Active based range measurement systems and applications

• Main Author: Ai, Xiao
• Published: University of Bristol 2014
• Subjects: 681
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.659107

In recent years, many instruments have been developed to capture distance and reflectance information. They have been incorporated into various applications, with two of these applications forming the focus of this work: (1) range cameras for obstacle detection and (2) integrated-path differential-absorption (IPDA) light detection and ranging (LIDAR) systems for space-borne remote sensing applications. Conventional range cameras are based either on triangulation or time-of-flight distance measurement principles. The former is constrained to indoor applications and the latter suffers from distance ambiguity. For space-borne IPDA LIDAR systems, the conventional pulsed approach takes two time-multiplexed measurements with laser pulses of different wavelengths, which results in measurement errors, due to the distance misalignment between the successive beams. The aforementioned problems have been solved in this work either by signal processing techniques or by deriving more suitable modulation schemes. In the first part of this thesis, the ToF camera captured range image has been enhanced by applying two modulation frequencies and Markov random field (MRF) modelling. This extends the non-ambiguous range and at the same time reduces noise. After which, the range images are then utilised in a novel obstacle detection system, which is described. In the second part of this thesis, a novel range imaging technique based on the random-modulation continuous wave (RMCW) scheme has been proposed. This technique extends the non-ambiguous distance and allows multi-user operation without the need for a software pre-processing procedure. In the last chapter of this thesis, the RMCW scheme has been extended to be applied in satellite remote sensing applications. This enables the use of continuous wave (CW) laser sources. Not only do CW sources offer a greater power efficiency, but this set-up also removes the beam misalignment problem. Together, this work has brought several innovations to the field of range measurement techniques and their applications.