# US 2014/0198171 A1 · Weight-balanced polygonal mirror, light scanning unit using the polygonal mirror, 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 2014/0198171 A1 - Document ID: US20140198171A1 - Status: Published application - Kind: A1 - Application number: 14/211,761 - Filed: 2014-03-14 - Published: 2014-07-17 - Earliest claimed: 2010-12-02 - Assignees: Samsung Electronics Co., Ltd. - Applicants: Samsung Electronics Co., Ltd. - Inventors: Jin-kwon CHUN; Jae-hwan YOO; Won-young CHO; Heon-hee LIM; Ho-hyun HWANG - Web page: https://patentgrep.com/patent/US20140198171A1 ## CPC - G02B 26/12: using multifaceted mirrors - B41J 2/471: {using dot sequential main scanning by means of a light deflector, e.g. a rotating polygonal mirror} - G02B 5/09: Multifaceted or polygonal mirrors {, e.g. polygonal scanning mirrors; Fresnel mirrors} - G03G 15/04072: {by laser} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - B41J: TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS - G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY ## Abstract A light scanning unit includes a light source to emit a light beam; a polygonal mirror to deflect the light beam in a main scanning direction; and an imaging optical system to image the light beam onto a scanning surface. The polygonal mirror includes a plurality of reflection surfaces that are formed in an outer portion of the polygonal mirror and rotate around a rotational axis and an internal mirror surface that defines a hole. A ratio of an internal diameter d to an outer diameter D satisfies 0.1≦d/D≦0.3. The polygonal mirror is adhered to a motor unit that supports and rotates the polygonal mirror, using an adhesive. The internal mirror surface of the polygonal mirror defining the hole is point-bonded to the motor unit using the adhesive, and the point-bonding is conducted in a direction toward a corner of the reflection surfaces. ## Claims ### Claim 1 A light scanning unit comprising: a light source to emit a light beam; a polygonal mirror to deflect the light beam emitted from the light source, in a main scanning direction; and an imaging optical system to image the light beam deflected by the polygonal mirror, onto a scanning surface, wherein the polygonal mirror is formed of a plastic and comprises a plurality of reflection surfaces that are formed in an outer portion of the polygonal mirror and rotate around a rotational axis and an internal mirror surface that defines a hole, wherein a ratio of an internal diameter d to an outer diameter D satisfies 0.1≦d/D≦0.3, the polygonal mirror is assembled by being adhered to a motor unit that supports and rotates the polygonal mirror, using an adhesive, the internal mirror surface of the polygonal mirror defining the hole is point-bonded to the motor unit using the adhesive, and the point-bonding is conducted in a direction toward a corner of the reflection surfaces. ### Claim 2 (depends on 1) The light scanning unit of claim 1, wherein the outer diameter D satisfies 10 mm≦D≦30 mm. ### Claim 3 (depends on 2) The light scanning unit of claim 2, wherein the outer diameter D is 20 mm and the internal diameter d is 4 mm. ### Claim 4 (depends on 1) The light scanning unit of claim 1, wherein a thermal expansion coefficient of the plastic satisfies 40*10-6 [1 m/m·° C.]≦α≦400*10-6 [1 m/m·° C.]. ### Claim 5 (depends on 1) The light scanning unit of claim 1, wherein a groove is formed in the internal mirror surface to accommodate the adhesive. ### Claim 6 (depends on 5) The light scanning unit of claim 5, wherein the groove is formed in a direction toward a corner of the reflection surfaces. ### Claim 7 (depends on 5) The light scanning unit of claim 5, wherein the groove is formed to correspond to a vertical length of the internal mirror surface. ### Claim 8 (depends on 5) The light scanning unit of claim 5, wherein the groove is formed only in an upper portion of the internal mirror surface. ### Claim 9 (depends on 5) The light scanning unit of claim 5, wherein the groove is cylindrical or in the same polyhedral shape as the polygon mirror having the plurality of reflection surfaces. ### Claim 10 (depends on 5) The light scanning unit of claim 5, wherein a holder frame is coupled to a rotational axis of the motor unit, and a portion of the holder frame is inserted into the hole of the polygonal mirror, and the internal mirror surface of the polygonal mirror defining the hole and an outer surface of the holder frame facing the internal mirror surface are point-bonded using the adhesive. ### Claim 11 An image forming apparatus comprising: a light scanning unit comprising a light source to emit a light beam; a polygonal mirror to deflect the light beam emitted from the light source, in a main scanning direction; and an imaging optical system to image the light beam deflected by the polygonal mirror, onto a scanning surface; a developing unit comprising a photoconductor that is disposed at an imaging point of the light beam emitted from the light scanning unit, wherein an electrostatic latent image is formed on the photoconductor, and a developing roller that develops the electrostatic latent image formed on the photoconductor; and a transfer unit onto which an image developed by the developing unit is transferred, wherein the polygonal mirror is formed of a plastic and comprises a plurality of reflection surfaces that are formed in an outer portion of the polygonal mirror and rotate around a rotational axis and an internal mirror surface that defines a hole, wherein a ratio of an of an internal diameter d to an outer diameter D satisfies 0.1≦d/D≦0.3, the polygonal mirror is assembled by being adhered to a motor unit that supports and rotates the polygonal mirror, using an adhesive, the internal mirror surface of the polygonal mirror defining the hole is point-bonded to the motor unit using the adhesive, and the point-bonding is conducted in a direction toward a corner of the reflection surfaces.