Optical scanners are configured so a principal ray of an incident beam from a light source device to a deflector and a principal ray of a scanning beam from the deflector to a scanned surface travel on the same side (or opposite sides) of an optical axis of an optical element(s) respectively wherein entrance and exit surfaces of the optical element(s) are both convex (or both concave) toward the deflector in the sub-scanning section. In various embodiments, the aforementioned principal rays travel on the same side, and surfaces are convex toward the deflector in the sub-scanning section. In various embodiments, the aforementioned principal rays travel on opposite sides, and surfaces are concave toward the deflector in the sub-scanning section. Embodiments may beneficially separate the scanning beam from ghost light and/or be incorporated in image forming apparatuses.