Akihiro Masaya

Shape Measurement by Phase-Stepping Method Using Multi-Line LEDs

Three-dimensional shape measurement is used in various fields such as robotics and inspection of industry production. It is requested to measure shape with high speed and high accuracy. It is also requested to make the system compact and low-cost. It is, however, difficult to satisfy these requests simultaneously for 3D shape measurement. In order to measure shape in real-time, Kato et al. proposed a method using phase-shifting electronic moire pattern (Kato et al., 1997). The authors developed integrated phase-shifting method for real-time shape measurement by a grating projection method using phase-shifting (Morimoto et al., 1999, Fujigaki & Morimoto, 2003). However, they showed only the phase distribution of the contour lines.

Development of dynamic shape and strain measurement system by sampling moiré method

Shape measurement and strain distribution measurement are important to analyze the behavior of a moving object. In this paper, a dynamic shape and strain measurement system by the sampling moire method is developed. Recently, phase analysis method using phase-shifting moire patterns generated in a computer from a grating image is proposed. This method is very suitable for dynamic measurement because the phase can be obtained from a one-dimensional or two-dimensional (2-D) grating image with high accuracy. It is possible to analyze strain distribution and shape measurement of a moving object using a grating pattern attached on the specimen surface. A dynamic shape and strain measurement system by the sampling moire method is developed. The principle and experimental results applied to a rotating object are shown.

Dynamic shape and strain measurements of rotating tire using a sampling moiré method

Shape measurements and strain distribution measurements are important for analyzing the behavior of a rotating tire. Recently, a two-dimensional phase analysis method using phase-shifting moire patterns, which are generated computationally from a two-dimensional grating image, was proposed. This method is well suited to the dynamic shape and strain measurement because the phase can be accurately obtained from a two-dimensional grating image. We show that it is possible to analyze the strain distribution and shape measurements of a moving object using a grating pattern attached to the surface of the specimen, and a dynamic shape and strain measurement system using the sampling moire method is developed in this paper. The principle of the method and the experimental results of the method when applied to a rotating object are shown.

Shape Measurement by Whole‐space Tabulation Method Using Phase‐shifting LED Projector

In order to obtain a 3D‐shape with grating projection method, the authors previously presented whole‐space tabulation method (WSTM). The relationship between the coordinates and the phase of the grating recorded at each pixel of a camera is obtained as calibration tables in three‐dimensional space by experiment beforehand. Therefore the analysis is very fast because of looking at the calibration tables without any complex calculation. It provides fine resolution even when the phase distribution of the grating is not linear. In this paper, a grating projector with three light emitted diode (LED) light sources is proposed. It provides a low cost system. The theory and experimental results are shown.

Development of Sampling Moire Camera for Real-Time Phase Analysis

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.

Shape measurement by grating projection and whole-space tabulation method

The authors previously proposed a shape measurement method using pixel-by-pixel calibration tables produced with multiple reference planes. In this method, all the relationships between the phase of the projected grating and the spatial coordinates can be obtained for each pixel. This method is called ‘whole-space tabulation method’. This method excludes a lens distortion and intensity errors of the projected grating in measurement results theoretically. Tabulation makes a high-speed and accurate shape measurement possible. The principle of the shape measurement using the whole-space tabulation method and some results of shape measurements using this method are shown.

Accurate Displacement Measurement for Landslide Prediction by Sampling Moiré Method

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.

Shape measurement by light-stepping method using LEDs

A new shape measurement method using whole-space tabulation method and light-stepping method is proposed. A grating projector using five LED line light sources is also proposed for the light-stepping method. It will be a very fast, low-cost and accurate measurement system. The theory and experiment are introduced.

Prediction of Landslide by Displacement Measurement using Sampling Moiré Method

In sampling moire method, a specimen grating pattern on an object is recorded by a digital camera. A moire fringe pattern appears by sampling the recorded grating pattern with a constant pixel pitch. The phase analysis of the moire patterns obtained from one grating pattern provides accurate results of displacement values of the grating. Meanwhile, it is very important to keep our life safely by predicting landslides. If the small displacement of land before the landslide is detected, it is possible to put out an alert before the disaster happens. In this paper, a measurement system for small displacement of landslide by sampling moire method is developed.

Real‐Time Shape Measurement by Grating Projection Method Applied to Electronic Packaging

In this study, a system using a Field Programmable Gate Array (FPGA) memory board is proposed to obtain the full‐size shape without any reduction of the image in real‐time. The memory of the FPGA memory board has a phase analysis table and phase‐coordinate tables. The brightness data of the recorded grating are stored in the phase analysis table to obtain the phase of the recorded grating. The calibration data using a moving reference plane are stored as a phase‐coordinate table to obtain the coordinates of the phase. An experiment to evaluate this system was performed. The analysis speed of shape measurement using the memory board did not depend on a speed of a personal computer. The accuracy of shape measurement using the memory board and using software was almost the same. The analysis speed using the memory board was faster than the one using software.