Fig. 1. Geometry of DFS.

Fig. 2. Relation between R and the piston error for cases with and without dispersion.

Fig. 3. Flow chart of the algorithm introduced in this Letter.

Fig. 4. Jn as a function of piston error, for (a) a uniform spectrum, (b) the random spectrum, (c) for the random spectrum shown in (b).

Fig. 5. Signal for a piston error of 42 μm. When the displacement of the actuator is −42 μm, the normalized merit function reaches its maximum.

Fig. 6. Two realizations of noisy DFP for different SNRs: (a) SNR is 1, (b) SNR is 5.

Fig. 7. Relative merit function versus piston error for an instant realization of DFP for an SNR of 1.

Fig. 8. Piston corresponding to the maximum of merit function versus different SNRs: (a) for uniform spectral profile, (b) for random spectral profile as in Fig. 4(b).