Znse lens is used in the infrared band, it will focus the light into a point. It is characterized by a positive focal length, one side is flat and the other is convex. Commonly used for aiming and focusing monochromatic light sources. To use, face the convex side toward the incident light. ZnSe lenses are commonly used as collimators in laser applications, such as biomedical and military applications. These lenses are also particularly suitable for high power CO or CO2 laser applications. Furthermore, they are transparent enough in the visible range to be useful for visible beam alignment, although back reflections are more pronounced.