Research On Key Techniques Of Parallel Laser Range Measurement

Laser ranging has the characterizes of high accuracy, strong anti-jamming capacity and easy operation, and therefore widely used in various technical fields. With the rapid development of the military, medical, construction, and distance technology, the scope of measured object are gradually expanding, which ask for more accurate and faster range finder. The traditional laser rang finder are measuring in the way of point by point with single-beam, which can't meet the high precision and high speed at the same time.The paper is to solve this problem.The commonly used methods include pulse laser rang finding method and the phase laser rand finding method:The former measurement is faster, btut less precise.The latter despite the high accuracy, but the measurement is slow. The paper design a multi-laser parallel range finding system solution using all-digital phase-detect approach, which have advantage of high-precision, high-speed and small-size. Several key technologies of the system are researched in the paper which lay the foundation for further development of the whole rang finding system.With Digital Synthesis (DDS) technology, digital signal processor(DSP) controls multi-DDS chips to output sine signals, whose frequency differences are a few kHz, then load these signals to different lasers separately at the same time, achieve multi-laser parallel modulation and emission; The returned light signals are detected by the same avalanche photodiode. After I/V conversion and amplitude adjusted, the parallel signals are send to the mixer to reduce the frequencies by using the "inalienable phase frequency shift" principle of the mixer. Then the low-frequency ranging signals are carried out by the low-pass filter, complete the parallel demodulation; Next, the demodulated parallel ranging signals and reference signals are synchronous collected by dual-channel, high-precision AD, which is controled by the DSP, and avoid phase error caused by AD acquisition delay. Based on all phase FFT spectrum analysis of phase ranging system for writing parallel software algorithms, can effectively suppress spectral leakage, and non-harmonic sampling phase is still measured accurately, improve the phase accuracy.Papers analysis the factors that affect the accuracy of the parallel ranging system in-depth, including phase shift introduced by nonlinear mixer and filter, phase error caused by quantify of A/D conversion and when the laser beam into the rough surface, the because of the spot caused by separate phase error. Paper through the establishment of appropriate simulation model obtains simulation results, and take the appropriate compensation methods to reduce error, in order to lay the foundation for improving the accuracy of the measuring system further.