High-resolution and high-speed rotary Fourier transform spectrometer

Abstract

Rotary Fourier Transform Spectrometer (RFTS) contains a rotary refractor, which produces continuous variational optical path difference (OPD). This specialty makes RFTS suitable to high speed spectrum measuring. Maximal OPD can increase so easily through increasing maximal sampling angle from which the system can get high resolution reconstructed spectrum also. Depending on rotating refractor to produce OPD brings some important advantages such as good immunity to outside influences, light weight, small size, etc. The basic theory of this new kind of spectrogram measuring instrument is introduced. OPD is the most important aspect to be considered in studying or designing a Fourier Transform spectrometer(FTS) system. OPD formulas of RFTS are deduced. RFTS has nonlinearity of OPD, which brings interferogram periodicity drifting and reconstructed spectrum noise. The index of OPD nonlinearity is defined and important aspects of nonlinearity are analyzed, including relationships with the refractor's refractive index and the rotating angle. Replacing OPD in Fourier Transform with nonlinear OPD of RFTS can buck the error of nonlinear OPD in reconstructed spectrum, and computer simulation shows the method effective.