# US 2026/0086331 A1 · Optical system and imaging apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2026/0086331 A1 - Document ID: US20260086331A1 - Status: Published application - Kind: A1 - Application number: 19/301,612 - Filed: 2025-08-15 - Published: 2026-03-26 - Earliest claimed: 2024-09-24 - Assignees: Tamron Co., Ltd. - Applicants: Tamron Co., Ltd. - Inventors: Tomohiro KOBAYASHI - Web page: https://patentgrep.com/patent/US20260086331A1 ## CPC - G02B 13/0045: {having five or more lenses} - G02B 7/025: {using glue} - G02B 13/006: {at least one element being a compound optical element, e.g. cemented elements} - H04N 23/55: Optical parts specially adapted for electronic image sensors; Mounting thereof - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract An optical system includes: a first lens group; and a rear group that has a plurality of lens groups, the first lens group and the rear group being arranged in order from an object side, wherein a spacing between lens groups which are adjacent to each other changes during focusing, the rear group includes a first focus group which has a negative refractive power and moves during focusing, and a second focus group which has a negative refractive power and moves during focusing, at least one lens group P having a positive refractive power is provided between the first focus group and the second focus group, the lens group P includes a subgroup PN having a negative refractive power at a position closest to the object side, and predetermined conditional formulae are satisfied. An imaging apparatus includes: the optical system, and an image sensor. ## Claims ### Claim 1 An optical system comprising: a first lens group; and a rear group that has a plurality of lens groups, the first lens group and the rear group being arranged in order from an object side, wherein the rear group includes a first focus group which has a negative refractive power and moves during focusing, and a second focus group which has a negative refractive power and moves during focusing, at least one lens group P having a positive refractive power is provided between the first focus group and the second focus group, the lens group P includes a subgroup PN having a negative refractive power at a position closest to the object side, and following formulae are satisfied: 0.3 < ❘ "\[LeftBracketingBar]" fP / fPN ❘ "\[RightBracketingBar]" ( 1 ) 0.05 < ❘ "\[LeftBracketingBar]" ( 1 - β ⁢ f ⁢ 1 × β ⁢ f ⁢ 1 ) × β ⁢ f ⁢ 1 ⁢ r × β ⁢ f ⁢ 1 ⁢ r / Fno < 2. ( 2 ) here, fP is a focal length of the lens group P, fPN is a focal length of the subgroup PN, βf1 is a lateral magnification of the first focus group at infinity focus, βf1r is a lateral magnification at infinity focus of all lenses arranged on an image side of the first focus group, and Fno is an open F-number of the optical system at infinity focus. ### Claim 2 (depends on 1) The optical system according to claim 1 satisfying a following conditional formula: 0.05 < ❘ "\[LeftBracketingBar]" ( 1 - β ⁢ f ⁢ 2 × β ⁢ f ⁢ 2 ) × β ⁢ f ⁢ 2 ⁢ r × β ⁢ f ⁢ 2 ⁢ r ❘ "\[RightBracketingBar]" / Fno < 2. ( 3 ) here, βf2 is a lateral magnification of the second focus group at infinity focus, and βf2r is a lateral magnification at infinity focus of all lenses arranged on an image side of the second focus group. ### Claim 3 (depends on 1) The optical system according to claim 1 satisfying a following conditional formula: 0.1 < fP / f < 2. ( 4 ) here, f is a focal length of the optical system at infinity focus. ### Claim 4 (depends on 1) The optical system according to claim 1 satisfying a following conditional formula: - 1. < ff ⁢ 1 / f < - 0.1 ( 5 ) here, ff1 is a focal length of the first focus group, and f is a focal length of the optical system at infinity focus. ### Claim 5 (depends on 1) The optical system according to claim 1 satisfying a following conditional formula: - 1. < ff ⁢ 2 / f < - 0.1 ( 6 ) here, ff2 is a focal length of the second focus group, and f is a focal length of the optical system at infinity focus. ### Claim 6 (depends on 1) The optical system according to claim 1, wherein the first lens group has a positive refractive power, and a following formula is satisfied: 0.05 < f ⁢ 1 / f < 1. ( 7 ) here, f1 is a focal length of the first lens group, and f is a focal length of the optical system at infinity focus. ### Claim 7 (depends on 1) The optical system according to claim 1, wherein the first focus group and the second focus group respectively move toward the image side during focusing from infinity to a minimum object distance, and following formulae are satisfied: - 1. < m ⁢ 1 / ff ⁢ 1 < - 0.2 ( 8 ⁢ a ) - 1. < m ⁢ 2 / ff ⁢ 2 < - 0.2 ( 8 ⁢ b ) here, m1 is a movement amount of the first focus group during focusing from infinity to the minimum object distance, m2 is a movement amount of the second focus group during focusing from infinity to the minimum object distance, ff1 is a focal length of the first focus group, ff2 is a focal length of the second focus group, and a moving direction from the object side to the image side is positive. ### Claim 8 (depends on 1) The optical system according to claim 1, wherein the subgroup PN includes a single lens or a cemented lens formed by cementing two or more lenses. ### Claim 9 (depends on 1) The optical system according to claim 1, wherein the first focus group includes a single lens or a cemented lens formed by cementing two or more lenses. ### Claim 10 (depends on 1) The optical system according to claim 1, wherein the second focus group includes a single lens or a cemented lens formed by cementing two or more lenses. ### Claim 11 (depends on 1) An imaging apparatus comprising: the optical system according to claim 1, and a solid-state image sensor that converts an optical image formed by the optical system into an electrical signal. ### Claim 12 (depends on 2) An imaging apparatus comprising: the optical system according to claim 2, and a solid-state image sensor that converts an optical image formed by the optical system into an electrical signal. ### Claim 13 (depends on 3) An imaging apparatus comprising: the optical system according to claim 3, and a solid-state image sensor that converts an optical image formed by the optical system into an electrical signal. ### Claim 14 (depends on 4) An imaging apparatus comprising: the optical system according to claim 4, and a solid-state image sensor that converts an optical image formed by the optical system into an electrical signal. ### Claim 15 (depends on 5) An imaging apparatus comprising: the optical system according to claim 5, and a solid-state image sensor that converts an optical image formed by the optical system into an electrical signal. ### Claim 16 (depends on 6) An imaging apparatus comprising: the optical system according to claim 6, and a solid-state image sensor that converts an optical image formed by the optical system into an electrical signal. ### Claim 17 (depends on 7) An imaging apparatus comprising: the optical system according to claim 7, and a solid-state image sensor that converts an optical image formed by the optical system into an electrical signal. ### Claim 18 (depends on 8) An imaging apparatus comprising: the optical system according to claim 8, and a solid-state image sensor that converts an optical image formed by the optical system into an electrical signal. ### Claim 19 (depends on 9) An imaging apparatus comprising: the optical system according to claim 9, and a solid-state image sensor that converts an optical image formed by the optical system into an electrical signal. ### Claim 20 (depends on 10) An imaging apparatus comprising: the optical system according to claim 10, and a solid-state image sensor that converts an optical image formed by the optical system into an electrical signal.