49-311 6.25 mm Dia. N-BK7/N-SF5 Achromatic Doublet; EFL=50mm VIS-NIR 400-1000nm

The 49-311 is a high-quality achromatic doublet lens, boasting a 6.25 mm diameter and a focal length of 50mm, specifically designed for the visual and near-infrared spectrum (400-1000nm). This lens is sourced from the renowned optical vendor, Edmund Optics, and is available for purchase on their official website.

The lens is constructed from two types of glass, N-BK7 and N-SF5, both from Schott, ensuring superior optical performance. The N-BK7, a borosilicate crown glass, is known for its low dispersion and excellent homogeneity, while the N-SF5, a fluorite crown glass, offers a high Abbe number and low refractive index. This combination effectively minimizes chromatic aberration, a common issue in optical systems.

The lens features a robust geometry, with a thickness of 2.77mm at the edge and 2mm at the center. The inner and outer radii are 0, indicating a circular shape. The first radius of curvature (r1) is 30.77mm, while the second (r2) is -22.05mm, and the third (r3) is -64.6mm. This complex geometry contributes to the lens's high performance and versatility.

The lens is coated with edm visnir0sp2002000 on both the front and back surfaces. This anti-reflection coating is specifically designed for the visual and near-infrared spectrum, reducing surface reflections and improving transmission.