Research On Imaging Spectrometer For Evidence Identification

Imaging spectrometer is a novel optical remote instrument, which can acquiretwo-dimensional spatial and one-dimensional spectral information simultaneously. It hasbecome the research focus of many field, such as forensic science, target detection formilitary and homeland defense/security purposes, biological threat detection, and so on.Spectral imaging technique for the evidence identification is studied in this paper. Amulti-spectral imaging spectrometer with narrow band filters and the large aperture staticinterference imaging spectrometer are designed and developed. A novel type ofrotating-beam-splitter interferometer which has no tilt and shearing problems is developed. This paperincludes the following aspects:Based on the narrow-band filter spectral imaging technology principle, a multi-spectralimaging spectrometer which works in the UV band is built and developed. This system usesa continuous source of deuterium lamp UV illumination. For reducing the volume of thefilter size and instrumentation,20narrow-band filters is placed close to the detectorposition in this system. The detector is placed on a platform which can move along theoptical axis of the system, which can adapt the variation of image plane position caused bythe aberration of imaging lens and filters. By detecting a sample, a satisfactory result isgiven by this system. In UV region, the fluorescent effect of body fat is found on the multi-spectral images obtained by the multi-spectral imaging spectrometer, which is the firstdiscovery in the evidence identification field.A large aperture static infrared Fourier transform interference imaging spectrometer isdeveloped in this paper, whose rear objective lens is replaced by the all-reflected Offnersystem. The all-reflected Offner system can eliminate the aberration caused by this lens. Anew method of correction of imaging interferogram is proposed and used in this system.Using this system, the handwriting on a paper is detected, whose spectral cube is obtainedby the infrared Fourier transform imaging spectrometer. The results show that it can be usedfor evidence identification perfectly.For overcoming the disadvantage of the weak sensivity of the the narrow-band filterspectral imaging spectrometer, a large aperture static UV Fourier transform interferenceimaging spectrometer is developed. The improved Cassegrain objective lens is desiged. Thedispersion characteristics of beam splitter and the phase error of imaging interferogram areanalyzed. The fingerprint on a paper is detected, whose spectral cube is obtained by the UV Fourier transform imaging spectrometer. The satisfied results are given by this UV Fouriertransform imaging spectrometer.A novel type of rotating-beam-splitter interferometer which has no tilt and shearingproblems is developed. Its principle is analyzed, and its properties are discussed. Theequivalent model of rotary interferometer is given. Moreover, the preliminary experimentalresults are shown. This interferometer can be used as a Fourier transform spectrometerbecause it has the merits of high stability, small driving force, easy assemblage andadjustment, etc.