Differences between Aspheric and Spherical Lenses
A spherical lens refers to a constant curvature from the center to the edge of the lens, while an aspherical lens continuously changes the curvature from the center to the edge.
The “curvature of the sphere” of a spherical lens is uncertain, meaning that the surfaces in front of and behind the lens are respectively part of the spherical surface. Each surface can be convex (protruding outward from the lens), concave (concave into the lens), or “flat” (flat). The line connecting the spherical center points of the front and rear surfaces of the lens is called the optical axis of the lens. In almost all cases, the optical axis of the lens passes through the physical center of the lens. The curvature radius of an aspherical lens changes with the central axis, which has a better curvature radius and can maintain good aberration correction.