This PDF file contains the front matter associated with SPIE Proceedings Volume 9451, including the Title Page, Copyright information, Table of Contents, Invited Panel Discussion, and Conference Committee listing.

The multispectral sensor suite consists of a HD-TV camera sensitive in the visible (VIS) spectral range and a short wave infrared ( SWIR) camera channel in combination with an integrated laser range finder all through one common entrance pupil. The sensor suite is developed for long ranging surveillance applications.

A significant reduction of the noise equivalent irradiance (NEI) of the SWIR imager in the multispectral VIS/SWIR sensor suite has been reached by a pitch reduction and corresponding optics F-number reduction of the SWIR channel. The pitch has been reduced from 20μm to 15μm and the F-number from F/7.0 to F/5.25, respectively. The visible channel has a F-number of F/2.6 with a 11- times optical zoom and provides the same field of view and focus position as the SWIR camera with the reduced pitch. The contributions from the pitch dependent dark current and read out noise levels in combination with the reduced F-number, increasing the resulting signal to noise ratio (SNR), are discussed.

The optical design of the SWIR imaging path has been significantly improved with respect to the resulting modulation transfer function (MTF) performance, resulting in an improved resolution with respect to the initial configuration [1,2]. The optical coating designs of the two multispectral beam splitters for the separation of the visual (450nm – 680nm) from the SWIR spectral wavelength range (900nm – 1700 nm) and the separation of the included laser rangefinder (LRF) receiver channel at 1.57nm center wavelength have been improved with respect to the optical imaging performance. First electro-optical results of the improved multispectral sensor suite are discussed and compared with the original design.

SWIR imaging based on InGaAs based FPAs is well suited for passive or active day and night vision applications in different weather conditions, including surveillance, defense or fire-fighting. Xenics developed the Rufus camera, based on a 640 x 512 pixel resolution FPA. In order to achieve the best performance over a large span of lighting conditions, different smart algorithms are implemented onboard.

The auto-exposure algorithm optimizes the integration time in order to position the image histogram at a given usercontrolled brightness level. Moreover the algorithm can also switch automatically between different gain and read-out modes. At the same time a TrueNUC™ algorithm is calculating the non-uniformity correction. This correction depends on the detector temperature and integration time, because of the variable dark current of the InGaAs diodes. After the image correction and auto-exposure, further image enhancement is done by additional auto-gain and histogram equalization algorithms. Depending on the application, the user can modify several parameters of the algorithms, e.g. the maximal allowed stretching, the output histogram position and equalization strength.

In the paper we will report on the performance of the algorithms at different environmental conditions. The residual Fixed Pattern Noise (FPN) of the TrueNUC™ model is analyzed. For the TrueNUC™ implementation a typical residual FPN of <1% is obtained (at 25°C) over the complete integration time range from 100us up to 40ms, both in high and low gain. Finally we will illustrate the capabilities of the algorithms in different applications.

RTI has developed a photodiode technology based on solution-processed PbS colloidal quantum dots (CQD). These devices are capable of providing low-cost, high performance detection across the Vis-SWIR spectral range. At the core of this technology is a heterojunction diode structure fabricated using techniques well suited to wafer-scale fabrication, such as spin coating and thermal evaporation. This enables RTI’s CQD diodes to be processed at room temperature directly on top of read-out integrated circuits (ROIC), without the need for the hybridization step required by traditional SWIR detectors. Additionally, the CQD diodes can be fabricated on ROICs designed for other detector material systems, effectively allowing rapid prototype demonstrations of CQD focal plane arrays at low cost and on a wide range of pixel pitches and array sizes.

SWIR spectral band is an attractive domain thanks to its intrinsic properties. Close to visible wavelengths, SWIR images interpretation is made easier for field actors. Besides complementary information can be extracted from SWIR band and bring significant added value in several fields of applications such as defense and security (night vision, active imaging), space (earth observation), transport (automotive safety) or industry (non destructive process control).

Among the various new technologies able to detect SWIR wavelengths, InGaAs appears as a key technology. Initially developed for optical telecommunications, this material guaranties performances, stability and reliability and is compatible with attractive production capacity. Thanks to high quality material, very low dark current levels can be achieved at ambient temperature. Then uncooled operation can be set up, allowing compact and low power systems.

Since the recent transfer of InGaAs imaging activities from III-Vlab, Sofradir provides a framework for the production activity with the manufacturing of high performances products: CACTUS320 SW. The developments towards VGA format with 15μm pixel pitch, lead today to the industrialization of a new product: SNAKE. On one side, the InGaAs detection array presents high performances in terms of dark current and quantum efficiency. On the other side, the low noise ROIC has different additional functionalities. Then this 640x512 @ 15μm sensor appears as well suited to answer the needs of a wide range of applications.

In this paper, we will present the Sofradir InGaAs technology, the performances of our last product SNAKE and the perspectives of InGaAs new developments.

Most SWIR sensing applications are limited to cutoff wavelength of 1.7μm at room temperature due to the energy gap of InGaAs alloy lattice matched to InP. Nevertheless, there is an increasing demand for detectors with extended cutoff wavelength of up to 2.5μm for various applications. Due to system requirements those detector should be operated at near room temperature conditions. The high temperature operation requirement limits the use of high Indium content alloys, since those alloys are strained related to the InP substrate and exhibit high dark current and poor uniformity, or even SWIR MCT – both of which need significant cooling.

In this paper we will present some comparative methods for evaluation of extended wavelength SWIR detectors with reduced dark current, working at near room temperature. Those types of detectors can be based on lattice matched alloys consist of type II superlattice, as well as other advanced structures, expected to have better uniformity and utilized for variety of SWIR based applications.

For many years image intensifier tubes were used for night vision systems. In 2014, Elbit systems developed a digital low-light level CMOS sensor, with similar sensitivity to a Gen II image-intensifiers, down to starlight conditions. In this work we describe: the basic principle behind this sensor, physical model for low-light performance estimation and results of field testing.

SiOnyx has demonstrated imaging at light levels below 1 mLux at 60 FPS with a 720P CMOS image sensor in a compact, low latency camera. The camera contains a 1 inch (16 mm) optical format sensor and streams uncompressed video over CameraLink with row wise image latency below 1 msec. Sub mLux imaging is enabled by the combination of enhanced quantum efficiency in the near infrared together with state of the art low noise image sensor design. The quantum efficiency enhancement is achieved by utilizing SiOnyx’s proprietary ultrafast laser semiconductor processing technology that enhances the absorption of light within a thin pixel layer. Our technology demonstrates a 10 fold improvement in infrared sensitivity over incumbent imaging technology while maintaining complete compatibility with standard CMOS image sensor process flows. Applications include surveillance, nightvision, and 1064nm laser see-spot.

Nowadays, maritime piracy turns out to be a severe threat for commercial ships, as illustrated by recent events that occurred in Gulfs of Aden and Guinea. Consequently, the design of a fully integrated shipborne self-protection system to counter this treat becomes a requirement. Today’s technology allows to equip commercial ships that are sailing in high-risk areas with early detection, dissuasion and protection capabilities to face coordinated attacks from pirates in various scenarios.

In this paper, a practical example of a module composed of multiple distributed COTS Infra-Red passive sensors is discussed. It is focused on a 360° close day/night surveillance system around the ship to detect and track these specific threats. The observation module presented hereafter takes advantage of Sagem experience in naval applications and infrared-based surveillance systems. The paper puts forward the detection process (image processing and 3D tracking). The module is planned to be combined with other ones (radar, AIS (Automatic Identification Systems) and electro-optics sensors suites) through a data fusion process in order to provide the ship with a continuous maritime awareness situation from long to very short ranges. The multisensor suite is part of BlueDome, a comprehensive and non-lethal anti-piracy solution developed by the Sagem-led Autoprotection consortium and recently unveiled at the Euromaritime trade show.

To conclude, results of detection scenarios are provided. Data have been registered during sea trials dedicated to very short range threats. Results highlight how the module detects and tracks the threats to be targeted. They also demonstrate how module performances are improved by implementing two specific processes: track fusion and features association in tracking process (heuristics assessment).

Electro-optical surveillance and reconnaissance systems are frequently mounted on unstable or vibrating platforms such as ships, vehicles, aircraft and masts. Mechanical coupling between the platform and the cameras leads to angular vibration of the line of sight. Image motion during detector and eye integration times leads to image smear and a resulting loss of resolution. Additional effects are wavy images for detectors based on a rolling shutter mechanism and annoying movement of the image at low frequencies. A good stabilization system should yield sub-pixel stabilization errors and meet cost and size requirements.

There are two main families of LOS stabilization methods: opto-mechanical stabilization and electronic stabilization. Each family, or a combination of both, can be implemented by a number of different techniques of varying complexity, size and cost leading to different levels of stabilization. Opto-mechanical stabilization is typically based on gyro readings, whereas electronic stabilization is typically based on gyro readings or image registration calculations. A few common stabilization techniques, as well as options for different gimbal arrangements will be described and analyzed. The relative merits and drawbacks of the different techniques and their applicability to specific systems and environments will be discussed.

Over the years Controp has developed a large number of stabilized electro-optical payloads. A few examples of payloads with unique stabilization mechanisms will be described.

US Domestic, International, allied Foreign National Warfighters and Para-Military First Responders (Police, SWAT, Special Operations, Law Enforcement, Government, Security and more) are put in harm’s way all the time. To successfully complete their missions and return home safely are the primary goals of these professionals. Tactical product improvements that affect mission effectiveness and solider survivability are pivotal to understanding the past, present and future of Clip-On in-line weapon sights.

Clip-On Weapon Sight (WS) technology was deemed an interim solution by the US Government for use until integrated and fused (day/night multi-sensor) Weapon Sights (WSs) were developed/fielded. Clip-On has now become the solution of choice by Users, Warriors, Soldiers and the US Government. SWaP-C (size, weight and power –cost) has been improved through progressive advances in Clip-On Image Intensified (I2), passive thermal, LL-CMOS and fused technology. Clip-On Weapon Sights are now no longer mounting position sensitive. Now they maintain aim point boresight, so they can be used for longer ranges with increased capabilities while utilizing the existing zeroed weapon and daysight optic.

Active illuminated low-light level (both analog I2 and digital LL-CMOS) imaging is rightfully a real-world technology, proven to deliver daytime and low-light level identification confidence. Passive thermal imaging is also a real-world technology, proven to deliver daytime, nighttime and all-weather (including dirty battlefield) target detection confidence. Image processing detection algorithms with intelligent analytics provide documented promise to improve confidence by reducing Users, Warriors and Soldiers’ work-loads and improving overall system engagement solution outcomes. In order to understand the future of Clip-On in-line weapon sights, addressing pros and cons, this paper starts with an overview of historical weapon sight applications, technologies and stakeholder decisions driving milestone events that helped shape the Clip-On weapon sight industry. Then, this paper systematically reviews current attributes of integrated multispectral wavelength electro-optical imaging systems that successfully (and sometimes unsuccessfully) shape today’s Warrior, Soldier and User’s net-capabilities. Finally, this paper explores the evolution, pros and cons, of future Clip-On weapon sights, from a manufacturing and real world applications perspective for tomorrow’s military soldier and paramilitary first responder.

We present a prototype of an infrared cryogenic camera directly integrated inside an off-the-shelf SOFRADIR's Detector Dewar Cooler Assembly (DDCA) and whose field of view is equal to 120°. Based on the co-design principle between optical design and image processing, we have designed a multichannel camera which produces four non-redundant images on a single SCORPIO detector, with 640 × 512 pixels and a pixel pitch of 15 μm. This leads to an ultra-miniaturized optical system with a very low additional optical and mechanical mass to be cooled. By this way, the cool-down time of the camera is comparable to the one of an equivalent DDCA without an imagery function. Indeed, we obtain a cool-down time of 6 minutes with a THALES Cryogenics RM3. With a superresolution algorithm, the four images produced by the camera are combined to process a single full-resolution image with an equivalent sampling pitch equal to 7.5μm. The performances of this camera, assessed by experimental characterizations, are presented.

A novel imaging device based on tomographic reconstruction is presented. The imager is based on rotating an image of the scene onto a linear detector array, and then reconstructing a 2-dimensional image from the detector array signal using tomographic reconstruction techniques. Similar in many ways to the conical scan tomographic scanning (TOSCA) imager, the spin scan TOSCA imager features several improvements compared to its predecessors, mainly because the linear array covers the whole scene and hence in principle can collect 100% of the incoming photons. In addition to presenting the theory behind the device and its sensitivity to noise, non-uniformity and errors, an experimental uncooled mid-wave infrared imager demonstrator is also presented, together with images of test targets, both the final result as well as the incremental steps in the imaging reconstruction process.

New development of imaging systems implies the use of multi band wavelength, VIS and IR, for imaging enhancement and more data presenting. As lasers as countermeasures against optics are widely spread in the recent years, these systems need to be protected from damage caused by intense radiation yet the optical system has to be transparent at these wavelengths for low light power.

This paper presents a non-linear, solid-state passive wideband optical protection filters (WPF). These filters have advantages over fixed spectral filters, which permanently block only specific wavelengths, the wideband filter is transparent at all wavelengths until it is hit by damaging light. We present work in continuation of our special design WPF suitable for dual- and multi- band wavelength range, including transmission and functionality performances. We demonstrate a new design transferring our WPF filter from VIS/NIR into the MW/LWIR.

The effectiveness of infrared imagery in poor visibility situations is well established and the range of applications is expanding as we enter a new era of inexpensive thermal imagers for mobile phones. However there is a problem in that the counterintuitive reflectance characteristics of various common scene elements can cause slowed reaction times and impaired situational awareness−consequences that can be especially detrimental in emergency situations. While multiband infrared sensors can be used, they are inherently more costly. Here we propose a technique for adding a daylight color appearance to single band infrared images, using the normally overlooked property of local image texture. The simple method described here is illustrated with colorized images from the visible red and long wave infrared bands. Our colorizing process not only imparts a natural daylight appearance to infrared images but also enhances the contrast and visibility of otherwise obscure detail. We anticipate that this colorizing method will lead to a better user experience, faster reaction times and improved situational awareness for a growing community of infrared camera users. A natural extension of our process could expand upon its texture discerning feature by adding specialized filters for discriminating specific targets.

When incorporated into the active layer of a "XBp" detector structure, Type II InAs/GaSb superlattices (T2SLs) offer a high quantum efficiency (QE) and a low diffusion limited dark current, close to MCT Rule 07. Using a simulation tool that was developed to predict the QE as a function of the T2SL period dimensions and active layer stack thickness, we have designed and fabricated a new focal plane array (FPA) T2SL XBp detector. The detector goes by the name of "Pelican-D LW", and has a format of 640 ×512 pixels with a pitch of 15 μm. The FPA has a QE of 50% (one pass), a cut-off of ~9.5 μm, and operates at 77K with a high operability, background limited performance and good stability. It uses a new digital read-out integrated circuit, and the integrated detector cooler assembly (IDCA) closely follows the configuration of SCD’s Pelican-D MWIR detector.

Short wavelength and middle wavelength dual color infrared detector were designed and prepared with InAs/Ga(In)Sb type-II superlattices materials. The Crosslight software was used to calculate the relation between wavelength and material parameter such as thickness of InAs, GaSb, then energy strucutre of 100 periods 8ML/8ML InAs/GaSb and the absorption wavelength was calculated. After fixing InAs/GaSb thickness parameter, devices with nBn and pin structure were designed and prepared to compare performance of these two structures. Comparison results showed both structure devices were available for high temperature operation which black detectivity under 200K were 7.9×10⁸cmHz^1/2/W for nBn and 1.9×10⁹cmHz^1/2/W for pin respectively. Considering the simultaneous readout requirement for further FPAs application the NIP/PIN InAs/GaSb dual-color structure was grown by MBE method. Both two mesas and one mesa devices structure were designed and prepared to appreciate the short/middle dual color devices. Cl₂-based ICP etching combined with phosphoric acid based chemicals were utilized to form mesas, silicon dioxide was deposited via PECVD as passivation layer. Ti/Au was used as metallization. Once the devices were finished, the electro-optical performance was measured. Measurement results showed that optical spectrum response with peak wavelength of 2.7μm and 4.3μm under 77K temperature was gained, the test results agree well with calculated results. Peak detectivity was measured as 2.08×10¹¹cmHz^1/2/W and 6.2×10¹⁰cmHz^1/2/W for short and middle wavelength infrared detector respectively. Study results disclosed that InAs/Ga(In)Sb type-II SLs is available for both short and middle wavelength infrared detecting with good performance by simply altering the thickness of InAs layer and GaSb layer.

A detailed understanding of limiting dark current mechanisms in InAs/GaSb type-II superlattice (T2SL) infrared detectors is key to improve the electrooptical performance of these devices. We present a six-component dark current analysis which, for the first time, takes account of sidewall-related dark current contributions in mesa-etched T2SL photodiodes. In a wide temperature range from 30K to 130K, the paper compares limiting mechanisms in two homojunction T2SL photodiode wafers for the long-wavelength infrared regime. While the two epi wafers were fabricated with nominally the same frontside process they were grown on different molecular beam epitaxy systems. In the available literature a limitation by Shockley-Read-Hall processes in the space charge region giving rise to generation-recombination (GR) dark current is the prevailing verdict on the bulk dark current mechanism in T2SL homojunction photodiodes around 77K. In contrast, we find that investigated photodiode wafers are instead limited by the diffusion mechanism and the ohmic shunt component, respectively. Furthermore, our in-depth analysis of the various dark current components has led to an interesting observation on the temperature dependence of the shunt resistance in T2SL homojunction photodiodes. Our results indicate that the GR and the shunt mechanism share the same dependence on bandgap and temperature, i.e., a proportionality to exp(-E_g/2kT).

We examine carrier transport in unipolar barrier infrared photodetectors and discuss aspects of barrier, contact, and absorber properties that can affect minority carrier collection. In a barrier infrared detector the unipolar barrier should block only the majority carriers while allowing the un-impeded flow of the minority carriers. Under the right conditions, unipolar barrier doping can reduce generation-recombination dark current without affecting minority carrier extraction. In an nBn structure, ideally with an electron unipolar barrier, improper barrier doping or barrier-absorber valence band offset could also block minority carriers and result in higher turn-on bias. We also examined the temperature-dependent turn-on bias in an n⁺Bn device and showed that observed behavior may be attributed to contact doping. Hole mobility in n-doped type-II superlattice (T2SL) is believed to be very low because of the extremely large effective mass along the growth direction. In practice MWIR and LWIR barrier infrared detectors with n-type T2SL absorbers have demonstrated good optical response. A closer inspection of the T2SL band structure offers a possible explanation as to why the hole mobility may not be as poor as suggested by the simple effective mass picture.

This paper reports a study of Shockley-Read-Hall, radiative, and Auger recombination processes in a series of molecular beam epitaxy grown InAs/InAsSb mid-wavelength infrared and long-wavelength infrared type-II superlattice samples using temperature- and excitation -density-dependent photoluminescence measurements, which are carried out from 12 to 77 K with excitation densities from 5 mW/cm² to 20 W/cm². A theoretical model is applied to describe the relation between integrated photoluminescence intensity and excitation density. Shockley-Read-Hall, radiative, and Auger recombination coefficients are extracted by fitting this relation. The results show that the Shockley-Read-Hall recombination lifetimes in all InAs/InAsSb type-II superlattice samples are longer than 100 ns, specifically the lifetime in a long-wavelength infrared sample reaches 358 ns at 77 K, in good agreement with the previously reported result of 412 ns measured using time-resolved photoluminescence on a similar sample.

We propose to utilize confocal Raman spectroscopy combined with high resolution atomic force microscopy (AFM) for nondestructive characterisation of the sidewalls of etched and passivated small pixel (24 μm×24 μm) focal plane arrays (FPA) fabricated using LW/LWIR InAs/GaSb type-II strained layer superlattice (T2SL) detector material. Special high aspect ratio Si and GaAs AFM probes, with tip length of 13 μm and tip aperture less than 7°, allow characterisation of the sidewall morphology. Confocal microscopy enables imaging of the sidewall profile through optical sectioning. Raman spectra measured on etched T2SL FPA single pixels enable us to quantify the non-uniformity of the mesa delineation process.

In this paper we report on an industry first; the commercial growth and characterization of >/=6" diameter GaSb substrates that are suitable for use in the fabrication of epitaxially grown, large area MWIR-VLWIR detectors. Results will be presented on the production of single crystal >/=6" GaSb ingots grown by a modified version of the Czochralski (LEC) technique, supported by the analysis of bulk material quality by spatial etch pit density assessments with mm resolution. The electrical quality of 6" GaSb crystals will be assessed. Hall mobility, resistivity and carrier level measurements will be made spatially. High quality, epitaxy-ready type surfaces have been prepared and we will demonstrate how the key surface quality characteristics of roughness, oxide thickness and flatness have been maintained across production processes that scale from 4" to ≥6" wafer formats. Comparisons will be made between ≥6" GaSb and other large diameter compound semiconductor materials produced in volume such as GaAs and InP. We conclude by demonstrating that the commercial production of large diameter GaSb substrates has matured and is thus ready to support the full commercialization of GaSb based detector technologies.

The GaSb-based 6.1 Å lattice constant family of materials and heterostructures provides rich bandgap engineering possibilities and have received considerable attention for their potential and demonstrated performance in infrared (IR) detection and imaging applications. Mid-wave and long-wave IR photodetectors are progressing toward commercial manufacturing applications. To succeed, they must move from research laboratory settings to general semiconductor production, and high-quality GaSb-based epitaxial wafers with diameter larger than the current standard 3-inch are highly desirable. 4-inch GaSb substrates have been in production for a couple of years and are now commercially available. Recently, epi-ready GaSb substrates with diameter in excess of 6-inch were successfully produced. In this work, we report on the MBE (Molecular Beam Epitaxy) growth of generic MWIR bulk nBn photodetectors on 6-inch diameter GaSb substrates. The surface morphology, optical and structural quality of the epiwafers as evaluated by atomic force microscopy (AFM), Nomarski microscopy, low temperature photoluminescence (PL) spectroscopy, and high-resolution x-ray diffraction (XRD) will be discussed. Current density versus voltage (J-V) and photoresponsivity measurements from large-area mesa diode fabricated will also be reported. Material and device properties of these 6-inch epiwafers will be compared to similar structures grown on commercially available 4-inch diameter GaSb substrates.

Gallium antimonide (GaSb) is an important Group III-V compound semiconductor for infra-red (IR) photodetectors used in sensing and imaging applications. Operating in the mid (3-5 μm) to long wavelength region (8-12 μm) of the IR spectrum, the application of GaSb detectors is extensive, encompassing military, industrial, medical and environmental uses. A significant developing technology for GaSb based detectors are those effective in the very long wavelength (VLWIR) infra-red region (13 μm and beyond) which are advantageous in space and stealth based applications which necessitate high operating temperatures. In this study different doping levels of GaSb are considered and the IR transmission spectra examined by Fourier Transform IR analysis. GaSb n-type doped material consistent in delivering long to very long wavelength transmission is demonstrated which is preferable to p-type material which requires backside thinning for IR transmission. Czochralski (Cz) grown GaSb wafers are assessed for electrical quality and uniformity results, on Hall mobility, resistivity and carrier level reported. Results of this work will establish the carrier concentration that ultimately results in high transparency substrates. In summary enhancements in IR transmission will be shown to be achieved in GaSb bulk crystals by tellurium (Te) compensation.

This paper presents and discusses digital pixel readout integrated circuit architectures for long wavelength infrared (LWIR) in CMOS technology. Presented architectures are designed for scanning and staring arrays type detectors respectively. For scanning arrays, digital time delay integration (TDI) is implemented on 8 pixels with sampling rate up to 3 using CMOS 180nm technology. Input referred noise of ROIC is below 750 rms electron meanwhile power dissipation is appreciably under 30mW. ROIC design is optimized to perform at room as well as cryogenic temperatures. For staring type arrays, a digital pixel architecture relying on coarse quantization with pulse frequency modulation (PFM) and novel approach of extended integration is presented. It can achieve extreme charge handling capacity of 2.04Ge^- with 20 bit output resolution and power dissipation below 350 nW in CMOS 90nm technology. Efficient mechanism of measuring the time to estimate the remaining charge on integration capacitor in order to achieve low SNR has employed.

This paper reports the development of a new SXGA format low-noise CTIA ROIC (MT12815CA-3G) suitable for mega-pixel SWIR InGaAs detector arrays for low-light imaging applications. MT12815CA-3G is the first mega-pixel standard ROIC product from Mikro-Tasarim, which is a fabless semiconductor company specialized in the development of ROICs and ASICs for visible and infrared hybrid imaging sensors. MT12815CA-3G is a low-noise snapshot mega-pixel CTIA ROIC, has a format of 1280 × 1024 (SXGA) and pixel pitch of 15 μm. MT12815CA-3G has been developed with the system-on-chip architecture in mind, where all the timing and biasing for this ROIC are generated on-chip without requiring any special external inputs. MT12815CA-3G is a highly configurable ROIC, where many of its features can be programmed through a 3-wire serial interface allowing on-the-fly configuration of many ROIC features. It performs snapshot operation both using Integrate-Then-Read (ITR) and Integrate-While-Read (IWR) modes. The CTIA type pixel input circuitry has 3 gain modes with programmable full-well-capacity (FWC) values of 10K e-, 20K e-, and 350K e- in the very high gain (VHG), high-gain (HG), and low-gain (LG) modes, respectively. MT12815CA-3G has an input referred noise level of less than 5 e- in the very high gain (VHG) mode, suitable for very low-noise SWIR imaging applications. MT12815CA-3G has 8 analog video outputs that can be programmed in 8, 4, or 2-output modes with a selectable analog reference for pseudo-differential operation. The ROIC runs at 10 MHz and supports frame rate values up to 55 fps in the 8-output mode. The integration time of the ROIC can be programmed up to 1s in steps of 0.1 μs. The ROIC uses 3.3 V and 1.8V supply voltages and dissipates less than 350 mW in the 4-output mode. MT12815CA-3G is fabricated using a modern mixed-signal CMOS process on 200 mm CMOS wafers, and there are 44 ROIC parts per wafer. The probe tests show that the die yield is higher than 70%, which corresponds to more than 30 working ROIC parts per wafer typically. MT12815CA-3G ROIC is available as tested wafers or dies, where a detailed test report and wafer map are provided for each wafer. A compact USB 3.0 based test camera and imaging software are also available for the customers to test and evaluate the imaging performance of SWIR sensors built using MT12815CA-3G ROICs. Mikro-Tasarim has also recently developed a programmable mixed-signal application specific integrated circuit (ASIC), called MTAS1410X8, which is designed to perform ROIC driving and digitization functions for ROICs with analog outputs, such as MT12815CA-3G and MT6415CA ROIC products of Mikro-Tasarim. MTAS1410X8 has 8 simultaneously working 14-bit analog-to-digital converters (ADCs) with integrated programmable gain amplifiers (PGAs), video input buffers, programmable controller, and high-speed digital video interface supporting various formats including Camera-Link. MT12815CA-3G ROIC together with MTAS1410X8 ASIC can be used to develop low-noise high-resolution SWIR imaging sensors with low power dissipation and reduced board area for the camera electronics.

This paper presents and discusses the cryogenic temperature (77K) measurement results of a digital readout integrated circuit (DROIC) for a 32x32 long wavelength infrared pixel sensor array designed in 90nm CMOS process. The chip achieves a signal-to-noise ratio (SNR) of 58dB with a charge handling capacity of 2.03Ge- at cryogenic temperature with 1.3mW of power dissipation. The performance of the readout is discussed in terms of power dissipation, charge handling capacity and SNR considering the fact that the process library models are not optimized for cryogenic temperature operation of the Metal-Oxide-Semiconductor (MOS) devices. These results provide an insight to foresee the design confrontations due to non-optimized device models for cryogenic temperatures particularly for short channel devices

This paper presents a mixed-signal LVDS driver in 90 nm CMOS technology. The designed LVDS core is to be used as a data link between Infrared Focal Plane Array (IRFPA) detector end and microprocessor input. Parallel data from 220 pixels of IRFPA is serialized by LVDS driver and read out to microprocessor. It also offers a reduced power consumption rate, high data transmission speed and utilizes dense placement of devices for area efficiency. The entire output driver circuit including input buffer draws 5mA while the output swing is 500mV at power supply of 1.2V for data rate of 6.4Gbps.Total LVDS chip area is 0.79 mm². Due to these features, the designed LVDS driver is suitable for purposes such as portable, high-speed imaging.

This paper reports the development of a new microbolometer Readout Integrated Circuit (ROIC), called MT6417BA. It has a format of 640 × 480 (VGA) and a pixel pitch of 17μm. MT6417BA is Mikro-Tasarim’s third microbolometer ROIC, which is developed specifically for surface micro-machined microbolometer detector arrays using high-TCR pixel materials, such as VO_x and a-Si. MT6417BA has a system-on-chip architecture, where all the timing, biasing, and pixel non-uniformity-correction (NUC) operations in the ROIC are applied using on-chip circuitry simplifying the use and system integration of this ROIC. MT6417BA has a serial programming interface that can be used to configure the programmable ROIC features and to load the NUC date to the ROIC. MT6417BA has a total of 4 analog video outputs and 2 analog reference outputs, placed at the top and bottom of the ROIC, which can be programmed to operate in the 1, 2, and 4-output modes and can support frames rates above 60 fps at 10 MHz pixel output rate. The ROIC is designed to support pixel resistance values ranging up to 100kΩ. MT6417BA is operated using conventional row based readout method, where pixels in the array are readout in a row-by-row basis, where they are biased and integrated using synchronously applied NUC data.

The NUC data is applied continuously in a row-by-row basis using the serial programming interface operated at 20 MHz supporting frame rates as high as 60 fps. The bias voltage of the pixels can be programmed over a 1.0 V range to compensate for the changes in the detector resistance values due to the variations coming from the manufacturing process. The ROIC has an on-chip integrated temperature sensor with a sensitivity of better than 5 mV / K, and the output of the temperature sensor is embedded in the analog video stream. MT6417BA can be used to build a microbolometer FPAs with an NETD value below 50 mK using a microbolometer detector array fabrication technology with a nominal detector resistance of 60 KΩ, a high TCR value (> 3 % / K), and a sufficiently low pixel thermal conductance (G_th ≤ 10 nW / K). MT6417BA ROIC die measures 14.1 mm × 15.4 mm in a 180 nm CMOS. MT6417BA is fabricated on 200 mm diameter CMOS wafers with 100 parts per wafer. The microbolometer ROIC wafers are engineered to have flat surface finish to simplify the wafer level detector fabrication and wafer-level vacuum packaging (WLVP). The ROIC runs on 3.3 V analog and 1.8 V digital supplies, and dissipates less than 150 mW in the 2-output mode at 60 fps. Mikro-Tasarim provides tested ROIC wafers and offers compact test electronics and software for its ROIC customers to shorten their uncooled FPA and camera development cycles. Mikro-Tasarim has also recently developed a new programmable mixed-signal application specific integrated circuit (ASIC), called MTAS1410X4, which is designed to perform ROIC driving and digitization functions for microbolometer ROICs with analog outputs, such as MT6417BA and MT3825BA ROIC products of Mikro-Tasarim. MTAS1410X4 has 4 simultaneously working 14-bit analog-to-digital converters (ADCs) with integrated programmable gain amplifiers (PGAs), video input buffers, a programmable controller, and a flash memory interface for NUC operations. MT6417BA ROIC together with MTAS1410X4 ASIC can be used to develop low-noise and low-power uncooled microbolometer imaging sensors with compact camera electronics.

The growing demand for compact and low consumption infrared cooled detectors is driven by different products segments. Hand Held Thermal Imagers, UAV, small gimbals are some of them. End users are requiring devices easy to use with fast cool down time, excellent portability, low acoustic noise with no trade-offs in reliability and performance. These requirements are pushing the technology developments toward constant innovations on detectors, coolers, read out circuits and proximity electronic boards. In this paper we are discussing the different figures of merit and highlighting the challenges for the different components. An update on the developments of HOT technology for most advanced pixel pitch will be presented. Very compact products are driving the developments for innovative coolers and cryogenic solutions. A low power compact architecture is a must for electronic boards to optimize the overall system power consumption. Finally a look to the future requirements for further shrink will be addressed.

Raising the operating temperature of mercury cadmium telluride infrared detectors from 80K to above 160K creates new applications for high performance infrared imagers by vastly reducing the size, weight and power consumption of the integrated cryogenic cooler. Realizing the benefits of Higher Operating Temperature (HOT) requires a new kind of infrared camera core with the flexibility to address emerging applications in handheld, weapon mounted and UAV markets. This paper discusses the Firefly core developed to address these needs by Selex ES in Southampton UK. Firefly represents a fundamental redesign of the infrared signal chain reducing power consumption and providing compatibility with low cost, low power Commercial Off-The-Shelf (COTS) computing technology. This paper describes key innovations in this signal chain: a ROIC purpose built to minimize power consumption in the proximity electronics, GPU based image processing of infrared video, and a software customisable infrared core which can communicate wirelessly with other Battlespace systems.

The realization of high operating temperature (HOT) midwave infrared (MWIR) photodetectors would significantly relax the requirements imposed on the cooling system, which would lead to a reduction in the size, weight, and cost of the detection system. One of the most attractive material systems to develop HOT photodetectors is InAs/GaSb Type II Superlattice (T2SL). This is due the ability of T2SL materials to engineer the band structure of the device, which can be exploited to make devices with unipolar barriers. It has been shown that the use of unipolar barriers can dramatically reduce the dark current levels of the device, which is essential to realize HOT photodetectors. In this work, we report on the performance of a unipolar barrier mid wave infrared detector based on type-II InAs/GaSb strained layer superlattice for high operating temperatures. The device architecture is the double-barrier heterostructure, pBiBn design. Under an applied bias of -10 mV and an operating temperature of 200 K, the best performing devices show a dark current density of 4.9×10^-4 A/cm². At 200 K, the measured zero-bias specific detectivity was 4.4×10¹⁰ Jones.

Significant attention has recently been given to photoluminescence (PL) spectra and lifetime measurements on InAs/InAsSb superlattices, as high quality optical material with long carrier lifetimes are required for infrared detectors. The standard sample structure for PL measurements includes energy barriers to block photo-generated carriers from being lost through non-radiative recombination at interfaces between the superlattice and the surface or between the superlattice and the buffer/substrate. However, defect, surface, and/or interface states in AlSb, a commonly used barrier material, are known to contribute carriers to InAs quantum wells. Due to the similarity of the AlSb interface with the InAs/InAsSb superlattice, the effects of the barriers on the electrical and optical properties of the superlattice were investigated. Structures with AlSb barriers at the top and bottom of the superlattice, with no AlSb barriers, and with an AlSb barrier only at the top of the superlattice structure were studied. Hall Effect measurements revealed little change in the sheet carrier concentration at 10 K due to the barriers, but significant increases in low temperature mobility and a two-dimensional-like mobility temperature dependence were observed when barriers were present. Further high magnetic field measurements are necessary, however, to understand the transport properties of these samples due to the likelihood that multiple carriers are present. The photoluminescence (PL) spectra were almost identical regardless of the barriers, except for a 15% increase in intensity with the AlSb barrier between the buffer layer and the superlattice. The surface AlSb barrier had little effect on the intensity. The barriers are therefore recommended for PL measurements to increase the signal intensity; however, they complicate the analysis of single-field Hall Effect measurements.

The InAs/GaSb type-II superlattice (T2-SL) based interband cascade (IC) photodetectors are emerging as a promising candidate for high performance infrared (IR) detectors, particularly for high operating temperature applications. In this paper, we present our latest progress on the development of high performance IC photodetectors in both mid- and longwave-IR. Our results show significant improvement in both the electrical and optical performance for the IC detectors. The mid-IR detectors show zero-bias operation, with external quantum efficiency as high as 11%. The dark current is 1.75 nA/cm² at 120 K and -10mV, which shows over 5 times improvement over our previous best results. The Johnson-limited D* of the mid-IR detector is around 1.20×10¹¹ Jones at 200 K, showing more than 10 times improvement over a wide temperature range. These mid-IR IC detectors have obtained background limited operation up to 210 K. Progress in longwave-IR IC detectors is also presented, which also demonstrates excellent electrical performance.

Numerical analysis of a CdS/PbSe room-temperature heterojunction photovoltaic detector is discussed as to provide guidelines for practical improvement, based on the previous experimental exploration [1]. In our experiment work, the polycrystalline CdS film was prepared in hydro-chemical method on top of the single crystalline PbSe grown by molecular beam epitaxy method. The preliminary results demonstrated a 5.48×10⁸ Jones peak detectivity at λ=4.7μm under zero-bias. However, the influence of some material and device parameters such as carrier concentration, interface recombination velocity remains uncertain. These parameters affect the built-in electric field and the carriers’ transportation properties, and consequently could have detrimental effect on the device performance of the CdS/PbSe detector. In this work, therefore, the numerical analysis is performed based on these parameters. The simulation results suggest that the device performance can be improved at least 4 times by increasing CdS concentration for two orders of magnitudes, and the device performance will degrade severely if the interface recombination speed is over 10⁴ cm/s.

The work reports on mid-wavelength infrared HgCdTe barrier detectors with a zero valence band offset, grown by metal organic chemical vapour deposition on GaAs substrates. The experiments indicate the influence of the barrier on electrical and optical performances of the p⁺BnN⁺ device. The devices exhibit very low dark current densities in the range of (2÷3)×10^–3 A/cm² at 300 K and a high current responsivity of about 2A/W in the wide range of reverse bias voltage. The estimated thermal activation energy of about 0.33 eV is close to the full Hg_0.64Cd_0.36Te bandgap, what indicates diffusion limited dark currents.

This article reviews the development of uncooled infrared focal plane array (UIFPA) imaging in China in the past decade. Sensors based on optical or electrical read-out mechanism were developed but the latter dominates the market. In resistive bolometers, VOx and amorphous silicon are still the two major thermal-sensing materials. The specifications of the IRFPA made by different manufactures were collected and compared. Currently more than five Chinese companies and institutions design and fabricate uncooled infrared focal plane array. Some devices have sensitivity as high as 30 mK; the largest array for commercial products is 640×512 and the smallest pixel size is 17 μm. Emphasis is given on the pixel MEMS design, ROIC design, fabrication, and packaging of the IRFPA manufactured by GWIC, especially on design for high sensitivities, low noise, better uniformity and linearity, better stabilization for whole working temperature range, full-digital design, etc.

Zhejiang Dali Technology Co. Ltd. is one of the major players in the China Infrared industry. The company has been working on infrared imagers using uncooled FPAs for about 15 years. It started the research and development of uncooled microbolometer detectors since 2006, and has brought several uncooled detectors into mass production, including 35um 384x288, 25um 160x120, 384x288, 640x480, and 17um 384x288, 640x480. In this presentation, we will describe the uncooled infrared detector and imager development at DALI Technology.

BAE Systems' SMART (Stacked Modular Architecture High-Resolution Thermal) Chip Camera provides very compact long-wave infrared (LWIR) solutions by combining a 12 μm wafer-level packaged focal plane array (FPA) with multichip-stack, application-specific integrated circuit (ASIC) and wafer-level optics. The key innovations that enabled this include a single-layer 12 μm pixel bolometer design and robust fabrication process, as well as wafer-level lid packaging. We used advanced packaging techniques to achieve an extremely small-form-factor camera, with a complete volume of 2.9 cm³ and a thermal core weight of 5.1g. The SMART Chip Camera supports up to 60 Hz frame rates, and requires less than 500 mW of power. This work has been supported by the Defense Advanced Research Projects Agency’s (DARPA) Low Cost Thermal Imager − Manufacturing (LCTI-M) program, and BAE Systems’ internal research and development investment.

The partnership between RVS, Seek Thermal and Freescale Semiconductor continues on the path to bring the latest technology and innovation to both military and commercial customers. The partnership has matured the 17μm pixel for volume production on the Thermal Weapon Sight (TWS) program in efforts to bring advanced production capability to produce a low cost, high performance product. The partnership has developed the 12μm pixel and has demonstrated performance across a family of detector sizes ranging from formats as small as 206 x 156 to full high definition formats. Detector pixel sensitivities have been achieved using the RVS double level advanced pixel structure. Transition of the packaging of microbolometers from a traditional die level package to a wafer level package (WLP) in a high volume commercial environment is complete. Innovations in wafer fabrication techniques have been incorporated into this product line to assist in the high yield required for volume production. The WLP seal yield is currently > 95%. Simulated package vacuum lives >> 20 years have been demonstrated through accelerated life testing where the package has been shown to have no degradation after 2,500 hours at 150°C. Additionally the rugged assembly has shown no degradation after mechanical shock and vibration and thermal shock testing. The transition to production effort was successfully completed in 2014 and the WLP design has been integrated into multiple new production products including the TWS and the innovative Seek Thermal commercial product that interfaces directly to an iPhone or android device.

We have developed the Compact Infrared Camera (CIRC) with an uncooled infrared array detector (microbolometer) for space application. Microbolometers have an advantage of not requiring cooling system such as a mechanical cooler, and is suitable for resource-limited sensor system. Another characteristic of the CIRC is its use of athermal optics. The athermal optics system compensates for defocus owing to temperature changes. We also employ a shutter-less system which is a method to correct non-uniformity of the detector without a mechanical shutter.

The CIRC achieves a small size (approximately 200 mm), light mass (approximately 3 kg), and low electrical power consumption (<20 W) by employing athermal optics and a shutterless system.

The CIRC is launched in May 2014 as a technology-demonstration payload of Advanced Land Observation Satellite-2 (ALOS-2). Since the initial functional verification phase (July 4-14, 2014), the CIRC was demonstrated a function according to its intended design. We also confirmed the temperature accuracy of the CIRC observation data is within ±4K in the calibration validation phase after the initial functional verification phase. The CIRC also detected wildfires in various areas and observed the volcano activities in the operational phase.

In this paper, we present the on-orbit performance of the CIRC onboard ALOS-2.

Over the last decade SCD has established a "state of the art" VOx μ-Bolometer product line. The market demands for low SWaP (Size, Weight and Power) uncooled engines is steadily growing, where low SWaP is especially critical in battery-operated applications such as goggles and Thermal Weapon Sights (TWS). In this approach, SCD has developed a low-SWaP, shutter-less uncooled video core, with a foot-print of 31x31mm and sub Watt power consumption. The video core contains a temperature calibrated, High Sensitivity (HS) 640x480 17μm pitch detector (NETD ≤ 32mK @ 30Hz, F/1), packaged in a new TEC-less ceramic package (26x23mm). The video core contains superior image processing algorithms including: local and global Dynamic Range Compression (DRC), and spatial and temporal de-noising algorithms providing low NETD and stable and low Residual Non Uniformity (RNU) video image.

Shutter-less infrared cameras based on microbolometer focal plane arrays (FPAs) are the most widely used cameras in thermography, in particular in the fields of handheld devices and small distributed sensors. For acceptable measurement uncertainty values the disturbing influences of changing thermal ambient conditions have to be treated corresponding to temperature measurements of the thermal conditions inside the camera. We propose a compensation approach based on calibration measurements where changing external conditions are simulated and all correction parameters are determined. This allows to process the raw infrared data and to consider all disturbing influences. The effects on the pixel responsivity and offset voltage are considered separately. The responsivity correction requires two different, alternating radiation sources. This paper presents the details of the compensation procedure and discusses relevant aspects to gain low temperature measurement uncertainty.

A shutterless algorithm is implemented into the Xenics LWIR thermal cameras and modules. Based on a calibration set and a global temperature coefficient the optimal non-uniformity correction is calculated onboard of the camera. The limited resources in the camera require a compact algorithm, hence the efficiency of the coding is important. The performance of the shutterless algorithm is studied by a comparison of the residual non-uniformity (RNU) and signal-to-noise ratio (SNR) between the shutterless and shuttered correction algorithm. From this comparison we conclude that the shutterless correction is only slightly less performant compared to the standard shuttered algorithm, making this algorithm very interesting for thermal infrared applications where small weight and size, and continuous operation are important.

Shutters are used to periodically provide a non-uniformity correction (NUC) calibration surface to micro bolometers. Many bolometer applications, such as TWS and DVE, require compact, power efficient actuators. Actuators in these applications, such as bistable solenoids and stepper motors, benefit from complex drive schemes. Consumer electronics products have generated compact, low-cost drive components that can be used to embed complex drives into these shutters. Shutter drives using these components maintain compactness and power efficiency while simplifying interfaces at minimal cost. Recently, several commercially available shutter systems have been created that incorporate embedded microprocessors into shutters usable for NUC correction of micro bolometers.

Patterned highly absorbing gold black film has been selectively deposited on the active surfaces of a vanadium-oxide-based infrared bolometer array. Patterning by metal lift-off relies on protection of the fragile gold black with an evaporated oxide, which preserves gold black’s near unity absorption. This patterned gold black also survives the dry-etch removal of the sacrificial polyimide used to fabricate the air-bridge bolometers. Infrared responsivity is substantially improved by the gold black coating without significantly increasing noise. The increase in the time constant caused by the additional mass of gold black is a modest 14%.

Three-dimensional plasmonic metamaterial absorbers (3-D PMAs) based on all-metal structures were developed. 3-D PMAs consist of a periodic array of thin metal micropatches connected to a thin metal plate with narrow metal posts. The 3-D PMA consists of plasmonic metal (Au) based components. 3-D PMAs were fabricated by a two-step lift-off procedure with a carbon sacrifice layer and a narrow metal post with a height of 200 nm was achieved. Reflection spectroscopy measurements demonstrate that the wavelength-selective absorption was realized, and the absorption wavelength can be controlled by the micropatch size, regardless of the micropatch-array period, and can be longer than the micropatch array period. Wavelength selective absorption is possible due to the surface plasmonic resonant mode localized at the micropatches. The metal posts have negligible impact on the plasmonic resonance. 3-D PMAs based on all-metal structures can be applicable for a wide range of the middle- and long-wavelength IR region due to the lack of additional absorption by an insulator layer based on SiO₂, SiN, or Al₂O₃, which are typically used in metal-insulatormetal absorbers. 3-D PMAs have a small thermal mass and an absorption wavelength beyond the period, which result in a fast response and small pixel size. The results obtained here should contribute to the high-performance wavelengthselective uncooled IR sensors and IR emitters.

A polarization-selective uncooled infrared (IR) sensor has been developed based on a one-dimensional plasmonic grating absorber (1-D PGA). The 1-D PGA has an Au-based one-dimensional periodic grating structure, where photons can be manipulated by surface plasmon resonance. A microelectromechanical systems-based uncooled IR sensor was fabricated using the 1-D PGA with complementary metal oxide semiconductor (CMOS) and micromachining techniques. The 1-D PGA was formed with an Au layer sputtered on a grating pattered SiO₂ layer. An Al layer was then introduced onto the backside of the 1-D PGA to reflect scattered light and prevent absorption at the SiO₂ backside of the absorber. The responsivity could be selectively enhanced depending on the polarization and the grating direction, and an absorption wavelength longer than the surface period and broadband absorption were realized due to the effect of the resonance in the grating depth direction. The 1-D PGAs enable a detection wavelength longer than the period and broadbandpolarization- selectivity by control of the grating depth in addition to the period. The results obtained in this study will contribute to the advancement of polarimetric IR imaging.

There is increasing demand for devices operating at room temperature for IR sensing and imaging. Antenna coupled metal-insulator-metal (MIM) diodes are potential candidates in this field. The reasons are miniaturizing features and femtosecond operation of these devices: smaller sizes lead to more pixels in limited areas and quantum tunneling phenomenon leads to faster operation. In this work, it is aimed to design and develop a device that can act as IR detector at room temperature.

The demand for infrared optical elements, particularly those made of chalcogenide materials, is rapidly increasing as thermal imaging becomes affordable to the consumer. The use of these materials in conjunction with established lens manufacturing techniques presents unique challenges relative to the cost sensitive nature of this new market. We explore the process from design to manufacture, and discuss the technical challenges involved. Additionally, facets of the development process including manufacturing logistics, packaging, supply chain management, and qualification are discussed.

As the desire to have compact multispectral imagers in various DoD platforms is growing, the dearth of multispectral optics is widely felt. With the limited number of material choices for optics, these multispectral imagers are often very bulky and impractical on several weight sensitive platforms. To address this issue, NRL has developed a large set of unique infrared glasses that transmit from 0.9 to > 14 μm in wavelength and expand the glass map for multispectral optics with refractive indices from 2.38 to 3.17. They show a large spread in dispersion (Abbe number) and offer some unique solutions for multispectral optics designs. The new NRL glasses can be easily molded and also fused together to make bonded doublets. A Zemax compatible glass file has been created and is available upon request. In this paper we present some designs, optics fabrication and imaging, all using NRL materials.

The growing demand for thermal imaging sensors and cameras has focused attention on the need for larger volumes of lower cost optics in this infrared region. A major component of the cost of thermal imaging lenses is the germanium content. As₄₀Se₆₀ was developed as a moldable, germanium-free chalcogenide glass that can serve as a low cost alternative to germanium and other infrared materials. This material also has promising characteristics for improved optical performance, especially with regard to reduced thermal sensitivity. As₄₀Se₆₀ has found acceptance as a material to be diamond turned or polished, but it is only now emerging as a legitimate candidate for precision glass molding. This paper will review chalcogenide molding and characterize As₄₀Se₆₀ for widespread use in highvolume thermal imaging optics. The relative advantages and disadvantages of As₄₀Se₆₀ as compared to other chalcogenide glasses will also be discussed.

Graded index (GRIN) optics offer potential for both weight savings and increased performance but have so far been limited to visible and NIR bands (wavelengths shorter than about 0.9 μm). NRL is developing a capability to extend GRIN optics to longer wavelengths in the infrared by exploiting diffused IR transmitting chalcogenide glasses. These IR-GRIN lenses are compatible with all IR wavebands (SWIR, MWIR and LWIR) and can be used alongside conventional wideband materials. Traditional multiband IR imagers require many elements for correction of chromatic aberrations, making them large and heavy and not well-suited for weight sensitive platforms. IR-GRIN optical elements designed with simultaneous optical power and chromatic correction can reduce the number of elements in wideband systems, making multi-band IR imaging practical for platforms including small UAVs and soldier handheld, helmet or weapon mounted cameras. The IR-GRIN lens technology, design space and anti-reflection considerations are presented in this paper.

Narcissus is caused by the reflection of the cold stop off a lens surface back to the image plane of a cooled infrared system and can be very difficult to remove from a lens design perspective. New infrared GRIN materials show the ability to reduce the amount of narcissus in an optical system without the reduction in performance or addition of optical elements.

With the increase in demand for infrared optics for thermal applications and the use of glass molding of chalcogenide materials to support these higher volume optical designs, an investigation of changes to the optical properties of these materials is required. Typical precision glass molding requires specific thermal conditions for proper lens molding of any type of optical glass. With these conditions a change (reduction) of optical index occurs after molding of all oxide glass types and it is presumed that a similar behavior will happen with chalcogenide based materials. We will discuss the effects of a typical molding thermal cycle for use with commercially and newly developed chalcogenide materials and show results of index variation from nominally established material data.

Gradient index (GRIN) optics have been an up-and-coming tool in the world of optics. By combining an index gradient with a surface curvature the number of optical components for a lens system can often be greatly reduced. Their use in the realm of infra-red is only becoming realized as new efforts are being developed to create materials that are suitable and mutually compatible for these optical components. The materials being pursued are the chalcogenide based glasses. Small changes in elemental concentrations in these glasses can have significant effects on physical and optical properties. The commonality between these glasses and their widely different optical properties make them prime candidates for GRIN applications. Traditional methods of metrology are complicated by the combination of the GRIN and the curvature of the element. We will present preliminary data on both destructive and non-destructive means of measuring the GRIN profile. Non-destructive methods may require inference of index through material properties, by careful measurement of the individual materials going into the GRIN optic, followed by, mapping measurements of the GRIN surface. Methods to be pursued are micro Raman mapping and CT scanning. By knowing the properties of the layers and accurately mapping the interfaces between the layers we should be able to back out the index profile of the GRIN optic and then confirm the profile by destructive means.

The proliferation of diffractive optics technologies into military and consumer markets has been driven by advancements in modeling, fabrication, and performance characterization of diffractive optical elements.

Diffractive optics offers additional degrees of freedom for controlling the propagation, dispersion, and polarization of light in photonic instruments. It provides instrumentation developers and optical designers with additional flexibility in systems' architectures, resulting in solutions with reduced overall size and weight, as well as enhanced performance characteristics. The benefits of diffractive optics are becoming especially important in spectral regions where high optical quality materials are sparse or not available. That applies especially to the long-wave infrared and THz spectral regions, where diffractive optical elements perform exceptionally well.

This paper presents examples of optical systems employing diffractive optical elements, emphasizing unique benefits enabled by the use of diffractive optics in modern photonic instruments. It also outlines certain areas of further diffractive optics developments that are expected to provide significant system-level performance benefits.

Today’s battlefield is evolving at light speed. Our war fighters are being tasked with highly complex missions requiring the very best technology our industry can offer. The demand for advanced ISR platforms is challenging designers and engineers in the optics industry to push the envelope and develop wider band solutions to support multiple and broadband sensor platforms. Recently, significant attention has been directed towards the development of optical systems that enable simultaneous operation in the visible and shortwave infrared spectral wavebands.

This paper will present a review of the evolution of StingRay Optics’ GhostSight™ continuous zoom optics that offer broad chromatic imaging capabilities from the visible through the shortwave infrared spectrum.

BAE Systems has developed an improved tool for exporting optical design coordinates to Computer-Aided Drafting (CAD) software. Existing scripts within common lens design packages export element shapes and rays which is enough for standard systems, but complex system design requires knowledge of surface vertices and coordinates for each component. Fixed coordinates for each element allows the mechanical engineer to place parts more accurately than allowed by the standard surface export algorithms, as well as locking optical elements in space so that mating surfaces do not inadvertently move optical elements during mechanical optimization. Including optical element vertex coordinates is useful for rotationally-symmetric systems, especially after multiple design iterations, and is essential for multi-channel, off-axis systems where apertures are not centered on surface vertices.

The demand for high performance, lightweight mirrors was historically driven by aerospace and defense (A&D) but now we are also seeing similar requirements for commercial applications. These applications range from aerospace-like platforms such as small unmanned aircraft for agricultural, mineral and pollutant aerial mapping to an eye tracking gimbaled mirror for optometry offices. While aerospace and defense businesses can often justify the high cost of exotic, low density materials, commercial products rarely can. Also, to obtain high performance with low overall optical system weight, aspheric surfaces are often prescribed. This may drive the manufacturing process to diamond machining thus requiring the reflective side of the mirror to be a diamond machinable material.

This paper summarizes the diamond machined finishing and coating of some high performance, lightweight designs using non-exotic substrates to achieve cost effective mirrors. The results indicate that these processes can meet typical aerospace and defense requirements but may also be competitive in some commercial applications.

An ultra-low surface finishing process for 6061 T6 type aluminum has been developed by Corning Incorporated, Specialty Materials Division, and has been successfully applied to mirrors up to 13 inches in diameter. This paper presents finish and figure data achieved from the mirror finishing process. Mirror stability is demonstrated through Pre and post thermal cycle surface figure measurements; temperature range of cycle -55°C to +70°C. As an added benefit, the process enables the use of deterministic finishing and enhances the reflective optics resistance to corrosion. Survivability of the reflective optic is evaluated through extended humidity testing.

In the omni-directional optical system used for real-time surveillance, we established the theory of basic optical design for a two-reflector catadioptric omni-directional optical system which has a convex primary mirror and a plane secondary mirror as its reflection imaging part. We also established an algorithm and programmed to analyze the variables of the theory. By using this method, the key optical elements related to the primary and secondary mirrors in the system can be simply and easily designed based on the optical system variables such as radius of curvature for the primary mirror and position of the secondary mirror, and location and radius of entrance pupil of the refractive imaging optics. And we achieved readily and successfully an infrared omni-directional optical system for night vision and surveillance of defense and safety by using the basic design theory.

In recent years there has been a drive towards miniaturized cooled IDCA solutions for low-power, low-mass, low-size products (SWaP). To support this drive, coolers are developed optimized for high-temperature, low heat load dewar-detector assemblies. In this paper, Thales Cryogenics development activities supporting SWaP are presented. Design choices are discussed and compared to various key requirements. Trade-off analysis results are presented on drive voltage, cold finger definition (length, material, diameter and sealing concept), and other interface considerations, including cold finger definition. In parallel with linear and rotary cooler options, designs for small-size high-efficiency drive electronics based on state-of-the-art architectures are presented.

The world growth in research and development of High Operating Temperature (HOT) IR detectors impels development and optimization of suitable cryocoolers. The current developments at RICOR are focused on the SWAP-oriented design process, meaning small Size, low Weight and low Power consumption, providing proper cryocoolers for future hand held thermal imagers.

This paper shows the progress made during development of "HOT" cryocooler prototypes, and engineering preproduction series cryocoolers working at the FPA temperature range of 130 - 200K. Three different cryocooler models based on rotary & linear design concepts are presented below. The progress with development of electronic control modules providing minimized regulated power consumption is also shown.

Boil-off isothermal calorimetry of Integrated Dewar-Detector Assemblies (IDDA) is a routine part of acceptance testing. In this traditional approach, the cryogenic liquid coolant (typically LN2) is allowed to naturally boil off from the Dewar well to the atmosphere. The parasitic heat load is then evaluated as the product of the latent heat of vaporization and the "last drop" boil-off rate monitored usually by a mass flow meter.

An inherent limitation of this technique is that it is applicable only at the fixed boiling temperature of the chosen liquid coolant, for example, 77K for LN2. There is a need, therefore, to use other (often exotic) cryogenic liquids when calorimetry is needed at temperatures other than 77K. A further drawback is related to the transitional nature of last drop boiling, which manifests itself in development of enlarged bubbles, explosions and geysering. This results in an uneven flow rate and also affects the natural temperature gradient along the cold finger. Additionally, mass flow meters are known to have limited measurement accuracy.

The above considerations especially hold true for advanced High Operational Temperature IDDAs, typically featuring short cold fingers and working at 150K and above. In this work, we adapt the well-known technique of dual-slope calorimetry and show how accurate calorimetry may be performed by precooling the IDDA and comparing the warm-up slopes of the thermal transient processes under different trial added heat loads. Because of the simplicity, accuracy and ability to perform calorimetry literally at any temperature of interest, this technique shows good potential for replacing traditional boil-off calorimetry.

As the scientific requirements of microsatellites migrate closer to those of larger, more-expensive traditional satellites, the technical requirements on the key enabling components and subsystems are becoming more demanding. If the utility of microsatellites is ever to expand to include high performance mid-wave infrared (MWIR) and short-wave infrared (SWIR) sensors, significant advancement in the state of art of small cryocooler systems is required. The Microsat Cryocooler System (MCS) is a radiation hard, space-qualified integrated cryocooler assembly (ICA) for CubeSat and microsat applications. The ICA includes a high reliability tactical cryocooler, a miniature set of Low Cost Cryocooler Electronics (mLCCE), the thermal management components, and the isolation structure. As is the case with the larger LCCE from which it was derived, the mLCCE supports any of a wide range of linear cryocoolers in its design output power range (nominally 25W). With minor adaptation, rotary coolers are also supported.

This paper presents the initial results from the brassboard phase of the MCS Program. A high fidelity set of cryocooler electronics with a well-defined upgrade path to a space-compatible design has been built and tested with the target cryocooler. Those data are presented. In addition to reducing risk for the spaceflight design to follow, these electronics are being released as an intermediate product for high-end tactical applications where the plug-and-play operability among different coolers and the enhanced level of control and programmability (relative to typical tactical cooler electronics) are desired.

The overall CubeSat-compatible mechanical subsystem design is also presented, including descriptions of the thermal management and vibration isolation approaches.

The growth in world demand for infrared missile warning systems (MWS) has impelled the development of new technologies, in particular, special ruggedized cryogenic coolers. Since the cryocooler is a core component in ruggedized platforms, RICOR has met the challenge by developing new models able to withstand high ambient temperatures above 110°C, as well as harsh vibration levels, both derived from airborne fighter applications. One of the development efforts focused on a cryocooler regenerator and cold finger optimization, in order to achieve high cooling capacity at 95K FPA and the efficiency of about 5.3 % at 102 °C.

In order to withstand harsh environmental vibration and high ambient temperature range, the mechanical parts of the cryocoolers were designed and tested for a high structural safety factor along with weight minimization. The electronic design concept was based on encapsulated controllers, the PCB of which has been designed with internal heat sinking paths and special components able to withstand ambient temperatures of up to 125°C.

As a final stage of development, four cryocooler models (K544, K549, K527 and K508) were successfully qualified under harsh environmental conditions, both by RICOR and by system manufacturers. Also life demonstration tests were performed with these models. The cryocoolers were designed and tested successfully to meet requirements of military standards MIL- STD-704D, MIL-STD- 461E and MIL-STD-810F reflecting real mission profiles in harsh environment.

The moving magnet linear compressors are very popular in the tactical miniature stirling cryocoolers. The magnetic circuit of LFC3600 moving magnet linear compressor, manufactured by Kunming institute of Physics, was studied in this study. Three methods of the analysis theory, numerical calculation and experiment study were applied in the analysis process. The calculated formula of magnetic reluctance and magnetomotive force were given in theoretical analysis model. The magnetic flux density and magnetic flux line were analyzed in numerical analysis model. A testing method was designed to test the magnetic flux density of the linear compressor. When the piston of the motor was in the equilibrium position, the value of the magnetic flux density was at the maximum of 0.27T. The results were almost equal to the ones from numerical analysis.

This paper presents recent improvements introduced in production lines of Mid-Wavelength Infra-Red (MWIR) and Long-Wavelength Infra-Red (LWIR) HgCdTe detectors that increase performances, image quality, and reliability. This was achieved thanks to accurate characterization of RMS noise distributions. Based on many MWIR and LWIR devices RMS distributions, a RMS noise distribution model that accounts for both Background Limited diodes and 1/f noise affected isolated diodes is first proposed. Then, a figure of merit for quantifying the defective pixels is introduced. This figure of merit is shown to be easy to use and robust to statistical variability. Moreover, it does also very well correlate with physics : there is high correlation between the total number of calculated defects and other figures of merit that gauge the material quality or the low frequency noise. The ability to accurately and efficiently quantify RMS noise benefits to Sofradir in its development of highly reliable and performant technologies. Such benefits are illustrated on the latest Sofradir MWIR and LWIR technologies that are demonstrated to be very robust regarding thermal stress and thermal cycling. Finally those technologies are shown to reach high image quality and stability.

In multiple publications over the last years, MCT MBE on GaAs has been shown to be a very versatile and promising material system and indeed may be the prime candidate among the alternative substrates for the fabrication of high-performance detectors across the whole IR composition range. In this paper we report on successful growth of MCT on GaAs over the composition range 0.2 < x(Cd) < 0.8. A single color MWIR 640 × 512, 15 μm pitch detector fabricated from this material with an operability of 99.71% at an operating temperature of 120 K is presented. In the LWIR region, an operability of 99.48% at 65 K has been achieved with a 1280 × 1024, 15 μm pitch detector. Finally we report on preliminary results of a dual-color 640 × 512, 20 μm pitch detector with cutoff wavelengths in the 3 - 4 and 4 - 5 μm range.

Thermal imagers based on cooled LWIR Modules are the choice for many Army applications in battlefield conditions like e.g. Gunner and Commander Sights in armored vehicles or Pilotage and Targeting Sights for helicopters. AIM has developed and produces LWIR FPAs based on liquid phase epitaxy (LPE) grown MCT on in-house grown CdZnTe substrates with different formats up to detector arrays with 1280x1024 elements in a 15μm pitch. LWIR detector arrays with different spectral cut-off wavelengths in the range of 9μm up to >12μm have been produced and characterized. For cost reduction a fabrication of molecular beam epitaxy (MBE) grown MCT on GaAs substrates is developed.

Critical performance parameters of the detector arrays are temporal noise at low frequencies and the residual fixed pattern noise after non-uniformity correction. A performance-limiting factor of a LWIR FPA is also the available full well capacity (FWC) of the readout integrated circuit (ROIC) for signal integration. AIM has done a redesign of the standard 640x512, 15μm pitch ROIC using now 0.18μm Si-CMOS technology. The available FWC for signal integration could be significantly increased resulting in better NETD performance.

Further developments are done for pitch reduction to realize LWIR modules also with 12μm and 10μm pixel pitch. The FPAs are integrated in compact dewar cooler configurations using different kinds of cooler types, like AIM’s split linear coolers SX095 or SX040 or rotary integral types depending whatever fits best to the application. The paper will present the development status and performance results of AIM’s latest improved MCT LWIR Modules.

This paper presents recent developments done at CEA-LETI Infrared Laboratory on processing and characterization of p-on-n HgCdTe (MCT) planar infrared focal plane arrays (FPAs) in LWIR and VLWIR spectral bands. These FPAs have been grown using liquid phase epitaxy (LPE) on a lattice matched CdZnTe substrate. This technology presents lower dark current and lower serial resistance in comparison with n-on-p vacancy doped architecture and is well adapted for low flux detection or high operating temperature. This architecture has been evaluated for space applications in LWIR and VLWIR spectral bands with cutoff wavelengths from 10μμm up to 17μm at 78K. Innovations have been introduced to the technological process to form a heterojunction with a LPE growth technique. The aim was to lower dark current at low temperature, by decreasing currents from the depletion region. Electro-optical characterizations on p-on-n photodiodes have been performed on QVGA format FPAs with 30μm pixel pitches. Results show excellent operabilities in current and responsivity, with low dispersion and noise limited by current shot-noise. Studies performed on dark current show that dark current densities are consistent with the heuristic prediction law "Rule07" at 78K. Below this temperature, dark current varies as a pure diffusion current.

Thermal stability of Atomic Layer Deposition Al₂O₃ film on HgCdTe was investigated by Al₂O₃ film post-deposition annealing treatment and Metal-Insulator-Semiconductor device low-temperature baking treatment. The effectiveness of Al₂O₃ film was evaluated by measuring the minority carrier lifetime and capacitance versus voltage characteristics. After annealing treatment, the minority carrier lifetime of the HgCdTe sample presented a slight decrease. Furthermore, the fixed charge density and the slow charge density decreased significantly in the annealed MIS device. After baking treatment, the fixed charge density and the slow charge density of the unannealed and annealed MIS devices decreased and increased, respectively.

Infrared focal plane array technology has evolved dramatically over the last 50 years. The author has been privileged to participate in this remarkable evolution, working totally within the confines of one of the most significant and remaining US players in the focal plane game, namely Texas Instruments, later to become DRS Technologies. This presentation describes a journey from the Common Module through second and third generation infrared systems in the USA up to the exciting developments of the present day ultra-small pixel technology. It represents an attempt to detail both the technology development of the time together with some of its associated drama as viewed from the author’s particular perspective. Thoughts on the lessons learned from this journey and their possible impact on future technology development will be discussed.

The fabrication of high performance infrared detectors using mercury cadmium telluride (MCT) grown on GaAs substrates by Metal Organic Vapour Phase Epitaxy (MOVPE) is now an established mature production process at Selex ES. Recent years have seen a substantial reduction in MCT pixel sizes, driven by system requirements for increased resolutions, lower power consumption and reduced costs. From initial devices with 30μm pixels, previous developments have produced MOVPE grown MCT arrays of 24μm, 20μm and 16μm pixels with response in short, long, mid and dual wavebands (SWIR, LWIR, MWIR and DWIR). High definition (HD) format and multi-megapixel arrays of 12μm MWIR pixels have also been produced using MOVPE grown MCT. The mesa structure of MOVPE grown MCT pixels inherently controls optical scattering, inter-pixel cross-talk, carrier diffusion and other blurring defects to negligible levels. This allows the goal for pixel size reduction to ultimately be determined by optical diffraction and Nyquist- Shannon sampling criteria alone.

This paper discusses the development of a new MCT detector at Selex ES, introducing the next generation of small pixels on an 8μm pitch. Transition to smaller silicon design rules has enabled the pixel size reduction in the read-out integrated circuit (ROIC) to be achieved with minimum sacrifice of storage capacity. The ROIC has a completely digital control with on-chip digital generation of photodiode bias voltage. Low power proximity electronics providing a fully digitised output have been developed to ease interface with the detector. Characteristics of the pixel design together with measured performance of the detector and its application to infrared sensor development, including updates of standard definition (SD) products to HD and better performance, will be addressed.

Sofradir was first to show a 10μm focal plane array (FPA) in DSS 2012, and announced the DAPHNIS 10μm product family back in 2014. This pixel pitch is key for enabling more compact sensors and increased resolution. SOFRADIR recently achieved outstanding MTF demonstration at this pixel pitch, which clearly demonstrate the benefit to users of adopting 10μm pixel pitch focal plane array based detectors. The last results, and associated gain in detection performance, are discussed in this paper.

Concurrently to pitch downsizing, SOFRADIR also works on a global offer using digital interfaces and smart pixel functionalities. This opens the road to enhanced functionalities such as improved image quality, higher frame rate, lower power consumption and optimum operation for wide thermal conditions scenes. This paper also discusses these enhanced features and strategies allowing easier integration of the detector in the system.

We report on a new high definition high charge capacity 2.1 Mpixel MWIR Infrared Focal Plane Array. This high definition (HD) FPA utilizes a small 5 um pitch pixel size which is below the Nyquist limit imposed by the optical systems Point Spread Function (PSF). These smaller sub diffraction limited pixels allow spatial oversampling of the image. We show that oversampling IRFPAs enables improved fidelity in imaging including resolution improvements, advanced pixel correlation processing to reduce false alarm rates, improved detection ranges, and an improved ability to track closely spaced objects. Small pixel HD arrays are viewed as the key component enabling lower size, power and weight of the IR Sensor System. Small pixels enables a reduction in the size of the systems components from the smaller detector and ROIC array, the reduced optics focal length and overall lens size, resulting in an overall compactness in the sensor package, cooling and associated electronics. The highly sensitive MWIR small pixel HD FPA has the capability to detect dimmer signals at longer ranges than previously demonstrated.

"Lucky-region" fusion (LRF) is a synthetic imaging technique that has proven successful in enhancing the quality of images distorted by atmospheric turbulence. The LRF algorithm extracts sharp regions of an image obtained from a series of short exposure frames from fast, high-resolution image sensors, and fuses the sharp regions into a final, improved image. In our previous research, the LRF algorithm had been implemented on CPU and field programmable gate array (FPGA) platforms. The CPU did not have sufficient processing power to handle real-time processing of video. Last year, we presented a real-time LRF implementation using an FPGA. However, due to the slow register-transfer level (RTL) development and simulation time, it was difficult to adjust and discover optimal LRF settings such as Gaussian kernel radius and synthetic frame buffer size. To overcome this limitation, we implemented the LRF algorithm on an off-the-shelf graphical processing unit (GPU) in order to take advantage of built-in parallelization and significantly faster development time. Our initial results show that the unoptimized GPU implementation has almost comparable turbulence mitigation to the FPGA version. In our presentation, we will explore optimization of the LRF algorithm on the GPU to achieve higher performance results, and adding new performance capabilities such as image stabilization.

In this paper we present initial test results of the Near Infrared Readout and Controller ASIC (NIRCA), designed for large area image sensors under contract from the European Space Agency (ESA) and the Norwegian Space Center. The ASIC is designed to read out image sensors based on mercury cadmium telluride (HgCdTe, or MCT) operating down to 77 K. IDEAS has developed, designed and initiated testing of NIRCA with promising results, showing complete functionality of all ASIC sub-components. The ASIC generates programmable digital signals to clock out the contents of an image array and to amplify, digitize and transfer the resulting pixel charge. The digital signals can be programmed into the ASIC during run-time and allows for windowing and custom readout schemes. The clocked out voltages are amplified by programmable gain amplifiers and digitized by 12-bit, 3-Msps successive approximation register (SAR) analogue-to-digital converters (ADC). Digitized data is encoded using 8-bit to 10-bit encoding and transferred over LVDS to the readout system. The ASIC will give European researchers access to high spectral sensitivity, very low noise and radiation hardened readout electronics for astronomy and Earth observation missions operating at 77 K and room temperature. The versatility of the chip makes the architecture a possible candidate for other research areas, or defense or industrial applications that require analog and digital acquisition, voltage regulation, and digital signal generation.

Previously, we adopted the resonator-QWIPs and increased the FPA QE to 30 − 40%. In this work, we performed a systematic theoretical analysis on the potential performance based on this new detector structure. In this analysis, the doping density and the number of quantum wells are varied to obtain different detector characteristics. For 25 μm pixel pitch, 10 Me⁻ integrated charge, and F/2 optics, the analysis shows that a 9.2 μm cutoff R-QWIP optimized for high temperature operation could provide 20 mK NEΔT at τ_int = 2.6 ms when operating at T = 80 K. An R-QWIP with a 10.2 μm cutoff could achieve the same with τ_int = 1.3 ms at T = 74 K. Similar NEΔT can also be achieved with smaller pixel pitch down to 6 μm for both cutoffs with a more relaxed operating condition where the f-number is 1, τ_int is 5 ms, and T is 70 K. We provide preliminary test detector data to support this analysis.

We first derive a formula that can successfully describe the device nonlinearity between the IR incidence corresponding to the blackbody temperature T and the pixel output V for infrared detectors such as QWIPs or QDIPs, which have a peak (not cutoff) type photo response.

Second, using this formula, we show that, in theory, conventional "two-point correction" can completely correct the non-uniformity; therefore, in the case of QWIP- or QDIP-FPA, the origin of the NUC incompleteness, that is, the origin of the residual non-uniformity in an IR image, is the nonlinear input-output characteristics in the electronics.

Last, we show that the nonlinearity in the electronics can be corrected by using our formula to reconstruct an almost completely non-uniformity corrected IR image.