Papers by Author: Motoharu Fujigaki

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Authors: Shien Ri, Motoharu Fujigaki, Yoshiharu Morimoto
Authors: Yoshiharu Morimoto, Motoharu Fujigaki, Akihiro Masaya, Hiroyuki Kondo, Tatsuya Inuzuka
Abstract: Sampling moiré method is useful to measure shape, displacement and strain distributions of multi-functional materials and structures. When a specimen grating pattern on an object is recorded by a digital camera, a moiré fringe pattern is obtained by sampling the digitized grating image with a constant pixel pitch. The method can analyze phase values from one image of a grating pattern. By using this sampling moiré method, the displacement measurement of land is analyzed to develop a landslide prediction system. The theory and the application for measuring the displacement of land are shown in this paper.
Authors: Qian Gao, Motoharu Fujigaki, Yoshiharu Morimoto
Authors: Yoshiharu Morimoto, Toru Matui, Motoharu Fujigaki
Abstract: In order to measure 3D displacement components and surface strain distributions of objects, three systems for digital holographic interferometry were developed. In this study, these three systems are introduced and the applications to measurement of 3D displacement components and surface strain distributions of cantilevers are shown.
Authors: Hitomi Matsukawa, Motoharu Fujigaki, Toru Matui, Yoshiharu Morimoto
Abstract: Phase-shifting digital holography can be used for displacement measurement instead of strain gauge. Our research group is developing the measurement equipment for phase-shifting digital holography. Generally, in the measurement equipment, piezo stages are used as phaseshifting devices. But the piezo stage is expensive. Cheaper and smaller phase-shifting device is required in order to put the measurement equipment into practical use. In this paper, we, therefore, propose a phase-shifting device using the deflection of a cantilever and we verify whether this phase-shifting device can be usedfor digital holography.
Authors: Motoharu Fujigaki, Yuji Sasatani, Akihiro Masaya, Hiroyuki Kondo, Makiko Nakabo, Takuya Hara, Yoshiharu Morimoto, Daisuke Asai, Teiji Miyagi, Noboru Kurokawa
Abstract: Sampling Moire method is one of the convenient phase analysis methods. The accuracy of phase difference analysis is from 1/100 to 1/1000 of the grating pitches. This method is useful for a real-time measurement because the phase analysis can be performed from a single-shot image. In this paper, we developed a sampling moire camera which can analyze grating phase in real time. This camera is composed of a CMOS sensor and a FPGA. A two-dimensional grating image taken by the CMOS sensor was analyzed by the FPGA in real time. An application on a real-time deformation measurement of a cantilever is demonstrated.
Authors: T. Kita, Yoshiharu Morimoto, Motoharu Fujigaki, Toru Matui
Abstract: Displacement measurement can be performed with high accuracy using phase-shifting method. In phase-shifting method, it is often used four steps of phase-shifting for one cycle. In conventional method, to measure the displacement of an object by an interferometer, the phase of a reference beam should be shifted by every π/2 in the four-step phase-shifting. In this paper, a phase-shifting method with unknown intervals is proposed. This method does not need to shift a phase by every π/2. It can detect an intensity distribution and a phase distribution from five fringe images with equal intervals even if the phase-shift amount is unknown. Using this method, we propose a displacement measurement of phase-shifting digital holographic interferometry using spherical wave as reference wave.
Authors: Motoharu Fujigaki, Toshio Toyotake, Toru Matui, Yoshiharu Morimoto
Abstract: We previously proposed a real-time shape measurement method using two-component synthesis grating projection. In the method, phase unwrapping of the projected grating is performed by using aliasing of the Fourier spectrum of the grating images. It requires only 5 images obtained for one-cycle phase-shifting. Each phase in the two-component can be extracted from only 5 phase-shifted grating images. In this paper, we propose a real-time shape measurement system. The theory, the algorithm for the analysis and the experimental results are shown.
Authors: S. Okazawa, Motoharu Fujigaki, Yoshiharu Morimoto, Toru Matui
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.
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