Research On The Combination System Of Pulse-Phase Laser Ranging

As the laser has the advantages of high brightness, good monochromaticity, good directivity and coherence, laser ranging technology has not only become an important technology for space exploration, but also been generalised in the field of land surveying, vibration detection and liquid level measurement. The most commonly used laser range finders are the pulse type and the phase type at present. Phase laser rangefinder is limited to the application in the high precision and short-distance measurement. Pulse laser range finder is limited to the application in the long-distance and low precision measurement.A pulse-phase laser ranging system combined the advantages of these two type system is researched to improve the measurement performance.This thesis gives an overview of the research status of the laser ranging technology at home and abroad, and four kinds of commonly used laser ranging technique are introduced. A specific method of a combination of the pulse measurement and phase measurement is put forward. The overall scheme of the laser ranging system is drafted. This system is divided into four module, including the signal generating module, signal receiving module, mixing module and phase detection module. The schematic diagram and software implementation of each module is completed.15 MHz pulse signal and 14.99 MHz sinusoidal signal are generated in the signal generating module.15 MHz optical signal is converted to electrical pulse signal in the signal generating module. The differential frequency processing of the initial pulse signal and the echo pulse signal, respectively, with the intrinsic signal are done in the mixing module. And two 10 KHz cosine signals are obtained in this module. The acquisition and processing of the signals are completed in the phase detection module. And the measurement results are displayed by LCD in this module.The Cauer filter in the signal generating module, the high voltage generating circuit and voltage comparison circuit in the signal receiving module, the low-pass filter in the mixing module and the CIC filter in the phase detection module are stimulated. According to the results, the noise of the output signal of the DDS can be filtered by the Cauer filter. A 10.3 KHz pulse signal of 87.5% duty cycle can be output by the NE555 clock chip. The 149.02 V DC high voltage can be generated by the high voltage generating circuit. The 10 KHz target signal is obtained by the low-pass filter in the mixing module. The frequency-doubling signal generated by the mixer can be well filtered.The experiment of the high voltage generating circuit is completed. And the testing experiment of the phase detection module directly connected to the signal generating module is conducted. According to the results, a stable control pulse is generated by the NE555 clock chip. The output DC voltage of the circuit can achieve 145 V. The maximum systematic error of the signal generating module and phase detection module is approximately 0.94 mm. According to the systematic error analysis, the improved methods, such as electromagnetic shielding cover in the high voltage generating circuit, and a phase compensation circuit in the signal receiving module are proposed.