# US 2008/0198370 A1 · Method and Device For Measuring the Concentricity of an Optical Fiber Core > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2008/0198370 A1 - Document ID: US20080198370A1 - Status: Published application - Kind: A1 - Application number: 11/997,408 - Filed: 2006-07-11 - Published: 2008-08-21 - Earliest claimed: 2005-08-05 - Assignees: Data-Pixel - Inventors: Loic Cherel - Web page: https://patentgrep.com/patent/US20080198370A1 ## CPC - G01M 11/33: {with a light emitter being disposed at one fibre or waveguide end-face, and a light receiver at the other end-face} - G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR ## Abstract Device for measuring the concentricity of the core 21 of an optical fiber 19 relative to a reference axis 22, comprising a means for determining the position of the intersection of the reference axis 22 with an optical face 23 on the end of the optical fiber 19, a means 17 for injecting light into the core 21 of the optical fiber 19, an objective 30 and a means 4 for observing, in a plane 5 conjugate with the optical face 23, the light emitted by the core 21 of the optical fiber 19, characterized in that the objective 30 has a numerical aperture sin β smaller than the numerical aperture sin α of the optical fiber to be measured. ## Claims ### Claim at position 1 1-12. (canceled) ### Claim 13 A device for measuring the position, especially the concentricity, of the core (21) of an optical fiber (19) relative to a reference axis (22), comprising a means for determining the position of the intersection of the reference axis (22) with an optical face (23) on the end of the optical fiber (19), a means (17) for injecting light into the core (21) of the optical fiber (19), an objective (30) and a means (4) for observing, in a plane (5) conjugate with the optical face (23), the light emitted by the core (21) of the optical fiber (19), characterized in that the objective (30) has a numerical aperture (sin β) smaller than the numerical aperture (sin α) of the optical fiber to be measured. ### Claim 14 (depends on 13) The device as claimed in claim 13, in which the numerical aperture (sin β) of the objective (30) is less than 0.11, or preferably less than 0.08 or in particular less than 0.06. ### Claim 15 (depends on 13) The device as claimed in claim 13, in which the numerical aperture (sin β) of the objective (30) is greater than 0.01, or preferably greater than 0.02 or in particular greater than 0.03. ### Claim 16 (depends on 13) The device as claimed in claim 13, in which the observation means is a digital camera sensitive to the light of the injection means (17). ### Claim 17 (depends on 13) The device as claimed in claim 13, intended for measuring the concentricity of the core of the fiber of an optical connector, the reference axis (22) of which is defined by an outside diameter (20) of a ferrule (18) of the optical connector, the device comprising a means for pivoting the optical face (23) relative to the outside diameter (20) of the ferrule (18), a means for calculating the position (14) of the center of the optical core (21) for each of the positions of the optical face (23), and a means for calculating the diameter of the circle passing through said positions of the center of the optical core (21). ### Claim 18 (depends on 13) The device as claimed in claim 13, in which the optical axis (31) of the objective (30) is approximately aligned with the reference axis (22) and the numerical aperture (sin β) of the objective (30) is obtained by a diaphragm (28) positioned in the image focal plane (3) of the objective (30). ### Claim 19 (depends on 13) The device as claimed in claim 13, in which the numerical aperture (sin β) of the objective (30) is obtained by a pupil positioned on the transverse entry plane of the objective (30). ### Claim 20 A method for measuring the concentricity of the core (21) of an optical fiber (19) relative to a reference axis (22), the optical fiber (19) having an optical face (23) at one end, in which method light is injected into the core (21) of the optical fiber (19), the light emitted by the core (21) is observed by means of an objective (30) and the position of the intersection of the reference axis (22) with the optical face (23) is determined, characterized in that the propagation modes that are peripheral to the central axis (31) of the objective (30) are filtered out. ### Claim 21 (depends on 20) The method as claimed in claim 20, using an objective (30) the numerical aperture (sin β) of which is smaller than the numerical aperture (sin α) of the optical fiber (19) to be measured. ### Claim 22 (depends on 20) The method as claimed in claim 20, in which the determination of the position of the intersection of the reference axis (22) with the optical face (23) includes a first step in which the reference axis (22) of the fiber (19) to be measured is positioned relative to the objective (30) and a first position (32a) of the center of the light spot (27a) emitted by the fiber (19) is measured in an image plane (5) of the objective (30) and then, in a second and a third step, the fiber (19) is pivoted in two other angular positions about the reference axis (22), a second position (32b) and a third position (32c) of the center of the emitted light spot are measured and the center of the circle passing through said three positions (32a, 32b, 32c) is calculated. ### Claim 23 (depends on 20) The method as claimed in claim 20, which includes a prior step in which the position of the intersection of the reference axis (22) with the optical face (23) is determined by means of a first optical fiber, said position is stored and then the reference diameter (20) of the optical fiber to be measured is repositioned so that the reference axis (22) of the fiber to be measured is in the identical position to the reference axis (22) of the first fiber. ### Claim 24 (depends on 20) The method as claimed in claim 20, intended for an optical connector (16), the reference axis (22) of which is defined by a reference diameter (20) relative to which an optical face (23) is fixed, in which method the position of the intersection of the reference axis (22) with the optical face (23) is determined by illuminating the diameter (20) and by calculating the position of the center of said diameter (20). ### Claim 25 (depends on 21) The method as claimed in claim 21, in which the determination of the position of the intersection of the reference axis (22) with the optical face (23) includes a first step in which the reference axis (22) of the fiber (19) to be measured is positioned relative to the objective (30) and a first position (32a) of the center of the light spot (27a) emitted by the fiber (19) is measured in an image plane (5) of the objective (30) and then, in a second and a third step, the fiber (19) is pivoted in two other angular positions about the reference axis (22), a second position (32b) and a third position (32c) of the center of the emitted light spot are measured and the center of the circle passing through said three positions (32a, 32b, 32c) is calculated. ### Claim 26 (depends on 21) The method as claimed in claim 21, which includes a prior step in which the position of the intersection of the reference axis (22) with the optical face (23) is determined by means of a first optical fiber, said position is stored and then the reference diameter (20) of the optical fiber to be measured is repositioned so that the reference axis (22) of the fiber to be measured is in the identical position to the reference axis (22) of the first fiber. ### Claim 27 (depends on 21) The method as claimed in claim 21, intended for an optical connector (16), the reference axis (22) of which is defined by a reference diameter (20) relative to which an optical face (23) is fixed, in which method the position of the intersection of the reference axis (22) with the optical face (23) is determined by illuminating the diameter (20) and by calculating the position of the center of said diameter (20). ### Claim 28 (depends on 14) The device as claimed in claim 14, in which the numerical aperture (sin β) of the objective (30) is greater than 0.01, or preferably greater than 0.02 or in particular greater than 0.03. ### Claim 29 (depends on 14) The device as claimed in claim 14, in which the observation means is a digital camera sensitive to the light of the injection means (17). ### Claim 30 (depends on 14) The device as claimed in claim 14, in which the optical axis (31) of the objective (30) is approximately aligned with the reference axis (22) and the numerical aperture (sin β) of the objective (30) is obtained by a diaphragm (28) positioned in the image focal plane (3) of the objective (30). ### Claim 31 (depends on 17) The device as claimed in claim 17, in which the optical axis (31) of the objective (30) is approximately aligned with the reference axis (22) and the numerical aperture (sin β) of the objective (30) is obtained by a diaphragm (28) positioned in the image focal plane (3) of the objective (30). ### Claim 32 (depends on 14) The device as claimed in claim 14, in which the numerical aperture (sin β) of the objective (30) is obtained by a pupil positioned on the transverse entry plane of the objective (30).