激光外差探测中基于遗传算法和序列移位的相位补偿方法研究

The technology of laser heterodyne detection has been widely applied in military and civilian fields. Spatial distortion phase and temporal random phase seriously decrease the signal-to-noise ratio of a heterodyne system. For the spatial distortion phase, the existing method needs a wavefront sensor to measure the distortion phase and compensate the phase by use of a wavefront corrector. For the temporal random phase, an extra optical path is needed to sample transmitter pulse, and it is necessary to measure the temporal random phase. So, the compensation methods have some shortcomings such as complex system and difficulty of realization. In order to overcome these shortcomings, we carry out the research on phase compensation theory and new technology. A new method based on sequence shifting and genetic algorithm is proposed to compensate for temporal random phase. In the method, there are no needs of sampling the transmitter pulse and measuring the random phase, so it is easy to realize. For spatial distortion phase, we propose to use an array detector to convert the issue of spatial phase compensation into how to realize the equiphase superimposition of the output signals of all detection elements. In this case, the new method can effectively compensate for the spatial distortion phase, and the wavefront sensor and corrector are omitted, which greatly simplifies the system. This topic mainly studies the relationships among the spatial resolution of the array detector, the time resolution of the sampling sequence and the compensation performance. How to efficiently find out the shifting steps by genetic algorithm will also be studied in this topic. In additon, experimental works will be conducted for verifying the performance of the new method. The study works in this topic will provide a new phase compensation method which has a simple system. In some application field, our work has an important value especially in airborne and spaceborne.

激光外差探测技术在军事和民用领域都有广泛应用。空间畸变相位和时间随机相位严重降低外差系统信噪比。针对空间畸变相位，现有的相位补偿技术需要波前传感器对其测量，并用校正器进行补偿；针对时间随机相位，需要额外的光路取样发射脉冲，然后测量随机相位，因此都存在系统复杂、实现困难等问题。为此本课题开展相位补偿理论和新技术研究，提出基于遗传算法和序列移位的新方法补偿时间随机相位，新方法无需测量随机相位，易于实现；提出利用阵列探测器将空间畸变相位的补偿问题，转化为探测单元信号的等相位叠加问题，新方法对畸变相位同样有效，并省略了波前传感器和校正器，极大地简化了系统。课题研究阵列探测器空间分辨率、采样序列时间分辨率和相位补偿性能的关系；研究遗传算法高效求解移位步数相关问题；开展新方法的实验验证工作。本课题将提供一种系统简单的相位补偿方法，这在严格限制系统重量、体积的领域，如机载、星载背景下，尤其具有重要意义。

激光外差探测技术己被广泛应用于各种重要行业。在军事领域，这种技术可以实现卫星跟踪、真假弹头识别、激光相干通信、地雷探测等；在民用领域可用于大气风廓线探测、飞机尾流探测、机械振动测量、相位测量等。但空间畸变相位和时间随机相位能减弱探测器输出的外差信号强度，降低信噪比。针对空间畸变相位和时间随机相位的补偿技术存在系统复杂、成本高、或难以实现等问题。本课题开展新型相位补偿的理论和技术研究，首先提出利用遗传算法和序列移位的组合，实现空间畸变相位和时间随机相位的补偿。提出利用阵列探测器将空间畸变相位的补偿问题，转化为探测单元信号的等相位叠加问题，新方法对畸变相位同样有效，并省略了波前传感器和校正器，极大地简化了系统。课题组通过研究，在初始方案的基础上，进一步提出了用自相关运算实现探测单元输出信号的等相位叠加，以此补偿空间畸变相位。与先前提出的基于优化迭代算法的补偿方法相比，该方法无需迭代搜寻，极大地提高了处理效率，使得该方法具有实时性，也避免了优化算法引起的虚警现象。基于新的等相位处理方案，课题研究了以下主要内容（1）通过理论分析，对比研究了单点探测系统和阵列系统的自相关处理后的信噪比情况；（2）研究了不同中频信号带宽情况下，自相关等相位处理算法的区别；（3）研究了阵列探测器不同阵列单元数以及不同相位畸变情况下，新方案的外差探测性能；（4）理论数值计数和实验研究表明，新方案中基于自相关算法的等相位叠加方法，在不同空间畸变程度下，都能将外差探测信噪比提高数十dB。本项目的研究结果提供了一种行之有效的相位补偿方法，从而改善和促进激光外差探测的性能。本项目的成果在军事领域，尤其是严格限制系统重量、体积的领域，如机载、星载背景下，尤其具有重要意义。