• 제목, 요약, 키워드: Noise Filter

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디지털 의료영상에서 Noise감소를 위한 필터조합과 임상적 효과에 관한 연구 (Research About Filter Association and Clinical Effect Noise Reduction of Digital Medical Imaging System)

  • 민정환;김정민;정회원;옥치일
    • 대한방사선기술학회지:방사선기술과학
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    • v.30 no.4
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    • pp.329-334
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    • 2007
  • 의료영상에서 화질저하를 최소화 하면서 Noise를 감소시키기 위하여 Noise가 첨가되어 있는 영상을 대상으로 Low Pass Filter(LPF) 5종, High Pass Filter(HPF) 4종, Median Filter(MF) 11종의 모두 20개의 필터를 복합적으로 사용하여 Noise 제거효과를 검토하였다. Noise를 나타내는 지표로 Peak Signal to Noise Ratio(PSNR), Mean Square Error(MSE)를 비교하였다. 그 결과 Noise 감소효과가 가장 높은 필터의 조합은 LPF3*3#1 + HPF3*3#1 + Vertical3*1로 나타났다. 이 필터의 조합을 흉부, 골반, 머리 등의 의료영상에 적용하여 임상적인 Noise 제거효과를 확인하였다.

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Modified Adaptive Gaussian Filter for Removal of Salt and Pepper Noise

  • Li, Zuoyong;Tang, Kezong;Cheng, Yong;Chen, Xiaobo;Zhou, Chongbo
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.9 no.8
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    • pp.2928-2947
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    • 2015
  • Adaptive Gaussian filter (AGF) is a recently developed switching filter to remove salt and pepper noise. AGF first directly identifies pixels of gray levels 0 and 255 as noise pixels, and then only restored noise pixels using a Gaussian filter with adaptive variance based on the estimated noise density. AGF usually achieves better denoising effect in comparison with other filters. However, AGF still fails to obtain good denoising effect on images with noise-free pixels of gray levels 0 and 255, due to its severe false alarm in its noise detection stage. To alleviate this issue, a modified version of AGF is proposed in this paper. Specifically, the proposed filter first performs noise detection via an image block based noise density estimation and sequential noise density guided rectification on the noise detection result of AGF. Then, a modified Gaussian filter with adaptive variance and window size is used to restore the detected noise pixels. The proposed filter has been extensively evaluated on two representative grayscale images and the Berkeley image dataset BSDS300 with 300 images. Experimental results showed that the proposed filter achieved better denoising effect over the state-of-the-art filters, especially on images with noise-free pixels of gray levels 0 and 255.

The effective noise reduction method in infrared image using bilateral filter based on median value

  • Park, Chan-Geun;Choi, Byung-In
    • 한국컴퓨터정보학회논문지
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    • v.21 no.12
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    • pp.27-33
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    • 2016
  • In this paper, we propose the bilateral filter based on median value that can reduce random noise and impulse noise with minimal loss of contour information. In general, EO / IR camera to generate a random or impulse noise due to a number of reasons. This noise reduces the performance of detecting and tracking by signal processing. To reduce noise, our proposed bilateral filter sorts the values of the target pixel and the peripheral pixels, and extracts a median filter coefficients of the Gaussian type. Then to extract the Gaussian filter coefficient involved with the distance between the center pixel and the surrounding pixels. As using those filter coefficients, our proposed method can remove the various noise effectively while minimizing the loss of the contour information. To validate our proposed method, we present experimental results for several IR images.

복합주파수에서 능동소음제어 시스템의 설계와 구현 (An Implementation and Design of Active Noise Control System in the Complex Frequency)

  • 구춘근;이상철
    • 전기학회논문지P
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    • v.50 no.3
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    • pp.130-137
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    • 2001
  • In this paper, we propose a new Active Noise Filter Control System which operate as a control performance when a adaptive filter fault. In this system, half-fixed filter which is new filter, connected to parallel with adaptive filter. An adaptive filler use to continuous parameter estimating, but adaptive filter is fault, half-fixed filter update newly data which is continuous estimating date each during sampling period. We simulate and apply the proposed active noise filter system to in the cylinder type duct. Experimental results show that proposed Active Noise Filter Control System has better control performance than existing filter which Eriksson's or Parallel Filter System in term of noise reduction.

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프레임 단위의 AELMS를 이용한 잡음 제거 알고리즘 (Noise Reduction Algorithm using Average Estimator Least Mean Square Filter of Frame Basis)

  • 안찬식;최기호
    • 디지털융복합연구
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    • v.11 no.7
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    • pp.135-140
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    • 2013
  • 잡음 추정과 검출 알고리즘에서는 LMS Filter를 이용하여 변화하는 잡음 환경에 빠르게 적응할 수 있도록 한다. 하지만 LMS Filter는 잡음 추정을 위한 일정 시간 동안 적응 시간이 필요하며 신호의 변화가 일어날 경우 더 많은 적응 시간이 소요되는 단점을 가지고 있다. 따라서 이를 보완하기 위하여 프레임 단위의 AELMS Filter를 이용한 잡음 제거 방법을 제안한다. 본 논문은 잡음 환경에서 입력되는 신호를 프레임 단위로 분할하고 평균과 분산을 이용한 예측 LMS Filter를 구성하여 잡음을 제거하므로 잡음 환경이 변화하더라도 빠른 적응 시간으로 잡음을 제거한다. 또한 환경 잡음과 음성 신호가 혼합되어 입력될 때 잡음을 제거하여 음성의 고유 특성을 유지하고 음성 정보 손상을 줄이기 위한 방법이다. 프레임 단위의 AELMS Filter를 이용한 잡음 제거 방법으로 잡음 제거 성능을 평가하였다. 실험 결과 변화하는 환경 잡음을 제거하여 얻은 감쇠도가 평균 6.8dB 향상되었다.

잡음제거를 위한 하이브리드 필터 (Hybrid filter for noise reduction)

  • 조범석;김영로
    • 디지털산업정보학회논문지
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    • v.7 no.4
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    • pp.133-139
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    • 2011
  • In this paper, we propose a hybrid filter for noise reduction. The proposed method adjusts rational filtering direction according to an edge in the image using median filtered data. Rational filter modulates the coefficients of a linear lowpass filter to limit its action in presence of image details. By the ratio of polynomials in the input variables, rational filter reduces noise adaptively. Median filter is widely used to reduce impulse noise, but removes some details for highly corrupted images. Also, desirable details are removed when the window size is large. Our proposed algorithm combines rational filter and median filter. Thus, proposed method not only preserves edge, but also reduces noise in uniform region. Experimental results show that our proposed method has better quality than those by existing median and rational filtering methods.

노이즈 필터 도면 표준화 방안에 관한 연구 (A study on the standardization of Noise Filter drawings)

  • 이지혁
    • 품질경영학회지
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    • v.46 no.3
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    • pp.379-396
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    • 2018
  • Purpose: The purpose of this study was to propose a standard form of noise filter drawing, which is widely used in the field of weapon systems, to define the essential specification which is not standardized at the existing drawings and to employ the reference for manufacturing and qualification test. Methods: To do that, it identifies the improvements to analyze 19 noise filter drawings, studies the principle of noise filtering to find the essential part of the spec. and reviews the MIL-STD-220C and KS IEC 60939, which is the widely used as a formal spec. pertaining to the noise filter. Throughout the study, a standard form is developed to standardize the attenuation characteristics and find eight crucial metrics to specify the noise filter. Results: The results of this study are as follows; The standardized drawings can be used as the qualification test of the item and the manufacturing and engineering documents to make the noise filter, which are also applicable to the reference document to review KDS(Korea Defense Standard) drawings.

수정된 Wiener 필터를 사용한 에지 영역에서의 효과적인 잡음 제거 (Effective Noise Suppression in Edge Region Using Modified Wiener Filter)

  • 송영철
    • 대한전기학회논문지:시스템및제어부문D
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    • v.52 no.3
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    • pp.173-180
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    • 2003
  • The modified Wiener filtering method is proposed for effective noise suppression in edge region of images corrupted by additive white gaussian noise. Although the pixels classified as a edge region in the conventional Wiener filter have lots of noise components, the conventional Wiener filler cannot remove noise effectively due to the preserving of edges. To reduce noise well in edge region, we modify filter coefficients of the conventional Wiener filter The modified filter coefficients increase in noise suppression effect In edge region, while they preserve edges for strong edge region. From simulation $(256{\time}256$ size, 256 graylevel images) filtered images by the proposed method show much improved subjective image quality with some improved peak signal-to-noise ratio compared to those by the conventional Wiener filtering.

의학 영상에서의 영역 기반 해상도대잡음비 향상 (Region Based Contrast-to-Noise Ratio Enhancement for Medical Images)

  • 송영철;최두현
    • 대한전기학회논문지:시스템및제어부문D
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    • v.53 no.2
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    • pp.118-126
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    • 2004
  • The modified Wiener filtering method is proposed for effective noise suppression in edge region of images corrupted by additive white gaussian noise. Although the pixels classified as a edge region in the conventional Wiener filter have lots of noise components, the conventional Wiener filter cannot remove noise effectively due to the preserving of edges. To reduce noise well in edge region, we modify filter coefficients of the conventional Wiener filter. The modified filter coefficients increase in noise suppression effect in edge region, while they preserve edges for strong edge region. From simulation (256${\times}$256 size, 256 graylevel images) filtered images by the proposed method show much improved subjective image quality with higher peak signal-to-noise ratio compared to those by the conventional Wiener filtering.

MATHEMATICAL PHASE NOISE MODEL FOR A PHASE-LOCKED-LOOP

  • Limkumnerd, Sethapong;Eungdamrong, Duangrat
    • 제어로봇시스템학회:학술대회논문집
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    • pp.233-236
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    • 2005
  • Phase noise in a phase-locked-loop (PLL) is unwanted and unavoidable. It is a main concern in oscillation system especially PLL. The phase noise is derived in term of power spectrum density by using a reliable phase noise model. There are four noise sources being considered in this paper, which are generated by reference oscillator, voltage controlled oscillator, filter, and main divider. The major concern for this paper is the noise from the filter. Two types of second order low pass filter are used in the PLL system. Applying the mathematical phase noise model, the output noises are compared. The total noise from the passive filter is lower than the active filter at the offset frequency range between 1 Hz to 33 kHz.

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