Fine localization of photons on the pixellated detectors based on the analytical model
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In this paper, an analytical model for evaluating the charge induction on pixels of the pixellated CdZnTe (CZT) detector is proposed. According to this model, the cross-talk between pixels increases while the pixel size decreases. We also propose a method for determining the position of charges more accurately by exploiting the charge sharing between the neighboring pixels. Conventionally to increase the resolution of the image, the pixel size is decreased that results in an increase in the amount of cross-talk. With our proposed method, the resolution of the image is effectively increased without the need for decreasing the pixel size.Keywords:
Charge sharing
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Sub-pixel resolution
Hyperspectral image super resolution (SR) reconstruction has been studied widely and many algorithms have been proposed. In this paper, a novel super resolution reconstruction method was designed by employing a joint spectral-spatial sub-pixel mapping model which aims to obtain the probabilities of sub-pixels to belong to different land cover classes by dividing mixed pixels into several sub-pixels. Given these sub-pixel probabilities, the resolution enhanced image can be further generated. The proposed approach has been evaluated using both synthetic and real hyperspectral images and compared with other well-known methods. The visual and quantitative comparisons confirm the effectiveness of the proposed method.
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Land Cover
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The consequences of changes in spatial resolution for application of thermal imagery in plant phenotyping in the field are discussed. Where image pixels are significantly smaller than the objects of interest (e.g., leaves), accurate estimates of leaf temperature are possible, but when pixels reach the same scale or larger than the objects of interest, the observed temperatures become significantly biased by the background temperature as a result of the presence of mixed pixels. Approaches to the estimation of the true leaf temperature that apply both at the whole-pixel level and at the sub-pixel level are reviewed and discussed.
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Charge sharing
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Charge sharing
Photon Counting
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In this paper, an analytical model for evaluating the charge induction on pixels of the pixellated CdZnTe (CZT) detector is proposed. According to this model, the cross-talk between pixels increases while the pixel size decreases. We also propose a method for determining the position of charges more accurately by exploiting the charge sharing between the neighboring pixels. Conventionally to increase the resolution of the image, the pixel size is decreased that results in an increase in the amount of cross-talk. With our proposed method, the resolution of the image is effectively increased without the need for decreasing the pixel size.
Charge sharing
Position (finance)
Sub-pixel resolution
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Charge sharing
Sub-pixel resolution
Photon Counting
Dot pitch
SIGNAL (programming language)
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To compare the characteristics of imaging systems based on pixel detectors of different thickness, we have measured the respective imaging capabilities, spatial resolution and spectroscopic characteristics. Each system consists of a single photon counting chip, developed in the framework of the Medipix Collaboration, bump bonded to a silicon detector. The detector is a matrix of 64 /spl times/ 64 square pixels, with 170 /spl mu/m pitch and thickness ranging from 300 to 800 /spl mu/m. As expected, the intrinsic detection efficiency increases with the detector thickness; nevertheless the spatial resolution can be affected by a charge sharing mechanism between adjacent pixels due to charge diffusion. The aim of the work reported in this paper is to demonstrate that, optimizing the settings of the image systems, we can increase the detection efficiency without losing in spatial resolution.
Charge sharing
Photon Counting
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Ranging
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Patterned pixel array was proposed to increase the number of energy bins in a single pixel of photon counting detectors without adding more comparators and counters. The pixels were grouped into four different types and each pixel has a common threshold and a specific threshold assigned to each pixel type. The common threshold in every pixel records the total number of incident photons regardless of its pixel type and the specific thresholds classify incident photon energies. The patterned pixel array was evaluated with the pinhole gamma camera system based on the XRI-UNO detector flip-chip bonded with a 1mm thick CdTe sensor. The experimental data was acquired with time-over-threshold mode to avoid the charge sharing problem. The shared total charges created by one photon can be found by summing all pixels within the cluster. To correct the different response to the same energy of photon, the energy calibration of the time-over-threshold value was perfomed independently depending on the cluster size. The time-over-threshold values were separated into two energy bins since we assumed that each pixel has two thresholds. Although each pixel has only two thresholds, five images from different energy windows were obtained by sharing the spectal information from four adjacent pixels. Thus, degradation of the spatial resolution in the image occured in each energy window. The image of the entire energy, however, was not degraded since all four different types of pixels have a common threshold just above the noise level. In addition, the number of steps for the threshold scan method can be drastically reduced with the increased number of effective thresholds in a single pixel.
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Charge sharing
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The color X-ray camera SLcam(R) is a full-field, single photon detector providing scanning free, energy and spatially resolved X-ray imaging. Spatial resolution is achieved with the use of polycapillary optics guiding X-ray photons from small regions on a sample to distinct energy dispersive pixels on a CCD. Applying sub-pixel resolution, signals from individual capillary channels can be distinguished. Accordingly the SLcam(R) spatial resolution can be released from pixel size being confined rather to a diameter of individual polycapillary channels. In this work a new approach to sub-pixel resolution algorithm comprising photon events also from the pixel centers is proposed. The details of the employed numerical method and several sub-pixel resolution examples are presented and discussed.
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