49-931 18 mm Dia. N-BAF10/N-SF57 Achromatic Doublet; EFL=22.5mm MgF2 400-700nm

The 49-931 is an 18 mm diameter achromatic doublet lens, designed and manufactured by Edmund Optics. This lens is a multiplet, meaning it is composed of multiple optical elements to achieve superior performance. The lens is specifically designed for use in the 400-700nm spectral range, making it suitable for a wide range of applications in the visible light spectrum.

The lens features a focal length of 22.5mm, indicated by the EFL (Effective Focal Length) parameter. This focal length, combined with the lens's diameter, allows for a wide field of view while maintaining a compact form factor. The lens's geometry includes a thickness of 8.03mm at the edge and 8.7mm at the center, with an additional 3mm of material at the center-front for coating application.

The lens is made from two types of glass, N-BAF10 and N-SF57, both from Schott. These glasses are chosen for their specific refractive indices and dispersion properties, which contribute to the lens's achromatic design. This design ensures that the lens effectively corrects chromatic aberration, a common issue in optical systems where different wavelengths of light are focused at different points.

The lens is coated with Edmund Optics' standard MgF2 coating on both the front and back surfaces. This coating is designed to reduce reflection and increase transmission, improving the lens's overall efficiency and performance. The coating is applied in a standard curve, ensuring consistent performance across the lens's surface.