Research On Ultraviolet Fourier Transform Imaging Spectrometer In Latent Target Detection

Latent target is a kind of invisible target on the object for examination, such as fingerprint, bodyfluid. With the advantages of fluorescence excitation and environmentaladaptability simultaneously, Ultraviolet Image Spectroscopy has shown irreplaceablefeatures in the field of latent target detection and become a current research focus. Theproblems of Ultraviolet Image Spectroscopy existed in the latent target detection field havebeen discussed in this paper. The theory and key techniques of applying Fourier transformImage Spectroscopy in such field were also studied. A design of Large Aperture UltravioletFourier Transform Imaging Spectrometer (LAUV-FTIS) based on image planeinterferometer and Offner system was first proposed in this paper. The prototype wasdiscussed and developed to demonstrate the research. The results in this paper not onlyprovide theoretical support for the related research work, but also made a useful explorationin engineering applications. The main work includes:(1) The problems of Ultraviolet image spectroscopy existed in the latent targetdetection field were analyzed. The feasibility of applying Fourier Transform ImageSpectroscopy in such field was also discussed. By studying the structures and performanceof Fourier transform imaging spectrometer (FTIS), the advantages of high light flux andstatic interference process which the time-spatial modulation structure has were pointed out.The overall performance was superior to the time modulation structure and the spatialmodulation structure for the particularity of working in the medium UV band (MUV) andnear UV band (NUV).(2) Two main kinds of the time-spatial modulation structures were introduced and theinterference process was analyzed. The non-simplified expression of Optical PathDifference (OPD) in Image Plane Interference Imaging Spectrometer (IPIIS) was first givenin this paper. The nonlinear residual of OPD both in Lateral Shear Interference ImagingSpectrometer (LSIIS) and IPIIS in different working modes were discussed. A new kind ofsingle-side defocus working mode in IPIIS, which has less nonlinear residual than thedouble-side defocus working mode currently used and helps to reduce spectralreconstruction error, was proposed based on the results aforementioned.(3) A design of large aperture Ultraviolet Fourier Transform Imaging Spectrometer(FTIS) based on image plane interferometer and Offner system was first proposed. The design of the optical system, mechanical system and electronic system were given and theprototype was developed successfully. The working waveband of the prototype is250nm~400nm and the interference pattern resolution is512pixels×512pixels. Thetheoretical minimum wavenumber resolution is81.3cm-1which is superior to that of theAOTF structure. For the first time the prototype collected raw interference pattern of latenttarget in solar blind UV band.(4) The data processing technology of time-spatial modulation FTIS in UV band hasbeen studied. Firstly, the scanning principle and process was analyzed and then thereconstruction, preprocessing and calibration of the raw interference pattern were discussedconsecutively. The spectral data cubes of the target in UV band were obtained finally. Thelatent fingerprint could be recognized clearly from the image slice which is capable to meetthe need of latent target detection. The spectral curve of the target could distinguish theemission peak at253.7nm and365nm when the low pressure and high pressure mercurylamp were used as the illuminator. Accurate spectral data of the target can be collected onthe short and long wave ends of the working band..