In an aspheric lens design, how does the surface curvature behave?

The correct answer reflects the behavior of surface curvature in an aspheric lens design, which is characterized by a varying curvature that indeed flattens from the center towards the edges. This design allows the lens to reduce spherical aberration and improve image quality. In traditional spherical lenses, the curvature is uniform, leading to distortion in the image, especially towards the periphery.

Aspheric lenses are crafted to have a more complex shape, where the curvature changes in a controlled manner, typically becoming flatter as one moves away from the center. This design effectively accommodates different optical requirements, enabling the lens to better focus light and enhance clarity, particularly in high-performance optical applications.

The other options misrepresent how aspheric lenses function. For example, constant curvature would lead to significant optical distortions, and sharpening towards the edges would be contrary to the principle of aspheric design, which aims to correct for such distortions. The suggestion of unpredictable variation does not align with the intended precision and design of aspheric lenses.