With spherical lens, the shape of the sphere corresponds to the cross-section of a sphere, which is a rotationally symmetric optical element with a constant radius of curvature at a distance from the geometric center. This means that the optical effective area can be described by specifying only one parameter, the radius R. This parameter is the same as the radius of the sphere. Since this parameter is constant over the entire surface, spheres have the advantage of being more economical in terms of cost in processing and manufacturing.

Hobbite offers K9 spherical lens, N-BK7 spherical lens, and many other kinds of spherical lens.

Specification
Material	K9,N-BK7
Diameter Tolerance	+0.0/-0.1mm
Irregularity (P-V)	λ/4@632.8nm
Centering Tolerance	It seems that the text you provided is incomplete. Please provide the full text you would like me to translate.3′
Bevel	0.2~0.5mmX45°
Design Wavelength	400~700nm
Center Thickness Tolerance	±0.2mm
Focal Length Tolerance	±2%
Surface Quality	60/40
Coating	Customized