Study of Time Interval Measurement with High Accuracy and Multi-hits for Airborne Lidar

机载激光雷达技术（Airborne Lidar）是激光遥感技术中的一项重要技术，自它诞生以来就广泛应用于军事、农业、水利电力设计、国土资源调查、交通旅游与气象环境调查、城市规划等各大领域。 高精度激光测距是机载激光雷达技术中的一个重要分支。在激光测距中脉冲式激光测距法是最常用的长距离测量方法，它通过测量发射激光脉冲和被测目标反射脉冲之间的时间间隔，及激光的传输速度，获得脉冲发射点和被测目标之间的距离。因此实现高分辨率的时间间隔测量是获得高精度的距离测量的关键，传统的脉冲飞行时间测量技术是基于脉冲计数方法设计地，它的分辨率在ns量级以上，利用这种方法测量时间间隔难以实现距离测量的高精度。并且这种传统的时间间隔测量电路采用分立元件设计，电路的规模较大、抗噪能力较差。本文采用专用时间数字转换芯片进行时间间隔测量模块的设计，该时间数字转换器基于数字延时线插入法，其时间分辨率高达250Ps。同时，为了突破传统测距只能获取单目标的技术限制，设计了多目标测距手段，每个通道的目标响应可达到4个。另外模块中还使用了微控制器、可编程逻辑器件、FIFO存储以及PCI总线等技术，不仅缩小了模块的体积，而且使得模块具有很好扩展性和兼容性。 我们所研制的高精度激光测距模块以机载激光测深系统为应用背景，以获取高精度的海表高程为目标。文中对所设计的时间间隔测量模块的硬件、驱动程序、应用程序以及测试做了逐一介绍。该时间间隔测量模块不仅可以用于机载激光雷达系统，而且可以用在其它高精度时间间隔测量中，具有较广的应用潜力。Airborne lidar is a powerful device in laser remote sensing, and it is widely used in civil and military application. Laser range finder is an important branch of lidar. Pulsed laser range finder is a most widely used technique for long distance measurement. The resolution of nanosecond is limited using the traditional pulsed laser ranging technique. In this thesis, a time-interval-unit(TIU) with resolution as high as 250 ps is designed and fabricated. In order to overcome the single hit in the traditional pulsed laser ranging, the TIU has an ability of 4 hits in both two channels. In additional, the TIU is assembly by combining the techniques of micro-processor, PLD> FIFO and PCI BUS, so the size is smaller and the expansibilitVs flexibility is improved. At present, the TIU is used for an airborne Laser bathymetry. In the thesis, the introduction, designs of hardware^ PCI device driver, the application will be present respectively. The TIU scribed in this thesis has a powerful potential, it can be not only used in Lidar, but also be used in other high accurate time interval measurement