UltraForm Finishing (UFF), OptiPro Systems' five axis sub-aperture polishing machine has evolved from an initial
prototype into a robust aspheric manufacturing system that can rapidly produce finished aspheres directly from a ground
surface. UFF utilizes a belt of polishing material 50" long supported by a polyurethane wheel to polish a wide variety of
materials ranging from traditional glasses to IR materials. This belt polishing system provides a tuned stiffness that is
capable of conforming to the polishing surface without replicating the surface roughness. When combined with state of
the art figure correction algorithms, the UFF is capable of robust and deterministic figure correction for aspheric
Recently, OptiPro Systems has expanded the capability of the UFF to include deep concave ogive and free-form
surfaces. Although these types of surfaces can be beneficial from an optical or aerodynamic standpoint they pose
additional challenges both from their steep geometry as well as from a polishing tool path perspective. A brief
description of these challenges as well as possible solutions to these problems will be presented. In addition, the current
figure correction capability of the system utilizing feedback from OptiPro's five axis non-contact free-form metrology
system will be presented.
OptiPro Systems has developed a robust 5-axes computer controlled platform, for implementation of the sub-aperture
UltraForm Finishing (UFF) process specifically focused on finishing AlON, spinel and transparent polycrystalline
alumina (PCA) steep concave, convex and ogive shaped infrared domes and aspheres. Traditional manufacturing of
optical components typically involves a three-stage process: grinding, lapping and polishing. The lapping and polishing
stages are focused at reducing the surface roughness while preserving the integrity of the form acquired during grinding.
Polishing of non spherical and irregular shapes is nearly impossible using traditional full aperture techniques. However,
finishing these non-spherical and irregular shapes is possible using UltraForm Finishing.
A brief description of the evolution of the UltraForm hardware and processes will be presented, with the current
hardware developments. A review of the results with regard to form/figure and roughness improvements on glass, AlON
and transparent PCA will be presented using a variety of grinding and finishing abrasives. Differences in the abrasive
materials, some bound, and others loose in a slurry have a large impact on the process cycle time and resultant surface
OptiPro Systems is developing a non-contact measurement system using state of the art motion control while minimizing the axes of motion during the measurement. The goal is to precisely scan concave and convex surfaces of aspheric, deep parabolic, and ogive shapes without the limitations associated with other measurement methods. The metrology systems will use different computer controlled slicing techniques to create a topographical surface map of the surface form with a high accuracy non-contact probe.
To achieve this precise scan the measurement system will incorporate sub-micrometer precision air bearings for the linear and rotary axes motion to minimize the effect of non-repeatable mechanical errors. Calibration of the measurement system will use high precision reference spheres. Finite element modeling and estimate has been used to predict and possibly compensate for mechanical flexures.
OptiPro has built a "breadboard" measurement system using a Professional Instruments air bearing and a STIL white light measurement pen. The results from the measurement of a near full hemispheric dome measurement will be presented as well as a comparison to the same dome measured using a stitching interferometer. The final system will incorporates complete computer controlled axes requiring as little operator training and set up as possible. The prototype system will utilize a non-contact pen for measurement. Current developments include the utilization of the STIL white light pen and the OptiGauge optical probe which utilizes invisible 1310 nm infrared light. The current system design and performance will be presented.