Research On Key Technology Of Pulse-phase Laser Rangefinder

Laser has been widely used in the field of measurement, for its strong directivity, high brightness and good monochromaticity. There are two major laser ranging techniques:pulse measurement and phase-shift measurement. Pulse ranging achieves the measurement of the distance by measuring the time of flight. Phase-shift laser ranging accomplishes measuring distance by measuring the phase difference indirectly. The advantage of the pulsed laser ranging is easy to transmit pulse high power, so it always has long measurement distance; disadvantage is the measurement of the flight time is difficult to achieve high accuracy. Phase-shift measurement method can achieve very high precision, but due to the phase measurement only reaching one waveform, the measured range is short. In order to resolve the contradiction between the measured distance and accuracy, this paper presents a pulse-phase laser rangefinder.Pulse-phase laser ranging technology emits a beam of semi continuous sine wave in the transmitter and measures phase and time of flight of the received signal simultaneously. The design can be divided into three modules:the laser module, laser receiving module and the measurement module. Laser emission module uses controlled DDS chip to emit semi continuous of4MHz sinusoidal signal frequency and10KHz repetition frequency, and uses semiconductor laser diode as the laser transmitter. Laser receiving module use PIN as the laser receiver and accomplishes the signal amplifying and filtering; signal phase measurement module uses high-speed A/D chip to realize4MHz sampling, the improved orthogonal phase measurement method in FPGA to complete high precision phase difference measurement. The paper completes Theoretical analysis and simulation of the transmitting module and receiving module and the hardware design of phase measurement module.The design use ORCAD PSpice A/D software to complete the simulation and improve of laser transmitter and receiver circuit. Using verilog language to achieve the phase measurement software programming, with adding received signal of17.5dB SNR, phase measuring error is not more than0.084°through the simulation. In the actual measurement of hardware circuit, without adding noise, phase measuring accuracy could reach0.0031°...