硅藻土基有色粉末显现复杂背景上潜指纹的图像增强分析

Image Enhancement Analysis of Fingerprints on Complex Backgrounds Developed by Diatomaceous Earth-Based Colored Powders

在法庭科学领域,指纹鉴定是一种身份认定的可靠方法,复杂背景上潜指纹的显现和图像增强尤为重要。本研究使用硅藻土基有色粉末显现复杂背景上的潜指纹,并开展显现后的图像增强分析。采用酸洗和热处理后的硅藻土作为基质材料,扫描电子显微镜观察到硅藻土颗粒呈半径15μm的圆盘状,氮气吸附脱附测试表明,硅藻土的BET比表面积为38.7 m^2/g,孔径集中在4.5 nm,累计孔体积为0.067 cm^3/g;然后利用物理吸附原理将有机染料与硅藻土复合,选取的染料是在分子结构上相似但颜色差异较大的孔雀石绿和结晶紫,根据紫外可见光谱拟合出的回归直线方程分别为y=0.1336x-0.01304(R^2=0. 99945)和y=0. 1136x-0.00400(R^2=0.99939),得到硅藻土对两种染料的吸附容量分别为0.60和0.62 mg/g,基于此制备出孔雀石绿-硅藻土粉末和结晶紫-硅藻土粉末。以食品包装盒和饮料标签作为具有复杂背景的客体,使用制备的硅藻土基有色粉末显现这类客体表面的潜指纹,分别借助Photoshop和Image J图像处理软件进行RGB图像通道分离和灰度统计分析,从定性和定量两个层面分析了图像增强效果。研究结果表明,硅藻土基有色粉末结合图像处理软件,能够有效滤除复杂背景干扰,得到清晰的指纹图像。

Fingerprint identification is one of the most reliable methods to identify cognizance in the field of forensic science.It is particular important to investigate the development and enhancement of latent fingerprints on complex backgrounds.In this study,diatomaceous earth-based colored powders were used to develop latent fingerprints on complex backgrounds and image enhancement analyses were performed after development process.Diatomaceous earth after pickling and heat treatment was used as the matrix material.The particle morphology exhibited disc shape with a radius of about 15μm.Nitrogen adsorption-desorption measurement showed that diatomaceous earth had a BET surface area of 38.7 m^2/g,a narrow pore-size distribution centered at 4.5 nm,and a cumulative volume of 0.067 cm^3/g.Organic dyes were incorporated into diatomaceous earth based on physical adsorption.Malachite green and crystal violet were chosen because of the similarity in molecular structure but the difference in color.According to the UV-Vis spectra,the standard curves of malachite green and crystal violet were y=0.1336x-0.01304(R^2=0.99945)and y=0.1136x-0.00400(R^2=0.99939)respectively.The adsorption capacity of diatomaceous earth to malachite green and crystal violet was 0.60 and 0.62 mg/g,respectively,and on the basis of this,the diatomaceous earth-based colored powders were prepared.Latent fingerprints on complex backgrounds including food packaging and beverage label were developed by the as-prepared powders.To qualitatively and quantitatively analyze the effect of image enhancement,R,G and B channels in RGB color images of fingerprints captured by a digital camera were extracted by Photoshop,and gray analysis was performed by Image J.The results indicated that the combination of diatomaceous earth-based colored powders and image processing software could effectively avoid background interference and eventually achieve clear fingerprint images.