Tomographic scanning imagers

Abstract

The tomographic scanning (TOSCA) family of imagers collects their raw signals from a line-shaped sensitive area scanned across the image plane. An image is then formed by tomographic reconstruction techniques. A TOSCA imager can be implemented by scanning knife edges, thin slots or thin line detectors across the image plane, repeating the scan at regularly distributed angular intervals. This thesis describes the conception, theory and practical realization of the TOSCA imaging technique, originally based on a simple hot spot scanner. The treatment incudes analysis of noise characteristics, sensitivity to alignment errors and errors in the scanning process, such as temporal offset and jitter. Detailed simulations are used as a tool to establish the different mechanisms that can degrade the image and the extent of their effect. Several experimental demonstrators are presented, operating in the visible, short wave infrared and mid wave infrared spectral domains, and also multispectral operation to demonstrate special features of the TOSCA imager system. Experimental noise measurements are shown to be in good agreement with theory. The reconstruction algorithms of these systems have demonstrated ability to handle illumination intensity modulation frequencies higher than the corresponding frame rate. It is demonstrated that a TOSCA imager can be created using simple and low cost components and consumer grade 3D-printers, opening up for the development of low-cost infrared imagers for use in low-cost survey drones, or for educational purposes.