The Research Of Multi-spectrum Video And Measuring Fingerprint Technique

During the course of clearing up many serious criminal cases, to obtain fingerprints is among the most vital steps. Sometimes fingerprint traces turn to be linchpins of breaking criminal cases. To obtain fingerprints accurately and effectively is even more helpful to make the case clear. In order to improve the present insufficient measuring means, we cooperate with the Provincial Police Authority and Xingbo Digital Company in developing a video multi-spectrum measuring system for checking traces. Instead of using the traditionally used measurement executed by human beings, this study adopts a device system combined of videos and monitors, together with fluorescence powder. This new approach aims at eliminating subjective errors to the uttermost as well as lessening labors strength so as to enhance work efficiency.This paper particularly explains the excitation mechanism for photoexcitation material and analyzes internal and external reasons of emitting fluorescence, the relationship between emitting and changing of fluorescence and lattice structure. The paper also analyzes the reasons of ions polarization and lattice structure's influence on fluorescent intensity. Besides, the paper discusses electron jump law during the course of emitting fluorescence, fluorescence life, quantum efficiency and the relationship between the fluorescent emission spectrums and transmission spectrums. The paper provides, at the same time, a theoretic basis for using fluorescent powder when checking traces by using multi-spectrum measuring system.If light sources are different, fingerprints are revealed in the same way. Likewise, beam's angles different, fingerprints not the same way either. This paper makes relevant analysis and comparison on the above-mentioned facts and provides sufficient experimental argumentations on whether to use filters and whatfilters to be used. The paper makes analysis and comparison on the sensitivity of varied fingerprints to fluorescent powder. The paper also analyzes the degrees of clarity of the fingerprints revealed.The experimentation provides a theoretic basis for devising the system and using it:1. The angles of light source or measuring lens can be adjusted. It can be adjusted to the most suitable angle to take pictures. Reflex spots of light source cannot affect fingerprints to appear.2. The best filters are selected to match for fluorescent powder in varied condition. After the comparison, a better reference can be provided. This way can reduce troubles and ease off work intensity.3. When the device comes out, its weight shall not be too heavy so that it can be carried conveniently.