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Products Home / Optical Elements / Optical Lenses / Spherical Singlet Lenses / Bi-Concave Spherical Lenses / N-BK7 and N-SF11 Bi-Concave Spherical Lenses
N-BK7 and N-SF11 Bi-Concave Spherical LensesThorlabs' N-BK7 and N-SF11 Bi-Concave lenses are popular for many applications. They are available mounted or unmounted, either uncoated or with an AR coating. Bi-Concave lenses have a negative focal length and are best used to diverge a converging beam. Bi-concave lens can diverge a collimated beam to a virtual focus and are commonly used in Galilean-type beam expanders.