A modified phase diversity diffraction wavefront sensor with a grating

The phase diversity wavefront sensor is one of the tools used to estimate wavefront aberration, and it is often used as a wavefront sensor in adaptive optics systems. However, the performance of the traditional phase diversity wavefront sensor is limited by the accuracy and dynamic ranges of the intensity distribution at the focus and defocus positions of the CCD camera. In this paper, a modified phase diversity wavefront sensor based on a diffraction grating is proposed to improve the ability to measure the wavefront aberration with larger amplitude and higher spatial frequency. The basic principle and the optics construction of the proposed method are also described in detail. The noise propagation property of the proposed method is also analysed by using the numerical simulation method, and comparison between the diffraction grating phase diversity wavefront sensor and the traditional phase diversity wavefront sensor is also made. The simulation results show that the diffraction grating phase diversity wavefront sensor can obviously improve the ability to measure the wavefront aberration, especially the wavefront aberration with larger amplitude and higher spatial frequency.     

大气湍流像差对空间零差二进制相移键控相干光通信误码性能的影响

通过研究不同大气湍流条件下的系统误码率(BER)来说明大气湍流引起的波前畸变给零差二进制相移键控(BPSK)相干光通信系统带来的恶劣影响。结果显示,大气湍流引起的像差可以独立于系统信噪比(SNR)作用于相干光通信系统,导致误码出现。即使在SNR无限大的情况下,当接收光信号的波面峰谷值(PV)大于一个波长后,就容易出现误码;并且随着SNR的降低,对波面PV的要求更加严格。另外,大气湍流引起的光强起伏和相位畸变会导致相干混频效率急剧下降,从而增加系统误码率。     

自适应光学控制系统对Kolmogorov湍流补偿的修正有效带宽

基于时间功率谱反演生成的Kolmogorov湍流时间序列, 模拟分析了自适应光学控制系统跟踪回路与高阶误差校正回路在有限误差-3 dB带宽、 有时间延迟情况下的闭环校正残余误差, 得出了系统的跟踪残余方差、高阶残余方差与误差-3 dB带宽的数值拟合结果, 修正了系统有效带宽的表达式, 使其能更精确地估计校正残余方差. 关键词： Kolmogorov湍流 Tyler频率 Greenwood频率 有效带宽     

死区对四象限跟踪传感器跟踪精度的影响

介绍了四象限跟踪传感器原理后, 分析了存在噪声和死区条件下的四象限探测器的光斑能量探测率、质心探测误差和光斑位移敏感度, 推导了此时四象限跟踪传感器跟踪误差的理论公式, 并通过实验证明了理论分析的正确性. 理论分析和实验的结果都表明, 在相同的噪声情况下, 质心探测误差和位移敏感度都随着光斑的高斯宽度与死区宽度之比减小而增大, 但是位移敏感度增大的趋势要小于质心探测误差增大的趋势, 它们共同作用的结果就导致了光斑的高斯宽度与死区宽度之比越大, 四象限跟踪探测器的跟踪误差越小.     

一种自适应光学系统响应矩阵的直接计算方法

提出了一种自适应光学系统响应矩阵的直接计算方法.通过分析特征驱动器斜率影响向量的实测值与理论值的相关性估计波前校正器与波前探测器的对准误差,得到了更接近实际情况的响应矩阵.实验结果表明,考虑对准误差后计算出的响应矩阵能够有效地进行闭环校正.     

自适应光学系统倾斜校正回路的最优闭环带宽

基于实际自适应光学系统倾斜校正回路最常使用的比例积分控制器,分析了最优闭环带宽与大气湍流、测量噪声之间的关系.利用满足Kolmogorov湍流整体倾斜功率谱密度的时间序列进行了相关的数值仿真.结果表明,根据不同湍流强度及测量噪声选择合适的闭环带宽,可以充分发挥自适应光学系统倾斜校正回路的闭环校正能力,减小闭环残差.     

利用倾斜镜对太阳像作平场处理

提出一种利用高速倾斜反射镜对太阳像进行平场处理的新方法。介绍了此方法的原理和实际工作过程，并给出了实验结果。结果表明，应用高速倾斜反射镜可以非常有效地对太阳像进行平场处理，提高太阳像成像质量。     

基于哈特曼夏克波前探测的图像解卷积:室内结果

在简要介绍哈特曼－夏克波前传感器原理和基于波前传感的目标图像解卷积恢复技术的基础上，分别给出了室内模拟点源和扩展源情况时畸变目标光斑图像解卷积处理的实验结果，结果表明，基于波前探测的图像解卷积事后处理能够有效地对畸变目标图像进行恢复。     

Experimental verification of combinational-deformable-mirror for phase correction

In adaptive optics (AO) system,the phase compensation capability is limited greatly by the actuator num- ber of the deformable mirror (DM).The actuator number of DM is mainly restricted by the manufacture techniques.The spatial correction capability of AO system can be improved by two or more combinational- DMs (CDMs) with conjugation relationship.The CDM AO system for wavefront correction is built,which consists of two 32-element DMs.The experimental results are in agreement with the numerical simulation results.It is indicated that the CDM AO system provides better correction performance than the single 32-element DM AO system.     

Real-time measurement of atmospheric parameters for the 127-element adaptive optics system of 1.8-m telescope

A real-time method for measuring atmospheric parameters based on co-processor field-programmable gate array (FPGA) and main processor digital signal processing (DSP) is proposed for ground-based telescopes with adaptive optics (AO) systems. Coherence length, outer scale, average wind speed, and coherence time are estimated according to closed-loop data on the residual slopes and the corrected voltages of AO systems. This letter introduces the principle and architecture design of the proposed method, which is successfully applied in the 127-element AO system of the 1.8-m telescope of Yunnan Astronomical Observatory. The method enables real-time atmospheric observations with the same object and path of the AO system. This method is also applicable to extended objects.