From Fauna to Flames : Remote Sensing with Scheimpflug Lidar

Sammanfattning: This thesis presents applications of the Scheimpflug Lidar (S-Lidar) method. The technique has been applied to combustion diagnostics on a scale of several meters as well as fauna detection and monitoring over distances of kilometers. Lidar or laser radar is a remote sensing technique where backscattering of laser light is detected with range resolution along the direction of the laser beam. It is an established method in e.g. atmospheric sensing where it is used to map and monitor gases and aerosols. In contrast to conventional Lidar, which uses a time-of-flight approach, Scheimpflug Lidar uses imaging to achieve range resolution. The laser beam transmitted from the Lidar system is sharply imaged onto a detector, resulting in range resolution along the sensor. This is done by placing the laser beam, the collection optics and the detector according to two trigonometrical conditions called the Scheimpflug and hinge rules. This kind of Lidar technique enables the use of small, continuous-wave diode lasers and line-array detectors with kHz sampling rates. A general description of the equations governing the achievable measurement range and resolution of S-Lidar are presented. The way the equations relate to the conventional Lidar equation is also discussed as well as the impact of the beam width. The instrumentation and experimental considerations for far range S-Lidar for aerial fauna monitoring are described and some temporally and spatially resolved data from field campaigns in Africa, China and Sweden are presented. A method used to reduce and analyze the large amount of collected data is also described. For the short-range applications, down-scaled versions of the system were developed. These systems are described as well as their applications. The short range system has mostly been used to investigate the potential of the technique to be applied for combustion diagnostics, and results from measurements in flames using both elastic and inelastic optical techniques, such as Rayleigh scattering and two-line atomic fluorescence are presented. A hyperspectral Lidar system aimed at aquatic applications is also presented.