Whole field in-plane displacement measurement using all optical fiber phase-shifting ESPI

This paper presents a novel method for measuring whole field in-plane displacement by using optical fiber phase-shifting ESPI. A 1 x 4 single mode optical fiber beamsplitter is employed to split the laser beam into four beams of equal intensity. We use one pair of fibers to illuminate the diffuse target at equal angles in the horizontal plane so it is sensitive only to horizontal in-plan displacement. Another pair of optical fibers is set to be sensitive only to vertical in-plane displacement. The polarization directions of light emitted by fibers are same for each pair but are at right angle between pairs. The optical fibers are equal in length for each pair but are not equal between two pairs. In this case the speckles are interference itself for each pair fibers, respectively, so we can get the horizontal and vertical displacement components simultaneously. By means of fiber phase shift technique we can displacement of a thin metal plate, and the examples of the results obtained are shown to demonstrate obtain the quantitative data of whole field. This method has enabled to study the in-plane displacement of a thin metal plate, and the examples of the results obtained are shown to demonstrate the novel method.