• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.329-332
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• 2009

Speckle noise reduction for ultrasound CT image using morphological adaptive median filtering based on edge preservation is presented in this paper. Speckle noise is multiplicative feature and causes ultrasound image to degrade widely from transducer. An input image is classified into edge region and homogeneous region in preprocessing. The speckle is reduced by morphological operation on the 2D gray scale by using convolution and correlation, and edges are preserved. The adaptive median is processed to reduce an impulse noise. As the result the proposed method enhances the image to about 20% in comparison with Winer filter by Edge Preservation Index and PSNR.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.05a
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• pp.156-159
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• 2009

Speckle noise reduction for 3D power doppler ventricle coherent image for restoration and enhancement using wavelet packet transform with separated thresholding is presented. Wavelet Packet Transform divide into low frequency component image to high frequency component image to be multi-resolved. speckle noise is located on high frequency component in multiresolution image mainly. A ventricle image is transformed and inversed with separated threshold function from low to high resolved images for restoration to be utilize visualization for ventricle diagnosis. The experimental result shows that the proposed method has better performance in comparison with the conventional method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.688-694
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• 2002

As a tool for strain measurement to work with screw driven or hydraulic material test systems, in which mechanical vibration is inherent, SSDG(Speckle Strain/Displacement Gage), ESP(Electronic Speckle Photography) and its 3-dimension version SDSP are investigated for the theory and practical appliance. Through tension test of steel strips, their validity and shortcomings are examined. As the results, it has been shown that, although SSDG and ESP provide direct measurement of in-plane strain in one direction, they are so sensitive to the out-plane displacement. On the other hand, SDSP which is aided with DIC (Digital Image Correlation) technique to trace the movement of the speckles provides not only in-plane 2-dimensional displacement field, but also out-of-plane displacement simultaneously. However, because the DIC is time-consuming, not automated yet and it needs post-processing to evaluate strain from the displacement field, SDSP appears to be not adequate as a real time sensor.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.6
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• pp.47-54
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• 2003

As a tool for strain measurement to work with screw driven or hydraulic material test systems, in which mechanical vibration is inherent, SSDG (Speckle Strain/Displacement Gage), ESP (Electronic Speckle Photography) and its 3-dimension version SDSP are evaluated for the theory and practical appliance. Through tension test of steel strips, their validity and shortcomings are examined. As the results, it has been shown that, although SSDG and ESP provide direct measurement of in-plane strain in one direction, they are so sensitive to the out-plane displacement. On the other hand, SDSP which is aided with DIC (Digital Image Correlation) technique to trace the movement of the speckles provides not only in-plane 2-dimensional displacement field, but also out-of-plane displacement simultaneously. However, because the DIC is time-consuming, not automated yet and it needs post-processing to evaluate strain from the displacement field, SDSP appears to be not adequate as a real time sensor.

• Proceedings of the KSRS Conference
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• 2008.10a
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• pp.159-162
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• 2008

This paper presents a modified mean curvature diffusion filter to smooth speckle noise in images. Mean curvature diffusion filter has already shown good results in reducing noise in images while preserving fine details. In the mean curvature diffusion, the rate of smoothing is controlled by the local value of the diffusion coefficient chosen to be a function of the local image gradient magnitude. In this paper, the diffusion coefficient is modified to be controlled adaptively by local image surface slope and heterogeneity. The local surface slope contributes to preserving details (e.g.edges) in image and the local surface heterogeneity helps the smoothing filter consider the amount of noise in both edge and non-edge area. The proposed filter's performance is demonstrated by quantitative experiments using speckle noised aerial image and TerraSAR-X satellite image.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.303-307
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• 2002

Although Synthetic Aperture Radar(SAR) is a very powerful and attractive tool, automatic interpretation of SAR images is extremely difficult because of several reason. Spatially, speckle noise reduction in SAR images is important step to interpret the SAR image at the preprocessing step. The speckle noise in SAR images is modeled to be multiplicative, and therefore, a signal-dependent noise. So, it has deflated many image-denoising algorithms that are based on additive noise model. In this paper, we propose an adaptive wavelet shrinkage method for speckle noise reduction in SAR images by analyzing the high frequency level in detail. We first decompose minutely the high frequency level to analyze the noise level. And then, we determine the weighting threshold value per the level, and layer. Finally, using those weighting threshold, we produce the efficient wavelet shrinkage method. So, this method not only reduces the speckle noise, but also preserves image detail and sharpness.

• Structural Monitoring and Maintenance
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• v.6 no.1
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• pp.67-84
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• 2019

Digital Image Correlation technique (DIC) is a non-contact optical method for rapid structural health monitoring of critical infrastructure. An innovative approach to DIC is presented using QR (Quick Response) code based random speckle pattern. Reinforced Cement Concrete (RCC) beams of size $1800mm{\times}150mm{\times}200mm$ are tested in flexure. DIC is used to extract Moment (M) - Curvature (${\kappa}$) relationships using random speckle patterns and QR code based random speckle patterns. The QR code based random speckle pattern is evaluated for 2D DIC measurements and the QR code speckle pattern performs satisfactorily in comparison with random speckle pattern when considered in the context of serving a dual purpose. Characteristics of QR code based random speckle pattern are quantified and its applicability to DIC is explored. The ultimate moment-curvature values computed from the QR code based random speckled pattern are found to be in good agreement with conventional measurements. QR code encrypts the structural information which enables integration with building information modelling (BIM).

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.574-576
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• 2004

Since variance of noise is important parameter for a noise filter to reduce noise in image and the performance of noise filter is dependent on estimated variance. In this paper, we apply additive noise variance estimation method to estimate variance of speckle noise of synthetic aperture radar (SAR) imagery. Generally, speckle noise is in multiplicative model, logarithmic transformation is then used to transform multiplicative model into additive model. Here, speckle noise is generally modeled as Gamma distribution function with different looks. The additive noise variance estimation is processed in log domain. The synthesis image and real image of SAR are implemented to test and confirm results and show that more accurate estimation can be achieved.

• Proceedings of the KOSOMBE Conference
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• v.1990 no.11
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• pp.5-10
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• 1990

The object detection capabilities of ultrasonic imaging systems are limited by the ability of the detection process to distinguish the resolved object signals from backscattered speckle noise. It has been shown that the phase component of the Fourier transform of the speckle noise is random. Based on this property. we propose a new algorithm for distinguishing between speckle and specular targets. The proposed algorithm is implemented by taking the Fourier transform of the received signal, low-pass filtering the phase, and taking the inverse Fourier transform of the filtered phase to enhance specular reflectors and reduce speckle in the image. Simulations and experiments using phantoms confirm the algorithm yielding significant reduction of speckle noise.

• Proceedings of the KSRS Conference
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• 2008.10a
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• pp.185-187
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• 2008

Speckle noise is primarily due to the phase fluctuations of the electromagnetic return signals. Since inherent spatial-correlation characteristics of speckle in SAR images are not exploited in existing multiplicative models for speckle noise. In this paper, we investigate the efficiency of the filters: Kuan, Gamma, Enhanced Lee, and Enhanced Frost filters in reduction of speckle noise in forestry area. Selection of the suitable filter can be played an important role in applications such as estimation of biomass in forestry areas. We employ ALOSPALSAR image use L-band frequency for this investigation. The filters test on different sites in PALSAR image of the northern forests part of Iran.