Co-focus experiment of segmented mirror

In this paper, an active optics and co-focus experimental system of segmented mirror is built. Firstly, a support structure of segmented mirror is designed and it is verified by simulation to meet the requirement for the experimental system of segmented mirror. In this system, the large de-focus and tilt/tip errors of the segmented mirror are adjusted by observing the density and contrast of interference fringes based on isoclinic interference theory until the defocus and tilt/tip errors are in the detective range of the Shack-Hartmann. Then, the Shack-Hartmann is used to measure them and they are adjusted by actuators. The actuators are controlled by active optics to realize the closed-loop adjustment and maintenance for fine co-focus of segmented mirror. And the interference fringes are utilized to verify the detective precision of Shack-Hartmann. After the co-focus fine-tuning of the segmented mirror, the tilt/tip residual surface error is better than 0.01λ RMS; the defocus residual surface error is better than 0.01λ RMS.