AL2520 25 mm Dia. S-LAH64 High-Precision; CNC Polished Aspheric Lenses; EFL=20 mm; NA=0.54 Uncoated

The AL2520 is a high-precision aspheric lens offered by Thorlabs, designed with a 25 mm diameter and a focal length of 20 mm. This lens is crafted from S-LAH64 Ohara, a high-quality optical glass known for its excellent transmittance and low autofluorescence. The lens's base shape is circular, ensuring uniform light distribution.

The lens's geometry is defined by its inner and outer radii, both of which are 0 mm, indicating a flat surface. The lens has a thickness of 2.4 mm at the edge and 7.6 mm at the center. The aspheric design is characterized by its conic constant (k1) of -1.35 and aspheric coefficients (a2 to a16), which control the curvature of the lens surface, minimizing spherical aberration and improving imaging quality.

The lens's numerical aperture (NA) is 0.54, indicating a high light-gathering capability. However, it is uncoated, meaning it may not offer optimal protection against environmental factors or scratch resistance compared to coated alternatives. Despite this, the lens's uncoated state can provide superior optical performance in specific applications where anti-reflection coatings may not be necessary.