The Research Of Modulation And Demodulation Technology In Array Laser Range Measurement System

Laser ranging has been widely used as a non-contact measurement in the field of remote sensing, precision measurement, construction, secure monitoring and intelligent monitoring, involving a multi-disciplinary technology. The existing laser ranging techniques are all used for point by point measurement can not meet the requirement of large measurement range, high accuracy, fast measurement, and so on. The laser ranging system in this article each can measure the distances of object by array measurements. Modulation and demodulation technique is the key of this system, the method of laser modulation and demodulation directly affects the measurement accuracy and the complexity of hardware. So this article will introduce the array laser ranging system at the same time to do research to modulation and demodulation techniques which suitable for array laser ranging system, and give its implementation of the hardware.Array laser ranging system is the phase laser ranging system using multi-channel frequency division multiplexing realized by different frequency modulation signal modulated lasers. The multi-channel frequency modulated wave signal produced by hardware circuit driving multiple semiconductor lasers emit laser, and returned light from the object surface mixed the light of multi-channel modulation, Use the same APD to receive the mixed light and convert it to a voltage signal, then send it to the DSP for phasing acquisition by AD after processed of amplified, mixed, filtered and so on. The system use phasing instead of the traditional FFT phasing method in order to eliminate the phase measurement error easily caused by spectral leakage and "synchronous sampling". We can get an accurate phase information directly taken the phase corresponding to the spectrum value on the main spectrum lines after phasing by all phase FFT. And then calculate the distances of the different measurement points according to the phase values, which is the principle of the array ranging system. In the modem part, this paper use square wave and sine wave modulation, analyzing square wave and sine wave modulation by simulation, giving its hardware circuit and then compare the complexity and accuracy to come up with a more effective modulation and demodulation.Finally, the article analysis the factors of the array ranging system, giving the influencing to phase caused by mixing, filtering and amplification, and propose appropriate improvements through experimental and simulation results show that the system technically is feasible, lay a solid technical foundation for its future developing.