Method and apparatus for generating a plurality of radiation beams from incident radiation in a multiple wavelength interferometer

Claim 2

Apparatus for generating a plurality of radiation beams from incident radiation, each of the beams being directed to a different region of space, comprising: a substrate; and at least one region formed within a surface of said substrate, said at least one region defining a blazed diffraction grating for deviating incident radiation into a radiation beam, wherein, for at least two wavelengths of interest of the radiation beam, the at least two wavelengths of interest are simultaneously and efficiently deviated at a same, predetermined angle in accordance with the expression λ.sub.1 /λ.sub.2 =m.sub.2 /m.sub.1 ; wherein λ 1 and λ 2 are two wavelengths of interest, and wherein m 1 is a diffraction order of λ 1 and m 2 is a diffraction order of λ 2 .

Claim 3

Apparatus as set forth in claim 1 wherein said blazed diffraction grating is a blazed transmission grating having a plurality of grooves spaced apart from one another in a parallel manner, and wherein each of the grooves is fabricated with an angle given by, φ=arc tan [(n-cos θ)/sinθ], where n is the refractive index of the substrate material for the wavelengths of interest and where θ is a diffraction angle for each of the wavelengths of interest.

Claim 4

Apparatus as set forth in claim 1 wherein said blazed diffraction grating is a blazed reflection grating having a plurality of grooves spaced apart from one another in a parallel manner, and wherein each of the grooves is fabricated with an angle φ given by, φ=90°-(θ/2), wherein θ is an angle of diffraction.

Claim 5

Interferometric apparatus comprising: means for generating a source beam of radiation having at least two constituent wavelengths of interest; means for splitting the source beam into a reference beam and into a measurement beam; means, optically coupled to said measurement beam, for differentiating the measurement beam into a plurality of pencil beams each of which is directed to a reflective region upon a surface under measurement; and means for interferometrically comparing, to the reference beam, each of the pencil beams reflecting back from the surface under measurement so as to determine a distance to each of the reflected regions, wherein said differentiating means comprises a substrate; and at least one region formed within a surface of said substrate, said at least one region defining a blazed diffraction grating for deviating incident radiation into a radiation beam, wherein, for at least two wavelengths of interest of the radiation beam, the at least two wavelengths of interest are simultaneously deviated at a same, predetermined angle in accordance with the expression λ.sub. λ.sub. 2m.sub.2 /m.sub.1 ; wherein λ 1 and λ 2 are two wavelengths of interest, and wherein m 1 is a diffraction order of λ 1 and m 2 is a diffraction order of λ 2 .

Claim 6

Interferometric apparatus comprising: means for generating a source beam of radiation having at least two constituent wavelengths of interest; means for splitting the source beam into a reference beam and into a measurement beam; means, optically coupled to said measurement beam, for differentiating the measurement beam into a plurality of pencil beams each of which is directed to a reflective region upon a surface under measurement; and means for interferometrically comparing, to the reference beam, each of the pencil beams reflecting back from the surface under measurement so as to determine a distance to each of the reflected regions, wherein said differentiating means comprises a substrate; and at least one region formed within a surface of said substrate, said at least one region defining a blazed diffraction grating for deviating incident radiation into a radiation beam, wherein, for at least two wavelengths of interest of the radiation beam, the at least two wavelengths of interest are simultaneously deviated at a same, predetermined angle in accordance with the expression λ.sub. λ.sub. 2m.sub.2 /m.sub.1 ; wherein λ 1 and λ 2 are two wavelengths of interest, and wherein m 1 is a diffraction order of λ 1 and m 2 is a diffraction order of λ 2 .

Claim 7

Interferometric apparatus as set forth in claim 4 wherein each blazed diffraction grating is a blazed reflection grating defined by a plurality of grooves spaced apart from one another in a parallel manner, and wherein each of the grooves is fabricated with an angle φ given by, φ=90°-(φ/2), wherein is an angle of diffraction.

Claim 8

Interferometric apparatus as set forth in claim 4 wherein each blazed diffraction grating is a blazed transmission grating having a plurality of grooves spaced apart from one another in a parallel manner, and wherein each of the grooves is fabricated with an angle φ given by, φ=arc tan [(n-cos θ)/sin θ], where n is the refractive index of the substrate material for the wavelengths of interest and where θ is a diffraction angle for each of the wavelengths of interest.

Claim 9

Interferometric apparatus as set forth in claim 4 wherein said generating means is comprised of a plurality of laser means each of which outputs one or more of said wavelengths of interest.

Claim 10

Interferometric apparatus as set forth in claim 4 wherein said generating means includes means for collimating said source beam.

Claim 11

Interferometric apparatus as set forth in claim 4 wherein each of said reflective regions includes a retroreflector.

Claim 12

Interferometric apparatus as set forth in claim 4 wherein said comparing means includes: a plurality of photodetector means disposed for receiving said reference beam; and a plurality of lens means individual ones of which are disposed for receiving and directing one of the reflected pencil beams to one of said photodetector means.

Claim 15

A method as set forth in claim 11 wherein each blazed diffraction grating is a blazed transmission grating defined by a plurality of grooves spaced apart from one another in a parallel manner, and wherein the step of providing includes a step of forming each of the grooves to have an angle φ given by, φ=arc tan [(n-cos θ)/sin θ], where n is a refractive index of the substrate material for the wavelengths of interest and where θ is a diffraction angle for each of the wavelengths of interest.

Claim 16

A method as set forth in claim 11 wherein each blazed diffraction grating is a blazed reflection grating defined by a plurality of grooves spaced apart from one another in a parallel manner, and wherein the step of providing includes a step of forming each of the grooves to have an angle φ given by, φ=90°-(θ/2), wherein θ is an angle of diffraction.