飞秒脉冲非对称互相关绝对测距

光学频率梳是一种重复频率与偏置频率锁定的新型光源，在频域上为频率间隔稳定的频率梳齿，在时域上为相对距离稳定的飞秒脉冲激光.光学频率梳在测距中的应用广泛，能够实现远距离高精度的测量.本实验使用飞秒激光脉冲作为光源，基于谐振腔扫描光学采样测距原理得到非对称的互相关干涉条纹，实现了远距离高精度的绝对测距.非对称互相关条纹可通过色散补偿与调节光学频率梳的重复频率得到，并通过得到的非对称的互相关干涉条纹对测距结果进行补偿.实验结果表明测距系统能够实现在50 m范围内误差为2 μm的绝对测距，测量相对误差为1.9×10^-7.

Absolute distance measurement based on asymmetric cross-correlation of femtosecond pulse

Optical frequency comb is a kind of new pulse source, whose repetition rate and phase are locked. Optical frequency comb plays an important role in absolute distance measurement and time-frequency metrology. Lots of laser ranging methods such as time-of-flight and multi-heterodyne interferometry based on femtosecond laser pulse have been used in distance measurement. In this paper, a high-precision distance measurement system based on optical sampling by cavity tuning is set up to realize a long absolute distance measurement. And a kind of error compensation method is proposed based on the asymmetric cross-correlation patterns. In traditional optical sampling by cavity tuning measurement system, the fiber link is inserted into the reference path to extend the non-ambiguity distance, which does not have a good performance in arbitrary distance measurement. In our system, we use a 116-meter-long fiber which is inserted into the measuring path to extend the non-ambiguity distance. Besides, dispersion compensation technique is used to control the shape of the laser pulse. An asymmetric optical pulse is used as the light source, so that we can obtain extremely asymmetric cross-correlation patterns. The cross-correlation patterns can be acquired by sweeping the repetition frequency. We use an arbitrary waveform generator to provide the scanning voltage, and the scanning voltage can adjust the repetition rate of the pulse and has a frequency of 1 Hz. There will be two peaks on the envelope of cross-correlation pattern, and both peaks can be used to obtain the distance information. When the laser propagates in vacuum and the system is stabilized, the distance between these two peaks is constant, and we can use this distance to obtain the important factor N, which is used to describe the number of the pulse. As a result, we can realize absolute distance measurement without the help of other measurement systems. However, due to the dispersion of the medium, the distance between these two peaks is not constant, which means that the asymmetry of the cross-correlation patterns in dispersion medium will influence the measurement results. And the deviation is relevant to the peak-to-peak distance. We use the difference among the peak-to-peak distances at different positions to correct the measurement results. A comparison of our results with those from a commercial He-Ne laser interferometer shows that they are in agreement within 2 μm over 50 m distance, corresponding to a relative precision of 1.9×10^-7.