Method and apparatus for profiling surfaces using diffracative optics

A method for profiling an object surface using desensitized interference fringes comprising the steps of

• illuminating a diffractive optical assembly with a source of light,
• dividing the source light illuminating said diffractive optical assembly into two beams which propagate in two different directions through said diffractive optical assembly, said beams exiting said diffractive optical assembly substantially overlapping adjacent said object surface with said beams impinging upon said object surface at substantially the same place at two different incident angles,
• reflecting said impinging beams from said object surface back toward said diffractive optical assembly, said reflected beams passing back through said diffractive optical assembly in different directions, and
• recombining said reflected beams passing back through said diffractive optical assembly to form an interference pattern representative of the surface profile of said object surface, said interference pattern having reduced sensitivity to surface deformation and surface roughness, said illuminating step comprising the step of illuminating said diffractive optical assembly with a broadband spatially incoherent light source.