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This study describes a new method to compensate bias heating effects for microbolometer readout circuits using a finely adjustable CMOS resistance as a reference. The proposed self calibrated cooler-less structure dynamically modifies CMOS resistance during integration time. This compensation structure also includes a feedback loop, which forces the oscillators to work in the linear region. The proposed self calibration circuit is designed and simulated using a 65-nm process node, and achieves 40 mK NETD (Noise Equivalent Temperature Difference) value for one percent resistance non-uniformity of pixel resistance values across one row. The layout area of this circuit occupies approximately one third of the layout area used by classical readout circuits. The circuit dissipates one third of power compared with classical microbolometer readout approaches.

We report a novel design for bolometric infrared detector operating at the long-wave infrared (LWIR) range for high-resolution human body temperature sensing and monitoring. We propose to incorporate efficient plasmonic absorber and high-responsivity VO2 nanobeam biased at transition temperature in our design to facilitate improvement in both aspects – thermal resolution and spatial resolution. The integration of plasmonic absorber allows efficient and selective radiation absorption. The use of a transducing nanobeam placed in close proximity to the plasmonic local heaters allows the radiation energy to be electronically readable. The use of nanobeam instead of a film in the detector allows over two-orders of magnitude improvement in responsivity owing to the large length to cross-sectional area ratio. Additionally, the use of nanobeam reduces the thermal mass and improves the bandwidth. Our calculation suggests a responsivity of as high as 700 kV/W at 100 Hz for a detector of only $12\,\,\mu \text{m}\,\,\times 12\,\,\mu \text{m}$ pixel size. Also, the theoretical noise equivalent temperature difference is calculated to be as low as 3.67 mK which is almost an order of improvement than the state-of-the-art bolometric LWIR detectors with larger pixel dimensions.

High-performance InAs/GaSb type-II superlattice infrared detectors and focal plane arrays (FPAs) are normally grown by molecular beam epitaxy (MBE). In this work, we demonstrate the first long-wavelength infrared InAs/GaSb superlattice FPA grown by metalorganic chemical vapor deposition (MOCVD) with clear image. High-quality superlattice material was obtained evidenced by sharp X-ray diffraction peaks and atomic flat surface. Electrical and optical measurements performed on single element detectors showed a 50% cut-off wavelength of $\sim 10.1~\mu \text{m}$ , a dark current density of $2.5\times 10^{-5}$ A/cm2, a peak responsivity of 0.88 A/W and a peak detectivity of $1.7\times 10^{11}$ cm $\cdot $ Hz1/2/W at 80 K. A $320\times256$ FPA with $30~\mu \text{m}$ pixel pitch was then fabricated. With an integration time of 1.9 ms and an applied bias of -0.1 V, the FPA shows an average operability of 96.96%, a non-uniformity of 4.97%, a noise equivalent temperature difference of 51.1 mK and a peak detectivity of $2.3\times 10^{10}$ cm $\cdot $ Hz1/2/W at 80 K without thinning down the substrate.

We present the metrological characterization and calibration of three different types of thermographic cameras for quantitative temperature measurement traceable to the International Temperature Scale (ITS-90). Relevant technical specifications – i.e., the non-uniformity of the pixel-to-pixel responsivity, the inhomogeneity equivalent temperature difference (IETD), the noise equivalent temperature difference (NETD), and the size-of-source effect (SSE) – are determined according to the requirements given in the series of Technical Directives VDI/VDE 5585. The measurements are performed with the camera calibration facility of the Physikalisch-Technische Bundesanstalt. The data reference method is applied for the determination and improvement of the non-uniformity, leading to an improved IETD for all three cameras. Finally, the cameras are calibrated according to the different procedures discussed in the VDI/VDE 5585 series. Results achieved with the different calibration procedures are compared for each type of camera and among the three cameras. An uncertainty budget for the calibration of each camera is given according to GUM (ISO, 1995) and VDI/VDE 5585.

The goal of the presented article is to investigate the impact of warm filters and elevated background temperature on the operation of an uncooled wideband camera used for optical gas imaging (OGI). The noise equivalent temperature difference (NETD) parameter is measured for a VOx wideband OGI camera built for the purpose of the experiments, with and without an interference filter. The results demonstrate that warm filters have a clear effect on the performance of the OGI camera. Based on the standard NETD measurement procedures, a camera-scene noise equivalent temperature difference (CSNETD) parameter is proposed to quantify both the camera and scene noise. The CSNETD measurements are used to evaluate the impact of elevated background temperature on the performance of the OGI camera. Finally, the camera is used to image methane leaks in the mid-wave infrared (MWIR) and long-wave infrared (LWIR) bands. The results are consistent with the presented NETD/CSNETD measurements and confirm the impact of warm filters and elevated background temperature on the operation of the uncooled thermal imaging camera.

For improving the dynamic range and sensitivity at high power load, we have integrated superconductor-insulator-normal metal-insulator-superconductor (SINIS) bolometers with a frequency selective surface (FSS)-based distributed absorber formed by a series and parallel array consisting of 25 annular antenna elements, each containing two SINIS bolometers. By using a design with 50 bolometers, we reduce incident power load on each bolometer, increase sensitivity and saturation power which is important for ground-based and balloon-borne telescopes with high background power loads. Our main detector pixel is optimized for a frequency band centered at 345GHz. The detectors are matched to incoming telescope beam by a back-to-back horn with a back reflector. Such a configuration improves both the efficiency and the bandwidth of the receiver. Measured voltage responsivity approaches 210(9) VW with an amplifier-limited voltage noise of 20nVHz(12), which corresponds to a NEP 10(-17) WHz(12). The linear voltage response for incoming power is observed for absorbed power of about 5 pW. The current responsivity for parallel array is 210(4) AW and the shot noise limited intrinsic noise equivalent power is NEP 510(-18)WHz(12). The noise equivalent temperature difference is NETD 100 KHz(12) at 2.7-K background radiation temperature.

This paper presents a novel and power efficient readout architecture for uncooled microbolometers that offers adequate noise performance along with a circuit-based method for self-heating compensation. The proposed method employs an event-generation scheme and a time-mode readout chain to achieve dynamic mode of operation resulting in low power. The readout chain consists of a capacitive transimpedance amplifier (CTIA) based current-to-time converter followed by a two stage time-to-digital converter (TDC). The CTIA employs a novel integration scheme for time amplification along with a modified reset mechanism to achieve self-heating compensation. We also present a model to analyze the implications of time-mode readout on imager operation. An experimental readout chip, based on this approach, has been designed using a 130 nm bulk CMOS technology. The proposed architecture offers robust frontend processing and achieves a per channel power consumption of $66~\mu \text{W}$ , which is considerably lower than the most recently reported designs, while maintaining better than 10-mK readout noise equivalent temperature difference (NETD).

Today’s long-range infrared cameras (LRIRC) are used in many systems for the protection of critical infrastructure or national borders. The basic technical parameters of such systems are noise equivalent temperature difference (NETD); minimum resolvable temperature difference (MRTD); and the range of detection, recognition and identification of selected objects (DRI). This paper presents a methodology of the theoretical determination of these parameters on the basis of technical data of LRIRCs. The first part of the paper presents the methods used for the determination of the detection, recognition and identification ranges based on the well-known Johnson criteria. The theoretical backgrounds for both approaches are given, and the laboratory test stand is described together with a brief description of the methodology adopted for the measurements of the selected necessary characteristics of a tested observation system. The measurements were performed in the Accredited Testing Laboratory of the Institute of Optoelectronics of the Military University of Technology (AL IOE MUT), whose activity is based on the ISO/IEC 17025 standard. The measurement results are presented, and the calculated ranges for a selected set of IR cameras are given, obtained on the basis of the Johnson criteria. In the final part of the article, the obtained measurement results are presented together with an analysis of the measurement uncertainty for 10 LRIRCs. The obtained measurement results were compared to the technical parameters presented by the manufacturers.

In this study, a portable and large-area blackbody system was developed following a series of processes including design, computational analysis, fabrication, and experimental analysis and evaluation. The blackbody system was designed to be lightweight (5 kg), and its temperature could exceed the ambient temperature by up to 15 &deg, C under operation. A carbon-fiber-based heat source was used to achieve a uniform temperature distribution. A heat shield fabricated from an insulation material was embedded at the opposite side of the heating element to minimize heat loss. A prototype of the blackbody system was fabricated based on the design and transient coupled electro-thermal simulation results. The operation performance of this system, such as the thermal response, signal transfer function, and noise equivalent temperature difference, was evaluated by employing an infrared imaging system. In addition, emissivity was measured during operation. The results of this study show that the developed portable and large-area blackbody system can be expected to serve as a reliable reference source for the calibration of aerial infrared images for the application of aerial infrared techniques to remote sensing.

The MODerate-resolution Imaging Spectroradiometer (MODIS) is a premier Earth-observing sensor of the early 21st century, flying onboard the Terra (T) and Aqua (A) spacecraft. Both instruments far exceeded their six-year design life and continue to operate satisfactorily for more than 15 and 13 years, respectively. The MODIS instrument is designed to make observations at nearly a 100% duty cycle covering the entire Earth in less than two days. The MODIS sensor characteristics include a spectral coverage from 0.41 to 14.4 $\mu\mbox{m}$ , of which those wavelengths ranging from 3.7 to 14. 4 $\mu\mbox{m}$ cover the thermal infrared region which is interspaced in 16 thermal emissive bands (TEBs). Each of the TEB contains ten detectors which record samples at a spatial resolution of 1 km. In order to ensure a high level of accuracy for the TEB-measured top-of-atmosphere radiances, an onboard blackbody (BB) is used as the calibration source. This paper reports the noise characterization and performance of the TEB on various counts. First, the stability of the onboard BB is evaluated to understand the effectiveness of the calibration source. Next, key noise metrics such as the noise equivalent temperature difference and the noise equivalent dn difference (NEdN) for the various TEBs are determined from multiple temperature sources. These sources include the nominally controlled BB temperature of 290 K for T-MODIS and 285 K for A-MODIS, as well as a BB warm up–cool down cycle that is performed over a temperature range from roughly 270 to 315 K. The space-view port that measures the background signal serves as a viable cold temperature source for measuring noise. In addition, a well characterized Earth-view target, the Dome Concordia site located in the Antarctic plateau, is used for characterizing the stability of the sensor, indirectly providing a measure of the NEdN. Based on this rigorous characterization, a list of the noisy and inoperable detectors for the TEB for both instruments is reported to provide the science user communities quality control of the MODIS Level 1B calibrated product.

This paper presents the design of a current-mode CMOS self-amplified imager operating in dark conditions, for thermal imaging, which provides an innovative solution for precision thermal contact mapping. Possible applications of this imager range from 3D CMOS integrated circuits to the study of in-vivo biological samples. It can provide a thermal map, static or dynamic, for the measurement of temperature microgradients. Some adaptations are required for the optimization of this self-amplified image sensor since it responds exclusively to the dark currents of the photodiodes throughout the array. The sensor is designed in a standard CMOS process and requires no post-processing steps. The optimized image sensor operates with integration times as low as one &mu, s and can achieve both SNR and dynamic range compatible to those of sensors available on the market, estimated as 87dB and 75dB, respectively, noise equivalent temperature difference can be as low as 10mK, and detection errors as low as &plusmn, 1%. Furthermore, under optimal conditions the self-amplification process enables a simple form of CDS, enhancing the overall sensor noise performance.

Semi-Conductor Devices’ long-wave infrared 640 × 512/15-μm pitch type II superlattice detector is based on an XBp design with an InAs/GaSb absorbing layer and an InAs/AlSb barrier layer. The barrier architecture ensures a low, diffusion-limited, dark current and allows stable passivation to all fabrication steps. It is shown that the dark current is about 10 times the Rule 07 value and corresponds to a minority carrier lifetime of about 10 ns, while the quantum efficiency can approach within 10% of the HgCdTe value for realistic detector parameters. Detectors are now being manufactured with a reasonable yield for an operability above 99.5%, and a stable and reproducible noise equivalent temperature difference of

This work presents the simulation results and design rules of a new sensor for IR-detection using the thermoelectric effect. Within the Seebeck-effect, thermopiles generate a voltage based on a temperature gradient inside the structure. State of the art thermopiles are manufactured as two-dimensional structures directly on a substrate. Here, a possible method of 3D integration is shown, where the thermoelectric materials are fabricated as thin tubes using an atomic layer deposition (ALD) process. These tubes are connected to an IR-absorber on top, where the IR-radiation causes a temperature gradient relative to the substrate. This has the advantages to achieve a fill factor of nearly 100%. In comparison to microbolometers, the 3D thermopile is a passive structure, which does not need complex readout and supply circuits. Furthermore, the usage of energy harvesting is possible. Additionally, new array circuitry options are discussed to achieve a better signal-to-noise ratio. An electrical series connection of multiple sensors effects a rising specific detectivity and the noise equivalent temperature difference (NETD) decreases analogously. With this technique, groups of pixels of the detector can be merged to one "super-pixel" for detecting even marginal temperature changes of an object.

According to the parameters of various kinds of infrared imaging equipment was performance full automatic detection and evaluation of research in this paper. The evaluation system will to accuracy, slit function (SRF), minimum resolvable temperature difference (MRTD), minimum detectable temperature difference (MDTD) and noise equivalent temperature difference (NETD) and other parameters as the basis, the establishment of infrared imaging evaluation system database, to convergence of digital interface to realize automatic detection and evaluation of infrared imaging device, solving the technical problem of performance evaluation of grid infrared imaging equipment, ensure the accuracy of condition based maintenance for power transmission system.

The range of applications in which remote detection of chemical compounds is used extends from monitoring of technological processes through diagnostics of industrial installation and environmental control up to military applications. The methods and the devices used for the passive detection of selected gases are presented. The change in the signal reaching the camera caused by the presence of gas was calculated. The successful detection can be achieved if the absorption (or emission) of a gas cloud, located between object (background) and the camera, causes signal change greater or equal to noise equivalent temperature difference (NETD) of the camera.

We present our latest results on cooled p-on-n planar mercury cadmium telluride (MCT) photodiode technology. Along with a reduction in dark current for raising the operating temperature (T op), AIM INFRAROT-MODULE GmbH (AIM) has devoted its development efforts to shrinking the pixel size. Both are essential requirements to meet the market demands for reduced size, weight and power and high-operating temperature applications. Detectors based on the p-on-n technology developed at AIM now span the spectrum from the mid-wavelength infrared (MWIR) to the very long wavelength infrared (VLWIR) with cut-off wavelengths from 5 μm to about 13.5 μm at 80 K. The development of the p-on-n technology for VLWIR as well as for MWIR is mainly implemented in a planar photodetector design with a 20-μm pixel pitch. For the VLWIR, dark currents significantly reduced as compared to ‘Tennant’s Rule 07’ are demonstrated for operating temperatures between 30 K and 100 K. This allows for the same dark current performance at a 20 K higher operating temperature than with previous AIM technology. For MWIR detectors with a 20-μm pitch, noise equivalent temperature differences of less than 30 mK are obtained up to 170 K. This technology has been transferred to our small pixel pitch high resolution (XGA) MWIR detector with 1024 × 768 pixels at a 10-μm pitch. Excellent performance at an operating temperature of 160 K is demonstrated.

XBn or XBp barrier detectors exhibit diffusion-limited dark currents comparable with mercury cadmium telluride Rule-07 and high quantum efficiencies. In 2011, SemiConductor Devices (SCD) introduced “HOT Pelican D”, a 640 × 512/15-μm pitch InAsSb/AlSbAs XBn mid-wave infrared (MWIR) detector with a 4.2-μm cut-off and an operating temperature of ∼150 K. Its low power (∼3 W), high pixel operability (>99.5%) and long mean time to failure make HOT Pelican D a highly reliable integrated detector-cooler product with a low size, weight and power. More recently, “HOT Hercules” was launched with a 1280 × 1024/15-μm format and similar advantages. A 3-megapixel, 10-μm pitch version (“HOT Blackbird”) is currently completing development. For long-wave infrared applications, SCD’s 640 × 512/15-μm pitch “Pelican-D LW” XBp type II superlattice (T2SL) detector has a ∼9.3-μm cut-off wavelength. The detector contains InAs/GaSb and InAs/AlSb T2SLs, and is fabricated into focal plane array (FPA) detectors using standard production processes including hybridization to a digital silicon read-out integrated circuit (ROIC), glue underfill and substrate thinning. The ROIC has been designed so that the complete detector closely follows the interfaces of SCD’s MWIR Pelican-D detector family. The Pelican-D LW FPA has a quantum efficiency of ∼50%, and operates at 77 K with a pixel operability of >99% and noise equivalent temperature difference of 13 mK at 30 Hz and F/2.7.

This paper reports on a study comparing the noise performance of two relatively low-cost microbolometers to a high-grade photon detector as applied to optical lock-in thermography, a well-established broad area non-destructive inspection technique. The photon detector is shown to significantly outperform both microbolometers by margins inconsistent with their noise equivalent temperature detectivity specifications. It is demonstrated that this performance gap can be overcome by increasing observation time or optical illumination intensity. For practical situations in which such steps are plausible microbolometers may provide a viable alternative to photon detectors for optical lock-in thermography. This raises the prospect of applying this method to structural health monitoring, where the generally small size and low capital cost of microbolometers would be advantageous.

This paper reports an InAs/InAsSb strained-layer superlattice (SLS) mid-wavelength infrared detector and a focal plane array particularly suited for high-temperature operation. Utilizing the nBn architecture, the detector structure was grown by molecular beam epitaxy and consists of a 5.5 &micro, m thick n-type SLS as the infrared-absorbing element. Through detailed characterization, it was found that the detector exhibits a cut-off wavelength of 5.5 um, a peak external quantum efficiency (without anti-reflection coating) of 56%, and a dark current of 3.4 &times, 10-4 A/cm2, which is a factor of 9 times Rule 07, at 160 K temperature. It was also found that the quantum efficiency increases with temperature and reaches ~56% at 140 K, which is probably due to the diffusion length being shorter than the absorber thickness at temperatures below 140 K. A 320 &times, 256 focal plane array was also fabricated and tested, revealing noise equivalent temperature difference of ~10 mK at 80 K with f/2.3 optics and 3 ms integration time. The overall performance indicates that these SLS detectors have the potential to reach the performance comparable to InSb detectors at temperatures higher than 80 K, enabling high-temperature operation.

Uncooled infrared detectors have enabled the rapid growth of thermal imaging applications. These detectors are predominantly bolometers, reading out a pixel’s temperature change due to infrared radiation as a resistance change. Another uncooled sensing method is to transduce the infrared radiation into the frequency shift of a mechanical resonator. We present here highly sensitive resonant infrared sensors, based on thermo-responsive shape memory polymers. By exploiting the phase-change polymer as transduction mechanism, our approach provides 2 orders of magnitude improvement of the temperature coefficient of frequency. Noise equivalent temperature difference of 22 mK in vacuum and 112 mK in air are obtained using f/2 optics. The noise equivalent temperature difference is further improved to 6 mK in vacuum by using high-Q silicon nitride membranes as substrates for the shape memory polymers. This high performance in air eliminates the need for vacuum packaging, paving a path towards flexible non-hermetically sealed infrared sensors., Though resonant infrared (IR) detectors are an attractive thermal imaging technology owing to its high performance potential, realizing devices with high sensitivity remains a challenge. Here, the authors report high-sensitivity resonant IR sensors based on thermo-responsive shape memory polymers.

The development of performant integrated detectors, which are sensitive to quantum fluctuations of coherent light, are strongly desired to realize a scalable and determinist photonic quantum processor based on continuous variables states of light. Here, we investigate the performance of hot electron bolometers (HEBs) fabricated on top of a silicon-on-insulator (SOI) photonic circuit showing responsivities up to 8600 V/W and a record noise equivalent temperature of 1.1 dB above the quantum limit. Thanks to a detailed analysis of the noise sources of the waveguide integrated HEB, we estimate 14.8 dBV clearance between the shot noise and electrical noise with just 1.1µW of local oscillator power. The full technology compatibility with superconducting nanowire single photon detectors (SNSPDs) opens the possibility of nonclassical state engineering and state tomography performed within the same platform, enabling a new class of optical quantum processors.

This letter demonstrates a novel prism-based optical-readout, which uses a single prism to detect the incoming TM polarized wave just below the critical angle. The method is used with a 35- $\mu \text{m}$ -pixel pitch MEMS thermal sensor, whose inclination angle changes with the absorbed infrared (IR) radiation that results in an increase in the reflectivity at the prism’s glass–air interface. We compared this approach with the conventional knife-edge method. Noise equivalent temperature difference for a single sensor was measured as 200 mK for knife-edge method, and 154 mK for the proposed critical angle approach. Our approach shows a significant improvement for the sensitivity of the IR sensor. Both methods utilize an AC-coupled readout method for a single MEMS pixel using a photodetector, which responds only to changes in the scene. This method can be scaled to achieve smart pixel cameras for read sensor arrays with low-noise and high-dynamic range.

This paper reports a novel infrared focal plane array (FPA) using SiN x /SiO2/SiN x sandwiched structure as the supporting frames for bimaterial cantilever pixels. The device was fabricated by a bulk silicon process, where a trench backfill technique was employed to form the SiN x /SiO2/SiN x sandwiched frames. By replacing the silicon frame with SiN x /SiO2/SiN x sandwiched frame, the fill factor of the FPA is increased to 42%. Compared with other substrate-free FPAs with frames making of a thin layer of SiN x , the sandwiched frame provides more supporting strength for the cantilever pixels. Meanwhile, the reliability and the uniformity of the FPA were improved with a design of staggered arrangement of cantilever pixels. Thermal images of human bodies were captured successfully at room temperature. A complete analysis of device performance was also carried out both theoretically and experimentally, including thermomechanical sensitivity, noise equivalent temperature difference, and response time. [2015-0261]

This paper presents a low switching-loss Dicke radiometer for W-band passive imaging systems. The equivalent switching loss introduced by the passive single-pole-double-throw (SPDT) switch in the conventional radiometer is significantly reduced by the proposed single-pole-double-throw distributed amplifier (SPDT-DA), which leads to radical improvement on the receiver’s noise performance. The Dicke radiometer consisting of a SPDT-DA, a four-stage low noise amplifier (LNA) and a power detector is fully integrated in a 0.13- $\mu{\hbox {m}}$ SiGe BiCMOS chip. With the 0.93-dB equivalent switching loss at 91 GHz of the SPDT-DA, the total noise figure (NF) of 8.4 dB at 91 GHz is achieved by the SPDT-DA followed by the LNA. With a power consumption of 28.5 mW, the radiometer obtains an overall RF gain of 42 dB and a noise equivalent temperature difference (NETD) of 0.21 K with 30-ms integration time. The two-dimensional imaging experiment with object distance of 0.7 m is successfully carried out with the radiometer chip.

This paper presents a low-noise SiGe radiometer at 136 GHz developed in an IBM 90-nm SiGe BiCMOS technology. The radiometer consists of a three-stage cascode low-noise amplifier with a gain of 36 dB, and a differential output square-law detector, all on a single chip. The detector results in responsivity of 11 kV/W and a noise equivalent power (NEP) of ${\hbox{0.6 pW/Hz}}^{1/2}$ at D-band frequencies. The radiometer chip consumes 45 mW and results in a minimum NEP of ${\hbox{1.4 fW/Hz}}^{1/2}$ with a peak responsivity of 52 MV/W at 136 GHz. The single-chip radiometer is suitable for high-resolution imaging systems having a noise bandwidth $>{\hbox{10 GHz}}$ and a low $1/f$ corner frequency $( . For an integration time of 3.125 mS $(\tau=3.125~{\hbox{mS}})$ , the temperature resolution [noise equivalent temperature difference (NETD)] is determined to be 0.25 K using several different independent methods, and is the lowest NETD demonstrated in silicon technologies at D-band frequencies. This state-of-the-art performance is comparable to the best III–V imaging systems and proves that the advanced SiGe technology is a reliable option for imaging and radiometry applications.

Detecting low energy photons, such as photons in the long-wave infrared range, is a technically challenging proposition using naturally occurring materials. In order to address this challenge, we herein demonstrate a micro-bolometer featuring an integrated metamaterial absorber (MA), which takes advantage of the resonant absorption and frequency selective properties of the MA. Importantly, our micro-bolometer exhibits polarization insensitivity and high absorption due to a novel metal-insulator-metal (MIM) absorber design, operating at 8-12 µm wavelength. The metamaterial structures we report herein feature an interconnected design, optimized towards their application to micro-bolometer-based, long-wave infrared detection. The micro-bolometers were fabricated using a combination of conventional photolithography and electron beam lithography (EBL), the latter owing to the small feature sizes within the design. The absorption response was designed using the coupled mode theory (CMT) and the finite integration technique, with the fabricated devices characterized using Fourier-transform infrared spectroscopy (FTIR). The metamaterial-based micro-bolometer exhibits a responsivity of approximately 198 V/W over the 8-12 µm wavelength regime, detectivity of ∼ 0.6 × 109 Jones, thermal response time of ∼ 3.3 ms, and a noise equivalent temperature difference (NETD) of ∼33 mK under 1mA biasing current at room-temperature and atmosphere pressure. The ultimate detectivity and NETD are limited by Johnson noise and heat loss with thermal convection through air; however, further optimization could be achieved by reducing the thermal conductivity via vacuum packaging. Under vacuum conditions, the detectivity may be increased in excess of two-fold, to ∼ 1.5 × 109 Jones. Finally, an infrared image of a soldering iron was generated using a single-pixel imaging process, serving as proof-of-concept of this detection platform. The results presented in this work pave the road towards high-efficiency and frequency-selective detection in the long-wave infrared range through the integration of infrared MAs with micro-bolometers.

According to the requirement of high-definition surveillance of the status of space targets in low illuminance, a high SNR (Signal to Noise Ratio) uncooled long-wave infrared system is designed. Based on the detector of UL04371 with 640 × 480 array, the system scheme, acquisition system and real-time image processing algorithms are realized. On the basis of system implementation, the paper mainly focuses on how to reduce the noises from the aspect of hardware circuits and how to realize the real-time processing in the way of specified infrared image algorithms. Finally, the paper gives the test result which shows that the system has achieved a relatively good SNR characteristic with the average NETD (Noise Equivalent Temperature Difference) value of 220mK under the condition of the integration time of 64us and the radiation of 300K black body.

An uncooled VGA Infrared Focal Plane Array (IRFPA) based on microbolometers with a pixel pitch of 25 μm for thermal imaging applications is presented. The IRFPA has a 16-bit digital video data output at a frame rate of 30 Hz. Thousands of Analog to Digital Converters (ADCs) are located under the microbolometer array. One ADC consists of a Sigma-Delta-Modulator (SDM) of 2nd order and a decimation filter. It is multiplexed for a certain amount of microbolometers arranged in a so called "cluster". In the 1st stage of the SDM the microbolometer current is integrated time-continuously. The feedback is applied using a switchable current source. First measurements of Noise Equivalent Temperature Difference (NETD) as a key parameter for IRFPAs will be presented.

Accurate correction of atmospheric effects on data captured by an infrared (IR) camera is crucial for several applications such as vegetation monitoring, temperature monitoring, satellite images, hyperspectral imaging, numerical model simulations, surface properties characterization, and IR measurement interpretation. Atmospheric effects depend on the temporal changes, i. e., year, season, day, hour, etc., and on the geometry between the camera and the measured scene, i. e., line of sight. The orientation and the optical depth of the camera significantly affect the variation of the geometry across the pixels. In this paper, we propose a method to estimate the range and zenith angle of each pixel using only the Global Positioning System (GPS) coordinates of the camera and a point of interest in the scene. The estimated geometry and measured meteorological data are used to obtain the spectral atmospheric transmittance and path radiance. Furthermore, we propose an atmospheric effects removal, i. e., atmospheric correction, method that considers the spectral characteristics of the detector, lens, and filter. The proposed atmospheric correction process is analyzed in detail with the simultaneous measurements of two IR cameras. In this process, an enhanced temperature calibration method is developed and it is shown that the temperature accuracy for the dynamic range of the IR camera is very close to the noise equivalent temperature difference (NETD) value of the camera.

This paper presents the design, fabrication, and performance of a $256 \times 256$ multiband infrared (IR) focal plane array (FPA) using microbimaterial cantilever as the sensitive pixel. Different from traditional uncooled IR FPA that works only at long wavelength IR, the working bandwidth of the presented FPA is extended to full band IR, covering the three IR atmospheric windows of 1– $2.5~\mu $ m, 3– $5~\mu $ m and 8–14 $\mu $ m simultaneously. The multiband performance is attributed to the elaborately designed multiband absorber consisting of a stacked layer of silicon nitride, chromium nanofilm, and gold mirror. The absorbing mechanism of the stacked layer is discussed in detail and testified by experimental results. Images of short-wavelength, middle-wavelength, and long-wavelength IR were captured successfully with the single FPA. The measured sensitivity and noise equivalent temperature difference of the FPA are $0.18~\mu $ m/K and 194.7 mK, respectively. [2014-0090]

For reasons associated with size, weight, power consumption, and cost, the future of infrared systems for all spectral bands is being driven towards megapixel formats operating under diffraction- and background-limited conditions with ever-smaller pixel pitches and ever-higher operating temperatures. The performance requirements of such systems with regard to both optical and detector limitations are examined for the materials technologies and device architectures that are in vogue today. At elevated operating temperatures, available noise equivalent temperature difference values for diffraction-limited operation are found to be strongly dependent on the available pixel pitch, optimizing at values ∼λ/4, where λ is the operating wavelength. The possibility for extending the operation of mid- and long-wavelength focal plane arrays to room temperature with diffraction- and background-limited performance is discussed, together with the potential issues that must be addressed in order to achieve this ultimate goal.

In this study, we analyzed and showed the enhanced thermal resolution of a lock-in infraredthermography system by employing a blackbody system and micro-register sample. The noise level or thermalresolution of an infrared camera system is usually expressed by a noise equivalent temperature difference (NETD),which is the mean square of the deviation of the different values measured for one pixel from its mean valuesobtained in successive measurements. However, for lock-in thermography, a more convenient quantity in thephase-independent temperature modulation amplitude can be acquired. On the basis of results, it was observed thatthe NETD or thermal resolution of the lock-in thermography system was significantly enhanced, which we considerto have been caused by the averaging and filtering effects of the lock-in technique. Keywords: Lock-in Thermography, Noise Equivalent Temperature Difference, Infrared Microscope, Thermal Resolution[Received: September 23, 2014, Revised: October 20, 2014, Accepted: October 29, 2014] *한국기초과학지원연구원첨단장비개발사업단, ** IT , Corresponding Author: Center for Analytical한국과학기술원스마트 융합시스템연구단 ✝Instrumentation Development, Korea Basic Science Institute, 169-148 Gwahak-ro, Yuseong-gu, Daejeon 305-806, Korea(E-mail: ksc@kbsi.re.kr)

Recently, thermography camera have been using for body-temperature monitoring. We report on fabrication of prototype thermography camera using the chalcogenide-glass lens and the camera test by analysis of thermal image. In this work, it was found out that thermography camera discerned body-temperature between 20 and with noise equivalent temperature difference(NETD) of 87.7mK. It is confirmed that thermography camera using the chalcogenide-glass lens is applicable to the body-temperature monitoring system.

A MEMS based novel THz detector structure is designed and realized by micro fabrication. The detector is then characterized to extract its mechanical performance. Operating in 1-5 THz band, the detector has a pixel size of 200μm × 200μm. Bimaterial suspension legs consist of Parylene-C and titanium, the pair of which provides a high mismatch in coefficients of thermal expansion. The pixel is a suspended Parylene-C structure having a 200 nm-thick titanium metallization. Operation principle relies on conversion of absorbed THz radiation into heat energy on the pixel. This increases the temperature of the free-standing microstructure that is thermally isolated from the substrate. The increase in temperature induces mechanical deflection due to bimaterial springs. The detector is designed to deliver a noise equivalent temperature difference (NETD) less than 500 mK and a refresh rate of 30Hz.

Fraunhofer IMS develops and fabricates far-infrared focal plane arrays (IRFPA) using microbolometers with a pixel pitch of 17μm technology realized on top of a 0.35 μm CMOS readout integrated circuit (ROIC). The microbolometers are encapsulated by a Chip-Scale-Package (CSP) to ensure a high quality vacuum level. The CSP is realized by placing an infrared transparent lid above a solder frame surrounding the microbolometer array. To concept a wafer-level test it is very challenging to implement highly accurate electrical stimuli and a far infrared radiation source (black body) while affecting the wafer-prober handling by a non-flat wafer surface, due to the infrared transparent lids of the CSP. Accordingly, wafer-level test has been developed based on a PC which controls, by using a test program, the wafer handling of a prober, the electrical stimuli of a test hardware, and the far-infrared radiation such as the optical stimuli. Thus, the most important electro-optical parameters of IRFPAs will be measured at wafer-level: Noise Equivalent Temperature Difference (NETD), responsivity, and the percentage of the defective pixels.

We analyze the performance limit of uncooled thermo-mechanical infra-red imagers with optical readout. We have shown that for large enough frame format thermal noise of load resistance of output electronic cascade of optical readout system determines mainly the noise equivalent temperature difference, NETD, of such systems. For middle frame format they can successfully compete with micro-bolometer infra-red detectors. Higher power low noise light source for optical readout system and more exquisite phase detection enable them to be competitive in large frame format too.

The Visible Infrared Imaging Radiometer Suite (VIIRS) sensor aboard the Suomi National Polar-orbiting Partnership spacecraft has successfully operated since its launch in October 2011. The VIIRS collects data in 22 spectral bands that are calibrated by a set of onboard calibrators (OBC). In addition, lunar observations are made to independently track VIIRS long-term calibration stability for the reflective solar bands (RSB). This paper provides an overview of VIIRS OBC functions as well as its on-orbit operation and calibration activities. It also describes sensor calibration methodologies and demonstrates VIIRS on-orbit performance from launch to present. Results reported in this paper include on-orbit changes in sensor spectral band responses, detector noise characterization, and key calibration parameters. Issues identified and their potential impacts on sensor calibration are also discussed. Since launch, the VIIRS instrument nominal operation temperature has been stable to within ±1.0 K. The cold focal plane temperatures have been well controlled, with variations of less than 20 mK over a period of 1.5 years. In general, changes in thermal emissive bands (TEB) detector responses have been less than 0.5%. Despite large response degradation in several near-infrared and short-wave infrared bands and large SD degradation at short visible wavelengths, the VIIRS sensor and OBC overall performance has been excellent postlaunch. The degradation caused by the telescope mirror coating contamination has been modeled and its impact addressed through the use of modulated relative spectral response in the improved calibration and the current sensor data record data production. Based on current instrument characteristics and performance, it is expected that the VIIRS calibration will continue to meet its design requirements, including RSB detector signal to noise ratio and TEB detector noise equivalent temperature difference, throughout its 7 year design lifetime.

We present an overview of the design and development of the POLARBEAR-2 experiment. The POLARBEAR-2 experiment is a cosmic microwave background polarimetry experiment, which aims to characterize the small angular scale B-mode signal due to gravitational lensing and search for the large angular scale B-mode signal from inflationary gravitational waves. The experiment will have a 365 mm diameter multi-chroic focal plane filled with 7,588 polarization sensitive antenna-coupled Transition Edge Sensor bolometers and will observe at 95 and 150 GHz. The focal plane is cooled to 250 mK. The bolometers will be read-out by SQUIDs with $$32\times $$ frequency domain multiplexing. The experiment will utilize high purity alumina lenses and thermal filters to achieve the required high optical throughput. A continuously rotating, cooled half-wave plate will be used to give stringent control over systematic errors. The experiment is designed to achieve a noise equivalent temperature of 5.7 $$\mu $$ K $$\sqrt{s}$$ , and this allows us to constrain the signal from the inflationary primordial gravitational corresponding to a tensor-to-scalar ratio of $$r = 0.01$$ ( $$2\sigma $$ ). POLARBEAR-2 will also be able to put a constraint on the sum of neutrino masses to 90 meV ( $$1\sigma $$ ) with POLARBEAR-2 data alone and 65 meV ( $$1\sigma $$ ) when combined with the Planck satellite. We plan to start observations in 2014 in the Atacama Desert in Chile.

Due to continuous improvement of traditional liquid-phase epitaxy n-on-p technology, excellent mid-wavelength infrared HgCdTe (MCT) detectors with 1280 × 1024 pixels and 15 μm pitch size have been produced at AIM. At an operating temperature (TOP) of 80 K, a noise equivalent temperature difference (NETD) of 17.8 mK and an operability of 99.96% have been obtained. At TOP = 130 K, the operability remains high at 99.58%. On the basis of these results, the sensitivity of this detector design has been extended into the long-wavelength infrared (LWIR) region, obtaining a detector with an NETD of 30.4 mK and an operability of 99.81% at TOP = 80 K. In parallel, the growing maturity of molecular-beam epitaxy (MBE) growth of MCT on GaAs substrates has led to an improvement of the performance of the MWIR 640 × 512, 15-μm-pitch detector from an operability of 99.30% in 2011 to 99.83% recently.

In this paper, the evaluation method for the responsivity and noise characteristics of an infrared thermal imaging camera was presented. Signal transfer function and noise equivalent temperature difference of the infrared thermal imaging camera were obtained by using a differential mode blackbody that is able to control the temperature difference T between an infrared target and its background. And we verified the suitability of our evaluation method through comparison between the found noise equivalent temperature difference and the specification of the camera. In addition, the difference of 0.01 K of the two noise equivalent temperature differences calculated from with and without nonuniformity correction suggests that the nonuniformity correction is essential process for the evaluation of the infrared thermal imaging camera.

We report a significant step in the design, fabrication, and performance evaluation of a 240 × 240 microelectromechanical system uncooled infrared (IR) focal plane array (FPA) with 42-μm pitch pixels. An improved analytical model has been developed to optimize the design. The optimal key parameters have been verified through experiments, including thermal transmission efficiency, thermomechanical sensitivity, thermal sensitivity, and response time. Compared with our previous work, the number of the fabricated FPA's pixels is increased by 125% and the corresponding pixel's area is decreased by 51%. Furthermore, our FPA has a good sensitivity with a noise equivalent temperature difference of about 373 mK, thus providing an extension of state-of-the-art IR FPA and practical information for future applications.

We investigate use of nanomechanical torsional resonators for frequency-shift-based infrared (IR) thermal sensing. Nanoscale torsion rods, ~1 μm long and 50–100 nm in diameter, provide both extraordinary thermal isolation and excellent angular displacement and torque sensitivities, of order ~10^(–7) rad·Hz^(–1/2) and 10^(–22) (N·m) Hz^(–1/2), respectively. Furthermore, these nanorods act as linear torsional springs, yielding a maximum angular displacement of 3.6° and a dynamic range of over 100 dB; this exceeds the performance of flexural modes by as much as 5 orders of magnitude. These attributes lead to superior noise performance for torsional-mode sensing. We demonstrate the operational principles of torsional-mode IR detection, attaining an uncooled noise equivalent temperature difference (NETD) of 390 mK. By modeling the fundamental noise processes, we project that further reduction of device size can significantly improve thermal responsivity; a room-temperature NETD below 10 mK appears feasible.

In this paper, a sensitivity analysis and procedure development for volcanic-plume sulfur dioxide and ash retrievals using ground thermal infrared camera have been carried out. The semiconductor device camera, considered as a reference, has a spectral range of 8-14 ìm with noise equivalent temperature difference that is better than 100 mK at 300 K. The camera will be used to monitor and assess the hazards of Mt. Etna volcano to mitigate the risk and impact of volcanic eruptions on the civil society and transports. A minimum number of filters have been selected for sulfur dioxide (SO 2) and volcanic ash retrievals. The sensitivity study has been carried out to determine the SO 2 and volcanic ash minimum concentration detectable by the system varying the camera geometry and the atmospheric profiles. Results show a meaningful sensitivity increase considering high instrument altitudes and low camera-elevation angles. For all geometry configurations and monthly profiles, the sensitivity limit varies between 0.5 and 2 g.m -2 for SO 2 columnar abundance and between 0.02 and 1 for ash optical depth. Two procedures to detect SO 2 and ash, based on the least square fit method and on the brightness temperature difference (BTD) algorithm, respectively, have also been proposed. Results show that high concentration of atmospheric water vapor columnar content significantly reduces the ash-plume effect on the BTD. A water vapor-correction procedure introduced improves the ash retrievals and the cloud discrimination in every season, considering all the camera geometries. © 2009 IEEE.

We have developed a passive 350 GHz (850 {\mu}m) video-camera to demonstrate lumped element kinetic inductance detectors (LEKIDs) -- designed originally for far-infrared astronomy -- as an option for general purpose terrestrial terahertz imaging applications. The camera currently operates at a quasi-video frame rate of 2 Hz with a noise equivalent temperature difference per frame of $\sim$0.1 K, which is close to the background limit. The 152 element superconducting LEKID array is fabricated from a simple 40 nm aluminum film on a silicon dielectric substrate and is read out through a single microwave feedline with a cryogenic low noise amplifier and room temperature frequency domain multiplexing electronics.

Driven by the need for more efficient and cost-effective production of infrared (IR) detectors as well as the demands for novel (third-generation) device concepts, a large amount of effort has been spent on the development of molecular beam epitaxy (MBE) for fabrication of high-quality HgCdTe (MCT) layers on both CdZnTe and alternative substrates. The bulk of recent publications focuses on Si as an alternative substrate material. The intent of this paper is to highlight the potential benefit of using GaAs as an alternative substrate material by presenting MCT material grown by MBE on GaAs at AIM. Mid-wave IR MCT/GaAs material has been processed by AIM’s standard planar n-on-p technique. Focal-plane arrays with 640 × 512 pixels and a 15 μm pitch design show low and homogeneous noise equivalent temperature difference of 18.3 ± 2.0 mK at 99.31% operability. To analyze the feasibility of MBE growth of long-wave IR MCT on GaAs, a layer with 8.8 μm cutoff at 80 K has been fabricated and processed into 640 × 512 pixels, 15-μm-pitch arrays. Initial current–voltage characterization yields promising results and illustrates the potential of MBE growth for LWIR MCT detector production.

Electrical and radiometric characterization results of a high-operability1024 × 1024 long wavelength infrared type-II superlattice focal plane array are described. It demonstrates excellent quantum efficiency operability of 95.8% and 97.4% at operating temperatures of 81 K and 68 K, respectively. The external quantum efficiency is 81% without any antireflective coating. The dynamic range is 37 dB at 81 K and increases to 39 dB at 68 K operating temperature. The focal plane array has noise equivalent temperature difference as low as 27 mK and 19 mK at operating temperatures of 81 K and 68 K, respectively, using f/2 optics and an integration time of 0.13 ms.

著者人数: 14名, Accepted: 2011-06-09, 資料番号: SA1003050000

Our previous research has reported on the development of the first generation of quantum dots-in-a-well (DWELL) focal plane arrays (FPAs), which are based on InAs quantum dots (QDs) embedded in an InGaAs well having GaAs barriers, which have demonstrated spectral tunability via an externally applied bias voltage. More recently, technologies in DWELL devices have been further advanced by embedding InAs QDs in InGaAs and GaAs double wells with AlGaAs barriers, leading to a less strained InAs/InGaAs/GaAs/AlGaAs heterostructure. These lower strain quantum dots-in-a-double-well devices exhibit lower dark current than the previous generation DWELL devices while still demonstrating spectral tunability. This paper compares two different configurations of double DWELL (DDWELL) FPAs to a previous generation DWELL detector and to a commercially available quantum well infrared photodetector (QWIP). All four devices are 320 × 256 pixel FPAs that have been fabricated and hybridized with an Indigo 9705 read-out integrated circuit. Radiometric characterization, average array responsivity, array uniformity and measured noise equivalent temperature difference for all four devices is computed and compared at 60 K. Overall, the DDWELL devices had lower noise equivalent temperature difference and higher uniformity than the first-generation DWELL devices, although the commercially available QWIP has demonstrated the best performance.