Research On Detection And Processing Technology Of Weak Fluorescence Signal

Analytical method of weak fluorescence, with high sensitivity, is a new type of method for Spectrum-Chemical analysis. It is widely researched and applied in agriculture, industry, medicine, materials science, environmental science, information science and some other fields. Weak fluorescent signals generated by transmitter LED is very faint, which is easily submerged in noise. In order to detect and process the weak fluorescence signal, it is indispensable to design a special testing and processing system which is able to maximize the signal-to-noise ratio, achieve amplification, and extract the useful information from the faint signal or its variation. The research content of this paper, which is mainly for industrialization research of high efficiency ultra sensitive hidden explosives detector, is a part of the major national instrument industrialization project called "series of industrialization and the subsequent development of high efficiency ultra sensitive hidden explosives detector and multifunctional water quality monitor". The main content includes the follows:(1) A weak fluorescence signal detection system is designed in this paper. SiPM is finally selected as the core photoelectric device after comparing the properties of the common photo sensors. The structural characteristics and main influence factors of SiPM are studied and the high voltage bias circuit for SiPM and low noise preamplifier module are designed. This paper does the theory research on sampling integral method in weak signal detection, which is used in the system to design the sampling integral module.(2) The influence of temperature factors on the weak fluorescence detection system and the frequently used temperature compensation methods are researched to design a temperature compensation circuit where the SiPM’s gain is compensated by the bias. Based on the research about the temperature characteristics of fluorescent film, a compensation measures by curve fitting to real-time correct the sampling is provided.(3) In this paper, the digital signal processing technology about the weak fluorescence signal detection system is studied. This paper designs an FIR digital filter to filter out power frequency noise and the excitation light pulse frequency interference noise. At the same time, the sliding low-pass filter is designed to filter out parts of high-frequency noise in the processing system. Second, the fluorescence quenching the fluorescence explosive detection instrument information identification methods are studied, and several algorithms of fluorescence quenching reaction is proposed.(4) In this paper, performance test has been carried on the weak fluorescence signal detection and processing system. It tests the low noise preamplifier module and sampling integral. At the same time, function test has been taken on common explosives detection by this system.The research results of this thesis applied to the development and industrialization of hand-held fluorescence explosive detection instrument. At present, the hand-held fluorescence explosive detection instrument has been realized industrialization. After the strictly performance test and industrial test, this product has reached the industrial grade product standard. This product has been carried out field-testing in Xinjiang, Tibet, Africa and other places. It proves that the performance has reached the domestic advanced level.