DRS history in microbolometer and uncooled focal plane array (UFPAA) development mimics that of the entire industry. The history extends over fifteen years as array pitches moved ever-smaller from 51uum to 25um to 17um, and now something smaller than 17uum. The uncooled microbolometer makers have transitioned through smaller pitches about every six years. This has been done while maintaining a noise equivalent temperature difference (NNETD) performance of 20-50mK, and maintaining a thermal time constant (TTTC) of 10-20mmSec. Once a newer pitch is developed to a performance level matching the previous pitch, development on the next smaller pitch is already underway. In this manner, the industry has progressed through smaller pitches without a fundamental performance improvement when measured in NNETD or in TTTC, or more specifically in NNETD*TTC product. Hence, a more-encompassing metric for tracking performance through time would involve the NNETD, the TTCC, and some indicator of bolometer size. Ann NETD*TTC**Area metric, as the appropriate metric for including bolometer size, will be proposed, theoretically justified, and discussed here. A rank-ordering of bolometers which have been published through 22013 is also presented in three charts, one for NETTD, one for NEETD*TTC, and lastly one for NETD*TTC**Area.

Identification of potential threats in low-light conditions through imaging is commonly achieved through closed-circuit television (CCTV) and surveillance cameras by combining the extended near infrared (NIR) response (800-10000nm wavelengths) of the imaging sensor with NIR LED or laser illuminators. Consequently, camera systems typically used for purposes of long-range observation often require high-power lasers in order to generate sufficient photons on targets to acquire detailed images at night. While these systems may adequately identify targets at long-range, the NIR illumination needed to achieve such functionality can easily be detected and therefore may not be suitable for covert applications. In order to reduce dependency on supplemental illumination in low-light conditions, the frame rate of the imaging sensors may be reduced to increase the photon integration time and thus improve the signal to noise ratio of the image. However, this may hinder the camera’s ability to image moving objects with high fidelity. In order to address these particular drawbacks, PHOTONIS has developed a CMOS imaging sensor (CIS) with a pixel architecture and geometry designed specifically to overcome these issues in low-light level imaging. By combining this CIS with field programmable gate array (FPGA)-based image processing electronics, PHOTONIS has achieved low-read noise imaging with enhanced signal-to-noise ratio at quarter moon illumination, all at standard video frame rates. The performance of this CIS is discussed herein and compared to other commercially available CMOS and CCD for long-range observation applications.

We have been researching and developing a CMOS image sensor that has 2.8 μm x 2.8 μm pixel, 33-Mpixel resolution (7680 horizontal pixels x 4320 vertical pixels), 120-fps frame rate, and 12-bit analog-to-digital converter for “8K Super Hi-Vision.” In order to improve its sensitivity, we used a 0.11-μm nanofabricated process and attempted to increase the conversion gain from an electron charge to a voltage in the pixel. The prototyped image sensor shows a sensitivity of 2.4 V/lx•s, which is 1.6 times higher than that of a conventional image sensor. This image sensor also realized the input-referred random noise as low as 2.1 e^-_rms.

Banpil Photonics (Banpil) has developed a low-cost high-performance multispectral camera system for Visible to Short- Wave Infrared (VIS-SWIR) imaging for the most demanding high-sensitivity and high-speed military, commercial and industrial applications. The 640x512 pixel InGaAs uncooled camera system is designed to provide a compact, smallform factor to within a cubic inch, high sensitivity needing less than 100 electrons, high dynamic range exceeding 190 dB, high-frame rates greater than 1000 frames per second (FPS) at full resolution, and low power consumption below 1W. This is practically all the feature benefits highly desirable in military imaging applications to expand deployment to every warfighter, while also maintaining a low-cost structure demanded for scaling into commercial markets. This paper describes Banpil’s development of the camera system including the features of the image sensor with an innovation integrating advanced digital electronics functionality, which has made the confluence of high-performance capabilities on the same imaging platform practical at low cost. It discusses the strategies employed including innovations of the key components (e.g. focal plane array (FPA) and Read-Out Integrated Circuitry (ROIC)) within our control while maintaining a fabless model, and strategic collaboration with partners to attain additional cost reductions on optics, electronics, and packaging. We highlight the challenges and potential opportunities for further cost reductions to achieve a goal of a sub-$1000 uncooled high-performance camera system. Finally, a brief overview of emerging military, commercial and industrial applications that will benefit from this high performance imaging system and their forecast cost structure is presented.

The use of 3D integration technology in focal plane array imaging devices has been shown to increase imaging capability while simultaneously decreasing device area and power consumption, as compared to analogous 2D designs. A key enabling technology for 3D integration is the use of high density metal-metal bonding to form pixel-level interconnects between device layers. In this paper, we review recent progress in high density, sub-10 μm pitch interconnect bonding for 3D integration of imaging systems. Specifically, we will present results from successful demonstrations of the use of Cu microbumps for the interconnection of 5 μm pitch 640×512 and 1280×1024 arrays. Operability of the arrays of bonded interconnects in two-layer silicon die stacks was greater than 99.99% with good electrical isolation between bonds.

InAsSb material with a cutoff wavelength in the 5 μm range has been grown on GaAs substrates. The MWIR InAsSb detector arrays were fabricated and hybridized to fanouts and ROICs to permit measurement of the electrical and optical properties of detectors. Detector arrays were fabricated in a 1024 x 1024 format on an 18 μm pitch. A fanout was utilized to directly acquire data from a set of selected detectors without an intervening read out integrating circuit (ROIC). Variable temperature Jdark vs Vd measurements have been made with the dark current density ~ 10^-5 A/cm² at 150 K. The external QE measured using a narrow band filter centered at ~ 4 μm had values in the 65 - 70 % range. Since the detectors were illuminated through a GaAs substrate which has a reflectance of 29%, the internal QE is greater than 90 %. A 1024 x 1024 ROIC on an 18 μm pitch was also designed and fabricated to interface with the barrier detectors. The ROIC operates at 30 Hz frame rate and has a well capacity of 20.7 M electrons. QE at 150 K for a 1024 x 1024 detector array hybridized to a ROIC had a median D* at 150 K under a flux of 1.07 x 10¹⁵ ph/(cm²/s was 1.2 x 10¹¹ cm Hz^1/2 /W. The NEdT was 44 mK and imagery was obtained at 150 K using an f/2.3 MWIR lens.

Research and development of robust compact hyperspectral imagers that can acquire both spectral and spatial features from a scene of interest is of utmost importance for standoff detection of targets as well as chemical and biological agents and backgrounds. Hyperspectral imagers can acquire images with a large number of narrow spectral bands and take advantage of the characteristic spectral signatures of different materials making up the scene. At the Army Research Laboratory (ARL), we are developing hyperspectral imagers based on acousto-optic tunable filters (AOTFs) that can provide adaptive no-moving-parts imagers from the ultraviolet (UV) to the long wave infrared (LWIR) to acquire a two-dimensional spectral image and build up a two-dimensional image cube as a function of time instead of using traditional grating or prism based approach that requires relative motion between sensor and scene. Here, we will review the development of different imaging AOTFs operating from the UV to the LWIR based on a variety of birefringent materials and include the spectral imaging carried out with these filters including both with single and double piezoelectric transducers. We will also include the theoretical background needed to carry out the filter design and discuss development of mercurous halide crystals that can be used to develop AOTFs operating over a wide spectral region from the visible to the LWIR.

Imaging spectrometry can be utilized in the midwave infrared (MWIR) and long wave infrared (LWIR) bands to detect, identify and map complex chemical agents based on their rotational and vibrational emission spectra. Hyperspectral datasets are typically obtained using grating or Fourier transform spectrometers to separate the incoming light into spectral bands. At present, these spectrometers are large, cumbersome, slow and expensive, and their resolution is limited by bulky mechanical components such as mirrors and gratings. As such, low-cost, miniaturized imaging spectrometers are of great interest. Microfabrication of micro-electro-mechanicalsystems (MEMS)-based components opens the door for producing low-cost, reliable optical systems. We present here our work on developing a miniaturized IR imaging spectrometer by coupling a mercury cadmium telluride (HgCdTe)-based infrared focal plane array (FPA) with a MEMS-based Fabry-Perot filter (FPF). The two membranes are fabricated from silicon-oninsulator (SOI) wafers using bulk micromachining technology. The fixed membrane is a standard silicon membrane, fabricated using back etching processes. The movable membrane is implemented as an X-beam structure to improve mechanical stability. The geometries of the distributed Bragg reflector (DBR)-based tunable FPFs are modeled to achieve the desired spectral resolution and wavelength range. Additionally, acceptable fabrication tolerances are determined by modeling the spectral performance of the FPFs as a function of DBR surface roughness and membrane curvature. These fabrication non-idealities are then mitigated by developing an optimized DBR process flow yielding high-performance FPF cavities. Zinc Sulfide (ZnS) and Germanium (Ge) are chosen as the low and the high index materials, respectively, and are deposited using an electron beam process. Simulations are presented showing the impact of these changes and non-idealities in both a device and systems level.

We present the recent development of high performance compact THz sources based on intracavity nonlinear frequency mixing in mid-infrared quantum cascade lasers. Significant performance improvements of our THz sources in the spectral purity, frequency coverage as well as THz power are achieved by systematic optimizing the device's active region, waveguide, phase matching scheme, and chip bonding strategy. Room temperature single-mode operation in a wide THz spectral range of 1-4.6 THz is demonstrated from our Čerenkov phase-matched THz sources with dual-period DFB gratings. High THz power up to 215 μW at 3.5 THz is demonstrated via epi-down mounting of our THz device. The THz power is later scaled up to mW level by increased the mid-IR power and conversion efficiency. The rapid development renders this type of THz sources promising local oscillators for many astronomical and medical applications.

In imaging systems, whether visible or infrared, the pixel dimension plays a crucial role in determining critical system attributes such as size, weight, and Power (SWaP). Smaller pixels enhance the value proposition of the imager through reduced cost Focal Plane Arrays (FPAs) and/or added system functionality for a given spatial footprint. For systems that operate at temperatures in which FPA cold shield efficiency is relevant an additional benefit to performance is achieved with the faster optics mandated by use of small pixels. Ultimate pixel dimensions are limited by diffraction effects from the aperture and are in turn wavelength dependent. Limits to the reduction in pixel dimensions will be explored and related to the historical trends in system design with accompanying performance attributes. Key challenges in realizing ultimate pixel dimensions in focal plane array design will be discussed. Progress toward these limits at DRS will be reviewed for LWIR HgCdTe Focal Plane arrays fabricated with 5 micron pixel dimensions. Possible system implications tied to the success of these shrinking pixel FPAs will be postulated.

Infrared Focal Plane Arrays have been developed with reductions in pixel size below the Nyquist limit imposed by the optical systems Point Spread Function (PSF). These smaller sub diffraction limited pixels allows spatial oversampling of the image. We show that oversampling the PSF allows improved fidelity in imaging, resulting in sensitivity improvements due to pixel correlation, reduced false alarm rates, improved detection ranges, and an improved ability to track closely spaced objects.

As the technologies in focal plane array (FPA) progresses, the industry is pushing for smaller pixel size and spacing between the pixels. The reduction in pixel size and spacing will increase both the resolution and fill factor which reduces the cost and increases the performance. However, as the density of the array elements increases, the crosstalk between the nearest neighboring pixels become a significant issue. Here we examine the case for a planer FPA with epitaxially grown NIN⁺ structure and the planer junctions are formed by diffusing P-type dopant into the N doped layer. We first examine the possible spacing by considering the lateral depletion region width to set the upper boundary for the spacing. The depletion region width is calculated by solving Poisson’s equation for Gaussian doping profile and the isolation of adjacent pixel is dependent on the formation of the back to back diodes to block the current flowing towards the device. Therefore overlap of the depletion regions indicates shorting and sets the minimum possible spacing for this structure. The electrical and optical crosstalks are modeled by using a DC resistive model to gauge the effect of current flow as the spacing reduces. Series of device arrays with various device pitches and device sizes ranging from 5 μm to 10 μm with device pitch from 5.5 μm to 15 μm are fabricated and tested under both dark and illumination conditions for their electrical performances including the crosstalk. The simulated and measured results will be presented.

Over the past decade, the development of infrared focal plane arrays (FPAs) has seen two trends: decreasing of the pixel size and increasing of signal-processing capability at the device level. Enabling more capability within smaller pixels can be achieved through the use of advanced wafer-level processes for the integration of FPAs with silicon (Si) readout integrated circuits (ROICs). In this paper, we review the development of these wafer-level integration technologies, highlighting approaches in which the infrared sensor is integrated with three-dimensional ROIC stacks composed of multiple layers of Si circuitry interconnected using metal-filled through-silicon vias.

With reductions in microbolometer size and cost, long-wave infrared (LWIR) systems are increasingly being developed for platforms with challenging size, weight, power, and cost (SWAP-C) constraints, such as helmet-mounted systems and unmanned vehicles. Past optimization of imaging systems toward the simultaneous objectives of improved stand-off detection and low size, weight, and power required an iterative, multi-disciplinary design process. Here we demonstrate the direct optimization of the full LWIR system model including the optics, sensor, signal processing, and display degrees of freedom with system level metrics including SWAP-C and detection range. The end result is a system with superior size and weight for a given detection range.

Optical sensing technology is critical for optical communication, defense and security applications. Advances in optoelectronics materials in the UV, Visible and Infrared, using nanostructures, and use of novel materials such as CNT and Graphene have opened doors for new approaches to apply device design methodology that are expected to offer enhanced performance and low cost optical sensors in a wide range of applications. This paper is intended to review recent advancements and present different device architectures and analysis. The chapter will briefly introduce the basics of UV and Infrared detection physics and various wave bands of interest and their characteristics [1, 2] We will cover the UV band (200-400 nm) and address some of the recent advances in nanostructures growth and characterization using ZnO/MgZnO based technologies and their applications. Recent advancements in design and development of CNT and Graphene based detection technologies have shown promise for optical sensor applications. We will present theoretical and experimental results on these device and their potential applications in various bands of interest.

The Lambert W function is applied via Maple to analyze the operation of the modern digital camera sensors. The Lambert W function had been applied previously to understand the functioning of diodes and solar cells. The parallelism between the physics of solar cells and digital camera sensors will be exploited. Digital camera sensors use p-n photodiodes and such photodiodes can be studied using the Lambert W function. At general, the bulk transformation of light into photocurrent is described by an equivalent circuit which determines a dynamical equation to be solved using the Lambert W function. Specifically, in a camera senor, the precise measurement of light intensity by filtering through color filters is able to create a measurable photocurrent that is proportional to image point intensity; and such photocurrent is given in terms of the Lambert W function. It is claimed that the drift between neighboring photocells at long wavelengths affects the ability to resolve an image and such drift can be represented effectively using the Lambert W function. Also is conjectured that the recombination of charge carries in the digital sensors is connected to the notion of “noise” in photography and such “noise” could be described by certain combinations of Lambert W functions. Finally, it is suggested that the notion of bias, and varying the width of the depletion zone, has a relationship to the ISO “sped· of the camera sensor; and such relationship could be described using Lambert W functions.

The purpose of this paper is to demonstrate the implementation of a new kind of image filter, in which the equations of the Ornstein-Uhlenbeck process are used in image processing in order to detect the edges of computerized images taken with magnetic resonance imaging (MRI) scanners, as a generalization of the standard Gaussian filter. This new filter will be called Ornstein-Uhlenbeck filter (OUF). One of the results obtained after applying the filter to the image, with the variation of the parameter σ is an effective differentiation of the various organs that are next to each other in each one of the resulting images. In addition, the edges of the internal body parts and organs are highlighted efficiently and differentiated from their surroundings.

Strict process control, combined with proprietary process enhancements have enabled the production of large-scale single-crystal sapphire that demonstrates crystalline quality in excess of what has previously been possible. Extremely low defect densities, narrow rocking-curves, and very low stress gradients in the material are demonstrated through various X-ray diffraction techniques.

An innovative heterojunction photodiode structure in HgCdTe-on-Si long-wavelength (LW) infrared focal plane array (IRFPA) detector is investigated in this paper. The quantum efficiency and the photoresponse of devices have been numerically simulated, using Crosslight Technology Computer Aided Design (TCAD) software. Simulation results indicate that in contrast to the p⁺-on-n homojunction photodiode, the heterojunction photodiode effectively suppresses the crosstalk between adjacent pixels and interface recombination between HgCdTe active region and buffer layer on Si substrate. And in the range of the LW-band, the quantum efficiency of the heterojunction photodiode increases by 35.5%. Furthermore, the heterojunction photodiode acquires the narrow-band response spectrum desired in the application of the LW IRFPA detectors as the p⁺-on-n homojunction photodiode with the optical filter. Finally, the smaller bulk resistance of its heavily doped N-type layer ensures the uniformity of the pixel series resistance in the large format IRFPAs.

Due to the absorptive and scattering nature of water, the characteristic of underwater image is different with it in the air. Underwater image is characterized by their poor visibility and noise. Getting clear original image and image processing are two important problems to be solved in underwater clear vision area. In this paper a new approach technology is presented to solve these problems. Firstly, an inhomogeneous illumination method is developed to get the clear original image. Normal illumination image system and inhomogeneous illumination image system are used to capture the image in same distance. The result shows that the contrast and definition of processed image is get great improvement by inhomogeneous illumination method. Secondly, based on the theory of photon transmitted in the water and the particularity of underwater target detecting, the characters of laser scattering on underwater target surface and spatial and temporal characters of oceanic optical channel have been studied. Based on the Monte Carlo simulation, we studied how the parameters of water quality and other systemic parameters affect the light transmitting through water at spatial and temporal region and provided the theoretical sustentation of enhancing the SNR and operational distance.

Noise is a primary characteristic of an infrared focal plane array (FPA) that contributes to detection performance at low light level. In a capacitive-feedback trans-impedance amplifier (CTIA)-based readout integrated circuit (ROIC), reset noise can be removed by correlated double sampling (CDS). There is an exotic experimental phenomenon that FPA noise will increase greatly if the first sampling time of CDS is less than a threshold value. A noise model at FPA interface is presented in this paper which explains that this new kind of noise originates from incompletely settling of CTIA preamplifier. As this noise is performed in time domains, we use transient noise simulation technique to describe the dependence of this noise on detector pixel capacitance, integration capacitor, and some other design parameters. Based on the theoretical model analysis and simulation results, effective design method is obtained to reduce this kind of noise.

In_xGa_1-xAs ternary compound is suitable for detector applications in the shortwave infrared (1-3 μm) band. In this paper, we reported on mesa type and planar type extended wavelength InGaAs detector arrays. The photo response performances of these detector arrays were investigated. The blackbody responsivities (R_bb) of these detectors at different temperatures were measured, and the results showed that the Rbb of planar type arrays was higher than that of the conventionally passivated mesa type, but the mesa arrays fabricated by improved passivating technique has the highest responsivity. The reason of the R_bb difference between the arrays was analyzed, and it is found that the difference mostly comes from the minority carrier lifetime, which is related to the device structures and fabrication processes. With the optimized fabrication processes the mesa type arrays can obtain higher blackbody responsivity even more than the planar arrays.

A 2-chip color camera, named UNB Super-camera, is introduced in this paper. Its image qualities in different lighting conditions are compared with those of a 1-chip color camera and a 3-chip color camera. The 2-chip color camera contains a high resolution monochrome (panchromatic) sensor and a low resolution color sensor. The high resolution color images of the 2-chip color camera are produced through an image fusion technique: UNB pan-sharp, also named FuzeGo. This fusion technique has been widely used to produce high resolution color satellite images from a high resolution panchromatic image and low resolution multispectral (color) image for a decade. Now, the fusion technique is further extended to produce high resolution color still images and video images from a 2-chip color camera. The initial quality assessments of a research project proved that the light sensitivity, image resolution and color quality of the Super-camera (2-chip camera) is obviously better than those of the same generation 1-chip camera. It is also proven that the image quality of the Super-camera is much better than the same generation 3-chip camera when the light is low, such as in a normal room light condition or darker. However, the resolution of the Super-camera is the same as that of the 3- chip camera, these evaluation results suggest the potential of using 2-chip camera to replace 3-chip camera for capturing high quality color images, which is not only able to lower the cost of camera manufacture but also significantly improving the light sensitivity.

UNB Pan-sharp, also named FuzeGo, is an image fusion technique to produce high resolution color satellite images by fusing a high resolution panchromatic (monochrome) image and a low resolution multispectral (color) image. This is an effective solution that modern satellites have been using to capture high resolution color images at an ultra-high speed. Initial research on security camera systems shows that the UNB Pan-sharp technique can also be utilized to produce high resolution and high sensitive color video images for various imaging and monitoring applications. Based on UNB Pansharp technique, a video camera prototype system, called the UNB Super-camera system, was developed that captures high resolution panchromatic images and low resolution color images simultaneously, and produces real-time high resolution color video images on the fly. In a separate study, it was proved that UNB Super Camera outperforms conventional 1-chip and 3-chip color cameras in image quality, especially when the illumination is low such as in room lighting. In this research the influence of image compression on the quality of UNB Pan-sharped high resolution color images is evaluated, since image compression is widely used in still and video cameras to reduce data volume and speed up data transfer. The results demonstrate that UNB Pan-sharp can consistently produce high resolution color images that have the same detail as the input high resolution panchromatic image and the same color of the input low resolution color image, regardless the compression ratio and lighting condition. In addition, the high resolution color images produced by UNB Pan-sharp have higher sensitivity (signal to noise ratio) and better edge sharpness and color rendering than those of the same generation 1-chip color camera, regardless the compression ratio and lighting condition.

The need for touch based authentication is growing rapidly in smartphones and tablets. Historically, fingerprint has served at its fullest capacity in establishing the uniqueness of an individual’s identity. In this paper we present a novel design of capacitive in-cell TFT-LCDs that supports both fingerprint scan and touch sensing by extending the in-cell capacitive sensing scheme. We discuss a novel readout circuit design that drives the capacitive sensors for touch interactions in low resolution and for fingerprint scan at higher resolution. Furthermore, we propose to enhance the low resolution fingerprint data with image super resolution. Evaluation results show that with super resolution, the proposed touch-fingerprint in-cell TFT-LCD design can support fingerprint verification with sensor pitch of 0.15mm.

A planar-type InGaAs linear detector was designed and fabricated based on n-i-n⁺ type InP/In_0.53Ga_0.47As/InP epitaxial materials. The major process of the detector contains planar diffusion, surface passivation, metal contact and annealing. The I-V curves and the relative spectral response were measured at room temperature. The relative spectral response is in the range of 0.9 μm to 1.68 μm. The R₀A of the detector is about 2×10⁶ Ω•cm² and the dark current density is 5~10nA/cm² at -10mV bias voltage. The linear detectors were wire-bonded with readout integrated circuits (ROIC) to form focal plane array (FPA). The input stage of the ROIC is based on capacitive-feedback transimpedance amplifier (CTIA) with a capacitor (C_int) to be 0.1pF. However, the FPA signals are oscillating especially when close to the saturation. The ohmic contact on p-InP region plays an important role in the performance of detectors and FPAs. In this case, the series resistance to p-InP layer of each pixel is up to 1×10⁶Ω. The FPAs were simulated in case of InGaAs detectors with different series resistances. According to the simulation results, the bandwidth of CTIA is lowering along with Rs increasing, and the signals of the FPAs oscillate when the series resistances are beyond 4×10⁴Ω. The reason for the unstable oscillation of FPA is due to the series resistance of the detector which is too high enough. Then, the annealing process of the detectors was improved and the series resistances were lower than 1×10⁴Ω. The optimized InGaAs linear detectors were wire-bonded with the same ROIC. The oscillation of the signals disappears and the FPA shows good stability.

This paper presents a novel high-sensitivity and wide dynamic range complementary metal oxide semiconductor (CMOS) active pixel sensor (APS) with an overlapping control gate. The proposed APS has a high-sensitivity gate/bodytied (GBT) photodetector with an overlapping control gate that makes it possible to control the sensitivity of the proposed APS. The floating gate of the GBT photodetector is connected to the n-well and the overlapping control gate is placed on top of the floating gate for varying the sensitivity of the proposed APS. Dynamic range of the proposed APS is significantly increased due to the output voltage feedback structure. Maximum sensitivity of the proposed APS is 50 V/lux•s in the low illumination range and dynamic range is greater than 110 dB. The proposed sensor has been fabricated by using 2-poly 4-metal 0.35 μm standard CMOS process and its characteristics have been evaluated.