The security market requirements for state-of-the-art mobile and portal radiography inspection systems include high imaging resolution (better than 5 mm line pair), penetration beyond 300 mm steel equivalent, material...
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ISBN:
(纸本)9781509016426
The security market requirements for state-of-the-art mobile and portal radiography inspection systems include high imaging resolution (better than 5 mm line pair), penetration beyond 300 mm steel equivalent, material discrimination (three groups of Z) at speeds up to 16 km/h with 100% image sampling, low dose and small radiation exclusion zone. New research into radiography methods and systems has been actively pursued in order to achieve these challenging requirements. Recently, a significant portion of the R&D effort has been devoted to re-examining betatron based X-ray inspection systems. The advantages of the betatron-based inspection systems over conventional linac-based designs include small focal spot (which improves resolution), low weight and form-factor, a simpler control system and relatively low cost. A novel, low-dose Multi-Energy Betatron-based Cargo Inspection System, MEBCIS, presented in this paper relies on an innovative technique of extracting two X-ray pulses with lower-and higher-energies within a single betatron acceleration cycle (in contrast to conventional dual-energy betatrons with one Xray pulse produced during separate betatron acceleration cycles). In addition to the new betatron, new types of fast X-ray Scintillation-Cherenkov detectors, rapid processing of detector signals, an adaptive detector feedback algorithm for control of the betatron, and algorithms for intelligent material discrimination are parts of the overall MEBCIS system. The key advantage of the MEBCIS concept is that the material discrimination data is acquired in a single scan line rather than two. Thus, for the same betatron pulse rate, the scan rate can be twice as fast (better throughput) or can be done with a lower dose, even without adaptive dynamic pulse adjustment. Application of these techniques will maximize material discrimination, penetration, and contrast resolution while simultaneously reducing dose to the environment, resulting in a smaller exclusion zone.
In the domain of imageprocessing, often real-time constraints are required. In particular, in safety-critical applications, timing is of utmost importance. A common approach to maintain real-time capabilities is to o...
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In the domain of imageprocessing, often real-time constraints are required. In particular, in safety-critical applications, timing is of utmost importance. A common approach to maintain real-time capabilities is to offload computations to dedicated hardware accelerators, such as Field Programmable Gate Arrays (FPGAs). Designing such architectures is per se already a challenging task, but finding the right design point between achieving as much throughput as necessary while spending as few resources as possible is an even bigger challenge. To address this design challenge in the domain of imageprocessing, several approaches have been presented that introduce an additional layer of abstraction between the developer and the actual target hardware. One approach is to use a Domain-Specific Language (DSL) to generate highly optimized code for synthesis by general purpose High-Level Synthesis (HLS) frameworks. Another approach is to instantiate a generic vHDL IP-Core library for local imaging operators. Elevating the description of imagealgorithms to such a higher abstraction level can significantly reduce the complexity for designing hardware accelerators targeting FPGAs. We provide a comparison of results for both approaches, a non-expert algorithm developer can achieve. Furthermore, we present an automatic optimization process to give the algorithm developer even more control over trading execution time for resource usage, that could be applied on top of both approaches. To evaluate our optimization procedure, we compare the resulting FPGA accelerators to highly optimized Graphics processing Unit (GPU) implementations of several image filters relevant for close-to-sensor image and video processing with stringent real-time constraints, such as in the automotive domain. (C) 2015 Elsevier B.v. All rights reserved.
Non-local cost aggregation has recently emerged as a promising approach for stereo-matching and has attracted much interest over the past few years. Most non-local algorithms are reportedly better than state-of-the-ar...
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Non-local cost aggregation has recently emerged as a promising approach for stereo-matching and has attracted much interest over the past few years. Most non-local algorithms are reportedly better than state-of-the-art local algorithms for high-quality indoor images. However, the accuracy of non-local algorithms is still limited for outdoor images. Computing disparity maps for outdoor images in driver assistance systems is one of the most actively researched topics in the field of stereo vision. In this paper, we present a robust non-local stereo matching algorithm that improves the performance of non-local approaches for outdoor driving images. The proposed algorithm is inspired by the non-local cost aggregation method based on a minimum spanning tree, and it improves the estimation accuracy by introducing an alternate, effective segment-simple-tree that is more adequate for outdoor driving images than the minimum spanning tree. Experimental results showed that the proposed algorithm is superior to the existing local and non-local algorithms, and is comparable to semi-global matching. (C) 2015 Elsevier B.v. All rights reserved.
Deep convolutional neural networks take GPU-days of computation to train on large data sets. Pedestrian detection for self driving cars requires very low latency. image recognition for mobile phones is constrained by ...
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ISBN:
(纸本)9781467388528
Deep convolutional neural networks take GPU-days of computation to train on large data sets. Pedestrian detection for self driving cars requires very low latency. image recognition for mobile phones is constrained by limited processing resources. The success of convolutional neural networks in these situations is limited by how fast we can compute them. Conventional FFT based convolution is fast for large filters, but state of the art convolutional neural networks use small, 3×3 filters. We introduce a new class of fast algorithms for convolutional neural networks using Winograd's minimal filtering algorithms. The algorithms compute minimal complexity convolution over small tiles, which makes them fast with small filters and small batch sizes. We benchmark a GPU implementation of our algorithm with the vGG network and show state of the art throughput at batch sizes from 1 to 64.
Robotic vision, unlike computer vision, typically involves processing a stream of images from a camera with time varying pose operating in an environment with time varying lighting conditions and moving objects. Repea...
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ISBN:
(纸本)9781509037636
Robotic vision, unlike computer vision, typically involves processing a stream of images from a camera with time varying pose operating in an environment with time varying lighting conditions and moving objects. Repeating robotic vision experiments under identical conditions is often impossible, making it difficult to compare different algorithms. For machine learning applications a critical bottleneck is the limited amount of real world image data that can be captured and labelled for both training and testing purposes. In this paper we investigate the use of a photo-realistic simulation tool to address these challenges, in three specific domains: robust place recognition, visual SLAM and object recognition. For the first two problems we generate images from a complex 3D environment with systematically varying camera paths, camera viewpoints and lighting conditions. For the first time we are able to systematically characterise the performance of these algorithms as paths and lighting conditions change. In particular, we are able to systematically generate varying camera viewpoint datasets that would be difficult or impossible to generate in the real world. We also compare algorithm results for a camera in a real environment and a simulated camera in a simulation model of that real environment. Finally, for the object recognition domain, we generate labelled image data and characterise the viewpoint dependency of a current convolution neural network in performing object recognition. Together these results provide a multi-domain demonstration of the beneficial properties of using simulation to characterise and analyse a wide range of robotic vision algorithms.
This article considers the problem of constructing a sequential computational procedure for detecting artificial changes of remote sensing data (RSD) using a set of elementary algorithms of detecting artificial RSD ch...
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image segmentation is a key component in many computer vision systems, and it is recovering a prominent spot in the literature as methods improve and overcome their limitations. The outputs of most recent algorithms a...
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ISBN:
(纸本)9781467388528
image segmentation is a key component in many computer vision systems, and it is recovering a prominent spot in the literature as methods improve and overcome their limitations. The outputs of most recent algorithms are in the form of a hierarchical segmentation, which provides segmentation at different scales in a single tree-like structure. Commonly, these hierarchical methods start from some low-level features, and are not aware of the scale information of the different regions in them. As such, one might need to work on many different levels of the hierarchy to find the objects in the scene. This work tries to modify the existing hierarchical algorithm by improving their alignment, that is, by trying to modify the depth of the regions in the tree to better couple depth and scale. To do so, we first train a regressor to predict the scale of regions using mid-level features. We then define the anchor slice as the set of regions that better balance between over-segmentation and under-segmentation. The output of our method is an improved hierarchy, re-aligned by the anchor slice. To demonstrate the power of our method, we perform comprehensive experiments, which show that our method, as a post-processing step, can significantly improve the quality of the hierarchical segmentation representations, and ease the usage of hierarchical image segmentation to high-level vision tasks such as object segmentation. We also prove that the improvement generalizes well across different algorithms and datasets, with a low computational cost.
Hyperspectral image analysis is considered as a promising technology in the field of remote sensing over the past decade. There are various processing and analysis techniques developed that interpret and extract the m...
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Convolutional neural networks (CNNs), in combination with big data, are increasingly being used to engineer robustness into visual classification systems including human detection. One significant challenge to using a...
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ISBN:
(纸本)9781509039302
Convolutional neural networks (CNNs), in combination with big data, are increasingly being used to engineer robustness into visual classification systems including human detection. One significant challenge to using a CNN on a mobile robot, however, is the associated computational cost and detection rate of running the network. In this work, we demonstrate how fusion with a feature-based layered classifier can help. Not only does score-level fusion of a CNN with the layered classifier improve precision/recall for detecting people on a mobile robot, but using the layered system as a pre-filter can substantially reduce the computational cost of running a CNN - reducing the number of objects that need to be classified while still improving precision. The combined real-time system is implemented and evaluated on a two robots with very different GPU capabilities.
RGB-D sensors are relatively inexpensive and are commercially available off-the-shelf. However, owing to their low complexity, there are several artifacts that one encounters in the depth map like holes, mis-alignment...
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ISBN:
(纸本)9781628414899
RGB-D sensors are relatively inexpensive and are commercially available off-the-shelf. However, owing to their low complexity, there are several artifacts that one encounters in the depth map like holes, mis-alignment between the depth and color image and lack of sharp object boundaries in the depth map. Depth map generated by Kinect cameras also contain a significant amount of missing pixels and strong noise, limiting their usability in many computer vision applications. In this paper, we present an efficient hole filling and damaged region restoration method that improves the quality of the depth maps obtained with the Microsoft Kinect device. The proposed approach is based on a modified exemplar-based inpainting and LPA-ICI filtering by exploiting the correlation between color and depth values in local image neighborhoods. As a result, edges of the objects are sharpened and aligned with the objects in the color image. Several examples considered in this paper show the effectiveness of the proposed approach for large holes removal as well as recovery of small regions on several test images of depth maps We perform a comparative study and show that statistically, the proposed algorithm delivers superior quality results compared to existing algorithms.
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