A high dynamic range image sensor with linear response based on asynchronous event detection

This paper investigates the potential of an image sensor that combines event-based asynchronous outputs with conventional integration of photocurrents. Pixels voltages can be read out following a traditional approach with a source follower and analog-to-digital converter. Furthermore, pixels have circuitry to implement Pulse Density Modulation (PDM) sending out pulses with a frequency that is proportional to the photocurrent. Both read-out approaches operate simultaneously. Their information is combined to render high dynamic range images. In this paper, we explain the new vision sensor concept and we develop a theoretical analysis of the expected performance in standard AMS 0.18mm HV technology. Moreover, we provide a description of the vision sensor architecture and its main blocksPeer reviewe

Review of ADCs for imaging

The aim of this article is to guide image sensors designers to optimize the analog-to-digital conversion of pixel outputs. The most common ADCs topologies for image sensors are presented and discussed. The ADCs specific requirements for these sensors are analyzed and quantified. Finally, we present relevant recent contributions of specific ADCs for image sensors and we compare them using a novel FOM. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use onlyPeer reviewe

A Rad-hard On-chip CMOS Charge Detector with High Dynamic Range

This article introduces a CMOS charge detector tailored for measuring ionizing radiation in a wide range of fluences. It represents an entirely on-chip solution based on capacitive sensing. It was fabricated using a standard 0.18 μm CMOS process and employs Metal-insulator-Metal (MiM) capacitor arrays to attain high matching, low leakage, and minimal process variations. The sensing area was radhardened with a post-CMOS layer of metal deposited with a Focus Ion Beam (FIB) that removes the use of external metallic plates. Experimental testing under the electron beam of a scanning electron microscope (SEM) demonstrated radiation hardness at energies up to 10 keV, with a very high dynamic range of up to 138 dB (externally adjustable), and with a sensitivity of 1.43 μV/e-. By harnessing the detection of relative charge variations instead of relying on absolute values, this approach proves highly suitable for particle event detection and facilitates future integrations compatible with the Address Event Representation (AER) communication protocol.Ministerio de Ciencia, Innovación y Universidades PGC2018-101538-A-I00, PID2021-128009OBC31, VERSO AT21_00096, P20_0120

Study, design, implementation, and test of VLSI retinae sensitive to spatial and temporal contrast

Memoria presentada por Juan Antonio Leñero Bardallo para optar al grado de Doctor por la Universidad de Sevilla en el Departamento de Electrónica y Electromagnetismo.La tesis describe dos sensores visuales AER (Address Event Representation) capaces de detectar el contraste espacial y temporal. Se tratan de dos sistemas de visión con inspiración biológica que tratan de emular el comportamiento de la retina humana. Al contrario de los sistemas de visión convencionales, los sistemas bioinspirados no están basados en frames. Ello posibilita que tengan una serie de ventajas inherentes, como el amplio rango dinámico, el bajo consumo y la alta velocidad. En el documento se explica el funcionamiento de dos sensores AER específicos para la detección de contraste espacial y temporal. Además, se muestran numerosos resultados experimentales. Como cunclusión, se muestra que para determinadas aplicaciones, como la detección de movimiento a alta velocidad, los sensores implementados ofrecen mejores características que los sistemas de visión convencionales que podemos encontrar en el mercado.Programa JAE (Junta para la Ampliación de Estudios) del CSIC para la formación de investigadores, gracias al cual he obtenido financiación para mi formación como doctor.Peer Reviewe

Thermography for the differential diagnosis of vascular malformations

This dataset contains thermographic and classic imaging modalities (Doppler ultrasonography and magnetic resonance) of low- and high-flow vascular malformations. In the file supplement_1, there is a comparative between alike low- and high-flow malformations in visible and the infrared band. Arrows indicate the exact localization of the malformation. Pictures on the top row correspond to a high-flow arteriovenous malformation and snapshots on the bottom row to a low-flow capillary malformation. In the visible spectrum, both malformations are quite similar and the diagnosis by simple visual inspection is challenging. However, thermal images are quite different. In the case of the high-flow malformation, there are high temperature variations in the hand (up to 1ºC). Moreover, the hemodynamic flow between both hands is completely different. The malformation creates an asymmetry on the bloods distribution. For the low-flow malformation, temperature variations are much less intense (lower than 0.3ºC). The hemodynamic flow between both hands is more homogeneous. Likewise, in file supplement_2 there is a similar comparative analysis between high- and low-flow malformations in the back. Images in the top row correspond to a high-flow arteriovenous malformation and images on the bottom row correspond to a low-flow one. Again, thermal images display remarkable temperature variations for the high-flow malformation and a more homogeneous temperature distribution for the low-flow malformation. In file supplement_3, we provide for the two previous high-flow arteriovenous malformations thermal images among other classic imaging modalities, i.e. Doppler ecography and magnetic resonance. Thermal images provide complementary information about temperature that can be crucial for an early classification of the malformation. In file supplement_4, there are snapshots of the custom imaging system developed for this research work. It has two cameras that operate simultaneously. One operates in the visible spectrum and the other one in the infrared band. The second camera can measure absolute temperature values after calibration. A LCD display is available to visualize data from the sensors

A calibration technique for very low current and compact tunable neuromorphic cells: Application to 5-bit 20nA DACs

Low current applications, like neuromorphic circuits, where operating currents can be as low as a few nanoamperes or less, suffer from huge transistor mismatches, resulting in around or less than 1-bit precisions. Recently, a neuromorphic programmable- kernel 2-D convolution chip has been reported where each pixel included two compact calibrated digital-to-analog converters (DACs) of 5-bit resolution, for currents down to picoamperes. Those DACs were based on MOS ladder structures, which although compact require unit transistors ( is the number of calibration bits). Here, we present a new calibration approach not based on ladders, but on individually calibratable current sources made with MOS transistors of digitally adjustable length, which require only -sized transistors. The scheme includes a translinear circuit-based tuning scheme, which allows us to expand the operating range of the calibrated circuits with graceful precision degradation, over four decades of operating currents. Experimental results are provided for 5-bit resolution DACs operating at 20 nA using two different translinear tuning schemes. Maximum measured precision is 5.05 and 7.15 b, respectively, for the two DAC schemes.This work was supported by Spanish Research Grants TEC2006-11730-C03-01 (SAMANTA2), TEC-417 (Brain System), and EU Grant IST-2001-34124 (CAVIAR). The work of J. A. Leñero-Bardallo was supported by the Spanish Ministry of Education and Science through an I3P national scholarship.Peer reviewe

A bioinspired 128x128 pixel dynamic-vision-sensor

Comunicación presentada al: "DCIS 2011, Sesion 4B: Biomedical Circuits"; celebrado en Albufeira (Portugal) del 16 al 18 de Noviembre del 2011.This paper presents a 128x128 dynamic vision sensor. Each pixel detects temporal changes in the local illumination. A minimum illumination temporal contrast of 10% can be detected. A compact preamplification stage has been introduced that allows to improve the minimum detectable contrast over previous designs, while at the same time reducing the pixel area by 1/3. The pixel responds to illumination changes in less than 3.6¿s. The ability of the sensor to capture very fast moving objects has been verified experimentally. A frame-based sensor capable to achieve this, would require at least 100K frames per second.This work has been supported by EU grant FP7-ICT-2007-1-216777 (NABAB), Spanish research grants (with support from the European Regional Development Fund) TEC2006-11730-C03-01 (SAMANTA2), TEC2009-10639-C04-01 (VULCANO), and Andalusian research project P06-TIC-1417 (Brain System). JALB was supported by the JAE program of the Spanish Research Council.Peer Reviewe

A 3.6 μ s latency asynchronous frame-free event-driven dynamic-vision-sensor

El pdf del artículo es la versión post-print.This paper presents a 128 × 128 dynamic vision sensor. Each pixel detects temporal changes in the local illumination. A minimum illumination temporal contrast of 10% can be detected. A compact preamplification stage has been introduced that allows to improve the minimum detectable contrast over previous designs, while at the same time reducing the pixel area by 1/3. The pixel responds to illumination changes in less than 3.6 μs. The ability of the sensor to capture very fast moving objects, rotating at 10 K revolutions per second, has been verified experimentally. A frame-based sensor capable to achieve this, would require at least 100 K frames per second.This work has been supported by EU grant FP7-ICT-2007-1-216777 (NABAB), Spanish research grants (with support from the European Regional Development Fund) TEC2006-11730-C03-01 (SAMANTA2), TEC2009-10639-C04-01 (VULCANO), and Andalusian research project P06-TIC-1417 (Brain System). JALB was supported by the JAE program of the Spanish Research Council.Peer reviewe

A spatial calibrated AER contrast retina with adjustable contrast threshold

Comunicación presentada al: "DCIS'09" celebrado en Zaragoza y organizado por la Universidad de Zaragoza (Unizar) del 18 al 20 de Noviembre del 2009.Address Event Representation (AER) is an emergent technology for assembling modular multi-blocks bio-inspired sensory and processing systems. Visual sensors (retinae) are among the first AER modules to be reported since the introduction of the technology. Spatial contrast AER retinae are of special interest since they provide highly compressed data flow without reducing the relevant information required for performing recognition. Reported AER contrast retinae perform a contrast computation based on the ratio between a pixel’s local light intensity and a spatially weighted average of its neighbourhood. This results in compact circuits, but with the penalty of all pixels generating output signals even if they sensed no contrast. In this paper we present a spatial contrast retina with bipolar output: contrast is computed as the relative difference between a pixel’s local light and its weighted spatial average. As a result, contrast includes a sign and the output will be zero if there is no contrast. Furthermore, an adjustable thresholding mechanism has been included, such that pixels remain silent until they sense an absolute contrast above the adjustable threshold. The pixel contrast computation circuit is based on Boahen’s Biharmonic operator contrast circuit, which has been improved to include mismatch calibration and adaptive current based biasing. As a result, the contrast computation circuit shows much less mismatch, is almost insensitive to ambient light illumination, and biasing is much less critical than in the original voltage biasing scheme. A full AER retina version has been fabricated. In the present paper we provide simulation and preliminary experimental results.This work was supported by EU grant 216777 (NABAB), Spanish grant TEC2006-11730-C03-01 (SAMANTA2) and Andalucian grant P06TIC01417 (Brain Systems). JA. Leñero-Bardallo was supported by a JAE scholarship.Peer Reviewe

Fire detection with a frame-less vision sensor working in the NIR band

This paper draws the attention of the community about the capabilities of an emerging generation of bio-inspired vision sensors to be used in fire detection systems. Their principle of operation will be described. Moreover experimental results showing the performance of an event-based vision sensor will be provided. The sensor was intended to monitor flames activity without using optic filters. In this article, we will also extend this preliminary work and explore how its outputs can be processed to detect fire in the environmentPeer reviewe