Results 221 to 230 of about 143,665 (236)

Speckle noise reduction for ultrasonic images

SMC'03 Conference Proceedings. 2003 IEEE International Conference on Systems, Man and Cybernetics. Conference Theme - System Security and Assurance (Cat. No.03CH37483), 2004
This paper presents a method to enhance ultrasonic images that are commonly plagued with a special type of acoustic noise called speckles. To reduce the noise effect, filters such as the weighted median filter, adaptive trimmed mean filter, two dimensional weighted Savitzky-Golay filter (2D-WSGF) have been studied.
Chung-Chang Wu, Chun-Jun Huang, Jung-Hua Wang   +2 more
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Speckle noise reduction in SAS imagery

Signal Processing, 2007
Synthetic aperture sonar (SAS) is actively used in sea bed imagery. Indeed high resolution images provided by SAS are of great interest, especially for the detection, localization and eventually classification of objects lying on sea bed. SAS images are highly corrupted by a granular multiplicative noise, called speckle noise which reduces spatial and ...
Fabien Chaillan, Philippe Courmontagne, Christophe Fraschini   +2 more
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Non-Gaussian statistics of speckle noise of Young's fringes in speckle velocimetry

Applied Optics, 1985
In speckle velocimetry, Young's fringes observed during analysis of the multiple-exposure photographs of tracer particles seeding a fluid flow are embedded in a speckle noise that renders their analysis difficult. Some first- and second-order statistical properties of this speckle background are considered in this paper.
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Laser vibrometer speckle-noise cancellation

Measurement Science and Technology, 1993
When a rotating scattering disc is used to frequency-shift the reference beam of a laser vibrometer, the noise floor is determined by speckle noise. The speckle noise is cancelled by recording it in the absence of target vibration and then subtracting the recorded signal Vr from that obtained when measuring the vibration. Vr is the average for 256 disc
T H Wilmshurst, N A Halliwell
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Speckle Noise Reduction by Random Phase Shifters

Japanese Journal of Applied Physics, 1974
Experimental results are given that show that a random phase shifter (RPS) is effective in reducing speckle noise caused by optical defects in coherent imaging systems, including holographic imaging systems. Here the RPS is composed of many tiny transparent blocks, each of which gives a definite phase shift such as O or pi to the transmitting light ...
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Detection of Images Immersed in Speckle Noise

Optica Acta: International Journal of Optics, 1971
Simple statistical detection theory is applied to the problem of detecting small images immersed in a background of laser-produced speckle. The detection device is assumed to be a flying-spot type of scanning machine which has continuous scanning in both the x and y directions. Two main points have emerged.
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Edge detection in ultrasound speckle noise

Proceedings of 1st International Conference on Image Processing, 2002
Presents a statistical approach to edge detection in ultrasound speckle, and uses actual noise statistics to derive an expression for an optimal detection rule. The authors compute the optimal detector for the special case of uncorrelated speckle, and an approximation to the optimal detector for the case when signal-to-noise ratio (SNR) is high.
R.N. Czerwinski, William D. O'Brien, Douglas L. Jones   +2 more
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Evaluation of noise in measurements with speckle shearography

Mechanical Systems and Signal Processing, 2019
Abstract Speckle shearography has the advantage of allowing non-contact, full-field and high resolution measurements. Nevertheless, due to its nature and to its sensitivity to ambient perturbations, the measurements may present high levels of noise.
H. Lopes, P. Moreno-García, J.V. Araújo dos Santos   +2 more
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Speckle noise in highly corrected coronagraphs

SPIE Proceedings, 2004
Speckles in a highly corrected adaptive optic imaging system have been studied through numerical simulations and through analytic and algebraic investigations of the Fourier-optical expressions connecting pupil plane and focal plane, which simplify at high Strehl ratio.
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Speckle noise removal by robust modeling

Proceedings 2003 International Conference on Image Processing (Cat. No.03CH37429), 2004
A robust modeling approach is applied to remove speckle noise in synthetic aperture images. Conventional adaptive filtering approaches in speckle filtering smoothes the image selectively depending on the details of underlying textures, and tend to blur details after speckle removal.
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