( ( ( Place ( the ( double ( concave lens ) ) ) ) ( after ( the ( cylindrical lens ) ) ) ) . )
(ROOT (S (VP (VB Place) (NP (DT the) (JJ double) (NN concave) (NN lens)) (PP (IN after) (NP (DT the) (JJ cylindrical) (NN lens)))) (. .)))
Place the double concave lens after the cylindrical lens.
(ROOT (S (NP (DT A) (JJ concave) (NN lens)) (VP (VBZ is) (NP (NP (JJR thicker)) (PP (IN at) (NP (DT the) (NNS edges)))) (SBAR (IN than) (S (NP (PRP it)) (VP (VBZ is) (PP (IN in) (NP (DT the) (NN middle))))))) (. .)))
A concave lens is thicker at the edges than it is in the middle.