It is assumed that accurate surface measurement is still possible with only a few fringes of low spatial frequency aberrations, i.e. astigmatism, coma and spherical aberration. To obtain this, we first generated Coma3 as described before and followed with superposition of Astm3 . . Next, Comatri is superposed onto the previous wavefront. In addition We have investigated the feasibility of correcting third and fifth-order wavefront aberrations by warping an active mirror. Comatri was achieved via the simple procedure of warping a constant-thickness fond de vase active mirror with a pressure control and with forces applied to two series of 12 radial support positions distributed symmetrically in two concentric ring around the mirror.
Possibilities also exist in the design of focal instruments by off-axis optics.
This work has been done in cooperation with the group of Prof. G. Lemaitre, at the Optical Group of Marseilles Observatory - France.