# US 11,906,725 B2 · Illumination lens, illumination optical system, and endoscope > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,906,725 B2 - Document ID: US11906725B2 - Status: Granted - Kind: B2 - Application number: 16/798,439 - Filed: 2020-02-24 - Published: 2020-08-27 - Granted: 2024-02-20 - Earliest claimed: 2019-02-27 - Assignees: FUJIFILM Corporation - Applicants: FUJIFILM Corporation - Inventors: Keisuke Harada - Web page: https://patentgrep.com/patent/US11906725B2 ## CPC - G02B 23/243: {Objectives for endoscopes} - G02B 23/2469: {using optical fibres} - A61B 1/0623: {for off-axis illumination} - G02B 9/06: two + components - G02B 19/0014: {at least one surface having optical power} - G02B 19/0047: {for use with a light source (G02B19/009, G02B19/0095 take precedence; details of lighting devices in general F21V; non-semiconductor lasers having optical devices external to the laser cavity H01S3/005)} - G02B 23/2461: {Illumination} - G02B 3/0075: {characterized by non-optical structures, e.g. having integrated holding or alignment means} - G02B 2003/0093: {characterised by the shape} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) ## Abstract An illumination lens consists of a first lens and a second lens that are arranged in this order from a light source side toward an irradiation target side. The surface of the first lens close to the light source side and the surface of the first lens close to the irradiation target side are spherical convex surfaces, and the surface of the second lens close to the light source side is a spherical convex surface. Conditional expression determined in advance about the radii of curvature of the surfaces of the first and second lenses is satisfied. ## Claims ### Claim 1 An illumination optical system of an endoscope, the illumination optical system comprising: an illumination lens consisting of a first lens and a second lens that are arranged in this order from a light source side toward an irradiation target side; and a point light source configured to emit a plurality of light rays to the illumination lens, wherein angles of the plurality of light rays incident on the illumination lens with respect to an optical axis of the illumination lens are different from each other, wherein the illumination lens is configured to directly receive the plurality of light rays from the point light source and cause all of the plurality of light rays to intersect on the irradiation target side at positions outside the second lens, wherein a surface of the first lens closest to the light source side and a surface of the first lens closest to the irradiation target side are spherical convex surfaces, a surface of the second lens closest to the light source side is a spherical convex surface, and in a case where a radius of curvature of the surface of the first lens closest to the light source side is denoted by Rf1, a radius of curvature of the surface of the first lens closest to the irradiation target side is denoted by Rr1, and a radius of curvature of the surface of the second lens closest to the light source side is denoted by Rf2, Conditional expression (1) is satisfied, 0.6 <  Rr ⁢ ⁢ 1 + Rf ⁢ ⁢ 1 Rr ⁢ ⁢ 1 - Rf ⁢ ⁢ 1 × Rf ⁢ ⁢ 1 Rf ⁢ ⁢ 2  < 6. ( 1 ) ### Claim 2 (depends on 1) The illumination optical system according to claim 1, wherein a surface of the second lens closest to the irradiation target side is a flat surface. ### Claim 3 (depends on 1) The illumination optical system according to claim 1, wherein light emitted from an optical fiber is incident on the illumination lens. ### Claim 4 (depends on 1) The illumination optical system according to claim 1, wherein Conditional expression (1-1) is satisfied, 0.65 <  Rr ⁢ ⁢ 1 + Rf ⁢ ⁢ 1 Rr ⁢ ⁢ 1 - Rf ⁢ ⁢ 1 × Rf ⁢ ⁢ 1 Rf ⁢ ⁢ 2  < 3. ( 1 ⁢ - ⁢ 1 ) ### Claim 5 (depends on 1) An endoscope comprising: the illumination optical system according to claim 1. ### Claim 6 (depends on 1) The illumination optical system according to claim 1, wherein in a case where a thickness of the second lens on the optical axis is denoted by t2, a distance on the optical axis between the surface of the first lens closest to the light source side and a surface of the second lens closest to the irradiation target side is denoted by TL, a focal length of the first lens is denoted by f1, and a focal length of the second lens is denoted by f2, Conditional expression (3) is satisfied, 0.6<(t2/TL)×(f1/f2)<6 (3). ### Claim 7 (depends on 6) The illumination optical system according to claim 6, wherein Conditional expression (3-1) is satisfied, 0.65<(t2/TL)×(f1/f2)<3 (3-1). ### Claim 8 (depends on 1) The illumination optical system according to claim 1, wherein in a case where a refractive index of the first lens with respect to a d line is denoted by N1 and a refractive index of the second lens with respect to the d line is denoted by N2, Conditional expression (5) is satisfied, 3.6