A line-scan system for the inspection and measurement of cylindrical surfaces

Zographos, A.N., 1998. A line-scan system for the inspection and measurement of cylindrical surfaces. PhD, Nottingham Trent University.

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This thesis describes research into a stereoscopic machine vision system specifically developed for the imaging of objects that have a high degree of cylindrical symmetry.

A preliminary investigation involved the consideration of two imaging scenarios based on the standard area array sensor. The first employed a network of such sensors in order to produce all-round observation of a cylindrical object. The second consisted of a single area array camera imaging a rotating object. It was found, however, that both schemes had a number of limitations which precluded the efficient inspection of cylindrical objects. These limitations were subsequently addressed by using a line-scan sensor and rotating the object to be inspected.

Following this initial investigation, an experimental two-dimensional (2-D) line-scan system employing rotational object motion was constructed. The imaging characteristics were analysed and experiments were conducted to evaluate the 2-D coordinate measurement capability of the technique. It was found that this system possessed the necessary attributes to be used in the extraction of coordinate information from a defined object workspace. The experimental line-scan system was utilised in the imaging of ballistics specimens, such as cartridge cases and fired rounds of ammunition.

The results obtained from this part of the investigation led to the development of a stereoscopic line-scan camera system, which could be employed to extract three-dimensional (3-D) coordinate data from an object of interest. To achieve this, a rigorous calibration technique, based on independent geometry for each camera with respect to both its platform and the object workspace, was devised. The resultant mathematical model was extended to encompass the calibration of all the critical parameters of the stereoscopic system.

Experiments were conducted to validate the system model and to determine the reliability of the analytical procedures applied when performing 3-D measurements. Further experiments were undertaken to characterise the spatial resolving properties of the stereoscopic system and evaluate its coordinate measurement accuracy. Utilising the existing hardware, the experiments indicate a spatial accuracy of 0.2mm to 0.4mm in all three coordinate axes at a range of 1.5m.

Item Type: Thesis
Creators: Zographos, A.N.
Date: 1998
ISBN: 9781369323412
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 its 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: 02 Oct 2020 08:26
Last Modified: 28 Sep 2023 09:53
URI: https://irep.ntu.ac.uk/id/eprint/41091

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