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    Design of digital instrumentation for scanning probe microscopy : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Physics at Massey University, Palmerston North, New Zealand
    (Massey University, 1999) Klank, Henning Albrecht Michael; Klank, Henning Albrecht Michael
    A scanning tunneling microscope with a focus on digital instrumentation has been built. The aim of this project was to allow a digital signal processor full control over all essential microscope variables, especially simultaneous control of the vertical and horizontal tip position. Due to the fact that its operation is controlled by software, this system offers convenient operation and considerable flexibility, allowing different modes of operation, such as topographical and spectroscopic scans. Presently this microscope is the only one in New Zealand that allows the operator full software control over the tip position and bias voltage, thereby allowing it to become a powerful research tool. Atomic scale images on graphite were successfully recorded. The spatial resolution of the microscope was estimated to be 5 pm vertically and 40 pm horizontally. Two different imaging methods were demonstrated on a gold sputtered TEM grating with a scan area that was larger than 4μm x 4μm. One method has variable horizontal scan speed, while the other method can possibly be used for nanolithography. Both show the flexibility of this system. Although digital electronics is often perceived as being slower and noisier than analog electronics, in this instrument it did not decrease the data acquisition speed nor did it reduce the signal-to-noise ratio. The bandwidth of the closed-loop controlled microscope is currently about 1 kHz, limited by the bandwidth of the current-to-voltage converter, an analog component. The resolution is limited by the large gain of the high-voltage amplifiers used to drive the actuators. With a faster current-to-voltage converter and a reduced high-voltage amplifier gain, a bandwidth of 8 kHz should be possible with a vertical resolution of less than 2 pm and a horizontal resolution of 10 pm.
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    Least-squares optimal interpolation for direct image super-resolution : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Engineering at Massey University, Palmerston North, New Zealand
    (Massey University, 2009) Gilman, Andrew
    Image super-resolution aims to produce a higher resolution representation of a scene from an ensemble of low-resolution images that may be warped, aliased, blurred and degraded by noise. There are a variety of methods for performing super-resolution described in the literature, and in general they consist of three major steps: image registration, fusion and deblurring. This thesis proposes a novel method of performing the first two of these steps. The ultimate aim of image super-resolution is to produce a higher-quality image that is visually clearer, sharper and contains more detail than the individual input images. Machine algorithms can not assess images qualitatively and typically use a quantitative error criterion, often least-squares. This thesis aims to optimise leastsquares directly using a fast method, in particular one that can be implemented using linear filters; hence, a closed-form solution is required. The concepts of optimal interpolation and resampling are derived and demonstrated in practice. Optimal filters optimised on one image are shown to perform nearoptimally on other images, suggesting that common image features, such as stepedges, can be used to optimise a near-optimal filter without requiring the knowledge of the ground-truth output. This leads to the construction of a pulse model, which is used to derive filters for resampling non-uniformly sampled images that result from the fusion of registered input images. An experimental comparison shows that a 10th order pulse model-based filter outperforms a number of methods common in the literature. The use of optimal interpolation for image registration linearises an otherwise nonlinear problem, resulting in a direct solution. Experimental analysis is used to show that optimal interpolation-based registration outperforms a number of existing methods, both iterative and direct, at a range of noise levels and for both heavily aliased images and images with a limited degree of aliasing. The proposed method offers flexibility in terms of the size of the region of support, offering a good trade-off in terms of computational complexity and accuracy of registration. Together, optimal interpolation-based registration and fusion are shown to perform fast, direct and effective super-resolution.