Diffraction Strain Sensor for Micromeasurements

摘要

In this paper, a novel compact optical diffraction strain sensor using medium density grating foil (500 lines/mm) and high-density diffractive grating (1200 lines/mm) is presented. The grating attached on the surface of a specimen is illuminated by a focused laser beam. The centroids of diffracted beam spots fro mthe grating are automatically determiend with two position-sensitivie detector (PSD) sensors connected to a personal computer. The shift of second-order diffracted beam spots due to the specimen deformation is then detected. The influences of noise sources and system geometry on system performances, such as sensitivity, spatial resolution, and strain range and measurement linearity are discussed. Strain sensitivity of 1 micro-strain can be achieved. The spatial resolution for strain measurement of 0.4 mm is attainable. The system can be used for continuous measurement and for both static and dynamic test.