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US 8,526,008 B2Granted
Interferometer with paraboloidal illumination and imaging optic and tilted imaging plane
AssigneeCorning Incorporated
InventorsJoshua Monroe Cobb, Thomas James Dunn, John Weston Frankovich
Life of this patent
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Abstract
A Fizeau interferometer incorporates an off-axis paraboloidal reflector that forms virtual images of reference and test surfaces and a camera lens that converts the virtual images into real images on a camera detector surface. The camera detector surface is arranged together with the camera lens to accommodate tilting of the virtual images by the off-axis paraboloidal reflector.
Claims20
A Fizeau interferometer for measuring a test surface of an object comprising:
- an off-axis paraboloidal reflector having a paraboloidal axis and a paraboloidal reflective surface that is offset from the paraboloidal axis;
- an effective light source located with respect to the off-axis paraboloidal reflector so that coherent light emanating from the light source along a main optical axis to the off-axis paraboloidal reflector is collimated by reflection from the offset paraboloidal reflective surface;
- a Fizeau reference surface oriented for receiving the collimated light at normal incidence, reflecting a first portion of the light, and transmitting a second portion of the light to and from the test surface;
- the off-axis paraboloidal reflector being arranged for forming overlapping virtual images of the of the reference and test surfaces, the overlapping virtual images being tilted through a non-normal angle to the main optical axis;
- and
- a camera detector surface together with a camera lens for converting the virtual images of the reference and test surfaces into real images on the camera detector surface having an optical orientation matching an optical orientation through which the virtual images are tilted.
3 more elements
A method of measuring a test surface of an object with a Fizeau interferometer comprising:
- emitting coherent light from an effective light source;
- propagating the coherent light toward an off-axis paraboloidal reflector along a main optical axis;
- reflecting the coherent light from the off-axis paraboloidal reflector toward a Fizeau reference surface as a collimated beam;
- reflecting a portion of the collimated beam from the Fizeau reference surface and transmitting another portion of the collimated beam to and from the test surface;
- collecting the light portions from the reference and test surfaces with the off-axis paraboloidal reflector and reflecting the collected light portions from the off-axis paraboloidal reflector to form overlapping virtual images of the reference and test surfaces in an optical orientation that is tilted through a non-normal angle with respect to the main optical axis;
- converting the virtual images of the reference and test surfaces into real images on a camera detector surface having an optical orientation matching the optical orientation through which the virtual images are tilted;
- and
- monitoring an interference pattern formed by the real images of the reference and test surfaces for measuring differences between the reference and test surfaces.
5 more elements
Dependencies are inferred from the claim text.