Convex lens: In the case of a convex lens, the rays passing parallel to the principal axis converge to a given point. That given point is termed as the principal focus of a convex lens. Concave lens: In the case of a concave lens, the light rays which diverge from the point appear ...
deflector and a principal ray of a scanning beam from the deflector to a scanned surface travel on the opposite sides of an optical axis of an optical element(s) wherein entrance and exit surfaces of the optical element(s) are both concave toward the deflector in the sub-scanning section....
incident beam passes in a sub-scanning section, and wherein both the entrance surface and the exit surface of the at least one imaging optical element constituting the second optical system through which the incident beam passes are concave toward the deflecting device in the sub-scanning section...