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US 4,624,569 AGranted
Real-time diffraction interferometer
AssigneeLockheed Missiles & Space Company, Inc.
InventorOsuk Y. Kwon
Life of this patent
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AssigneeLockheed Missiles & Space Company, Inc.
InventorOsuk Y. Kwon
Estimating the term…
A real-time diffraction interferometer for analyzing an optical beam comprises converging means (13) for bringing the beam to a focus at focal point (14), and an apertured grating structure (20) positionable adjacent the focal point (14). The apertured grating structure (20) comprises a transparent substrate (10'), an obverse surface of which is coated with a translucent coating (11) except for a pinhole-sized spot (12) that is left uncoated so as to function as an aperture in the coating (11). A reverse surface of the substrate (10') has a lenticulate surface configuration, which functions as a diffraction grating. The beam incident upon the apertured grating structure (20) is separated into a major portion, which is transmitted with attenuated intensity through the translucent coating (11), and a minor portion, which is transmitted with undiminished intensity through the pinhole aperture (12). The major portion of the beam is diffracted into spatially separated diffraction components, and the minor portion of the beam is diffracted by the pinhole aperture (12) so as to acquire a spherical wavefront. Interference patterns produced by interference of the spherical wavefront with each of the wavefronts of the zeroth order and the positive and negative first-order diffraction components of the intensity-attenuated beam transmitted by the coating (11) are separately imaged on conventional solid-state photodetectors (21, 22 and 23).
Apparatus for monitoring quality of an optical beam wavefront, said apparatus comprising:
An apertured grating structure for separating an optical beam into first and second portions, said grating structure having a homogeneous diffraction grating of uniform grating period for causing said first portion of said beam to be diffracted into a plurality of components corresponding to different diffraction orders, said components of said first portion of said beam produced by said diffraction grating being of different phases with respect to each other, said grating structure being only partially transparent to said beam except for an apertured portion of said grating structure that is substantially transparent to said beam, said apertured portion of said grating structure defining a pinhole aperture that is dimensioned to cause said second portion of said beam to have a substantially spherical wavefront, said second portion of said beam interfering with each of said components of said first portion of said beam so as to produce a plurality of separate interference patterns of different phases with respect to each other, said aperture being positioned on said grating structure with respect to said diffraction grating so as to enable a selected phase difference between any two of said components of said first portion of said beam to be obtained.
The apertured grating structure of claim 17 wherein said translucent coating is provided on said surface that is configured as said diffraction grating.
Dependencies are inferred from the claim text.