Alexandre Schmid

Compressive multichannel cortical signal recording

This paper presents a novel approach to acquire multichannel wireless intracranial neural data based on a compressive sensing scheme. The designed circuits are extremely compact and low-power which confirms the relevance of the proposed approach for multichannel high-density neural interfaces. The proposed compression model enables the acquisition system to record from a large number of channels by reducing the transmission power per channel. Our main contributions are the twofold. First, a CMOS compressive sensing system to realize multichannel intracranial neural recording is described. Second, we explain a joint sparse decoding algorithm to recover the multichannel neural data. The idea has been implemented at system as well as circuit levels. The simulation results reveal that the multichannel intracranial neural data can be acquired by compression ratios as high as four.

A spherical multi-camera system with real-time omnidirectional video acquisition capability

A multi-camera system inspired from the visual system of flying insects is introduced which is referred to as the Panoptic camera. In the Panoptic system each camera is mounted over a hemispherical geometry and has its own vision of surrounding and distinct focal direction. The Panoptic device finds application in the area of omnidirectional vision and 3D imaging. A systematic approach is presented for the coverage analysis and design guidelines of the Panoptic device. The presented approach enables the construction of arbitrary multi-camera systems based on the Panoptic principle. An implemented hardware architecture based on FPGA is introduced which is capable of real-time omnidirectional vision reconstruction. The implemented hardware is capable of live video streaming at a rate of 6.25M pixels per second and a maximum image resolution of 32M pixels per FPGA board.

Compressed look-up-table based real-time rectification hardware

Stereo image rectification is a pre-processing step of disparity estimation intended to remove image distortions and to enable stereo matching along an epipolar line. A real-time disparity estimation system needs to perform real-time rectification which requires solving the models of lens distortions, image translations and rotations. Look-up-table based rectification algorithms allow image rectification without demanding high complexity operations. However, they require an external memory to store large size look-up-tables. In this work, we present an intermediate solution that compresses the rectification information to fit the look-up-table into the on-chip memory of a Virtex-5 FPGA. The low-complexity decompression process requires a negligible amount of hardware resources for its real-time implementation. The proposed image rectification hardware consumes 0.28% of the DFF and 0.32% of the LUT resources of the Virtex-5 XCUVP-110T FPGA, it can process 347 frames per second for a 1024×768 pixels image resolution, and it does not need the availability of an external memory.

Real-Time FPGA Implementation of Linear Blending Vision Reconstruction Algorithm Using a Spherical Light Field Camera

A custom spherical light-field camera used as a polydioptricsystem where imagers are distributed over a spherical geometry, each having its own vision of the surrounding and distinct focal plane. The spherical light-field camera is also an omnidirectional camera which records light information fro many direction around its center. A novel linear 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 vision with respect to the ordinary stitching technique. A novel pixel gridding scheme is presented for rectangular displaying of the reconstructed vision induced from the spherical light field camera. This gridding technique preserve the correct size of objects when mapped on the spherical geometry of the Panoptic system. A hardware architecture based on FPGAs with the real-time implementation of the linear blending algorithm and the new pixel gridding scheme of the spherical light-field camera are presented along with imaging results.

Modeling Stressed MOS Oxides Using a Multiphonon-Assisted Quantum Approach—Part II: Transient Effects

Multifrequency charge pumping analysis has been performed using a multiphonon-assisted charge trapping model in the view of analyzing the oxide region in energy and position that can be characterized using charge pumping (CP) characterization. Transient phenomena observed during CP and ac characterization (hysteresis loops) have been modeled, and the role of out-of-equilibrium quasi-Fermi levels in proximity of the Si/SiO2 interface has been studied in detail.

Hemispherical Multiple Camera System for High Resolution Omni-Directional Light Field Imaging

Inspiration from light field imaging concepts has led to the construction of multi-aperture imaging systems. Using multiple cameras as individual apertures is a topic of high relevance in the light field imaging domain. The need for wide field-of-view (FOV) and high-resolution video for applications in areas of surveillance, robotics and automotive systems has driven the idea of omni-directional vision. Recently, the Panoptic camera concept has been presented that mimics the eyes of flying insects using multiple imagers. The Panoptic camera utilizes a novel methodology for constructing a spherically arranged wide FOV plenoptic imaging system whereas omni-directional image quality is limited by low resolution sensors. In this paper, a very-high resolution light field imaging and recording system inspired from the Panoptic approach is presented. Major challenges consisting of managing the huge amount of data as well as maintaining a scalable system are addressed. The proposed system is capable of recording omni-directional video at 30 fps with a resolution exceeding 9000 2400 pixels. The system is capable of capturing the surrounding light field in a FOV. This important feature opens the door to various post processing techniques such as quality-enhanced 3D cinematography, very high resolution depth map estimation and high dynamic-range applications which are beyond standard stitching and panorama generation.

Real-time hardware implementation of multi-resolution image blending

A novel real-time implementation of a multi-resolution image blending algorithm is presented in this paper. A multi-resolution decomposition of the input is used to blend multiple images at different scales. Processing time is shortened by designing a pipeline system. The proposed solution requires less hardware multipliers and is able to achieve very high operating frequencies, compared to the current designs. The presented hardware architecture is optimized to support multiple simultaneous video streams, and high frame rates at High-Definition (HD) resolutions.

Modeling Stressed MOS Oxides Using a Multiphonon-Assisted Quantum Approach—Part I: Impedance Analysis

Complementary MOS device electrical performances are considerably affected by the degradation of the oxide layers and Si/SiO2 interfaces. A general expression for electrically stressed MOS impedance has been derived and applied within the nonradiative multiphonon theory of carrier capture/emission at oxide defects. The capacitance and the conductance of aged MOS field-effect transistor oxides, and their dependences on bias voltage, temperature, and stress conditions have been investigated.