光谱成像和传统光学方法增强光滑纸张上血指印的比较研究

摘要

目的：研究光谱成像和传统光学方法增强光滑纸张上（有复杂背景干扰的）血指印效果，比较这些方法的实际效果和消除背景的规律性及特点，便于有选择性的拍摄利用。方法利用可见光定向反射（小偏角）配光照明方法照相；利用多光谱成像仪中的420~720 nm波段进行可见光多光谱成像方法照相，并进行影像分类和去混合处理；利用全波段CCD系统进行降温降噪恒温锁定、暗视场配光照明、254 nm短波紫外反射照相，分别对21种光滑纸张上的血指印样本进行拍摄采集。结果得到了21种光滑纸张上的血指印不同程度的显现效果，其中利用可见光定向反射（小偏角）配光照明方法照相、可见光多光谱成像方法照相以及暗视场配光照明、254 nm短波紫外反射照相，消除21种血指印背景干扰后，使影像效果明显改善的分别约占19%、33%和66%。结论利用不同光谱拍摄光滑纸张上（背景干扰状况下）的血指印，能各自消除某些特定背景干扰状况，能使得影像效果得到较好的改善，利用不同光谱拍摄光滑纸张上（背景干扰状况）的血指印具有各自的优缺点，可根据消除各种血指印背景干扰的实际效果来选择相应的光谱拍摄。%ABSTRACT:ObjectiveTo compare the effects of spectral imaging and traditional optical methods for blood ifngerprints on glossy paper with complex background and the regularity and characteristics of eliminating background, for the purpose of selection the most optimal photographical method.MethodsThree methods were employed to take photo of blood ifngerprint samples on 21 different kinds of glossy paper separately: the optical directional relfection at small angle with light illumination for photography; the visible spectrum imaging at 420~720 nm band of the Multiple Spectral Imager, classifying images and ifltering the mixed; the full-wave band CCD system for the constant temperature locking by reducing temperature and ifltering noise, illuminating with light in the dark ifeld, and the relfex photography by 254 nm short-wave ultraviolet band.Results Different images of blood ifngerprints on 21 kinds of glossy paper had been taken, among which, the image effects were obviously improved by light illumination method at 19%, Multiple Spectral Imager at 33% and full-wave band CCD system at 66% respectively after eliminating blood fingerprint background interference.ConclusionsDifferent imaging methods by multiple spectra for blood fingerprints on different glossy paper could eliminate the interference under some specific background, and to improve the imaging effects. It is suggested to select the right photographic method by the corresponding spectrum according to the real effect of eliminating interference from the background of the blood ifngerprints.