Digital speckle displacement measurement by fuzzy logic correlation

摘要

Fuzzy set has an advantage over classic set for representation of objects with a high degree of vagueness, inaccurate, or uncertainty. Fuzzy set theory could be seen as a generalization of classic set theory. In this paper, a digital speckle correlation method based on fuzzy logic (DSCMF) is proposed to measure the displacement of laser speckles. DSCMF is developed to improve performances of the digital speckle correlation method based on classic logic (DSCMC), at the same time keeping low computation simplicity. Fuzzy correlation between two images could be defined as an integral of membership of similarity between elements of two images. Membership function of similarity is defined to represent the distance of two values. An optical and analysis system was set up to verify DSCMF's validity. A parameter δ_(SN) is introduced to represent the ratio of signal to noise. Experimental results show that DSCMF using triangle tent similarity membership function could obtain a bigger δ_(SN) than DSCMC could. This paper also shows the influence on δ_(SN) of quantification of membership function.