合成孔径激光成像雷达散斑效应分辨单元成像研究

分析了合成孔径激光成像雷达(SAIL)受散斑效应影响的分辨单元成像过程并推导了含有散斑效应的二维数据收集方程。在此基础上通过数值模拟分析比较了不同接收天线尺寸、不同天线积分起点位置情况下散斑效应对成像所需的光电流交流项、距离向压缩和最终分辨单元成像结果的影响。结果表明散斑效应对分辨单元成像的影响主要体现在降低了分辨单元的图像强度,同时不同天线尺寸和天线积分位置对分辨单元的成像影响差异较大。分析结果可为今后SAIL散斑效应的抑制提供一定的参考。     

Research on wavefront error of prism induced by thermoelastic distortion

To meet the design and usage requirements of the precision light beam scanner, the thermoelastic distortion of prism is detailedly analyzed by the thermal-structure coupling method, the influence of which, on the surface deformations of prism, is conclusively proved far greater than that of only the gravity load without temperature fluctuation. With the temperature fluctuation from 20 to 20.5 ℃, the strains as well as the stresses appropriately eightfold increase, which right accords with the actual results measured by Zygo Mark interferometer with the error of not over 10%. Therefore some strict temperature-controlled measures are necessary for the scanner.     

Variation of the absorption and dispersion profiles in a ladder-four-level system

A theoretical research on the variation of the absorption and dispersion profiles and population distribution of each level in a ladder-four-level system driven by two coherent fields has been made. Whether the variation occurs or not depends on the effect of quantum interference, the detuning of the upper coherent field and the separation of the two intermediate levels. A dressed-state analysis is introduced to explain the numerical results.     

复振幅光瞳滤波器的三维超分辨性能研究

超分辨技术中现有的纯振幅型或纯相位型光瞳滤波器,大部分只能实现轴向或横向超分辨而不能实现三维超分辨,三维超分辨在三维成像系统中有着重要的作用。因此为提高成像系统中的三维分辨能力,设计了一种复振幅光瞳滤波器,并对其三维超分辨性能进行了研究。详细分析了该光瞳滤波器的第一区半径和透射率对施特雷尔比、轴向和横向超分辨因子以及旁瓣能量的影响。通过一系列的模拟证明,借助于复振幅光瞳滤波器可以实现三维超分辨。该滤波器的优点是容易实现三维超分辨,且有比较高的施特雷尔比,缺点是三维超分辨的实现总是伴随着旁瓣能量的增加,但可以采用共焦扫描成像系统来加以抑制。     

菲涅耳望远镜合成孔径激光成像雷达实验室验证

对菲涅耳望远镜合成孔径激光成像雷达进行了实验室尺度条件下的原理验证实验。实验中利用不同曲率半径、垂直正交偏振的两个球面波通过二维(2D)扫描方式照明远距离处的目标,接收望远镜接收到的目标回波经过偏振分光镜分成两束作为信号光和本振光进入2×4 90°桥接器,桥接器输出的四路光信号被两个平衡探测器接收,平衡探测器输出电信号经模数转换后经过复数化、两维相位二次项匹配滤波算法处理后可以重构出目标图像。对4.3m处点目标和2D面目标进行了成像实验,取得了具有良好成像分辨率和对比度且带有散斑效应的预期成像结果,证明了该合成成像激光雷达概念的正确性。     

直视合成孔径激光雷达自补偿高速空间波前调制器

提出了一种直视合成孔径激光雷达的高速空间相位调制方法。将一束空间偏振光束分为两束同轴同心且正交偏振的光束。在交轨向,将两个光束调制成随时间正弦变化且变化方向相反的空间相位;在顺轨向,将两束光调制成具有符号相反曲率半径的相位,在慢时间轴上产生与目标顺轨向位置有关的空间二次项相位历程。此种调制方法,在顺轨向具有自动补偿抖动的功能,可以有效地防止平台抖动对成像的影响。     

Analysis of detection error for spot position in fiber nutation model

The influences of nutation trail accuracy,simplification of coupling model,spot position jitter,and power variation of incident light on the detection error are analyzed theoretically.Under the condition of satisfying the requirements,the nutation radius is less than 1.13μm,the accuracy of the nutation trail is less than 0.04μm,and the detection range is[?5μm,+5μm].The nutation frequency is 160 times spot position jitter frequency and 100 times intensity jitter frequency of incident light.The analysis is of great significance for determining nutation radius and frequency in the tracking system based on fiber nutation.     

多体制兼容相干探测卫星激光通信技术

卫星相干激光通信系统中,信号调制格式以相移键控(PSK)为主,未兼容开关键控(OOK)的相干接收。针对卫星相干光通信接收机不兼容多种调制格式的问题,实验搭建了兼容OOK以及二进制相移键控(BPSK)的相干通信接收装置。在1 Gbit/s的通信速率下,当调制格式为OOK且信号光功率为-54.6 dBm时,误码率(BER)为10^-3,接收灵敏度距离散粒噪声极限3.3 dB;当调制格式为BPSK且信号光功率为-57.95 dBm时,BER为10^-3,接收灵敏度距离散粒噪声极限4.2 dB。该多体制兼容相干接收机的结构与当前大多数相干接收机的硬件通用,且具有较高的接收灵敏度,证明了卫星相干激光通信多体制兼容技术的可行性,具有重要意义。     

Direct phase control method for binary phase-shift keying space coherent laser communication

An optical phase locking method based on direct phase control is proposed. The core of this method is to synchronize the carrier by directly changing the phase of the local beam. The corresponding experimental device and the supporting algorithm were configured to verify the feasibility of this method. Phase locking can be completed without cycle skipping, and the acquisition time is 530 ns. Without an optical preamplifier, a sensitivity of-34.4 d Bm is obtained, and the bit error rate is10^...     

远距离激光成像雷达进展

远距离激光成像雷达在军事侦察和空间监视等领域应用广泛.介绍了几种不同类型远距离激光成像雷达的基本原理,给出几种不同类型的远距离激光成像雷达,并指出了激光成像雷达的发展趋势.