Papers by Keyword: Interferogram

Abstract: The kinetic dependence of the photorefractive effect in the congruent lithium niobate crystal is determined in the work. The adequacy of the model for calculating the photoelectric fields from the indicatrix of photoinduced light scattering is shown. Two methods for determining the induced birefringence by interferograms and on the parameters of photoinduced light scattering are compared.

Abstract: According to the characteristics of interferogram, we design a new spike detection method, which firstly filters an interferogram with two different ways and then detects spikes based on both results. Theoretical analysis and computer simulation shows that this algorithm performs well in detecting spikes in any position of an interferogram with high accuracy, and can be easily implemented in hardware.

Abstract: Interferogram noise filter is one of the key technologies which use synthetic aperture radar interferometry phase to extract digital elevation model. However, the interference fringes’ details are often reduced when complex interferogram is filtered, and this leads to inaccurate phase unwrapping result, for this combined filter method based on terrain factors is proposed. Filter method can be selected through weight factor associated with the terrain slope in the filter process, and Wiener filter method is implemented in flat terrain area, frequency estimated filter method is achieved in steep terrain area. Then the new filter method is applied to deal with data where the region of Quebec, Canada. This proves that the new filter algorithm proposed in this paper can effectively suppress noise and better maintain stripe details.

Abstract: Interferogram is the original measured signal of the Fourier transform spectrometer. A new method addressed the problem of noise reduction in inter-ferogram domain is proposed for multivariate calibration of Fourier transform near infrared spectral signals. The method is based on the discrete wavelet transform (DWT). It is used to determination of the ethanol as noise reduction tool for partial least square (PLS) modeling. It is shown that the benefit of the proposed method lies not only in its performance to improve the quality of PLS model and the prediction precision, but also in its simplicity and practicability.

Abstract: The equation for the recovered spectrum is derived in spatially modulated interferometric imagers, which takes into account the pixel photosensor width. The results show that the effect of the pixel photosensor width on the recovered spectral intensity is related to the wavenumber and the intensity of the incident spectrum, which causes the broadband spectral waveform changed, and the distortion increases with the spectral bandwidth increasing. A mathematical algorithm is given to correct the distortion, and the experimental results show this method is effective.

Abstract: In this paper, a coupled nonlinear diffusion partial differential equations (PDE) method for Interferometric Synthetic Aperture Sonar(InSAS) interferogram filtering was introduced. Many previous PDE methods in this area usually use Gauss pre-filtering. The choice of variance in Gauss function plays a very important role in the quality of the image obtained. Manually choice of the variance can hardly reach the self-adaptation aim. Using nonlinear diffusion equation to instead Gauss pre-filtering can overcome the disadvantage mentioned above. Numerical experiment results indicate that this coupled PDE method is able to effectively reduce the noise and preserve edge information. And it is important for InSAS real time processing.

Abstract: Interferogram processing is one of main techniques in optical interferometry metrology. Modern interferometry for thin-film thickness has the advantages of noncontact and high accuracy, etc. Interferogram processing is important Step of interferometry. This article is the sum-up about the key technology of interferogram processing in interferometry, it reduce key technology of interferogram processing to three steps: removing the noise, edge detection, region spreading and phase unwrapping. Interferogram processing can be realized by using software developed by the key technologies. Then getting surface of the measured material object, thus the measured material object is measured automatically. In this paper, the thin-film thickness is determined by the key technologies, setting the results of this method against results from ZYGO, the PV error and RMS maximum error are 0.0364λ and 0.002λ respectively. Although single interferogram was processed in this study, a phase distribution with high accuracy was achieved.

Abstract: Interferometric Synthetic Aperture Radar is a kind of technology to acquire the DEM information on the surface of the earth. It is concerned and researched by all over the world. Complex image registration of high precision is the key step in InSAR data processing, its results directly influence on the quantity of interferometric phase , even to the DEM precision.This paper introduces the complex image registration plans which is used the correlative coefficient method to make the coarse registration, and is used the correlative coefficient interpolation method to make the high precise registration.The experiments with spaceborne and aeroplane InSAR data prove that this method is with feasibility, high efficiency and practicability.

Abstract: In this paper, we present a video-based interferogram analysis method for measuring the influence of vibration on white light interferometer in terms of undesired change in optical path difference between reference and sample arms. The measurement principle is based on the analysis of interferograms which involves tracking and converting change in interferograms to physical change in optical path difference. The method proposed uses the original sensor in interferometer for data acquisition as such no additional hardware is required. Such an approach ensures that the properties of interferometer such as the bandwidth of sensor are considered and the vibration pattern recorded is close to the effective influence of vibration. With our method, the influence of vibration on white light interferometer and the performance of vibration isolation system can be objectively quantified and measured.

Abstract: Interferometry is a meterage technology which is based on light-wave interference theory. In the general interferometry measurements, the procedure of analyzing and studying interferogram depends on a processing system mostly based on PC. In this paper an image processing system based on DSP is conceived, and the entire system consists of a image collecting module, a digital data exchanging interface and a image processing module. A typical interferogram collected from experiments is processed by the system conceived above. Comparing the processed stripe with the ideal pattern, we found that the system is competent for interferometry.