A biconcave lens will radiate light with a negative focal length, which is composed of two concave surfaces with equal curvature. It is often used for beam expansion, projection and focal length expansion of the lens. Hengpu optics provides double concave lenses without coating and with antireflection coating. Antireflective film options include UV, VIS, NIR, and SWIR. Germanium, silicon or zinc selenide substrates are suitable for infrared applications, while fused quartz is suitable for ultraviolet applications.
Material: K9, BK7, FS, UVFS, CaF₂, ZnSe
Diameter:3mm-200mm±0.05mm
Center Thickness Tolerance:±0.05mm
Lens Alignment Error:≤3min
Surface Accuracy:λ/ 10 @
Surface Quality:40/20. 60/40. 80/60
Effective Caliber: 90%
Example with BK7 material：These N-BK7 biconvex lenses are available uncoated or with one of five antireflection coatings (-A, -AB, -B, -C, or -D), which reduces the amount of light reflected from each surface of the lens (see the Selection Guide table below for coating option). Since approximately 4% of the incident light is reflected at each surface of an uncoated substrate, the application of an AR coating improves transmission, which is important in low-light applications, and prevents the undesirable effects (e.g., ghost images) associated with multiple reflections. Having optics that are AR coated on both surfaces is particularly desirable for applications utilizing multiple optical elements. Please see the Graphs tab for additional coating information.
| N-BK7 bi-Concave Lens Selection Guide | 
|
| Coating name | wavelength band |
| Uncoated | Uncoated |
| A Coating | 350nm-700nm |
| AB Coating | 400nm-1100nm |
| B Coating | 650nm-1050nm |
| C Coating | 1050-1700nm |
| D Coating | 1650nm-3000nm |
Other series products：
Concave lens Achromatic Lens Ball Lens Silicon Window Zinc Selenide Window Wedge Optical Window
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