Patent ID: 7619191

Claim:
A differential sensing device for measuring a wavefront curvature using increased spatial sampling for wavefront testing comprising: a sampling sensor having an output beam; an optical element to split said output beam into a first, second and third beam, each of said first, second and third beams traveling in at least one of an x, y and z direction, respectively; a first, second and third lenslet array in the path of the first, second and third beam, respectively, to generate a corresponding first, second and third sampling grid each having plural grid points; a shearing element for shifting said plural grid points a distance in a horizontal and a vertical direction to produce plural sampling grids each having plural grid points the displacement of the shifting being less than a pitch size of the lenslet array; and a measuring device for measuring plural slopes of plural wave fronts at each grid point on the spatial sampling grid to obtain wave front normal curvatures and corresponding twist curvature terms for determining a principal curvature and direction, wherein said plural slopes at each of the plural grid points is measured approximately simultaneously before and after differentially shifting the sampling grid.