Simultaneous Measurement of Out-of-Plane and In-Plane Displacements by Phase-Shifting Digital Holographic Interferometry

Abstract

In this paper, we apply phase-shifting digital holographic interferometry to simultaneous measurement for out-of-plane and in-plane displacements by employing two beam illuminations for an object. Phase-shifted holograms before and after displacements of the object using each of two beams are recorded by a CCD camera, separately. The complex amplitude at each pixel of the CCD plane is analyzed from the holograms taken with phase-shifting. The complex amplitude of he object is reconstructed from the complex amplitude distribution on the CCD plane using the Fresnel diffraction integral. Each directional phase difference distribution is obtained by calculating the phases before and after deformation for each directional beam. The phase distribution for out-of-plane displacements is obtained by calculating the sum of the two phase difference distributions. The phase distribution for in-plane displacements is obtained by calculating the difference of the two phase difference distributions. The phase values provide accurate displacement distribution information. Actually, when the object deforms in both out-of-plane and in-plane directions, it is possible to analyze the displacement distribution in each direction. The theory and an experiment are shown.

Multiple phase estimation via signal separation using a windowed Fourier transform in digital holographic interferometry

“…Recent improvements in lasers and digital data processing have created a demand for better performance from DHI, including expanding its capacity to achieve multidimensional measurements, possibly in a simultaneous manner, and with improved precision. Measurement techniques have been proposed [4][5][6][7][8][9] for the simultaneous measurement of the in-plane and out-of-plane displacement components. However, the complexity involved in these set-ups makes them less suitable for their application to practical measurement problems.…”

Measurement of in-plane and out-of-plane displacements and strains using digital holographic moiré

“…Finally, Ref. [14] considers sequentially recording a pair of digital holograms for each of the two object-reference beam pairs 756 R. Kulkarni et al used in the measurement system. However, the requirement of multiple frames and the use of sequential recording makes the method less relevant to the simultaneous measurement of multiple displacement components of a dynamic object.…”

Three‐dimensional Displacement Analysis by Windowed Phase‐shifting Digital Holographic Interferometry

“…In order to measure three‐dimensional displacement components, three‐directional illumination method or three‐directional observation method is usually employed [7,8]. Kolenovic et al measured three‐dimensional displacement using an endoscope with three object beams [7].…”

“…Kolenovic et al measured three‐dimensional displacement using an endoscope with three object beams [7]. The authors also proposed a method of simultaneous measurement of in‐plane and out‐of‐plane displacements using two‐beam illuminations [8]. Using this method, a measurement system was developed [9].…”