11 October 2010 Application of ZOOM-FFT for scanning-type spectrometer based on digital signal processor
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Abstract
The Fourier transform spectrometer is based on a scanning-type Michelson interferometer with two optical-beams including reference laser and measurement light. The optical spectrum of measurement light can be obtained by colleting the analog signal of measurement light with the sampling time-scale based on interference fringes pulse of reference laser. The optical interferogram signal of the reference laser is converted to pulse signal, and it is subdivided into 16 times. So the sampling rate is constant only depending on frequency of reference laser and irrelative to the scanning-motor velocity. This means the sampling rate of measurement channel signal is on a uniform time-scale. In order to get optical spectrum, the analog signal of measurement channel should be collected and Fourier-transformed. Digital Signal Processor (DSP) TMS320-F2812 is used. Its internal 12-bit Analog-to-Digital Converter (ADC) for measurement channel is triggered by the 16-times pulse signal of reference laser. The DSP is used to process optical interferogram signal with ADC sampling rate up to about 1.5MHz. The optical spectrum of measurement channel signal is processed with 1024 points-Fast Fourier Transform (FFT) method. Then, the ZOOM-FFT is adopted. By digital frequency-shift conversion and low-pass filter, these digital signals are processed with 1024 points-FFT once again to improve the frequency measurement resolution. Finally, the optical spectrum of measurement channel will be displayed on LCD with high frequency-resolution.
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Peng Xu, Peng Xu, Yue-xiang Peng, Yue-xiang Peng, Li-qiang Wang, Li-qiang Wang, Hua Kang, Hua Kang, } "Application of ZOOM-FFT for scanning-type spectrometer based on digital signal processor", Proc. SPIE 7656, 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment, 76563B (11 October 2010); doi: 10.1117/12.865576; https://doi.org/10.1117/12.865576
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