Fast phase processing of off-axis interferograms

Patent metadata

Field	Value
Publication number	US-2016290782-A1
Application number	US-201615089691-A
Country	US
Kind code	A1
Filing date	Apr 4, 2016
Priority date	Apr 2, 2015
Publication date	Oct 6, 2016
Grant date	—

Abstract

Techniques for extracting phase data of off-axis interferogram images are disclosed. At least one sample-related interferogram image associated with a sample is spectrally decomposed to obtain a set of frequency components thereof, and a portion of the set of frequency components is used to generate at least one complex image having a reduced size being smaller in size than the sample-related interferogram image and being indicative of the phase data of the at least one sample-related interferogram image. The reduced size complex image is then used to generate a phase image of the least one sample-related interferogram image.

First claim

1 . A computer-implemented method of extracting phase data of off-axis interferogram images, the method comprising:
(i) receiving at least one sample-related interferogram image associated with a sample; (ii) performing spectral decomposition to said at least one sample-related interferogram image to obtain a set of frequency components thereof; (iii) generating from a portion of said set of frequency components at least one complex image having a reduced size being smaller in size than said sample-related interferogram image and being indicative of said phase data; (iv) using said reduced size complex image to generate a phase image of said least one sample-related interferogram image.

2 . The method of claim 1 wherein performing of the spectral decomposition comprises performing a single Fourier transform operation to obtain the frequency components.

3 . The method of claim 2 wherein generating the at least one complex image comprises performing one or more inverse Fourier transform operations.

4 . The method of claim 1 wherein the size of the reduced size complex image is 1/16 of the size of the at least one sample-related interferogram image.

5 . The method of claim 1 wherein the portion of the frequency components used to generate the complex image is indicative of cross-correlation of an interference pattern in said interferogram image.

6 . The method of claim 5 comprising providing a sample-free instance of the interferogram image, performing steps (ii) and (iii) of claim 1 on said sample-free instance image to obtain a reference image indicative of the cross-correlation of the interference pattern, a size of said reference image being smaller than a size of said sample-free instance image, and using said reference image to compensate for stationary aberrations and curvatures in the at least one complex image.

7 . The method of claim 1 comprising enlarging a size of the phase image to provide an enlarged phase image of the interferogram image.

8 . The method of claim 1 comprising asymmetric re-sampling of the at least one interferogram image along an image plane axis so as to reduce size of the interferogram image along said image plane axis, said image plane axis substantially coincides with direction of fringes of said at least one interferogram image.

9 . The method of claim 1 comprising using empty spatial-frequency domain areas of the spectral decomposition used in step (ii) for processing at least one additional sample-related interferogram image and generating a respective at least one additional complex image therefrom indicative of phase data of said at least one additional interferogram image.

10 . The method of claim 9 wherein performing of the spectral decomposition comprises performing a single Fourier transform operation to obtain the frequency components.

11 . The method of claim 10 comprising generating the sample-related interferogram image by summating a first sample-related interferogram image and a transpose of a second sample-related interferogram image.

12 . The method of claim 11 comprising asymmetric re-sampling of the first and second sample-related interferogram images along an image plane axis, before summating said images, so as to reduce sizes of said sample-related interferogram images along said image plane axis, said image plane axis substantially coincides with direction of fringes of said sample-related interferogram images.

13 . The method of claim 12 wherein the generating of the at least one complex image comprises selecting a first spatial-frequency portion of the frequency components and generating therefrom a first complex image being indicative of phase data of the first sample-related interferogram image, and selecting a second spatial-frequency portion of the frequency components and generating therefrom a second complex image being indicative of phase data of the second sample-related interferogram image.

14 . The method of claim 10 comprising generating the sample-related interferogram image as a complex interferogram image constructed from first and second sample-related interferogram images used as real and imaginary parts thereof, respectively.

15 . The method of claim 14 comprising asymmetric re-sampling of the first and second sample-related interferogram images along an image plane axis, before constructing the complex interferogram image, so as to reduce sizes of said sample-related interferogram images along said image plane axis, said image plane axis substantially coincides with direction of fringes of said sample-related interferogram images.

16 . The method of claim 15 wherein the generating of the at least one complex image comprises selecting first and second spatial-frequency portions of the frequency components, generating from a first linear combination of said first and second spatial-frequency portions a first complex image being indicative of phase data of the first sample-related interferogram image and from a second linear combination of said first and second spatial-frequency portions a second complex image being indicative of phase data of the second sample-related interferogram image, said first and second linear combinations comprise a transposition of one of said first and second spatial-frequency portions.

17 . The method of claim 16 wherein the first and second spatial-frequency portions are associates with a common image plane axis.

18 . The method of claim 10 comprising generating the sample-related interferogram image as a complex image constructed from first and second summations of sample-related interferogram images used as its real and imaginary part, respectively, said first summation comprises a first sample-related interferogram image summated with a transpose of a second sample-related interferogram image and said second summation comprises a third sample-related interferogram image summated with a transpose of a fourth sample-related interferogram image.

19 . The method of claim 18 wherein the generating of the at least one complex image comprises: selecting first and second spatial-frequency portions of the frequency components, generating from a first linear combination of said first and second spatial-frequency portions a first complex image being indicative of phase data of the first interferogram image and from a second linear combination of said first and second spatial-frequency portions a second complex image being indicative of phase data of the second interferogram image; and selecting third and fourth spatial-frequency portions of the frequency components, generating from a first linear combination of said third and fourth spatial-frequency portions a third complex image being indicative of phase data of the third interferogram image and from a second linear combination of said third and fourth spatial-frequency portions a fourth complex image being indicative of phase data of the fourth interferogram image, said first and second linear combinations comprise a transposition of one of said first and second spatial-frequency portions.

20 . The method of claim 19 wherein first and second spatial-frequency portions of the frequency components are associated with a first image plane axis, and wherein the third and fourth spatial-frequency portions of the frequency components are associated with a second image plane axis.

21 . The method of claim 20 wherein said first and second image plane axes are orthogonal.

22 . The method of claim 1 wherein t

Assignees

• Ramot At Tel-Aviv Univ Ltd

Inventors

• Girshovitz Pinhas
• Shaked Natan Tzvi

Classifications

• G01B11/0675

  using interferometry · CPC title

• G01B11/2441

  using interferometry · CPC title

• G01B9/021 Primary

  using holographic techniques · CPC title

• G01B11/26

  for measuring angles or tapers; for testing the alignment of axes · CPC title