Figure 5.

Interferograms of the wavefronts produced by the membrane mirror before aberration correction (a) and after aberration correction (b). Additional wavefront tilt has been introduced into the reference beam to aid visualization of the wavefront aberration. These interferograms correspond to the mirror deformation used during the scans in Fig. 3 a and b, respectively. The wavefront in b compensates for aberrations induced by the optical system including the specimen. The actual induced aberration could be larger than that inferred by the interferogram because the built-in coverglass correction of the lens provides partial correction of spherical aberration.