Method and apparatus for profiling surfaces using diffracative optics
First Claim
1. A method for profiling an object surface using desensitized interference fringes comprising the steps ofilluminating 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, andrecombining 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.
1 Assignment
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Accused Products
Abstract
Optical system for measuring surface topography, comprised of a light source (30), a diffractive optical assembly (70,72,73) comprised of two or more diffraction gratings, holograms or like diffractive optics (120, 130;122, 132;123, 133), electronic detection means and digital signal processing means (10, 110) for determining surface height from interference data. The diffractive optical assembly (70,72,73) divides the incident light into two beams (150,160;152,162;153,163), which subsequently impinge upon the object (20) at the same place on the object surface (70) but at two different angles of incidence. After reflection from the object surface, the beams pass separately back through the diffractive optical assembly (70,72,73), after which they combine once again and form an interference pattern representative of the surface topography. The equivalent wavelength of the resultant interference pattern is much greater than the illumination wavelength.
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Citations
45 Claims
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1. 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.
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25. An optical surface profiler for profiling an object surface using desensitized interference fringes, said profiler comprising an illumination source;
- a diffractive optical assembly optically aligned between said illumination source and said object surface, said illumination source illuminating said diffractive optical assembly, said diffractive optical assembly comprising means for 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 and impinging upon said object surface at substantially the same place at two different incident angles, said object surface 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;
means for recombining said reflected beams to form an interference pattern representative of the surface profile of said object surface;
said illumination source comprising a broadband spatially incoherent light source. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45)
- a diffractive optical assembly optically aligned between said illumination source and said object surface, said illumination source illuminating said diffractive optical assembly, said diffractive optical assembly comprising means for 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 and impinging upon said object surface at substantially the same place at two different incident angles, said object surface 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;
Specification