基于双波长外差干涉的飞秒激光脉冲对准和精密测距方法研究

Using satellite-formation for optical remote sensing　has　extremely high requirements of formation keeping and control.　It has to depend on　wide-range and high-accuracy distance measurement technique based on optical frequency combs. Consider the methods reported in this field, the method based on pulse-to-pulse alignment has an advantage of simple structure, which is suitable for space application. The key point of this method is the accuracy of pulse-to-pulse alignment. The current method for the alignment mainly depends on the peak finding of the envelope of the two pulses overlapped, and the accuracy is not enough for high-accuracy satellite formation. In order to resolve the problem, we propose a method that applying two-color heterodyne interferometry for the pulse-to-pulse alignment and distance measurement using optical frequency combs. The synthetic wavelength is skillfully utilized to bridge the peak finding method and the heterodyne interferometric phase for pulse-to-pulse alignment, so that the accuracy is greatly improved. This method enables tracing the accuracy of pulse-to-pulse alignment and distance measurement to the heterodyne interferometric phase, which can fully utilize the stability of optical frequency comb to realize an accuracy of nanometer level for distance measurement. Therefore it can offer key supports for the high accuracy satellite formation. Moreover, benefitted from the special design of this system, the "dead zone" problem of such kind methods can be resolved.

将卫星编队用于光学遥感，对于其队形保持与控制有极高的要求，需要基于飞秒激光频率梳的大量程、高精度的测距技术作为支撑。其中基于飞秒脉冲对准测距法结构简单，非常适合于空间应用。影响该方法精度的关键因素是脉冲对准的精度。目前的脉冲对准主要依赖于判断脉冲重叠信号的强度极值，易受干扰，并且无法溯源。针对这一问题，本项目提出了一种将双波长外差干涉技术用于飞秒激光频率梳脉冲对准和测距的方法，巧妙地利用合成波长作为桥梁，将外差干涉相位和找极值方法衔接起来用于脉冲对准，能解决找极值法无法直接与单波长干涉相衔接的问题，从而能够大大提高对准精度和测距精度。该方法将脉冲对准精度追溯到外差干涉相位上，因此能充分利用飞秒激光频率梳波长的稳定性，能在较大的量程下实现纳米级的测距精度，从而为高精度卫星编队等应用提供关键技术支撑。同时本项目也通过测距系统的专门设计，能够解决这类方法存在的测量死区问题。

高精度测距作为机械制造和装配中的关键检测技术，在高端装备制造领域有重要的应用。当前精密测距领域的研究重点和热点是光频梳测距，本项目针对光频梳测距中脉冲对准的溯源问题，提出了光频梳外差干涉测距方法，以合成波为桥梁，突破了脉冲极值定位与干涉相位无法衔接的限制，和传统的脉冲极值对准方法相比，精度提升近2个数量级，实现了光频梳脉冲对准的计量溯源。在此基础上，利用脉冲间隔扫描的倍增效应，扩展了测距的动态范围。为了进一步解决测量死区的问题，项目在测距方法上做了延伸，研究了双光梳测距方法。针对双光梳测量系统噪声大的共性问题，提出了同步锁定和自适应补偿的噪声抑制方法，突破了双光梳测量系统纵模无法分辨的限制，在不增加光源锁定复杂性的条件下，提高测距精度超1个数量级。研制的测距系统解决了航天五院508所空间相机部组件稳定性测量的难题，并进一步应用于航天五院总体部合成孔径雷达（SAR）卫星天线展开测量地面验证实验，解决了卫星天线绝对位置和姿态测量的难题。