Patent ID: 7170662

Claim:
An optical lens system, comprising: a plurality of optical lenses which cooperate with each other to transmit a laser beam deflected in a main scanning direction to scan an object in the main scanning direction, and which include a first lens which is formed of a resin and has a tilt correction function, and at least one second lens which is remoter from the object than the first lens on an optical path, the first lens, including: an effective lens portion which transmits the laser beam therethrough, the effective lens portion having an incidence surface to which the laser beam is incident in an optical-axis direction, and an outgoing surface from which the laser beam outgoes in the optical-axis direction, and at least one of the incidence surface and the outgoing surface being curved outward such that in a cross section of the first lens taken along a plane perpendicular to the main scanning direction, two opposite edge lines of the effective lens portion that are opposite to each other in the optical-axis direction and correspond to the incidence surface and the outgoing surface, respectively, include at least one outward curved line that is curved outward in the optical-axis direction, and at least one first ineffective lens portion, which does not transmit the laser beam therethrough, and which is located adjacent the effective lens portion in a sub-scanning direction perpendicular to the main scanning direction and the optical-axis direction, wherein in the cross section of the first lens, said at least one first ineffective lens portion does not project outward from the outward curved surface of the effective lens portion in the optical-axis direction.