| 其他摘要 | With the features of rich information, strong analytical ability, fast processing speed, without sample pretreatment and easy to use, handheld Raman spectrometer is widely used in water pollution monitoring, drug smuggling, air quality monitoring, cultural identification, drug testing and other areas. The technology of handheld Raman spectrum is relatively mature abroad, and series of excellent products have been applied. In China, the domestic applications are still in its infancy. The key technology of handheld Raman spectrometer is hard to break is the main blocking reason.In this paper, basing on the current technical condition, two main parts of handheld Raman spectrometer, the optical system of Raman probe and the grating spectrometer, are studied. In terms of Raman probe, an optical system of handheld Raman probe with the total length of 15cm, small field of view and large object numerical aperture has been designed. The object numerical aperture of collecting system is 0.33 using spherical optical technology and 0.4 using non-spherical optical technology. The telephoto structure with the telephoto ratio of 0.59 has been used in converging system. Meanwhile, the further analysis of stray light in optical system of Raman probe has been investigated. By real ray tracing, a reasonable stray light analysis model has been established. Several technologies of eliminating the scattering stray light caused by the laser reflecting and scattering on lens surface have been proposed, such as the technology of notch filter, the technology of black spots, the technology of aperture matching and so on. Using the optical simulation software Tracepro, the opto-mechanical model of handheld Raman spectrometer has been simulated. The simulation result shows that stray light suppression level meets the Raman spectral measuring requirements while using the eliminating stray light technologies above. In terms of grating spectrometer, for coma-free Czerny-Turner structure，the formula of determining the structure by the image size has been proposed. Basing on this formula, the spectrometer with a high resolution of 0.6nm and satisfying application requirements of Raman spectroscopy has been designed. In astigmatism-free Czerny-Turner structure, the zero-order and first-order astigmatism-free conditions in crossed astigmatism-free structure have been derived, and the restricted conditions on system construction are presented. The correspondent crossed coma-free Czerny-Turner structure has also been built up for the comparison. It is shown in both of theoretical calculation and software simulation, that the astigmatism-free crossed C-T structure has a superior optical performance, with RMS of spot diagram only 12 % to 52 % of that in the correspondent coma-free Czerny-Turner structure at the working wavelength. The former is easy to obtain good optimized results. In order to improve design efficiency, and to make work more intelligent and reliable, the initial structure models of coma-free and astigmatism-free have also been established by GUI in Matlab to directly communicating with Zemax, which make it convenient by automatically input instead of manually input. Finally, we get the results of the spectral resolution better than 0.6nm and the Raman spectral range from 781nm to 1014nm, with the prototype size of 243mm×25mm×71mm. The five characteristic peaks of Raman spectrum of CCL4 have been successfully measured by the prototype of the Raman spectrometer, which verifies the feasibility and the rationality of the optical design of the whole Raman spectrometer system. These have established a good technical foundation of handheld Raman spectrometer for further development in reducing instrument size and improving excellent performance. |
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