Absolute Distance Measurement Method Usingfrequency-sweeping Based On Current Modulation

High-accuracy absolute distance measurement has importance theoretical value and practical significance in the field of measurement science and industrial application. In view of this, based on the Michelson interference principle, a current modulated absolute distance measurement system with compensation is designed. In order to achieve the absolute distance measurement, the system scanns the frequency of semiconductor laser which changes with the injected current. In this paper, the main study includes the measuring principle, the design of hardware circuit, data processing algorithm and so on, the specific research content as follows:Firstly, a absolute distance measurement system is designed based on the Michelson interference principle. The system adopts frequency scanned method based on current modulation, and a comparing optical path and a measuring optical path are used to measure synchronously. The two interference signals are converted into electrical signals by two photodetectors, and are used as input signals for absolute distance calculation. The current modulation characteristics of semiconductor laser is introduced. The semiconductor laser driver laser is designed. The measurement principle of this measurement system is discussed.Secondly, a signal processing algorithm is designed for the absolute distance measurement system performed with frequency-sweeping interferometry. The algorithm uses the zero position of the signal to extract the period or frequency of the signal. The characters of interference signals are presented, the difference smoothing convolution is used for processing the signals twice, absolute distance is determined by the period or frequency information extracted from interference signals produced while scanning the laser frequency. Meanwhile, the period calculating error of this algorithm is analyzed.Thirdly, in order to realize the data acquisition, multi-channel data acquisition program is designed. The photoelectric conversion circuit is designed to conevert the light signal to electrical signal. This lay the foundation for the experimental data acquisition. The corresponding filter algorithm is designed to filter the signal.Finally, the experimental data is processed by the signal processing algorithm which uses the zero position of the signal to extract the period or frequency of the signal. The experimental results of the measurement system is compared with the experimental results of the double-frequency laser interferometer. The experiment results demonstrate that this method has major computing advantages and this system has good stability and repeatability. At the same time, the error of the experimental results is analyzed.