Showing papers on "Spatial filter published in 2017"
TL;DR: The purpose of this paper is to evaluate and compare the performance of several linear spatial filtering techniques, with a focus on those that use generalized eigendecomposition to facilitate dimensionality reduction and signal-to-noise ratio maximization.
78 citations
TL;DR: In this article, a regularized version of the regularized orthogonal decomposition (Reg-ROM) was proposed, which aims to add numerical stabilization to proper POD ROMs for convection-dominated flows.
Abstract: Summary
In this paper, we propose a new evolve-then-filter reduced order model (EF-ROM). This is a regularized ROM (Reg-ROM), which aims to add numerical stabilization to proper orthogonal decomposition (POD) ROMs for convection-dominated flows. We also consider the Leray ROM (L-ROM). These two Reg-ROMs use explicit ROM spatial filtering to smooth (regularize) various terms in the ROMs. Two spatial filters are used: a POD projection onto a POD subspace (Proj) and a new POD differential filter (DF). The four Reg-ROM/filter combinations are tested in the numerical simulation of the three-dimensional flow past a circular cylinder at a Reynolds number Re = 1000. Overall, the most accurate Reg-ROM/filter combination is EF-ROM-DF. Furthermore, the spatial filter has a higher impact on the Reg-ROM than the regularization used. Indeed, the DF generally yields better results than Proj for both the EF-ROM and L-ROM. Finally, the CPU times of the four Reg-ROM/filter combinations are orders of magnitude lower than the CPU time of the DNS. This article is protected by copyright. All rights reserved.
72 citations
TL;DR: In this article, a simple Fourier spectral-based method is proposed to calculate the modal curvature (MC) of beams instead of the traditional central difference method, which provides an alternative selection to estimate MC in damage detection.
70 citations
Patent•
23 Jun 2017
TL;DR: In this paper, a near-to-eye display device includes a spatial light modulator that modulates an illumination wave to create a virtual scene wave that is steered to a useful portion of an exit pupil plane.
Abstract: A near-to-eye display device includes a spatial light modulator. The spatial light modulator modulates an illumination wave to create a virtual-scene wave that is steered to a useful portion of an exit pupil plane. Higher diffraction orders and noise beams are filtered out by the user's pupil acting as a spatial filter.
67 citations
TL;DR: This work improved the previous laser optical system for matrix-assisted laser desorption ionization (MALDI)-MSI, from ~9 μm practical laser spot size to a practical laser Spot size of ~4 μm, thereby allowing for 5 μm resolution imaging without oversampling.
67 citations
TL;DR: In this article, an interferometric scattering microscope is adapted by performing spatial filtering of output light, which comprises both light scattered from a sample location and illuminating light reflected from the sample location, prior to detection of the output light.
Abstract: An interferometric scattering microscope is adapted by performing spatial filtering of output light, which comprises both light scattered from a sample location and illuminating light reflected from the sample location, prior to detection of the output light. The spatial filtering passes the reflected illumination light but with a reduction in intensity that is greater within a predetermined numerical aperture than at larger numerical apertures. This enhances the imaging contrast for coherent illumination, particularly for objects that are weak scatterers.
58 citations
TL;DR: The accuracy of DOA estimation using PIVs and SSPIVs is compared against the state of the art in simulations including realistic reverberation and noise for single and multiple, stationary and moving sources.
Abstract: Direction of arrival DOA estimation is a fundamental problem in acoustic signal processing. It is used in a diverse range of applications, including spatial filtering, speech dereverberation, source separation and diarization. Intensity vector-based DOA estimation is attractive, especially for spherical sensor arrays, because it is computationally efficient. Two such methods are presented that operate on a spherical harmonic decomposition of a sound field observed using a spherical microphone array. The first uses pseudointensity vectors PIVs and works well in acoustic environments where only one sound source is active at any time. The second uses subspace pseudointensity vectors SSPIVs and is targeted at environments where multiple simultaneous soures and significant levels of reverberation make the problem more challenging. Analytical models are used to quantify the effects of an interfering source, diffuse noise, and sensor noise on PIVs and SSPIVs. The accuracy of DOA estimation using PIVs and SSPIVs is compared against the state of the art in simulations including realistic reverberation and noise for single and multiple, stationary and moving sources. Finally, robust performance of the proposed methods is demonstrated by using speech recordings in a real acoustic environment.
56 citations
TL;DR: In this study, the numerical correlation is performed with a phase-only filter, and the phase function of the Fourier transform of the source point hologram is used as the spatial filter in the correlation process.
Abstract: Coded aperture correlation holography (COACH) is a recently introduced technique for recording incoherent digital holograms of general three-dimensional scenes. In COACH, a random-like coded phase mask (CPM) is used as a coded aperture. Even though the CPM is optimized to reduce background noise, there is still a substantial amount of noise, mitigating the performance of COACH. In order to reduce the noise, we first modify the hologram reconstruction method. Instead of computing the correlation between a complex hologram of the entire object and a hologram of a source point, in this study the numerical correlation is performed with a phase-only filter. In other words, the phase function of the Fourier transform of the source point hologram is used as the spatial filter in the correlation process. Furthermore, we propose and demonstrate two additional methods for reducing the background noise in COACH. The first is based on the integration of a quadratic phase function, as used in Fresnel incoherent correlation holography (FINCH), with the CPM of COACH. This hybrid COACH-FINCH system enables a dynamic trade-off between the amount of background noise and the axial resolution of the system. The second method is employed by recording COACH holograms with multiple independent CPMs and averaging over the reconstructed images. The results of the above two techniques are compared with FINCH and with a regular imaging system.
52 citations
TL;DR: A super-resolution reconstructed image has been achieved, in which the spatial resolution can exceed the Rayleigh diffraction limit by more than a factor of two.
Abstract: A sub-Rayleigh resolution ghost imaging experiment is performed via post-detection spatial low-pass filtering of the instantaneous intensity. A super-resolution reconstructed image has been achieved, in which the spatial resolution can exceed the Rayleigh diffraction limit by more than a factor of two. The resolution depends on the filter threshold, and the Rayleigh limit can be exceeded for a wide choice of threshold values. The setup is simple and easy to implement, which is an advantage for practical applications.
47 citations
TL;DR: In this article, the authors proposed to use the time-frequency processing approach, which formulates a spatial filter that can enhance a target direction based on local direction of arrival estimates at individual timefrequency bins.
Abstract: When a micro aerial vehicle (MAV) captures sounds emitted by a ground or aerial source, its motors and propellers are much closer to the microphone(s) than the sound source, thus leading to extremely low signal-to-noise ratios (SNR), e.g., −15 dB. While microphone-array techniques have been investigated intensively, their application to MAV-based ego-noise reduction has been rarely reported in the literature. To fill this gap, we implement and compare three types of microphone-array algorithms to enhance the target sound captured by an MAV. These algorithms include a recently emerged technique, time-frequency spatial filtering, and two well-known techniques, beamforming and blind source separation. In particular, based on the observation that the target sound and the ego-noise usually have concentrated energy at sparsely isolated time-frequency bins, we propose to use the time-frequency processing approach, which formulates a spatial filter that can enhance a target direction based on local direction of arrival estimates at individual time-frequency bins. By exploiting the time-frequency sparsity of the acoustic signal, this spatial filter works robustly for sound enhancement in the presence of strong ego-noise. We analyze in details the three techniques and conduct a comparative evaluation with real-recorded MAV sounds. Experimental results show the superiority of blind source separation and time-frequency filtering in low-SNR scenarios.
43 citations
TL;DR: It is shown that either isotropic or anisotropic edge enhancement in any desired orientation can be performed by operating the same spatial filter setup in different illuminating polarization states.
Abstract: Using polarization as an additional parameter apart from amplitude and phase in spatial filtering experiments offers additional advantages and possibilities. An S-waveplate that can convert a linearly polarized light into radially or azimuthally polarized light can also be used for isotropic edge enhancement. For anisotropic edge enhancement, introduction of a polarizer at the output was recommended and edge selection was done by orientation of the polarizer. But the full potential of the S-waveplate as a spatial filter has not been exploited so far. Unlike the standard amplitude and phase-based Fourier filters, which are independent to the state of polarization of the illuminating beam, the S-waveplate acts in a different way depending on the state of polarization. The edge selection does not need to be carried out by changing the orientation of the polarizer. With a fixed polarizer at the output, we show that either isotropic or anisotropic edge enhancement in any desired orientation can be performed by operating the same spatial filter setup in different illuminating polarization states.
TL;DR: An endoscopic μOCT probe with an extended DOF is reported by using a binary phase spatial filter and the feasibility of clinical use was demonstrated by ex vivo imaging of the rabbit iliac artery.
Abstract: Micro-optical coherence tomography (μOCT) is an advanced imaging technique that acquires a three-dimensional microstructure of biological samples with a high spatial resolution, up to 1 μm, by using a broadband light source and a high numerical aperture (NA) lens. As high NA produces a short depth of focus (DOF), extending the DOF is necessary to obtain a reasonable imaging depth. However, due to the complexity of optics and the limited space, it has been challenging to fabricate endoscopic μOCT, which is essential for clinical translation. Here, we report an endoscopic μOCT probe with an extended DOF by using a binary phase spatial filter. The imaging results from latex beads demonstrated that the μOCT probe achieved an axial resolution of 2.49 μm and a lateral resolution of 2.59 μm with a DOF extended by a factor of 2. The feasibility of clinical use was demonstrated by ex vivo imaging of the rabbit iliac artery.
TL;DR: This work proposes a frequency-translational arbitrary spatial filtering technique that features not only arbitrary spatial filter response generation at baseband for the protection of the following analog-to-digital converters, but modulated baseband input impedance that can be translated by passive mixers to achieve arbitrary spatial filters at RF as well.
Abstract: Traditional digital multiple-input multiple-output (MIMO) receivers that feature element-level digitization face high instantaneous dynamic range challenges in the analog/RF domain due to the absence of analog/RF spatial filtering. Existing analog/RF spatial notch filtering techniques are limited in their noise, linearity, and spatial filtering bandwidth performance. More importantly, only single spatial notches have been demonstrated, providing insufficient filtering in practical scenarios. We propose a frequency-translational arbitrary spatial filtering technique that features not only arbitrary spatial filtering response generation at baseband for the protection of the following analog-to-digital converters, but modulated baseband input impedance that can be translated by passive mixers to achieve arbitrary spatial filtering at RF as well. This technique allows the synthesis and independent steering of an arbitrary number of spatial notches, and the independent adjustment of notch depths. Current-mode operation leads to superior linearity performance and ultra-wideband rejection. A four-element 65-nm CMOS 0.1–3.1 GHz prototype MIMO receiver array shows arbitrary spatial response formation, more than 50-dB spatial rejection across all measured directions, and an ultra-wide 320-MHz 20-dB rejection bandwidth for a single-notch setting at 500-MHz local oscillator (LO) frequency. Formation of a single spatial notch only moderately degrades the equivalent single-element double-sideband noise figure from 2.1–3.7 dB to 3.4–5.8 dB. In the notch direction, +34 dBV in-band output-referred IP3 is measured, an improvement of 33 dB compared with outside-notch directions. A wireless demonstration shows the receiver array demodulating a weak spatial signal in the presence of two strong in-band spatial signals, verifying the arbitrary spatial filtering functionality.
05 Mar 2017
TL;DR: Experimental results with real-recorded MAV ego-noise show the superiority of the proposed time-frequency processing framework over the state of the art in performing source localization robustly.
Abstract: We address the problem of sound source localization with a microphone array mounted on a micro aerial vehicle (MAV). Due to the noise generated by motors and propellers, this scenario is characterized by extremely low signal-to-noise ratios (SNR). Based on the observation that the energy of MAV sound recordings is usually concentrated at isolated time-frequency bins, we propose a time-frequency processing framework to address this problem. We first estimate the direction of arrival of the sound at individual time-frequency bins. Then we formulate a set of spatially informed filters pointing at candidate directions in the search space. The output of the filtering tends to present high non-Gaussianity when the spatial filter is steered towards the target sound source. Finally, by measuring the non-Gaussianity of the spatial filtering outputs we build a spatial likelihood function from which we estimate the direction of the target sound. Experimental results with real-recorded MAV ego-noise show the superiority of the proposed method over the state of the art in performing source localization robustly.
TL;DR: Two-color side-view probing of light-matter interaction from minute focal volume of a tightly focused fs-laser pump pulse reveals charge dynamics with high 0.9μm optical resolution and approximately ~45fs temporal resolution defined by pulse duration as discussed by the authors.
Abstract: Two-color side-view probing of light-matter interaction from minute focal volume of a tightly focused fs-laser pump pulse reveals charge dynamics with high 0.9 μm optical resolution and approximately ~45fs temporal resolution defined by pulse duration. Use of two colors is advantageous for probing optically excited plasma regions with different density. Holographical digital focusing and spatial filtering were implemented to obtain the same resolution images for subsequent Fourier analysis. Fast plasma density decay with time constant ~150 fs was resolved and is consistent with self-trapping. Potential applications of an optical control over light-induced defects with deep-sub-wavelength resolution is discussed.
TL;DR: In this article, the authors presented the Chebyshev pseudo spectral modal curvature formulation for damage detection in beam-like composite structures, which is an extension of authors' former work which is based on the Fourier spectral method.
DOI•
12 Dec 2017
TL;DR: In this article, the fundamental properties of computed flow fields using particle imaging velocimetry (PIV) have been investigated, viewing PIV processing as a black box without going in detail into algorithmic details.
Abstract: The fundamental properties of computed flow fields using particle imaging velocimetry (PIV) have been investigated, viewing PIV processing as a black box without going in detail into algorithmic details. PIV processing can be analyzed using a linear filter model, i.e. assuming that the computed displacement field is the result of some spatial filtering of the underlying true flow field given a particular shape of the filter function. From such a mathematical framework, relationships are derived between the underlying filter function, wavelength response function (MTF) and response to a step function, power spectral density, and spatial autocorrelation of filter function and noise. A definition of a spatial resolution is provided independent of some arbitrary threshold e.g of the wavelength response function and provides the user with a single number to appropriately set the parameters of the PIV algorithm required for detecting small velocity fluctuations. The most important error sources in PIV are discussed and an uncertainty quantification method based on correlation statistics is derived, which has been compared to other available UQ-methods in two recent publications (Sciacchitano et al. 2015; Boomsma et al. 2016) showing good sensitivity to a variety of error sources. Instantaneous local velocity uncertainties are propagated for derived instantaneous and statistical quantities like vorticity, averages, Reynolds stresses and others. For Stereo-PIV the uncertainties of the 2C-velocity fields of the two cameras are propagated into uncertainties of the computed final 3C-velocity field. A new anisotropic denoising scheme as a post-processing step is presented which uses the uncertainties comparing to the local flow gradients in order to devise an optimal filter kernel for reducing the noise without suppressing true small-scale flow fluctuations. For Stereo-PIV and volumetric PIV/PTV, an accurate perspective calibration is mandatory. A Stereo-PIV self-calibration technique is described to correct misalignment between the actual position of the light sheet and where it is supposed to be according to the initial calibration procedure. For volumetric PIV/PTV, a volumetric self-calibration (VSC) procedure is presented to correct local calibration errors everywhere in the measurement volume. Finally, an iterative method for reconstructing particles (IPR) in a volume is developed, which is the basis for the recently introduced Shake-the-Box (STB) technique (Schanz et al. 2016).
TL;DR: A general filtering method based on variational image decomposition that can filter speckle noise for ESPI fringe images with various densities and compared with the windowed Fourier transform method and coherence enhancing diffusion partial differential equation filter, which may be the most effective filtering methods at present.
Abstract: Filtering off speckle noise from a fringe image is one of the key tasks in electronic speckle pattern interferometry (ESPI) In general, ESPI fringe images can be divided into three categories: low-density fringe images, high-density fringe images, and variable-density fringe images In this paper, we first present a general filtering method based on variational image decomposition that can filter speckle noise for ESPI fringe images with various densities In our method, a variable-density ESPI fringe image is decomposed into low-density fringes, high-density fringes, and noise A low-density fringe image is decomposed into low-density fringes and noise A high-density fringe image is decomposed into high-density fringes and noise We give some suitable function spaces to describe low-density fringes, high-density fringes, and noise, respectively Then we construct several models and numerical algorithms for ESPI fringe images with various densities And we investigate the performance of these models via our extensive experiments Finally, we compare our proposed models with the windowed Fourier transform method and coherence enhancing diffusion partial differential equation filter These two methods may be the most effective filtering methods at present Furthermore, we use the proposed method to filter a collection of the experimentally obtained ESPI fringe images with poor quality The experimental results demonstrate the performance of our proposed method
TL;DR: A method for phase visualization in the images of transparent specimens using analog image processing in incoherent light is reported, and the processing of microscopic images of unstained and stained histological sections of human thyroid tumor with improved contrast is demonstrated.
Abstract: We report a method for phase visualization in the images of transparent specimens using analog image processing in incoherent light. The experimental technique is based on adaptive bandpass spatial filtering with an amplitude mask matched with an acousto-optic tunable filter in a telecentric optical system. We demonstrate the processing of microscopic images of unstained and stained histological sections of human thyroid tumor with improved contrast.
TL;DR: In this paper, the authors designed, simulated, and experimentally tested extremely subwavelength evanescent Bessel beam launchers, which consist of several concentric coils strategically positioned to spatially filter the fields of a single actively fed radiating coil.
Abstract: In this paper, extremely subwavelength evanescent Bessel beam launchers are designed, simulated, and experimentally tested to generate nondiffracting beams. The launching apertures consist of several concentric coils strategically positioned to spatially filter the fields of a single actively fed radiating coil. The geometrical properties of each coil element of the aperture were obtained through a procedure based on the orthogonal matching pursuit algorithm in order to maximize the quality of the launched beam while minimizing manufacturing complexity. Two apertures with outer diameters of 64 and 48 mm were fabricated and the generated field distributions were measured at the operating frequencies of 13.66 and 13.86 MHz, respectively. Desired and measured field distributions exhibited correlations above 0.9 even as the distance from the aperture was increased, demonstrating the ability of the apertures to approximate the field distribution and harmonic content of a Bessel beam. This paper furthers the study and practical implementation of Bessel beams and other types of beams in extremely subwavelength applications such as focusing, wireless power transfer, magnetic stimulation, and microwave ablation.
TL;DR: In this paper, a comprehensive comparative study of spatial filtering is conducted, where 10 kinds of filters are used to smooth the hyperspectral images and the classified maps, respectively, and experimental results show that most filtering-based classification methods perform well with high efficiency.
Abstract: The classification of hyperspectral images benefits greatly from integration of spectral information and spatial context. There have been many means to incorporate spatial information into the classification, such as the Markov random field, extended morphological profiles, and segmentation-based methods. Recently, spatial filtering was introduced to improve the classification accuracy of hyperspectral images. Compared with other spectral-spatial algorithms, spatial filtering is simple and easy to implement. This advantage makes it suitable for practical applications. However, spatial filtering has not been given enough attention. A comprehensive comparative study of spatial filtering is conducted. Specifically, 10 kinds of filters are used to smooth the hyperspectral images and the classified maps, respectively. The experimental results show that most filtering-based classification methods perform well with high efficiency.
TL;DR: Broad-area quantum cascade lasers with high output powers are reported and their response to a nonlinear control based on optical feedback is studied, enabling to efficiently tailor its near-field beam profile.
Abstract: Broad-area quantum cascade lasers with high output powers are highly desirable sources for various applications including infrared countermeasures. However, such structures suffer from strongly deteriorated beam quality due to multimode behavior, diffraction of light and self-focusing. Quantum cascade lasers presenting high performances in terms of power and heat-load dissipation are reported and their response to a nonlinear control based on optical feedback is studied. Applying optical feedback enables to efficiently tailor its near-field beam profile. The different cavity modes are sequentially excited by shifting the feedback mirror angle. Further control of the near-field profile is demonstrated using spatial filtering. The impact of an inhomogeneous gain as well as the influence of the cavity width are investigated. Compared to existing technologies, that are complex and costly, beam shaping with optical feedback is a more flexible solution to obtain high-quality mid-infrared sources.
TL;DR: It is described how Fourier signal processing techniques can be generalized to partially coherent fields and how spatial filtering in the Fourier plane allows one to tune the coherence properties of the beam.
Abstract: We describe how Fourier signal processing techniques can be generalized to partially coherent fields. Using standard coherence theory, we first show that focusing of a partially coherent beam by a lens modifies its coherence properties. We then consider a 4f imaging system composed of two lenses and discuss how spatial filtering in the Fourier plane allows one to tune the coherence properties of the beam. This, in turn, provides control over the beam’s directionality, spectrum, and degree of polarization.
Posted Content•
TL;DR: Two-color side-view probing of light-matter interaction from minute focal volume of a tightly focused fs-laser pump pulse reveals charge dynamics with high 0.9 μm optical resolution and approximately ~45fs temporal resolution defined by pulse duration.
Abstract: Two-color side-view probing of light-matter interaction from minute focal volume of a tightly focused fs-laser pump pulse reveals charge dynamics with high 0.9 micrometers optical resolution and approximately ~20 fs temporal resolution in coincidence between pump and probe pulses. Use of two colors is advantageous for probing optically excited plasma regions with different density. Holographical digital focusing and spatial filtering were implemented to obtain the same resolution images for subsequent Fourier analysis. Fast electron removal with time constant ~150 fs was resolved and is consistent with self-trapping. Potential applications of an optical control over a light-induced defect placement with deep-sub-wavelength resolution is discussed.
01 Sep 2017
TL;DR: This contribution saw that, spatial filtering through directional antennas leads to a limited number of propagation paths in the channel, and compares narrowband measurements with spatial averaging to traditional broadband channel sounding.
Abstract: We introduce a novel directional channel sounding concept where we sweep a horn antenna around its phase center Directional channel measurements are thus carried out at a fixed coordinate in space To verify our concept, we conducted multi-carrier measurements with 2 GHz of measurement bandwidth The directional broadband channel was sampled uniformly within a cube of three wavelengths side length In this contribution, we compare narrowband measurements with spatial averaging to traditional broadband channel sounding We saw that, spatial filtering through directional antennas leads to a limited number of propagation paths in the channel We show the difference of both approaches and explain the deviation by spatial correlation The spatial correlation is evaluated at several two-dimensional slices We observed wavelength-periodic correlations
TL;DR: A novel framework for a spatial filter design with Fisher’s ratio in feature space directly used as the objective function, which yields improvement in classification performance for both single broadband and filter bank settings compared with conventional nonunified methods.
Abstract: To detect the mental task of interest, spatial filtering has been widely used to enhance the spatial resolution of electroencephalography (EEG). However, the effectiveness of spatial filtering is undermined due to the significant nonstationarity of EEG. Based on regularization, most of the conventional stationary spatial filter design methods address the nonstationarity at the cost of the interclass discrimination. Moreover, spatial filter optimization is inconsistent with feature extraction when EEG covariance matrices could not be jointly diagonalized due to the regularization. In this paper, we propose a novel framework for a spatial filter design. With Fisher’s ratio in feature space directly used as the objective function, the spatial filter optimization is unified with feature extraction. Given its ratio form, the selection of the regularization parameter could be avoided. We evaluate the proposed method on a binary motor imagery data set of 16 subjects, who performed the calibration and test sessions on different days. The experimental results show that the proposed method yields improvement in classification performance for both single broadband and filter bank settings compared with conventional nonunified methods. We also provide a systematic attempt to compare different objective functions in modeling data nonstationarity with simulation studies.
TL;DR: MIT Lincoln Laboratory is developing narrow-beam lasercom for the undersea environment, where a collimated transmit beam is precisely pointed to the receive terminal, where the maximization of light collected at the receiver is achieved.
Abstract: Optical propagation through the ocean encounters significant absorption and scattering; the impact is exponential signal attenuation and temporal broadening, limiting the maximum link range and the achievable data rate, respectively. MIT Lincoln Laboratory is developing narrow-beam lasercom for the undersea environment, where a collimated transmit beam is precisely pointed to the receive terminal. This approach directly contrasts with the more commonly demonstrated approach, where the transmit light is sent over a wide angle, avoiding precise pointing requirements but reducing the achievable range and data rate. Two advantages of narrow-beam lasercom are the maximization of light collected at the receiver and the ability to mitigate the impact of background light by spatial filtering. Precision pointing will be accomplished by bi-directional transmission and tracking loops on each terminal, a methodology used to great effect in atmospheric and space lasercom systems. By solving the pointing and tracking problem, we can extend the link range and increase the data throughput.
TL;DR: In this article, the spatial phase distribution of a femtosecond laser beam was modulated by a phase grating pattern reflecting a transfer function for beam shaping, and the spatial amplitude distribution of the zero-order beam was shaped to top-flat and square.
Abstract: We demonstrated beam shaping to top-flat and square by phase-only Spatial Light Modulator (SLM) and spatial frequency filtering. Spatial phase distribution of a femtosecond laser beam was modulated by a phase grating pattern reflecting a transfer function for beam shaping. By filtering the higher spatial frequency component at Fourier plane in 4f system, the spatial amplitude distribution of the zero-order beam was shaped to top-flat and square. This result enables us to fabricate large area and uniform devices by using multi-shot processing.
TL;DR: In this paper, the authors investigated the quantum image spatial filtering, and focused on the design method of quantum weighted averaging filter and its application in image de-noising, and provided the quantum circuits that implements the filtering task and presented the results of several simulation experiments on some gray images with different noises.
Abstract: In this paper, we investigated the quantum image spatial filtering, and focused on the design method of quantum weighted averaging filter and its application in image de-noising. To this end, we first designed the quantum circuits for some auxiliary modules, such as swapping two numbers, comparing two numbers, computing the weighted average of some integers, etc. Next, we constructed a weighted averaging filter of size 3 × 3 using auxiliary modules. The spatial filtering directly on the image itself can be accomplished by using designed filter. We provided the quantum circuits that implements the filtering task and presented the results of several simulation experiments on some gray images with different noises. The significance of this paper is to explore the quantum realization method of image filtering in spatial domain.
TL;DR: A new selective filtering technique is proposed for the Lattice Boltzmann Method based on an adaptive implementation of the selective filter coefficient that makes the latter coefficient dependent on the shear stress in order to restrict the use of the spatial filtering technique in sheared stress region where numerical instabilities may occur.