Hardware Study And Design Of High-Precision Phase-shift Ranging System

The pulse laser scanner currently is still the main method adopted in the field of laser threedimensional measurement in China.And there is no domestic manufacturer which has developed a phase-shift laser scanner with human eye safety level,millions of times per second,and millimeter accuracy.In this context,the thesis proposes a set of high-speed,high-precision phase-shift laser ranging scheme on the basis of 1550 nm laser with eye safety level by employing undersampling technology,which simplifies the system design.This thesis "Hardware Study and Design of High-Precision Phase-Shift Ranging System" aims to design a safe,fast and high-precision dual-frequency phase-shift ranging hardware system based on the theory of phase-shift laser ranging.In the phase-shift laser ranging technology,there are some problems that need to be solved urgently in China,such as the strong light intensity,which hurts eyes easily,slow measurement speed,and the nonlinearity of an avalanche photodiode(APD)due to its susceptibility to temperature.Aiming at the above problems,the thesis presents a solution to help the overall phase-shift laser ranging hardware system achieve high-precision,fast measurement at millions of points per second,which can be widely used in aerospace,cultural relics measurement,precision instrument manufacturing and other fields.The achievements and problems involved in this topic mainly cover the following aspects:1.For the eye safety,the thesis adopts 1550 nm laser wavelength,which is safe for the human eye,and dual-frequency measuring ruler to modulate the 1550 nm semiconductor laser simultaneously,so that the laser emission power can reach the first-level laser safety standard,which can improve the safety of the phase-shift ranging system effectively.2.To solve the problem that the measurement accuracy of the whole phase-shift laser ranging system is restricted by the non-linear characteristic of the reverse breakdown voltage of avalanche photodiode(APD)which varies with temperature,a new bias voltage and temperature compensation circuit is proposed to compensate the non-linear characteristics of APD,which can effectively reduce the final phase measurement error caused by the nonlinear response of APD,and improve the accuracy of phase-shift laser ranging.3.To address the problem that the laser reference and echo signals are too weak,the receiving system of the direct detection technology based on ADP is designed in this thesis.Through the low noise preamplification,power amplification,filtering and automatic gain conditioning for the weak laser echo signal,the phase-shift ranging system extracts the weak laser echo signals effectively.4.To settle the problem of slow measurement speed of the traditional phase shift laser ranging system,the thesis designs the high-speed signal processing board of FPGA+ARM.Meanwhile,on the basis of the simultaneous modulation and measurement scheme of the low-frequency and high-frequency measuring rulers,the processing board effectively receives and processes the two measuring rulers by using the dual-channel high-speed ADC to sample the laser reference and echo information synchronously.Finally,the measurement speed and algorithm solving speed of the overall phase-shift laser ranging system are improved.Finally,the author verifies several key technical problems in the research through experiments.Through the ranging verification experiment within 6m in the laboratory,the high-precision phase-shift ranging system achieves the level 1 laser safety,measuring speed of 1,000,000 points per second,system ranging accuracy of less than 1.9mm in 95% confidence interval.