Research On Techniques Of Air Refractive Index Measurement And Compensation In Laser Ranging

High-precision absolute distance measurement technology plays an indispensable role in various fields,such as benchmark for advanced military equipment manufacturing,providing accurate experimental data for high energy physics and cosmophysics,and providing space vehicle with guidance and so on.Laser ranging technology has good stability,high precision and excellent measurement repeatability.As for the overground laser ranging system,its measured values are often susceptible to air disturbance.Two important methods to improve the accuracy of laser ranging are covered in this thesis,namely improving the system stability and reducing influence of the air refractive index.In this thesis,theoretical analysis and system design have been carried out for the second polarization modulation laser ranging technology,at the same time,the distance formula related to wavelength has been derived.Compared with the traditional phase measurement method,second polarization modulation technology can satisfy both requirements of range and accuracy.With qualitative analysis of the influence of air refractive index on the ranging accuracy,this paper proved that real-time high precision measurement of air refractive index is necessary.By using the Edlen formula,which has high precision in theory,measurements of the air refractive index are carried out.With the help of simulation of how much each atmospheric parameter affects the air refractive index,digital sensors are chosen to automatically measure temperature,humidity and atmospheric pressure in real time.To set up the ranging system,AD convertor and power supply are designed with low noise to improve the stability of the ranging.And by using the Zigbee technology,the air refractive index value can be transferred to the ranging system.In this thesis,on the condition of precision deficiencies of digital sensors,a novel method of taking temperature value as the correction factor for air pressure measuring and using high-precision sensors to calibrate the digital sensors is put forward.Through the correction of the calculation formula,the accuracies of measured atmospheric parameters are improved so that the accuracy of air refractive index is improved as well.Finally,the experimental data shows that the precision of distance with air refractive index compensation is better than that without compensation.So the air refractive index is proved to have great importance to ranging precision.