Spectral calibration of spectrometer based on interference fringes
TONG Jun hai1, ZHONG Shun chong1，2, ZHANG Qiu kun1, LIN Jie wen1, FU Xi bin3
(1.Laboratory of Optics, Terahertz and Non destructive Testing & Evaluation, School of Mechanical Engineering 
and Automation, Fuzhou University, Fuzhou 350108, China;
2.Fujian Key Laboratory of Medical Instrument and Pharmaceutical Technology, Fuzhou 350000, China;
3.Xiamen Special Equipment Inspection Institute, Xiamen 361000, China)


Abstract: In order to get fast and accurate calibration of spectrometer spectral bandwidth and to determine its spectral abscissa, in optical coherence tomography (OCT) system, a method for calibrating spectral bandwidth and determining the nonlinear distribution law of the wavelength by interference fringes, was proposed. A single frequency laser was employed to determine the CCD pixel position of the specific wavelength. Subsequently, according to the relationship between optical path differences and the number of interference fringe cycles, the bandwidth of a spectrometer was determined. Polynomial function was used to fit the interference fringes. After that, spectral intensity was smoothed and peak pitches were interpolated. Distribution disciplines of the wavelength in the abscissa was determined according to the relationship between the peak pitches and the wavenumber. Two comparative tests show that the spectral bandwidth calibration error is about ±0.15 nm. The calibration error is better than the traditional calibration method using mercury lamp. The results indicate that the resolution and the signal to noise ratio of the OCT system could be greatly improved after the wavelength calibration. Hence, the feasibility of this proposed method for spectral calibration is verified.

Key words: spectrometer; nonlinear; interference fringes; spectral calibration; single frequency laser