# US 10,502,552 B2 · Field splitter for three-dimensional strain measurement > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,502,552 B2 - Document ID: US10502552B2 - Status: Granted - Kind: B2 - Application number: 15/745,811 - Filed: 2016-07-25 - Published: 2018-08-02 - Granted: 2019-12-10 - Earliest claimed: 2015-08-27 - Assignees: Illinois Tool Works Inc. - Applicants: Illinois Tool Works Inc. - Inventors: Christian J. Hoehl; Martin A. Peterson; Roy D. Allen - Web page: https://patentgrep.com/patent/US10502552B2 ## CPC - G01B 11/16: for measuring the deformation in a solid, e.g. optical strain gauge - G02B 27/10: Beam splitting or combining systems (polarising systems G02B27/28; mixing and splitting light signals using optical waveguides G02B6/28; {beam shaping, e.g. changing the cross-sectional area, by dividing or superposing multiple light beams G02B27/0905}) - G06T 7/0004: {Industrial image inspection} - G06T 7/97: {Determining parameters from multiple pictures (depth or shape recovery from multiple images G06T7/55; stereo camera calibration G06T7/85)} - G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL ## Abstract The present disclosure provides an apparatus and method which uses a field splitter or a beam splitter for the purpose combining two different views of a materials testing sample under materials testing into a single image. This allows for three-dimensional strain measurement in the context of material/compound testing. In particular, the time and stress dependent change in gauge length can be tracked and calculated in order to calculate the time and stress dependent strain. The method and apparatus allows imaging on a single image sensor for the three-dimensional strain calculation. ## Claims ### Claim 1 A device for strain measurement and calculation, including: a field splitter, including first and second objectives, for receiving first and second images of a materials testing sample through the respective first and second objectives, from first and second angles and combining the first and second images into a single composite image; a first device for receiving the single composite image and generating a single digital image; and a second device for receiving the single digital image and performing strain calculations with respect to the material testing sample by measuring a selected gauge length and subsequently performing a three-dimensional calculation to calculate at least one change in the selected gauge length in order to calculate strain. ### Claim 2 (depends on 1) The device for strain measurement and calculation of claim 1 wherein wherein the at least one change in the selected gauge length is a time-dependent change in the selected gauge length in order to calculate a time-dependent strain. ### Claim 3 (depends on 1) The device for strain measurement and calculation of claim 1 wherein the second device for receiving the single digital image and performing strain calculations with respect to a material testing sample defines the gauge length as being a distance between first and second video targets on a materials testing sample, a distance between first and second video targets increasing under tensile load. ### Claim 4 (depends on 3) The device for strain measurement and calculation of claim 3 wherein the field splitter includes a housing, the housing including first and second optical pathways for receiving the respective first and second images, the housing further including a third optical pathway with an associated mount for an optical lens, the single composite image being transmitted through the third optical pathway. ### Claim 5 (depends on 4) The device for strain measurement and calculation of claim 4 wherein the first device for receiving the single composite image and generating a single digital image includes a lens that is mounted on the associated mount for an optical lens. ### Claim 6 (depends on 4) The device for strain measurement and calculation of claim 4 wherein the first device for receiving the single composite image and generating a single digital image is a digital camera. ### Claim 7 A method of strain measurement and calculation, including the steps of: providing a field splitter, including first and second objectives, for receiving first and second images of a materials testing sample from first and second angles through the respective first and second objectives; combining the first and second images into a single composite image; receiving the single composite image and generating a single digital image; and receiving the single digital image; and performing strain calculations on the single digital image with respect to the material testing sample, further including the step of measuring a selected gauge length and subsequently performing a three-dimensional calculation to calculate at least one change in the selected gauge length in order to calculate strain. ### Claim 8 (depends on 7) The method of strain measurement and calculation of claim 7 wherein the at least one change in the selected gauge length is a time-dependent change in the selected gauge length in order to calculate a time-dependent strain. ### Claim 9 (depends on 7) The method of strain measurement and calculation of claim 7 wherein the step of performing strain calculations with respect to a material testing sample further includes the step of defining the gauge length as being a distance between first and second video targets on a materials testing sample, a distance between first and second video targets increasing under tensile load. ### Claim 10 (depends on 9) The method of strain measurement and calculation of claim 9 further including the step of providing a housing for the field splitter, the housing including first and second optical pathways for receiving the respective first and second images, the housing further including a third optical pathway with an associated mount for an optical lens, the single composite image being transmitted through the third optical pathway. ### Claim 11 (depends on 10) The method of strain measurement and calculation of claim 10 wherein the step of receiving the single composite image includes the step of providing a lens that is mounted on the associated mount for an optical lens. ### Claim 12 (depends on 10) The method of strain measurement and calculation of claim 10 wherein the steps of receiving the single composite image and generating a single digital image are performed by a digital camera.