Patent ID: 9221272
Filing Date: 2015-12-29
Classification: B41J,G02B

Abstract:
1. An optical scanning device that forms images on a plurality of photoconductors, the optical scanning device comprising: a light-source unit that emits four light beams, each light beam corresponding to a respective one of the photoconductors; a deflector that rotates about a rotational axis and deflects the four light beams from the light-source unit, wherein the four light beams are all simultaneously deflected by the same surface of the deflector as each other; and an image-forming optical system that causes the light beams deflected by the deflector to each form a spot image on a corresponding scan target surface of each one of the photoconductors, the image-forming optical system including scanning lenses arranged on optical paths of the four light beams from the deflector to corresponding ones of the scan target surfaces, wherein the four light beams enter the deflector obliquely with respect to a plane extending orthogonal to the rotational axis of the deflector, a first light beam and a second light beam of the four light beams enter the deflector obliquely such that the first and second light beams travel in first directions to one side of the plane orthogonal to the rotational axis of the deflector, wherein the first and second light beams are present in an area to the one side of the plane orthogonal to the rotational axis of the deflector as the first and second light beams approach the deflector, the area to the one side of the plane being spaced from the plane in the direction of the rotational axis of the deflector, a third light beam and a fourth light beam of the four light beams enter the deflector obliquely such that the third and fourth light beams travel in second directions to the other side of the plane orthogonal to the rotational axis of the deflector, wherein the third and fourth light beams are present in an area to the other side of the plane orthogonal to the rotational axis of the deflector as the third and fourth light beams approach the deflector, the area to the other side of the plane being spaced from the plane in the direction of the rotational axis of the deflector, wherein the scanning lenses are arranged such that a direction of a curve in a scan line entering the scanning lenses is opposite, and to approximately the same degree, between scan lines of the first and second light beams on the one side of the plane orthogonal to the rotational axis of the deflector and between scan lines of the third and fourth light beams on the other side of the plane orthogonal to the rotational axis of the deflector, and a difference between A