"; _cf_contextpath=""; _cf_ajaxscriptsrc="/cfthorscripts/ajax"; _cf_jsonprefix='//'; _cf_websocket_port=8578; _cf_flash_policy_port=1244; _cf_clientid='2BFE5EFCCD911EDDDD04D2E9A0FE537A';/* ]]> */
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
N-BK7 and N-SF11 Bi-Concave Lenses, Uncoated![]()
LD1464 (Ø1") LD1357 (Ø1/2") LD2568 (Ø9 mm) LD2746 (Ø6 mm) These Lenses are Also Available in the LSB04 Kit ![]() Please Wait
Features
Thorlabs offers Bi-Concave lenses fabricated from either an N-BK7 or an N-SF11 substrate. These lenses are available uncoated or with one of our three popular broadband antireflection coatings deposited on both sides to reduce the amount of light reflected from each surface of the lens. the lenses on this page are uncoated and have broad wavelength ranges. Please see the Graphs tab for detailed coating curve information. Bi-concave lenses have a negative focal length and are best used to diverge a converging beam. Similar to a plano-concave lens, a bi-concave lens can diverge a collimated beam to a virtual focus like in a Galilean-type beam expander. Since the Abbe Number of N-SF11 (25.76) is lower than that for N-BK7 (64.17), lenses fabricated from N-SF11 will exhibit higher dispersion than those fabricated from N-BK7. Lens kits with bi-concave lenses made from N-BK7 are available.
![]() Click to Enlarge Click Here for Raw Data Above is the transmission curve for N-BK7, a RoHS-compliant form of BK7. Total Transmission is shown for a 10 mm thick, uncoated sample and includes surface reflections. ![]() Click to Enlarge Click Here for Raw Data Above is the transmission curve for N-SF11. Total Transmission is shown for a 10 mm thick, uncoated sample and includes surface reflections.
The lenses sold on this page are also available with broadband antireflective coatings, the reflectance traces of which are shown in the graph below. These high-performance multilayer AR coatings have an average reflectance of less than 0.5% (per surface) across the specified wavelength ranges and provide good performance for angles of incidence (AOI) between 0° and 30° (0.5 NA). The plot shown below indicates the performance of the standard coatings in this family as a function of wavelength. Broadband coatings have a typical absorption of 0.25%, which is not shown in the reflectance plots.
Mounting High-Curvature OpticsThorlabs' retaining rings are used to secure unmounted optics within lens tubes or optic mounts. These rings are secured in position using a compatible spanner wrench. For flat or low-curvature optics, standard retaining rings manufactured from anodized aluminum are available from Ø5 mm to Ø4". For high-curvature optics, extra-thick retaining rings are available in Ø1/2", Ø1", and Ø2" sizes. Extra-thick retaining rings offer several features that aid in mounting high-curvature optics such as aspheric lenses, short-focal-length plano-convex lenses, and condenser lenses. As shown in the animation to the right, the guide flange of the spanner wrench will collide with the surface of high-curvature lenses when using a standard retaining ring, potentially scratching the optic. This contact also creates a gap between the spanner wrench and retaining ring, preventing the ring from tightening correctly. Extra-thick retaining rings provide the necessary clearance for the spanner wrench to secure the lens without coming into contact with the optic surface.
![]() | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|