Method for compensation during the process of wavefront reconstruction in grating-based lateral shearing interferometry
AssigneeShanghai Institute of Optics And Fine Mechanics, Chinese Academy of Sciences
InventorsPeng Li, Feng Tang, Xiangzhao Wang, Yunjun Lu, Yang Liu
Life of this patent
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Abstract
Method for simultaneously compensating pupil coordinate distortion and shear amount change in a process of wavefront reconstruction in grating transverse shear interference. Where a wavefront is diffracted by a grating, the shapes and light paths of the diffracted wavefronts of all the orders are different, so that on one hand, a coordinate system detected by a detector plane is distorted relative to a pupil coordinate system, and on the other hand, a shear amount changes along with a coordinate position.
Claims6
A method for simultaneously compensating pupil coordinate distortion and shear amount change in a process of wavefront reconstruction in grating transverse shear interference, comprising:
- (1) generating a differential wavefront interferogram of an optical system to be measured in X and Y-directions by using a grating transverse shear interferometer, and receiving differential wavefront interferograms Ix(xd,yd) and Iy(xd,yd) by using a two-dimensional photoelectric sensor, wherein (xd,yd) is a pixel position coordinate system on the two-dimensional photoelectric sensor;
- (2) extracting diffracted wavefronts of n1-order and n2-order, and differential phases Sx(xd,yd) and Sy(xd,yd) in X and Y-directions from the generated differential wavefront interferograms, wherein n1≠n2 and both are an integer;
- (3) using an inversing method to solve corresponding position coordinates of light rays received by different pixels on a plane of the two-dimensional photoelectric sensor a pupil plane along diffraction light paths of the n1 and n2 orders in the case of shearing in the X-direction and the Y-direction, respectively, wherein the position coordinates obtained in the case of shearing in the X-direction are (xn1x,yn1x) and (xn2x,yn2x), and the position coordinates obtained in the case of shearing in the Y-direction are (xn1y,yn1y) and (xn2y,yn2y);
- (4) selecting first m (m>1) polynomials to build a set of equations according to the obtained coordinate systems (xn1x,yn1x), (xn2x,yn2x), (xn1y,yn1y), (xn2y,yn2y), and solving to obtain a coefficient Ci (i=1, 2, . . . , m) corresponding to each polynomial when the wavefront to be measured is expressed by the selected polynomials;
- and
- (5) reconstructing a wavefront WF according to the following Equation:
- W
- F
- =
- ∑
- i
- =
- 1
- m
- C
- i
-
- Z
- i
- ,
- wherein Zi represents an i-th polynomial.
Dependencies are inferred from the claim text.