Study Of Fluorescence Lifetime Optical Fiber Thermometry System And Signal Processing

The temperature is one of the most important parameters in the measurement science and industrial process control. It is difficult to measure temperature in some special situations in the special fields. In particular, the requirement to measure temperature in inaccessible or difficult circumstances, such as those in RF radiation, or other noisy electromagnetic environments, the optical sensor has been the imperatives in the development of optical sensors for this purpose. The optical fiber fluorescence temperature sensing system is a preceding problem in this research area. The virtues of the fluorescence optical fiber temperature sensor are electromagnetic interference resisting,little bulk,low transmission loss, corrosion resisting. More and more attention is paid on the fluorescence optical fiber temperature sensor.In this paper, the luminescence theory of fluorescence material is discussed based on photoluminescence. Several common fluorescent materials and their temperature characters are introduced. The basic principle and characteristic of fluorescence measurement methods of temperature are discussed. The characteristics of the excitation light source and the part of optical signal transmission including the coupling between light source and optical fiber, optical fiber and sensitive part, optical fiber and optical detector are analyzed.The basic principle of the fluorescence lifetime is introduced, and the pulse and phase detection methods of the fluorescence lifetime are researched. In this paper, phase-locked loop is used to detect the phase of the fluorescence to get the fluorescence lifetime. The method for the detection of fluorescence lifetime that uses the technology of the phase-locked loop is mainly proposed. The basic principle and structure and the mathematics model of the phase-locked loop are researched in detail.The fluorescence temperature measurement system with the phase-locked loop technology as the core including hardware and software parts is designed in this paper. According to the interesting temperature measurement range of 273~423 K, the proper sensitive material is selected and accordingly the light source is selected. The detect part of this sensor system with high collect efficiency is designed. The detector, amplifier circuit, filter circuit and the phase-locked loop circuit are analyzed and designed in detail. The singlechip of MSP430 is used in this system to process the signal and detect the fluorescence lifetime, calculate the temperature and display the temperature.In this paper, the absorb spectrum of the LED is tested. The error of the system is analyzed. The experiment of the relation of the temperature and the lifetime of the ruby crystal is conducted, and the high accuracy and resolution are obtained.