Double Convex lens with AR coating both surfaces

A double convex lens also called bi convex lens, it's also a part of spherical lens which is converging lens with a positive focal length outward on both sides, with center being thicker and edge being thinner. it's converges the parallel light towards the optical axis, can form either a real image or a virtual image, commonly used as the primary imaging lens or focusing lens, the symmetrical design helps reduce certain aberration, but it is more difficult to align compared to a plano convex lens, and the cost is slightly higher.commonly used in camera,telescope, microscope as objective lens, also used in projector, searchlight light collection systems.   In beam expander, double convex lens and double concave lens usually combine together, first , the light beam is diverged by a double concave lens, then it's focused through a double convex lens, final ouput is beam with an enlarged diameter and a reduced divergence angle,by combining the opposite optical focal lengths of the two,the…