Meniscus lens is concave-convex lens. The lens has a convex mirror and a concave mirror. The meniscus lens can be a positive lens or a negative lens. The center of the negative meniscus lens is thinner than the periphery, and the center of the positive meniscus lens is thicker than the periphery. Meniscus lens can correct phase difference, which is usually used as correction lens, and can also be used as concentrator of illumination system, and choosing appropriate thickness can also eliminate chromatic aberration.