We present details of a MEMS-based holographic adaptive optics system. The modal wavefront sensing relies on
measuring the intensity of focal spots using a multiplexed hologram and multi-pixel photon counter. The basis set for the
sensing is a direct recording of the actuator responses in the deformable mirror. This allows us to directly control the
wavefront correction in closed loop without need for any calculations or computer. The entire system is compact and
lightweight and the limiting speed is set only by the dynamics of the deformable mirror and not the number of actuators.