12 October 2010 Test of film thickness based on annular sub-aperture stitching interference
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The technology of annular sub-aperture stitching interference used in film thickness testing is an efficient route with the characters of high-resolution and low-cost, which don't need compensation with auxiliary components. In this contribution, the interference methods of film thickness testing and principles of annular sub-aperture stitching are introduced, and then a model of annular sub-aperture stitching is established on the interference phase of thin film; finally, Sub-aperture spatial phases are unwrapped by fast Fourier transform (FFT) algorithms, and based on this, annular image is obtained by Zernike polynomial fitting algorithm and stitching objective function. The processing algorithms program are written and simulated by a computer. A variety of affecting the accuracy of splicing factors of the errors are analyzed in detail, and the solutions are given to reduce the errors, and proposed changes to the existing experimental platform. The results show that the PV value and the RMS value of phase residuals of full aperture splicing are 0.0092λ and 0.0036λ before and after stitching respectively, and it achieves a large aperture high-precision detection of film thickness.
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Li-hong Yang, Jun-hong Su, Zhi-li Chen, "Test of film thickness based on annular sub-aperture stitching interference", Proc. SPIE 7656, 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment, 765661 (12 October 2010); doi: 10.1117/12.866735; https://doi.org/10.1117/12.866735

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