A curved mirror is a mirror with a curved reflecting surface ,
IODA built a cylindrical glass lens BK-7 with a very precise convex curvature to be used by a camera in order to obtain a wide-angle view.
When a beam of paraxial rays and parallel to the optical axis is reflected
from a convex cylindrical mirror, the reflected rays seem to come from the fire F of the mirror.
R and f indicate the radius, respectively of curvature and focal distance
of the mirror .