Analysis of polishing errors from subaperture tools

The polishing process of aspheric or freeform surfaces is normally implemented using a subaperture tool. This tool is moved on a controlled path over the surface. A shape correction is done by controlling this movement. The use of different tools and controlling mechanisms may introduce errors. A way to visualize these errors is the analysis with the 'Power Spectral Density' (PSD) which gives information about the amplitude as well as the wavelength of the error. The behaviour of different polishing tools in simulation and real world polishing and the results of several optimisation algorithms are compared.