Bi-Concave (Double-Concave) lenses have equal radius of curvature on both sides of the lens and function similarly to plano-concave lenses by causing collimated incident light to diverge. Bi-Concave lenses are generally used to expand light or increase focal length in existing systems, such as beam expanders and projection systems, and are the best choice when the object and image are at absolute conjugate ratios closer to 1:1 with a converging input beam. N-BK7 lenses are a great choice for most general purpose visible and NIR applications, featuring high homogeneity and low bubble and inclusion content. UV Fused Silica lenses are ideal for UV or higher energy applications, combining a very low thermal expansion coefficient and excellent transmittance down to 195 nm.
| Material | optical glass,N-BK7 , Fused Silica, sapphire,Si,Ge,CaF2,LiF,BaF2 |
| Dimensions | 3-400mm |
| Dimension Tolerance | ±0.01mm |
| Thickness Tolerance | ±0.01mm |
| Center thickness | >1mm |
| Focal Length tol. | ±1% |
| Centration | 3 arc minutes |
| Surface Quality | 80/50 60/40 40-20 20-10 |
| Clear Aperture | >90% |
| Wavelength Range | Substrate Material |
| 180nm-8.0μm | Calcium Fluoride (CaF2) |
| 185 nm-2.1 um | UV Fused Silica |
| 200 nm- 5.0 um | Sapphire |
| 200 nm- 6.0 um | Magnesium Fluoride (MgF2) |
| 220 nm to >50 um | CVD Diamond Windows |
| 230 nm- 1.1 um | UV Fused Silica. Textured Antireflective surface |
| 250 nm- 1.6 um | UV Fused Silica, for 45° AOI |
| 250 nm- 26 um | Potassium Bromide (KBr) |
| 350 nm- 2.0 um | N-BK7 |
| 600 nm- 16 um | Zinc Selenide (ZnSe) |
| 1.2- 8.0 um | Silicon (Si) |
| 1.9- 16 um | Germanium (Ge) |
| 2- 5 μm | Barium Fluoride (BaF2) |
