# US 10,310,238 B2 · Magnification optical system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,310,238 B2 - Document ID: US10310238B2 - Status: Granted - Kind: B2 - Application number: 15/704,920 - Filed: 2017-09-14 - Published: 2018-01-04 - Granted: 2019-06-04 - Earliest claimed: 2012-11-05 - Assignees: Ricoh Company, Ltd. - Applicants: Ricoh Company, Ltd. - Inventors: Hibiki Tatsuno; Kiichiro Nishina; Yasuyuki Shibayama; Takanobu Osaka; Makoto Hirakawa - Web page: https://patentgrep.com/patent/US10310238B2 ## CPC - G02B 13/16: for use in conjunction with image converters or intensifiers {, or for use with projectors, e.g. objectives for projection TV} - G02B 7/04: with mechanism for focusing or varying magnification - G02B 7/10: by relative axial movement of several lenses, e.g. of varifocal objective lens - G02B 17/08: Catadioptric systems {(used in non-imaging applications G02B19/00)} - G03B 21/147: {Optical correction of image distortions, e.g. keystone} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - G03B: APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR (optical parts of such apparatus G02B; photosensitive materials or processes for photographic purposes G03C; apparatus for processing exposed photographic materials G03D) ## Abstract A magnification optical system forms an enlarged image of an object. It includes a refractive optical system including a plurality of lens groups; and a mirror train including a curved mirror, arranged in this order from an object side, a first focus structure configured to move the respective lens groups of the refractive optical system by different amounts along a normal line of a conjugate surface on the object side, and a second focus structure configured to move the respective lens groups along the normal line of the conjugate surface on the object side by different amounts from those of the first focus structure. ## Claims ### Claim 1 A magnification optical system that enlarges an image of an object, the magnification optical system comprising: a refractive optical system including, in order from an object side to an enlarged side, a first lens group having a positive power, a second lens group, a third lens group including a plurality of lenses, and a fourth lens group; a curved mirror that reflects light from the refractive optical system; and a focus structure that moves the third lens group and the fourth lens group and does not move the first lens group and the curved mirror. ### Claim 2 (depends on 1) The magnification optical system according to claim 1, wherein the focus structure further moves the second lens group, and the focus structure moves the second lens group, the third lens group, and the fourth lens group by different amounts. ### Claim 3 (depends on 2) The magnification optical system according to claim 2, wherein the focus structure includes a first focus structure that moves the second lens group and the third lens group, and a second focus structure that moves the fourth lens group. ### Claim 4 (depends on 3) The magnification optical system according to claim 3, wherein the second focus structure is fixed after a focus adjustment is performed by the second focus structure. ### Claim 5 (depends on 1) The magnification optical system according to claim 1, wherein the fourth lens group comprises a single lens that is closer to the curved mirror in the refractive optical system than each of the other lenses in the refractive optical lens system. ### Claim 6 (depends on 1) The magnification optical system according to claim 1, wherein the fourth lens group is adjacent to the third lens group. ### Claim 7 (depends on 6) The magnification optical system according to claim 6, wherein the third lens group is adjacent to the second lens group. ### Claim 8 A magnification optical system that enlarges an image of an object, the magnification optical system comprising: a first optical system including a plurality of lens groups; a second optical system including a curved mirror that reflects light received from the first optical system; and a focus structure, wherein the plurality of lens groups includes, in order from an object side to an enlarged side, a first lens group, a second lens group, a third lens group, and a fourth lens group, the focus structure does not move the first lens group and the curved mirror, and the focus structure moves the third lens group and the fourth lens group to change an interval between the third lens group and the fourth lens group. ### Claim 9 (depends on 8) The magnification optical system according to claim 8, wherein the focus structure further moves the second lens group, and the focus structure moves the second lens group, the third lens group, and the fourth lens group by different amounts. ### Claim 10 (depends on 9) The magnification optical system according to claim 9, wherein the focus structure includes a first focus structure that moves the second lens group and the third lens group, and a second focus structure that moves the fourth lens group. ### Claim 11 (depends on 10) The magnification optical system according to claim 10, wherein the second focus structure is fixed after a focus adjustment is performed by the second focus structure. ### Claim 12 (depends on 8) The magnification optical system according to claim 8, wherein the fourth lens group comprises a single lens that is closer to the curved mirror in the refractive optical system than each of the other lenses in the first optical system. ### Claim 13 (depends on 10) The magnification optical system according to claim 10, wherein the fourth lens group is adjacent to the third lens group. ### Claim 14 (depends on 13) The magnification optical system according to claim 13, wherein the third lens group is adjacent to the second lens group. ### Claim 15 (depends on 1) The magnification optical system according to claim 1, wherein the focus structure moves the third lens group and the fourth lens group to change an interval between the third lens group and the fourth lens group.