Fiber Bragg grating tactile sensor for imaging

A novel tactile sensor using an optical fiber Bragg grating (FBG) embedded in silicone for imaging is envisaged. The tactile sensor in contact with the surface, detects the force perpendicular to the surface in terms of change in wavelength of the grating through the elasticity of the polymer. As the tactile sensor encounters any discontinuity on the surface, the preloaded normal force/pressure is relieved and squeezing of the polymer in to the crack takes place. This results in increase in the reflected wavelength of the FBG. The paper describes the fabrication process of the tactile sensor and presents its potential in imaging. The validation of the tactile sensor is performed on notches of known widths and the results show that the variation of Full Width at Half Maxima (FWHM) with the scan distance can be used to quantify the notch width. The experimental results are verified using finite element simulation of the FBG based tactile sensor. Also, the mapping of surface discontinuities is demonstrated by scanning the sensor tangentially across a fatigue crack and the 3D image is reconstructed. The experimental results show that the sensor has good repeatability and increased spatial resolution, owing to its small foot print.