Strain Measurement Based on Speeded-up Robust Feature Algorithm Applied to Microimages from a Smartphone-Based Microscope

• Published in: Sensors (Basel, Switzerland) Vol. 20; no. 10; p. 2805
• Main Authors: Xie, Botao, Li, Jinke, Zhao, Xuefeng
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 15-05-2020; MDPI
• Subjects: Accuracy; Bragg gratings; Construction accidents & safety; Experiments; Interferometry; M-estimator sample consensus (MSAC); Methods; microimages; Optical fibers; Outliers (statistics); Sensors; smartphone; Smartphones; speeded-up robust feature (SURF); Stability analysis; Standard error; Strain measurement; Structural health monitoring; speeded-up robust feature (SURF); smartphone; strain measurement; microimages; M-estimator sample consensus (MSAC)
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s20102805

The objective of this study is to evaluate and improve the accuracy and stability of a strain measurement method that uses the speeded-up robust feature (SURF) method to trace the displacement of feature points in microimages and obtain the strain in objects. The microimages were acquired using a smartphone with a portable microscope, which has a broad prospect of application. An experiment was performed using an unpacked optical fiber as the experimental carrier. The matching effect of the SURF method was analyzed in the microimage, and the M-estimator sample consensus (MSAC) algorithm was used to reject outliers generated by SURF. The results indicated that the accuracy of strain measurement using the proposed method is improved by modifying the feature point tracking method and measurement method. When compared with the fiber Bragg grating (FBG) data, the maximum standard error corresponded to 2.5 με, which satisfies the requirement of structural health monitoring (SHM) in practical engineering.