Research On Improved Phase-shift Laser Range Finder

A laser range sensor used to obstacle detection in construction machinery is designed. The phase-shift laser range is applied to the system, and the method includes dual-frequency modulation, difference-frequency, Fast Fourier Transform (FFT) and so on. The hardware detection circuit and program of laser range are completed, and some improved circuits and slip average method are applied. Besides, the cause of error is discussed. The whole detection circuits have the advantages of high integration and simpleness. The ranging accuracy has reached centimeter magnitude. The research includes these following sections:1. Commonly used methods of range are analyzed, and the phase-shift laser range is chose to detect obstacles. According to method and requirement of the ranging system, overall measurement solutions are determined.2. According to the power equation and error analysis of phase-shift laser ranging system, the feasibility of range sensor without cooperation target to achieve the target range and accuracy is demonstrated.3. According to the measurement program, the laser modulation and transmitter circuit, the laser receiver circuit, the measurement circuit of phase and communication circuit are designed. The waveforms and the key parameters are analyzed, and appropriate chips and circuits are selected to achieve ranging.4. The method based on difference-frequency and FFT is used to measure the phase-shift between transmitter and receiver. The program of controlling Direct Digital Synthesizer (DDS), controlling analog switches, A/D acquisition, data processing, and CAN bus communication are written. In order to improve the accuracy of phase measurement, the method of silding is used to get the average value.5. The experiment of phase measurement based on FFT is finished. The experiment of range measurement is finished. The data of measurement is analyzed.