Rapid optical figuring of aspherical surfaces with plasma-assisted chemical etching

Programmed motion of a tool which removes material by plasma assisted chemical etching (PACE) gives controlled, deterministic figuring. The process has been automated to correct arbitrary figure errors on aspheric surfaces directly from the measured surface data. A system is now operating for figuring aspheric surfaces up to 0.5 m diameter. PACE can greatly reduce the time and cost of figuring large optics by its rapid convergence to the final figure requiring only two to three measurement/figuring cycles to reach 1/50 wave surfaces. PACE intrinsically smooths high frequency roughness with material removal leaving a surface free of subsurface damage