Proceedings Volume 5251

Detectors and Associated Signal Processing

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Proceedings Volume 5251

Detectors and Associated Signal Processing

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Volume Details

Date Published: 19 February 2004
Contents: 6 Sessions, 36 Papers, 0 Presentations
Conference: Optical Systems Design 2003
Volume Number: 5251

Table of Contents

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Table of Contents

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  • Opto Detectors
  • IR Cooled Detectors
  • IR Uncooled Detectors
  • Silicon Detectors
  • FPA Signal Processing and Applications
  • Posters
  • FPA Signal Processing and Applications
Opto Detectors
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Retro-prospective in IR optical detectors
Daniel Esteve, Francis Bony, Christophe Escriba, et al.
This presentation looks back over this last twenty years, the French activity in IR detectors. Photon and thermal detectors, cooled and uncooled focal plane arrays are considered. Two specific experiences are described on Automation Home IR Systems and Earth horizon IR sensing for Space Applications. The discussion is focussed on low cost devices and perspectives which are to be open in obstacle detection for Automotive Applications.
IR Cooled Detectors
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MCT linear arrays and associated silicon readouts
Fiodor F. Sizov, Yurii P. Derkach, S. A. Dvoretski, et al.
MCT 2×64 and 4×288 linear arrays with silicon readouts were designed, manufactured and tested. (013) MCT MBE layers were grown on GaAs substrates with ZnTe and CdTe buffer layers. 2×64 arrays were also manufactured on the base of LPE layers on CdZnTe (111) substrates. 50×55 and ≈30×30 μm area n-p-type photodiodes were formed by 50 ÷ 120 keV boron implantation. The dark currents at V ≈ 100 mV reversed biased diodes used in arrays with cutoff wavelength λco ≈ 10.0 - 12.2 μm were within 15 - 50 nA and zero bias resistance-area products were within R0A ≈ 5 ÷ 20 Ohm×cm2. Designed silicon readouts with skimming and partitioning functions were manufactured by n-channel MOS technology with buried or surface channel CCD register. For achievement with the silicon readouts the deselection function, the “composite” technology approach was considered. In this case both the technology of n-channel CCD and CMOS technology were applied, which allow to weaken considerably the technological design rules for realization of 288×4 readouts with deselection of “dead” elements. It is shown that 2.5 μm design rules for CCD and 2.0 design rules for CMOS technologies allow to realize most of the functions needed for 288×4 MCT array operation with deselection function. Before hybridisation the parameters of MCT linear arrays and Si readouts were tested separately. HgCdTe arrays and Si readouts were hybridised by cold welding In bumps technology. In dependence of FOV with skimming mode used for integration time of 8 - 20 μs detectivities within D*λ (0.4 - 1.7)×1011 cm×Hz1/2/W were achieved in dependence of the array format. Dark carrier transport mechanisms in MCT diodes were calculated and compared with experimental data.
Cooled large IR staring arrays: toward third generation
SOFRADIR has moved to large quantity production for 2.5 generation IR detectors (320x256 format) since 2001. The move from 2nd generation to 2.5-generation IR detectors, mainly for MWIR applications, has been successfully achieved at SOFRADIR thanks to improvements of the technologies fully dedicated to performance improvements as well as production capacity increase for staring arrays. Then, in order to prepare future military and industrial needs, SOFRADIR has been working in close relationship with CEA-LETI/LIR on third generation development based on HgCdTe materials. This effective approach has been one of the keys to success in preparing third generation IR detectors. Three main areas are investigated for the third generation IR detectors: large IRFPA manufacturing following a cost effective approach, development of new IR detector structures and design of new silicon readout circuits. Developments in progress are presented regarding these main areas.
High-performance IR detector modules
The 3rd generation of infrared (IR) detection modules is expected to provide higher video resolution, advanced functions like multi band or multi color capability, higher frame rates, and better thermal resolution. AIM has developed staring and linear high performance focal plane arrays (FPA) integrated into detector/dewar cooler assemblies (IDCA). Linear FPA’s support high resolution formats such as 1920 x 1152 (HDTV), 1280 x 960, or 1536 x 1152. Standard format for staring FPA’s is 640 x 512. In this configuration, QEIP devices sensitive in the 8 - 10 µm band as well as MCT devices sensitive in the 3.4 - 5.0 µm band are available. A 256 x 256 high speed detection module allows a full frame rate >800 Hz. Especially usability of long wavelength devices in high performance FLIR systems does not only depend on the classical electrooptical performance parameters such as NEDT, detectivity, and response homogeneity, but are mainly characterized by the stability of the correction coefficients used for image correction. The FPA’s are available in suited integrated detector/dewar cooler assemblies. The linear cooling engines are designed for maximum stability of the focal plane temperature, low operating temperatures down to 60K, high MTTF lifetimes of 6000h and above even under high ambient temperature conditions. The IDCA’s are equipped with AIM standard or custom specific command and control electronics (CCE) providing a well defined interface to the system electronics. Video output signals are provided as 14 bit digital data rates up to 80 MHz for the high speed devices.
SOFRADIR IR detectors for LW applications
SOFRADIR is one of the leading companies worldwide for the production of second-generation InfraRed (IR) detectors based on more than 10,000 Time Delay and Integration (TDI) array deliveries up to date! This success is mainly due to the top quality of the unique and production oriented French HgCdTe technology for manufacturing InfraRed Focal Plane Arrays (IRFPA). Although it is easy to get an image with 2D staring arrays in comparison with TDI linear arrays, it is more difficult to answer the full system needs in terms of high performances in very tough environmental conditions. However, cooled 2D arrays are more and more used in both IR medium and long wavebands for many different applications and SOFRADIR has moved to large quantity production for 2.5 generation IR detectors (320×256 format) since 2001. Then different technologies are available for answering LW staring arrays needs and SOFRADIR offers a large range of IR staring arrays for LW applications.
Infrared negative luminescent devices and higher operating temperature detectors
Infrared LEDs and negative luminescent devices, where less light is emitted than in equilibrium, have been attracting an increasing amount of interest recently. They have a variety of applications, including as a 'source’ of IR radiation for gas sensing; radiation shielding for and non-uniformity correction of high sensitivity starring infrared detectors; and dynamic infrared scene projection. Similarly, IR detectors are used in arrays for thermal imaging and, discretely, in applications such as gas sensing. Multi-layer heterostructure epitaxy enables the growth of both types of device using designs in which the electronic processes can be precisely controlled and techniques such as carrier exclusion and extraction can be implemented. This enables detectors to be made which offer good performance at higher than normal operating temperatures, and efficient negative luminescent devices to be made which simulate a range of effective temperatures whilst operating uncooled. In both cases, however, additional performance benefits can be achieved by integrating optical concentrators around the diodes to reduce the volume of semiconductor material, and so minimise the thermally activated generation-recombination processes which compete with radiative mechanisms. The integrated concentrators are in the form of Winston cones, which can be formed using an iterative dry etch process involving methane/hydrogen and oxygen. We will present results on negative luminescence in the mid and long IR wavebands, from devices made from indium antimonide and mercury cadmium telluride, where the aim is sizes greater than 1cm x 1cm. We will also discuss progress on, and the potential for, operating temperature and/or sensitivity improvement of detectors, where very higher performance imaging is anticipated from systems which require no mechanical cooling.
Megapixel HgCdTe MWIR focal plane array with a 15-um pitch
Pierre Castelein, Francois Marion, Jean-Luc Martin, et al.
In this paper we present the first demonstration at LETI infrared laboratory of a megapixel HgCdTe MWIR focal plane array with a 15μm pitch. The detectors were interconnected by indium bumps to the CMOS readout circuit. The design of these interconnections has been adapted from the standard CEA-LETI process to achieve resolution and uniformity required by the reduced pitch: the indium bumps scale 12μm width and 7μm height. Because of the important mechanical constraints induced by the size of the component, specific developments were necessary in order to achieve the hybridization process with an extremely reduced amount of defaults. The readout circuit was designed in a 3.3V /0.35μm CMOS technology. Its main features were to allow the validation of the hybridization and technological processes. A Megapixel IRCMOS has been mounted in a dewar and fully characterized at 77K exhibiting excellent electro-optical performances and an operability greater than 99.8%.
Highly sensitive large-area bolometers for scintillation studies below 100 mK (from near IR to soft x rays)
Noel Jean Coron, Pierre de Marcillac, Jacques Leblanc, et al.
At very low temperature large area bolometers may show a better sensitivity than photomultipliers or semiconductor diodes, while allowing fluorescence measurements of cool targets with no window, no infrared background, good optical couplings and a flat response on a large absorption bandpass. The optical absorber of these composite bolometers can be matched to the desired bandpass. Here we present the design, the performances and calibration tests of a new generation of large area (5 cm2) optical bolometers with a pure germanium disk absorbing on a wide spectral band from near-IR to X-rays. Performances obtained at 25 mK are very promising : Noise Equivalent Power as low as 4x10-17 W/√Hz in the photometry mode, energy threshold about 50 eV in the single photon detection mode, and time constant τ~3 ms. These detectors of low mass (0.25 g) have been recently successfully used for detecting the fluorescence emitted by much more massive bolometers, having for example a BGO (92 g), or a CaWO4 (54 g) target. The simultaneous detection of heat and light in these <> permits the identification of each event in the massive target (α decay, or γ cosmic ray interaction, neutron recoil...). Thanks to the consecutive excellent subtraction of the radioactive and cosmic rays background, it is a powerful tool developed by several groups for fundamental research : study of very rare decays of atoms, measurement of internal very low radioactivity content in single crystals, direct detection of dark matter recoils in massive fluorescence targets, detection of solar neutrino fluorescence events in liquid 4He...Recently obtained results which support this new promising field are reminded: the first detection of the rare alpha decay of 209Bi, and new scintillation data on Al2O3 (sapphire), LiF or TeO2 at 20mK. We discuss the ultimate performances at 12 mK of the optical bolometers as a function of their area, as well as the optimisation of their absorbing part to the desired bandpass, and finally, we estimate achievable improvements of our current technology.
IR Uncooled Detectors
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Developments of uncooled infrared detectors at the Kunming Institute of Physics
Chaoguang Pu, Yunjian Tai, Huisong Jin, et al.
Kunming Institute of Physics (KIP) had launched its project for uncooled infrared detectors from 1995. Uncooled infrared detector technology in KIP has progressed from the initial hybrid architecture, evolved through developments and now moved up to a new generation of monolithic architecture. In this paper, the history and developments of uncooled infrared detectors in KIP are briefly described.
Room temperature spectrometry in the MIR range
Reynald Passerini, Markus Kohli, Peter Ryser, et al.
Simple solutions for spectra acquisition in the MIR range have been studied in order to develop analysis systems for various process control and safety applications. The detection unit is a 64-pixel linear detector (μray 64, IR Microsystems), based on pyroelectric thin film technology. This detector exhibits a high signal to noise ratio at room temperature and therefore is ideal for the production of rugged, low cost and simple to use mini-spectrometers. We combined various technologies, including dispersive optics (gratings) and linear variable filters (LVF), with the μray 64 detector to build small spectral engines. These devices have been tested and their characteristics will be discussed in terms of sensitivity, resolution and costs.
Process technology to integrate polycrystalline uncooled PbSe infrared detectors on interference filters
A technology to process uncooled polycrystalline PbSe IR detectors on interference filters has been developed. Thus, the lead salt natural spectral response can be modified as required. PbSe is deposited, processed and sensitized, following a unique method, on an interference filter made up of a sapphire or silicon substrate and a Ge/SiO multilayer structure. Unlike standard polycrystalline PbSe processing methods, we deposit PbSe by sublimation in vacuum. As-deposited, PbSe is not sensitive to infrared light. In order to turn it photosensitive it is necessary to expose the films to specific thermal treatments. We have developed a very efficient sensitization process during which substrates are submitted to temperatures as high as 450 ºC. In this work we demonstrate that we are able to process a PbSe detector directly on top of an interference filter. Also, we present preliminary results regarding the compatibility of our technology with standard photolithography and dry etch techniques. Results obtained pave the way for the development of uncooled multicolor medium-wave infrared detectors.
Design and fabrication of InAsSb detectors
Mathieu Carras, Gabrielle Marre, Borge Vinter, et al.
A study of the optimisation of the detectivity of a mid infrared double heterostructures photovoltaic detector is proposed. Simple approximate analytic expressions for the dark current are compared with full numerical calculations, and give physical insight on the mechanisms dominating the dark current. The analysis is performed step by step in different structures, from a simple p-n junction to the full double heterostructures. The influence of temperature, barrier band gap energy and absorbing layer thickness in a double heterostructures, doping density in the active region on diffusion and generation-recombination mechanisms is analysed.
320x240 uncooled microbolometer 2D array for radiometric and process control applications
Bruno Fieque, Arnaud Crastes, Jean-Luc Tissot, et al.
Uncooled infrared focal plane arrays are being developed for a wide range of thermal imaging applications. Developments are focused on the improvement of their sensitivity enabling the possibility to manufacture high performance radiometric devices with internal temperature stabilized shield to determine precisely the input infrared flux. We present the characterization of a new radiometric device obtained from 320 x 240 uncooled microbolometer array with f/1.4 aperture. This device is well adapted to radiometric or process control applications and moreover shows a high level of stability due to the internal temperature stabilized shield which prevents the detector from camera internal temperature shift artifacts.
Pyroelectric infrared detectors based on lithium tantalate: state of art and prospects
This paper gives an overview of the most important results obtained in the development of pyroelectric single-element detectors and arrays (up to 256 responsive elements) at the Institute for Solid-State Electronics at the Dresden University of Technology. Since the late 1970s, the Institute has been carrying out a wide range of research and development work in this area. This work aimed at the development of sensor technologies which allow the construction and cost-efficient manufacturing of long-term stable detectors with a high signal-to-noise ratio. It is shown that a flexible sensor technology has been developed on the basis of lithium tantalate (LiTaO3) which allows to adjust the detector layout and its properties to the planned application in the best possible way. This applies to the number and geometry of the responsive elements and also to the spectral responsitivity, the noise and the spatial resolution of the detectors.
Low-cost amorphous silicon-based 160x120 uncooled microbolometer 2D array for high-volume applications
Cyrille Trouilleau, Arnaud Crastes, Jean-Luc Tissot, et al.
Uncooled infrared focal plane arrays are being developed for a wide range of thermal imaging applications. Developments are focused on the improvement of their sensitivity enabling the possibility of reducing the pixel pitch in order to decrease the total system (size and weight) by using smaller optics. The amorphous silicon technology is the latest one developed by CEA / LETI and transferred to ULIS to manufacture 160 x 120 2D arrays. We developed for this device a low cost package based on existing technologies. This device is well adapted to high volume process control applications where spatial resolution (in terms of pixel number) is less important than device costs.
Focal plane array for the GERB instrument
Nick Nelms, Gillian I. Butcher, Oliver Blake, et al.
The Geostationary Earth Radiation Budget (GERB) instrument is an Earth observing scientific payload launched on-board the European Space Agency Meteosat Second Generation (MSG) satellite in September 2002. The instrument measures reflected and emitted radiation in two wavebands, 0.3 - 4 μm and 4 - 30 μm. The focal plane consists of a 256-element thermoelectric linear array operating at ~300 K and four application specific integrated circuits (ASIC) providing parallel amplification, filtering and digitisation. This paper describes in detail the design, operation and performance of the GERB focal plane array.
Silicon Detectors
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CCD and APS/CMOS technology for smart pixels and image sensors
The relentless progress of semiconductor technology makes it possible to provide image sensors and pixels with additional analog and digital functionality. Growing experience with such photosensor functionality leads to the development of modular building blocks that can be employed for smart pixels, single-chip digital cameras and functional image sensors. Examples given include a non-linear pixel response circuit for high-dynamic range imaging offering a dynamic range of more than 180 dB, low-noise amplifiers and avalanche-effect pixels for high-sensitivity detection performance that approaches single-photoelectron resolution, lock-in pixels for optical time-of-flight range cameras with sub-centimeter distance resolution and in-pixel demodulation circuits for optical coherence tomography imaging. The future is seen in even higher levels of integration, such as system-on-a-chip machine vision cameras (“seeing chips”), post-processing with non-silicon materials for the extension of the detection range to the X-ray, ultraviolet and infrared spectrum, the exploitation of all properties of the incident light and imaging of fields other than electromagnetic radiation
CMOS optical detector system for capillary fluorescence measurements
Jean-Marc Galvan, Guo-Neng Lu, Patrick Pittet, et al.
We present a fluorescence detection system for capillary analysis. It is designed using a CMOS BDJ (Buried Double p-n Junction) detector which can be operated either as a photodiode or as a wavelength-sensitive device. Noise-reduction techniques such as signal pre-amplification and synchronous detection are implemented to boost the sensitivity of measurements. The system indicates fluorescence intensity for concentration determination, and average wavelength of fluorescence spectrum for molecular discrimination. The system has been tested by measuring two widely used fluorophores (FITC and Rhodamine B) in different concentrations. A 407-nm blue laser diode and a 532-nm green YAG compact laser have been respectively employed for their excitation. The illuminated volume inside the capillary is about 5 nl. The best results have been obtained with FITC, enabling as low as 10-10 M to be detectable.
CMOS photodetection system with variable-time synchronous detection
Patrick Pittet, Guo Neng Lu, Michel Pitaval, et al.
For sensitive fluorescence detection requiring weak signal recovery, we propose a novel digital synchronous detection method. It is based on a voltage/time duality concept which, compared to a conventional approach, consists of transformation of constant sampling rate with voltage measurement into variable-time sampling with constant threshold voltage. This Variable-Time Synchronous Detection (VTSD) method ensures a constant SNR over a large dynamic range, with optimised measuring rate. It can be implemented without any precise analogue-to-digital converter. A CMOS photodetection system with implementation of this VTSD method together with charge amplification is designed and tested. The results confirm its ability to recover photocurrent signals at femto-Ampers levels.
Monolithic diffractive interference detector on silicon
Yves Jourlin, Stephanie Reynaud, Nathalie Destouches, et al.
The presented interference detector comprises a standard pn junction in a silicon substrate and a corrugation grating engraved at its surface. Two beams with unknown phase difference impinge onto the detector under the Littrow condition for some diffraction order of the grating. The detected power exhibits a non-zero AC component as the relative phase between the incident beams changes. The present paper describes the operation principle and brings the evidence of non-zero interference contrast in the application case of a displacement sensor.
Analysis and potentialities of backside-illuminated thinned CMOS imagers
Cecilia Marques Vatus, Pierre Magnan
CMOS imagers, now considered as a valuable alternative to CCD in many application fields, have their quantum efficiency reduced by optical filtering effects due to complex top layers structure and limited fill factor. Thinning and backside illumination (BI) have been successfully applied to CCD image sensor to improve their quantum efficiency. It can potentially be similarly applied to CMOS imagers in an attempt to allow, both the increase of impinging photons number on the photosensitive area through the suppression of top layers stack filtering, and the use of a maximal fill factor value, the whole backside surface being photosensitive. But, it has to take into account the specific features of CMOS process, mostly the limited EPI thickness in the case of the heavily doped substrate option.
Source follower noise limitations in CMOS active pixel sensors
CMOS imagers are commonly employing pinned photodiode pixels and true correlated double sampling to eliminate kTC noise and achieve low noise performance. Low noise performance also depends on optimisation of the readout circuitry. This paper investigates the effect of the pixel source follower transistor on the overall noise performance through several characterization methods. The characterization methods are described, and experimental results are detailed. It is shown that the source follower noise can be the limiting factor of the image sensor and requires optimisation.
Photodetector with giant internal current amplification: experiment and numerical calculated model
Aleksandr Malik, Volodymyr Grimalsky, Alfonso Jacome Torres, et al.
New silicon based optical sensors with a metal - insulator - semiconductor structure (MIS) are developed and investigated both theoretically and experimentally. The physical properties of these sensors are described with a model of MIS capacitor where a presence of depletion layer of electrons and an inversion layer of holes of a finite depth is taken into account. Two-level voltage bias provides a transient between two quasi-equilibrium inversion modes. This transient is applied both for storage and for readout of the input optical signal for quantitative measurements of a weak infra red radiation. Proposed simple readout procedure provides reading the integrated information with a significant amplification. The amplification (or the current transformation coefficient) is determined by the ratio of integration and readout times and it may exceed 104. A theoretical model is given to explain a behavior of the sensor under storage by thermo generated carries and by photo generated ones jointly. Numerical simulations are of an agreement with experimental investigations of proposed sensors.
Three-dimensional CMOS image sensor with 4x64 pixel array
Omar M. Elkhalili, Olaf Schrey, Ralf F. Jeremias, et al.
A 3D CMOS imager based on time-of-flight (TOF) has been developed and successfully tested. It uses an active pulsed class 1 laser operating at 905nm to illuminate a 3D scene. The scene depth is determined by measurement of the travel time of reflected pulses by employing a fast on-chip synchronous shutter. A so-called “Multiple Double Short Time Integration” (MDSI) enables suppression of the background illumination and correction for reflectivity variations in the scene objects. The sensor chip contains 2 pixel lines with each pixel containing twin photodiodes, thus the chip contains 4×64 sensors. The chip allows two operating modes; the first is the binning mode (mode0 and mode1 are activated), where the twin pixels are short-circuited (tow lines on the die) and the average signal is measured. The second mode is the high-resolution mode (either mode0 or mode1 is activated). In this mode the pixels operate separately (four lines on the die). The chip has been realized in 0.5μm n-well standard CMOS process. The pixel pitch is 130μm. To get a good fill factor, the readout circuitry is located at the sides of the chip.
CMOS detector with combined in-situ demodulation and image acquisition
Ingo Hehemann, Werner Brockherde, Armin Kemna, et al.
All optoelectronic detectors today are based either on integrating or demodulating readout approaches. In this paper we introduce an optical detector that in-situ combines these two readout methods thus enabling simultaneous demodulation and image acquisition of the impinging light signal. Measurement results of a realized chip for optical storage systems with six demodulating paths and a 5x5 matrix of integrating pixels are presented. Furthermore, approaches for system integration of the novel architecture in the field of optical storage and fibre transmission systems are described.
New package for CMOS sensors
Jean-Luc Diot, Kum Weng Loo, Jean-Pierre Moscicki, et al.
Cost is the main drawback of existing packages for C-MOS sensors (mainly CLCC family). Alternative packages are thus developed world-wide. And in particular, S.T.Microelectronics has studied a low cost alternative packages based on QFN structure, still with a cavity. Intensive work was done to optimize the over-molding operation forming the cavity onto a metallic lead-frame (metallic lead-frame is a low cost substrate allowing very good mechanical definition of the final package). Material selection (thermo-set resin and glue for glass sealing) was done through standard reliability tests for cavity packages (Moisture Sensitivity Level 3 followed by temperature cycling, humidity storage and high temperature storage). As this package concept is new (without leads protruding the molded cavity), the effect of variation of package dimensions, as well as board lay-out design, are simulated on package life time (during temperature cycling, thermal mismatch between board and package leads to thermal fatigue of solder joints). These simulations are correlated with an experimental temperature cycling test with daisy-chain packages.
FPA Signal Processing and Applications
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Modeling of a 3D CMOS sensor for time-of-flight measurements
Rico Kuhla, Bedrich J. Hosticka, Peter Mengel, et al.
A solid state 3D-CMOS camera system for direct time-of-flight image acquisition consisting of a CMOS imaging sensor, a laser diode module for active laser pulse illumination and all optics for image forming is presented, including MDSI & CDS algorithms for time-of-flight evaluation from intensity imaging. The investigation is carried out using ideal and real signals. For real signals the narrow infrared laser pulse of the laser diode module and the shutter function of the sensors column circuit were sampled by a new sampling procedure. A discrete sampled shutter function was recorded by using the impulse response of a narrow pulse of FWHM=50ps and an additional delay block with step size of Δτ = 0.25ns. A deterministic system model based on LTI transfer functions was developed. The visual shutter windows give a good understanding of differences between ideal and real output functions of measurement system. Simulations of shutter and laser pulse brought out an extended linear delay domain from MDSI. A stochastic model for the transfer function and photon noise in time domain was developed. We used the model to investigate noise in variation the laser pulse shutter configuration.
Fast MTF measurement of CMOS imagers using ISO 12333 slanted-edge methodology
Magali Estribeau, Pierre Magnan
The ISO 12233 standard provides a fast and efficient way of measuring Modulation Transfer Function (MTF) of digital input devices (such a digital still camera) using a normalized reflective target based on a slanted-edge method. A similar methodology has been applied for measuring MTF of CMOS image sensors, using 12233 slanted-edge technique associated with a prototype transmissive target. In order to validate the results, comparisons have been made between MTF measurements of image sensor implemented using a 0.25 μm process, using this method and sine target direct measurements.
CCDs for the rotational velocity spectrometer on GAIA
Andrew D. Holland, Mark S. Cropper, David Katz, et al.
The ESA cornerstone mission GAIA will perform astrometric, photometric and spectroscopic measurements and is due for launch in 2010 into L2 orbit. The astrometric telescope system will catalogue the position of over 109 objects down to 20th magnitude and perform broadband photometry. The spectroscopic telescope will provide narrow-band photometry and feed a Radial Velocity Spectrometer which will accurately determine the radial velocities of objects down to 17-18 magnitude. This paper discusses the characteristics of the detectors envisaged for the focal plane of the RVS instrument.
SEDHI: a new generation of detection electronics for Pléiades
Didier G. Dantes, Jean-Marc Biffi, Claude Neveu, et al.
Future earth observation optical systems will be more and more demanding in terms of ground sampling distance, swath width, number of spectral bands, duty cycle. Existing architectures of focal planes and video processing electronics are hardly compatible with these new requirements: electronic functions are splitted in several units, and video processing is limited to frequencies around 5 MHz in order to fulfil the radiometric requirements expected for high performance image quality systems. This frequency limitation induces a high number of video chains operated in parallel to process the huge amount of pixels at focal plane output, and leads to unacceptable mass and power consumption budgets. Furthermore, splitting the detection electronics functions into several units (at least one for the focal plane and proximity electronics, and one for the video processing functions) does not optimize the production costs : specific development efforts must be performed on critical analog electronics at each equipment level and operations of assembly, integration and tests are duplicated at equipment and subsystem levels. Taking into account these constraints, Alcatel Space has developed with CNES a new concept of Highly Integrated Detection Electronic Subsystem (SEDHI). This paper presents the design of this new concept and summarizes the main performances which have been measured at component and subsystem levels. The electrical, mechanical and thermal aspects of the SEDHI concept are described, including the basic technologies : ASIC for detector clocks driving, ASIC for video processing, ASIC for phase trimming, hybrids, microchip modules... The adaptability to a large amount of missions and optical instruments is also discussed. Design, performance and budgets of the subsystem are given for the Pléiades mission (successor of SPOT) for which the SEDHI concept has been selected.
Low cost uncooled IRFPA and molded IR lenses for enhanced driver vision
Arnaud Crastes, Jean-Luc Tissot, Yann M. Guimond, et al.
Uncooled infrared focal plane arrays are being developed for a wide range of thermal imaging applications. CEA / LETI developments are focused on the improvement of their sensitivity enabling the possibility to reduce the pixel pitch in order to decrease the total system cost by using smaller optics. We present the characterization of a 160 x 120 infrared focal plane array with a pixel pitch of 35 μm. The amorphous silicon based technology is the latest one developed by CEA / LETI and transferred to ULIS. ULIS developed for this device a low cost package based on existing technologies. The readout integrated circuit structure is using an advanced skimming function to enhance the pixel signal exploitation. This device is well adapted to high volume infrared imaging applications where spatial resolution is less important than device cost. The electro-optical characterization is presented. Besides, A unique and high precision molding technology has been developed by Umicore IR Glass to produce low cost chalcogenide infrared glass lenses with a high performance level. Spherical, aspherical and asphero-diffractive lenses have been manufactured with very accurate surface precision. The performances are comparable to those of an optic made with aspherical germanium. This new glass named GASIR2 offers an alternative solution to germanium for thermal imaging, especially for medium and high volumes applications. These two key technologies are well adapted to develop infrared enhanced driver vision (EDV) system for commercial application. A European project named ICAR has been setting up to exploit these advantages. An overview of the project will be given.
Adaptive transfer function concept for uncooled FLIR cameras
The adaptive transfer function concept analyzes the various factors contributing to the uncooled microbolometer FLIR camera performances, and describes a series of solutions to control in real time its transfer function for optimal performances. The paper describes the entire camera concept, elaborating in more details the following subjects: 1. The time domain filter used to improve the SNR and its control function, 2. The two dimensional filter used to remove the DC and the low frequencies components, 3. The supplementary filter used to reduce one over f law power noise on vertical direction, 4. The dynamic range compression and its control function.
Thales Angenieux recent progress in night vision technology
Joel Rollin, Jean Louis Teszner, Jean-Luc Espie
Uncooled LWIR technology yields now an attractive alternative within the thermal sights area: TAGX launched one year ago, a new product line ELVIR, promoting cost-efficient solutions whilst meeting performances that are likely to suit most hand-held military purposes. We backed on our earnest skills on previous in-house made equipment such as light intensifier goggles, to reach the best trends, both complying with operational demands and current market prices. The very first step which is aiming at settling the main device characteristics will be emphasized thought typical requirements upon current customer’s requests: quick and flexible range computations models should answer that purpose and we will rely on operational feed back. ELVIR is built around micro- bolometer arrays that are available in France: a very best effort was done on each cost budget contributor, involving mechanics, electronics and optics. As detailed hereafter, many improvements were steered up by the latest research outcomes, partly sponsored by the French DGA, as, for instance, low cost LWIR lenses already off-the-shelves in France thanks to the UMICORE IR Glass Company. All these compromises will be displayed
Posters
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Development of laser-induced grating spectroscopy for underwater temperature measurement in shock wave focusing regions
Ardian B. Gojani, Paul M. Danehy, David W. Alderfer, et al.
In Extracorporeal Shock Wave Lithotripsy (ESWL) underwater shock wave focusing generates high pressures at very short duration of time inside human body. However, it is not yet clear how high temperatures are enhanced at the spot where a shock wave is focused. The estimation of such dynamic temperature enhancements is critical for the evaluation of tissue damages upon shock loading. For this purpose in the Interdisciplinary Shock Wave Research Center a technique is developed which employs laser induced thermal acoustics or Laser Induced Grating Spectroscopy. Unlike most of gas-dynamic methods of measuring physical quantities this provides a non-invasive one having spatial and temporal resolutions of the order of magnitude of 1.0 mm 3 and 400 ns, respectively. Preliminary experiments in still water demonstrated that this method detected sound speed and hence temperature in water ranging 283 K to 333 K with errors of 0.5%. These results are used to empirically establish the equation of states of water, gelatin or agar cell which will work as alternatives of human tissues.
Design and analysis of filter-based optical systems for spectral responsivity estimation of digital video cameras
Gao-Wei Chang, Hong-Da Jian, Zong-Mu Yeh, et al.
For estimating spectral responsivities of digital video cameras, a filter-based optical system is designed with sophisticated filter selections, in this paper. The filter consideration in the presence of noise is central to the optical systems design, since the spectral filters primarily prescribe the structure of the perturbed system. A theoretical basis is presented to confirm that sophisticated filter selections can make this system as insensitive to noise as possible. Also, we propose a filter selection method based on the orthogonal-triangular (QR) decomposition with column pivoting (QRCP). To investigate the noise effects, we assess the estimation errors between the actual and estimated spectral responsivities, with the different signal-to-noise ratio (SNR) levels of an eight-bit/channel camera. Simulation results indicate that the proposed method yields satisfactory estimation accuracy. That is, the filter-based optical system with the spectral filters selected from the QRCP-based method is much less sensitive to noise than those with other filters from different selections.
FPA Signal Processing and Applications
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Single-pixel carrier-based approach for full-field laser interferometry using a CMOS-DSP camera
This investigation describes the implementation of a Single Pixel Carrier Based Demodulation (SPCBD) approach on a digital CMOS-DSP camera for full-field heterodyne interferometry. A full-field vibration measurement system is presented as an alternative to a classical scanning Laser Doppler Vibrometer (LDV). The Heterodyne set-up, CMOS-DSP camera and the signal demodulation techniques adopted are described. Characterisation tests that describe the basic performance of the CMOS-DSP camera, in terms of acquisition rates and time response are presented. A simple experiment was performed to demonstrate the novel laser vibrometry system that consisted of determining the displacement of a point on the surface of a vibrating mirror. The measured velocity and displacement data were compared to the output from a commercial LDV. The integration of a CMOS sensor, DSP and a laser-doppler interferometer has lead to the development of a fully digital “functional” machine vision system that provides a flexible, compact and inexpensive tool for automated high-precision optical measurements.