Stereoscopic dual-energy X-ray imaging for target materials identification

An experimental stereoscopic dual-energy X-ray imaging system is employed to extract the effective atomic number from a target layer of multiple layers of different materials. Further work investigated utilising stereoscopic parallax data to calculate layer thickness which, when combined with dual-energy data, enables the mass density of the target to be established. The research is part of an ongoing programme of work in collaboration with the UK Home Office to discriminate and identify substances in X-ray security screening applications. Initial work utilised a basis materials decomposition (BMD) technique to compute the characteristic angle, an indicator of atomic composition. The problem of overlapping materials masking a target was solved by further refinement of the BMD method, which can also be used determine mass density when layer thickness is known. The empirical investigation concentrated on computing the characteristic angle for different target materials in various overlapping arrangements. Also, the results from employing manually extracted parallax data to calculate the thickness of a target material are presented together with the resultant estimation of the targets' mass density.     

A subspace matching color filter design methodology for a multispectral imaging system.

In this paper, we present a methodology to design filters for an imaging system to improve the accuracy of the spectral measurements for families of reflective surfaces. We derive the necessary and sufficient conditions that the sensor space of the system must obey in order to measure the spectral reflectance of the surfaces accurately. Through simulations, we show how these conditions can be applied to design filters using a set of sample spectral data acquired from extracted teeth. For this set of data, we also compare our results to those of Wolski's method, a conventional filter design method which produces filters that recover tristimulus values of surfaces accurately under several illuminants. We show that our method produces filters that capture the spectral reflectance better given the same number of measurements. The errors in predicting the color of the sample data are much lower under every test illuminant when the filters designed with our method are used.     

Novel color demosaicking for noisy color filter array data

Single sensor digital color still/video cameras use color demosaicking to reproduce full color images from color filter array (CFA) data. The quality of interpolated image will be degraded due to the sensor noise introduced during the image capture process. Many conventional demosaicking-denoising solutions adopt the channel-dependent noise model, which may fit the CMOS/CCD image sensor less than signal-dependent noise model. In this paper, the wavelet sub-band decomposition and synthesis are applied to interpolate the CFA data with signal-dependent noise model. The major contributions of this work include: (1) The combination of LMMSE and statistical calculation in wavelet domain are utilized to suppress the signal-dependent noise, which is separated into additive noise and multiplicative noise. (2) In CFA data, it has been verified that the quantitative relationship between the current pixel and the adjacent pixel, which locate in the same edge. Both simulated and real CFA images are employed to compare the proposed algorithm with the state-of-the-art techniques reported in the literature. The experimental results confirm that our method outperforms them both on demosaicking performance and on computational cost, when they process the noisy color filter array data.     

Vector filtering for color imaging

Vector processing operations use essential spectral and spatial information to remove noise and localize microarray spots. The proposed fully automated vector technique can be easily implemented in either hardware or software; and incorporated in any existing microarray image analysis and gene expression tool.     

位相调制图像密度假彩色编码的处理方法

介绍了位相调制图像密度假彩色编码的原理及实验方法，并就实验过程中应注意的一些问题作出了较详细的说明     

Adaptive filtering for color filter array demosaicking.

Most digital still cameras acquire imagery with a color filter array (CFA), sampling only one color value for each pixel and interpolating the other two color values afterwards. The interpolation process is commonly known as demosaicking. In general, a good demosaicking method should preserve the high-frequency information of imagery as much as possible, since such information is essential for image visual quality. We discuss in this paper two key observations for preserving high-frequency information in CFA demosaicking: (1) the high frequencies are similar across three color components, and (2) the high frequencies along the horizontal and vertical axes are essential for image quality. Our frequency analysis of CFA samples indicates that filtering a CFA image can better preserve high frequencies than filtering each color component separately. This motivates us to design an efficient filter for estimating the luminance at green pixels of the CFA image and devise an adaptive filtering approach to estimating the luminance at red and blue pixels. Experimental results on simulated CFA images, as well as raw CFA data, verify that the proposed method outperforms the existing state-of-the-art methods both visually and in terms of peak signal-to-noise ratio, at a notably lower computational cost.     

Fast bilateral filter for HDR imaging

Bilateral filtering is a method often used in image processing applications. It is specifically useful for HDR algorithms. A novel approach to a fast and close approximation of bilateral filtering is presented. The method is designed especially with a focus on HDR image conversion into a normal color space processing. This paper presents the methods itself, describes the sources of acceleration and discusses the results of the method.     

彩色滤光片制备方法概述

彩色滤光片是液晶显示器中实现彩色显示的重要部件,其制备工艺直接影响决定了彩色滤光片的性能。本文介绍了彩色滤光片结构及原理,比较分析了各种彩色滤光层的制作方法的优势和劣势,提出喷墨法由于具有快速、精准、材料利用率高等一系列优点,其已经成为制备大尺寸彩色滤光片极有竞争力的一项技术,并简要阐述喷墨法国内外的发展现状及。     

An NMOS dual-mode digital low-pass filter for color TV

A low-pass filter for separation of the luminance and chroma spectra is dealt with. The function of the filter and the implementation of the filter on a chip are briefly described and the circuit design is discussed in some detail. The chip, which runs at frequencies up to 40 MHz, has been designed with two-phase race-compensated MOS logic in a 4 /spl mu/m E/D NMOS technology with implanted undercrossings.     

Spatio-spectral color filter array design for optimal image recovery

In digital imaging applications, data are typically obtained via a spatial subsampling procedure implemented as a color filter array-a physical construction whereby only a single color value is measured at each pixel location. Owing to the growing ubiquity of color imaging and display devices, much recent work has focused on the implications of such arrays for subsequent digital processing, including in particular the canonical demosaicking task of reconstructing a full color image from spatially subsampled and incomplete color data acquired under a particular choice of array pattern. In contrast to the majority of the demosaicking literature, we consider here the problem of color filter array design and its implications for spatial reconstruction quality. We pose this problem formally as one of simultaneously maximizing the spectral radii of luminance and chrominance channels subject to perfect reconstruction, and-after proving sub-optimality of a wide class of existing array patterns-provide a constructive method for its solution that yields robust, new panchromatic designs implementable as subtractive colors. Empirical evaluations on multiple color image test sets support our theoretical results, and indicate the potential of these patterns to increase spatial resolution for fixed sensor size, and to contribute to improved reconstruction fidelity as well as significantly reduced hardware complexity.     

Analysis of false alarm for imaging space-based laser warning system

In view of the problem of false alarm in imaging space-based laser warning system, the effects of sunlight and lightning on the threaten laser detection and attack event determination are studied by analyzing and calculating the radiant energy density and space-time feature of imaging spot, respectively. The results show that the main false alarm resourses of spacebased laser warning system are sunlight and lightning. The sunlight should exposure the detector directly in one ninth of the satillite orbital period, and the imaging spot of sun is similar to the attack laser. The lightning imaging spot is similar to the illumination laser. About 1.4 lightning events can occur in the field of view (FOV) of the warning system per second. It could not discriminate spots of sun, lightning and threaten laser by the frame subtraction technology.     

Fabrication and performance of color filter arrays for solid-state imagers

A technique has been developed for the fabrication of a color filter array (CFA) to be used in conjunction with a solid-state area sensor to provide three-color image information from a single sensor. The fabrication technique employs sublimable dyes which are heat-transferred through photoresist windows onto a polymer receiving layer. Good edge sharpness and a low dye penetration depth into the polymer have been achieved. The predicted and measured spectral response of the color channels of the composite device are in good agreement. The pattern noise associated with CFA transmittance fluctuations from element to element is on the order of 10 percent.     

X-ray computed tomography for medical imaging

The article looks at reconstruction in 2-D and 3-D tomography. We have not dealt with some of the issues in reconstruction such as sampling and aliasing artifacts, finite detector aperture artifacts, beam hardening artifacts, etc., in greater detail since these are beyond the scope of an introductory tutorial. We examine the physical and mathematical concepts of the Radon (1917) transform, and the basic parallel beam reconstruction algorithms are discussed. We also develop the algorithms for fan-beam CT, and discuss the mathematical principles of cone-beam CT     

A vector Wiener filter for dual-radionuclide imaging

The routine use of a single radionuclide for patient imaging in nuclear medicine can be complemented by studies employing two tracers to examine two different processes in a single organ, most frequently by simultaneous imaging of both radionuclides in two different energy windows. In addition, simultaneous transmission/emission imaging with dual-radionuclides has been described, with one radionuclide used for the transmission study and a second for the emission study. There is thus currently considerable interest in dual-radionuclide imaging. A major problem with all dual-radionuclide imaging is the "crosstalk" between the two radionuclides. Such crosstalk frequently occurs, because scattered radiation from the higher energy radionuclide is detected in the lower energy window, and because the lower energy radionuclide may have higher energy emissions which are detected in the higher energy window. The authors have previously described the use of Fourier-based restoration filtering in single photon emission computed tomography (SPECT) and positron emission tomography (PET) to improve quantitative accuracy by designing a Wiener or other Fourier filter to partially restore the loss of contrast due to scatter and finite spatial resolution effects. The authors describe here the derivation and initial validation of an extension of such filtering for dual-radionuclide imaging that simultaneously 1) improves contrast in each radionuclide's "direct" image, 2) reduces image noise, and 3) reduces the crosstalk contribution from the other radionuclide. This filter is based on a vector version of the Wiener filter, which is shown to be superior [in the minimum mean square error (MMSE) sense] to the sequential application of separate crosstalk and restoration filters.     

A surface acoustic wave filter for color TV receiver VIF

A surface acoustic wave filter for color TV-VIF with a low insertion loss and high selectivity was developed using modified normal type interdigital transducers. Single-crystalline LiNbO3was used as the substrate and the electrodes were formed by photolithographic technique. The ripples in the passband were suppressed by means of a step-type transducer and the sidelobes in the out-of-band were decreased by eliminating some finger elements of the transducer. Filter chip was so small that it could be packaged in a TO-5 type can.     

Quaternion switching filter for impulse noise reduction in color image

A novel approach to impulse noise reduction in color image is introduced in this paper. By applying the quaternion unit transform theory, the difference between two color pixels can be represented in the quaternion form. Based on the difference mentioned above, an efficient filter that can switch between the vector median filter (VMF) and the identity filter (no filtering operation) is proposed. Extensive simulation result indicates that the proposed filter achieves a trade-off between noise suppression and detail preservation in both correlated and uncorrelated impulse noise scenarios when compared with other widely used filters. Furthermore, the computational complexity analysis shows that the proposed filter is quite efficient.     

Effects of scatter in dual-energy imaging: an alternative analysis

Dual-energy imaging provides images in which the conspicuity of the signal of interest is heightened by selectively cancelling intervening structures. Area detectors for dual-energy imaging offer some advantages over line-scanning systems because they make efficient use of the source. Area detectors, however, collect scattered radiation. To determine the seriousness of the scatter problem and how effective scatter correction is at reducing scatter's deleterious effects, dual-energy imaging in the presence of scatter is simulated. The coefficients are modified so that the intervening material and the scatter are cancelled in some particular region of the image. Results for simulations of two clinically important material-subtraction-the bone-subtraction image and the soft-tissue-subtraction image-are presented. The effects of scatter on contrast, noise variance, and SNR for the two subtractions are examined.     

A color separating filter integrated vidicon for frequency multiplex system single pickup tube color television camera

A new vidicon with color separating stripe filter integrated faceplate was developed for frequency multiplex system using a single pickup tube color television camera. The distinctive features of the vidicon are 1) a faceplate with integrated color separating stripe filters, 2) an indium oxide transparent electrode, and 3) a set of spatial frequency limiting quartz filters which act as a limiter for spurious color signals. A color television camera using this vidicon provided satisfactory color pictures.     

Amplified MOS imager for soft X-ray imaging

This paper describes a new area sensor for soft X-rays, and its performance. The operational principle is based on detecting the change in potential of a floating photodiode caused by X-ray-induced electron-hole pairs generation in a stacked amorphous silicon photoconversion layer. The photoresponse was measured at wavelength from 50 /spl Aring/ to 160 /spl Aring/. The signal to noise ratio of 25 dB was achieved, when the number of incident 70 /spl Aring/ X-ray photons is as low as 230/pixel. Quantum efficiency (stored carriers/photon) at 70 /spl Aring/ wavelength was 22. In addition, good reproducibility (<10% deviation) between different detectors and good reproducibility (<20% deviation) after ten months were also clarified. The performance of this area sensor indicates its potential for detection of soft X-ray images.<>     

A positive-reading silicon vidicon for X-ray imaging

A silicon vidicon that uses an n on p silicon diode array for a target was designed. The electron beam landing energy is 600 eV, and all the diodes are charged to a reversed bias by secondary electron emission. With the high electron beam energy, it is possible to sharply focus the beam into a sheet beam, which can be used to simultaneously bombard several separate linear diode arrays in a detector scheme for a bent-crystal X-ray spectrometer. By such a method, the bandwidth requirement of the data-transmission system is reduced by a factor equal to the number of separate linear arrays that are simultaneously bombarded. Data are presented on the diode-charging mechanism, with emphasis on the method used to determine the potential of the diode n-surface. Examples are shown of the tube being used to detect 25-keV X-rays.