| In this dissertation several hybrid opto-electronic systems and techniques are described for the first time to allow the studies of motile microorganisms in close approximation to real-time. First, dynamic bio-speckle can be obtained from cultures of motile microorganisms. Based on theoretical analysis and experimental results, we discuss three techniques, namely, autocorrelation detection, relative histogram analysis, and holographic matched spatial filter, to process the signals derived from dynamic bio-speckle and to extract feature information about the cultures. Secondly, a novel imaging system has been set up to study and to track in-plane translation and rotation of a microorganism in the space domain. Unlike a conventional microscopic method, the observation volume in this system is much larger, and microorganisms can swim in an unconstrained environment. The novel feature of the system is the laser illuminator which forms enlarged Quasi Fourier Transformed (QFT) images of the microorganisms. These QFT images can be viewed directly on a monitor without further optical magnification, or captured and processed by a computer. Thirdly, a hybrid laser Doppler velocimeter (LDV) is studied and demonstrated to classify motion signature of a motile microorganism in the frequency domain. The new system includes two major units, a tracking and a three-axis LDV unit. An individual microorganism can be selected from the field to avoid ambiguity caused by multiscattering. During the measurement, a computer system collects and processes the time series data from transit of a microorganism through the measurement volume. The loci of the fast Fourier transform (FFT) contains the data which can be used to form a feature vector. Such a feature vector appears to be a useful criterion for distinguishing the species by methods of statistical pattern recognition. We have demonstrated that these new systems and techniques have unique advantages. For the first time, we can directly monitor the vitality of microorganisms in water samples, even in very low concentration and in the presence of detritus. Therefore, we believe these techniques can be effectively applied to many microbiological-related industries, such as in bioremediation processes, environmental protection engineering, and food processing industry. |
