94 S. Arikawa and Y. Ando Fig. 15.1 Schematic figure of line laser scanning speckle interferometry Fig. 15.2 Line phase integration 15.3 Experiment A dual-beam interferometer for a horizontal displacement measurement which can illuminate horizontal line lasers and can scanning for vertical direction is constructed on an experimental stage. The laser power is 53 mW and the wavelength is 633 nm. The beam diameter for vertical axis is 1.42 mm. The width of the interference region expanded by the cylindrical lenses is about 50 mm. A monochrome CCD camera is used for measurement. A measurement of a static horizontal tensile deformation of an aluminum sheet specimen is carried out. The camera is fixed on the experimental stage while the measurement with laser scanning. 15.4 Results and Discussion Line shaped interferograms showing the tensile deformation were obtained. Hence the accurate laser scanning could be performed. Analyzed phase maps for each line showed the mismatch of the phases. The phase correction was performed. The corrected phases were then integrated as a single phase map. The integrated phase map showed a continuous phase distribution. Therefore the phase correction was effective. However, slight phase mismatches observed on the integrated phase map with phase correction when the scanning steps increased. It is expected that the deformation slightly occurs while the measurement. The proposed method can only be used for static deformation measurement. However, a comparatively long time was taken for the line laser scanning and the phase shift for the phase analysis because of the hand movement at this stage. Therefore, the deformation increased during the measurement. For minimizing the deformation during the measurement, speeding up the measurement process by an automation is required. 15.5 Conclusion In this study, ESPI with line laser scanning was investigated for large area deformation measurements without increasing the laser power. A dual-beam interferometer for a horizontal displacement measurement which can illuminate horizontal line lasers and can scanning for vertical direction was constructed. A static in-plane deformation of an aluminum sheet
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