A Near-Infrared Micro-Spectrometer Based on Integrated Scanning
Grating Mirror and Improved Asymmetric C-T Structure
XIE Ying-ke1, 2, WANG Xi-chen2, LIANG Heng-heng2, WEN Quan3
1. School of Physical and Technology, Southwest University, Chongqing 400715, China
2. College of Science, Chongqing University of Technology, Chongqing 400054, China
3. Key Laboratory of Optoelectronic Technology and System of Education Ministry, Chongqing University, Chongqing 400030, China
Abstract：NIR spectrometer has been widely used in many fields such as aerospace, biomedicine, environmental testing, food safety etc. High performance, miniaturization, and low-cost are the main bottlenecks of developing micro-detection equipment based on near-infrared (NIR) continuous spectrum analysis, which is the leading research direction of the spectrometer. This paper proposes a miniature NIR spectrometer system structure based on micro-optical electro-mechanical system (MOEMS) integrated scanning grating micromirror and improved asymmetric Czerny-Turner(C-T) optical structure, analyzes the working principle of the spectrometer system and integrated scanning grating micromirror, and determines the maximum scanning angle of the integrated scanning grating micromirror based on grating-related parameters and spectrometer performance index requirements. The aberration of the improved asymmetric C-T initial optical structure is analyzed, the simulation and optimization design of the spectrometer optical system is completed based on the ZEMAX optical design platform, and the system’s key parameters are determined. The influence of the plano-convex cylindrical lens on the performance parameters, such as resolution and detection sensitivity of the improved asymmetric C-T optical structure system, was simulated and analyzed. Based on the simulation and optimization results, the mechanical structure design, processing and mounting of the miniature NIR spectrometer were completed, and the experimental platform was built to complete the testing of the relevant performance parameters of the spectrometer. The results show that the miniature NIR spectrometer based on MOEMS integrated scanning grating micro-mirror and improved asymmetric C-T optical structure was designed. This paper uses the MOEMS integrated scanning grating micro-mirror with the resonance frequency of 677.1 Hz developed by Chongqing University to realize simultaneous scanning and spectroscopy and can complete a wavelength range of 800~1 800 nm in 0.8 ms. The spectral accuracy is not significantly different from that of foreign brand spectrometers, the overall spectral resolution (FWHM) is ≤11 nm, and the wavelength stability is ≤±1 nm. The optical structure design based on the plano-convex lens can increase the detection output light intensity value by more than 15%, effectively improving spectral measurement sensitivity. At the same time, the spot size is smaller after the second focus of the plano-convex lens so that the single tube detector with a small sensing area and large frequency can be used to achieve spectral detection, which can reduce the system costs, suppress external optical noise, and meet the scanning grating type spectrometers with high scanning frequency. It can reduce system cost, suppress external optical noise, and meet the demand for spectral resolution of scanning grating spectrometer with high scanning frequency. Therefore, the NIR spectrometer based on MOEMS integrated scanning grating micromirror and improved asymmetric C-T structure proposed in this paper meet the development needs of high-performance, miniaturization and low-cost spectrometer.
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