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 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. Embodiments may beneficially separate the scanning beam from ghost light and/or be incorporated in image forming apparatuses.