The flat lapping of plano optical windows using a double-sided planetary machine is the most feasible process for flat lapping when both sides of the windows need lapping. This process is performed for pre-polishing using very fine micro abrasives of Calcite Allumina powder. The smoothing of the surface is very important to the final polishing. Great care and attention must be paid to the condition of the lapping plates and abrasive. The lapping plates are prepared using a set of precision conditioning rings which lap the metal lapping plates prior to the lapping of the components.

When a non-polished surface is required, surfaces can be lapped to different gradients of roughness. This can be either single of both sides of the window. The controlled roughness process is used for the manufacture of optical glass diffusers controlling the scattering of light. For less demanding applications, the surfaces can be sandblasted.

Double-sided planetary flat lapping can hold thickness tolerances to 0.010mm and achieve parallelism to less than 10 seconds of arc. Components and flats can be processed from 3mm dia to 300mm dia or 5mm² to 200mm².