Guy Meynants

Random addressable 2048/spl times/2048 active pixel image sensor

In this paper, we discuss the design, design issues, fabrication, and performance of a 2048/spl times/2048 active pixel image sensor in a 0.5-/spl mu/m standard CMOS process. Each pixel, 7.5/spl times/7.5 /spl mu/m/sup 2/, consists of three transistors and a photo diode, resulting in a 12-million transistor chip with a die size of 16.3/spl times/16.5 mm. The pixel has a nonintegrating direct readout architecture, with a logarithmic light-to-voltage conversion. This allows the array to be fully random accessible, both in space and time. The sensor has eight analog outputs, each with a pixel rate of 4.5 MHz, which implies a maximum frame rate of eight full frames per second. Sub-sampling or windowing makes higher frame rates possible. The yield of the sensor is high if one accepts a small number of bad pixels.

Total dose and displacement damage effects in a radiation-hardened CMOS APS

A 512/spl times/512 CMOS active pixel sensor (APS) was designed and fabricated in a standard 0.5-/spl mu/m technology. The radiation tolerance of the sensor has been evaluated with Co-60 and proton irradiation with proton energies ranging from 11.7 to 59 MeV. The most pronounced radiation effect is the increase of the dark current. However, the total ionizing dose-induced dark current increase is orders of magnitude smaller than in standard devices. It behaves logarithmically with dose and anneals at room temperature. The dark current increase due to proton displacement damage is explained in terms of the nonionizing energy loss of the protons. The fixed pattern noise does not increase with total ionizing dose. Responsivity changes are observed after Co-60 and proton irradiation, but a definitive cause has not yet been established.

Random addressable active pixel image sensors

In this article we discuss the trade-offs for the design, fabrication and interfacing of fast pixel addressable (random-access) cameras. In order to benefit most from the random addressability, the interface must be optimized for access through a data bus/address bus structure. Measures to correct the cameras inherent non-uniformity must not slow down the interface speed.

Time-Delay-Integration Architectures in CMOS Image Sensors

Difficulty and challenges of implementing time-delay-integration (TDI) functionality in a CMOS technology are studied: synchronization of the samples forming a TDI pixel, adder matrix outside the array, and addition noise. Existing and new TDI sensor architecture concepts with snapshot shutter, rolling shutter, or orthogonal readout are presented. An optimization method is then introduced to inject modulation transfer function and quantum efficiency specification in the architecture definition. Moderate spatial and temporal oversamplings are combined to achieve near charge-coupled device (CCD) class performances, resulting in an acceptable design complexity. Finally, CCD and CMOS dynamic range and signal-to-noise ratio are conceptually compared.

A 2.2M CMOS image sensor for high-speed machine vision applications

This paper describes a 2.2 Megapixel CMOS image sensor made in 0.18 μm CMOS process for high-speed machine vision applications. The sensor runs at 340 fps with digital output using 16 LVDS channels at 480MHz. The pixel array counts 2048x1088 pixels with a 5.5um pitch. The unique pixel architecture supports a true correlated double sampling, thus yields a noise level as low as 13 e- and a pixel parasitic light sensitivity (PLS) of 1/60 000. The sensitivity of the sensor is measured to be 4.64 Vlux.s and the pixel full well charge is 18k e-.

Project SVAVISCA: a space-variant color CMOS sensor

The paper describes the result of the first phase of the ESPRIT LTR project SVAVISCA. The aim of the project was to add color capabilities to a previously developed monochromatic version of a retina-like CMOS sensor. In such sensor, the photosites are arranged in concentric rings and with a size varying linearly with the distance from the geometric center. Two different technologies were investigated: 1) the use of Ferroelectric Liquid Crystal filters in front of the lens, 2) the deposition of color microfilters on the surface of the chip itself. The main conclusion is that the solution based on microdeposited filters is preferable in terms of both color quality and frame rate. The paper will describe in more detail the design procedures and the test results obtained.

Real-time, miniaturized optical sensor for motion estimation and time-to-crash detection

The paper presents a low cost, miniature sensor that is able to compute in real time (up to 1000 frames/sec) motion parameters like the degree of translation, expansion or rotation that is present in the observed scene, as well as the so-called time-to-crash (TTC), that is the time required for a moving object to collide with the sensor. The sensing principle is that of computing and analyzing the optical flow projected by the scene on the sensor focal plane, through a novel algorithmic technique, based on sparse sampling of the image and one-dimensional correlation. The hardware implementation of the algorithm is based on two custom VLSI chips: one is a CMOS image sensor, having nonstandard pixel geometry, while the other one is a digital correlator that computes at high speed the optical flow vectors. The high-level control and communication tasks are managed by a microcontroller, thus guaranteeing a high level of flexibility and adaptability of the sensor properties towards different application requirements and/or variable external conditions.

Characterization of Backside-Illuminated CMOS APS Prototypes for the Extreme Ultraviolet Imager On-Board Solar Orbiter

For the Extreme Ultraviolet Imager (EUI) of the Solar Orbiter mission, to be launched in 2017, CMOS active pixel sensor (APS) prototypes have been developed with several test pixel designs. A set of measurements was carried out to evaluate their performance characteristics in visible and in extreme ultraviolet wavelengths. We present the results of measurement campaigns that lead to the selection of a preferred pixel design in regard to the scientific performance requirements of the EUI flight model detectors, i.e., back-thinned CMOS APS devices of 2048 × 2048 and 3072 × 3072 pixel formats with a 10-μm pixel pitch.

1024×1280-pixel dual shutter APS for industrial vision

We present a 1.3 megapixel CMOS active pixel sensor dedicated to industrial vision. It features both rolling and synchronous shutter. Full frame readout time is 33 ms, and readout speed can be boosted by windowed region of interest (ROI) readout. High dynamic range scenes can be captured using the double and multiples slope functionality. All operation modes and settings can be programmed over a serial or a parallel interface.

Analogue-domain FPN compensation circuit for random access CMOS imagers

Random access active pixel CMOS image sensors generally suffer from non-uniformity in their pixel outputs. This document describes a simple mixed analogue-digital integrated circuit for fixed-pattern-noise compensation. The method has been applied to the range of sensors developed by IMEC, and improves their operation beyond mere static noise suppression.