Thorlabs LC1439-B Plano Concave Spherical Lens

What Is the Thorlabs LC1439-B?

• It’s a plano-concave spherical lens.

• Made of N-BK7 optical glass.

• Diameter: ½ inch (12.7 mm).

• Focal length: –50.0 mm (i.e., it diverges light).

• Has an AR (anti-reflection) coating for 650–1050 nm (“B” coating).

Optical and Mechanical Specifications

• Center thickness: 3.5 mm.

• Edge thickness: ~4.3 mm.

• Radius of curvature (concave side): –25.7 mm.

• Back focal length: –52.3 mm.

• Surface quality: 40-20 scratch-dig.

• Focal length tolerance: ±1%.

• Centration: < 3 arcmin.

• Clear aperture: > 90% of diameter.

Material & Coating Notes

• Substrate: N-BK7. This is standard BK7 glass, a very common optical glass.

• Coating (“B”): Broadband AR for 650–1050 nm. Useful if you are working in red / near-IR wavelengths, since it minimizes reflections in that band.

Uses / Applications

A lens like this is typically used to diverge collimated beams (because of the negative focal length). Some common use cases:

• Beam expansion: can be part of a beam expander to increase divergence on one axis.

• Aberration compensation: negative lenses like this can be used to correct for spherical aberrations introduced by other optics.

• Optical design: for optical systems where you need to do ray shaping or add divergence.