Two digital image registration algorithms are tested and evaluated on a personal computer system. The two algorithms, correlation and sequential similarity detection, are tested and evaluated for speed of execution, accuracy, and optimum parameter determination. The programs are written in BASIC and can be easily converted to FORTRAN or other high-level language. Three different polynomial functions are tested and evaluated to improve the resolution of the correlation determination. Based on the results of the tests, it was concluded that the testing of registration algorithms is feasible in small computer systems and that sequential similarity detection is faster. An optimum threshold setting can be determined for an individual image. Increasing the magnitude of the SSDA threshold parameter increases the execution time of the SSDA program. Also, the resolution of the correlation can be improved with a curve fitting technique. / Master of Engineering

Digital imagers including Charge-Coupled Devices (CCD) are essential to most forms of modern photographic technologies. The quality of the data produced by digital imagers have made them an invaluable scientific measurement tool. Despite the numerous advantages of digital imagers, there are still factors that limit their performance. One such factor is the stability of the camera's gain, the ratio that dictates the imager's ability to convert incident photons to a measurable output voltage. Variations in gain can affect the linearity of the device and produce inaccurate measurements. One of the factors that determines the gain of the camera is the sensitivity of the output amplifier. The purpose of this study is to compare the performance of two different output amplifier structures: the traditional source follower (SF) and the charge feedback amplifier (CFA). In studies of other solid state detectors, the CFA has shown a greater stability against variations in certain system parameters and environmental conditions such as operating temperature. It is thought that the CFA shows a superior stability over the SF, because the gain of the SF is dependent on multiple capacitances associated with the reset and output transistors, whereas the CFA gain is only dependent on its feedback capacitance. Furthermore, the CFA is able to handle a larger amount of charge than the SF, which increases the dynamic range of the output amplifier. In this research, output amplifier stability is measured using gain and linearity data collected from a CCD manufactured with both types of amplifiers. Preliminary data is presented that indicates the CFA exhibits a greater linearity, larger dynamic range, and a more stable gain than the SF. Despite this the CFA suffers from a significantly larger level of noise. Suggestions for future research are also given as to how to verify and expand upon the results presented here.

Dimensional inspection with Vision Systems requires a careful selection of image analysis methods in order to obtain accurate information about the geometry of the parts to be measured. The purpose of this project is to study, implement and compare different image evaluation methods and to show their strengths and weaknesses with respect to dimensional inspection. Emphasis is made on the inspection of circular features. The criteria of comparison for these methods are discussed. Using synthetically generated images, various analysis methods are compared and conclusions for their use are drawn. Results of the comparison show that the selection of a method has to be done with regard to the noise level of the measurement. Finally, a computationally fast calibration algorithm is studied and implemented .

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Recently, the number of digital imaging systems incorporated into information display applications, such as military and industrial aerial reconnaissance, has increased rapidly. These imaging systems provide considerable flexibility for the processing and enhancement of information that otherwise might be unnoticed in conventional imaging systems. Many of the digital enhancement techniques, however, have not been subjected to systematic evaluations to examine their influence upon operationally relevant human task performance. This paper reports the findings of a segment of an ongoing research program designed to establish a digital image database, to standardize a set of experimental procedures of obtaining human performance data, and to relate these performance measures to various image display conditions. The image database consists of low-altitude aerial scenes of various military and. civilian installations. Original transparencies were digitized with a microdensitometer to generate the image database for magnetic tape storage. The digitized images were then degraded by blur and noise to simulate various levels of system resolution and system signal-to-noise ratio, respectively. Two experimental tasks were developed to assess the effects of digital image quality upon human performance characteristics of interest to the military reconnaissance community. An information extraction task required the human observers to answer a series of questions pertaining to the essential elements of information with each image. A subjective rating task required observers to estimate the extent of image interpretability. Using military photointerpreters as subjects, studies were conducted to assess the effects of image degradations (blur and noise) and image enhancement/restoration processing on human performance. The studies employed high-resolution, black-and-white CRT monitors to display the digital images. Results indicated that both blur and noise image degradations impaired interpretability of the imagery and that several enhancement/restoration processing techniques substantially improved interpretability of the imagery. These results provide useful information for users of digital imaging systems and for researchers to aid future developments of digital image processes. / Ph. D.

This thesis presents the design of a real time digital image correlator circuit The circuit accepts images in real time from two video sources, with one video source serving as a reference with which images from the second video source are compared. The proposed circuit extracts a reference window from the reference image and a horizontal band from the input image, and performs real time image cross-correlation on the two extracted portions. The resulting cross-correlation values are shifted out of the circuit as they are computed. The size of the reference window, the size of the image pairs, and the vertical offset of the reference window and input band are externally selectable. The circuit has been modeled in VHDL and simulated using the SYNOPSYS VHDL Simulator. This thesis also presents a proposed implementation of the circuit. / M.S.

A severely defocused incoherent system has isolated zeros in its optical transfer function(OTF); therefore, an exact inverse filtering cannot be performed. It has been established that, by using an annular aperture in an optical system, the depth of focus can be extended. Isolated zeros in the OTF can therefore be avoided by choosing an annular aperture with a proper radius ratio. However, in the process of increasing the depth of focus of the system, this method results in a loss of image contrast. An annular pass filter can be used to restore this loss in contrast. A simple hybrid optical/digital image processing system in which a TV camera is coupled with an annular aperture is considered. The annular-pass filtering to compensate for the loss of contrast is performed by a digital computer. The experimental results are presented. / M.S.

Digital image segmentation using periodic codings is explored with reference to two applications. First, the application of uniform periodic codings, to the problem of segmenting the in-focus regions in an image from the blurred parts, is discussed. The work presented in this part extends a previous investigation on this subject by considering the leakage effects. The method proposed consists of two stages. In each stage, filtering is done in the spatial frequency domain after uniform grating functions are applied to the images in the spatial domain. Then, algorithms for finding the period and phase of a physical grating are explored for a hybrid optical-digital application of the method. Second, a model for textures as the linear superposition of periodic narrowband components, defined as tones, is proposed. A priori information about the number of the tones, their spatial frequencies, and coefficients is necessary to generate tone and texture indicators. Tone indicators are obtained by filtering the image with complex analytical functions defined by the spatial frequencies of the tones present in the image. A criterion for choosing the dimensions of the filter is also provided. Texture indicators are then generated for each texture in the image by applying the a priori information of the tonal coefficients to the filtered images. Several methods for texture segmentation which employ texture indicators are proposed. Finally, examples which illustrate the characteristics of the method are presented. / Master of Science