High signal-to-noise ratio sensing with Shack–Hartmann wavefront sensor based on auto gain control of electron multiplying CCD
Zhu Zhao-Yi1, 2, Li Da-Yu1, Hu Li-Fa1, Mu Quan-Quan1, Yang Cheng-Liang1, Cao Zhao-Liang1, Xuan Li1, †, 
The block diagram of the controller combined with the EMCCD.
