scispace - formally typeset
Search or ask a question

Showing papers on "Spatial filter published in 2012"


Journal ArticleDOI
TL;DR: Experimental results for the focal distance, the vortex pattern and the diameter of the focused beam can be made smaller than the size of a comparable Airy beam from a lens are shown.
Abstract: We generate abruptly autofocusing beams that produce vortices at the focus. We give explicit equations for the phase-only Fourier masks that generate these beams including explanations for controlling the focal distance and numerical aperture. We show experimental results for the focal distance, the vortex pattern and show that the diameter of the focused beam can be made smaller than the size of a comparable Airy beam from a lens. Finally we show how to move the focus spot in three dimensions by encoding additional optical elements onto the phase pattern.

92 citations


Journal ArticleDOI
TL;DR: In this article, the experimental realization of these FWs was obtained using a holographic setup for the optical reconstruction of computer generated holograms (CGH), based on a 4-f Fourier filtering system and a nematic liquid crystal spatial light modulator (LC-SLM).
Abstract: Frozen waves (FWs) are very interesting particular cases of nondiffracting beams whose envelopes are static and whose longitudinal intensity patterns can be chosen a priori. We present here for the first time (that we know of) the experimental generation of FWs. The experimental realization of these FWs was obtained using a holographic setup for the optical reconstruction of computer generated holograms (CGH), based on a 4-f Fourier filtering system and a nematic liquid crystal spatial light modulator (LC-SLM), where FW CGHs were first computationally implemented, and later electronically implemented, on the LC-SLM for optical reconstruction. The experimental results are in agreement with the corresponding theoretical analytical solutions and hold excellent prospects for implementation in scientific and technological applications.

89 citations


Journal ArticleDOI
TL;DR: Detailed analysis of the impact and the interplay of various diffraction orders to the formation of Talbot images provides new insights into the fundamental properties of gratings that often find use in applications such as, e.g., lithography, sensing, and imaging.
Abstract: By means of experiment and simulation, we achieve unprecedented insights into the formation of Talbot images to be observed in transmission for light diffracted at wavelength-scale amplitude gratings. Emphasis is put on disclosing the impact and the interplay of various diffraction orders to the formation of Talbot images. They can be manipulated by selective filtering in the Fourier plane. Experiments are performed with a high-resolution interference microscope that measures the amplitude and phase of fields in real-space. Simulations have been performed using rigorous diffraction theory. Specific phase features, such as singularities found in the Talbot images, are discussed. This detailed analysis helps to understand the response of fine gratings. It provides moreover new insights into the fundamental properties of gratings that often find use in applications such as, e.g., lithography, sensing, and imaging.

72 citations


Patent
Katsumi Umeda1, Nobuo Iwatsuki1
31 Dec 2012
TL;DR: In this paper, an information acquiring device includes a laser light source which emits light in a predetermined wavelength region, a projection lens which projects the light from the laser source toward a targeted area, an image sensor which receives reflected light reflected from the targeted area to output a signal, and an imaging lens which guides the reflected light to the image sensor.
Abstract: An information acquiring device includes a laser light source which emits light in a predetermined wavelength region; a projection lens which projects the light from the laser light source toward a targeted area; an image sensor which receives reflected light reflected from the targeted area to output a signal; and an imaging lens which guides the reflected light to the image sensor; a filter which transmits the light from the laser light source; and an actuator which inclines the filter. A filter controlling circuit inclines the filter in such a direction as to approximate a transmissive wavelength region of the filter to the wavelength region of the light from the laser light source.

52 citations


Journal ArticleDOI
TL;DR: In this paper, the authors report on the fabrication and characterization of composite multimode waveguide structures that consist of a stack of single-mode waveguides fabricated by ultrafast laser inscription.
Abstract: We report on the fabrication and characterization of composite multimode waveguide structures that consist of a stack of single-mode waveguides fabricated by ultrafast laser inscription. We explore 2 types of composite structures; those that consist of overlapping single-mode waveguides which offer the maximum effective index contrast and non-overlapped structures which support multiple modes via strong evanescent coupling. We demonstrate that both types of waveguides have negligible propagation losses (to within experimental uncertainty) for light injected with focal ratios >8, which corresponds to the cutoff of the waveguides. We also show that right below cutoff, there is a narrow region where the injected focal ratio is preserved (to within experimental uncertainty) at the output. Finally, we outline the major application of these highly efficient waveguides; in a device that is used to reformat the light in the focal plane of a telescope to a slit, in order to feed a diffraction-limited spectrograph.

52 citations


Journal ArticleDOI
TL;DR: In this article, the authors theoretically considered infrared-driven hyperbolic metamaterials able to spatially filter terahertz (THz) radiation, and numerically proved the device functionality by resorting to full wave simulation coupled to the dynamics of charge carried photoexcited by infrared radiation in semiconductor layers.
Abstract: We theoretically consider infrared-driven hyperbolic metamaterials able to spatially filter terahertz (THz) radiation. The metamaterial is a slab made of alternating semiconductor and dielectric layers whose homogenized uniaxial response, at THz frequencies, shows principal permittivities of different signs. The gap provided by metamaterial hyperbolic dispersion allows the slab to stop spatial frequencies within a bandwidth tunable by changing the infrared radiation intensity. We numerically prove the device functionality by resorting to full wave simulation coupled to the dynamics of charge carries photoexcited by infrared radiation in semiconductor layers.

50 citations


Journal ArticleDOI
TL;DR: This work numerically proves the device functionality by resorting to full wave simulation coupled to the dynamics of charge carries photoexcited by infrared radiation in semiconductor layers.
Abstract: We theoretically consider infrared-driven hyperbolic metamaterials able to spatially filtering terahertz radiation. The metamaterial is a slab made of alternating semiconductor and dielectric layers whose homogenized uniaxial response, at terahertz frequencies, shows principal permittivities of different signs. The gap provided by metamaterial hyperbolic dispersion allows the slab to stop spatial frequencies within a bandwidth tunable by changing the infrared radiation intensity. We numerically prove the device functionality by resorting to full wave simulation coupled to the dynamics of charge carries photoexcited by infrared radiation in semiconductor layers.

44 citations


Journal ArticleDOI
TL;DR: How the angular spectrum of the radiation from a spatially modulated GIM BAS amplifier becomes narrower while propagating and being amplified is demonstrated to demonstrate how the spatial quality of emission of BAS lasers is improved.
Abstract: We propose and analyze a beam-shaping mechanism that in broad-area semiconductor amplifiers occurs due to spatial pump modulation on a micrometer scale. The study, performed under realistic parameters and conditions, predicts a spatial (angular) filtering of the radiation, which leads to a substantial improvement of the spatial quality of the beam during amplification. Quantitative analysis of spatial filtering performance is presented based on numerical integration of the paraxial propagation model and on analytical estimations.

44 citations


Journal ArticleDOI
TL;DR: In this paper, a novel spatial filtering velocimeter for solid particle velocity measurement in gas-solid flow system is presented based on a Linear Electrostatic Sensor Array (LESA) in which a differential filter based on two LESAs is further proposed to remove the pedestal component of the output signal from the LESA.

43 citations


Journal ArticleDOI
TL;DR: The fabrication and characterization of straight dielectric-loaded surface plasmon polaritons waveguides doped with lead-sulfide quantum dots as a near infra-red gain medium is reported on.
Abstract: We report on the fabrication and characterization of straight dielectric-loaded surface plasmon polaritons waveguides doped with lead-sulfide quantum dots as a near infra-red gain medium. A loss compensation of ~33% (an optical gain of ~143 cm⁻¹) was observed in the guided mode. The mode propagation, coupling efficiency and stimulated emission were characterized using leakage radiation microscopy. The guided mode signature was separated using spatial filters in the Fourier plane of the microscope for quantitative measurements of stimulated emission.

42 citations


Journal ArticleDOI
TL;DR: In this paper, the scintillation index for a Gaussian beam wave propagation through non-Kolmogorov turbulent atmosphere is derived in strong fluctuation regime, using non-kinetic spectrum with a generalized power law exponent and the extended Rytov theory with a modified spatial filter function.

Journal ArticleDOI
TL;DR: In this paper, the effects of spatial filtering on the streamwise spectrum function of wall-bounded flows were investigated using a grid-generated turbulence as a benchmark flow, and it was shown that spatial filtering significantly attenuates the attenuation of the Reynolds stress due to spatial filtering.
Abstract: We use grid-generated turbulence as a benchmark flow to test the effects of spatial resolution on turbulence measurements with hot wires. To quantify the spatial filtering, measurements of the turbulence statistics and spectra downstream of the grid were made using hot wires of varying length and compared to the results from a new nanoscale thermal anemometry probe, which has a sensing length of the order of, or smaller than, the Kolmogorov scale. In order to separate the effects of temporal and spatial filtering, a study was performed to ensure that the data were free of the artifacts of temporal filtering so that differences in the measurements could be wholly attributed to spatial filtering. An empirical correlation for the attenuation of the streamwise Reynolds stress due to spatial filtering is constructed, and it is shown that these grid turbulence results relate directly to the near-wall region of wall-bounded flows, where the effects of spatial filtering are most acutely felt. The effect of spatial filtering on the streamwise spectrum function is observed to extend to almost all wavenumbers, even those significantly lower than the length of the hot wire itself. It is also shown that estimates of the Kolmogorov scale are affected by spatial filtering when wires longer than the Kolmogorov length are used.

Journal ArticleDOI
TL;DR: This study uses a Bessel-like beam in-conjugation with an orthogonal detection system to achieve depth imaging and demonstrates a penetration depth that extends up to 650 µm, which will advance the field of fluorescence imaging and deep nano-particle tracking.
Abstract: Monitoring and visualizing specimens at a large penetration depth is a challenge. At depths of hundreds of microns, several physical effects (such as, scattering, PSF distortion and noise) deteriorate the image quality and prohibit a detailed study of key biological phenomena. In this study, we use a Bessel-like beam in-conjugation with an orthogonal detection system to achieve depth imaging. A Bessel-like penetrating diffractionless beam is generated by engineering the back-aperture of the excitation objective. The proposed excitation scheme allows continuous scanning by simply translating the detection PSF. This type of imaging system is beneficial for obtaining depth information from any desired specimen layer, including nano-particle tracking in thick tissue. As demonstrated by imaging the fluorescent polymer-tagged-CaCO3 particles and yeast cells in a tissue-like gel-matrix, the system offers a penetration depth that extends up to 650 mu m. This achievement will advance the field of fluorescence imaging and deep nano-particle tracking.

Journal ArticleDOI
TL;DR: An active imaging, snapshot, system design and postprocessing algorithms that differentiate between radiation that scatters or reflects from remote, obscured objects and the radiation from the scattering media itself through a combination of polarization difference imaging, channel blurring, and Fourier spatial filtering are developed.
Abstract: Conventional intensity imaging through turbid media suffers from rapid loss of image contrast due to light scattering from particles or random variations of refractive index. This paper features the development of an active imaging, snapshot, system design and postprocessing algorithms that differentiate between radiation that scatters or reflects from remote, obscured objects and the radiation from the scattering media itself through a combination of polarization difference imaging, channel blurring, and Fourier spatial filtering. The produced sensor acquires and processes image data in real time, yielding improved image contrasts by factors of 10 or greater for dense water vapor obscurants.

Journal ArticleDOI
TL;DR: Some representative and recent filtering methods for electronic speckle pattern interferometry (ESPI) fringe or wrapped phase patterns, mainly including the second-order oriented partial differential equations (PDEs) filtering methods (SOOPDE), the oriented, regularized quadratic cost function (ORQCF) method, the oriented spatial filter masks (OSFM), the windowed Fourier transform method (WFF), and the localized Fouriertransform filter (LFF).

Journal ArticleDOI
TL;DR: In this article, the authors proposed and numerically demonstrated the feasibility of spatial filtering, i.e., a selective removal of the high spatial frequency components, of narrow acoustic beams during their propagation along a two-dimensional sonic crystal.

Journal ArticleDOI
Juanjuan Zheng1, Yanlong Yang1, Ming Lei1, Baoli Yao1, Peng Gao1, Tong Ye1 
TL;DR: A slice-by-slice diffraction propagation model in the frame of the angular spectrum method is proposed to simulate the whole imaging process of TPFVI and reveals that the Bessel beam can penetrate deep in scattering media due to its self-reconstruction ability.
Abstract: In a two-photon excitation fluorescence volume imaging (TPFVI) system, an axicon is used to generate a Bessel beam and at the same time to collect the generated fluorescence to achieve large depth of field. A slice-by-slice diffraction propagation model in the frame of the angular spectrum method is proposed to simulate the whole imaging process of TPFVI. The simulation reveals that the Bessel beam can penetrate deep in scattering media due to its self-reconstruction ability. The simulation also demonstrates that TPFVI can image a volume of interest in a single raster scan. Two-photon excitation is crucial to eliminate the signals that are generated by the side lobes of Bessel beams; the unwanted signals may be further suppressed by placing a spatial filter in the front of the detector. The simulation method will guide the system design in improving the performance of a TPFVI system.

Journal ArticleDOI
TL;DR: A new beam-forming system for generating high intensity programmable optical spikes using so-called matched-filtering Generalized Phase Contrast (mGPC) applying two consumer handheld pico-projectors, presenting a low-cost alternative for optical trapping and manipulation, optical lattices and other beam-shaping applications usually implemented with high-end spatial light modulators.
Abstract: We report on a new beam-forming system for generating high intensity programmable optical spikes using so-called matched-filtering Generalized Phase Contrast (mGPC) applying two consumer handheld pico-projectors. Such a system presents a low-cost alternative for optical trapping and manipulation, optical lattices and other beam-shaping applications usually implemented with high-end spatial light modulators. Portable pico-projectors based on liquid crystal on silicon (LCoS) devices are used as binary phase-only spatial light modulators by carefully setting the appropriate polarization of the laser illumination. The devices are subsequently placed into the object and Fourier plane of a standard 4f-setup according to the mGPC spatial filtering configuration. Having a reconfigurable spatial phase filter, instead of a fixed and fabricated one, allows the beam shaper to adapt to different input phase patterns suited for different requirements. Despite imperfections in these consumer pico-projectors, the mGPC approach tolerates phase aberrations that would have otherwise been hard to overcome by standard phase projection.

Journal ArticleDOI
Hao Bengong1, Mingguang Shan1, Diao Ming1, Zhi Zhong1, Hongwen Ma1 
TL;DR: A common-path interferometer with a tri-window built using a 4f optical system with Ronchi ruling as a spatial filter and reconstructed from the three patterns using just one interferogram is proposed.
Abstract: A common-path interferometer is proposed with a tri-window. It is built using a 4f optical system with Ronchi ruling as a spatial filter. The input rectangular aperture is formed by three windows; the central window supports a phase object, and the other two are used for reference beams. Using an appropriate grating period relative to input aperture size, an interferogram containing three patterns can be obtained in the output plane. The object phase can then be reconstructed from the three patterns using just one interferogram. The experiments are carried out to demonstrate the feasibility and reliability of the proposed scheme.

Journal ArticleDOI
TL;DR: It is demonstrated how low-light-level, non-laser sources enable holographic imaging with a video frame rate, an intermediate SNR of 8 dB, and a volume of coherence of 3.4×10(4) μm3.
Abstract: The light of a light-emitting diode or a common thermal source, such as a tungsten filament lamp, is known to be quasi-incoherent. We generated partially coherent light of these sources with a volume of coherence in the micrometer range of 5-100 μm3 by spatial and spectral filtering. The corresponding degree of partial coherence was adapted for microscopic interference setups, such as a digital in-line holographic microscope. The practicability of the sources was determined by the spectral emittance and the resulting signal-to-noise ratio (SNR) of the detector. The microscale coherence in correlation with the SNR and its resolution for microscopy were analyzed. We demonstrate how low-light-level, non-laser sources enable holographic imaging with a video frame rate (25 frames/s), an intermediate SNR of 8 dB, and a volume of coherence of 3.4×10(4) μm3. Holograms of objects with a lateral resolution of 1 μm were achieved using a microscope lens (50×/NA=0.7) and a CCD camera featuring a 4-12 bit dynamic range.

Patent
22 Oct 2012
TL;DR: In this paper, a defect signal which is small enough to be buried in a background noise was detected by a method that includes detecting a defect on a specimen which is detected by another inspection device by using a detection device equipped with an optical microscope, amending positional information of the defect, observing the defect by using an SEM, wherein the detecting the defect is carried out such that forming stationary waves on the specimen by irradiating the specimen with two illumination lights having the same wavelength from opposite directions on the same incidence plane at the same angle and cause the two illuminating light to interfere.
Abstract: The present invention is detection of a defect signal which is small enough to be buried in a background noise, by a method that includes detecting a defect on a specimen which is detected by another inspection device by using a detection device equipped with an optical microscope, amending positional information of the defect, observing the defect by using an SEM, wherein the detecting the defect is carried out such that forming stationary waves on the specimen by irradiating the specimen with two illumination lights having the same wavelength from the opposite directions on the same incidence plane at the same incidence angle and cause the two illuminating light to interfere; removing scattered components generated by minute irregularities on the specimen surface by a spatial filter, detecting an image formed by the scattered light not removed by the spatial filter; and processing the detected image to detect the defect.

Patent
04 Jan 2012
TL;DR: In this paper, the authors proposed a method and a device for simultaneously measuring droplet positions, particle sizes and a complex refractive index, which consists of dividing a highly coherent continuous laser beam into two beams after spatial filtering and collimating beam expansion, wherein one beam radiates particles in a detected flow field region, and the other beam is used as a reference beam.
Abstract: The invention relates to technology for simultaneously measuring multi-phase flow particles online through multi-parameter, and aims to provide a method and a device for simultaneously measuring droplet positions, particle sizes and a complex refractive index. The method comprises the following steps of: (1) dividing a highly coherent continuous laser beam into two beams after spatial filtering and collimating beam expansion, wherein one beam radiates particles in a detected flow field region, and the other beam is used as a reference beam; (2) mixing scattered light of a lateral 30-degree to90-degree region of particles in the detected flow field region and the attenuated reference beam to perform interference so as to form a hologram, storing the hologram in a computer after being recorded by a digital camera through an imaging device; (3) acquiring a series of reconstructed images of the detected particles along the depth direction by utilizing digital reconstruction technology; and (4) identifying the reflective spot and the refractive spot of the particles from the reconstructed images by utilizing digital image processing technology so as to acquire space coordinates and scattered light intensity ratios. Compared with rainbow measurement technology, the measurement method has the advantages that: a light path system of the measurement device is relatively simple and is easy to implement.

Journal ArticleDOI
TL;DR: A digital holography microscopy technique based on parallel-quadrature phase-shifting method that eliminates phase errors caused by mechanical vibrations and air turbulences and allows a much larger dimension of the spatial filter for reconstruction of the object information.

Patent
04 Jul 2012
TL;DR: In this article, a linear multi-wavelength confocal microscopy module with a linear scanning confocal principle and a light source dispersion technique was used to develop a long-field-depth high-definition optical micro-morphological profile microscopic method and a system by using a confocal microscopic technique withoptical sectioning capacity and in combination with the high definition of spectral dispersion.
Abstract: The invention provides a linear multi-wavelength confocal microscopic system, which uses more than two chromatic lenses to enable a linear incident light field to generate dispersed rays and to enable rays with different wavelengths to be focused at different positions. Moreover, the invention utilizes a linear multi-wavelength confocal microscope module with a linear scanning confocal principle and a light source dispersion technique to develop a long-field-depth high-definition optical micro-morphological profile microscopic method and a system by using a confocal microscopic technique withoptical sectioning capacity and in combination with the high definition of spectral dispersion. The method and the system of the invention use a broadband light source. By adopting a dispersion objective module, the broadband light source is enabled to generate axially dispersed rays which are focused at different depths, the focused surface reflectance spectrum is obtained simultaneously, spatial filtering is conducted through a slit, the peak position of a spectral focusing response curve is accurately sensed by a linear spectral image sensing unit and thereby sectional profile measurement can be finished accurately and rapidly.

Journal ArticleDOI
TL;DR: In this paper, the authors used high-speed Nipkow spinning disk confocal microscopy to measure 3D3C velocity fields in microscopic volumes, using a piezo objective positioner.
Abstract: We present a diagnostic platform for measuring three-dimensional three-component (3D3C) velocity fields in microscopic volumes. The imaging system uses high-speed Nipkow spinning disk confocal microscopy. Confocal microscopy provides optical sectioning using pinhole spatial filtering which rejects light originating from out-of-focus objects. The system accomplishes volumetric scanning by rapid translation of the high numerical aperture objective using a piezo objective positioner. The motion of fluorescent microspheres is quantified using 3D3C super resolution particle-imaging velocimetry with instantaneous spatial resolutions of the order of 5 µm or less in all three dimensions. We examine 3D3C flow in a PDMS microchannel with an expanding section at 3D acquisition rates of 30 Hz, and find strong agreement with a computational model. Equations from the PIV and PTV literature adapted for a scanning objective provide estimates of maximum measurable velocity. The technique allows for isosurface visualization of 3D particle motion and robust high spatial resolution velocity measurements without requiring a calibration step or reconstruction algorithms.

Patent
04 Jan 2012
TL;DR: In this article, a device for generating rotary compound vortex light beams is proposed, which is characterized by a light source emerged by a laser light source sequentially pass through a light beam amplifier and a beam splitting mirror.
Abstract: The utility model relates to a device for generating rotary compound vortex light beams, which is technically characterized in that light beams emerged by a laser light source sequentially pass through a light beam amplifier and a beam splitting mirror, one light beam of the two light beams processed by beam splitting is modulated by a first spatial light modulator after the light beam passes through a second half-transmitting half-reflecting mirror, and then the light beam is filtered by a first Fourier spatial filter; the other light beam is modulated by a second spatial light modulator after the light beam is reflected by a first half-transmitting half-reflecting mirror, then the light beam is filtered by a second Fourier spatial filter, and frequency shift is generated by a frequency shifting component; and the coaxial superposition of two beams of light is realized by a beam combining mirror so as to obtain and generate the rotary compound vortex light beams According to the device provided by the utility model, the rotating speeds and the speckle patterns of the compound vortex light beams can be conveniently controlled; and the light beams generated by using the device for generating the rotary compound vortex light beams can be used as an optical wrench, and particles are operated and rotated by the specific orbital angular momentum characteristic of the optical wrench

Journal ArticleDOI
TL;DR: A novel closed-loop approach for high-precision co-alignment of laser beams in an actively phase-locked, coherently combined fiber laser array is demonstrated, ensuring interferometric precision by optically transducing beam-to-beam pointing errors into phase errors on a single detector.
Abstract: We demonstrate a novel closed-loop approach for high-precision co-alignment of laser beams in an actively phase-locked, coherently combined fiber laser array. The approach ensures interferometric precision by optically transducing beam-to-beam pointing errors into phase errors on a single detector, which are subsequently nulled by duplication of closed-loop phasing controls. Using this approach, beams from five coherent fiber tips were simultaneously phase-locked and position-locked with sub-micron accuracy. Spatial filtering of the sensed light is shown to extend the control range over multiple beam diameters by recovering spatial coherence despite the lack of far-field beam overlap.

Journal ArticleDOI
TL;DR: Simulation results indicate that the use of proposed full‐spectrum imaging technique may result in three times improvement in signal dynamic range compared to that can be achieved in the filter‐based imaging.
Abstract: We implement a filterless illumination scheme on a hyperspectral fluorescence microscope to achieve full-range spectral imaging. The microscope employs polarisation filtering, spatial filtering and spectral unmixing filtering to replace the role of traditional filters. Quantitative comparisons between full-spectrum and filter-based microscopy are provided in the context of signal dynamic range and accuracy of measured fluorophores’ emission spectra. To show potential applications, a five-colour cell immunofluorescence imaging experiment is theoretically simulated. Simulation results indicate that the use of proposed full-spectrum imaging technique may result in three times improvement in signal dynamic range compared to that can be achieved in the filter-based imaging.

Journal ArticleDOI
TL;DR: Two techniques to improve the quality of reconstructed optical projection tomography (OPT) images using the modulation transfer function (MTF) as a function of defocus experimentally determined from tilted knife-edge measurements are demonstrated.
Abstract: We demonstrate two techniques to improve the quality of reconstructed optical projection tomography (OPT) images using the modulation transfer function (MTF) as a function of defocus experimentally determined from tilted knife-edge measurements. The first employs a 2-D binary filter based on the MTF frequency cut-off as an additional filter during back-projection reconstruction that restricts the high frequency information to the region around the focal plane and progressively decreases the spatial frequency bandwidth with defocus. This helps to suppress “streak” artifacts in OPT data acquired at reduced angular sampling, thereby facilitating faster OPT acquisitions. This method is shown to reduce the average background by approximately 72% for an NA of 0.09 and by approximately 38% for an NA of 0.07 compared to standard filtered back-projection. As a biological illustration, a Fli:GFP transgenic zebrafish embryo (3 days post-fertilisation) was imaged to demonstrate the improved imaging speed (a quarter of the acquisition time). The second method uses the MTF to produce an appropriate deconvolution filter that can be used to correct for the spatial frequency modulation applied by the imaging system.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a spatial filter velocimetry (SFV) based on a frequency analysis of time-series spatially filtered particle images, which can measure velocity from one particle in a measurement region, it enables us to measure the velocity with high accuracy and high spatial resolution.
Abstract: High accuracy and high spatial resolution are required in measurements of fluid velocity for detailed flow diagnostics. In this study, we proposed spatial filter velocimetry (SFV) based on a frequency analysis of time-series spatially filtered particle images. Since this method can measure velocity from one particle in a measurement region, it enables us to measure the velocity with high accuracy and high spatial resolution. We developed a SFV system and applied it to laminar and turbulent flows in a duct to examine its performance. Comparisons between the velocities measured by SFV and LDV confirmed that SFV accurately measures the mean velocity and turbulent intensity with spatial and temporal resolutions as high as LDV.