Contrast of the vibration fringes in time-averaged electronic speckle-pattern interferometry: effect of speckle averaging.

This paper presents a detailed investigation of the effect of speckle averaging in electronic speckle-pattern interferometric fringes. The theory states that the constrast of the resultant smoothed fringes increases as the number of frames is increased. It is shown that the contrast of the fringes is optimized with a limited number of superpositions, and further addition results in the reduction of speckle noise with the contrast remaining almost the same. The contrast of the fringes obtained with pi and pi/2 phase-stepping methods with speckle averaging is also discussed. Both theoretical and experimental results are presented in this paper.