To quantitatively analyze the influence of vehicle platform vibration on the vehicle laser radar (LIDAR) measurement accuracy, the modal, harmonic response, and random vibration are analyzed using finite-element software. On this basis, combined with the optical path structure of LIDAR, the deformation of mirror caused by vibration is analyzed. The results show that the maximum deflection of the laser output angle resulting from the mirror deformation is about 0.0001 deg, which is much less than the 0.00573 deg (0.1 mrad) that is required by the performance of the vehicle LIDAR.
The vehicle LIDAR has been widely used in the fields of three-dimensional city modeling, terrain mapping, the agroforestry ecosystem, military detection, and unmanned driving for its advantages of high resolution, strong anti-interference ability, small volume, and light weight. The measurement accuracy of vehicle LIDARs is influenced by the internal heat source of the system and the external ambient temperature to a great extent. A compact vehicle LIDAR system is designed and analyzed. Combined with the distribution characteristics of the internal heat source of the LIDAR system, the temperature distribution and thermal deformation in the LIDAR system under different external temperatures are analyzed. On this basis, the laser path deviation of the LIDAR system caused by thermal deformation is also analyzed and compared. Finally, when the ambient temperature changes from −10 ° C to 50°C, the deviation of the laser output angle is within ±0.1 mrad by optimizing the design, which meets the requirements of the measurement accuracy of the vehicle’s LIDAR.
A miniaturized underwater polarized radiation measuring instrument (MUPRMI) LiDAR system applied in detecting the polarization optical parameter profiles for shallow water has been designed. This system will be used for detecting the depolarization of laser propagating underwater. For that purpose, a 532 nm linearly polarized laser with the repetition rate of 100 Hz and per pulse of energy of 50 μJ will be used in the system. When propagating underwater, the polarization state of laser will be changed in case of collision with the particles suspended in water. The linearly polarized laser will gradually become non-polarized due to depolarization, and the depolarization degree is related to the suspended particles. In order to detect the depolarization effect of waters, two orthogonal polarization receiving channels have been assembled in the MUPRMI system. For signal receiving, a photomultiplier tube has been assembled in each of the channels. By detecting the change of polarization state, parameters of scattering particles suspended in water in the detecting area can be inverted using inversion algorithm. The MUPRMI system can be controlled by a host computer, which communicate with the MUPRMI system using ethernet communication protocol. An adjustable aperture driven by a stepping motor has been assembled in the receiving optical path. Using this adjustable diaphragm, we can control the change of receiving field of view by transmitting instructions from the host computer, and change the reception of signals from different kind waters. A ship-borne experiments have been conducted in South China Sea, results show that the deepest bathymetry of the MUPRMI system is about 9 meters with the pulse energy of 50 μJ, in South China Sea.
The airborne lidar with two segmented field-of-view (FOV) receivers was used to detect the subsurface scattering layers. Significant differences were observed in the waveforms from one channel with small FOV of 6 mrad and the other channel with larger FOV of 40-6 mrad. The larger FOV of 40-6 mrad was to provide a larger dynamic range for the deep-water signal detection. A small-angle approximation based Lidar waveform simulation model was developed, and found that these differences are owing to the narrow beam divergence of laser pulse of only 0.3 mrad. Next, an algorithm, which incorporates a waveform-decomposition technique and a lowpass digital differentiator, was then used to detect the scattering layers from both small- and large- FOV channels. The observation of scattering layer along the coastal region of Sanya Bay of China shows that, more than three thin scattering layers can be found in the same water column close to the coasts, and the maximum depth of the scattering layer detected by the large FOV Channel can be up to 35m, and internal waves can be detected from spatial distributions of scattering layer. It can be found that the airborne bathymetry lidar with segmented field-of-view receivers can also be a great tool for the subsurface scattering layer detection.
Abstract: The measurement of ocean optical parameters is an important part of ocean research. According to the transmission of the blue and green laser pulse, the lidar return signals were analyzed, and the vertical profiles of the lidar attenuation coefficient were studied with airborne polarization lidar. Simultaneously, the absorption coefficient and extinction coefficient of South China Sea were measured using AC-S. Comparing the lidar and in situ measurements, we found that the lidar attenuation coefficient is between the absorption and extinction coefficient. The correlation analyses of lidar attenuation coefficient with absorption and extinction coefficient were carried out respectively, and it was shown that they have a good correlation. Overall, the results indicated that the airborne polarization lidar is an efficient way to detect the profiles of ocean and the combination of airborne lidar and in situ measurements provide comparable and complementary information about ocean optical parameters.