Largeshearing electronic speckle pattern interference system with carrierfrequency modulation techniqu

Largeshearing electronic speckle pattern interferometry (LSESPI) offers many advantages such as good fringe quality and no reference beam needed. The fringe pattern obtained by the LSESPI is easy to be observed. The new electronic speckle pattern interferometer is formed by introducing carrierfrequency modulation for interference fields to LSESPI. The new system does not have strict requirement for environment on isolating vibration. The displacement fields could be quantitatively measured with the system. The principle of carrierfrequency modulation of LSESPI is discussed. A typical experiment is implemented with a centralloaded and peripheralclamped plate. And a step motor system controlled by a computer is designed. With the step motor system the reference object can be rotated accurately so that the electronic speckle pattern can be modulated automatically. At last, Fourier transform is used to demodulate the modulated fringes and obtain the phase of deformed field, then acquire the precision deformation of the object by the transformation calculation of the phase and displacement. The experimental results indicate that the interference field of the speckle pattern can be modulated and the displacement of the object can be measured accurately by this system.