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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Investigations relating to the computer restoration of ultrasonic sector scan images

Burger, R. E. January 1987 (has links)
This dissertation describes the application of maximum entropy image restoration to envelope-detected ultrasonic sector scans. The maximum entropy restoration of the image of a point target (phantom) test object is shown to be superior to results obtained from the more familiar Wiener filter. The subsequent application of maximum entropy to an in-vivo clinical ultrasound image, however, illustrates the pitfalls associated with determining the relative merit of an ultrasonic image restoration technique from test object results alone. Since the resolution of sector scan images is substantially worse in the lateral (azimuthal) scan direction than the axial scan direction, the deconvolution filters described in this thesis were applied in the lateral direction only. The maximum entropy method is shown to have certain inherent advantages over linear frequency-domain techniques for the restoration of ultrasonic sector scan images. The positivity constraint inherent in the maximum entropy method is shown to produce restorations with substantially fewer oscillatory artifacts than those produced by Wiener filtering. In addition, the iterative nature of the maximum entropy algorithm is shown to be compatible with the restoration of the undersampled regions in the far field of sector scan images. The restoration of sector scan images is complicated by the spatially varying degradation associated with such images. A novel approach to the restoration of this class of image degradation is presented in this thesis. The widespread use of maximum entropy image restoration has been inhibited by the technique's demanding computational requirements. This problem can be alleviated by the use of high speed computer hardware, and the final chapters of this thesis describe the design and construction of a microcomputer-based array processor. The advantages inherent in the use of such hardware are demonstrated with reference to the maximum entropy restoration of ultrasonic images.

N-tuple based image analysis using transputers

Bouridane, A. January 1992 (has links)
No description available.

Spatial filtering in multi-resolution texture image analysis

Dessipris, Nikolaos G. January 1990 (has links)
No description available.

Automatic moire topography

Reid, G. T. January 1988 (has links)
No description available.

Digital Spatial Domain Multiplexing technique for optical fibre sensor arrays

Hu, Yiqun January 1997 (has links)
No description available.

Fixed pattern noise compensation in a mercury cadmium telluride infrared focal plane array

Reddy, Praven January 1998 (has links)
Bibliography: pages 106-109. / This thesis describes techniques for the correction of spatial noise artifacts in a mercury cadmium telluride infrared camera system. The spatial noise artifacts are a result of nonuniformities within the infrared focal plane detector array. The techniques presented dispense with the need for traditional temperature references, and provide nonuniformity compensation by using only the statistics of the moving infrared scene and motion of the camera assembly for calibration. Frame averaging is employed, assuming that all of the detector pixels will eventually be irradiated with the same levels of incident flux after some extended period of time. Using a statistical analysis of the camera image data, the correction coefficients are re-calculated and updated. These techniques also ensure that the calculated coefficients continually track the variations in the dark currents as well as temperature changes within the dewar sensor cooling vessel. These scene-based reference free approaches to the calculation of compensation coefficients in the infrared camera are shown to be successful in compensating for the effects of fixed pattern spatial noise.

A programmable image processor

Atkin, Philip January 1989 (has links)
No description available.

Object characterisation and image segmentation using a modified HSI colour space

Pritchard, A. J. January 1995 (has links)
No description available.

Topology and measure theory in the digital setting : on the approximation of spaces by inverse sequences of graphs

Webster, Julian Hilary Michael January 1997 (has links)
No description available.

Segmentation of natural texture images using a robust stochastic image model

Kim, Kyu-Heon January 1996 (has links)
No description available.

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