# US 2013/0278704 A1 · Optical scanning apparatus and image forming apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0278704 A1 - Document ID: US20130278704A1 - Status: Published application - Kind: A1 - Application number: 13/869,268 - Filed: 2013-04-24 - Published: 2013-10-24 - Earliest claimed: 2012-04-24 - Assignees: Canon Kabushiki Kaisha - Applicants: Canon Kabushiki Kaisha - Inventors: Hidekazu Shimomura - Web page: https://patentgrep.com/patent/US20130278704A1 ## CPC - G02B 26/10: Scanning systems - G02B 26/123: {Multibeam scanners, e.g. using multiple light sources or beam splitters} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract An optical scanning apparatus includes a light source, a deflector that deflects a light beam in a main scanning direction, an incident optical system that makes the light beam enter the deflecting surface in a sub-scanning section, and an imaging optical system that includes at least one imaging optical element and condenses the light beam onto a surface to be scanned, in which at least one of an incident surface and an exit surface of the at least one imaging optical element is decentered in the sub-scanning section such that an origin position line exists in a region sandwiched between marginal rays at two sub-scanning direction ends of the light beam, the origin position line being extended in the main scanning direction and passing through an origin of an aspherical surface formula defining a surface shape of each of the incident surface and the exit surface in the sub-scanning section. ## Claims ### Claim 1 An optical scanning apparatus comprising: a light source; a deflector that deflects, by a deflecting surface, a light beam emitted by the light source in a main scanning direction for scanning; an incident optical system that makes the light beam emitted by the light source obliquely enter the deflecting surface of the deflector in a sub-scanning section perpendicular to the main scanning direction; and an imaging optical system that includes at least one imaging optical element and condenses the light beam deflected by the deflecting surface of the deflector onto a surface to be scanned, wherein at least one of an incident surface and an exit surface of the at least one imaging optical element is decentered in the sub-scanning section including an optical axis of the imaging optical system such that an origin position line exists in a region sandwiched between marginal rays at two sub-scanning direction ends of the light beam deflected by the deflecting surface of the deflector, the origin position line being extended in the main scanning direction and passing through an origin of an aspherical surface formula defining a surface shape of each of the incident surface and the exit surface in the sub-scanning section including the optical axis of the imaging optical system. ### Claim 2 (depends on 1) An apparatus according to claim 1, wherein the at least one imaging optical element comprises an imaging optical element optically closest to the surface to be scanned. ### Claim 3 (depends on 1) An apparatus according to claim 1, wherein at least one of the incident surface and the exit surface of the at least one imaging optical element is tilted and decentered in the sub-scanning section including the optical axis of the imaging optical system, and a tilt angle of the at least one of the incident surface and the exit surface changes in the main scanning direction so as to make bending of a scanning locus of the light beam on the surface to be scanned small. ### Claim 4 (depends on 1) An apparatus according to claim 1, wherein a power of the at least one imaging optical element in the sub-scanning section changes in the main scanning direction so as to make bending of a scanning locus of the light beam on one of the incident surface and the exit surface small. ### Claim 5 (depends on 4) An apparatus according to claim 4, wherein when the power in the sub-scanning section including the optical axis of the imaging optical system is positive, the positive power becomes strong toward an end in the main scanning direction, and wherein when the power in the sub-scanning section including the optical axis of the imaging optical system is negative, the negative power becomes weak toward the end in the main scanning direction. ### Claim 6 (depends on 1) An apparatus according to claim 1, wherein at least one of the incident surface and the exit surface of the at least one imaging optical element is decentered in the sub-scanning section including the optical axis of the imaging optical system such that the origin position line is set across a principal ray of the light beam deflected by the deflector. ### Claim 7 (depends on 1) An apparatus according to claim 1, wherein at least one of the incident surface and the exit surface of the at least one imaging optical element has a non-arc shape in the sub-scanning section. ### Claim 8 (depends on 1) An apparatus according to claim 1, wherein the at least one imaging optical element comprises a multi-stage lens that condenses a plurality of light beams onto corresponding different surfaces to be scanned. ### Claim 9 (depends on 1) An apparatus according to claim 1, wherein the at least one imaging optical element is configured to have a thickness changing between one end side and an opposing other end side in a widthwise direction. ### Claim 10 (depends on 1) An apparatus according to claim 1, wherein the light source comprises a plurality of light-emitting portions, the imaging optical system condenses a plurality of light beams from the plurality of light-emitting portions onto a plurality of corresponding surfaces to be scanned, and the at least one imaging optical element comprises an imaging optical element arranged on each of optical paths of the plurality of light beams. ### Claim 11 An image forming apparatus comprising: an optical scanning apparatus including a light source, a deflector that deflects, by a deflecting surface, a light beam emitted by the light source in a main scanning direction for scanning, an incident optical system that makes the light beam emitted by the light source obliquely enter the deflecting surface of the deflector in a sub-scanning section perpendicular to the main scanning direction, and an imaging optical system that includes at least one imaging optical element and condenses the light beam deflected by the deflecting surface of the deflector onto a surface to be scanned, wherein at least one of an incident surface and an exit surface of the at least one imaging optical element is decentered in the sub-scanning section including an optical axis of the imaging optical system such that an origin position line exists in a region sandwiched between marginal rays at two sub-scanning direction ends of the light beam deflected by the deflecting surface of the deflector, the origin position line being extended in the main scanning direction and passing through an origin of an aspherical surface formula defining a surface shape of each of the incident surface and the exit surface in the sub-scanning section including the optical axis of the imaging optical system; a developer that develops, as a toner image, an electrostatic latent image formed on a photosensitive member arranged on the surface to be scanned by the light beam scanned by the optical scanning apparatus; a transfer device that transfers the developed toner image to a transfer material; and a fixer that fixes the transferred toner image to the transfer material. ### Claim 12 (depends on 11) An image forming apparatus according to claim 11, further comprising a printer controller that converts a color signal input from an external device into image data.