Papers by Hossein Afshari
2013 IEEE International Conference on Industrial Technology (ICIT), 2013
Panoptic is a custom spherical light field camera used as a polydioptric system where imagers are... more Panoptic is a custom spherical light field camera used as a polydioptric system where imagers are distributed over a spherical geometry, each having its own vision of the surrounding and a distinct focal plane. The spherical light field camera records light information from any direction around its center. A novel Gaussian blending technique is presented for vision reconstruction of a virtual observer located inside the spherical geometry of this camera. This blending technique improves the output quality of the reconstructed image with respect to ordinary stitching techniques and simpler image blending algorithms. A hardware architecture based on Field Programmable Gate Arrays (FPGA) with the real-time implementation of the Gaussian blending algorithm using the spherical light field camera is presented, along with the imaging results.
IFIP Advances in Information and Communication Technology, 2015
The Panoptic camera is an omnidirectional multi-aperture visual system which is realized by mount... more The Panoptic camera is an omnidirectional multi-aperture visual system which is realized by mounting multiple imaging sensors on a hemispherical frame. In this chapter, we will present a novel distributed and parallel implementation of the real-time omnidirectional vision reconstruction algorithm of the Panoptic Camera, for camera modules with processing, memory and interconnectivity features. A methodology for the arrangement of camera modules with interconnectivity feature into a target interconnection network topology will be introduced. A unique custom-made multiple-FPGA hardware platform designed for the implementation of an interconnected network of a 49 camera prototype Panoptic system will be explained. A novel way to represent the omnidirectional data obtained from the Panoptic Camera and real-time high dynamic range (HDR) video application which is realized by the system will be presented.. .
Hardware implementation of an omnidirectional camerawith real-time 3D imaging capability
2011 3DTV Conference: The True Vision - Capture, Transmission and Display of 3D Video (3DTV-CON), 2011
Abstract A novel hardware implementation of an omnidirectional image sensor is presented which is... more Abstract A novel hardware implementation of an omnidirectional image sensor is presented which is capable of acquiring and processing 3D image sequences in real time. The system consists of a hemispherical arrangement of a large number of CMOS imagers, connecting to a layered arrangement of a high-end FPGA platform that is responsible data framing and image processing. The hardware platform in charge of real-time processing the 3.8 Gb/s data which is generated by the cameras is presented, and a first application of the system ...
Sensors, Cameras, and Systems for Industrial and Scientific Applications XIV, 2013
The real-time development of multi-camera systems is a great challenge. Synchronization and large... more The real-time development of multi-camera systems is a great challenge. Synchronization and large data rates of the cameras adds to the complexity of these systems as well. The complexity of such system also increases as the number of their incorporating cameras increases. The customary approach to implementation of such system is a central type, where all the raw stream from the camera are first stored then processed for their target application. An alternative approach is to embed smart cameras to these systems instead of ordinary cameras with limited or no processing capability. Smart cameras with intra and inter camera processing capability and programmability at the software and hardware level will offer the right platform for distributed and parallel processing for multicamera systems real-time application development. Inter camera processing requires the interconnection of smart cameras in a network arrangement. A novel hardware emulating platform is introduced for demonstrating the concept of the interconnected network of cameras. A methodology is demonstrated for the interconnection network of camera construction and analysis. A sample application is developed and demonstrated.
2012 IEEE Workshop on Signal Processing Systems, 2012
2012 15th Euromicro Conference on Digital System Design, 2012
Omnidirectional stereoscopy and depth estimation are complex problems of image processing to whic... more Omnidirectional stereoscopy and depth estimation are complex problems of image processing to which the Panoptic camera offers a novel solution. The Panoptic camera is a biologically-inspired vision sensor made of multiple cameras. It is a polydioptric system mimicking the eyes of flying insects where multiple imagers, each with a distinct focal point, are distributed over a hemisphere. Recently, the omnidirectional image reconstruction algorithm (OIR) and its real-time hardware implementation have been proposed for the Panoptic camera. This paper presents an enhanced omnidirectional image reconstruction algorithm (EOIR) and its real-time implementation. The proposed EOIR algorithm provides improved realistic omnidirectional images and residuals compared to OIR. As a processing core of EOIR, 57% of the available slice resources in a Virtex 5 FPGA are consumed. The proposed platform provides the high bandwidth required to simultaneously process data originating from 40 cameras, and reconstruct omnidirectional images of 256x1024 pixels at 25 fps. This proposed hardware and algorithmic enhancements enable advanced real-time applications including omnidirectional image reconstruction, 3D model construction and depth estimation.
A Real-time Multi-camera System with Omnidirectional Image Reconstruction Capability
A new plenoptic sensor inspired from the visual system of flying insects is introduced. This sens... more A new plenoptic sensor inspired from the visual system of flying insects is introduced. This sensor is referred to as the Panoptic camera. This system has two distinguished features. First, it is an omnidirectional camera capable of recording light information around it. Second, it is a polydioptric system where each CMOS facet has a distinct focal plane; hence the full system is a multiple aperture camera. An FPGA based solution is proposed for real time application deployment. The omnidirectional vision reconstruction algorithm of the Panoptic camera is elaborated and implemented in real time. A built system along with its captured results are presented. Panoptic device is targeted for applications such as depth map estimation, 3D cinematography, ego motion and reconstruction from motion.
IEEE Transactions on Circuits and Systems for Video Technology, 2015
Centralized and multilevel implementations of the Panoptic omnidirectional multiaperture visual s... more Centralized and multilevel implementations of the Panoptic omnidirectional multiaperture visual system were previously presented by us, relying on the transmission of all camera outputs to a single central processing node for omnidirectional image and video reconstruction. In this paper, a novel distributed and parallel implementation of the omnidirectional vision reconstruction algorithm of the Panoptic system is presented. The parallel approach aims to overcome the scalability problems and memory bandwidth limitations of the centralized approach. The real-time hardware implementation is presented for camera modules with image processing, memory, and interconnectivity features. A methodology is introduced for the arrangement of camera modules with interconnectivity feature into a target interconnection network topology. A unique custom-made multiple-field-programmable gate array hardware platform is introduced for the implementation of an interconnected network of 49 camera prototype Panoptic system. A hardware architecture based on presented hardware platform enabling the real-time implementation of the blending algorithms is presented, along with the imaging results and resource utilization. The realtime implementation results of the implemented omnivision application on the mentioned prototype are demonstrated.
Hemispherical Multiple Camera System for High Resolution Omni-Directional Light Field Imaging
IEEE Journal on Emerging and Selected Topics in Circuits and Systems, 2013
ABSTRACT
Design and Implementation of Multi-camera Systems Distributed over a Spherical Geometry
Lecture Notes in Computer Science, 2012
ABSTRACT
2014 IEEE Biomedical Circuits and Systems Conference (BioCAS) Proceedings, 2014
The massive amount of data recorded by dense electrode arrays which are routinely connected to Ny... more The massive amount of data recorded by dense electrode arrays which are routinely connected to Nyquistsampling signal conditioning blocks introduces new design challenges for implantable and wireless biological signal acquisition. Five different architectures of implantable multichannel neural recording systems are compared in terms of power and area constraints. Silicon results of a 16-channel spatial-domain compressive recording system implemented in a UMC 0.18 µm CMOS technology are presented. Applying intracranially recorded EEG signals, the proposed system achieves up to 16-times compression rate, consuming an extra compression power of 0.95 µW within a die area of 0.008 mm 2 per channel.
Journal of Signal Processing Systems, 2013
Panoptic is a custom spherical light field camera used as a polydioptric system where imagers are... more Panoptic is a custom spherical light field camera used as a polydioptric system where imagers are distributed over a hemispherical surface, each having its own vision of the surroundings and a distinct focal plane. The spherical light field camera records light information from any direction around its center. This paper revises previously developed Nearest Neighbor and Linear blending techniques. Novel Gaussian blending and Restricted Gaussian blending techniques for vision reconstruction of a virtual observer located inside the spherical geometry are presented. These new blending techniques improve the output quality of the reconstructed image with respect to the ordinary stitching techniques and simpler image blending algorithms. A comparison of the developed blending algorithms is also given in this paper. A hardware architecture based on Field Programmable Gate Arrays (FPGA) enabling the real-time implementation of the blending algorithms is presented, along with the imaging results and resource utilization comparison. A recorded omnidirectional video is attached as a supplementary material.
A spherical multi-camera system with real-time omnidirectional video acquisition capability
IEEE Transactions on Consumer Electronics, 2012
ABSTRACT
Journal of Signal Processing Systems, 2012
A new biologically-inspired vision sensor made of one hundred "eyes" is presented, which is suita... more A new biologically-inspired vision sensor made of one hundred "eyes" is presented, which is suitable for real-time acquisition and processing of 3-D image sequences. This device, named the Panoptic camera, consists of a layered arrangement of approximately 100 classical CMOS imagers, distributed over a hemi-This research has been partly conducted with the support of the Swiss NSF under grant number 200021-125651.
Friction stir welding (FSW) is a promising solid-state joining technique that allows the design o... more Friction stir welding (FSW) is a promising solid-state joining technique that allows the design of weight competitive assemblies with a minimum number of mechanical fasteners. In this paper, the joining of AA6061 (Al-Mg-Si) aluminum plates of 4 mm thickness was carried out by FSW. The FSW tool used was made from a rhenium-based tungsten carbide material with a cone probe and a concave shoulder. Microstructure analysis distinguished four distinct regions on the surface of the transverse cross-section of the FSW joint, namely unaffected parent material, heat affected zone (HAZ), thermo-mechanically affected zone (TMAZ) and weld nugget. Tensile test on the whole joint showed surprisingly that cracking started from TMAZ/HAZ interface. According to this observation, a model created to simulate the response of the joint under uniaxial tension. For this end, extended finite element method (XFEM) is invoked to estimate stress and strain fields around a minute virtual crack located in the TMAZ/HAZ interface. Critical load was evaluated using local strain energy density (SED) criterion. The SED criterion states that failure occurs when the mean value of the strain energy density over a well-defined control volume in the vicinity of the crack tip is equal to a critical energy. Mechanical properties in TMAZ/HAZ were idealized as continuous functions to be used for finding the outer boundary of the control volume. The predicted values of SED criterion was found in good agreement with experimental results.
Design and Implementation of Byte Wise Fashion Concatenated Encoder for DVB Systems
We presented a concatenated encoder design which is used for all digital video broadcast (DVB) ap... more We presented a concatenated encoder design which is used for all digital video broadcast (DVB) applications, no matter what the media of transfer is. It is composed of a scrambler, Reed-Solomon encoder, convolutional interleaver, and punctured convolutional encoder. Two novel architectures are provided for the scrambler and punctured convolutional encoder units to operate in a byte wise fashion. Thus any need for bit serial to parallel and parallel to bit serial module has been eliminated. Furthermore the minimum performance requirement of the concatenated encoder has been reduced by factor of eight. The power consumption of the byte wise fashion implementation compared to that of the standard implementation has also been reduced. For verification purposes the proposed design was implemented in FPGA and embedded in a DVB-terrestrial (DVB-T) modulator
A Novel Symbol Interleaver Address Generation Architecture for DVB-T Modulator
A new algorithm along with its hardware scheme has been proposed for consecutive generation of th... more A new algorithm along with its hardware scheme has been proposed for consecutive generation of the symbol addresses involved in the symbol interleaving process of a digital video broadcast terrestrial (DVB-T) standard modulator. Advantages achieved through the utilization of this architecture in a DVB-T modulator design outperforms the one presented in the DVB-T standard. Using this technique the large buffer
Proceedings of The Institution of Mechanical Engineers Part I-journal of Systems and Control Engineering, 2009
The current paper presents the determination of a closed-loop guidance law for an orbital injecti... more The current paper presents the determination of a closed-loop guidance law for an orbital injection problem using two different approaches and, considering the existing timeoptimal open-loop trajectory as the nominal solution, compares the advantages of the two proposed strategies. In the first method, named neighbouring optimal control (NOC), the perturbation feedback method is utilized to determine the closed-loop trajectory in an analytical form for the non-linear system. This law, which produces feedback gains, is in general a function of small perturbations appearing in the states and constraints separately. The second method uses an L 1 adaptive strategy in determination of the non-linear closedloop guidance law. The main advantages of this method include characteristics such as improvement of asymptotic tracking, guaranteed time-delay margin, and smooth control input. The accuracy of the two methods is compared by introducing a high-frequency sinusoidal noise. The simulation results indicate that the L 1 adaptive strategy has a better performance than the NOC method to track the nominal trajectory when the noise amplitude is increased. On the other hand, the main advantage of the NOC method is its ability to solve a non-linear, two-point, boundary-value problem in the minimum time.
A perturbation approach in determination of closed-loop optimal-fuzzy control policy for planetary landing mission
Proceedings of The Institution of Mechanical Engineers Part G-journal of Aerospace Engineering, 2009
ABSTRACT Development of time-optimal strategy for non-linear problem of planetary landing mission... more ABSTRACT Development of time-optimal strategy for non-linear problem of planetary landing mission by using perturbation technique is investigated on two scenarios in this study. The first scenario includes finding an optimal control policy for descent in the variable gravitational field of the target planet analytically. In the second scenario, the optimal policy is derived by considering the effect of spacecraft mass variations in an analytic solution. To validate the accuracy of each generated policy, a numeric method such as steepest descent is employed. Afterwards, the fuzzy algorithm is followed to achieve the closed-loop guidance strategy for this non-linear system. The training process of the fuzzy system is based on the achieved perturbation solution of variable mass landing problem by utilizing a set of states-related non-dimensional variables for faster convergence rate. Finally, the lunar landing mission is demonstrated as a viable example of the non-linear planetary landing mission. Simulation results show that the presented optimal guidance laws are so effective which can be utilized in the real world spacecraft applications.
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Papers by Hossein Afshari