Research On Laser Ranging Technology Based On Time-of-flight

With the rapid development of science and technology,human beings in civil,industrial,military,aerospace and many other fields have imposed higher requirements on the measurement range and measurement accuracy of the distance.The traditional measurement methods(such as ultrasonic ranging,infrared measurement Distance and radio frequency electromagnetic wave ranging,etc.)can no longer meet the needs of the development of science and technology.Laser ranging is a kind of precision optical measurement technology developed during the continuous development of laser technology.Laser ranging has the advantages of long range,high precision,high speed,good concealment,and strong anti-interference ability,which make it widely used in military,guidance,measurement and control,aerospace and other fields.This paper aims to design a high-precision laser ranging system that can achieve distance measurements of 3000 meters with an error of no more than 1 meter.The following work has been completed for this purpose:(1)Analysis of the principle of laser ranging:After comparing the advantages and disadvantages of both phase-based laser ranging and pulsed laser ranging,consider the advantages of the latter with longer detection distance,better concealment,and stronger anti-interference ability,etc.This article chooses pulsed laser ranging.In combination with the laser ranging equation and related parameters,the detection capability of the laser ranging system is discussed,and several key system errors affecting the accuracy of the pulsed laser ranging are analyzed,ie the principle error of the time interval measuring module and the time-differentiating jitter Errors and drift errors caused by attenuation of echo power.(2)The overall design and analysis of the pulsed laser ranging system:The laser ranging system is mainly composed of a laser emitting unit,a collimating unit,a focusing unit,a laser receiving unit,and a signal processing unit.In this paper,a laser with a peak power of 2.5 MW,a pulse width of 5 ns,and a laser wavelength of 1064 nm is used as the emission source.The IAG 200X APD from Laser Components of Germany is used as the detector of the echo signal.The linear response model is determined according to the bandwidth and magnification of the APD.,And calculated its thermal noise and shot noise.(3)Design of laser echo signal electronics system:The current signal output by APD is converted into a voltage signal by a transimpedance amplifier OPA657,and a main amplifier circuit composed of two stages of AD603 is used to further amplify the voltage signal.The weak signal is analyzed in detail and elaborated.Based on the relevant detection principle,a constant ratio timing discrimination circuit is designed to determine the timing start and end timing and the peak hold circuit so as to facilitate subsequent AD sampling.(4)Time interval measurement module design:Based on the pulse counting method,a digital phase-shifting time interval measurement method—the equivalent pulse counting method—is used to improve the time resolution.The measurement principle and error of the method are discussed in detail.According to this method,a high-precision time interval measurement module is designed using FPGA,and the measurement error of time interval does not exceed 250ps.(5)System performance simulation test:Based on the APD model,a simulation experiment was performed on each module.The results showed that the echo amplification circuit achieved a total gain of 95.46 dB for echo signals with a measurement range of 3 km,and the response time of the peak hold circuit was 1.5.In ns,the peak-to-peak relative error is less than 9%,and the bleed rate is 5.06mV/μs.The time-differential jitter error caused by noise in the constant ratio timing circuit is 706.4ps at the maximum,and the measurement error of the time interval measurement module does not exceed 250ps.The total ranging error does not exceed 1m,which meets the system design requirements.