Abstract

Computer controlled stressed-lap polishing, developed at the Steward Observatory Mirror Laboratory, promises to be an effective method for figuring large, fast aspheric mirrors. Stressed- lap polishing uses a large stiff circular polishing tool that is actively deformed under computer control so that it continually fits the aspheric mirror surface. As the lap is translated across the rotating mirror, the lap’s horizontal speed and rotation rate, the total force on the lap, and applied moments to the lap are all dynamically controlled. To fully take advantage of these many degrees of freedom, computer simulation and optimization software has been developed. The simulation is based on Preston’s equation (local removal rate proportional to pressure and relative velocity) but allows the inclusion of nonlinear effects based on comparison to measured results. The optimization of polishing parameters is accomplished by a damped least-squares optimization algorithm which varies the polishing parameters to obtain a desired simulated removal profile.

© 1991 Optical Society of America