  To achieve high resolution imaging the standard control algorithm used for
classical adaptive optics (AO) is the simple but efficient
proportional-integral (PI) controller. The goal is to minimize the root mean
square (RMS) error of the residual wave front. However, with the PI controller
one does not reach this minimum. A possibility to achieve is to use Linear
Quadratic Gaussian Control (LQG). In practice, however this control algorithm
still encounters one unexpected problem, leading to the divergence of control
in AO. In this paper we propose a Modified LQG (MLQG) to solve this issue. The
controller is analyzed explicitly. Test in the lab shows strong stability and
high precision compared to the classical control.
