Pierre Magnan

Near infrared thermography with silicon FPA - Comparison to MWIR and LWIR thermography

An ideal thermographic camera could be defined as an uncooled system with high spatial and thermal resolutions featuring a video frame rate, and a short calibration process. In this paper a measurement system based on Silicon FPA operating in the Near Infrared spectral band (0.7 - 1.1 µm) is proposed. This system offers an excellent spatial resolution, a low cost and compactness. With a specific radiometric model, this system can accurately measure temperatures, in a broad temperature range, from 400 up to 1000°C. A comparison with two commercial infrared cameras is performed between 400 and 700°C.

Development and characterization of active pixel sensors for space applications

Since 1993, research concerning CMOS APS (Active Pixel Sensors) has been intensively carried out, in order to offer an alternative to CCDs as an image sensor, particularly in space applications. Many laboratories have demonstrated the feasibility of these new devices and the high level of performances that can be achieved. Nowadays, the first generation of commercial devices becomes available for consumer electronics, and start to be used in many applications such as surveillance micro-cameras, video- conferencing, digital-still cameras. The latest designs have shown that APS is getting closer to the CCD in terms of performance level in scientific applications. APS device offers high potentialities for space applications (low power, low cost, high integration level), and fast improvements will make this sensors available for spacecraft: star tracker, planetary imaging functions, fine guidance sensor... A summary of APS benefits for space applications will be presented in this paper. Recently developed APS image sensors (128 X 128 and 256 X 256 pixels) designed by the Conception dImageurs Matriciels Integres (CIMI) group of SUPAERO and jointly tested by CIMI and Matra Marconi Space will be presented. The results demonstrate that standard CMOS process is well suited for image sensors implementation. The trade-off regarding the pixel detector choice (photoMos vs photodiode) will be discussed. Finally, future trends and perspectives for APS applications in space activities will be presented.

Research-grade CMOS image sensors for demanding space applications

Imaging detectors are key elements for optical instruments and sensors on board space missions dedicated to Earth observation (high resolution imaging, atmosphere spectroscopy...), Solar System exploration (micro cameras, guidance for autonomous vehicle...) and Universe observation (space telescope focal planes, guiding sensors...). This market has been dominated by CCD technology for long. Since the mid- 90s, CMOS Image Sensors (CIS) have been competing with CCDs for more and more consumer domains (webcams, cell phones, digital cameras...). Featuring significant advantages over CCD sensors for space applications (lower power consumption, smaller system size, better radiations behaviour...), CMOS technology is also expanding in this field, justifying specific R&D and development programs funded by national and European space agencies (mainly CNES, DGA, and ESA). All along the 90s and thanks to their increasingly improving performances, CIS have started to be successfully used for more and more demanding applications, from vision and control functions requiring low-level performances to guidance applications requiring medium-level performances. Recent technology improvements have made possible the manufacturing of research-grade CIS that are able to compete with CCDs in the high-performances arena. After an introduction outlining the growing interest of optical instruments designers for CMOS image sensors, this talk will present the existing and foreseen ways to reach high-level electro-optics performances for CIS. The developments of CIS prototypes built using an imaging CMOS process and of devices based on improved designs will be presented.

Development of a 750x750 pixels CMOS imager sensor for tracking applications

Solid-state optical sensors are now commonly used in space applications (navigation cameras, astronomy imagers, tracking sensors...). Although the charge-coupled devices are still widely used, the CMOS image sensor (CIS), which performances are continuously improving, is a strong challenger for Guidance, Navigation and Control (GNC) systems. This paper describes a 750x750 pixels CMOS image sensor that has been specially designed and developed for star tracker and tracking sensor applications. Such detector, that is featuring smart architecture enabling very simple and powerful operations, is built using the AMIS 0.5μm CMOS technology. It contains 750x750 rectangular pixels with 20μm pitch. The geometry of the pixel sensitive zone is optimized for applications based on centroiding measurements. The main feature of this device is the on-chip control and timing function that makes the device operation easier by drastically reducing the number of clocks to be applied. This powerful function allows the user to operate the sensor with high flexibility: measurement of dark level from masked lines, direct access to the windows of interest… A temperature probe is also integrated within the CMOS chip allowing a very precise measurement through the video stream. A complete electro-optical characterization of the sensor has been performed. The major parameters have been evaluated: dark current and its uniformity, read-out noise, conversion gain, Fixed Pattern Noise, Photo Response Non Uniformity, quantum efficiency, Modulation Transfer Function, intra-pixel scanning. The characterization tests are detailed in the paper. Co60 and protons irradiation tests have been also carried out on the image sensor and the results are presented. The specific features of the 750x750 image sensor such as low power CMOS design (3.3V, power consumption<100mW), natural windowing (that allows efficient and robust tracking algorithms), simple proximity electronics (because of the on-chip control and timing function) enabling a high flexibility architecture, make this imager a good candidate for high performance tracking applications.

COBRA: a CMOS space qualified detector family covering the need for many LEO and GEO optical instruments

Visible and NIR space imaging applications are today taking advantage from the availability of CMOS arrays offering excellent electro-optics performances thanks to the use of processes dedicated to imaging applications. Astrium and ISAE have developed a family of CMOS detector based on UMC 0.35 microns foundry from a sound R&T program which has enabled the design a wide toolbox and subsequent qualification of associated technology bricks. From these elements, many detectors were developed, among them a 2 Million pixels detector was fully space qualified in 2007. This will be one of the first CMOS detector operated in an operational mission on the geostationary orbit. The back-end processing of COBRA 2M was carried out to e2v technologies. e2v will also industrialize the multi linear sensor of the Multi Spectral Instrument of the low Earth orbit Sentinel 2 mission for which COBRA family was selected. Performances and qualification results will be presented in this paper as well as the development of test benches to improve accuracy and efficiency for extensive detectors characterisation and advanced technology works to extend the COBRA family capabilities.

Space optical instruments design optimisation thanks to CMOS image sensor technology

Today, both CCD and CMOS sensors can be envisaged for nearly all visible sensors and instruments designed for space needs. Indeed, detectors built with both technologies allow excellent electro-optics (EO) performances to be reached, the selection of the most adequate device being driven by their functional and technological features and limits. The first part of the paper shortly recalls how far CMOS Image Sensors (CIS) EO performances have been improved these last years. The second part reviews the advantages of CMOS technology for space applications, illustrated by examples of CIS developments performed by EADS Astrium and Supaéro/CIMI for current and short term coming space programs.

A visible and NIR multilinear array dedicated to Sentinel 2 Multi Spectral Imager

Sentinel 2 is an EU/ESA LEO Earth observation mission currently developed in the framework of Global Measurement Environment and Security (GMES) program. The associated Multi Spectral Imager instrument is equipped with about 230 mm length VNIR and SWIR Focal Plane Arrays, each one being made of twelve detectors mechanically butted in staggered configuration. Each elementary VNIR detector features tens spectral bands with 10m, 20m or 60m spatial sampling, ranging from about 430 to 900 nm. The devices are currently manufactured using a 0.35 μm CMOS process optimised for imaging application and already space qualified, thanks to Astrium COBRA family development. For each spectral band, minimum SNR corresponding to reference flux and maximum integration time is required. Maximum flux and minimum MTF are also specified. The photo detector charge to voltage conversion factors and geometrical shapes have therefore been adjusted band per band in order to meet all these competing specifications. In addition, a per pixel Correlated Double Sampling readout circuit has been implemented to cancel photodiode reset noise, providing mean total readout noise lower than 200μV, and the output voltage swing has been improved in view of maximizing the device dynamics. Black coating has been deposited between the simple or double lines of photo detectors in order minimizing straight light effects. After a description of the multi linear detector architecture and functionality, its main performances will be presented. The current status of the industrial development will also be depicted.