金属腐蚀方法提高刑事物证显微摄影质量的研究

目的通过对金属承痕客体表面使用腐蚀液进行处理,以提高其在常用的可见光源环境中的成像质量。方法对铝及铅板表面形成的线条及凹陷状痕迹,使用不同光源时光学显微镜下的成像特点进行研究,对高倍率下影响成像效果的色散现象进行分析。使用无水乙醇与50%(质量分数)丙酮的混合溶液对金属表面的痕迹进行前处理,对其成像质量进行检验,并讨论引起变化的原因。结果金属客体表面线条状痕迹中存在的微小线条会引起照明光的干涉现象,在显微拍照过程中能形成不同颜色的明暗条纹,极大地影响观察拍照质量。使用腐蚀液对金属客体表面痕迹进行腐蚀,可增大纳米尺度塑性变形部位的几何尺寸,改善显微镜的拍摄质量。结论使用特殊的腐蚀液对金属客体表面痕迹进行适当处理,可消除金属承痕客体在光学成像系统中干涉现象的发生,用此方法对金属表面痕迹进行前处理,可得到一种显微摄影条件下提高微小痕迹成像质量的方法。

Improving Imaging Quality of Criminal Photography Photomicrograph by Corrosion of Metals

Objective Aimed to improved the image quality of criminal photography use a new surface treatment technology on the trace. Methods The imaging characteristics of traces with shapes of line and concave formed on the surface of Al and Pb boards were investigated by an optical microscope with different light sources. The dispersion phenomena under high magnification were analyzed in order to validate their effects on the image quality. After pre-processing by an etching solution, the change of image quality on different traces was tested and discussed. Results The results indicated that the tiny lines in the traces on the metal surface could lead to optical interference, which resulted in the formation of light and dark stripes with different colors in the optical microscope photomicrograph. Conclusions The interference could extremely affect the image quality. Using etching solution to corrode traces on metal surface could enlarge the size of plastic deformation in a nano-scale. The effect of interference was eliminated and the quality of photomicrograph was improved.