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Thorlabs - Model N-BK7 -Plano-Convex Lenses (Uncoated)
These uncoated Plano-Convex Lenses are fabricated from RoHS-compliant N-BK7 glass. N-BK7 is typically chosen whenever the additional benefits of UV fused silica (i.e., good transmission further into the UV and a lower coefficient of thermal expansion) are not necessary. They have a positive focal length and near-best-form shape for infinite and finite conjugate applications.
Plano-convex lenses can focus a collimated beam or collimate light from a point source. To minimize the introduction of spherical aberration, a collimated light source should be incident on the curved surface of the lens when being focused and a point light source should be incident on the planar surface when being collimated.
The focal length of each lens can be calculated using a simplified thick lens equation:
f = R/(n-1),
where n is the index of refraction and R is the radius of curvature of the lens surface. These lenses are fabricated from N-BK7, which has an Abbe Number of 64.17; this value is an indicator of the dispersion.
These N-BK7 Plano-Convex lenses are also available 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 links to each 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 coating information.
Thorlabs offers fixed lens mounts that can be used for mounting the lenses sold here. For mounting high-curvature lenses in select sizes, extra-thick retaining rings with SM05 (0.535"-40), SM1 (1.035"-40), or SM2 (2.035"-40) threading are available that provide extra clearance for spanner wrenches (see the Lens Mounting Guide tab for more information).
Features
- Material: N-BK7
- Wavelength Range: 350 nm - 2.0 μm (Uncoated)
- Available Uncoated or With One of Three Broadband Antireflection Coating
- Offers Excellent Transmittance Throughout the Visible and Near Infrared
- Focal Lengths Available from 10 to 1000 mm