运用紫外线摄影技术鉴定字迹与盖章的先后顺序

近年来，运用紫外反射摄影这一技术，对痕迹物品的拍摄研究取得了较大的进展，并已在司法鉴定的物证拍摄中广泛运用。利用紫外线进行拍摄，根据照相机镜头和摄影感光材料在紫外线区域的敏感程度进行划分为：长波紫外线摄影区域，波长为３２０～４００nm，峰值为３６５nm；短波紫外线摄影区域，波长为３２０～２００nm，峰值为２５４nm。紫外线摄影的主要作用是将肉眼看不清或看不见的一些痕迹物品加以显现，从而达到能进行物证鉴定的目的。笔者在长期的教学和检案中，运用这一技术对文件、图表、票据等上的字迹与盖章的先后顺序进行检验，取…     

提高现场指纹查询破案的技巧

我市的指纹自动识别系统自建成以来 ,查破了一大批刑事案件 ,实践证明 :只有灵活掌握和运用查询技巧 ,才能充分发挥指纹自动识别系统的破案功能。笔者仅就 5个方面谈一下掌握和运用查询技巧的做法和体会。1　认真分析现场指纹 ,把好编辑关对每枚现场指纹都要认真分析每个细节特征点 ,并根据现场指纹图像的强弱反差调整扫描仪的设置 ,使存储到机器中的指纹图像达到最佳效果。也有些现场指纹多次扫描后效果仍然不佳 ,这需要我们对现场指纹细节特征进行标画时 ,不要单独的对机器内的现场指纹细节特征进行标画 ,而是要结合实物或照片进行标画 ,…     

泰科视频监控新技术亮点纷呈

<正>高清监控更应提升影像画质对于视频监控而言,图像清晰度无疑是关键,图像越清晰,细节越明显,智能应用的准确度也越高。但是,片面追求高像素并无意义,因为图像质量并不仅仅取决于像素点,还取决于图像处理技术。泰科集成安防的视频监控解决方案,除了通过采用更高分辨率的摄像机覆盖相同的区域,来获得更高的像素密度和更大视野,还采用多种先进的影像提升技术提高产品差异化和性能:宽动态:使摄像机在光源对比明显的场景,捕捉更多画面细节,     

多传感器视频集成技术及应用浅析

多传感器弥补了纯视频监控的不足，对多个环境量进行跟踪，能够实现对目标区域的多方位立体监控；同时，运用多传感器信息整合技术，系统能够有效提高对检测区域或目标报警、智能分析、智能跟踪的准确度，此外，大规模的传感器集成系统能够获得比单个或少量传感器集成系统更多信息，对这些大数据进行有效的综合应用，能够实现更加复杂和高阶的功能，产生巨大的行业与社会价值。     

浅论刑侦摄影技术的运用技巧

刑侦摄影技术是刑事图像侦查工作的一项重要内容。侦查人员通过运用专业设备,能够准确客观地记录案发现场的实际情况,对于案件侦破工作具有十分重要的意义．与其他摄影方法不同,由于刑侦摄影的图像要用做刑事侦查工作的证据,因此刑侦摄影具有自身独特的规范要求和使用技巧。本文分析了刑侦摄影的几种主要形式和基本技术,就侦查人员如何更好地提高刑侦摄影技术运用能力进行了研究。     

数码相机在指纹自动识别系统中的运用

数码照相是通过数码相机将所拍景物、图像转换成数码信息进行计算机存储、加工处理和图像输出等一项专门的处理技术，是数码影像技术的具体运用。近几年，数码相机已经在刑事技术中得到了普及利用，它的运用与传统的摄影技术相比有着无法比拟的优越性，不仅减少了传统刑事照相中的冲洗等化学制作环节，避免了对社会环境的污染，提高了刑事照相的工作效率，而且可以即拍即看，拍摄后通过其液晶显示器预览影像效果，随机进行储存或删除，或方便灵活地对图像进行加工处理。由于它的这些优点，所以被广泛运用于刑事案件的现场照相、物证照相和辨…     

剪影

剪影，是从剪纸工艺中引申出来的一种艺术形式，通常是艺人照着模特的脸或人体的轮廓剪纸成形。摄影中的用光，有顺光、顶光、侧光和逆光，在逆光或光线较暗时拍出的照片，没有多少层次和细节，只有被拍之人物或物体的轮廓，有剪纸或版画的韵味。这种手法，往往被摄影人称为剪影并经常采用。     

刑侦光源

在刑事案件的侦破现场,无论是照明,还是寻找证据,都需要用到光源。多种现代化的光源在刑侦现场的应用,大大提升了破案效率,减少了寻找证据时对现场的破坏程度。在现场物证勘验中,各种痕迹物证的细节往往是很微弱的,在普通光照条件下,很难捕捉和记录到这些细节。由于物体本身对光的反射、吸收的特性不同,在一些特殊的可见或不见光源的照射下,物证的表面将得到不同的亮度分布,从而显示出不同的细节。     

运用数码摄像技术快速提取现场血脚印

在现场勘查工作中，快速提供现场痕迹物证照片，对案件的快速侦破是十分必要的。而传统的照相技术难以实现。现在，数码照相、摄像技术日趋完善，为现场照相拓展了空间，使快速提供现场图片材料成为可能。１器材SONYDSR－PL１００AP数码摄录像机；PANASONICNV－MPD１MU升华型彩色打印机；监视器（或电视机）；A／V连接电缆（或S视频电缆）；摄影灯（或现场勘查灯）。２操作过程调整摄像机的位置，使镜头轴线与脚印平面垂直；摄像机广角微距对焦；调整灯光角度、物距，使纹线最清晰时进行摄像。３照片打印用A／V连接电缆（S视…     

翻拍票据的技术要点

翻拍，是指利用相机对各种黑白、彩色照片、表格、文字材料等进行原比例或变比例（放大或缩小）的复制摄影技术。在我们的工作中，尤其是在检验鉴定和自侦案件中，经常运用这一技术对涉案的票据进行收集、固定和保全，为起诉、审判提供证据。涉案票据往往字迹（包括阿拉伯数字）较小，使用常规照相方法很难按原比例拍摄下来，而对一些因放置时间长等原因引起的票据字痕较轻或被修改、涂改、变造的票据，仅仅依靠复印机进行复印又不能反映犯罪的细节特征，揭露犯罪的本质。使用照相机对原物证进行翻拍能弥补这一缺憾，为侦查、起诉和审判提供…     

Latent evidence detection using a combination of near infrared and high dynamic range photography: an example using bloodstains

In this paper, we use bloodstains to illustrate an approach for identifying latent evidence on dark cloth using near infrared (NIR) photography combined with high dynamic range (HDR) photography techniques. NIR photography alone has been used to capture latent evidence that cannot be seen in normal ambient light. HDR techniques combine multiple bracketed photographs of the same image to increase the dynamic range of the photograph which can provide greater contrast. Using NIR photography alone, we were able to detect a bloodstain up to a 1/16 dilution, an improvement over previous studies. Combining NIR photography with the HDR process resulted in a noticeable increase in visibility up to 1/16 dilution when compared to NIR photographs alone. At 1/32 dilution, we were able to detect bloodstains that were not visible using NIR alone. NIR is a useful tool for imaging latent evidence, and combining NIR with HDR consistently provides better results over NIR alone.     

Development of a Dundee Ground Truth imaging protocol for recording indoor crime scenes to facilitate virtual reality reconstruction

Early and accurate visualisation of a crime scene is highly desirable such that a rapid, agile, and informed decision-making process can be undertaken by an investigative team. We present a new standard operating procedure for imaging an indoor scene using DSLR cameras conventionally used by crime scene investigators and examiners. The standard operating procedure (SOP) enables the systematic photography of indoor spaces in such a way that the Structure from Motion (SfM) photogrammetry technique can be implemented, allowing the scene to be recreated in Virtual Reality (VR). To demonstrate the method’s validity, we compare two VR-rendered representations of an example scene using (a) photographs taken by an experienced crime scene examiner using a conventional photographic method and (b) photographs taken by a novice photographer following the developed SOP.     

Detection of latent bloodstains beneath painted surfaces using reflected infrared photography

Bloodstain evidence is a highly valued form of physical evidence commonly found at scenes involving violent crimes. However, painting over bloodstains will often conceal this type of evidence. There is limited research in the scientific literature that describes methods of detecting painted-over bloodstains. This project employed a modified digital single-lens reflex camera to investigate the effectiveness of infrared (IR) photography in detecting latent bloodstain evidence beneath a layer or multiple layers of paint. A qualitative evaluation was completed by comparing images taken of a series of samples using both IR and standard (visible light) photography. Further quantitative image analysis was used to verify the findings. Results from this project indicate that bloodstain evidence can be detected beneath up to six layers of paint using reflected IR; however, the results vary depending on the characteristics of the paint. This technique provides crime scene specialists with a new field method to assist in locating, visualizing, and documenting painted-over bloodstain evidence.     

The Effects of High Dynamic Range on Fingerprint Images Processed by Photoshop

High dynamic range (HDR) imaging is a function that combines five images with different exposures into a single image. This technique may provide fine ridge details of fingerprint images for forensic latent fingerprint examination. Therefore, viewing fingerprints under optimal conditions is of paramount importance. This paper analyzes HDR and non‐HDR photos by using the Michelson contrast formula. The Michelson formula will provide a measurement to determine whether better contrast between the background and print can be achieved using the HDR function and if the background color affects the quality of the images. Two hypothesis were tested: (i) the HDR image provides more details of fingerprints with a better tone, greater clarity, and contrast than a normally exposed image regardless of the background color; (ii) the background color does not affect the quality of HDR fingerprint images overall, but the multi‐color background may increase the contrast of HDR fingerprint images in some cases.     

Visualization of Latent Blood Stains Using Visible Reflectance Hyperspectral Imaging and Chemometrics

The detection of latent traces is an important aspect of crime scene investigation. Blood stains on black backgrounds can be visualized using chemiluminescence, which is invasive and requires a darkened room, or near-infrared photography, for which investigators need to change filters manually to optimize contrast. We demonstrated the performance of visible reflectance hyperspectral imaging (400–720 nm) for this purpose. Several processing methods were evaluated: single wavelength bands, ratio images, principal component analysis (PCA), and “SIMPLe-to-use Interactive Self-modeling Mixture Analysis” (SIMPLISMA). Using these methods, we were able to enhance the contrast between blood stains and 12 different fabrics. On black cotton, blood dilutions were visible with a minimal concentration of 25% of whole blood. The hyperspectral camera system used in this study is portable and wireless, which makes it suitable for crime scene use. The described technique is noncontact and nondestructive, so all traces are preserved for further analysis.     

多源图像融合技术及其在公安刑事摄影工作中的应用

近年来,多源图像融合技术的应用越来越多,它可以将同一场景以不同成像方式或者不同成像时间获得的不同图像融合为一幅图像。这种技术可以综合多张照片的信息量,提高视觉感知,便于进行计算机的处理,因此,可在公安刑事摄影工作中用于对疑难指纹、立体痕迹、强反光客体痕迹、高逆光现场照片等的拍摄和处理,从而最大程度的准确反映被摄景物的实际情况。     

论交通事故证据的审查与采用

交通事故发生后,针对众多证据,除了依靠科学、合法的手段收集证据外,对于收集到的各类证据,就要从现场勘查图;现场照片;现场勘查笔录;对技术鉴定;驾驶员的分析和证人证言等多方面审查,只有这样才能使交通事故责任认定事实清楚、证据充分,才可以正确的处理交通事故     

闪光灯照相用于现场手印

对现场手印进行综合分析,结合勘查实践,对几类常见现场手印如何运用闪光灯照相提取进行了可行性探讨,具有实用性,可操作性.     

The Use of Near‐Infrared Photography to Image Fired Bullets and Cartridge Cases

An imaging technique that is capable of reducing glare, reflection, and shadows can greatly assist the process of toolmarks comparison. In this work, a camera with near‐infrared (near‐IR) photographic capabilities was fitted with an IR filter, mounted to a stereomicroscope, and used to capture images of toolmarks on fired bullets and cartridge cases. Fluorescent, white light‐emitting diode (LED), and halogen light sources were compared for use with the camera. Test‐fired bullets and cartridge cases from different makes and models of firearms were photographed under either near‐IR or visible light. With visual comparisons, near‐IR images and visible light images were comparable. The use of near‐IR photography did not reveal more details and could not effectively eliminate reflections and glare associated with visible light photography. Near‐IR photography showed little advantages in manual examination of fired evidence when it was compared with visible light (regular) photography.     

Multi-resolution image fusion technique and its application to forensic science

Image fusion is a process of combining two or more images into an image. It can extract features from source images, and provide more information than one image can. Multi-resolution analysis plays an important role in image processing, it provides a technique to decompose an image and extract information from coarse to fine scales. In some practical forensic examinations (such as the cartridge image check), we cannot obtain all information from just one image; on the contrary, we need information from images with difference light sources (or light ways). In this paper, we apply an image fusion method based on multi-resolution analysis to forensic science. Synthetic and real images (such as images from closed-up photography and flash photography) are used to show the capability of the multi-resolution image fusion technique.