彩色布面上浅灰指纹拍摄1例

1案情简介2004年4月泰兴市发生一起拦路强奸案件,1名犯罪嫌疑人尾随一下夜班回家的女工,并将其强奸。图4正交偏振光+红色分色配光方法简图4讨论(1)纺织品上的指纹拍摄时,由于布纹条的存在,使得指印纹线断断续续,更由于纺织品纤维的圆柱形表面在入射光线照射下存在垂直方向上的纹路状分布的定向反射光,这些定向反射光一方面使背景反射亮度增加,另一方面其纹路状分布也起到一种背景干扰作用。这极大的干扰了指纹纹线的显现,所以,用普通光拍摄很难取得理想的效果。(2)在正交偏振光照相方法中,起偏镜使照明光线在入射平面上振动线偏振光,检偏镜…     

偏振光照相显现镜面客体上的潜在指印

目的研究镜面客体上潜在指印的偏振光照相显现方法。方法用偏振光照相分别对普通镜面和CD盘上的油脂指纹、灰尘指印进行显现。结果显现指纹清晰,通过与定向反射、暗视场照相方法进行比较,偏振光照相效果明显好于其他光学方法。结论偏振光照相可以有效地增加指印纹线与背景的亮度反差,消除物体背景干扰。     

全波段CCD物证检验系统在图像检验中的应用

1全波段CCD物证检验系统简介 特种照相作为现阶段用来提取现场潜在痕迹物证的重要手段，主要包括红外照相、紫外照相、发光照相和偏振光照相等，不同的方法需要用不同的器材来实现，这些器材包括多波段光源、紫外成像仪、红外成像仪、紫外光源、红外光源、偏振光摄影灯、各种波长的滤光镜等，器材繁多，操作繁琐。     

RGB通道与分色照相法结合分离图像背景

目的减弱或消除分色照相法分离不彻底的图像背景。方法RGB通道与分色照相法结合来改进分离图像背景的效果。结果图像的背景得到进一步消除。结论分色照相法与RGB通道结合背景分离效果有明显改进。     

暗视场照明与分色照相配合显现指印

目的研究彩色光滑客体上指印的显现方法。方法用暗视场照明和分色照相配合的方法对4种彩色木板上指印进行了显现。结果实验结果表明了暗视场照明和分色照相方法能够有效显现出彩色光滑客体上的潜在指印。结论拓宽了暗视场照明显现指印的范围,同时为彩色光滑客体上指印的显现提供了一种新的方法。     

Photozoom清晰放大刑事数码图像

数码摄影已逐渐成为刑事摄影的主流。然而，在电脑上使用Photoshop软件放大处理用数码相机拍摄的较小物证或者局部放大数码图片时就会出现影像放的越大清晰度越下降的情况，放大一定程度以后就会出现马赛克现象。这是因为数码信息处理技术原理的原因：利用数码相机拍摄的照片以及扫描仪扫描获得的图片都属于电脑图像中的点阵图，点阵图的影像是由若干个点（像素）以矩阵排列组成，一幅数码图片会完整的记述整幅图片的每个像素的信息。图片在放大后，整个图片像素量就会比原有图片像素增多，新图像上的每个像素是通过对原有图像对应像素按照某种数值运算方法进行插值得到的。而运用的计算方法不同，图片拉大后的效果也不同。现在，专业放大图片软件Photozoom软件提供了最近逼近法、     

高速瞬间摄影在物证检验中的应用实验

目的采用声、光、电瞬间感应触发的高速闪光成像装置,以普通数码相机拍摄物证瞬间变化形态,提高物证检验的有效性、客观性;方法研制专用摄影装置,包括触发装置、延时器和超高速闪光灯等组件。进行物证瞬间状态摄影实验,研究运动物体瞬间形态的拍照技术方法;结果本实验装置原理简单、有效。最高记录瞬间成像速度小于0.5μm。可以用于常规物证瞬间变化的成像摄影记录。     

刑事数码照相设备配备原则

数码相机及彩色打印机在技术上的突飞猛进使传统的摄影技术发生了里程碑式的变化,结合刑事照相专业的特点,就如何建立一个适应新形式工作下的“电子暗室”提出以下建议。“电子暗室”主要由两部分组成:硬件和软件。数码相机、照片打印机及计算机是硬件部分,最好还应包括一台平板扫描仪和底片扫描仪;软件应选择那些既简单易用又功能强大、能进行数字照片的编辑处理管理、检索的应用软件。1数码相机数码相机应选择拍摄速度好、能使用闪光灯、可更换镜头、动静皆能拍摄的数码相机。目前,数码相机按图像传感器种类的不同可分为阵列CCD数码相机…     

浅谈数码相机在刑事照相中的运用

１数码相机的特点数码相机不同于传统的相机,它不用感光胶片记录光学影像,而是运用数字技术将光学影像转换成磁信号记录在影像存贮器磁盘上,它的主要特点是：（１）影像的再现和复制无需暗房和化学冲洗加工,不受场所、温度、时间、以及药品的影响,数码相机较传统摄影更有利于环境的保护。（２）拍摄后可立即看到摄影的效果（通过机置的液晶显示器或相连的计算机显示屏观察）。（３）影像的存贮器可反复使用,不需要的或没有拍好的影像可随时消去;存贮的影像可转移到计算机硬盘、软盘或光盘上保存,相机存贮器可反复重新使用。（４）拍…     

紫外荧光拍摄纺织品上的消褪印章

1987年5月10日,某省博物馆保卫科送来一块有淡红色印章的淡黄色绸布,要求辨认印章内容。由于此物存放年代较长,绸布陈旧,印章颜色消褪,字迹模糊,无法辨认。用反差较大的12°缩微全色胶片进行了可见光分色照相,效果不理想,后采用紫外荧光照相获得了较好的效果。     

HDR技术在现场摄影中的应用研究

运用HDR技术可以获得被拍景物从最亮区域到最暗区域更多的细节。在现场摄影中运用HDR技术能够使现场照片和部分物证获得比通常的数字成像技术或摄影方法更大的动态范围,从而更好地再现高光或阴影部分的细节,获得更多的影像信息。     

A More Efficient Method for Synthetic Textile Fiber Analysis Using Polarized Light Microscopy

The efficiency of conventional polarized light microscopy (PLM) methods for analyzing synthetic fiber evidence analyses is improved. Historically, using PLM for fiber identification relied on measuring refractive index. This prior PLM technology is reliable, but it is not efficient. Most fibers are optically anisotropic, having two principal refractive index values, N_(High) and N_(Low). When the fiber is mounted in intermediate refractive index medium, efficiency is improved by observing the change in contrast while the polarized light’s vector is rotated relative to the fiber’s axis. Minimum contrast occurs when the refractive indices of the mounting medium and fiber are equal. This angle of equality is determined by orienting the fiber’s highest refractive index parallel to the polarized light’s electric field vector, rotating the fiber or polarizing element, observing minimum contrast and measuring the angle of equality. This method is rapid, reduces remounting fibers in different mounting media and provides a quantitative measure for fiber comparisons.     

Statistical Evaluation of Alternative Light Sources for Bloodstain Photography

Bloodstain photography is important in forensic applications, especially for bloodstain pattern analysis. This study compares the enhancement effect of bloodstain photography using three different types of light source: fluorescent white light, near‐ultraviolet (UV) light‐emitting diode (LED) light, and 410 nm LED light. Randomized complete block designs were implemented to identify the lighting that would statistically produce the best enhancement results for bloodstains on different types of surfaces. Bloodstain samples were prepared on white cotton, brown carpet, tar road, and wood. These samples were photographed in darkroom conditions using a Canon EOS 50D digital SLR camera, with Canon EFS 60 mm f/2.8 Macro USM lens. Two‐way analysis of variance and Fisher's least significant difference test were used to analyze the contrast of the images. The statistical analysis showed that 410 nm light is the best among the tested lights for enhancing bloodstains on the tested surfaces, where the contrast of bloodstain to background was the highest.     

Passport examination by polarized infrared spectra

In this study, a new nondestructive technique for passport examination is proposed. In this technique, linearly polarized light is used to measure Fourier transform infrared (FT-IR) reflectance spectra of films on the biographical data page. Thirty genuine and thirty-five counterfeit Japanese passports and five marketed films pasted on name cards were examined. The measured spectra were analyzed as follows. The absorption spectra were obtained by the Kramers-Kronig transformations of reflectance spectra. The peak ratios were then calculated from the absorption spectra by adding the peak areas at 1126 and 1263 cm(-1) and dividing the result by the peak area at 1727 cm(-1). When nonpolarized light was used, the samples could not be distinguished by comparing the peak ratios. However, when polarized light was used, they were successfully distinguished by the comparison. Therefore, polarized light is useful for the forensic discrimination of passport films by the measurement of FT-IR spectra.     

短波紫外反射照相显现胶带粘面潜在指印

目的研究胶带粘面上指印的提取方法。方法用短波紫外照相的方法对各种胶带粘面的指印进行拍照提取。结果从理论上解释了短波紫外照相拍照提取胶带粘面上指印的原理,从实践上为短波紫外照相法提取胶带粘面上指印提供技术方法和技巧。结论为胶带粘面指印的提取提供了一种新的方法。     

Automated Mapping of Explosives Particles in Composition C‐4 Fingerprints*†‡

Abstract: A method is described to perform automated mapping of hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX) particles in C‐4 fingerprints. The method employs polarized light microscopy and image analysis to map the entire fingerprint and the distribution of RDX particles. This method can be used to evaluate a large number of fingerprints to aid in the development of threat libraries that can be used to determine performance requirements of explosive trace detectors. A series of 50 C‐4 fingerprints were characterized, and results show that the number of particles varies significantly from print to print, and within a print. The particle size distributions can be used to estimate the mass of RDX in the fingerprint. These estimates were found to be within ±26% relative of the results obtained from dissolution gas chromatography/μ‐electron capture detection for four of six prints, which is quite encouraging for a particle counting approach. By evaluating the average mass and frequency of particles with respect to size for this series of fingerprints, we conclude that particles 10–20 μm in diameter could be targeted to improve detection of traces of C‐4 explosives.     

A Novel Approach to the Examination of Soil Evidence: Mineral Identification Using Infrared Microprobe Analysis*

Abstract: Identification of minerals using the infrared microprobe with a diamond internal reflection objective is a rapid and reliable method for forensic soil examinations. Ninety‐six mineral varieties were analyzed, and 77 were differentiated by their attenuated total reflection (ATR) spectra. Mineral grains may be mounted in oil for conventional polarized light microscope characterization and their ATR spectrum obtained with little or no interference by the liquid. This infrared microprobe method can be used to identify silicates, phosphates, nitrates, carbonates, and other covalent minerals; however, ionic minerals, metal oxide and sulfide minerals, and minerals with refractive indexes greater than diamond do not produce identifiable spectra, but the lack of a spectrum or one with high absorbance values does provide useful information. This research demonstrates the overall utility that infrared microprobe analysis brings mineral identification in soil evidence.