Airborne Light Detection and Ranging (LiDAR) can perform high-density scanning on the surface and quickly collect massive point cloud data with information such as three-dimensional (3D) coordinates and echo intensity. It is an important means of geospatial data acquisition and plays a very important role in various fields such as power inspection, forestry investigation, digital city, culture heritage protection, altitude hold and collision avoidance of Unmanned Aerial Vehicle (UAV), etc. Driven by the development of sensor technology and practical demand, airborne LiDAR has made great progress in hardware performance as well as industrial applications. This paper reviews the current status of the light and miniature UAV-borne LiDAR in China and other contries, then typical applications in related fields are listed. Finally, some future perspectives are presented.
A long-distance, high-efficiency "cat’s-eye" target laser active detection method based on the characteristics of target echo spectral segments was proposed. Considering the target echo generation condition, multiple sets of different wavebands, high-frequency and short-pulse detection lasers are used to obtain the high-precision distance value of the detection target, and simultaneously record the echo intensity information of the detection signal for different spectral segments. Analyze the relationship between the target distance, the target feature, the probe band and the beam quality, correlate the distance with the spectrum information, calculate and identify whether the target is a "cat’s eye" target. In the experiment, 1064nm and 1550nm laser sources are used to detect and analyze different types of targets. The test results show that the detection method can quickly and effectively obtain the multi-spectral echo reflection characteristics of the target, and achieve the "Cat’s Eye" target detection in the kilometer range. Effectively reducing the number required for target identifies feature points, improves the recognition efficiency and accuracy, and reduces false alarms.
Online 3-D laser-scanner is a non-contact measurement system with high speed, high precision and easy operation, which can be used to measure heavy and high-temperature forgings. But the current online laser measurement system is mainly a mobile light indicator, which can only be used in the limited environment and lacks the capability of 3-D accurate measurement. This paper mainly introduces the structure of the online high-speed real-time 3-D measurement for heavy high-temperature forgings of Academy of Opto-Electronics (AOE), Chinese Academy of Sciences. Combining TOF pulse distance measurement with hybrid scan mode, the system can scan and acquire point cloud data of an area of 20m×10m with a 75°×40° field of view at the distance of 20m. The entire scanning time is less than 5 seconds with an accuracy of 8mm, which can meet the online dimensional measurement requirements of heavy high-temperature forgings.
The use of CCD imaging to measure laser divergence angle and imaging spot quality directly affect the accuracy of measurement results. Analysis of laser spot imaging features, do noise reduction and desaturation process for the image. With the method of image coordinate vectors superposition to obtain the laser intensity distribution curve in x, y direction, and laser spot diameter is exactly calculated by curve fitting algorithm. Experiment for different exposure intensity spot images, this method is effective to suppress the influence of CCD self-noise and improve measurement accuracy. Different exposure intensity spot images obtained a high measurement accuracy results, and laser divergence angle measurement results with an accuracy higher than 0.01mrad.