Research Of Digital Speckle Pattern Interferometry Fringe Information Process

The Digital Speckle Pattern Interferometry is a full-field non-contact opticalmeasurement technology, which is being used widely by these industries for themeasurement ofdeformation, stress, and displacement of components and structures.In optical measurement, optical phase is very sensitive to the change ofdisplacement and wavelength，that is benefit for the measurement of physicalquantities of deformation, displacement. So it is important for DSPI to extractphase information from the speckle pattern, and analyses and process the phaseinformation.The key of DSPI fringe information process is to extract phase from the lightintensity images through a series of analysis and processing. Because of thefeatures of the speckle pattern images, such as fringe distribution of phase, aliasingbetween phase information and noises, it has to use some specific methods for theprocess of DSPI fringe information.This thesis analysed the fundamental of DSPI, summarized the characteristicsof speckle interference image, studied a variety of image processing algorithms,then design and implement a DSPI image processing system, which can get the realphase values at optional position in the interference field. The primary coverage ofthis paper is as follows:(1) Using phase-shifting or spatial carrier could measure the phase distribution atthe whole field. We introduced the fundamental of these methods, andanalysed the characteristics of phase maps.(2) We studied filtering algorithms for phase images in space domain andfrequency domain respectively, than a frequency domain low-pass filteringmethod based on sine and cosine transform were presented. We implementedthe two methods using computer programming, got improved filter effect inthe experiment.(3) Studied the current phase unwrapping algorithm, an algorithm of pointwiseunwrapping from the inside to the outside was presented. We implemented themethod using computer programming and got the real phase distribution morequickly and accurately in the experiment.(4) A set of DSPI image processing software was prepared based on Visual C++ 6.0, which implemented a series of speckle image processing includes phasecalculation, smoothing, phase unwrapping, deformation information extraction,3-D display.