Development of a Full-Field Time-of-Flight Range Imaging System

A full-field, time-of-flight, image ranging system or 3D camera has been developed from a proof-of-principle to a working prototype stage, capable of determining the intensity and range for every pixel in a scene. The system can be adapted to the requirements of various applications, producing high precision range measurements with sub-millimetre resolution, or high speed measurements at video frame rates. Parallel data acquisition at each pixel provides high spatial resolution independent of the operating speed. The range imaging system uses a heterodyne technique to indirectly measure time of flight. Laser diodes with highly diverging beams are intensity modulated at radio frequencies and used to illuminate the scene. Reflected light is focused on to an image intensifier used as a high speed optical shutter, which is modulated at a slightly different frequency to that of the laser source. The output from the shutter is a low frequency beat signal, which is sampled by a digital video camera. Optical propagation delay is encoded into the phase of the beat signal, hence from a captured time variant intensity sequence, the beat signal phase can be measured to determine range for every pixel in the scene. A direct digital synthesiser (DDS) is designed and constructed, capable of generating up to three outputs at frequencies beyond 100 MHz with the relative frequency stability in excess of nine orders of magnitude required to control the laser and shutter modulation. Driver circuits were also designed to modulate the image intensifier photocathode at 50 Vpp, and four laser diodes with a combined power output of 320 mW, both over a frequency range of 10-100 MHz. The DDS, laser, and image intensifier response are characterised. A unique method of measuring the image intensifier optical modulation response is developed, requiring the construction of a pico-second pulsed laser source. This characterisation revealed deficiencies in the measured responses, which were mitigated through hardware modifications where possible. The effects of remaining imperfections, such as modulation waveform harmonics and image intensifier irising, can be calibrated and removed from the range measurements during software processing using the characterisation data. Finally, a digital method of generating the high frequency modulation signals using a FPGA to replace the analogue DDS is developed, providing a highly integrated solution, reducing the complexity, and enhancing flexibility. In addition, a novel modulation coding technique is developed to remove the undesirable influence of waveform harmonics from the range measurement without extending the acquisition time. When combined with a proposed modification to the laser illumination source, the digital system can enhance range measurement precision and linearity. From this work, a flexible full-field image ranging system is successfully realised. The system is demonstrated operating in a high precision mode with sub-millimetre depth resolution, and also in a high speed mode operating at video update rates (25 fps), in both cases providing high (512 512) spatial resolution over distances of several metres

New HCI techniques for better living through technology

In the Human Computer Interaction community, researchers work on many projects that investigate the efficacy of new technologies for better living, but unlike other research fields, these researchers must have an approach that is typically multi-disciplinary. Technology is always developing thus improving our lives in many ways like education, health and communication. This due to the fact that it is supposed to make life easier. This dissertation explores three main aspects: the first is learning with new technologies, the second is the improvement of real life by using innovative devices while the third is the usage of mobile devices in combination with image processing algorithms and computer graphics techniques. We firstly describe the progress on the state of the art and related work that have been necessary to implement such tools on commodity hardware and deploy them in both mobile and desktop settings. We propose the usage of different technologies in different settings, comparing these solutions for enhancing the interaction experience by introducing virtual/augmented reality tools for supporting this kind of activities. We also applied well-known gamification techniques coming from different mobile applications for demonstrating how users can be entertained and motivated in their working out. We describe our design and prototype of several integrated systems created to improve the educational process, to enhance the shopping experience, to provide new experiences for travellers and even to improve fitness and wellness activities. Finally, we discuss our findings and frame them in the broader context of better living thanks to technology, drawing the lessons learnt from each work while also proposing relative future work