Low Noise Density Research Articles

An Improved Method of Adaptive Median Filter Based on Noise Density

To filter salt and pepper noise and protect the texture details of images effectively, an improved method of adaptive median filter is proposed. It can detect the suspicious noise by adjusting the filter window size and adopting the filter algorithm of adaptive texture direction in low density noise area and the filter algorithm of euclidean distance weighted average in high density noise area. Experimental results show that this method has better de-noising and detail-preserving performance.

AN FPGA IMPLEMENTATION OF MODIFIED DECISION BASED UNSYMMETRICAL TRIMMED MEDIAN FILTER FOR THE REMOVAL OF SALT AND PEPPER NOISE IN DIGITAL IMAGES

A modified decision based unsymmetrical trimmed median filter algorithm for the restoration of gray scale, and color images that are highly corrupted by salt and pepper noise is proposed in this paper. Images are often corrupted by impulse noise during acquisition and transmission; thus, an efficient noise suppression technique is required before subsequent image processing operations. Median filter (MF) is widely used in noise removal methods due to its denoising capability and computational efficiency. However, it is effective only for low noise densities. Extensive experimental results demonstrate that our method can obtain better performances in terms of both subjective and objective evaluations than denoising techniques. Especially, the proposed method can preserve edges very well while removing salt and pepper noise. Modified Decision Based Algorithm (MDBA), and Progressive Switched Median Filter (PSMF) shows better results at low and medium noise densities. At high noise densities, their performance is poor. A new algorithm to remove high-density salt and pepper noise using modified Decision Based Unsymmetric Trimmed Median Filter (DBUTMF) is proposed. The proposed algorithm replaces the noisy pixel by trimmed median. Since our algorithm is algorithmically simple, it is very suitable to be applied to many real-time applications and higher noise densities. When all the pixel values are 0’s and 255’s then the noise pixel is replaced by mean value of all the elements present in the selected window. The proposed algorithm is tested against different grayscale and color images and it gives better Peak Signal-to-Noise Ratio (PSNR) and Image Enhancement Factor (IEF).

Design and Simulation of Brushless Direct Current Motor Drive

Instead of mechanical commutator for DC motor, Brushless DC motor used electronic commutator. And brushless DC motor (BLDCM) extended the effective using time of a motor and eliminated some problems caused by the mechanical commutator, such as electromagnetic interference, brush wear, frequent maintenance and etc. At the meantime, brushless DC motor inherited a few advantages from DC motor, like wide speed range, large torque, stable operation, low noise, and high power density; there is great significance in researching BLDCM control system. This paper researches the application of fuzzy control strategy in BLDCM (brushless direct-current motor) control system. The design and simulation of BLDCM control system based on DSP controller also presented in the paper.

A low-power digital processing circuit for capacitive accelerometer

A low power consumption digital processing circuit with large dynamic range and low noise density for micromachined capacitive accelerometer is proposed. To reduce the power consumption, the sampling rate and the number of logic units used are analyzed. We lower the sampling rate to 2.5 MHz that is only 1/16 of previous scheme. At this frequency, the dynamic range is still as high as 120 dB that has been tested, while the dynamic power is as low as 5.4 mW that is only about 1/16 of previous scheme. To reduce the amount of logic units, we adopt square-wave demodulator instead of sinusoidal demodulator (realized by coordinate rotation digital computer algorithm). The entire digital processing circuit with square-wave demodulator uses 577 slice registers, about 1/10 of the circuit with sinusoidal demodulator. The dynamic power is even reduced to 0.54 mW. Most of all, almost no additional noise is added into this circuit, and the output noise density is as low as 0.01 mg/√Hz.

Restoration of Images Corrupted by High Density Salt & Pepper Noise through Adaptive Median Based Modified Mean Filter

In this paper an efficient algorithm is proposed for removal of salt & pepper noise from digital images. Salt and pepper noise in images is present due to bit errors in transmission or introduced during the signal acquisition stage. It represents itself as randomly occurring white and black pixels. This noise can be removed using standard Median Filter (SMF), Progressive Switched Median Filter (PSMF) under low density noise conditions. Decision Based Algorithm (DBA) and Modified Decision Based Unsymmetric Trimmed Median Filter (MDBUTMF) do not give better results at high noise density. So, in this project, this drawback will be overcome by using Adaptive Median based Modified Mean Filter (AMMF). This proposed algorithm shows better Peak Signal-to-Noise Ratio and clear image than the existing algorithm. Keywords- Median filter, Progressive Switched Median Filter, Decision Based Algorithm, Modified Decision Based Unsymmetric Trimmed Median Filter

Reconstruction of Corrupted Image From Salt And Pepper Noise From Median Filter

- Inthis paper,we propose an improved median filtering algorithm. Here, we introduced salt and pepper noise for the image corruption and reconstruct original image using different filters i.e. mean, median and improved median filter. The performance of improved median filter is good at lower noise density levels.The mean filter suppresses little noise and gets the worst results.The experimental resultsshow that our improved median filter is better than previousmedian filterfor lower noise density (upto 60%). It removes most of the noises effectively while preserving image details very well.

Enhanced Switching Median Filter for Denoising in 2D Patterned Textile Images

Wallpaper fabric, a part of patterned fabric, is a new decorative material covered with fabric or other natural fibre materials. Wallpaper fabrics are different from other indoor decorative materials and are designed for daily use with easy maintenance instructions. Because of their high demand, quality assurance or fault detection and recognition, in wallpaper fabrics is important. One step that is important during fault detection is the removal of noise. A common type of noise that affects patterned fabric images is the impulse noise. In this paper, a method that modifies a switching median filter is proposed. The algorithm contains two stages, namely, noise detection stage and noise filtering stage. During noise detection a modified adaptive switching median filter with three new thresholds are used to remove the impulse noise. During filtering stage, an adaptive switching median filter is used to determine the size of the sliding window. To detect noisy pixels which are close to its neighbours that are normally missed with the traditional threshold of switching median filter, a modified threshold that considers the ranking order of the pixels in the sliding window is used. Both the enhanced stages improve the noise removal process while maintaining image details. The proposed denoising model was evaluated using three performance metrics, namely, PSNR, FoM and execution time. The experimental results showed that the proposed model is efficient in removing impulse noise with low and high noise density while preserving important image and edge details.

Application of the KolibriSensor® to combined atomic-resolution scanning tunneling microscopy and noncontact atomic-force microscopy imaging

Combined atomic-resolution scanning tunneling microscopy (STM) and noncontact atomic-force microscopy (NC-AFM) studies are carried out with the piezoelectric KolibriSensor in ultrahigh vacuum at room temperature. The sensor exhibits a very low spectral deflection noise density of only 6.5 fm/Hz which favors in combination with its high spring constant of 540 000 N/m stable NC-AFM operation at subnanometer oscillation amplitudes. The authors present atomic-resolution imaging on the Si(111)(7×7) surface recorded in STM and NC-AFM feedback mode. They find that the tip surface distance during atomic-resolution imaging on silicon is much smaller for NC-AFM compared to STM. It is shown that atomic-resolution NC-AFM and dynamic STM images of the same area on the Si(111)(7×7) surface enable a discrimination of vacancies and adsorbates. Furthermore, the topography of graphite imaged in dynamic STM and NC-AFM feedback mode is compared.

Symmetry: Modeling the Effects of Masking Noise, Axial Cueing and Salience

Symmetry detection is an interesting probe of pattern processing because it requires the matching of novel patterns without the benefit of prior recognition. However, there is evidence that prior knowledge of the axis location plays an important role in symmetry detection. We investigated how the prior information about the symmetry axis affects symmetry detection under noise-masking conditions. The target stimuli were random-dot displays structured to be symmetric about vertical, horizontal, or diagonal axes and viewed through eight apertures (1.2° diameter) evenly distributed around a 6° diameter circle. The information about axis orientation was manipulated by (1) cueing of axis orientation before the trial and (2) varying axis salience by including or excluding the axis region within the noise apertures. The percentage of correct detection of the symmetry was measured at for a range of both target and masking noise densities. The threshold vs. noise density function was flat at low noise density and increased with a slope of 0.75–0.8 beyond a critical density. Axis cueing reduced the target threshold 2–4fold at all noise densities while axis salience had an effect only at high noise density. Our results are inconsistent with an ideal observer or signal-to-noise account of symmetry detection but can be explained by a multiple-channel model is which the response in each channel is the ratio between the nonlinear transform of the responses of sets of early symmetry detectors and the sum of external and intrinsic sources of noise.

무선 MEMS 시스템을 이용한 구조물 식별

The structural health monitoring has been gaining more importance in civil engineering areas such as earthquake and wind engineering. The use of health monitoring system can also provide tools for the validation of structural analytical model. However, only few structures such as historical buildings and some important long bridges have been instrumented with structural monitoring system due to high cost of installation, long and complicated installation of system wires. In this paper, the structural monitoring system based on cheap and wireless monitoring system is investigated. The use of advanced technology of micro-electro-mechanical system(MEMS) and wireless communication can reduce system cost and simplify the installation. Further the application of wireless MEMS system can provide enhanced system functionality and due to low noise densities. Identification results are compared to ones using data measured from traditional accelerometers and results indicate that the system identification using wireless MEMS system estimates system parameters accurately.

SOI Low Frequency Noise and Interface Trap Density Measurements with the Pseudo MOSFET

Low frequency noise (LFN) is important in analog and digital circuits. In analog circuits it affects the performance of low- noise amplifiers and the phase noise of voltage-controlled oscillators. In digital circuits it becomes more important as the supply voltage is reduced and it degrades substrate noise coupling. Low-frequency noise is due to interactions of the channel carriers with oxide/semiconductor interface traps and oxide charges and is very dependent on the quality of the oxide/semiconductor interface and noise measurements can give important information about such interfaces and defects (1). Silicon-on-insulator devices have two oxide/semiconductor interfaces and the bottom interface is generally worse than the top interface. Most LFN measurements are made after MOSFET fabrication, but it is desirable to characterize such materials without fabricating devices. In this paper we discuss silicon- on-insulator (SOI) low-frequency noise and interface trap density measurements using a Ground-Signal-Ground (GSG) pseudo- MOSFET structure with minimum fabrication.

SOI Low Frequency Noise and Interface Trap Density Measurements with the Pseudo MOSFET

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Magnetoresistive magnetometer with improved bandwidth and response characteristics

We report on the realization and characterization of a high performance, compact magnetometer based on a magnetoresistive sensor and working in the range ±600μT. The output is provided both numerically and by means of a field-proportional voltage. Spurious offset effects are suppressed by flipping the film magnetization at a frequency of 100kHz, 2∕3 orders of magnitude higher than in conventional applications. The design allows for a field resolution of 20nT, low output noise density, and high precision and accuracy (relative full-scale uncertainty of about 500ppm).

The Outer Tracker detector of the HERA-B experiment. Part II: Front-end electronics

The HERA-B Outer Tracker is a large detector with 112,674 drift chamber channels. It is exposed to a particle flux of up to 2 × 10 5 cm - 2 s - 1 thus coping with conditions similar to those expected for the LHC experiments. The front-end readout system, based on the ASD-8 chip and a customized TDC chip, is designed to fulfil the requirements on low noise, high sensitivity, rate tolerance, and high integration density. The TDC system is based on an ASIC which digitizes the time in bins of about 0.5 ns within a total of 256 bins. The chip also comprises a pipeline to store data from 128 events which is required for a deadtime-free trigger and data acquisition system. We report on the development, installation, and commissioning of the front-end electronics, including the grounding and noise suppression schemes, and discuss its performance in the HERA-B experiment.

Design of Piezoresistive MEMS-Based Accelerometer for Integration with Wireless Sensing Unit for Structural Monitoring

The use of advanced embedded system technologies such as microelectromechanical system ~MEMS! sensors and wireless communications hold great promise for measuring the response of civil structures to ambient and external disturbances. In this paper, the design of a high-performance, planar piezoresistive MEMS accelerometer is discussed in detail. The piezoresistive accelerometer pos- sesses superior performance characteristics including low noise densities when measuring local structural responses characterized by high-frequency content. A low-cost wireless sensing unit, designed for automated structural monitoring, is utilized to record and wirelessly transmit measurements obtained by the piezoresistive accelerometer. To validate the performance of the wireless monitoring system including the interfaced piezoresistive accelerometer, a five degrees-of-freedom laboratory test structure is utilized.

Density and Hα diagnostics and results for the sustained spheromak physics experiment

A newly installed density diagnostic using CO2 laser interferometry and an Hα diagnostic using interference filters and photomultiplier tubes for the recently constructed sustained spheromak physics experiment (SSPX) are described. First diagnostic results of the Hα diagnostic were useful to understand the breakdown physics in the new SSPX experiments. Low-noise density data validates techniques to reduce vibration and electronic pickup. The data-processing electronics of the new interferometer can yield unambiguous density data that is equivalent to 16 fringe shifts. Density data is also critical to understand the particle source, and the J/ne parameter for SSPX.

Low complexity signal space detection for MTR coded channels

Two new signal space detectors designed to take advantage of maximum transition run (MTR) coded modulation are presented. These detectors are designed to perform across a wide range of densities and offer lower error rates than a 3D-110 detector at low densities while requiring only modest increases in complexity. The first scheme, 2D-121/spl alpha/ employs an equalization constraint that reduces low density noise correlation relative to the 3D-110 target. The second uses a 3D-110 detector but includes a linear noise predictive filter to reduce the effective noise between the minimum distance sequences. Analysis and simulation results indicate that the two detectors perform equally well in terms of bit error rate.

The fluctuation-imposed limit for temperature measurement

In experimental sciences, random processes often place a fundamental limit on the achievable measurement resolution. A well known example is the Johnson noise voltage across a resistor. In this paper, we describe observations of the spontaneous transfer of heat in two equilibrium systems: one consisting of a thermometer linked to a reservoir, the other consisting of two thermometers connected to each other and linked to a reservoir for the purpose of temperature stabilization. In the second system, we find anti-correlations between the temperature fluctuations of the two thermometers at intermediate frequencies. We also find that the low frequency temperature noise density of the thermometers, in units of $$K/\sqrt {Hz} $$ , is given by $$\sqrt {4Rk_B T^2 } $$ , whereR is the thermal resistance of the link between the thermometer and the reservoir. This implies that for noise reduction purposes,R is the only available engineering parameter to adjust. In a recent thermometer design, we have reduced R to achieve a low frequency temperature noise density of 5×10−11 $$K/\sqrt {Hz} $$ at 2.18 K.

Induced twinkle aftereffect as a probe of dynamic visual processing mechanisms

After viewing a blank patch surrounded by a dynamic noise stimulus (a video “snowstorm”), viewers report the prolonged perception of twinkle in the unstimulated region of the blank patch. We compare this induced twinkle aftereffect to the filling-in phenomenon, which may be seen in a small blank region, under similar test conditions but during stimulation. We found that strong induced twinkle aftereffects were seen both centrally and peripherally for blank test regions from 0.5 deg to as large as 20 deg in diameter, whereas filling-in was seen centrally only for test patch diameters smaller than 0.75 deg, becoming stronger peripherally but still limited to test regions less than about 3 deg in diameter. Lower noise density and larger noise element size facilitated filling-in but had little effect on the induced twinkle aftereflect. Conversely, noise frame rate had little effect on filling-in but had to be faster than 10 frames/sec to produce a twinkle aftereflect. Induced twinkle showed binocular superiority but no interocular transfer. The binocular superiority was partially explained by monocular blankout of the dynamic noise by the blank field in the occluded eye. These results all imply a different mechanism for the induced twinkle aftereffect than for filling-in. We consider a model in which the induced twinkle aftereflect is produced by post-inhibitory rebound in complex cells.

Vibration fringes by phase stepping on an electronic speckle pattern interferometer: an analysis

A detailed analysis of the vibration fringes obtained by phase stepping on a time-averaged electronic speckle pattern interferometer is presented. It is shown that the contrast of the fringes remains relatively high for any phase step between 30 degrees and 180 degrees for low electronic noise and fringe density. Also, for the four-phase-stepped method, the vibration fringes have the same contrast as that of the pi-phase-shift method except that the high-frequency speckles are smoothed. The contrast of the fringes obtained with extra phase steps along with incoherent superimposition is shown to be higher than the single- or four-phase-step method. Both theory and experimental results are presented.