基于二次偏振调制的变频测距方法与系统实现

由于鉴相精度限制、电路等引入的附加相移干扰等因素,传统相位测距技术精度的提高受到了限制.采用二次偏振调制技术对相位测距技术进行了改进.利用二次偏振调制方法能够直接在相位调制器上对两次调制信号的相位差进行解调,大幅度简化了系统的复杂程度.采用变频方法替代传统的鉴相方法,从而系统的测量精度不再受鉴相问题的困扰.从理论上得到系统输出光强与调制频率成正余弦关系,并进行了实验验证.基于变频测距的实验中,系统频率的稳定度优于10-6,测量精度可以达到±10.6μm(被测距离为4.5 m).并对一段长200 m的光纤进行了实际测量,得到了清晰的调制频率与系统输出光强的曲线.

Variable frequency range finding technology based on double polarization modulation method and system implementation

Traditional laser range technology has a poor phase measurement accuracy and an additional phase of the system, which restricts the improvement of its accuracy. In this article, by using the technology of variable frequency measurement based on double polarization modulation the phase shift range-finding technology is improved. With the method of double polarization modulation, the demodulation of the phase information is directly implemented on the phase modulator, which can make the system simpler. The variable frequency technology is used to replace the traditional phase discrimination technology; therefore the measurement accuracy of the system will not be persecuted with the phase crimination any more. The theoretical curve of sine (cosine) relation between modulation frequency and output light intensity is proved experimentally. Owing to the fact that the stability of frequency can be better than 10^-6, the measurement accuracy can reach ±10.6 u m@4.5 m. By using this system to measuring a 200 m-long fiber, the clear curve of modulation frequency versus output of system is obtained.
Keywords：laser distance measurementvariable frequency distance measurementdouble polarization modulation