An Improved Fitting Method for Predicting the Zernike Coefficient–Wavelength Curves

Broadband transmitted wavefront measurement is a detection method that uses transmitted wavefronts at a few specific wavelengths though a function of Zernike coefficients and wavelength to predict other transmitted wavefronts at any wavelength within a certain range. This method is used when the des...

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Main Authors: Fang Wang, Qiyuan Zhang, Haoyu Wang, Dayong Zhu, Huaikang Zhu, Wenxin Jia, Sen Han
Format: Article
Language:English
Published: IEEE 2021-01-01
Series:IEEE Photonics Journal
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Online Access:https://ieeexplore.ieee.org/document/9360526/
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author Fang Wang
Qiyuan Zhang
Haoyu Wang
Dayong Zhu
Huaikang Zhu
Wenxin Jia
Sen Han
author_facet Fang Wang
Qiyuan Zhang
Haoyu Wang
Dayong Zhu
Huaikang Zhu
Wenxin Jia
Sen Han
author_sort Fang Wang
collection DOAJ
description Broadband transmitted wavefront measurement is a detection method that uses transmitted wavefronts at a few specific wavelengths though a function of Zernike coefficients and wavelength to predict other transmitted wavefronts at any wavelength within a certain range. This method is used when the designed wavelength of the interferometer and the detection wavelength are different. The function of the Zernike coefficients and wavelength can be expressed by the Conrady formula which can be used to describe a monotonic function curve or a function curve with an inflection point. Two methods, i.e., solving and fitting, can be used to determine the coefficients of the Conrady formula. Owing to the inevitable errors in the actual measurements, the fitting method is preferred to determine the coefficients of the Conrady formula. However, by analyzing the Conrady formula, it was found that the curve obtained by fitting the Conrady formula is a monotonic curve. This method cannot be used to obtain a curve with an inflection point or a slow-changing curve in the long waveband. In this paper, we propose an improved data fitting approach that transforms the Conrady formula into a polynomial formula to fit a given set of data for determining the Conrady formula coefficients. The correctness of the method was verified via simulations. Finally, the feasibility of the proposed method was verified by changing the light source and using the Fizeau interferometer to measure the transmitted wavefront of the doublet lens. To ascertain the feasibility of using visible light to predict the invisible light band, a near-infrared 1064 nm light source was added to the experimental set-up to broaden the range of the transmitted wavefront prediction waveband. Experimental results showed that the conversion polynomial fitting method can be used to obtain monotonic curves and the curve with an inflection point and a slow-changing curve in the long waveband, thereby mitigating the limitation of directly fitting the Conrady formula using a set of data points. Furthermore, using this method, we verified that the visible light can be used to predict the transmitted wavefront at any wavelength in the invisible light band. This observation is highly significant for the practical applications of the broadband transmitted wavefront measurement technique.
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spelling doaj-art-6997a55d94aa40e4906a3bd9032105282025-08-20T03:15:50ZengIEEEIEEE Photonics Journal1943-06552021-01-0113211710.1109/JPHOT.2021.30597649360526An Improved Fitting Method for Predicting the Zernike Coefficient–Wavelength CurvesFang Wang0Qiyuan Zhang1Haoyu Wang2Dayong Zhu3Huaikang Zhu4Wenxin Jia5Sen Han6School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai, ChinaSuzhou H&L Instruments LLC, Suzhou, ChinaSchool of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai, ChinaSchool of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai, ChinaSchool of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai, ChinaSuzhou University of Science and Technology, Suzhou, ChinaSchool of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai, ChinaBroadband transmitted wavefront measurement is a detection method that uses transmitted wavefronts at a few specific wavelengths though a function of Zernike coefficients and wavelength to predict other transmitted wavefronts at any wavelength within a certain range. This method is used when the designed wavelength of the interferometer and the detection wavelength are different. The function of the Zernike coefficients and wavelength can be expressed by the Conrady formula which can be used to describe a monotonic function curve or a function curve with an inflection point. Two methods, i.e., solving and fitting, can be used to determine the coefficients of the Conrady formula. Owing to the inevitable errors in the actual measurements, the fitting method is preferred to determine the coefficients of the Conrady formula. However, by analyzing the Conrady formula, it was found that the curve obtained by fitting the Conrady formula is a monotonic curve. This method cannot be used to obtain a curve with an inflection point or a slow-changing curve in the long waveband. In this paper, we propose an improved data fitting approach that transforms the Conrady formula into a polynomial formula to fit a given set of data for determining the Conrady formula coefficients. The correctness of the method was verified via simulations. Finally, the feasibility of the proposed method was verified by changing the light source and using the Fizeau interferometer to measure the transmitted wavefront of the doublet lens. To ascertain the feasibility of using visible light to predict the invisible light band, a near-infrared 1064 nm light source was added to the experimental set-up to broaden the range of the transmitted wavefront prediction waveband. Experimental results showed that the conversion polynomial fitting method can be used to obtain monotonic curves and the curve with an inflection point and a slow-changing curve in the long waveband, thereby mitigating the limitation of directly fitting the Conrady formula using a set of data points. Furthermore, using this method, we verified that the visible light can be used to predict the transmitted wavefront at any wavelength in the invisible light band. This observation is highly significant for the practical applications of the broadband transmitted wavefront measurement technique.https://ieeexplore.ieee.org/document/9360526/Broadband transmitted wavefront measurementconversion polynomial fittingnear-infrared
spellingShingle Fang Wang
Qiyuan Zhang
Haoyu Wang
Dayong Zhu
Huaikang Zhu
Wenxin Jia
Sen Han
An Improved Fitting Method for Predicting the Zernike Coefficient–Wavelength Curves
IEEE Photonics Journal
Broadband transmitted wavefront measurement
conversion polynomial fitting
near-infrared
title An Improved Fitting Method for Predicting the Zernike Coefficient–Wavelength Curves
title_full An Improved Fitting Method for Predicting the Zernike Coefficient–Wavelength Curves
title_fullStr An Improved Fitting Method for Predicting the Zernike Coefficient–Wavelength Curves
title_full_unstemmed An Improved Fitting Method for Predicting the Zernike Coefficient–Wavelength Curves
title_short An Improved Fitting Method for Predicting the Zernike Coefficient–Wavelength Curves
title_sort improved fitting method for predicting the zernike coefficient x2013 wavelength curves
topic Broadband transmitted wavefront measurement
conversion polynomial fitting
near-infrared
url https://ieeexplore.ieee.org/document/9360526/
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