Sx Godber

A new stereoscopic X-ray imaging technique using a single X-ray source: theoretical analysis

A binocular stereoscopic X-ray imaging technique is presented which can be used for both visual inspection by human observers and also for the extraction of three-dimensional coordinate information. The concept of implementing a stereoscopic X-ray imaging system to solve the problem of image interpretation is not new in itself. However, what is innovative in this research is the stereoscopic imaging technique developed. This is based on a rigorous design theory specifically developed for a single X-ray source and a pair of linear X-ray detector arrays.

High energy transmission annular beam X-ray diffraction

We demonstrate material phase retrieval by linearly translating extended polycrystalline samples along the symmetry axis of an annular beam of high-energy X-rays. A series of pseudo-monochromatic diffraction images are recorded from the dark region encompassed by the beam. We measure Bragg maxima from different annular gauge volumes in the form of bright spots in the X-ray diffraction intensity. We present the experiment data from three materials with different crystallographic structural properties i.e. near ideal, large grain size and preferred orientation. This technique shows great promise for analytical inspection tasks requiring highly penetrating radiation such as security screening, medicine and non-destructive testing.

X-ray diffraction tomography employing an annular beam

We demonstrate depth-resolved materials characterization by scanning a sample through an annular beam of X-rays. We measure Bragg X-ray diffraction from a sample with a planar detector positioned centrally in a circular dark field defined by the annular beam. The diffraction maxima are optically encoded with the position of crystalline phases along this beam. Depth-resolved material phase images are recovered via tomosynthesis. We demonstrate our technique using a heterogeneous three-dimensional object comprising three different phases; cyclotetramethylene - tetranitramine, copper and nickel, distributed in a low density medium. Our technique has wide applicability in analytical imaging and is scalable with respect to both scan size and X-ray energy.

Discrimination of liquids by a focal construct X-ray diffraction geometry

A novel technique for the discrimination of liquids based upon X-ray diffraction and focal construct technology (FCT) is presented. FCT is a new, high efficiency coherent scatter harvesting technique. In this work, the competence of FCT to discriminate liquids was explored. A variety of liquids relevant to security inspection was analysed by FCT for application to liquid security inspection. Discrimination of potential threat liquids was successfully and reliably achieved even for limited data sets.

Energy-dispersive X-ray diffraction using an annular beam

We demonstrate material phase identification by measuring polychromatic diffraction spots from samples at least 20 mm in diameter and up to 10 mm thick with an energy resolving point detector. Within our method an annular X-ray beam in the form of a conical shell is incident with its symmetry axis normal to an extended polycrystalline sample. The detector is configured to receive diffracted flux transmitted through the sample and is positioned on the symmetry axis of the annular beam. We present the experiment data from a range of different materials and demonstrate the acquisition of useful data with sub-second collection times of 0.5 s; equating to 0.15 mAs. Our technique should be highly relevant in fields that demand rapid analytical methods such as medicine, security screening and non-destructive testing.

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.

Scatter enhanced 3D X-ray imaging for materials identification

This paper presents an imaging technique, which utilizes coherently scattered or diffracted X-rays for the identification of potentially harmful or illicit construct substances. Typically, the inherently low intensity of diffraction phenomena has lead to their use being limited to slow response laboratory instrumentation such as diffractometers. Our investigation concentrates on the requirements of scanning and imaging applications, which require orders of magnitude reduction in signal integration periods. We achieve this speed by employing a novel configuration of tubular X-ray beam to produce a series of high intensity foci. Each bright spot exhibits orders of magnitude increase in the diffraction signal in comparison with conventional angular dispersive methods. This novel technique promises a high-speed solution for security screening applications.