The determinism of the MRF optical polishing process relies on a well-characterized and stable removal rate during polishing runs. The workpiece immersion depth into the MR fluid is a main contributor to the removal rate. During polishing, the CNC machine platform attempts to maintain a consistent immersion depth throughout the toolpath to keep the removal rate constant. Polishing aspheric parts with either significant wedge or unaccounted for aspheric shape can result in unpredicted removal rate errors due to a change in plunge depth. By accounting for the figure error expected from the change in plunge depth in the hitmap, the removal error resulting from high amounts of wedge and aspheric departure can be mitigated. This process allows MRF to figure correct highly wedged parts and to reduce MRF iterations on challenging aspheric parts.
While the wave structure function has been analytically calculated for a variety of beam types, recent work has begun the exploration of higher-order beams and partially coherent beams. For these waves, no analytic wave structure function has been developed. By extending the well known split step phase screen simulations, we have developed a method of numerically simulating the wave structure function. We present the methods and results of this simulation technique, and describe its applicability to general beams.
We have previously shown that amplitude weighting can improve the accuracy of measurements of the frequency offset of a signal contaminated by multiplicative Gaussian noise. We have investigated the more general non-Gaussian case through study of the statistics of a simple phase-screen scattering model and derived formulae for the low-order moments of the intensity-weighted phase-derivative. In this paper we extend numerical simulation of the problem to the case of a phase screen with Kolmogorov spectrum. We also report the results of some preliminary experimental measurements.