The imaging spectrometer based on dual photoelastic modulator of unequal retardation amplitudes

Rui Zhang; Zhi-bin Wang; Ting-dun Wen; Yao-li Wang; Ke-wu Li

doi:10.1117/12.2199048

8 October 2015 The imaging spectrometer based on dual photoelastic modulator of unequal retardation amplitudes

Rui Zhang, Zhi-bin Wang, Ting-dun Wen, Yao-li Wang, Ke-wu Li

Proceedings Volume 9675, AOPC 2015: Image Processing and Analysis; 96750U (2015) https://doi.org/10.1117/12.2199048
Event: Applied Optics and Photonics China (AOPC2015), 2015, Beijing, China

Abstract

As the existing photoelastic modulator (PEM) resonant frequency is high (tens to hundreds of kHz), the interference signal frequency is up to hundreds of MHz, even to several GHz. Signal frequency is so high that they can not effectively be detected by charge coupled device (CCD). This paper reports a method for measuring spectroscopy using two PEMs at different frequencies. The difference frequency of dual-PEM system is 2~3 orders of magnitude lower than any one modulation frequency of the two PEMs. Operating the PEMs at slightly different resonant frequencies f₁ and f₂ respectively, the dual-PEM system generates a difference frequency modulation signal. Therefore, interference signal contains low frequency modulation components which carry the information of the incident light. And low frequency modulation component consists of a series of frequency-multiplier signals whose fundamental frequency is equal to (f₁-f₂)/2. The low frequency modulation components can be detected by ordinary CCD. Through Fourier transform, modulation signal of CCD is to get a series of frequency-multiplier signals amplitude. Then the incident light spectra can be obtained by the corresponding matrix operations. Furthermore, this method is to realize object imaging spectral measurement by the way of combining with CCD. The peak retardation amplitude of two PEMs does not require being complete equal, and modulation frequencies f₁ and f₂ do not also require equality. So this can reduce the difficulty of the PEM processing. What’s more, the method makes the traditional PEM have both imaging and spectroscopy measurement functions. The basic principle is introduced, the basic equations is derived, and the feasibility is verified through the corresponding numerical simulation and experiment.

Citation Download Citation

Rui Zhang, Zhi-bin Wang, Ting-dun Wen, Yao-li Wang, and Ke-wu Li "The imaging spectrometer based on dual photoelastic modulator of unequal retardation amplitudes", Proc. SPIE 9675, AOPC 2015: Image Processing and Analysis, 96750U (8 October 2015); https://doi.org/10.1117/12.2199048

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