基于飞秒激光纵模间拍信号的高精度绝对距离测量

High Precision Absolute Distance Measurement Based on Beat Signal Between Longitudinal Modes of Femtosecond Laser

针对使用单一频率飞秒激光纵模间拍信号测距时测量分辨力和最大非模糊距离之间的矛盾,提出了一种同时使用不同频率的微波信号对距离进行测量并逐级合成测量结果的方法。分别选取频率为100 MHz和1GHz的纵模间拍信号测量目标距离,之后调整飞秒激光器的重复频率,使1GHz的纵模间拍信号频率变化1 MHz后再次测量,借助频率变化进一步得到更大的合成波长,最后将三次测量的结果逐级合成,在扩展最大非模糊距离的同时保证了测量结果的高精度。实验结果表明,这种方法能够将最大非模糊距离扩展到150m,对目标绝对距离的测量结果不确定度为25.8μm。该方法不需要改变光路结构,测量过程简便,能很好地实现大尺寸高精度的绝对距离测量。

The increasing of measurement resolution leads to the shortening of non-ambiguity range during the distance measurement with the beat signal between longitudinal modes of femtosecond laser. A method for measuring distance by using microwave signals of different frequencies simultaneously and synthesis of measurement results is proposed in this paper. Firstly, the longitudinal beat signals of frequency 100 MHz and 1 GHz are selected to measure the target distance respectively. Then, the repetition frequency of the femtosecond laser is adjusted so that the frequency of the longitudinal mode beat signal of 1 GHz is changed 1 MHz. After measuring with the variation frequency, a longer synthetic wavelength is obtained. By synthesis of the measurement results, the non-ambiguity range is enlarged without reducing the measurement resolution. The experimental results show that the non-ambiguity range achieves 150 m while the uncertainty of the absolute distance of the target is 25. 8μm. The structure of the optical path and measurement process is simple in the present method, and it can realize high accuracy absolute distance measurement in large scale.