The modelling of multiple beam X-ray systems using visible light

Hon, H.-W., 2000. The modelling of multiple beam X-ray systems using visible light. PhD, Nottingham Trent University.

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In general, x-ray shadowgraph images are very difficult to interpret for human observers due to the lack of visual depth cues in an image which has been produced by transmitted radiation. The psychological cues to depth associated with 'normal' two-dimensional images such as a photograph are not available in a standard x-ray image. Further, these cues can be incorrectly interpreted as being present in an x-ray image and can lead to serious ambiguity in the subsequent visual interpretation of that image. In an attempt to solve this problem previous research has utilized the powerful physiological depth cue of binocular parallax by the production of binocular stereoscopic image pairs.

The solution put forward in this research is to introduce another powerful physiological depth cue of motion parallax into the resultant shadowgraph x-ray images. This is achieved by collecting a number of different views (i.e. from 6 to 16) of the object under inspection and displaying the resultant 'raw' perspective images in a specific sequence on a standard video monitor. This produces the effect of the object appearing to undergo a partial rotation in the display. Further work combined the geometric and temporal design theory developed for the production of motion parallax with that required for the production of binocular stereoscopic images. Therefore, the resultant image information can be viewed ill a number of different modes. These include a sequence of perspective images exhibiting motion parallax or a sequence of perspective images exhibiting motion parallax and binocular parallax.

In order to test the premise on which the theoretical analysis of the multiple view imaging techniques is based would require the development of sophisticated x-ray imaging apparatus. However, a visible light analogy of transmission x-ray imaging was identified as the theoretical basis for developing a visible light experimental system utilising a standard charge coupled device (CCD) area array camera. The camera is used to obtain perspective images during a single linear translation of the object under inspection. Thus the camera in conjunction with an appropriate image capture mechanism is used to obtain multiple perspective images in its standard mode of operation (i.e. area array 'snapshot') or a novel multiple line-scan mode. Therefore, both a theoretical and an empirical analysis of the imaging properties of these techniques has been conducted.

The results from this work produced sufficient interest by the Police Scientific Development Branch (P.S.D.B.) part of Home Office Science and Technology Group to provide funding to conduct definitive experiments with shadowgraph images. This was successfully achieved by implementing a real time image intensified x-ray set to validate the findings of the earlier visible light work. Thus the high degree of correlation between the x-ray and visible light techniques in terms of the spatial and temporal content of the resultant images has been empirically demonstrated and evaluated. The operational and scientific constraints adhered to throughout this programme of work enhance the general applicability of the imaging techniques developed for on-line applications encountered in security screening and industrial inspection.

Item Type: Thesis
Description: Collaborating Establishment: Home Office Science and Technology Group, Police Scientific Development Branch (P.S.D.B.), Sandridge, Hertfordshire, United Kingdom.
Creators: Hon, H.-W.
Date: 2000
ISBN: 9781369314915
Rights: This copy of the thesis has been supplied on condition that anyone who consults it is understood to recognise that its copyright rests with the author and that no quotation from the thesis and no information derived from it may be published without the author’s prior written consent.
Divisions: Schools > School of Science and Technology
Record created by: Linda Sullivan
Date Added: 30 Nov 2020 14:36
Last Modified: 10 Aug 2023 09:05

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