Thesis (Ph. D.)--University of Texas at Austin, 2009. / Title from PDF title page (University of Texas Digital Repository, viewed on Sept. 15, 2009). Vita. Includes bibliographical references.

Thesis (MSc)--University of Stellenbosch, 2005. / Bibliography. Also available via the Internet.

This work details two investigations into image capture, taken from the fields of x-ray and laser research, and also details two scanning systems: a wire surface generator and a video security device. Firstly a camera system is described that can display images, digitize them and provide real time false shading. This camera is shown to have a linear intensity response and to have a maximum saturation level below the digitizing range. Some example outputs are then illustrated. The ability to irradiate CCDs with direct X-ray radiation is also investigated. A camera is developed that vertically integrates such images and is shown to give an increase in the processing speed of existing equipment and to reduce experiment times by a factor of 388. Taking this idea further, a fast one dimensional camera is developed. This camera couples laser pulses onto a CCDs via a fibre optic faceplate and a 25 mum slit. Unusual scanning techniques are used to achieve image storage within the sensor itself and a method for correcting dark current and other errors is proposed. Next a mechanism for displaying wire surface representations of intensity) images is investigated. Results obtained from real time, hidden line removing hardware are illustrated, along with improved algorithms for shaded surface generation. This is then developed into a security device protecting VDUs from radio based surveillance. This is achieved by randomizing the display order of raster lines along with a hardware solution for random sequence generation. Finally the generation of Uniformly distributed random numbers is achieved by processing readings from a digitized. Normally distributed voltage source. The effects of this processing are investigated and an analysis of the underlying theory is used to determine an optimal setting for the gain stage.

The research described in this dissertation focuses on the development of a new approach for the generation of geometric models from multiple-view range image data. Through intensive comparison and evaluation of different representations, the cross-section contour based representation is concluded to be ideal for modeling with range image data. The representation is shown to be at an intermediate level - compatible with both the low-level of range image data and with the need to provide relatively high-level geometric and topological information in models. A new concept of generating partial models within device frames, frames associated with the working principle and geometry of a range sensor, is introduced. The range data are well distributed in the device frame. This good data distribution facilitates computations relevant to rendering the cross-sections required by the representation and relevent to identifying occlusions present in the image. Methodology for merging the partial models with a current global model is developed to allow the incorporation of redundancy between the partial model and the current global model and to allow growth of the global model. A simulation of the ERIM imaging-radar based range sensor, a prototype triangulation-based range sensor developed for this research and a commercial HYMARC range sensing system are used for approach verification. The device frames associated with the sensors are derived, and used to test the modeling approaches and the developed system. The presented research: demonstrates the suitability of the cross-section based representation for range-image based modeling systems; introduces a new concept and associated methods for generating cross-section contour models in range sensor device frames to take advantage of well distributed data; develops a series of algorithms for partial modeling in the device frame and for global model integration; and demonstrates the feasibility of the developed new approaches for applications by testing the system for multiple sensor types. / Graduate

Thesis (MSc (Physics))--University of Stellenbosch, 2005. / The extremely high light intensities produced by lasers and the increasing use of lasers highlights the need for measures to prevent damage to materials due to exposure to high intensity laser light. In particular it necessitates the development of systems to protect optical sensors, including the human eye. In this work optical limiters were investigated as a system for protecting sensors. An optical limiter transmits ambient light, but absorbs high intensity light. This makes it ideal for protecting sensors from laser radiation, since it allows the sensor to operate unhindered at design intensities while protecting it from harmful high intensity radiation. There are various mechanisms used for optical limiting, and in this work the nonlinear absorption and the nonlinear index of refraction changes of materials were investigated. A facility was established to measure the nonlinear optical properties of a variety of materials, in order to classify them as possible optical limiters. This entailed creating a so called Zscan setup, which enabled us to measure the nonlinear absorption coefficient and the nonlinear index of refraction of a material. The theory and the design of the setup are discussed and experimental results obtained using this setup are presented. A wide variety of material types were investigated to show the versatility of the experimental setup. These included C60, which was analyzed in solution; ZnO which is a crystal; CdS quantum dots in solution; and poly(dioctyl-fluorene), which is a large polymer molecule, in solution. The materials investigated in this work were chosen based on their known strong nonlinear optical properties. Emphasis was placed on measuring the nonlinear absorption coefficients since it was the dominant optical limiting effect of the materials under investigation. The results obtained displayed the same trends as published results and it shows that the established facility was capable of measuring the nonlinear properties of these samples. The experimental limitations of the setup were determined, and critical experimental parameters were identified for measurements of this nature. Improvements to the experimental facility are suggested to improve the accuracy of future measurements.

Thesis. 1975. Sc.D.--Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science. / Vita. / Includes bibliographical references. / Sc.D.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: Aniosotropy; scanning instruments; scanning; surface metrology; surface; fractal. Includes bibliographical references (p. 52).

This dissertation provides the first demonstration of scanning synthetic aperture radar (ScanSAR) advanced interferometry processing for measuring surface deformation. ScanSAR data are synthesized from ERS-1/2 stripmap SAR images over known deformation in Phoenix, Arizona. The strategy is to construct a burst pattern similar to Envisat ScanSAR data and to create a realistic variable-burst synchronization scenario in which any image pair has at least 50% burst overlap. The Small Baseline Subsets technique is applied to the synthesized data to demonstrate ScanSAR time series analysis for a scenario generally conducive for interferometry. The same processing approach is employed with the stripmap data to validate the results. The differences in ScanSAR and stripmap velocities have a mean and standard deviation of 0.02±0.02 cm/year. 96.3% and 99.1% of the velocity differences are within ±0.1 cm/year and ±0.2 cm/year, respectively. The RMS deviations between the ScanSAR and stripmap displacement estimates are 0.40±0.30 cm. 68.5% and 94.6% of the differences are within ±0.5 cm and ±1.0 cm, respectively. The Permanent Scatterer (PS) technique also is adapted and applied to the synthesized data to demonstrate the presence of PS in ScanSAR data. The atmospheric and nonlinear motion phase derived from a PS analysis of stripmap data are removed from the ScanSAR interferograms. Even for this idealized scenario, the final PS identification yields fewer ScanSAR PS (10 PS/km²) than the stripmap PS results (312 PS/km² or 15.6 PS/km² at the ScanSAR pixel resolution). Based on the calculated likelihood of finding multiple stripmap PS within a ScanSAR pixel, it is concluded that the ScanSAR single scatterer PS model is flawed. A model is introduced that considers multiple PS within a ScanSAR pixel. The search for two PS per pixel yields 120 PS/km². The ScanSAR and stripmap PS velocity differences mean is zero and standard deviation is 0.02 cm/year. However, while the differences between the ScanSAR and stripmap PS DEM error estimates are zero-mean, they have a 7-meter standard deviation. One possible explanation for this relatively large deviation is the differencing of the wrong ScanSAR and stripmap PS as the result of a misalignment between the ScanSAR and stripmap images. / text

Many applications in optical research require the use of diffraction limited point images with reduced spot sizes. The instrumentation that evaluates these small diameter images must have high resolution (sub-micron) capabilities. One method used to measure sub-micron optical point images is a scanning grating technique. However, many characteristics of this measurement technique have not been fully examined. In this paper, the sensitivity of this measurement technique to the scanning mechanism, beam characteristics, and grating tilt is evaluated.

A prototype rapid, high precision fan beam optical computed tomography (OptCT) scanner for three-dimensional polymer gel dosimetry of complex radiotherapy protocols has been developed. This study documents the design. construction and characterization of the system, as well as preliminary reconstructed optical attenuation images and dosimetric verification experiments. The principal goal in scanner design and implementation was to satisfy the Radiotherapy Accuracy and Precision (RTAP) criteria consisting of a spatial resolution of 1 x 1 x 1 mm3, an imaging time of 60 minutes, a dose accuracy within 3% and a precision within 1%. The scanner, which employs a sixty degree fan beam of 543 nm laser light to scan irradiated polymer gel samples up to 19 cm in cross-sectional diameter. has several defining attributes. Data acquisition for a single slice through a dosimeter is achieved in two minutes, using one signal acquisition per CT projection angle over a total of 360 projections. The effects of scatter and refraction of visible light are minimized by using the unique radial design of the matching medium tank, the concentric arrangement of a prototype, computer numerical control (CNC)-machined collimator and five Hamamatsu photodiode detector arrays for light detection. The novel tertiary collimation eliminates scattered light by 13% and improves reconstructed image contrast-to-noise ratio. Other characteristics of the scanner include: a laser power output variation of only 0.7%:, signal-to-noise ratio (SNR.) for calibration projections of up to 294:1, SNR for transmission projections through an irradiated polymer gel dosimeter of up to 161:1, a large absorbance dynamic range extending from 0.1 to 1.7 absorbance units and a spatial resolution of 0.25 mm2 in the axial plane of the scan¬ning geometry and 0.8 mm along the longitudinal z-axis of the scan plane. Images of optical attenuation coefficients and concomitant dose maps extracted from irradi¬ated, normoxic N--isopropylacylamide (NIPAM) polymer gels were used to investigate the potential of the system for dosimetric verification. Three different NIPAM gel irradiation experiments were performed and the resultant OptCT dose distributions were compared to the Eclipse® (Varian Medical Systems. Palo Alto. CA.) treatment planning system model. While the fan beam OptCT scanner provides promising ini¬tial images of reconstructed optical attenuation coefficients, its dosimetric accuracy compared to Eclipse - nominally 7% in low dose gradient regions and 5% on the field edges - constitutes the most significant area for future refinement.