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UBC Theses and Dissertations

Close range photogrammetric systems and their applications in ophthalmology Frankich, Kresho

Abstract

Photogrammetry as a measuring tool has been applied mainly in topographic mapping, although from the very beginning of its development there have been a sufficient number of attempts-to apply photogrammetry in various fields of science. However with the exception of the utilization of photogrammetry in architecture, criminology and investigation of traffic accidents, which has been a standard procedure in many European countries, all other applications have remained in the experimental stage. There are many reasons for the fact that non-topographic photogrammetry has not obtained general acceptance. The methods, instruments and ample potential of photogrammetry are practically unknown to scientists. Fortunately developments in recent years have been changing the situation slightly. A rapid increase of interest in the application of photogrammetry in various branches of science cannot be satiated with metric cameras only. Standard amateur and professional cameras, television systems, holography, x-rays and many other "nonconventional" photogrammetric systems have been serving as non-metric data acquisition systems. Very concentrated investigations in numerous photogrammetric centres all over the world are now underway to evaluate the quality of non-metric data acquisition systems. A special problem in the determination of very accurate measurements from photographs taken by non-metric cameras represents the camera calibration. The standard laboratory methods used for metric cameras are not very suitable for non-metric cameras because of their unstable parameters of interior orientation. This thesis includes a great variety of approaches in the camera calibration describing and assessing many methods that are used or suggested by various scientists all over the world. In the restitution of photographs taken by non-metric cameras using standard existing plotting instruments photo-grammetrists face the very serious problem of rather significant and irregular radial and decentering distortions which cannot be easily eliminated. Another problem is the plotting instruments which do not have sufficient range of principal distance. Plotting in such cases must be performed in an affine model with an exaggerated principal distance and vertical scale. All these problems can be avoided by the application of analytical plotters. The analytical approach is especial advantageous in the most general case of close-range photogrammetry where the elements of interior and exterior orientation as well as the calibration parameters of the cameras are simultaneously determined with the object space coordinates. It can only be hoped that in coming years instrument manufacturers will be able to produce a small and inexpensive stereocomparator with automatic coordinate registration. The field of ophthalmology is particularly suitable for photogrammetry. The eye as an object of research has very specific properties which make almost any measurements by conventional methods extremely difficult. The fundamental problem of measurements is the mobility of the living eye. To solve that problem photogrammetry may be the ideal measuring tool. The last part of this thesis deals with small number of attempts to utilize the great potential of photogrammetry in ophthalmology showing that without the combined efforts of the medical profession and photo-grammetrists no success can be achieved.

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