TheDoubleConcaveLensesaremadefromBK7material,whicharemanufacturedwithbothsurfacesconcave.Theselenseshavenegativefocallengths.Theselensesdivergecollimatedincidentlightandformvirtualimages,whichareseenthroughthelens.Theyareoftenusedtoexpandlightorincreasefocallengthsinexistingsystems.Theyareusedinlaserbeamexpanders,opticalcharacterreaders,viewers,andprojectionsystems.WewillprovideprecisiongradeDoubleConcaveLenseswithtightermanufacturingtolerances.Specifications:Material:BK7DesignWavelength:546.1nm,n=1.518721DiameterTolerance:+0.0/-0.1mmParaxialFocalLength: 2%Centration:3arcminutesSurfaceFigure:l/4@632.8nmSurfaceQuality:60/40ClearAperture: 80%Bevel: 0.25mmX45 Coating:Uncoated