Double concave lens(DCV) is similar with plano concave lens. The focus length is negative. It can make parallel light diverge outside. The two sides have same radius of curvature. Double convex lens generally used for expanding beam of light and projection etc. BK7 double concave lens has excellent transmittance from visible to near infrared wavelength (350-2000nm).
UV fused silica double concave lens(DCV) has better uniformity and lower thermal expansion coefficient compared with BK7 double convex lens. It has high transmittance from ultraviolet to near infrared wavelength(185-2100nm).