• Journal of the Korean Society for Precision Engineering
• /
• v.32 no.9
• /
• pp.807-813
• /
• 2015

In the present study, an interferometer system, which integrates the laser sensitivity control technique based on the theory of electronic speckle pattern interferometry, one of non-contact non-destructive analysis methods, was developed. This interferometry system receives an image from CCD cameras for each reference and object, and compares the photosensitivity of the object and reference images from imagification. For the purpose of this study, the photosensitivity of object and reference light is measured with power meters, and the amount of light was controlled with an ND filter with a reference light port matching photosensitivity. Using the plate specimen as the object, 0.6, 0.9, 1.2, and $1.5{\mu}m$ of out-plane deformation was made, and images were compared according to the difference in photosensitivity. After analysis, larger object deformations showed larger numbers of stripe patterns. Images became clearer and data error was reduced when the photosensitivity of object and reference light matched.

• The Journal of the Acoustical Society of Korea
• /
• v.15 no.5
• /
• pp.21-29
• /
• 1996

Industrial equipment, such as power plant, is required to operate reliably, continuously and economically under rather severe conditions of temperature, stress, and enbironment. To test structural integrity and fitness, ultrasonic nondestructive testing is used because of effectiveness and simplicity. In this paper, wavelet transform based least mean square(LMS) algorithm is applied to reduce the influence of the interference occurring between randomly positioned small scatters. The RUN test is performed to check the nonstationarity of the speckle noise signal. The performance of this new approach is compared with that of the time domain LMS algorithm by means of condition numbers, signal-to-noise ratio and 3-D image. As a result, the wavelet transform based LMS algorithm shows better performance than the time domain LMS algorithm in this experiment.

• Journal of Digital Contents Society
• /
• v.15 no.6
• /
• pp.675-682
• /
• 2014

Prostate is only an organ of men. To diagnose the disease of the prostate, generally transrectal ultrasound(TRUS) images are used. Detecting its boundary is a challenging and difficult task due to weak prostate boundaries, speckle noise and the short range of gray levels. In this paper a method for automatic prostate segmentation in TRUS images using Support Vector Machine(SVM) is presented. This method involves preprocessing, extracting Gabor feature, training, and prostate segmentation. The speckle reduction for preprocessing step has been achieved by using stick filter and top-hat transform has been implemented for smoothing. Gabor filter bank for extraction of rotation-invariant texture features has been implemented. SVM for training step has been used to get each feature of prostate and nonprostate. Finally, the boundary of prostate is extracted. A number of experiments are conducted to validate this method and results shows that the proposed algorithm extracted the prostate boundary with less than 10% relative to boundary provided manually by doctors.

• The Journal of the Korea Contents Association
• /
• v.8 no.11
• /
• pp.1-9
• /
• 2008

Thanks to the multimedia technology development, it is possible to show image representations in high quality and to process images in various ways. Anisotropic diffusion as an effective diffusion filtering among many image preprocessing methods and postprocessing methods is used in reduction of speckle noises of ultrasound images, image restoration, edge detection, and image segmentation. However, the conventional anisotropic diffusion based on a cross-kernel causes the following problems. The problem is the concentration of edges in the vertical or horizontal directions. In this paper, a new anisotropic diffusion transform based on directions of gradient is proposed. The proposed method uses the eight directional square-kernel which is an expanded form of the cross-kernel. The proposed method is to select directions of small gradient based on square-kernel. Therefore, the range of proposed diffusion is selected adaptively according to the number of the directions of gradient. Experimental results show that the proposed method can decrease the concentration of edges in the vertical or horizontal directions, remove impulse noise. The image in high quality can be obtained as a result of the proposed method.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.30 no.4 s.247
• /
• pp.287-297
• /
• 2006

The Holographic Particle Velocimetry system can be a promising optical tool for the measurements of three dimensional particle velocities. One of inherent limitations of particle holography is the very long depth of field of particle images, which causes considerable difficulty in the determination of particle positions in the optical axis. In this study, we introduced three auto-focusing parameters corresponding to the size of particles, namely, Correlation Coefficient, Sharpness Index, and Depth Intensity to determine the focal plane of a particle along the optical axis. To investigate the suitability of the above parameters, the plane image of dot array screens containing different size of dots was recorded by diffused illumination holography and the positions of each dot in the optical axis were evaluated. In addition, the effect of particle position from the holographic film was examined by changing the distance of the screen from the holographic film. All measurement results verified that the evaluated positions using suggested auto-focusing parameters remain within acceptable range of errors. These research results may provide fundamental information for the development of the holographic velocimetry system based on the automatic image processing.

• Korean Journal of Remote Sensing
• /
• v.32 no.5
• /
• pp.539-550
• /
• 2016

Detection of water bodies in land surface is an essential part of disaster monitoring, such as flood, storm surge, and tsunami, and plays an important role in analyzing spatial and temporal variation of water cycle. In this study, a quantitative comparison of different thresholding-based methods for water body detection and their applicability to Kompsat-5 SAR data were presented. In addition, the effect of speckle filtering on the detection result was analyzed. Furthermore, the variations of threshold values by the proportion of the water body area in the whole image were quantitatively evaluated. In order to improve the binary classification performance, a new water body detection algorithm based on the bimodality test and the majority filtering is presented.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.34 no.1
• /
• pp.43-52
• /
• 2016

Due to the characteristics of microwave signals, Radar satellite image has been used for flood detection without weather and time influence. The more methods of flood detection were developed, the more detection rate of flood area has been increased. Since flood causes a lot of damages, flooded area should be distinguished from non flooded area. Also, the detection of flood area should be accurate. Therefore, not only image resolution but also the filtering process is critical to minimize resolution degradation. Although a resolution of radar images become better as technology develops, there were a limited focused on a highly suitable filtering methods for flood detection. Thus, the purpose of this study is to find out the most appropriate filtering method for flood detection by comparing three filtering methods: Lee filter, Frost filter and NL-means filter. Therefore, to compare the filters to detect floods, each filters are applied to the radar image. Comparison was drawn among filtered images. Then, the flood map, results of filtered images are compared in that order. As a result, Frost and NL-means filter are more effective in removing the speckle noise compared to Lee filter. In case of Frost filter, resolution degradation occurred severly during removal of the noise. In case of NL-means filter, shadow effect which could be one of the main reasons that causes false detection were not eliminated comparing to other filters. Nevertheless, result of NL-means filter shows the best detection rate because the number of shadow pixels is relatively low in entire image. Kappa coefficient is scored 0.81 for NL-means filtered image and 0.55, 0.64 and 0.74 follows for non filtered image, Lee filtered image and Frost filtered image respectively. Also, in the process of NL-means filter, speckle noise could be removed without resolution degradation. Accordingly, flooded area could be distinguished effectively from other area in NL-means filtered image.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.05a
• /
• pp.330-333
• /
• 2002

This study Presents improvement of Precision in the non-contacted laser application measuring techniques. The phase map of deformation obtained by phase shifting method in Electronic Speckle Pattern Interferometry displays the wrapped image by the arctangent function, which is a characteristic of 4-step phase shifting method. To obtain deformation distribution from the results, the wrapped phase map is processed by an unwrapping method. But a previous method cannot apply discontinuous object as like plate with a circular hole to obtain precious deformation distribution To solve this problem, new algorithm is developed and the result is compared with previous method.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2000.11a
• /
• pp.93-96
• /
• 2000

This study discusses a non-contact optical technique, phase shifting electronic speckle pattern interferometry, that is well suited for a deformation measurement. However, the phase shifting method has difficulties for determinating a deformation quantitatively beacuse of the characteristics of arctan function. In order to solve this problem, phase unwrapping methods has been studied during the last few years. In this study, using phase unwrapping based on line by line scanning phase shifted fringe patterns are studied to determinate a deformation quantitatively. Also least square fitting method is applied to reduce noise and improve image resolution.

• Journal of Ocean Engineering and Technology
• /
• v.16 no.4
• /
• pp.13-18
• /
• 2002

The magnitude of the plastic zone around the crack tip of DENT(Double Edge Notched Tension) specimen and the crack growth length under cyclic loading were measured by ESPI(Electronic Speckle Pattern Interferometry) system. The measured magnitude of plastic zone was compared with the equations proposed by Irwin and calculated by a nonlinear static method of MSC/NASTRAN. The measured crack growth length by ESPI system was also compared with the obtained data by the image analysis system. From the study, it is confirmed that the plastic zone and crack growth length can be measured accurately with the high-tech equipment.