Double-Concave lens
A double-concave lens is compose of two concave surface, has a negative focal length and are best used to diverge a converging beam. Similar to a plano-concave lens, a bi-concave lens can diverge a collimated beam to a virtual focus like a beam expander.​

Material:                        BK7 Optical glasses,CaF2,BaF2, MgF2,Ge,Si,Fused Silica

Diameter Tolerance:     +0.0/-0.02mm

Thickness Tolerance:    ± 0.01mm

Surface Accuracy:        λ/4 @632.8nm

Surface Quality:           20-10

Centration:                  1′

Clear Aperture:            > 90%

Bevel:                          0.2mm×45°

Coating:                      user-defined