Study On Some Key Technologies Of Portable Raman Spectrometer

Raman spectroscopy is moving from laboratory researches to many practicalapplications, such as food safety test, security inspection, custom and environmentalmonitoring. The development of portable Raman spectrometer makes Raman spectroscopyapplied more widely and used more conveniently. However, the further promotion of theportable Raman spectrometer in China is greatly limited, because most of the domesticmarket is controlled by foreign manufacturers. This paper analyzed the key problemswhich will affect the performances of portable Raman spectrometer, discussed somecritical technologies of portable Raman spectrometer, and focused on the solution to CCDcooling method and Raman fiber probe design to provide the technological basis for theindependent production of high-performance portable Raman spectrometer.In this paper, the thermoelectric CCD cooling technology for reducing dark currentnoise was studied. And in order to solve the water-condensation problems in CCD cooling,a drying method based on the theory of dewfall condition was proposed. The relativehumidity inside the CCD chamber is controlled below0.1%by using silica gel desiccant.The alarm system for preventing water-condensation was implemented using a humiditysensor and a condensation sensor, which can monitor the chamber humidity in real timeand trigger the alarm quickly once water-condensation occurred on the CCD surface. Thethermoelectric cooling system in this paper can realize the cooling temperature differenceover40℃, and can prevent condensation and frosting on-20℃.For the convenience of in-situ application of portable Raman spectrometer, anintegrated Raman fiber probe with separate excitation and collection optical structure wasdesigned and implemented. After careful mounting and adjustment, the probe was testedand its performance was verified. Through the test of Rhodamine B fluorescence andRaman intensity, it’s shown that the light collection efficiency of this fiber probe is betterthan that of the small mirror structure. Using the home-made Raman fiber probe, two kindsof illegal food additives (SudanⅠand Rhodamine B) were tested. The results demonstrated that the portable Raman spectrometer could effectively suppress Rayleigh scattering andimprove Raman signal.