# US 10,502,558 B2 · Curvature sensor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,502,558 B2 - Document ID: US10502558B2 - Status: Granted - Kind: B2 - Application number: 15/983,172 - Filed: 2018-05-18 - Published: 2018-09-20 - Granted: 2019-12-10 - Earliest claimed: 2015-11-20 - Assignees: Olympus Corporation - Applicants: Olympus Corporation - Inventors: Yasuo Sasaki; Eiji Yamamoto - Web page: https://patentgrep.com/patent/US10502558B2 ## CPC - A61B 1/009: {with bending or curvature detection of the insertion part} - G01B 11/255: for measuring radius of curvature {(measuring diameter G01B11/08)} - A61B 1/00165: {with light-conductive means, e.g. fibre optics (A61B1/07 takes precedence)} - G01B 11/18: {using photoelastic elements} - G01B 11/24: for measuring contours or curvatures - G02B 6/34: utilising prism or grating {(G02B6/293 takes precedence)} - G02B 6/02042: {Multicore optical fibres} - G02B 6/02076: {Refractive index modulation gratings, e.g. Bragg gratings} - G02B 6/022: {using mechanical stress, e.g. tuning by compression or elongation, special geometrical shapes such as "dog-bone" or taper (G02B6/02204 takes precedence; optical modulation using photo-elastic effect G02F1/0131)} - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) - G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract A curvature sensor includes a light source, a flexible light guide including cores, FBG sensors that are provided in the cores and constitute FBG sensor groups at predetermined positions along longitudinal axes of the cores. The curvature sensor includes a detector that detects an optical spectrum of light from the FBG sensors, and a processor that determines a bend position and a bend amount of the light guide. The FBG sensor groups include a first FBG sensor group and a second FBG sensor group next to it. FBG sensors in the first and second FBG sensor groups include gratings having first and second pitches. The first pitch is shorter than the second pitch and is closer to the second pitch than other pitches of gratings of FBG sensors that include gratings having pitches shorter than the second pitch. ## Claims ### Claim 1 A curvature sensor comprising: a light source configured to emit light; a flexible light guide comprising a plurality of cores disposed so as to maintain relative spaces, wherein the plurality of cores are configured to guide light emitted from the light source; a plurality of fiber Bragg grating (FBG) sensors provided in the respective one of the plurality of cores of the flexible light guide and constitute FBG sensor groups at predetermined positions along longitudinal axes of the plurality of cores, respectively, wherein each of the plurality of FBG sensors comprises a grating having a predetermined pitch configured to reflect light with a particular wavelength corresponding to the predetermined pitch in light guided by the plurality of cores; a detector configured to detect information on an optical spectrum of light reflected by the plurality of FBG sensors or light passing through the plurality of FBG sensors; and a processor configured to determine a bend position and a bend amount of the flexible light guide based on the information on the optical spectrum, wherein the FBG sensor groups positioned at the predetermined positions comprises a first FBG sensor group and a second FBG sensor group provided next to the first FBG sensor group in a longitudinal direction of the flexible light guide, wherein all FBG sensors included in the first FBG sensor group each comprises a first grating having a predetermined first pitch, wherein all FBG sensors included in the second FBG sensor group each comprises a second grating having a predetermined second pitch, the first pitch being shorter than the second pitch, and wherein a difference between the first pitch and the second pitch is less than a difference between each of pitches of gratings of FBG sensors in all FBG sensor groups that include gratings having pitches shorter than the second pitch and the second pitch. ### Claim 2 (depends on 1) The curvature sensor according to claim 1, further comprising a light brancher that distributes light from the light source to the plurality of cores, wherein the detector comprises sub-detectors configured to respectively detect light guided by the cores. ### Claim 3 (depends on 1) The curvature sensor according to claim 1, wherein several FBG sensor groups among the FBG sensor groups are arranged adjacently in a wavelength space, and Bragg wavelengths of FBG sensors included in each of the FBG sensor groups are coincident with one another. ### Claim 4 (depends on 3) The curvature sensor according to claim 3, wherein the FBG sensor groups are arranged adjacently in the wavelength space, and Bragg wavelengths of FBG sensors included in each of the FBG sensor groups are coincident with one another. ### Claim 5 (depends on 1) The curvature sensor according to claim 1, wherein the flexible light guide is configured to be provided along a length of a bendable elongated object. ### Claim 6 (depends on 5) The curvature sensor according to claim 5, wherein the plurality of cores extend along a length of the flexible light guide while maintaining relative spaces, and wherein the curvature sensor further comprises a tubular guide covering a periphery of the flexible light guide, wherein the tubular guide is configured to abut against a surface of the flexible light guide to prevent rotation of the flexible light guide relative to the elongated object. ### Claim 7 (depends on 1) The curvature sensor according to claim 1, wherein the flexible light guide is configured to be provided along a length of an insertion section of a scope of an endoscope system. ### Claim 8 (depends on 1) An endoscope system comprising: a scope; and the curvature sensor according to claim 1, wherein either one of the light source and the detector is disposed inside the scope. ### Claim 9 (depends on 1) An endoscope system comprising: a scope; and the curvature sensor according to claim 1, wherein the light source and the detector are disposed inside the scope.