Research On High Precision Time Measurement System In Airborne 3D Laser Scanner

Airborne 3D laser scanning measurement technology is a means of observing earth spatial information.As most of the key technologies are monopolized by foreign countries,it is necessary to study a number of technologies in airborne 3D laser scanner,including high precision time measurement technology,High sensitivity photoelectric conversion technology and data acquisition and digital image processing technology.This will be developed with independent intellectual property rights for the cause of earthquake disaster reduction in the airborne three-dimensional laser scanner experimental prototype.This paper will study the high precision time measurement technology in the prototype.As the main part of the prototype,the time measurement system is to measure the laser pulse from the issued to the return of flight time information,used to determine the distance between the aircraft and the scanning target.Time measurement system indicators will directly affect some of the indicators of the prototype,such as geomorphic level measurement accuracy,vertical vertical measurement accuracy,the maximum measurement distance.The paper is based on FPGA design and time measurement system in the device.Based on the requirements of the prototype,the time measurement system requirements in the prototype are analyzed,and the time measurement scheme of the prototype is studied.Three kinds of time measurement system schemes are designed for the prototype.The time measurement system is designed,The three schemes are the vernier caliper method,the delay chain method and the improved counting method respectively.The design scheme is designed in a low-cost,low-power Cyclone IV series FPGA device,and the design of the time measurement system is realized by writing Verilog HDL programming.Finally,the time measurement system is tested.After testing,we can see that the time measurement system designed and realized in this paper has good measurement accuracy,resolution and stability,and satisfies the demand of time measurement system in prototype and other seismic instruments,and has good practical value.