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Evaluation of correction algorithm for the Reflectance Measured with Optical Glass

Journal of Donghua University(English Edition) 2003年第2期20卷 52-55页

作者：车江宁周志华陈东辉 School of Graduate Donghua University Shanghai 200051 School of Graduate Donghua University Shanghai 200051he proposed algorithm for reflectance measured with optical glass has been verified with materials of various forms. The reflectances measured with optical glass ( raw) without glass (true) and corrected by the algorithm are compared. The results show that the corrected reflectance agrees very well with true one and their color differences fall below the acceptable limit which indicates the validity of the correction algorithm. The algorithm could be used not only for fiber-forming materials but also for powder-forming granulate-forming etc.

The proposed algorithm for reflectance measured with optical glass has been verified with materials of various forms. The reflectances measured with optical glass ( raw), without glass (true) and corrected by the algorithm are compared. The results show that the corrected reflectance agrees very well with true one and their color differences fall below the acceptable limit, which indicates the validity of the correction algorithm. The algorithm could be used not only for fiber-forming materials, but also for powder-forming, granulate-forming, etc.

关键词： correction algorithm Reflectance Optical Glass

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correction of the image distortion for laser galvanometric scanning system

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OPTICS AND LASER TECHNOLOGY 2005年第4期37卷 305-311页

作者： Xie, J Huang, SH Duan, ZC Shi, YS Wen, SF Huazhong Univ Sci & Technol Rapid Mfg Ctr Sch Mech Sci & Engn Wuhan 430074 Hubei Province Peoples R China

Laser galvanometric scanning techniques are commonly used in various image display fields, such as medical imaging, laser display and material processing. The paper gives detail analyses of the image distortion involved in the galvanometric scanning. At the same time, the paper addresses the role of the correction algorithms of the image distortion. Experiment results based on SLS machine prove the efficiency of the correction algorithms. (C) 2004 Elsevier Ltd. All rights reserved.

关键词： galvanometric scanning image distortion correction algorithm

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Error characteristics of the atmospheric correction algorithms used in retrieval of sea surface temperatures from infrared satellite measurements:: Global and regional aspects

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JOURNAL OF THE ATMOSPHERIC SCIENCES 2003年第3期60卷 575-585页

作者： Kumar, A Minnett, PJ Podestá, G Evans, RH Univ Miami Rosenstiel Sch Marine & Atmospher Sci Meteorol & Phys Oceanog Div Miami FL 33149 USA

A database of cotemporal, collocated satellite and in situ observations is used to examine the association between the brightness temperature differences measured by the thermal infrared channels (T45) of the Advanced Very High Resolution Radiometer (AVHRR) and water vapor estimates (omega) derived from the Special Sensor Microwave Imager (SSM/I). This channel difference is used to estimate the atmospheric correction (due mostly to water vapor absorption) in sea surface temperature (SST) algorithms. The association between T45 and vis found to be greatest for tropical latitudes;for mid- and high latitudes, the association is best during summer. However, the association tends to decrease toward mid- and higher latitudes during other periods. SST residual errors (satellite 2 buoy) show a negative mean in the Tropics, suggesting undercorrection for water vapor attenuation in the Tropics. This underestimation is explicitly shown for SST residuals in the high-water-vapor regimes of the Arabian Sea. In mid- and high latitudes, the variability of atmospheric water vapor and air-sea temperature difference contributes to the weaker association between T45 and v and results in positive mean SST residual errors. A differential form of SST algorithm that incorporates the use of a "first-guess estimate'' that correlates with SST is observed to give the least residual error.

关键词： Sst Space Skin Association (Psychology) sea-surface temperature Water Vapor satellites skin retrieval correction algorithm Special Sensor Microwave/Imager polar regions tropics atmospheric correction Arabian Sea temperature gradients Atmospheric Water Vapor MIDS

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correction of conductance measurements in non-space-clamped structures:: 1.: Voltage-gated K⁺ channels

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BIOPHYSICAL JOURNAL 2003年第6期84卷 3508-3528页

作者： Schaefer, AT Helmstaedter, M Sakmann, B Korngreen, A Bar Ilan Univ Fac Life Sci IL-52900 Ramat Gan Israel Max Planck Inst Med Res Zellphysiol Abt D-69120 Heidelberg Germany

To understand functions of a single neuron, such as propagation and generation of synaptic or action potentials, a detailed description of the kinetics and distribution of the underlying ionic conductances is essential. In voltage-clamp experiments, incomplete space clamp distorts the recorded currents, rendering accurate analysis impossible. Here, we present a simple numerical algorithm that corrects such distortions. The method performs a stepwise approximation of the conductance density at the site of a local voltage clamp. This is achieved by estimating membrane conductances in a simulation that yields simulated clamp currents, which are then fitted to the distorted recordings from the non-space-clamped structure, relying on accurately reconstructed cell morphology and experimentally determined passive properties. The method enabled accurate retrieval of the local densities, kinetics, and density gradients of somatic and dendritic channels. Neither the addition of noise nor variation of passive parameters significantly reduced the performance of the correction algorithm. The correction method was applied to two-electrode voltage-clamp recordings of K+ currents from the apical dendrite of layer 5 neocortical pyramidal neurons. The generality and robustness of the algorithm make it a useful tool for voltage-clamp analysis of voltage-gated currents in structures of any morphology that is amenable to the voltage-clamp technique.

关键词： .Korngreen conductances voltage-clamp conductance density correction algorithm

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Tomographic motion detection and correction directly in sinogram space

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PHYSICS IN MEDICINE AND BIOLOGY 2002年第8期47卷 1267-1284页

作者： Lu, WG Mackie, TR Univ Wisconsin Dept Med Phys Madison WI 53706 USA

Patient motion, especially respiratory motion, results in various artefacts such as blurring and streaks in tomographic images. The interplay of the movement of the beam aperture and variations of organ anatomy during delivery can create 'hot' and 'cold' spots throughout the field in intensity-modulated radiation therapy (IMRT). Detection and correction of patient motion is extremely important in tomographic imaging and IMRT. Tomographic projection data (sinogram) encode not only the patient anatomy information, but also the intra-scanning motion information. In this paper. we developed an algorithm to detect and correct the in-plane respiratory motion directly in sinogram space. The respiratory motion is modelled as time-varying scaling along the x and v directions. Its effects on the sinogram are discussed. Based on the traces of some nodal points in the sinogram, the intra-scanning motion is determined. The motion correction is also implemented in sinogram space. The motion-corrected sinogram is used for reconstruction by the filtered back-projection (FBP) method. Computer simulations validate the motion detection and correction algorithm. The reconstructed images from the motion-corrected sinogram eliminate the majority of the artefacts. The method could be applied to projection data used in CT and ECT, as well as in tomotherapy delivery modification and dose reconstruction.

关键词： correction algorithm Tomography sinogram Motion detection COLD SPOT Patient Motion Artifact

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Improved topographic correction for satellite imagery

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IEICE TRANSACTIONS ON INFORMATION AND SYSTEMS 2001年第12期E84D卷 1820-1827页

作者： Chen, F Muramoto, K Kubo, M Kanazawa Univ Grad Sch Nat Sci & Technol Div Mat & Informat Sci Kanazawa Ishikawa 9208667 Japan

An improved algorithm is developed for correcting the topographic impact on satellite imagery, First, we analyze the topography induced distortion un satellite image. It is shown that the variation of aspect can cause the obvious different distortions in the remotely sensed image, and also effect the image illumination significantly. Because the illumination is the basis for topographic correction algorithms, we consider its variation in different smi-facing aspects in calculation a correction parameter and take it as a key element in the modified correction algorithm. Then, we apply the modified correction method on the actual Landsat Thematic Mapper satellite image. The topographic correction was done in different image data with different season and different solar angle. The corrected results show the effectiveness and accuracy using this approach.

关键词： satellite imagery mountainous region topographic factor correction algorithm

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Rebinning-based algorithms for helical cone-beam CT

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PHYSICS IN MEDICINE AND BIOLOGY 2001年第11期46卷 2911-2937页

作者： Defrise, M Noo, F Kudo, H Free Univ Brussels Dept Nucl Med B-1050 Brussels Belgium Univ Liege Inst Montefiore B-4000 Liege Belgium Univ Tsukuba Inst Informat Sci & Elect Tsukuba Ibaraki 305 Japan

Several image reconstruction algorithms based on rebinning have been proposed recently for helical cone-beam CT. These algorithms separate the 3D reconstruction into a set of independent 2D reconstructions for a set of surfaces: planar or non-planar surfaces are defined and then reconstructed using 2D filtered backprojection from a 2D fan-beam or parallel-beam set of data estimated from the cone-beam (CB) measurements. The first part of this paper presents a unified derivation of rebinning algorithms for planar and nonplanar surfaces. An integral equation is derived for the surface allowing the best rebinning and an iterative algorithm converging to the solution of that equation is given. The second part presents an efficient method to correct the residual reconstruction artefacts observed with rebinning algorithms when the cone-anale is too large for the required accuracy. This correction algorithm involves a CB backprojection and the reconstruction time is slightly longer than for the zero-boundary (ZB) method.

关键词： algorithms seconds X-Ray Computed Tomography allowing Solutions 算法溶液 backprojection algorithms Reconstructive Surgical Procedures Planar Spiral Cone-Beam Computed Tomography correction algorithm nonplanarity X-Ray Computed Tomography three-dimensional displays

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Nonrandom quantization errors in timebases

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IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT 2001年第4期50卷 888-892页

作者： Stenbakken, GN Liu, D Starzyk, JA Waltrip, BC US Dept Commerce Natl Inst Stand & Technol Technol AdmDiv Elect Elect & Elect Engn Lab Gaithersburg MD 20878 USA Ohio Univ Sch Elect Engn & Comp Sci Athens OH 45701 USA

Timebase distortion causes nonlinear distortion of waveforms measured by sampling instruments. When such instruments are used to measure the rms amplitude of the sampled waveforms, such distortions result in errors in the measured root-mean squared (rms) values. This paper looks at the nature of the errors that result from nonrandom quantization errors in an instrument's timebase circuit. Simulations and measurements on a sampling voltmeter show that the errors in measured rms amplitude have a nonnormal probability distribution, such that the probability of large errors is much greater than would be expected from the usual quantization noise model. A novel timebase compensation method is proposed which makes the measured rms errors normally distributed and reduces their standard deviation by a factor of 25. This compensation method was applied to a sampling voltmeter and the improved accuracy was realized.

关键词： compensation correction algorithm quantization sampling timebase voltmeter

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Nonrandom quantization errors in timebases

Nonrandom quantization errors in timebases

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Instrumentation and Measurement Technology Conference (IMTC 2000)

ISBN: (纸本)0780358902

关键词： compensation correction algorithm quantization sampling timebase voltmeter

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Atmospheric correction of SeaWiFS imagery for turbid coastal and inland waters

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APPLIED OPTICS 2000年第6期39卷 897-912页

作者： Ruddick, KG Ovidio, F Rijkeboer, M Math Models N Sea Management Unit B-1200 Brussels Belgium Free Univ Amsterdam Inst Environm Studies NL-1081 HV Amsterdam Netherlands

The standard SeaWiFS atmospheric correction algorithm, designed for open ocean water, has been extended for use over turbid coastal and inland waters. Failure of the standard algorithm over turbid waters can be attributed to invalid assumptions of zero water-leaving radiance for the near-infrared bands at 765 and 865 nm. In the present study these assumptions are replaced by the assumptions of spatial homogeneity of the 765:865-nm ratios for aerosol reflectance and for water-leaving reflectance. These two ratios are imposed as calibration parameters after inspection of the Rayleigh-corrected reflectance scatterplot. The performance of the new algorithm is demonstrated for imagery of Belgian coastal waters and yields physically realistic water-leaving radiance spectra. A preliminary comparison with in situ radiance spectra fbr the Dutch Lake Markermeer shows significant improvement over the standard atmospheric correction algorithm. An analysis is made of the sensitivity of results to the choice of calibration parameters, and perspectives for application of the method to other sensors are briefly discussed. (C) 2000 Optical Society of America.

关键词： Water-leaving Radiance atmospheric correction Inland waters correction algorithm sea water SeaWiFS application methods

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