Research On The Ranging Accuracy And Error Analysis Of The Underwater Laser Short-range Detection System

The ranging procedure of blue-green laser in water is complex.Many factors will affect the waveform of echo signal,such as the sea channel,the target reflection and the dynamic range of the receiving channel.These factors will lead to signal broadening,delay and saturation and so on,which will have a great impact on the accuracy of underwater laser ranging.Therefore,the ranging precision of blue-green laser in sea water are studied,by establishing the simulation model of underwater laser ranging.According to the component and optical properties of sea water,the absorption and scattering coefficients of sea water to 532nm green light are calcxulated.The Bidirectional Reflectance Distribution Function(BRDF)is used to describe the target reflection characteristics of the non-Lambert surface,and the power equation of the target echo power in the sea water is derived.According to the target echo power equation,the change law and dynamic range of target echo power under different target distance,incident angle and sea water quality are analyzed.The mathematical model of underwater pulse laser echo power is obtained by analyzing the modulation of the sea water channel,the target inclination angle and circuit parameters.Based on the mathematical model,a system error simulation method for receiving processing circuit is proposed,and the ranging accuracy of different time discrimination methods is analyzed,which is a reference for system design.By analyzing the variation of the system ranging precision with the target distance and the pulse width,the main error sources that affect the ranging precision are found.The analytic expression of the time discrimination shake error and saturation drift error is derived by using the linearized model,and the corresponding method of reducing or compensating error is given.And the saturation drift error compensation method is verified in the atmosphere.The range circuit is designed and made,and the correctness of the simulation model of underwater laser range finder is verified by the experiment of water pool,and the result of the measurement is corrected by the simulation error.The test results show that the maximum target distance of ranging system in simulated sea water is about 10m,and the precision of distance measurement is better than that of 0.3m.The research results can provide theoretical basis and design reference for the application of blue-green laser in underwater short-range ranging.