THE CALCULATION OF THE DENSITY FIELD FROM AXISYMMETRIC SCHLIEREN INTERFEROGRAMS BY THE IMAGE PROCESSING TECHNIQUES

The schlieren interferograms used to be analyzed in a qualitative way. In this paper, by meansof the powerful computational ability and the large memory of computer; the image processing method isinvestigated for the digitalization of an axisymmetric schlieren interferogram and the determination of thedensity field. This method includes the 2-D low-pass filtering, the thinning of interferometric fringes, theextraction of physical information and the numerical integration of the density field. The image processingresults show that the accuracy of the quantitative analysis of the schlieren interferogram can be improved anda lot of time can be saved in dealing with optical experimental results. Therefore, the algorithm used here isuseful and efficient.

SAR Tomography with Improved Non-Local Means Filtering Based on Adaptive Window

In order to mitigate speckle noise in synthetic aperture radar(SAR)images and enhance the accuracy of SAR tomography,non-local means(NL-means)filtering has been proven to be an effective method for improving the quality of SAR interferograms.Apart from considerations like noise type and the definition of similarity,the size and shape of filtering windows are critical factors influencing the efficacy of NL-means filtering,yet there has been limited research on this aspect.This paper introduces an enhanced NL-means filtering method based on adaptive windows,allowing for the automatic adjustment of filtering window size according to the amplitude information of the SAR interferogram.Simultaneously,a directional window is incorporated to align SAR interferograms,achieving the dual objective of preserving filtering standards and retaining detailed information.Experimental results on interferogram filtering and tomography,based on TerraSAR-X data,demonstrate that the proposed method effectively reduces phase noise while maintaining texture accuracy,thereby improving tomography quality.

Three-step self-calibrating generalized phase-shifting interferometry

An accurate and fast three-step self-calibrating generalized phase-shifting interferomertry(SGPSI) is proposed. In this approach, two new phase-shifting signals are constructed by the difference interferograms normalization and noise suppressing, then the unknown phase shift between the two difference phase-shifting signals is estimated quickly through searching the minimum coefficient of variation of the modulation amplitude, a limited number of pixels are selected to participate in the search process to further save time, and finally the phase is reconstructed through the searched phase shift. Through the reconstruction of phase map by the simulation and experiment, and the comparison with several mature algorithms, the good performance of the proposed algorithm is proved, and it eliminates the limitation of requiring more than three phase-shifting interferograms for high-precision SGPSI. We expect this method to be widely used in the future.

INTERFEROGRAM NOISE REDUCTION ALGORITHM BASE ON MAXIMUM A POSTERIORI ESTIMATE

Interferogram noise reduction is a very important processing step in Interferometric Synthetic Aperture Radar(InSAR) technique. The most difficulty for this step is to remove the noises and preserve the fringes simultaneously. To solve the dilemma, a new interferogram noise reduction algorithm based on the Maximum A Posteriori(MAP) estimate is introduced in this paper. The algorithm is solved under the Total Generalized Variation(TGV) minimization assumption, which exploits the phase characteristics up to the second order differentiation. The ideal noise-free phase consisting of piecewise smooth areas is involved in this assumption, which is coincident with the natural terrain. In order to overcome the phase wraparound effect, complex plane filter is utilized in this algorithm. The simulation and real data experiments show the algorithm can reduce the noises effectively and meanwhile preserve the interferogram fringes very well.

Robust PolInSAR optimal interferogram estimation method based on generalized scattering vector

For the polarimetric synthetic aperture radar interferometry(PolInSAR) processing, it is necessary to coregister all the images, including the coregistration of polarimetric SAR images and the coregistration of interferometric SAR images. Otherwise,the performance of the estimated optimal interferograms will be deteriorated. A generalized scattering vector(GSV) model is proposed to execute the PolInSAR optimal interferograms estimation.The generalized scattering vector is constructed by the Pauli scattering vectors of the processing pixel and the surrounding pixels.Even though there are coregistration errors, all the polarimetric information of the current processing pixel is entirely included in the generalized scattering vector. Therefore, the GSV-based method can automatically recover the optimal scattering mechanisms of the processing pixel with coregistration errors either in interferoemetric channels or polarimetric channels. Theoretical analysis and processing results of simulated Pol SARPro data and real PALSAR data validate the effectiveness and correctness of the proposed method.

A NEW ALGORITHM FOR SCANSAR PROCESSING

In this paper, a new phase preserving algorithm-the short IFFT algorithm for the burst-mode ScanSAR processing is presented. Analysis and simulation are done to verify the phase accuracy of this algorithm. Finally, the phase accuracy of this algorithm by making interferogram with simulated burst-mode INSAR data is illustrated. The results show that this new algorithm works well for interferometric application of ScanSAR data.

InSAR Observation for the Surface Displacements at Mt. Etna between 2003 and 2007

This research is mainly devoted to InSAR observations using Poly-Interferogram Rate and Time-series Estimator (π-rate) software to investigate continuous surface displacement at Mt. Etna (Sicily), Italy between 2003 and 2007. Using ascending and descending SAR images produced by European Space Agency’s ENVISAT, we generate a set of interferograms which are used to determine?the deformation history of Etna from 2003 to 2007. Using (π-rate), we can generate the InSAR?time-series and ratemap while minimizing errors induced by the satellites orbit and atmospheric?phase delays. During the period of 2003-2007, three separate eruptions were observed. In order to explain the deformation, we solve three displacement rate for 2003-2005, 2006 and 2007. As expected, the result suggests that displacement rates are not constant with respect to time. During 2006 the volcano appeared to switch from a period of deflation to a period of inflation. These results highlight the importance of InSAR for generating deformation time-series around Mt.?Etna, and with the application of numerical models these results can be used to estimate the?amount of magma moving in the subsurface.

Thermal Stress Monitoring on Piston Rings by Real Time Holographic Interferometry

In this paper, real time holographic Interferometry (RTHI) technique was used to monitor the thermal stress on the piston rings. The piston rings holograms were recorded and the holographic plate replaced on the holder after development. The piston ring was subjected to thermal stress as it was illuminated by Laser beam acting as the object beam. This process led to generation of interferograms which were captured by a CCD camera at different temperatures. The captured interferograms were analyzed using atmosfringe version 3.3 software. From the analysis, the peak to valley (P-V) aberrations measured for each of the piston ring varied for the same temperature value. The P-V aberrations ranging from 0.0128λ to 1.2989λ were obtained. From this result, it was evident that the three rings on the piston had different unique structural characteristics due to their function.

Vortex Field Propagation in a Hexagonal Multicore Fiber Array

The propagation of an optical vortex in a hexagonally arranged single mode multicore fiber structure is investigated for possible generation of additional vortices and their spread dynamics. Fields are separated into a slowly varying paraxial envelope and a rapidly changing exponential component. Solutions are derived from the paraxial inhomogeneous Schrodinger equation in two dimensions along with the index of refraction of the proposed structure. Numerical analyses are based on the beam propagation method and transparent boundary conditions in matrix form with different parameters to represent the intensity and phase of all derived fields. Vortices are numerically identified by their points of zero intensity and their phase change or polarity. The optical interferogram with a plane wave reference is also employed to distinguish the dislocation points in the transverse directions of the propagating fields.

Observation of the Metallic Vaporfrom a Plasma Focus

Although many scientists suggested that the ionized metallic vapor produced in plasma focus plays asignificantrole in the X ray emission,they did not give a visualimage ofthe metallic vapor.In this paper the evolution of plasma sheath above the anode was recorded with a laser differentialinterferometer and the metallic vapor produced onthetargetsurface by bombardmentofanintense electron beam was observedforthe firsttime. The results can help understanding ofthe physicalprocess ofthe X ray emissionfrom plasma focus.