Development Of The Near-infrared Line Spectrum Analyzer

Near infrared spectroscopy plays an important part in process control for its advantages such as simple structure, fast analysis speed, non-destructive detection, adaptation to almost all kinds of samples(fluid, dope, coating, powder, solid, etc.) and simultaneous detection of multiple components with multiple channels. To apply near infrared spectroscopy to quality analysis during traditional Chinese medicine manufacturing process is not only feasible but also very appropriate.In this thesis, the author comprehensively described the theory of Fourier transform spectrometer, which is one of the most common spectrometers. We set up the spectrometer system, realized the controlling of the stepping motor, designed the amplifying circuits, developed the software system of data acquisition and data processing based on Labview, did some preliminary experiments and made some analysis on the results. This thesis goes in five chapters as follows:Chapter 1: The background of carrying out this thesis. The features of near infrared spectroscopy and the prospect of applying it to manufacturing process of traditional Chinese medicine are analyzed. Several popular kinds of near infrared spectrometers are introduced and their advantages and disadvantages are discussed. Finally, the major objective and works are outlined.Chapter 2: The fundamental theoretics of Fourier transform spectrometer. First, the basic principle of Fourier transform spectroscopy is expounded. Then the influence of instrument line shape function on interferogram and the inhibition methods are analyzed. The factors that determine the spectral resolution of Fourier transform spectrometer and the methods of sampling the interferogram are discussed. The phase error and its correction are then introduced. Finally, the advantages of Fourier transform spectrometer over other types of spectrometers are demonstrated.Chapter 3: Design of the Fourier transform spectrometer. A design of Fourier transform near infrared spectrometer is proposed. Its components are expounded through three parts: light path, circuit and software. At last, the major system parameters are listed.Chapter 4: Building and test of Fourier transform near infrared spectrometer. According to the design shown in chapter 3, a simple Fourier transform near infrared spectrometer is built. Some preliminary experiments are made and the analysis of the results is given.Chapter 5: Conclusion and expectation. The conclusions of the thesis are made, and further improvements are also proposed.