T. Sessler

640 × 512 17 μm microbolometer FPA and sensor development

RVS has made a significant breakthrough in the development of a 640 x 512 uncooled array with a unit cell size of 17 μm x 17 μm, and performance approaching that of the 25μm arrays. The successful development of this array is the first step in achieving mega-pixel formats. This FPA is designed to ultimately achieve performance of (<50mK, f/1, 30 Hz) with an 8 msec time constant. The SB-400 is a highly productized ROIC and is designed to achieve very good sensitivity (low NETD and low spatial noise) and good dynamic range. The improved performance is through bolometer structure improvements and an innovative ROIC design. It also has a simple and flexible electrical interface which allows external electronics to be small, lightweight, low-cost, and low-power. Almost all adjustments can be made through the serial interface; hence there is no need for external adjustable (DAC) circuitry. The improved power supply rejection helps maintain highly stable detector and strip resistor bias voltages which helps reduce spatial noise and image artifacts. The combination of reduced FPA pixel size and improved effective thermal sensitivity enhances weapon sight performance by providing smaller, lighter-weight sights via reduced optics size or increased range via enhanced pixel resolution without increasing mass or increased range via improved NETD (lower f/#) without increasing mass. We will also provide an update on the enhanced performance and yield producibility of our NVESD ManTech 640 x 480 25μm arrays. We will also show the improvement in our uncooled common architecture electronics in terms of reduced power and size for helmet and rifle mounted sensors and a variety of missile applications.

Large format short-wave infrared (SWIR) focal plane array (FPA) with extremely low noise and high dynamic range

Raytheon Vision Systems (RVS) has obtained the initial performance data on a 1280x1024 format short wave infrared (SWIR) sensor with a dark current of 1 nA/cm2 and low noise input circuit of five noise electrons (5 e-), which is 2× lower electronic read-out noise and 2× lower dark current than previous designs. A remarkable feature of the sensor is that a novel high dynamic range circuit is also designed into the 15 × 15 μm pixel unit cell, in a large format, high density 1280×1024 SWIR FPA. The integration of the conflicting design requirements of extremely low noise with high dynamic range allows recognition of low contrast targets, without saturation from bright sources within the same frame of information. This enables operation in urban environments at low levels of ambient illumination, and simultaneously with bright sources that saturate conventional sensors.

Performance improvements for VOx microbolometer FPAs

Raytheon is producing high-quality 320 x 240 microbolometer FPAs with 25 μm pitch pixels. The 320 x 240 FPAs have a sensitivity that is comparable to microbolometer FPAs with 50 μm pixels. Typical NETD values for these FPAs are <50mK with an f/1 aperture and operating at 30 Hz frame rates. Pixel operability is greater than 99.9% on most FPAs, and uncorrected responsivity nonuniformity is less than 4% (sigma/mean). These 25 μm microbolometer detectors also have a relatively fast thermal time constant of approximately 10 msec. These arrays have produced excellent image quality, and are currently fielded in a variety of demonstration systems. The pixel size reduction facilitates a significant FPA cost reduction since the number of die printed on a wafer can be increased, and also has enabled the development of a large-format 640 x 480 FPA array. Raytheon is producing these arrays with excellent sensitivity and typical NETD values of <50mK with an f/1 aperture and operating at 30 Hz frame rates. These arrays have excellent operability and image quality. Several dual FOV prototype 640 x 480 systems have been delivered under the LCMS and UAV programs. RVS has developed a flexible uncooled front end (UFE) electronics that will serve as the basis for the camera engine systems using 320 x 240 arrays. RVS has developed a 640 x 480 Common Uncooled Engine (CUE) which is intended for small pixel, high performance applications. The CUE is the ideal cornerstone for ground and airborne systems, multi-mode sensor, weapon sight or seeker architectures, and commercial surveillance.

Resolution and sensitivity improvements for VOx microbolometer FPAs

Raytheon Vision Systems (RVS) has achieved a significant technical breakthrough in uncooled FPAs by reducing the pixel size by a factor of two while maintaining state-of-the-art sensitivity. Raytheon is producing high-quality 320 x 240 microbolometer FPAs with 25 μm pitch pixels. The 320 x 240 FPAs have a sensitivity that is comparable to microbolometer FPAs with 50 μm pixels. The array average NETD value for these FPAs is about 30 mK with an f/1 aperture and operating at 30 Hz frame rates. Pixel operability is greater than 99% on most FPAs, and uncorrected responsivity nonuniformity is less than 4% (sigma/mean). These 25 μm microbolometer detectors also have a relatively fast thermal time constant of approximately 10 msec. This state-of-the-art performance has been achieved as a result of an advanced micro machining fabrication process, which allows maximization of both the thermal isolation and the optical fill-factor. These arrays have produced excellent image quality, and are currently fielded in demonstration systems. The reduction in pixel size offers several potential benefits for IR systems. For a given system resolution (IFOV) requirement, the 25 μm pxiels allow a factor of two reduction in both the focal length and aperture size of the sensor optics. These FPAs are applicable to wide-field-of-view, long-range surveillance and targeting missions. The pixel size reduction facilitates a significant FPA cost reduction since the number of die printed on a wafer can be increased, and also has enabled the development of a large-format 640 x 480 FPA array. Raytheon is producing these arrays with very good sensitivity. These arrays have excellent operability and image quality. Several dual FOV prototype systems have been delivered under the LCMS and UAV programs, and are under evaluation at NVESD. Raytheon Vision Systems (RVS) has developed a flexible uncooled front end (UFE) electronics that will serve as the basis for camera engine systems using 320 x 240 and 640 x 480 FPAs. The focus has been to develop architecture suitable for a wide variety of systems from low cost modest performance to high performance military applications. This product has been designed with military environmental and shock and vibration conditions in mind. Intended for small pxiel, high performance applications, the UFE is the ideal cornerstone for ground and airborne UAV, multi-mode sneosr, weapon sight or seeker architectures.

High sensitivity 640 × 512 (20 μm pitch) microbolometer FPAs

RVS has made a significant breakthrough in the development of a 640 × 512 array with a unit cell size of 20μm × 20 μm and performance equivalent to that of the 25μm arrays. The successful development of this array is the first step in achieving mega-pixel formats. This FPA is designed to ultimately achieve performance near the temperature fluctuation limited NETD (<20mK, f/1, 30 Hz). The SB-300 is a highly productized readout and is designed to achieve very good sensitivity (low NETD and low spatial noise) and good dynamic range. The improved performance is through bolometer structure improvements and an innovative ROIC design. It also has a simple and flexible electrical interface which allows external electronics to be small, light, low-cost, and low-power. Almost all adjustments can be made through the serial interface; hence there is no need for external adjustable (DAC) circuitry. The improved power supply rejection helps maintain highly stable detector and strip resistor bias voltages which helps reduce spatial noise and image artifacts. We will show updated performance and imagery on these arrays, which is currently being measured at <30mK, f/1,555 30 Hz. Pixel operability is greater than 99.5% on most FPAs, where the uncorrected responsivity nonuniformity is less than 4% (sigma/mean), and time constant for these arrays was measured at <8msec. We will report detailed FPA performance results including responsivity, noise, uniformity and pixel operability. We also plan to present video imagery from the most recent FPAs. The reduction in pixel size offers several potential benefits for IR systems. For a given system resolution (IFOV) requirement, the 20 μm pixel will allow an optical volume that is 50 % the size of a 25 μm based system! We will also provide an update on the enhanced performance and yield producibility of our NVESD ManTech 640 × 480 25 μm arrays, and also show data on 25 μm arrays that have been designed for faster time constants (5 ms), while maintaining high performance. We will also show the improvement in our uncooled 320 × 240 and 640 × 480 sensor electronics in terms of reduced power and size for helmet and rifle mounted sensors.

Uncooled detector development at Raytheon

At the 2010 meeting of the Defense and Security Symposia Raytheon reported on the status of their efforts to establish a high rate uncooled detector manufacturing capability. At that time we had just finished the transition of the 640 × 480, 25 μm product to our 200 mm wafer fab line at Freescale semiconductor and established an automated packaging and test capability. Over the past year we have continued to build on that foundation. In this paper we will report on this years progress in completing the transition of our 25 μm product line to Freescale semiconductor. Included will be the 320 × 240 product transition and a summary of SPC and defectivity data from one years production. Looking beyond 25 μm, we are well along in our transition of the 17 μm product line to Freescale, with test results being available for the 640 × 480. Additionally, we will report on progress / status of the Tailwind program, which is developing a 2048 × 1536, 17 μm uncooled sensor. Data to be reported includes the establishment of subfield stitching at a high rate commercial fab and the development of the detector package and electronics. With 17 μm transitioned to production, Raytheon has started work on the HD LWIR program, which is laying the foundation for the next generation of uncooled detectors by further shrinking the pixel to <17 μm. With the HD LWIR program just beginning, we will review our development strategy and program plan.

Expanded applications for high performance VOx microbolometer FPAs

RVS is producing high-quality microbolometer FPAs with 25 μm pixels. We have developed formats in both 320 x 240 and 640 x 480 array formats. These FPAs have demonstrated sensitivities that are comparable to microbolometer FPAs with 50 μm pixels with the best measured NETD value for these FPAs now <25mK with an f/1 aperture and operating at 30 Hz frame rates. Pixel operability is greater than 99.9% on most FPAs, and uncorrected responsivity nonuniformity is less than 3% (sigma/mean). These 25 μm microbolometer detectors also have a relatively fast thermal time constant of approximately 10 msec. These arrays have produced excellent image quality, and are currently fielded in a variety of systems. We will report on our latest performance data and IR captive flight test imagery. We will also show data on 25μm arrays that have been designed for faster time constants (5 msec), while maintaining high performance. RVS is also developing a 320 x 240 50μm mid-wave responding FPA. We will review the MWIR sensitivity improvements with this array and provide IR imagery. RVS is developing a 640 x 480 25μm uncooled FPA for a countermine detection application using a two-band assembly designed to be sensitive in both the Restrahlen and Thermal spectral bands. We will provide IR image data on these arrays. RVS has made a significant breakthrough in the development of a 640 x 512 array with a unit cell size of 20 μm x 20 μm, and performance approaching that of the 25μm arrays. The successful development of this array is the first step in achieving mega-pixel formats. This FPA is designed to ultimately achieve performance near the temperature fluxuation limited NETD (<20mK, f/1, 30 Hz). We will show updated performance and imagery on these arrays, which is currently being measured at <45mK, f/1, 30 Hz.

Megapixel InGaAs arrays for low background applications

Large focal planes with InGaAs detector arrays have been developed that meet the demanding requirements of astronomy and other low background systems. With high quantum efficiency between 0.9 and 1.7 μm, the InGaAs detectors are ideally suited for many SWIR applications. This paper describes two types of arrays with more than one million detector elements-one with 1280 × 1024 elements and the other with 1024 × 1024 elements-developed by Raytheon Vision Systems with detectors provided by Sensors Unlimited. The detector elements of both formats are on a 20 μm pitch. The 1024 × 1024 array utilizes a standard Virgo astronomy multiplexer (readout) that reads out the array at a maximum frame rate of 8 Hz. An innovative readout was designed for the 1280 × 1024 array with the support of DARPAs MANTIS program. This readout features a high gain front-end amplifier that can operate up to a 60 Hz frame rate and is designed to operate at room temperature. Summary performance data of each of these array types are presented.

RVS Uncooled Sensor Development for Tactical Applications

RVS has made a significant breakthrough in the development of an athermal (TECless) 640 x 480 uncooled sensor with a unit cell size of 17 μm x 17 μm, and performance approaching that of the 25μm arrays. The sensor design contains a highly productized FPA and is designed to achieve excellent sensitivity (low NETD and low spatial noise) with good dynamic range. The improved performance is achieved through bolometer structure improvements, innovative ROIC design, and flexible, low power electronics architecture. We will show updated performance and imagery on these sensors, which is currently being measured at <50mK, f/1, 30 Hz. Pixel operability is greater than 99 % on most FPAs, and uncorrected responsivity nonuniformity is less than 3% (sigma/mean). The combination of reduced FPA pixel size and improved effective thermal sensitivity enhances performance by providing smaller, lighter-weight systems via reduced optics size. Or, alternatively, increased range via enhanced pixel resolution without increasing mass (maintaining optical size). We will also show the advancements made in our uncooled common architecture electronics in terms of reduced power and size for man-portable and missile applications.