RESUMO
Original waveforms and optimized signal processing are proposed for frequency-modulated continuous-wave lidar for range finding, velocimetry, and laser anemometry. For range finding, the aim of this signal processing is to extend lidar range and reduce ambiguities. Moreover, the effect of moderate atmospheric turbulence on lidar efficiency is analyzed for infinite and finite targets, taking into account wind-induced bistatism. For laser anemometry, the aim is to measure air speed at the shortest distance farther than the rotor-induced turbulent volume around the helicopter and to avoid parasitic echoes coming from clouds or hard targets in the vicinity of a helicopter.
RESUMO
Frequency-modulated continuous-wave lidar is evaluated for range finding, velocimetry, and laser anemometry. An original signal processing and waveform calibration for range finding leads to a reduction of computational effort while preserving capability for long-range measurement. Multiple target distance measurement is also demonstrated. For laser anemometry, the aim is to avoid parasitic echoes in the vicinity of a helicopter and to measure the air speed at the shortest distance farther than the rotor-induced turbulent volume around the helicopter. Flight tests of this functionality and vortex ring state warning are demonstrated.
RESUMO
The two-photon absorption resonance that is due to the internal charge-transfer transition of an organic push-pull molecule has been characterized. A nonlinear absorption spectrum of the 4-(diethylamino)- beta-nitrostyrene molecule was measured in a tetrahydrofuran solution by optical Kerr ellipsometry. The shape and the amplitude of the two-photon absorption spectrum are well described by a model that uses the relevant one-photon absorption spectrum related to the internal charge-transfer transition.