Imaging experiment of an adaptive optics with a normal-incident EUV telescope

We report experimental results of our normal-incident EUV telescope tuned to a 13.5 nm band, with an adaptive optics. The optics consists of a spherical primary mirror and a secondary deformable mirror. A laser plasma source irradiates optical and EUV lights to the system. The system also equips a reference laser, optical light from which are nearly spherical and reflected by mirrors through the light path along the objective light. We controlled the deformable mirror to correct the wave form by referring that of the reference laser. At first, we attempted a normal AO control, where we controlled deformable mirror so that the wave form of the reference laser becomes spherical. Although we verified an improvement of angular resolution with this method, the resolution is not good enough comparing with the diffraction limit. The degradation is due to the difference between the paths of objective light and the reference laser. Then we modify the target wave form to control the deformable mirror, as the EUV image becomes best. We confirmed the validity of this control and performed a 2.1 arcsec resolution in both optical and EUV lights.