LB11-25-250 25.4 mm Dia. N-BK7 Double-Concave Lens; EFL=-250mm Uncoated

The LB11-25-250 is a high-quality spherical lens from CeNing Optics, featuring a concave-concave design. This lens is specifically designed for use in optical systems that require a negative focal length, making it ideal for applications such as beam expansion, image reduction, and other scenarios where a diverging lens is needed.

The lens has a diameter of 25.4 mm and a center thickness of 2 mm, providing a compact and robust design. The effective focal length (EFL) of this lens is -250 mm, which is the distance from the lens center to the point where the light rays converge or diverge. This negative EFL indicates that the lens will cause light rays to diverge, which is the defining characteristic of a double-concave lens.

The lens is made from N-BK7 glass, a popular material for optical elements due to its excellent optical properties and wide transmission range. The refractive index of N-BK7 at the specified wavelength of 546.1 nm is 1.5168, which contributes to the lens's high optical performance.

Notably, this lens is uncoated. While coatings can enhance the performance of optical elements by reducing reflection, increasing transmission, or providing other benefits, an uncoated lens can be advantageous in certain applications where cost, simplicity, or specific optical characteristics are important.