One of the challenges of the optical manufacturer is measuring a lens curvature and its radius. Producing a lens has a long process from the raw material stage until the final product is created, which is polished and curved, either spherical or aspherical.
Measuring a polished and transparent flat lens is possible, albeit challenging. Measuring a polished and transparent lens which is curved is even more challenging since the signal back-reflection has to go inside the detector in order to get a measurement. The angular coverage of a laser sensor over glass is very limited and stands over a few degrees only.
Along the lens manufacturing process there is a stage where the lens is still diffusive after its grinding, and before polished. Such condition is perfectly suitable for measuring by a non-contact laser sensor. Other technologies which are also used today are manual spherometer and a touch probe. Both are relatively slow process and a non-contact sensor can make the measurement much faster.