Mr. Caixun Bai Profile

Caixun Bai

at Nanjing Univ of Science and Technology

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Publications (3)

Proceedings Article | 18 December 2019 Paper

A high-precision wavelength calibration method based on Fourier transform imaging spectrometer

Yixuan Xu, Jianxin Li, Caixun Bai, Jie Liu, Yi Zong, Mingliang Duan

Proceedings Volume 11337, 1133708 (2019) https://doi.org/10.1117/12.2541545

KEYWORDS: Calibration, Fourier transforms, Spectroscopy, Spectral calibration, Interferometers, Sagnac interferometers

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Fourier Transform Imaging Spectrometer(FTIS) is an instrument cable of acquiring two-dimensional spatial information and one-dimensional spectral information. The FTIS has attracted much attention and is widely applied in the fields like military reconnaissance, remote sensing, biomedicine, environmental monitoring, etc. The FTIS acquires the spectral intensity in different wavelengths by performing Fourier transform on the white light interference signal of the target generated by the FTIS. The spectral curve obtained directly by Fourier transform reflects the relationship between the wavenumber order and the spectral intensity. So wavelength calibration is required to convert the above relationship into the relationship between the wavelength and the spectral intensity, which makes it more intuitive. Therefore, wavelength calibration is a necessary step for FTIS to recovery spectrum. The traditional wavelength calibration method can only get the wavenumber order in the range of integer because of the picket fence effect in Fourier transform. It will definitely ignore the fractional part which results in the inaccurate wavenumber order, which will directly affect the precision of the wavelength calibration result. In order to solve this problem, a high-precision wavelength calibration method based on Fourier transform imaging spectrometer is proposed according to the principle of FTIS and Fourier transform. This method can calculate the wavenumber order with the precision of percentile, which will reduce the error of wavelength calibration effectively. As a result, the precision of spectral calibration can be increased eventually. This method realizes high-precision wavelength calibration by the way of adding zero to the interference fringe in the spatial domain. The core of the method is getting a more precise wavenumber order. The brief process of obtaining wavenumber order is as follows: First, the FTIS acquires the interference fringe of a monochromatic laser. Second, the original interference fringe is extrapolated with zero. Third, the subtle spectrum can be obtained by performing Fourier transform on the extrapolated interference fringe. Finally, the precise wavenumber order is calculated by dividing the abscissa of the peak value by the extrapolation multiple. The principle of this method is investigated and related simulations are then carried out. The simulation results indicate that the wavenumber order calculated by the method have the same precision with the preset parameters, which illustrates that the method can calculate the wavenumber order more accurately. Therefore, the method can improve the precision of the spectral calibration. Besides, related experiments are also performed. The laser interference fringes of different wavelengths generated by the actual FTIS all apply the method to get the wavenumber orders in the frequency domain. Then a curve which is the wavelength calibration function is fitted using the discrete relation between the wavelengths and the wavenumber orders. A laser whose wavelength is known is measured by the FTIS with the wavelength calibration function got by the proposed method. The error of the wavelength measurement result is one-fifth of the traditional method. The simulations and the experiment results indicate that the proposed method can improve the precision of the wavelength calibration, which provides the theory and technology support for spectral measurement using FTIS. It also provides a possibility for the development of FTIS towards the super resolution direction.

Proceedings Article | 13 April 2015 Paper

System design of Fourier transform imaging spectrometer using tunable lateral shearing splitter

Xin Meng, Jianxin Li, Caixun Bai, Rihong Zhu

Proceedings Volume 9522, 952219 (2015) https://doi.org/10.1117/12.2179843

KEYWORDS: Collimators, Spectroscopy, Fourier transforms, Imaging systems, Objectives, Modulation transfer functions, Glasses, Prisms, Spatial resolution, Interferometers

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Proceedings Article | 13 April 2015 Paper

Analysis of system parameters for interferometric imaging spectrometer

Caixun Bai, Jianxin Li, Xin Meng, Yan Shen, Rihong Zhu

Proceedings Volume 9522, 95221A (2015) https://doi.org/10.1117/12.2179847

KEYWORDS: Imaging systems, Spectroscopy, Interferometry, Mirrors, Sensors, Beam splitters, Lithium, Spectral resolution, Prototyping, Imaging spectroscopy

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