Patent ID: 6909510

Claim:
A method for measuring the aberrations of a negative lens, comprising: producing a diverging measurement wavefront of light from a first diffracting aperture; positioning a negative lens under test in said diverging measurement wavefront such that said negative lens modifies and substantially transmits said diverging measurement wavefront to produce a first diverging measurement wavefront; introducing an aperture stop at said negative lens under test; converting said first diverging measurement wavefront from a diverging to a converging wavefront with an auxiliary optical element to produce a first converging measurement wavefront; producing a diverging reference wavefront from a second diffracting aperture and phase shifted relative to said diverging measurement wavefront; propagating a portion of said reference wavefront onto a detector; reflecting said first converging measurement wavefront from surface of said second diffracting aperture onto said detector, wherein said reference wavefront and said first converging measurement wavefront combine to form a first interference pattern on said detector; removing said negative lens from said aperture stop; re-positioning said first diffracting aperture relative to said auxiliary optical element such that said diverging measurement wavefront converges therefrom to produce a second converging measurement wavefront; and reflecting said second converging measurement wavefront from surface of said second diffracting aperture onto said detector, wherein said reference wavefront and said converging second measurement wavefront combine to form a second interference pattern on said detector.