Deformation measurement of diffuse objects by using two laser beams of different wavelengths

摘要

In deformation changes including step-like discontinuities, techniques using a laser beam of single wavelength cannot measure the deformation amounts. Because the deformation changes between successively captured specklegrams would be larger than the wavelength of the laser. We have developed the technique that can measure large deformation changes including step-like discontinuities by using two laser beams of different wavelengths. In an optical system, optical fibers are used to ensure the same optical-path differences between the different wavelengths. Phase changes are evaluated in both the wavelengths through all the successively captured specklegrams. From the difference of phase changes between both the wavelengths, large deformation changes can be estimated, but precise deformation changes could not be estimated. Then, phase changes of one of two wavelengths is also utilized to estimate precise and large deformation changes.