Patent ID: 8004554

Claim:
A plastic optical element for guiding a scanned light beam in a main scanning direction and a sub-scanning direction, which is prepared by a molding method using a die, comprising: a main body including at least two optically functional surfaces, which are transfer surfaces formed by contact with transfer surfaces of the die and which include: a light entrance surface from which the light beam enters; and a light exit surface from which the light beam exits; and at least two ribs located on surfaces of the main body other than the at least two optically functional surfaces and extending in parallel in a longitudinal direction of the main body corresponding to the main scanning direction, wherein a recessed portion is present on a surface of at least one of the at least two ribs, the recessed portion has a side surface, which is a transfer surface, and a bottom surface, which is a non-transfer surface formed without contact with the transfer surfaces of the die, wherein a distance between the at least two optically functional surfaces of the main body is less than a length of the main body in the sub-scanning direction.