Correlation algorithm to recover the phase of a test surface using phase-shifting interferometry

Dynamical evaluation of interference fringe parameters by the Wiener adaptive filtering method

Application of the Wiener adaptive filtering method for estimation of interferometric signal parameters is presented and analyzed. It is shown that the fringe phase, as well as the envelope of low-coherence interference fringes, can be evaluated directly from the adaptive filter impulse response obtained under the criterion of the minimum error variance of a processed fringe signal and predefined reference signal. The method does not limit the number and value of the phase shifts and allows determination of the actual phase step. The accuracy of the method is evaluated and experimental results of dynamical fringe processing in low-coherence interferometry are presented.

Deterministic convergence in iterative phase shifting

Previous implementations of the iterative phase shifting method, in which the phase of a test object is computed from measurements using a phase shifting interferometer with unknown positions of the reference, do not provide an accurate way of knowing when convergence has been attained. We present a new approach to this method that allows us to deterministically identify convergence. The method is tested with a home-built Fizeau interferometer that measures optical surfaces polished to lambda/100 using the Hydra tool. The intrinsic quality of the measurements is better than 0.5 nm. Other possible applications for this technique include fringe projection or any problem where phase shifting is involved.

Blind phase shift estimation in phase-shifting interferometry

A blind phase shift estimation algorithm that allows simultaneous calculation of phases and phase shifts from three or more interferograms is presented. In phase-shifting interferometry, the phase shift errors introduce specific correlations between the calculated background intensity distribution and the fringe component. These correlations can be measured with a cross-power spectrum. By minimization of an objective function based on this cross-power spectrum, the actual phase shifts are estimated and used for phase recovery. The validity of this algorithm is verified by both the numerical simulation and the experiment results.

Water jet: a promising method for cutting optical glass

We present an alternative method for cutting optical glass. It works with a high-pressure fluid, carring abrasive powder. This technique offers some advantages over conventional methods that use diamond abrasive covered wires or disks. We make a critical comparison between those two techniques, characterizing cuts with interferometric, polarimetric, and Ronchi testing. The main feature of the water-jet technique is that it allows surface of any shape, already polished, to be cut safely.