  claim 14 , wherein the object includes a movable mirror with a variable surface slope for scanning the beam across the pupil.  
   
   
       23 . The system of  claim 14 , wherein the detector is located in a plane that is optically conjugate with the pupil.  
   
   
       24 . The system of  claim 14 , further comprising a grating in the image plane to generate the fringe pattern.  
   
   
       25 . A method of measuring a wavefront of an optical system comprising: 
 generating electromagnetic radiation at a source;    delivering said electromagnetic radiation to an object plane of said optical system;    generating a diffraction pattern at said object plane;    scanning the diffraction pattern across a pupil of said optical system;    receiving an image of said source while scanning the diffraction pattern; and    determining wavefront parameters from said image.    
   
   
       26 . The method of  claim 25 , wherein the scanning step includes tilting a mirror to direct the diffraction pattern across the pupil.  
   
   
       27 . The method of  claim 25 , wherein the scanning step includes moving a diffraction grating with variable pitch to direct the diffraction pattern across the pupil.  
   
   
       28 . The method of  claim 25 , wherein the scanning step includes adjusting a refractive prism with a varying wedge angle to direct the diffraction pattern across the pupil.  
   
   
       29 . The method of  claim 25 , wherein the scanning step includes adjusting a spatial light modulator to direct the diffraction pattern across the pupil.  
   
   
       30 . The method of  claim 25 , wherein the scanning step uses reflective optics to scan the diffraction pattern across the pupil.  
   
   
       31 . The method of  claim 25 , wherein the scanning step uses refractive optics to scan the diffraction pattern across the pupil.  
   
   
       32 . A method of measuring a wavefront of a projection optical system comprising: 
 (1) delivering electromagnetic radiation at an object plane of the projection optical system so as to generate a beam directed at the projection optical system;    (2) positioning a detector below an image plane of the projection optical system;    (3) receiving a fringe pattern of the beam at the detector while simultaneously scanning the beam across a pupil of the optical system; and    (4) calculating wavefront aberrations from the fringe pattern.    
   
   
       33 . A wavefront measurement system comprising: 
 means for generating electromagnetic radiation;    means for delivering said electromagnetic radiation to an object plane of a projection optical system;    means for generating a diffraction pattern in the object plane;    the projection optical system that projects an image of said diffraction pattern onto an image plane; and    means for detecting a fringe pattern from said image plane,    means for scanning the diffraction pattern across a pupil of said projection optical system.