Meniscus Lens can increase the NA of the system while only adding slightly to the total spherical aberrations. The Negative Meniscus Lens is used to increase the focal length of another lens while maintaining the angular resolution of the optical assembly. This lens shape is best used when one conjugate is relatively far from the lens.

Specifiction of our meniscus lens as follow:
*Material BK7 or other optical materials 
*Dimension Tolerance +0.0~-0.1mm 
*Center Thickness +/-0.1mm 
*Focal Length Tolerance+/-1%
*Surface Quality:40/20
*Surface Figure:lambda/2 at 633nm on plano side 
*Clear Aperture >90%
*Chamfer 0.25mm at 45 degree typical 
*Coating Optional