Abstract

The contemporary designs for large, space-born optical systems presented the industry with fabrication requirements which could not be met by conventional fabrication methods based on telescope-making techniques. The main features of these designs are on- and off-axis aspheric surfaces produced on highly lightweighted blanks (80% to 90%). To meet this requirement, Itek developed a computerized optical fabrication approach based on robotic technology. One of the challenges in this effort was to produce the surface on highly lightweighted blanks without a printthrough of the rib structure. It required a grinding and polishing method which would not utilize a net normal force for material removal. Recently, such a method has been developed. It replaces the conventionally used surfacing force provided by pinloading of the tool with a vacuum-induced suction force in the tool glass interface. In this approach, the net normal force acting on the glass surface has been reduced to zero, removing the cause for printthrough. This technique also provided solution for the rolled edges typically produced by pinload tools. The main cause for this surfacing defect is the pressure gradient produced in the tool glass interface whenever the tool overhangs the blanks edge. Replacement of the pin loading with vacuum-induced suction eliminated this gradient.

© 1990 Optical Society of America