【作者】 余浩；

【导师】 姜文汉； 饶长辉；

【作者基本信息】 国防科学技术大学 ， 光学工程， 2010， 博士

【摘要】 自适应光学是一种实时测量与像差校正的技术,它适用于大气补偿即校正光在通过大气传输时产生的像差。传统的自适应光学是应用单变形镜补偿光束的相位畸变为主,而最有效的补偿为对相位畸变和振幅畸变的全场补偿,双变形镜自适应光学系统是实现全场补偿的技术之一。本文以自适应光学理论为基础,利用现有变形镜器件,提出利用双变形镜系统同时对光束的振幅畸变和相位畸变进行补偿,在实验上验证了基于双变形镜的全场补偿自适应光学技术的可行性。论文对双变形镜全场补偿的自适应光学技术原理、技术特点和应用前景进行了理论和实验研究。本文围绕双变形镜全场补偿自适应光学理论,利用相位型液晶空间光调制器(LC-SLM)作为变形镜,按照对光束近场场强控制方法的研究、双变形镜自适应光学系统验证性实验、双变形镜闭环自适应光学系统的实现这样一条主线展开研究,目的在于验证双变形镜自适应光学技术在全场补偿中的可行性。本文首先介绍了自适应光学系统在激光发射系统中的补偿应用,通过仿真模拟了传统单变形镜自适应系统补偿光束相位畸变的校正效果,结果表明单纯的相位补偿并不能使光束畸变得到完全校正,尤其当光束传输距离较远、出射孔径较小、大气扰动强的情况下校正效果并不理想。根据双变形镜自适应光学理论,对光束的振幅和相位畸变同时进行校正,仿真结果证明,畸变光束经过全场补偿后,近场场强得到更好改善,远场焦斑分布更接近衍射极限。其次,在双变形镜自适应光学系统中要求利用探测到的波前畸变信息对变形镜进行控制,其中如何利用探测到的场强信息获得变形镜所需位相是关键技术之一,从而对光束的近场场强进行校正。本文在传统的G-S算法的基础上提出一种相位迭代算法,利用已知激光的出射振幅分布和近场接收平面上需要达到的振幅分布,在光束传输过程中反复相位迭代得到出射场所需的相位信息,然后通过控制变形镜得到该相位,使光束的近场场强分布与所要求的理想场强分布接近,从而达到对光束近场场强的控制。首次设计了一套基于G-S算法的自适应光学系统,对光束近场场强进行控制,并在实验上取得良好效果。再次,在全场补偿理论中,主激光到达第二块变形镜时,振幅分布与信标光一致,相位共轭,根据光路可逆与相位共轭原理,主激光达到目标时的场强分布将与信标光一致。为验证光路可逆与相位共轭原理,提出一种基于该原理,利用自适应光学技术控制光束近场场强的方法,并率先进行了实验研究。仿真和实验结果表明,利用该系统可以实现对光束近场场强的控制,使光束质量得到改善。通过该实验系统首次验证了双变形镜自适应光学系统对光束近场场强控制的可行性。此外,本文设计了一套原理性实验系统对双变形镜技术的校正能力进行验证。实验中没有信标光,而是利用已知信息的像差板,计算出两块变形镜所需的变形量,对主激光进行调制。实现了利用双变形镜对静态畸变波前进行全场校正的实验,对比研究了双变形镜和单变形镜对波前的空间校正能力,并验证了双变形镜全场校正的有效性,显示出了双变形镜全场补偿用于自适应光学系统波前校正的优势。最后,根据双变形镜技术对光束全场补偿的理论,本文首次搭建了一套双变形镜闭环实验系统,利用探测到的信标光畸变信息分别对两个变形镜进行控制。利用CCD探测到的振幅畸变迭代出第一个变形镜所需加的面形,利用哈特曼传感器探测到的相位畸变控制第二个变形镜,实现了对波前振幅和相位畸变全场补偿的实时闭环控制。仿真和实验结果表明,通过首套双变形镜自适应光学系统的全场补偿,畸变光波的近场场强和远场焦斑都得到了更好的校正。本文的研究结果为双变形镜自适应光学系统的实际应用提供一定的理论参考和工程应用经验。更多还原

【Abstract】 Adaptive optics (AO) is a real-time measurement and aberration correction technology, which applies to compensating the aberration of beam when it propagating the atmospherc turbulence. Traditional adaptive optics is to use a single deformable mirror (DM) compensation for the beam phase distortion. The more effective compensation is correcting the amplitude and phase distortion synchronously. A proposed method to compensate for amplitude and phase distortion is the use of two DMs. In this paper, we study the AO theory and use the existing DM devices to design the two DMs AO system. This system can compensate the distortion of amplitude and phase for beam. In the experiment we achieve this full compensation technology. The principles, the characters and application prospect of the two DMs AO system are studied by theoretic analysis and experimental verification.This paper is devoted to the principles of two DMs AO system, using of phase-type liquid crystal spatial light modulator (LC-SLM) as a DM. Accordance with correction near-field intensity of beam, validation of DMs AO system in experiment and realization of the closed-loop experiment to conduct the feasibility of full compensation in two DMs AO system.First, the AO system to compensate for laser system application is introduced. The simulation of tranditional single DM AO system compensating phase distortion is analyzed. Result shows that the only pahse compensation can not make the beam distortion fully corrected, especially when the beam propagation is so distance, out of radio aperture is so small and the atmospheric disturbance is so strong. According to the two DMs AO theory, the beam amplitude and phase distortion is corrected at the same time. Simulation results show that laser beams through the full compensation, the quality of laser beam in the near field intensity is improved and the far field image is close to diffraction limit.Second, in the two DMs AO system, the intensity and phase of the beacon beam reaching the transmitting system can be detected by the detectors, and then the measured results are used to control two DMs. The key technique is to determine the required phase of DM1, thus the near-field intensity of beam is corrected. The phase-iterative algorithm based on the traditional algorithm G-S algorithm is presented. This algorithm is using the emitted laser known amplitude distribution and the near-field receiving plane needed amplitude distribution to iterate the phase of beam. We can control the DM to give the beam this pahse, so that the beam near-field distribution is close to the requirements of the ideal field distribution, so as to achieve the control of near-field intensity of the beam. The AO system based on G-S algorithm to control the near-field intensity of the beam is designed for the first time, and experiments with good results.Again, in the full compensation theory, when the laser reaching the second DM, the amplitude distribution is according to beacon and phase conjugation. In optical reversion and phase conjugation principle, the primary laser to target the field distribution will beacon unanimously. According to the principle of optical reversion and phase conjugation, the method based on AO technology to control beam near-field intensity is proposed, and the first experimental study is carried out. Simulation and experimental results show that the system can realize the control of near-field intensity, so that the beam quality is improved. The experimental system verifies the feasibility of the two DMs AO system to improve the near-field intensity of beam for the first time.In addition, a schematic experiment of the two DMs AO system is designed to verify the ability of full compensation. In experiment has no beacon, but from the available aberration plate information we can calculate the required deformation of twoDMs.The ability of compensation between two DMs and single DM is compareted, showing the advantage of full compensation using two DMs for adaptive optics wavefront correction.Finally, based on the theory of full compensation using two DMs, we design a set of two DMs AO closed-loop system for the first time. The intensity and phase of the beacon beam can be detected by the detectors, and then the measured results are used to control two DMs. We can use CCD to detect the amplitude distortion and iterate the required phase for DM1, use Hartmann sensor to detect the phase distortion and control DM2. The system can correct the distortion of phase and amplitude at the same time in closed-loop control. Simulation and experimental results show that, through the first set of two DMs AO system the fully compensation is effective. The quality of laser beam in the near field is improved and the far field image is close to diffraction limit in the experiment. This dissertation will provide some reference and experience for the two DMs AO system in practical application.更多还原