Rapid in-situ mastering of an aspheric fizeau
AssigneeZygo Corporation
InventorsChristopher James Evans, Michael Küchel
Life of this patent
Estimating the term…
Abstract
Interferometric apparatus and methods by which aspheric surfaces and wavefronts may be precisely measured. The apparatus is provided with two modes of operation. In one mode, the apparatus is configured generally as a Fizeau interferometer in which an aspheric reference surface is used to permit the rapid, robust measurement of the difference between the aspheric reference surface and an aspheric test optic or wavefront. In another mode of operation, the aspheric test surface itself is completely characterized through in-situ use of an interferometric scanning technique using a spherical reference surface.
Claims15
An interferometric method for measuring rotationally and non-rotationally symmetric optics, said interferometric method comprising the steps of:
- scanning at least one aspheric reference surface with a spherical reference surface to determine the shape of said aspheric reference surface;
- aligning a test optic to be measured with said aspheric reference surface placed closely adjacent the test optic by a predetermined distance;
- illuminating said at least one reference aspherical surface with a beam having a predetermined wavefront such that part of said predetermined wavefront is reflected from said reference aspherical surface to serve as reference wavefront and part is transmitted as a continuing aspherical wavefront that impinges on the said test optic and returns therefrom as a measurement wavefront that travels back towards said reference aspherical surface;
- and
- combining said reference and measurement wavefronts to form an interferogram containing phase information indicative of the shape of the wavefront generated by the test optic.
Interferometric apparatus for measuring rotationally and non-rotationally symmetric test optics, said interferometric apparatus comprising:
- means for mounting a test optic to be measured so that it can be illuminated as it is precisely aligned;
- means for scanning an aspheric reference surface to precisely determine its shape;
- means for aligning said reference aspherical surface closely adjacent said test optic to be measured and spaced therefrom by a predetermined distance;
- and
- means for illuminating said reference aspherical surface with a beam having a predetermined wavefront whose shape is substantially the same as that of said reference aspherical surface so that part of said predetermined wavefront is reflected from said reference aspherical surface to serve as reference wavefront and part is transmitted as a continuing aspherical wavefront that impinges on the said test optic and returns therefrom as a measurement wavefront that travels back towards said reference aspherical surface, said reference and measurement wavefronts combining to form an interferogram containing phase information indicative of the shape of the wavefront generated by the test optic.
Dependencies are inferred from the claim text.