The Construction Of A Class Of Oriented Anisotropy Filter Masks And Theirs Application

Rising gradually from the late sixties of the last century, electronic speckle pattern interferometry (ESPI) testing technology is a modern optical testing technology and a comprehensive modern high-tech achievement which includes the computer image processing technology, the laser holographic interferometry and the electronic technology. It is widely used in the object deformation measurement such as vibration, displacement and strain and the nondestructive testing, because by the ESPI testing technology not only can we study rough surface itself, but also of its shape and position changes. However, the ESPI fringe patterns and phase patterns got from the experiments always have strong noises which seriously affect the ESPI phase extraction. Therefore, how to remove the noise and get the high-quality ESPI fringe patterns and phase pattern is the key factor to the technological development.Directivity is a very important feature of the ESPI fringe patterns and phase patterns, and plays a very important role in guiding the filtering process. In particular, when the fringe density change is very large, it is more necessary to consider the direction of the ESPI fringe patterns and phase patterns. My paper's main work contains: (1) introduces the filtering theories and methods of three typical oriented filtering models, which are the second-order oriented partial-differential equations filtering only along the tangent direction, the regularized quadratic cost function for oriented fringe-pattern filtering and the coherence enhancing diffusion filtering both along the tangent and the normal direction, then analyzes and compares their respective advantages and disadvantages and also simplifies to improve the coherence enhancing diffusion model. (2) Based on the theory of the image sharpening and referred to the Laplacian operator, we have built a class of oriented spatial filter masks and introduced their derivation in details. In order to obtain the same better filtering effect of the thin ESPI patterns and thick ESPI patterns, we also make an improvement on the oriented spatial filter mask for enhancing the smoothness. (3) The improved oriented spatial filter masks are used to the filtering process of the ESPI fringe patterns and ESPI phase patterns and compared with other directional partial differential equation filter models.The main advantages of our oriented spatial filter masks derived in this paper contain:Simple, intuitive, practical and have a very high applied value; filtering results are satisfactory; the high image contrast after filtering and the fringe edge can be well maintained while filtering. The performance of our oriented spatial filter masks is demonstrated via experimental results and the comparison with other directional partial differential equation filter models.