87-995 50mm Dia. Germanium Infrared Aspheric Lens; EFL=25mm; NA=1 BBAR 3-5µm

This is the 87-995 model from Edmund Optics, a 50mm diameter Germanium Aspheric Lens, specifically designed for Infrared applications with a wavelength of 4000nm. The lens boasts an effective focal length (EFL) of 25mm and a numerical aperture (NA) of 1, indicating its high light-gathering capability and ability to resolve fine details.

The lens is made of Germanium, a material known for its excellent transmission properties in the infrared spectrum. It features a Broadband Anti-Reflective (BBAR) coating on both the front and back surfaces, which significantly reduces surface reflections and increases transmission, thereby enhancing the overall performance of the lens.

The lens geometry is intricately designed with an inner radius of 0 and an outer radius of 0, suggesting a symmetrical structure. The thickness at the edge is 2.5mm, while the center thickness is 7.75mm. The lens's front surface is defined by a conic constant (k1) of 0, indicating a spherical shape, and the back surface (k2) is also 0, suggesting a similar spherical shape.

The lens's shape is aspheric, which means it has a non-spherical surface. This design helps to correct spherical aberration, a common optical problem where light rays fail to meet at a single point, leading to a blurry image. The aspheric shape ensures that the light rays converge at the correct point, providing a sharper image.