Hydrodynamic radial polishing tool: HyDRa

A novel hydrodynamic radial polishing tool (HyDRa) is presented. It performs corrective lapping and fine polishing of diverse materials by means of a low-cost abrasive flux and a hydrodynamic suspension system that avoids contact of the tool with the working surface. With this tool it is possible to polish aspheres and free-form optics on diverse materials and sizes. The functioning principle is based on the generation of a grazing, high-velocity, low-pressure, rotational, variable density, abrasive flux with radial geometry. It has the advantage of avoiding fallen edges during the polishing process as well as reducing tool wear out and deformation. The polishing process is repeatable and achieves high degrees of precision and accuracy on optical and semiconductor surfaces. This tool is particularly useful for polishing thin substrates such as membranes and semiconductors since it can be biased for a non-interactive action on the work piece. An additional advantage of this new tool is the possibility to perform in-process interferometric measurements. Polishing results on assorted materials using HyDRa are presented.