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Analysis of the optical quality by determining the modulation transfer function for anterior corneal surface in myopes 认领 引用 被引量：6
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作者 Yan-Zhen Zheng Yan-Peng Chen +2 位作者 Yan Qiu Guo-Guang Zhai Yao-Yu Li 《International Journal of Ophthalmology(English edition)》 SCIE CAS 2012年第2期196-201,共6页
AIM:To describe the characteristics of modulation transfer function(MTF)of anterior corneal surface,and obtain the the normal reference range of MTF at different spatial frequencies and optical zones of the anterior c... AIM:To describe the characteristics of modulation transfer function(MTF)of anterior corneal surface,and obtain the the normal reference range of MTF at different spatial frequencies and optical zones of the anterior corneal surface in myopes.METHODS:Four hundred eyes from 200 patients were examined under SIRIUS corneal topography system.Phoenis analysis software was applied to simulate the MTF curves of anterior corneal surface at vertical and horizontal meridians at the 3,4,5,6,7mm optical zones of cornea.The MTF values at spatial frequencies of 5,10,15,20,25,30,35,40,45,50,55 and 60 cycles/degree(c/d)were selected.RESULTS:The MTF curve of anterior corneal surface decreased rapidly from low to intermediate frequency(0-15cpd)at various optical zones of cornea,the value decreased to 0 slowly at higher frequency(>15cpd).With the increase of the optical zones of cornea,MTF curve decreased gradually.3)In the range of 3 mm-6 mm optical zones of the cornea,the MTF values measured at horizontal meridian were greater than the corresponding values at horizontal meridian of each spatial frequency,the difference was statistically significant(P<0.05).At 7 mm optical zones of cornea,the MTF values measured at horizontal meridian were less than the corresponding values at vertical meridian at 10-60 spatial frequencies(cpd),and the difference was statistically significant in 25,30,35,40,45,50 cpd(P<0.05).CONCLUSION:MTF can be used to describe the imaging quality of optical systems at anterior corneal surface objectively in detail. 展开更多
关键词 modulation transfer function optical quality cornea point spread function optical transfer function phase transfer function
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A new modulation transfer function for ocean wave spectra retrieval from X-band marine radar imagery 认领 引用 被引量：4
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作者 陈忠彪 张彪 +2 位作者 何宜军 丘仲锋 PERRIE William 《Chinese Journal of Oceanology and Limnology》 CSCD 2015年第5期1132-1141,共10页
When imaging ocean surface waves by X-band marine radar, the radar backscatter from the sea surface is modulated by the long surface gravity waves. The modulation transfer function （MTF） comprises tilt, hydrodynamic... When imaging ocean surface waves by X-band marine radar, the radar backscatter from the sea surface is modulated by the long surface gravity waves. The modulation transfer function （MTF） comprises tilt, hydrodynamic, and shadowing modulations. A conventional linear MTF was derived using HH-polarized radar observations under conditions of deep water. In this study, we propose a new quadratic polynomial MTF based on W-polarized radar measurements taken from heterogeneous nearshore wave fields. This new MTF is obtained using a radar-observed image spectrum and in situ buoy-measured wave frequency spectrum. We validate the MTF by comparing peak and mean wave periods retrieved from X-band marine radar image sequences with those measured by the buoy. It is shown that the retrieval accuracies of peak and mean wave periods of the new MTF are better than the conventional MTF. The results also show that the bias and root mean square errors of the peak and mean wave periods of the new MTF are 0.05 and 0.88 s, and 0.32 and 0.53 s, respectively, while those of the conventional MTF are 0.61 and 0.98 s, and 1.39 and 1.48 s, respectively. Moreover, it is also shown that the retrieval results are insensitive to the coefficients in the proposed MTF. 展开更多
关键词 X-band marine radar modulation transfer function ocean wave spectra
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Modulation transfer function characteristic of uniform-doping transmission-mode GaAs/GaAlAs photocathode 认领 引用 被引量：3
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作者 任玲 常本康 《Chinese Physics B》 SCIE EI CAS CSCD 2011年第8期398-402,共5页
The resolution characteristic can be obtained by the modulation transfer function （MTF） of a GaAs/GaA1As photocathode. After establishing the theoretical model of GaAs（100）-oriented atomic configuration and the fo... The resolution characteristic can be obtained by the modulation transfer function （MTF） of a GaAs/GaA1As photocathode. After establishing the theoretical model of GaAs（100）-oriented atomic configuration and the formula for the ionized impurity scattering of the non-equilibrium carriers, this paper calculates the trajectories of photoelectrons in a photocathode. Thus the distribution of photoelectron spots on the emit-face is obtained, which is namely the point spread function. The MTF is obtained by Fourier transfer of the line spread function obtained from the point spread function. The MTF obtained from these calculations is shown to depend heavily on the electron diffusion length, and enhanced considerably by decreasing the electron diffusion length and increasing the doping concentration. Furthermore, the resolution is enhanced considerably by increasing the active-layer thickness, especially at high spatial frequencies. The best spatial resolution is 860 lp/mm, for the GaAs photocathode of doping concentration 1 ×10^19 cm 3 electron diffusion length 3.6 μm and the active-layer thickness 2 μm, under the 633-nm light irradiated. This research will contribute to the future improvement of the cathode＇s resolution for preparing a high performance GaAs photocathode, and improve the resolution of a low light level image intensifier. 展开更多
关键词 GaAs/GaAlAs photocathode uniform-doping modulation transfer function spatial res-olution
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Comparison of the retinal modulation transfer function between amblyopes successfully corrected and normal subjects 认领 引用
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作者 Xiao-Ming Huang Xue-Gu Xu Guo-Xing Xu 《International Journal of Ophthalmology(English edition)》 SCIE CAS 2011年第3期284-285,共2页
AIM:To analyze the retinal modulation transfer function between amblyopes whose visual acuity was corrected to 5.0 and normal subjects at the same age.METHODS:RM-800 used to detect contrast sensitivity was adopted to ... AIM:To analyze the retinal modulation transfer function between amblyopes whose visual acuity was corrected to 5.0 and normal subjects at the same age.METHODS:RM-800 used to detect contrast sensitivity was adopted to measure MTF of 96 amblyopes(96 eyes)whose visual acuity was corrected to 5.0 and 80 normal controls(80 eyes)at the same age under six interference fringes(IVA=0.06,0.1,0.2,0.4,0.6,0.8).RESULTS:The functional values of amblyopes were significantly lower than those of normal subjects in every fringe(P<0.01),especially in medium and high frequency.CONCLUSION:For amblyopes,MTF was still abnormal after stopping the treatments. 展开更多
关键词 modulation transfer function amblyope Interference Fringe Visual Acuity
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Fuzzy image restoration using modulation transfer function 认领 引用
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作者 袁媛 Yi Yaohua Liu Juhua 《High Technology Letters》 EI CAS 2016年第4期461-469,共9页
The key difficulty of restoring a fuzzy image is to estimate its point spread function( PSF). In the paper,PSF is modelled based on modulation transfer function( MTF). The first step is calculating the image MTF. In t... The key difficulty of restoring a fuzzy image is to estimate its point spread function( PSF). In the paper,PSF is modelled based on modulation transfer function( MTF). The first step is calculating the image MTF. In the traditional slanted-edge method,a sub-block is always manually extracted from original image and its MTF will be viewed as the result of the whole image. However,handcraft extraction is inefficient and will lead to inaccurate results. Given this,an automatic MTF computation algorithm is proposed,which extracts and screens out all the effective sub-blocks and calculates their average MTF as the final result. Then,a two-dimensional MTF restoration model is constructed by multiplying the horizontal and vertical MTF,and it is combined with conventional image restoration methods to restore fuzzy image. Experimental results indicate the proposed method implementes a fast and accurate MTF computation and the MTF model improves the performance of conventional restoration methods significantly. 展开更多
关键词 fuzzy image modulation transfer function(MTF) slanted-edge method automatic computation MTF restoration model
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Comparison of ocular modulation transfer function determined by a ray-tracing aberrometer and a double-pass system in early cataract patients 认领 引用 被引量：3
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作者 Qiao Liya Wan Xiuhua +6 位作者 Cai Xiaogu Balamurali Vasudevan Xiong Ying Tan Jiaxuan Guan Zheng David A Atchison Wang Ningli 《Chinese Medical Journal》 SCIE CAS CSCD 2014年第19期3454-3458,共5页
Background The evaluation of retinal image quality in cataract eyes has gained importance and the clinical modulation transfer functions （MTF） can obtained by aberrometer and double pass （DP） system. This study ai... Background The evaluation of retinal image quality in cataract eyes has gained importance and the clinical modulation transfer functions （MTF） can obtained by aberrometer and double pass （DP） system. This study aimed to compare MTF derived from a ray tracing aberrometer and a DP system in early cataractous and normal eyes. Methods There were 128 subjects with 61 control eyes and 67 eyes with early cataract defined according to the Lens Opacities Classification System II1. A laser ray-tracing wavefront aberrometer （iTrace） and a double pass （DP） system （OQAS） assessed ocular MTF for 6.0 mm pupil diameters following dilation. Areas under the MTF （AUMTF） and their correlations were analyzed. Stepwise multiple regression analysis assessed factors affecting the differences between iTrace- and OQAS-derived AUMTF for the early cataract group. Results For both early cataract and control groups, iTrace-derived MTFs were higher than OQAS-derived MTFs across a range of spatial frequencies （P 〈0.01）. No significant difference between the two groups occurred for iTrace-derived AUMTF, but the early cataract group had significantly smaller OQAS-derived AUMTF than did the control group （P 〈0.01）. AUMTF determined from both the techniques demonstrated significant correlations with nuclear opacities, higher-order aberrations （HOAs）, visual acuity, and contrast sensitivity functions, while the OQAS-derived AUMTF also demonstrated significant correlations with age and cortical opacity grade. The factors significantly affecting the difference between iTrace and OQAS AUMTF were root-mean-squared HOAs （standardized beta coefficient=-0.63, P 〈0.01） and age （standardized beta coefficient=0.26, P 〈0.01）. Conclusions MTFs determined from a iTrace and a DP system （OQAS） differ significantly in early cataractous and normal subjects. Correlations with visual performance were higher for the DP system. OQAS-derived MTF may be useful as an indicator of visual performance in early cataract eyes. 展开更多
关键词 cataract contrast sensitivity function double-pass system modulation transfer function retinal image quality,＂ wavefront aberration
Solving the atmospheric scattering optical transfer function using the multi-coupled single scattering method 认领 引用 被引量：2
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作者 孙斌 洪津 孙晓兵 《Chinese Physics B》 SCIE EI CAS CSCD 2014年第9期200-204,共5页
The atmospheric scattering optical transfer function （OTF） is solved by applying the multi-coupled single scattering （MCSS） method to the three-dimensional radiative transfer equation （RTE） under the periodic gr... The atmospheric scattering optical transfer function （OTF） is solved by applying the multi-coupled single scattering （MCSS） method to the three-dimensional radiative transfer equation （RTE） under the periodic ground condition. This approach is a direct hit to the atmospheric scattering OTF using the same original context of modulation transfer function （MTF） measurement, i.e., images of sinusoidal grating at different spatial frequencies. Both the amplitude and phase shift of the OTF at various zenith and azimuth angles can be obtained at an arbitrary spatial frequency. 展开更多
关键词 atmospheric scattering optical transfer function modulation transfer function multi-coupled single scattering method
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Changes of pupil parameters and visual quality after cataract surgery as well as their correlation 认领 引用
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作者 Fan Yang Jie Xu +2 位作者 Pei-Min Lin Ming-Yang Wang Tian-Yu Zheng 《International Journal of Ophthalmology(English edition)》 SCIE CAS 2026年第8期1518-1525,共8页
●AIM:To compare the changes of pupil parameters and visual quality after cataract surgery and explore their potential correlations.●METHODS:This retrospective cohort study analyzed clinical data of Han Chinese patie... ●AIM:To compare the changes of pupil parameters and visual quality after cataract surgery and explore their potential correlations.●METHODS:This retrospective cohort study analyzed clinical data of Han Chinese patients who received cataract surgery from June 2016 to October 2016.Visual acuity,pupil size,pupil shift,wavefront aberrations,point spread function(PSF),and modulation transfer function(MTF)were detected preoperatively,1d and 1mo postoperatively.Pupil parameters and visual outcomes were compared across the three time points.●RESULTS:A total of 110 eyes from 110 patients(42 males and 68 females)were enrolled,with a mean age of 66.8±7.9y(range:53–88y).Under both photopic and mesopic conditions,pupil diameter and pupil shift at 1d and 1mo after surgery were significantly lower than baseline levels.Corneal aberrations decreased postoperatively.Photopic and mesopic modulation transfer function derived from higher-order(HO)aberrations increased significantly from postoperative day 1 to postoperative month 1.Pupil size was positively correlated with wavefront aberrations,and negatively correlated with total PSF and HO-PSF.Significant correlations were identified between preoperative pupil diameter and 1-month postoperative visual quality indicators(including aberrations,PSF and modulation transfer function).A preoperative mesopic pupil diameter over 5.60 mm effectively predicted poor 1-month postoperative visual quality(HO aberrations>0.5μm),with an area under the curve(AUC)of 0.71.●CONCLUSION:Pupil parameters and visual quality alter significantly after cataract surgery,and moderate correlations exist between pupil diameter and visual quality at each time point.Preoperative pupil diameter is correlated with 1-month postoperative visual quality. 展开更多
关键词 a b e r r a t i o n s c a t a r a c t s u r g e r y modulation transfer function point spread function pupil diameter
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A Wave Modulation Model of Ripples over Long Surface Waves 认领 引用
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作者 CONG Peixiu ZHENG Guizhen 《Journal of Ocean University of China》 CAS 2011年第2期122-126,共5页
A study is presented on the modulation of ripples induced by a long surface wave (LW) and a new theoretical modula-tion model is proposed. In this model, the wind surface stress modulation is related to the modulation... A study is presented on the modulation of ripples induced by a long surface wave (LW) and a new theoretical modula-tion model is proposed. In this model, the wind surface stress modulation is related to the modulation of ripple spectrum. The model results show that in the case of LW propagating in the wind direction with the wave age parameter of LW increasing, the area with enhanced shear stress shifts from the region near the LW crest on the upwind slope to the LW trough. With a smaller wave age parameter of LW, the ripple modulation has the maximum on the upwind slope in the vicinity of LW crest, while with a larger parameter the enhancement of ripple spectrum does not occur in that region. At low winds the amplitude of ripple modulation transfer function (MTF) is larger in the gravity wave range, while at moderate or high winds it changes little in the range from short gravity waves to capillary waves. 展开更多
关键词 ocean waves ripples wave modulation modulation transfer function wind stress wave spectrum
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Relationship between angle kappa,angle alpha and objective visual quality in patients with multifocal intraocular lens 认领 引用
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作者 Zhu Chaojie Long Tan +2 位作者 Ma Ting Yan Jie Wang Rui 《国际眼科杂志》 CAS 2025年第9期1399-1405,共7页
AIM:To investigate how angles kappa and alpha affect postoperative visual quality in patients with multifocal intraocular lens(mIOLs)implantation.METHODS:Retrospective cases series.A total of 46 patients(46 eyes)who u... AIM:To investigate how angles kappa and alpha affect postoperative visual quality in patients with multifocal intraocular lens(mIOLs)implantation.METHODS:Retrospective cases series.A total of 46 patients(46 eyes)who underwent phacoemulsification were subsumed.The correlation between Preoperative angles kappa and alpha,wave-front aberrations and objective visual quality of cornea,internal,and total eye after surgery were analyzed using iTrace.RESULTS:The magnitude of angle kappa was negatively correlated with internal and total modulation transfer function(MTF)at 3 mm;the magnitude of angle kappa was positively correlated with astigmatism,trefoil,higher-order aberrations(HOAs)of both internal and total eye at 3 mm.The magnitude of angle alpha was negatively correlated with total MTF and total Strehl ratio at 3 mm.The magnitude of angle alpha was positively correlated with corneal coma at 5 mm,internal astigmatism at both 3 mm and 5 mm,and total spherical aberration(SA)at 3 mm.Multivariate linear regression analysis showed that,among candidate independent variables(kappa,alpha,astigmatism,SA,coma,trefoil,and HOAs),astigmatism is the only independent factor for altering corneal MTF at 3 mm and 5 mm;astigmatism and HOAs emerged as independent factors for altering internal MTF at 3 mm and 5 mm,and total MTF at 3 mm;astigmatism,SA and HOAs emerged as independent factors for altering total MTF at 5 mm.CONCLUSION:With greater preoperative angle kappa or angle alpha,patients who accept mIOL implantation tend to have larger internal astigmatism and HOAs,which resulting in poor visual quality,especially those with small pupil size. 展开更多
关键词 angle kappa angle alpha modulation transfer function cataract Strehl ratio
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Design and implementation of an integrated and rapidly assembled infrared three-band optical system 认领 引用
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作者 Shuanglong Tan Yulin Wang +3 位作者 Guangwei Shi Shuaiwei Mu Xin Zhang Lin Ma 《Astronomical Techniques and Instruments》 CSCD 2025年第2期88-99,共12页
Continuing advancement in astronomy,space exploration,and scientific detection,has increased demand for infrared multi-band detection systems.Traditional three-band optical systems,designed to simultaneously image at ... Continuing advancement in astronomy,space exploration,and scientific detection,has increased demand for infrared multi-band detection systems.Traditional three-band optical systems,designed to simultaneously image at infrared short-wave,mid-wave,and long-wave bands typically rely on dispersive elements,leading to bulky sizes,complex system architectures,low efficiency,and challenges in rapid assembly.To overcome these obstacles,in combination with the latest third-generation infrared detectors,we propose a design for a compact and lightweight three-band optical system,with infrared capabilities in all three required bands.The core of this approach is an integrated design philosophy that emphasizes the high steepness of mirror surfaces.This design achieves uniform correction and optimization of chromatic aberration and off-axis aberration across the spectral range.We introduce a novel integration of optical and mechanical elements to replace traditional assembly,reducing manufacturing and assembly errors,and degrees of freedom,associated with high-power optical elements.Confirming the effectiveness through a combination of simulations and experimental comparisons,the measured mid-wave full-field transfer function exceeds 0.405 at 17 lp/mm,satisfying the imaging requirements of the system.The optical system is lightweight and compact,with a total mass under 408 g and a compact volume of justΦ112 mm×117 mm.This serves as a valuable reference for the engineering application of high-performance,compact multi-band infrared composite detection systems for astronomy and space exploration. 展开更多
关键词 Three-band infrared Integrated Rapid assembly Modulation Transfer Function(MTF)
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Temporal Characteristics of GaAs NEA and Alkali Metal Photocathodes 认领 引用 被引量：2
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作者 李相民 周立伟 《Journal of Beijing Institute of Technology》 EI CAS 2003年第4期381-384,共4页
The temporal characteristics of GaAs NEA and alkali metal photocathodes are studied using Monte Carlo simulation method. The electron transit time and its distribution functions in the photocathodes are calculated. Ba... The temporal characteristics of GaAs NEA and alkali metal photocathodes are studied using Monte Carlo simulation method. The electron transit time and its distribution functions in the photocathodes are calculated. Based on the results, the time modulation transfer functions and temporal resolutions of the photocathodes are obtained. The results show that the response time and temporal resolution of alkali metal photocathode is in femitosecond order and those of GaAs NEA photocathode are in picosecond order. 展开更多
关键词 GaAs photocathode alkali metal photocathode Monte Carlo simulation time modulation transfer function
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MTF Measurement of EBCCD Imaging System by Using Super Resolution Technique 认领 引用
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作者 左昉 高岳 +2 位作者 高稚允 苏美开 周立伟 《Journal of Beijing Institute of Technology》 EI CAS 2003年第2期125-128,共4页
Existing methods of measurement MTF for discrete imaging system are analysed. A slit target is frequently used to measure the MTF for an imaging system. Usually there are four methods to measure the MTF for a discrete... Existing methods of measurement MTF for discrete imaging system are analysed. A slit target is frequently used to measure the MTF for an imaging system. Usually there are four methods to measure the MTF for a discrete imaging system by using a slit. These methods have something imperfect respectively. But for the discrete imaging systems of under sampling it is difficult to reproduce this type of target properly since frequencies above Nyquist are folded into those below Nyquist, resulting in aliasing effect. To tackle the aliasing problem, a super resolution technique is introduced into our measurement, which gives MTF values both above and below Nyquist more accurately. 展开更多
关键词 EBCCD modulation transfer function super resolution low light level imaging
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Simplified modeling of frequency behavior in photonic crystal vertical cavity surface emitting laser with tunnel injection quantum dot in active region 认领 引用
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作者 Mehdi Riahinasab Vahid Ahmadi Elham Darabi 《Chinese Physics B》 SCIE EI CAS CSCD 2017年第2期260-267,共8页
In this work, the characteristics of the photonic crystal tunneling injection quantum dot vertical cavity surface emitting lasers（Ph C-TIQD-VCSEL） are studied through analyzing a modified modulation transfer functio... In this work, the characteristics of the photonic crystal tunneling injection quantum dot vertical cavity surface emitting lasers（Ph C-TIQD-VCSEL） are studied through analyzing a modified modulation transfer function. The function is based on the rate equations describing the carrier dynamics at different energy levels of dot and injector well. Although the frequency modulation response component associated with carrier dynamics in wetting layer（WL） and at excited state（ES） levels of dots limits the total bandwidth in conventional QD-VCSEL, our study shows that it can be compensated for by electron tunneling from the injector well into the dot in TIQD structure. Carrier back tunneling time is one of the most important parameters, and by increment of that, the bias current dependence of the total bandwidth will be insignificant. It is proved that at high bias current, the limitation of the WL-ES level plays an important role in reducing the total bandwidth and results in rollovers on 3-d B bandwidth-I curves. In such a way, for smaller air hole diameter of photonic crystal, the effect of this reduction is stronger. 展开更多
关键词 modulation transfer function photonic crystal（PhC） tunnel injection quantum dot（TIQD） vertical cavity surface emitting laser（VCSEL）
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Characterization of a Multimodal and Multispectral Led Imager: Application to Organic Polymer’s Microspheres with Diameter Φ = 10.2 μm 认领 引用 被引量：2
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作者 Marcel A. Agnero Jérémie T. Zoueu Kouakou Konan 《Optics and Photonics Journal》 2016年第7期171-183,共13页
Multispectral microscopy enables information enhancement in the study of specimens because of the large spectral band used in this technique. A low cost multimode multispectral microscope using a camera and a set of q... Multispectral microscopy enables information enhancement in the study of specimens because of the large spectral band used in this technique. A low cost multimode multispectral microscope using a camera and a set of quasi-monochromatic Light Emitting Diodes (LEDs) ranging from ultraviolet to near-infrared wavelengths as illumination sources was constructed. But the use of a large spectral band provided by non-monochromatic sources induces variation of focal plan of the imager due to chromatic aberration which rises up the diffraction effects and blurs the images causing shadow around them. It results in discrepancies between standard spectra and extracted spectra with microscope. So we need to calibrate that instrument to be a standard one. We proceed with two types of images comparison to choose the reference wavelength for image acquisition where diffraction effect is more reduced. At each wavelength chosen as a reference, one image is well contrasted. First, we compare the thirteen well contrasted images to identify that presenting more reduced shadow. In second time, we determine the mean of the shadow size over the images from each set. The correction of the discrepancies required measurements on filters using a standard spectrometer and the microscope in transmission mode and reflection mode. To evaluate the capacity of our device to transmit information in frequency domain, its modulation transfer function is evaluated. Multivariate analysis is used to test its capacity to recognize properties of well-known sample. The wavelength 700 nm was chosen to be the reference for the image acquisition, because at this wavelength the images are well contrasted. The measurement made on the filters suggested correction coefficients in transmission mode and reflection mode. The experimental instrument recognized the microsphere’s properties and led to the extraction of the standard transmittance and reflectance spectra. Therefore, this microscope is used as a conventional instrument. 展开更多
关键词 Multispectral Imaging Reference Wavelength Correction Coefficients Modulation Transfer Function
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The efifect of wave breaking on surface wave imaging by Synthetic Aperture Radar 认领 引用
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作者 孙建 管长龙 史剑 《Chinese Journal of Oceanology and Limnology》 2006年第1期21-27,共7页
The effect of ocean wave breaking as a non-Bragg mechanism on backscattering cross-section and modulation transfer functions （MTF） of radar was investigated based on Bragg resonance theory and parametric method. The... The effect of ocean wave breaking as a non-Bragg mechanism on backscattering cross-section and modulation transfer functions （MTF） of radar was investigated based on Bragg resonance theory and parametric method. The result showed that the additional effect of wave breaking on backscattering cross-section is not more than 20% except for the small incident angle of VV polarized electromagnetic （e.m.） wave but is significant for HH polarized e.m. wave. Breaking waves lead to increase in the modulus of tilt modulation MTF and the larger the wind speed, the faster the increase. For large incident angle, the modulus of tilt modulation MTF with wave breaking decreases quickly with incident angle for HH polarization and approach to that without wave breaking for VV polarization. The hydrodynamic MTF increases 30%-60% when considering wave breaking and the increase is larger for HH polarization than for VV polarization. 展开更多
关键词 Synthetic Aperture Radar modulation transfer function wave breaking tilt modulation hydrodynamic modulation
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Computed Tomography Protocol Optimisation for Pediatric Head Trauma: Radiation Dose and Image Quality Assessment 认领 引用
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作者 Evelyn Anaafi Mary Boadu +2 位作者 Albertina Rusandu Mercy Afadzi Kwame Anokye Amoabeng 《International Journal of Medical Physics, Clinical Engineering and Radiation Oncology》 2022年第3期160-175,共16页
Purpose: Children are sometimes examined with Computed Tomography protocols designed for adults, leading to radiation doses higher than necessary. Lack of optimisation could lead to image quality higher than what is n... Purpose: Children are sometimes examined with Computed Tomography protocols designed for adults, leading to radiation doses higher than necessary. Lack of optimisation could lead to image quality higher than what is needed for diagnostic purposes with associated high doses to patients. Optimising the protocols for paediatric head trauma CT imaging will reduce radiation dose. Objective: The study aimed to optimise radiation dose and assess the image quality for a set of protocols by evaluating noise, a contrast to noise ratio, modulation transfer function and noise power spectrum. Methods: Somaton Sensation 64 was used to scan the head of an anthropomorphic phantom with a set of protocols. ImageJ software was used to analyse the paediatric head image from the scanner. IMPACTSCAN dosimeter software was used to evaluate the radiation dose to the various organs in the head. MATLAB was used to analyse the Modulation Transfer Function and the Noise Power. Results: The estimated Computed Tomography Dose Index volume (CTDIvol) increased with increasing tube current and tube voltage. The high pitch of 0.9 gave a lower dose than the 0.5 pitch. The eye lens received the highest radiation dose (39.2 mGy) whiles the thyroid received the least radiation dose (13.7 mGy). There was an increase in noise (62.46) when the H60 kernel was used and a lower noise (8.829) was noticed when the H30 kernel was used. Conclusion: The results obtained show that the H30 kernel (smooth kernel) gave higher values for noise and contrast to noise ratio (CNR) than the H60 kernel (sharp kernel). The H60 kernel produced high values for the modulation transfer function (MTF) and noise power spectrum (NPS). The eye lens received the highest radiation dose. 展开更多
关键词 Image Quality Radiation Dose Modulation Transfer Function Noise Power Spectrum Optimization
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An Improved Coupling of Numerical and Physical Models for Simulating Wave Propagation 认领 引用 被引量：1
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作者 阳志文 柳淑学 李金宣 《China Ocean Engineering》 SCIE EI CSCD 2014年第1期1-16,共16页
An improved coupling of numerical and physical models for simulating 2D wave propagation is developed in this paper. In the proposed model, an unstructured finite element model （FEM） based Boussinesq equations is ap... An improved coupling of numerical and physical models for simulating 2D wave propagation is developed in this paper. In the proposed model, an unstructured finite element model （FEM） based Boussinesq equations is applied for the numerical wave simulation, and a 2D piston-type wavemaker is used for the physical wave generation. An innovative scheme combining fourth-order Lagrange interpolation and Runge-Kutta scheme is described for solving the coupling equation. A Transfer function modulation method is presented to minimize the errors induced from the hydrodynamic invalidity of the coupling model and/or the mechanical capability of the wavemaker in area where nonlinearities or dispersion predominate. The overall performance and applicability of the coupling model has been experimentally validated by accounting for both regular and irregular waves and varying bathymetry. Experimental results show that the proposed numerical scheme and transfer function modulation method are efficient for the data transfer from the numerical model to the physical model up to a deterministic level. 展开更多
关键词 coupling numerical model physical model wave propagation transfer function modulation
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Controllable structurally randomized Cu mesh films for EMI-shielded optical windows with slight imaging quality degradation 认领 引用
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作者 Yongmao Guan Liqing Yang +3 位作者 Chen Guo Mingde Chen Qinfang Chen Pengfei Wang 《Science China Materials》 SCIE EI CAS CSCD 2026年第7期3856-3867,共12页
This work presents a cracked template and vacuum metal evaporation strategy for fabricating structurally randomized copper(Cu)mesh films.Regulating the internal stress distribution within the coating during template c... This work presents a cracked template and vacuum metal evaporation strategy for fabricating structurally randomized copper(Cu)mesh films.Regulating the internal stress distribution within the coating during template cracking enables the controlled fabrication of Cu mesh films with varying discrete degrees of mesh aperture area and distinct probability distributions of metal line inclination.The influence of structural parameter randomization within the Cu mesh films on properties has been systematically investigated,encompassing higher-order diffraction energy homogenization,optoelectronic performance,and electromagnetic interference shielding effectiveness(EMI SE).Results demonstrate that increasing structural randomization effectively suppresses higher-order diffraction energy,achieving a reduction to-3.93 dB in normalized higher-order diffraction energy.Furthermore,the Cu mesh film exhibited minimal degradation on imaging system performance,with resolution decreasing only marginally from 80.6 to 71.8 lp/mm.Simultaneously,the most randomized Cu mesh film demonstrates an ultra-low sheet resistance(3.31Ω/sq),high visible light transmittance(88.7%at 550 nm),an exceptional figure of merit(FoM=913.69),and robust EMI SE within the X-band(average SE of 33.18 dB).These findings underscore that metal mesh films incorporating structural randomization offer an effective strategy for enhancing EMI shielding in high-performance optoelectronic imaging systems. 展开更多
关键词 cracked template structurally randomized Cu mesh higher-order diffraction energy modulation transfer function transparent EMI shielding window
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Metamerism Recognition Using a Hybrid Operation Optical Differentiator with Dispersion Assistance 认领 引用
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作者 Jiahao Wang Wen Chen +4 位作者 Dongyu Hu Yingxin Xie Zile Li Peng Chen Guoxing Zheng 《Electromagnetic Science》 CSCD 2026年第1期46-55,共10页
Optical analog image processing technology holds great potential for numerous modern applications due to its advantages of high-throughput parallel processing and ultra-low power consumption.The optical spatial differ... Optical analog image processing technology holds great potential for numerous modern applications due to its advantages of high-throughput parallel processing and ultra-low power consumption.The optical spatial differentiator,as a fundamental component of optical analog image processing,finds extensive applications in edge extraction,biomedical imaging,and feature classification.Unfortunately,most current optical differentiators are restricted by a constant modulation transfer function(MTF)across the working wavelength range,which restricts the application of optical differentiators in the spectral domain.Here,we propose and experimentally demonstrate a hybrid operation differentiator that can perform hybrid operations of the 0th-order and 2ndorder radial differential operations within its operational bandwidth,and convert similar color information,which is indiscernible to the human eye,into intensity information that is easily distinguishable.As a proof of concept,we fabricated an electrically tunable liquid crystals(LCs)-based device,which enables continuous adjustment of the MTF at different wavelengths while preserving its broadband operational characteristics,by leveraging the dispersion and electrically tunable characteristics of LCs.The proposed method extends the application range of optical differentiators,expanding from the traditional edge information recognition function to wavelength information recognition.Our approach may have various applications in metamerism recognition,ore color sorting,and advancing biomedical imaging,among others. 展开更多
关键词 Optical differentiator Metamerism recognition Hybrid differential operation Liquid crystal Modulation transfer function
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