Meniscus Lenses

Meniscus lenses have one concave surface and one convex surface.
A meniscus lens creates a smaller beam diameter thus reducing the spherical aberration and beam waste when precision cutting or marking. The lens also provides a smaller spot size that creates the same power output in a smaller area. In order to achieve the smallest spot size the concave side of the lens is mounted face down, pointing towards the material being cut.

Although meniscus lenses are more expensive than Plano-Convex lenses, they offer a higher accuracy of the cut therefore increasing cutting speed by up to 5%. Meniscus lenses are usually used by European customers and machine manufacturers (OEM's).

Plano-Convex Lenses

Plano-Convex lenses have one flat surface and one outward curving surface.
These lenses are more suitable for high turnover cutting applications and when cutting and welding certain materials (metals, wood, ceramics, plastics and composites) - when the cost is more important than the level of accuracy. 

When cutting steel and other thick materials, a Plano-Convex lens provides a greater width of the cut enabling the laser's Oxygen assist to enter and ease the cutting process. In addition, Plano-Convex lenses give a greater depth of field needed to maintain a taperless edge when cutting thicker materials. This kind of lens is more popular in American and Japanese machinery.