Application Of ESPI In Industry Quality Inspection

Electronic speckle pattern interferometry (ESPI) technology is widely used in micro-deformation detection and non-destructive testing as a high-precision optical measurement technology and it has the feathers of high accuracy, non-contact, high detection speed and etc.The phase information contained in pattern images has relationships with the deformation of object. Now the fringe-centerline method and the phase-shifting technology are two of the most comprehensive phase extraction techniques. But lots of granulation noises and the low contrast of pattern images make it difficult to extract the accurately information of the phase. We can't extract the precise phase information by using the fringe-centerline method in this article, so the phase-shifting device is introduced to the electronic speckle pattern interferometry system to pick up the phase information contained in the images. The phase-shifting technology, the device of phase-shifting, the generation modes for phase map, filter method for wrapped phase map and the phase unwrapped technique are presented and studied in this article.The hardware consisted of the system is so important and selecting appropriate optical components is also necessary in order to improve measurement accuracy. The shear has a big impact on measurement accuracy, measurement sensitivity and the fringe contrast. Research of shear is done and the method for selecting shear is proposed through the combination of theoretical analysis and simulation images. Bubbles defect of tire is detected and the micro-deformation of steel plate is measured by using the ESPI test system.The major innovations achieved in the dissertation are as follows:[1] Deriving the relationship between the out-place displacement derivative and phase contained in the image obtained by the electronic shearography speckle pattern interferometry test system, computing the parameters of each part and selecting the appropriate components to build the system.[2] Using MATLAB to simulate the electronic shearography speckle pattern under different shears and generate a lot of valid images. The method for selecting shear is proposed through the combination of theoretical analysis and simulation images.[3] Proposing appropriate algorithms of filter method for wrapped phase map and the phase unwrapped technique by using phase-shifting technology.[4] Using the electronic shearography speckle pattern interferometry test system to detect the bubbles defect and deformation of tire at different loading ways, and measure the micro-deformation of steel plate.