2003 年 3 巻 2 号 p. 98-102
In displacement measurement by holographic interferometry, an interferogram is recorded before and after deformation of a specimen using a double exposure method. The fringe pattern obtained from holographic interferometry is the superposition of the complex amplitudes before and after deformation. Then the reconstructed fringe pattern represents contours of out-of-plane displacement. Recently, digital holography was developed. In digital holography, a hologram is recorded on a CCD and the reconstructed image can be obtained from the hologram with a computer. In the case of phase-shifting digital holography, the complex amplitude is obtained from phase-shifted holograms using Fresnel diffraction algorithm. In this study, we propose a method to measure out-of-plane displacement using the phase-shifting digital holography. The displacement distribution of a cantilever is measured by combining holographic interferometry and phase-shifting digital holography. A removal technique of speckle noise is proposed where the speckle noise is suppressed by using the mask made from the reconstructed image.