用于液晶自适应可见光高分辨率成像系统的相位差图像重建技术研究

The large aperture telescope with adaptive optics system is one of the most important ways to observe space objects, which is used widely for military and astronomy such as distinguishing and surveillance of satellites and remains. However, due to the atmosphere turbulence the resolution of large aperture telescope can only reach the level of 20-centimeter telescope. Traditional adaptive optics system is limited by the actuator number of deformable mirror. The liquid crystal adaptive system has large number of actuators, but it still cannot perform diffraction limited imaging due to other limitations. The phase diversity technique can be used to remove the residual wavefront errors from the image after adaptive system and improve the resolution further. But the phase diversity technique has never been used in the liquid crystal adaptive optics system before and there are many problems need to be studied. In this project, we will propose a new optical system and phase diversity function applying strategy according to the special characters of liquid crystal adaptive system. All the problems introduced by liquid crystal adaptive system will be solved and the variable phase diversity function will also be realized. The accuracy and convergence of phase reconstruction will be improved. The liquid crystal adaptive system with phase diversity technique will be accomplished and experiments will be performed on the 2-meter aperture telescope. This work will improve the progress of diffraction limited visible light imaging on large aperture telescope, especially for the oncoming 12-meter telescope of our country. All of these are very important and valuable for the space defense and astronomy research of our country.

带有自适应光学系统的大口径望远镜是观测空间目标最重要的工具之一，被广泛用于人造卫星编目、空间碎片监视以及天文研究等领域。传统自适应光学技术受限于变形镜驱动单元少，液晶自适应技术虽然突破了单元数限制，但受限于响应速度，成像分辨率依然无法达到衍射极限。本项目拟将相位差图像重建技术与液晶自适应技术相结合，使大口径望远镜可见光波段成像分辨率达到衍射极限。将针对一系列相位差技术在液晶自适应系统中所特有的问题进行研究，提出新型光学系统和相位差函数施加方式，解决液晶“零级光”问题，实现相位差函数随时可变并降低噪声带来的影响，实现具有相位差图像重建技术的液晶自适应可见光高分辨率成像系统，并在2米口径望远镜上进行实验验证。本项目工作能够实现大口径望远镜在可见光波段进行衍射极限分辨率的成像，尤其对于我国即将开工建设的12米望远镜迫切需要该类技术，在我国空间防卫以及天文研究等领域具有重要且现实的科学及应用价值。

带有自适应光学系统的大口径望远镜是观测空间目标最重要的工具之一，被广泛用于人造卫星编目、空间碎片监视以及天文研究等领域。传统自适应光学技术受限于变形镜驱动单元少，液晶自适应技术虽然突破了单元数限制，但受限于响应速度等问题，成像分辨率依然存在进一步提高的空间。本项目将相位差图像重建技术引入液晶自适应技术中，成功将二者相结合，率先实现了可用于大口径望远镜的具有相位差重建技术的液晶自适应可见光波段高分辨率成像系统，使大口径望远镜可见光波段成像分辨率得到了进一步提高。针对一系列相位差技术在液晶自适应系统中所特有的问题进行了系统研究，提出了全新的双校正器独立调制液晶自适应光学系统，采用了全新的相位差函数施加方式和系统运行模式，解决了液晶系统中的“零级光”问题，使波前重建误差较传统方法降低了50%。同时建立了与液晶自适应系统相符合的相位差重建技术数学模型，模拟分析了不同的相位差函数对系统收敛性和精度的影响，并进行实验验证，优化了相位差重建技术关键参数的选择。提出了基于BM3D的相位差图像重建降噪方法，使低信噪比下波前重建误差降低了40%，图像结构相似度从50%提高到90%。相关系统在2米望远镜上进行了观测试验验证，实测图像分辨率在自适应校正基础上提高了0.25角秒。本项目所取得的研究成果不仅有希望满足10米级大口径望远镜可见光波段高分辨率自适应成像的需求，解决高速和暗弱空间目标在可见光波段高分辨率成像的问题，服务于我国空间目标的监视与识别的国防及天文学应用需求，尤其是对于我国已经开工建设的12米口径望远镜具有更现实的应用价值。同时该技术也可应用于激光通讯、激光武器、自适应光学显微镜等其他领域，具有较高的实际应用价值。