Development of figure correction system for inner surface of ellipsoidal mirrors

In this study, a figure correction method employing ion beam sputtering deposition was developed. The sputtering target is placed inside the ellipsoidal mirror. Then, a cylindrical tube with a small aperture is inserted inside the mirror to realize selective deposition. The figure accuracy of an ellipsoidal mirror is improved even when its diameter is less than 10 mm. This figure correction system can also be applied to various axisymmetric devices with a small diameter.