Elimination Of Distortion Research Articles

High-resolution laser frequency scanning interferometer based on fiber dispersion phase compensation

The laser frequency scanning interferometer has several advantages, such as non-contact, high accuracy and low signal to noise ratio in detection. In order to achieve higher resolution of the laser frequency scanning interferometer, increasing the tuning range of the light source and reducing the tuning non-linearity have become the key factors. The commonly used method is to correct the non-linearity of the wide bandwidth external cavity tuning laser by a fiber optical auxiliary interferometer constructed external frequency sampling clock. When using the broadband external cavity tuning laser and the auxiliary interferometer with an optical path difference of 220 m, it is found experimentally that the single-mode fiber dispersion makes the frequency of sampled signals change over time, causing the spectrum to broaden and resolution to decline. This paper has established the dispersion mismatch model which shows that the fiber dispersion of the auxiliary interferometer causes linear chirp frequency changes during the measurement of signals. The linear chirp frequency is proportional to the tuning bandwidth and measured distance. The phenomenon and theoretical model of dispersion mismatch is verified by experiments. The results for targets in the air are shown to linearly decrease as the tuning range increases with the maximum offset of 156.3 µm for the 20 nm tuning bandwidth. The experiment also proves the peak broadening intensifies with increasing distance measured, and thus verifies as the time delay of free space increase, and the peak broadening and distortion also increases. This result means that it will limit the ranging distance and make large errors in measurement result for long distance targets. The dispersion of the auxiliary interferometer should be compensated in the laser frequency scanning interferometer for large-sized high resolution measurements. In this paper, phase dispersion compensation method based on the evolution of peak variation distortion elimination is proposed, by taking the peak amplitude variation as the criterion; the phase compensation can offset the dispersion and improve the resolution. The original signal is multiplied by the complex phase compensation term, then regulating the phase compensation factor, the chirp becomes smaller as the phase compensation factor is approaching the distortion factor. Under the condition that the phase compensation factor is equal to the distortion factor, the chirp is offset. Then, the relationship between the amplitude and the peak FWHM is studied. It is found that the peak FWHM decreases while the amplitude shows a gradually increasing trend. Therefore, the amplitude can be referred to in order to determine whether the peak FWHM reaches the minimum. The resolution for target's peak can be improved by searching for the maximum amplitude of the spectrum and adjusting the phase distortion coefficient. The experiment shows that the peak FWHM of the target is obviously narrowed after dispersion compensation. The peak value becomes close to the theoretical resolution, and the static target at a distance of 975.216254 mm from the laser frequency scanning interferometer is measured. Results show the measurement accuracy of the interferometer is 584 nm. To further verify the accuracy of the laser frequency scanning interferometer, the laser frequency scanning interferometer is compared with the Renishaw laser interferometer in the measurement range of 0692 mm. The standard deviation between them is 4.5 µm. The proposed method is put forward to provide basis for future studies on the large size high resolution laser frequency scanning interferometer.

Linearization of phase-modulated analog optical links using a four-wave mixing comb source.

We present a novel method for distortion elimination in phase-modulated analog optical links. A small part of the phase modulated signal seeds a four-wave mixing comb source, which generates lightwaves with integer multiples of the phase modulation of the original signal. These lightwaves are scaled and re-combined with the original phase-modulated signal to cancel the distortion generated in the interferometric phase-to-amplitude conversion process. Experimentally, we demonstrate full cancelation of the third-order distortion of the receiver and achieve a 19-dB improvement in the link's SFDR at a 1-Hz bandwidth. This approach is readily extendable to eliminate all relevant higher-order distortion products or synthesize arbitrary phase-to-amplitude transfer functions.

Electric Vehicle Positioning for Inductive Charging Purposes Using Magnetic Field Distortion Elimination in High-Permeability Environments

This paper presents a novel method to position electric vehicles for inductive charging purposes. The approach is to get position information by measuring the magnetic flux density caused by the charging coil located in the ground of the parking place. However, the sensors are mounted at the high-permeable undersurface of the vehicle, which leads to field distortions and, consequently, to high measurement errors. In this paper, these distortions were investigated by means of the finite-element method. Thereby, the vehicle was designed as finite expanded cuboid of high permeability. From these results, a simple mathematical model was derived, which maps the original field to the distorted one. In the following, this model and its validity constraints are discussed more in detail.

On-Orbit Geometric Calibration Model and Its Applications for High-Resolution Optical Satellite Imagery

On-orbit geometric calibration is a key technology to guarantee the geometric quality of high-resolution optical satellite imagery. In this paper, we present an approach for the on-orbit geometric calibration of high-resolution optical satellite imagery, focusing on two core problems: constructing an on-orbit geometric calibration model and proposing a robust calculation method. First, a rigorous geometric imaging model is constructed based on the analysis of the major error sources. Second, we construct an on-orbit geometric calibration model through performing reasonable optimizing and parameter selection of the rigorous geometric imaging model. On this basis, the calibration parameters are partially calculated with a stepwise iterative method by dividing them into two groups: external and internal calibration parameters. Furthermore, to verify the effectiveness of the proposed calibration model and methodology, on-orbit geometric calibration experiments for ZY1-02C panchromatic camera and ZY-3 three-line array camera are conducted using the reference data of the Songshan calibration test site located in the Henan Province, China. The experimental results demonstrate a certain deviation of the on-orbit calibration result from the initial design values of the calibration parameters. Therefore, on-orbit geometric calibration is necessary for optical satellite imagery. On the other hand, by choosing multiple images, which cover different areas and are acquired at different points in time to verify their geometric accuracy before and after calibration, we find that after on-orbit geometric calibration, the geometric accuracy of these images without ground control points is significantly improved. Additionally, due to the effective elimination of the internal distortion of the camera, greater geometric accuracy was achieved with less ground control points than before calibration.

View synthesis distortion elimination filter for depth video coding in 3D video broadcasting

Depth image based rendering (DIBR), which can generate synthesized images according to the users' demand, is a key technique for achieving 3D television. However, view synthesis by DIBR technique is very sensitive to depth coding distortion. Because depth distortion will lead to geometrical rendering position errors, and seriously affect the quality of synthesized images. In this paper, we propose an in-loop filter to minimize view synthesis distortion at the cost of transmitting extra filter parameters as supplementary information. And an adaptive parameter determination scheme is presented for the proposed filter. Then a good trade-off between bit rate and view synthesis distortion has been achieved by considering the spatial-temporal correlations of 3D video sequence. The simulation results reveal that the proposed view synthesis distortion elimination method can significantly improve the rate-distortion performance, which achieves Bjontegaard Delta Peak Signal-to-Noise Ratio (BDPSNR) gain from 0.41 to 1.09 dB compared with the benchmark.

Digital Image Stabilization Based on Harmony Filter

A digital image stabilization algorithm based on a harmony filter is presented in this paper. The corner points are extracted from the reference image. A new motion estimation method based on diamond search (DS) and partial distortion elimination (PDE) algorithm is proposed in the feature block matching. The global motion parameters are obtained based on the affine transformation model and the least square solution. Then a new filter algorithm named harmony filter is adopted to smooth the global motion by separating the active scanning movement from random jitter of camera. Finally, the original jitter sequences are compensated by the correction vectors. Experimental results show that our method can eliminate the high frequency tremble, keep active motion of camera and realize real-time image stabilization.

Use of the Fluoro-ProGraph-RP Digital Fluorograph for Tomosynthesis

Use of the Fluoro-ProGraph-RP digital fluorograph for tomosynthesis is described. Specific conditions for application are listed, and results of its functions are presented. In particular, calibration of a focal spot of X-ray generator is discussed, as well as elimination of optical distortions and experimental tests for marginal effects in the case of large objects. The tests performed in this work show that the Fluoro-ProGraph-RP fluorograph can be used in tomosynthesis.

A single-channel 128 Tbit/s-58 km transmission in the 11 μm band with wideband GVD and slope compensation

We describe a 1.28 Tbit/s single-channel transmission in the 1.1 μm band that uses a high-Δ single-mode step-index fiber (SIF) and ytterbium-doped fiber amplifiers (YDFAs). A 650 fs signal pulse was generated from a 10 GHz mode-locked Yb fiber laser (Yb MLFL) that was soliton-compressed by using an anomalous dispersion photonic crystal fiber (PCF). The dispersion of the SIF was compensated over a bandwidth as broad as 2.1 THz with two cascaded chirped fiber Bragg gratings (FBGs). In addition, an enhanced pre-chirping technique was newly adopted for the precise elimination of the large waveform distortion caused by the dispersion slope. As a result, 320 Gbit/s-161 km and 1.28 Tbit/s-58 km transmissions were successfully achieved.

Third-order intermodulation distortion elimination of microwave photonics link based on integrated dual-drive dual-parallel Mach–Zehnder modulator

A method to realize a highly linear microwave photonics link is proposed based on the dual-drive dual-parallel Mach-Zehnder modulator (MZM). The scheme theoretically eliminates third-order intermodulation distortion (IMD3) completely by taking all the sidebands in the optical spectrum that cause IMD3 into consideration. Without digital linearization and other optical processors, the method utilizes simple electrical signal phase control. Microwave signals are symmetrically single sideband modulated in the two MZMs. IMD3 suppression of approximately 30 dB is experimentally demonstrated, and the spurious-free dynamic range is improved by 12 dB·Hz2/3.

Elimination of tragic end and distortion of history ‒Focused on interrelationship between the incident Genroku and 『Ganadehoh Chusingura』‒

Elimination of tragic end and distortion of history ‒Focused on interrelationship between the incident Genroku and 『Ganadehoh Chusingura』‒

Multichannel Two-Stage Beamforming with Unconstrained Beamformer and Distortion Reduction

This paper proposes a novel multichannel speech enhancement technique for reverberant rooms that is effective when noise sources are spatially stationary, such as a projector fan noise, an air-conditioner noise, and unwanted speech sources at the back of microphones. Speech enhancement performance of the conventional multichannel Wiener filter (MWF) degrades when the Signal-to-Noise Ratio (SNR) of the current microphone input signal changes from the noise-only period. Furthermore, the MWF structure is computationally inefficient, because the MWF updates the whole spatial beamformer periodically to track switching of the speakers (e.g. turn-taking). In contrast to the MWF, the proposed method reduces noise independently of the SNR. The proposed method has a novel two-stage structure, which reduces noise and distortion of the desired source signal in a cascade manner by using two different beamformers. The first beamformer focuses on noise reduction without any constraint on the desired source, which is insensitive to SNR variation. However, the output signal after the first beamformer is distorted. The second beamformer focuses on distortion reduction of the desired source signal. Theoretically, complete elimination of distortion is assured. Additionally, the proposed method has a computationally efficient structure optimized for spatially stationary noise reduction problems. The first beamformer is updated only when the speech enhancement system is initialized. Only the second beamformer is updated periodically to track switching of the active speaker. The experimental results indicate that the proposed method can reduce spatially stationary noise source signals effectively with less distortion of the desired source signal even in a reverberant conference room.

FVQEOPT: Fast Vector Quantization Encoding with Orthogonal Polynomials Transform

This paper deals with a design of new vector quantization algorithm for coding of color images in the Transform domain. In order to speed up the design issue, the feature of transform coding is combined with vector quantization. The transformed training set is obtained with the proposed integer Orthogonal Polynomials transform with reduced computational complexity. The proposed method then generates a single codebook for all the three color components, utilizing the inter-correlation property of the individual color plane as well as interactions among the color planes with the proposed transformation. In the codebook generation phase of the proposed vector quantization encoding, binary tree method is used to achieve considerable saving in codebook construction time. The vector encoding phase uses binary search and partial distortion elimination to further reduce the encoding time for finding closest codeword of an input vector. The experimental result shows that the proposed algorithm greatly reduces the encoding time. The proposed algorithm is also compared with existing standard LBG algorithm.

Analysis of the existing coding methods for ensuring the integrity of information in modern IСNS

The article analyzes the existing methods of error-correcting channel coding secure information networks. The quantitative evaluation of the effectiveness of using a code from the condition of the conditional residual increase the integrity and reliability of the information is stored, transmitted and processed in modern information networks. It is shown that the use of conditional code residues is further complete elimination of distortions in the information message from the condition of occurrence of multiple errors.

Harmonic excitation of linear respiratory mechanics for physiological dual controlled ventilation

The theoretical approach along with the rationale of harmonic excitation modality (HEM) applied as optimal dual controlled ventilation (DCV) to anaesthetized or severe brain injured patients, whose respiretory mechanics can be properly assumed steady and linear, are presented and discussed. The design criteria of an improved version of the Advanced Lung Ventilation System (ALVS), including HEM in its functional features, are described in details. In particular, the elimination of any undesiderable artificial distortion affecting the respiratory and ventilation pattern waveforms is achieved by maintaining continuous forever the airflow inside the ventilation circuit, ensuring also the highest level of safety for patient in any condition. In such a way, the full-time compatibility of controlled breathings with spontaneous breathing activity of patient during continuous positive airways pressure (CPAP) or bilevel positive airways pressure (BiPAP) ventilation modalities and during assisted/controlled ventilation(A/CV), includeing also synchronized or triggered ventilation modalities, is an intrinsic innovative feature of the system available for clinical application. As expected and according to the clinical requirements, HEM provides for physiological respiratory and ventilation pattern waveforms together with optimal “breath to breath” feedback control of lung volume driven by an improved diagnostic measurement procedure, whose outputs are also vital for adapting all the preset ventilation parameters to the current value of the respiratory parameters of patient. The results produced by software simulations concerning both adult and neonatal patients in different clinical conditions are completely consistent with those obtained by the theoretical treatment, showing that HEM reaches the best performances from both clinical and engineering points of view.

Dependence of camera lens induced radial distortion and circle of confusion on object position

Our work presents a theoretical description of camera lens radial distortion and its dependence on the change of the object position with respect to the optical system. We derived approximate formulas within the validity of the third-order aberration theory, which make possible to calculate the changes of lens distortion and the circle of confusion in dependence on the change of the object from the camera lens. These formulas consider a wide angle bundle of rays for calculation of the image point. We also prove that the elimination of distortion by tracing the principal ray does not warrant the removal of distortion of the optical system for the wide angle bundle of rays.

A novel distortion elimination method of power amplifier in wideband OFDM system

The nonlinear, memory and saturate distortion caused by power amplifier lead to low BER performance and low power efficiency in wideband OFDM system. To solve the related problems, a novel power amplifier based on combined amplification with multi power amplifiers is proposed in this paper. In addition, a novel simplified filter look-up table predistorter is proposed. The novel predistorter connects to a memoryless predistorter subsystem with an adaptive filter subsystem in cascade, and can eliminate the nonlinear memory distortion effectively. The simulation results indicate that the power efficiency and BER performance will be improved by using the novel amplifier structure together with the novel predistorter.

Statistical digital image stabilization

In this paper, an efficient algorithm for the statistical digital Image stabilization (SDIS) is proposed to reduce the computational cost of block matching algorithm, for local motion estimation. This method is based on calculation of statistical functions, mean and variance of pixels in each block; four blocks are used in each frame. By using the statistical functions, the best block is selected then the local motion vector (LMV) of selected block is estimated by using full search algorithm. LMV of selected block is used as global motion vector (GMV) and it is used to stabilize current frame. Full search algorithm is used for motion estimation, but instead of searching points in a block for full search, it is used in the partial distortion elimination method to terminate the improper candidate blocks and reduce computation for block matching. Key words: Digital image stabilization, motion estimation, block matching algorithm, global motion vector, statistical functions, partial distortion elimination.

Phase transition of Ni–Mn–Ga alloy powders prepared by vibration ball milling

This study investigated the phase transformation of the flaky shaped Ni–Mn–Ga powder particles with thickness around 1 μm prepared by vibration ball milling and post-annealing. The SEM, XRD, DSC and ac magnetic susceptibility measurement techniques were used to characterize the Ni–Mn–Ga powders. The structural transition of Heusler → disordered fcc occurred in the powders prepared by vibration ball milling (high milling energy) for 4 h, which was different from the structural transition of Heusler → disordered fct of the powders fabricated by planetary ball milling (low milling energy) for 4 h. The two different structures after ball milling should be due to the larger lattice distortion occurred in the vibration ball milling process than in the planetary ball milling process. The structural transition of disordered fcc → disordered bcc took place at ∼320 °C during heating the as-milled Ni–Mn–Ga powders, which was attributed to the elimination of lattice distortion caused by ball milling. The activation energy for this transition was 209 ± 8 kJ/mol. The Ni–Mn–Ga powder annealed at 800 °C mainly contained Heusler austenite phase at room temperature and showed a low volume of martensitic transformation upon cooling. The inhibition of martensitic transformation might be attributed to the reduction of grain size in the annealed Ni–Mn–Ga particles.

広視野３次元CG における歪除去

広視野３次元CG における歪除去

USE X-RAY RADIOMETRIC METHOD FOR DETERMINATION OF LIGHT LANTHANIDES IN THE SOILS

The technique of X-ray fluorescent energy dispersion method - X-ray radiometric analysis using 241Am isotope source for identification of lanthanides: praseodymium, neodymium and samarium - has been developed. The method is based on the elimination of barium distortion and lanthanum on the praseodymium and neodymium line, as well as the effects of lanthanum and selenium on the samarium line. On the basis of the new method it is possible to obtain mass data on the geochemistry of light lanthanides in soils.