47-016 12.5 mm Dia. N-BK7/N-SF5 Negative Achromatic Doublet; EFL=-75mm MgF2 400-700nm

The 47-016 is a high-quality negative achromatic doublet lens, sourced from the renowned optical vendor, Edmund Optics. This lens, with a diameter of 12.5 mm, is designed for use in the visible spectrum, specifically between 400-700nm.

The lens features a negative doublet design, which is a compound lens made up of two separate elements with different refractive indices. This design helps to correct chromatic aberration, a common issue in optical systems where different wavelengths of light are focused at different points. The negative achromatic doublet design of the 47-016 ensures that the lens focuses light of different wavelengths onto a single point, improving the overall image quality.

The lens has an effective focal length (EFL) of -75mm, which is the distance from the lens's principal point to the point where the lens focuses parallel rays of light. The negative EFL indicates that the lens diverges light, which is typical of negative lenses.

The 47-016 is made from two types of glass: N-BK7 and N-SF5, both from Schott. N-BK7, also known as borosilicate crown, is a common optical glass with a low refractive index and low dispersion. N-SF5, on the other hand, is a dense flint glass with a high refractive index and high dispersion. The combination of these two glasses in the doublet design helps to correct chromatic aberration.

The lens is coated with MgF2, a standard coating that provides high transmission in the visible spectrum. This coating helps to reduce reflection and increase the amount of light transmitted through the lens, improving the overall image quality.