Standard diverging and expanding lens for most routine applications; 350 nm – 2 μm. These N-BK7 equi-concave lenses offer low f-number and are well-suited to a wide range of light expansion tasks in the visible and near-infrared. They are available in a selection of standard focal lengths and diameters, with optional VIS & NIR broadband AR coatings.

Standard N-BK7 bi-concave lenses use their negative focal length to diverge or expand light in laser beam expanders, optical character readers, viewers, and projection systems.  N-BK7 is the preferred optical glass for quality optical components in the visible and near infrared, offering excellent transmission, as well as good optical and mechanical properties.   These bi-convex lensespossess two concave surfaces of equal radii.  Like their convex counterparts, they are best corrected for diverging a converging beam, but can also be used at infinite or near-infinite conjugate ratio when compact optical systems are required, as in the construction of beam expanders. They are well-suited to a wide range of applications, but are not recommended for high energy lasers or when high wavefront quality is required.  In those applications, we recommend using our BICC-C laser quality lenses.  Contact CVI Laser Optics for custom dimensions, focal lengths and OEM capabilities.
• Negative focal lengths from 5 to 50 mm
• Diameters from 5 to 42 mm
• Available uncoated or with visible or near-IR broadband AR coatings