The Research On Reconfigurable Lidar Data Acquisition Platform

Because laser beams have excellent directionality, monochromaticity, coherence and high intensity, Lidar can achieve higher resolution and larger detection range. What is more, Lidar is able to identify and classify the objects by probing tiny particles, even molecules and atoms, which are out of the detectability of Radar. Hence, Lidar is widely used in atmospheric monitoring, ocean science and biomedicine. Obviously, there are many kinds of Lidars, that naturally lead to the variety and complexity of data acquisition system.Currently, the mission of Lidar data acquisition cannot be achieved by a single device, but be completed by numerous devices or acquisition cards, for example, the advanced digital oscilloscope, the multi-channel scaler (MCS), NI integrated instruments, and Licel TR products, etc. The introduction of these data acquisition products improves the measurement precision, and makes the operation more convenient. However, with the continuous new techniques and new requirements in Lidar, some research units design dedicated data acquisition cards to match precisely their respective program. In one hand, the rapid progress and marketization of Lidar need to decrease research and development costs by modular, standardized and integrated products. In another hand, in order to guarantee the scientific advancement and competitive advantage in market, an open and non-customized data acquisition system is expected to allow user’s redevelopment. Facing the urgent contradiction, this thesis proposes the establishment of a reconfigurable Lidar data acquisition platform (RLDAP). RLDAP not only expands the applications, but also increases the portability and compatibility to reserve resources for system upgrade and service future development on novel Lidars. The application of RLDAP will reduce repetitive funding and man-hours, and generate more economic and social benefits.The basics of this research are the deep investigation of history and present situation of Lidar, the principle of the optical receiver and photoelectric detection, the rule and specificity of Lidar data acquisition systems. The practicability of RLDAP is proved by laboratorial tests and field comparative experiments.The innovations of the thesis are as follows:(1) For the first time, the thesis introduces the concept of reconfiguration into Lidar field. Hence, the definition is extended to the mixture of multi-component reconfiguration, software and hardware reconfiguration, beyond any software or hardware part in computer science. The definition includes reorganization of hardware resources, online reconfiguration of FPGA logic, communication protocols with multi-mode processes, dynamic invocation of software procedure.(2) The research takes the lead in developing hierarchy detection techniques in our country. And the linear dynamic range of up to5～6orders of magnitude has reached the international advanced level. Although there are photon counters for ultra-weak optical signals and A/D converter cards for strong signals, these internal devices fail to meet the large dynamic range and high SNR. RLDAP overcomes the detection difficulty in the valid region of both mode signals, and breaks the limits of long-term dependence on the single foreign product.(3) During field experiments, RLDAP successfully covers both near ground and middle atmospheric detection, and fits kinds of Lidars including traditional and new Micro Pulse Lidar. RLDAP has been implemented in Rayleigh Doppler wind Lidar and visibility Lidar. Especially for20-60km wind field measurement, the key points are a high speed and high gain amplification for photon counting, a strictly linear amplification below the Nyquist frequency of the A/D converter for analog measurement, and high A/D converter resolution for weaker signals. RLDAP satisfies the requirements at the same time and helps achieve the wind measurement ranging from stratosphere to low mesosphere firstly in our country.