Max Robinson

Line-scan imaging for the positive identification of ballistics specimens

The identification of firearms from forensic ballistics specimens is an exacting and intensive activity performed by specialists with extensive experience. The introduction of imaging technology to assist the identification process of firearms has enhanced the ability of forensic ballisticians to analyse the specimens. This paper describes a development in the application of imaging technology for the identification of forensic ballistics specimens. Both the line-scan technique and the surface profiling technique have been applied to cylindrical ballistics projectiles to provide additional optical information for analyses. The combination of these two techniques will allow correlational data to validate the analysis of class characteristics and unique markings on forensic ballistics specimens.

Ballistics identification using line-scan imaging techniques

A new line-scan imaging technique, well-suited to the inspection of ballistics specimens, is presented. The proposed system addresses a number of problems associated with the imaging of cartridge cases when conventional inspection techniques are used. This particular paper deals exclusively with imaging of the cylindrical surface of cartridge cases. Imaging of the firing pin marks on the end of the case is not considered. Results obtained so far from a prototype system are presented. It should be noted that this technique is still very much in its experimental phase and that as yet it has not been fully investigated for this forensic ballistics application.

The development of 3-D (stereoscopic) imaging systems for security applications

Stereoscopic or 3D imaging systems have been investigated by many research groups for a considerable number of years. Experimentation has shown that the use of such vision systems enables quite sophisticated manipulative tasks to be carried out remotely. Recent developments in materials science, electronics and video camera capabilities now make 3-D television systems for teleoperator applications a much more viable proposition than in the past. This paper describes the development of a range of 3-D systems which have been used for remote controlled vehicle and manipulator guidance in hazardous environments. Two particular scenarios are in dealing with improvised explosive devices (IEDs) and also in a nuclear industry application. The paper mentions the development of novel stereoscopic sensors based on line-scan cameras. One application of such packages may well be in wide area surveillance.

Line-scan system for all-round inspection of objects

Sensor choice is critical in all object inspection imaging systems and the suitability of different types of sensor must be thoroughly assessed before a decision is made. Despite its wide use, a television type camera may not represent the best choice for certain object inspection applications. Specifically, when inspection of an object that has a degree of cylindrical symmetry is required, a line-scan camera is a viable alternative to the television type and, in general, any matrix camera, offering a number of unique advantages. By applying rotational motion to the object of interest and using a line-scan device, an 360 degree(s) view of the object is obtained. The cylindrical surface of the object is effectively unfolded into a planar 2D one, allowing for the efficient inspection of the entire surface of the object from a single, continuous image. To allow accurate object space co-ordinate measurement, a line-scan camera calibration technique has been developed, catering for both interior and exterior parameter calibration. The former accounts for the lens effective focal length, the pierce-pixel value and the timing of the line-scan camera, while the latter yields the relative position and orientation of the camera with respect to a reference object space co-ordinate system.

Line-scan sensor: an alternative sensor modality for the extraction of three-dimensional coordinate information

We describe research carried out to investigate a stereoscopic line-scan system for the extraction of 3-D coordinate information from a scene of interest. Initial work involved analyzing the operating characteristics of a line-scan device for the production of 2-D images. Following this, a theoretical appraisal was undertaken of a sensor in a stereoscopic arrangement, and a mathematical model was derived for the calibration of a novel camera system. Algorithms to determine the 3-D relationship of points in the object space were developed using this model. To test the suitability of the model, a complete stereoscopic line-scan system was constructed. Experiments were conducted with the stereo camera to establish the accuracy that is achieved with such a system using the developed algorithms. The results indicate that the relative position of points in the object space could be determined to an accuracy of less than 1 mm at a range of 1.5 m.

Panoramic line-scan imaging system for teleoperator control

It is the intention of this paper to give details of the continuing research into obtaining 3-D coordinate information from an object space using non-standard video sources. Details are given on producing images with the line-scan sensor by rotating the device relative to an object space. Theoretically, this could provide picture information from a potential 360 degree panoramic view. However, initial results have demonstrated that such images are difficult for humans to interpret. Details are given in this paper on the limitations of the line-scan images produced from camera rotation for presentation to human observers.

Multiple view dual-energy X-ray imaging

This paper introduces a multiple view X-ray line-scan imaging technique for the screening of carry-on-luggage and hold cargo encountered in aviation security. The three-dimensional information inherent in the resultant perspective images can be visualised as a smooth object rotation on a video display monitor. It has also been demonstrated that this rotational effect can be incorporated into a dynamic binocular stereoscopic display. In order to produce the closely matched perspective images required by this technique an integrated multiple view dual-energy X-ray camera is under development.

Ballistics imaging-latest developments

This paper outlines the latest developments concerning a forensic imaging system that uses a CCTV camera in a line-scan mode for the inspection of bullet specimens placed on a rotating platform. Specifically, line-scan images obtained from the cylindrical sides of fired rounds including both projectiles and cartridge cases plus firing pin marks are discussed. Ultimately, it is anticipated that this research will lead to the development of a forensic imaging application from which a data base can be built to automatically match different bullet specimens in much the same way as a fingerprint data base is operated.

Testing and evaluation of an advanced (3-D) X-ray screening system

This paper presents a 3-D X-ray screening technique based on stereoscopic tomography. This is realised using a single X-ray source and folded line-scan X-ray sensors. The research was originally initiated to develop a binocular stereoscopic X-ray screening technique to enhance the visual interpretation of complex X-ray images, specifically in response to problems encountered in the routine screening of freight by HM Customs and Excise. This phase of the work culminated in the successful development of several experimental machines utilising a single X-ray source and a pair of standard linear X-ray detector arrays. More recently a system has been developed in collaboration with the Police Scientific Development Branch (PSDB), Home Office, which uses folded dual-energy line-scan sensors. The dual-energy sensor provides a material identification capability.

Derivation of 2.5D image models from one-dimensional x-ray image sensors

This paper describes on-going research into the development of a 21/2D image modeling technique based on the extraction of relative depth information from stereoscopic x-ray images. This research was initiated in order to aid operators of security x-ray screening equipment in the interpretation of complex radiographic images. It can be shown that a stereoscopic x-ray image can be thought of as a series of depth planes or slice images which are similar in some respects to tomograms produced by computed tomography systems. Thus, if the slice images can be isolated the resulting 3D data set can be used for image reconstruction. Conceptually, the production of a 21/2D image from a stereoscopic image can be thought of as the process of replacing the physiological depth cue of binocular parallax, inherent in a stereoscopic image, with the psychological depth cues such as occlusion and rotation. Once the data is represented in this form it is envisaged that, for instance in the case of a security imaging scenario a suspicious object could be electronically unpacked. The work presented in this paper is based on images obtained from a stereoscopic folded array dual energy x-ray screening system, designed and developed by the Nottingham Trent University group.