Digital surfacing uses CNC (computer numerically controlled) technology in the generator to transfer highly accurate designs to the lens. Digital surfacing can be used to create simple single vision lenses or very complex progressive lens designs.
The milling, or lathing, process used in traditional lens generators leaves imperfections and irregularities on the lens surface that must be polished out using a hard “lap” tool. This process produces a lens with a high quality, optically correct surface but it is limited to spherical or toric surfaces.
Because the CNC generator is so much more accurate, digitally surfaced lenses require only a light polishing with a softer tool to finish the surfacing. Using a softer tool for polishing allows us to also produce aspheric and progressive lens designs with our digital surfacing equipment.
Conventional lens surfacing typically takes a molded lens that has the lens design manufactured into the front side and the generator mills the power into the backside of the lens.
Most digital lens designs are used to create “backside” lenses, which refers to the fact that both the design and the power are added to the back side of the lens blank during digital surfacing.
Essilor’s patented DualOptix lenses start with unfinished lenses that have a portion of the progressive lens design already manufactured into the front of the lens and then the rest of the design and power are digitally surfaced into the back of the lens. Combining a front side and back side lens design allows for nearly unlimited customization and delivers greater visual performance than single sided progressives.