Pertaining to a multi-focal lens that incorporates three separate corrective powers within a single piece of glass or plastic. These lenses are designed to provide clear focus at distance, intermediate, and near viewing ranges. In optical manufacturing, creating a trifocal requires precise grinding and polishing to minimize the visual jump and distortion at the boundaries between the three focal zones.
Heard on the job
The technician had to re-grind the trifocal blank because the intermediate zone was slightly off-axis.
Also heard as
- trifocals