利用变形反射镜和激光导星扩大校正视场

Extending corrected view of field using deformable mirrors and laser guide stars

为了扩大自适应光学(AO)系统的校正视场,在主要湍流层的共轭面上设置两个变形反射镜(DM),即采用分层共轭自适应光学(MCAO)的方法。主湍流层的共轭面位置设置两个变形反射镜和激光导星可以将湍流层上不同高度位置产生的波前畸变进行分离,并使焦距非等晕性几乎完全消除。在自适应光学系统中,角度的非等晕性产生的波前误差主要取决于校正的模式数、大气介质折射率结构常数(Cn2)的分布和系统的几何尺寸。结果表明:对于孔径为3.5m的望远镜,利用两个变形反射镜能够达到3弧分的校正视场。

In order to increase the corrected field of view （FOV）of an adaptive optics （AO） system, two deformable mirrors （DMs） were placed on the conjugate planes of the dominant turbulent layers, namely applying the method of multi-conjugate adaptive optics （MCAO）. The wavefront distortions in different altitudes could be separated by two deformable mirrors and laser guide stars placed on the conjugate place of the dominant turbulence layer and total anisoplanatism of the focal length was completely eliminated. The wavefront error caused by angular anisoplanatism in a MCAO system depended on the number of corrected modes, the profile of structure constant of atmosphere refractive index Cn^2 and the system geometry. A new approach of calculating the anisoplanatism by using spatial correlation functions of Zernike modes was presented. The results show that a corrected field of view of three arc minutes can be achieved by the setup consisting of two deformable mirrors with the Calar Alto 3.5 m telescope.