TEMPERATURE INSENSITIVE FIBER-OPTIC TORQUE AND STRAIN SENSOR

摘要

The present invention provides a simple design for a temperature-insensitiv e extrinsic polarimetric strain sensor. The sensing element is a thin sheet of photoelastic material that is bonded to the test object. It is illuminated with linearly polarized light with the polarization direction at 45 degrees relative to the strain-induced fast and slow axes in the photoelastic material. The sens or measures the difference between the strains along these two orthogonal directions. The reduced sensitivity of the sensor to temperature results fro m the fact that the illumination is perpendicular to the surface of the test objec t. All polarization components that are parallel to the surface will experience identical refractive index changes due to thermal effects. Consequently, a measurement of the difference in strains along two directions in the surface plane is insensitive to temperature.