This is the 89-607 model from Edmund Optics, a 25mm diameter Germanium Infrared Aspheric Lens with an effective focal length (EFL) of 12.5mm and a numerical aperture (NA) of 1. This lens is specifically designed for use in the infrared spectrum, with a coating that is optimized for wavelengths up to 4000nm.
The lens features a base shape of a circle and is made from Germanium burnett material. It has an inner radius of 0 and an outer radius of 0, with a thickness at the edge of 2.5mm. The EFL of 12.5mm is complemented by a back focal length (BFL) of 11.61mm. The center thickness of the lens is 4.24mm, and it has a diameter of 25mm.
The lens's aspheric shape is defined by its radii (r1: 41.397, r2: 435.187), and it has a NA of 1. The front and back of the lens are coated with "edm arcedgermanium31", providing excellent durability and performance in the infrared spectrum.
The lens is currently in stock and can be purchased directly from the Edmund Optics website using the provided weblink.