These patterned flash fronts are typically used to shape and spread the light efficiently without needing a thick, heavy conventional lens. The segmented pattern works like a Fresnel-type optical element: it breaks a curved lens into many smaller sections, reducing bulk, weight, and some optical losses while still controlling the flash beam.

For a flash, the goal is usually not to form a sharp image, but to project light in a useful pattern. Small discontinuities in the surface are acceptable as long as they distribute the light evenly across the beam.

A diffuser has a related purpose: it softens or spreads the light, helping avoid a narrow, harsh beam. In practice, these thin patterned plates are a compact way to manage the light cone.

Without this kind of patterned lens/diffuser, a flash would either need a thicker conventional lens or would produce a less controlled beam pattern. That could mean a heavier front element, more absorption/dispersion, or a beam that is less evenly spread.