James T. Woolaway

Demonstration of Megapixel Dual-Band QWIP Focal Plane Array

Quantum well infrared photodetectors (QWIPs) are well known for their stability, high pixel-pixel uniformity and high pixel operability which are quintessential parameters for large area imaging arrays. In this paper we report the first demonstration of the megapixel-simultaneously-readable and pixel-co-registered dual-band QWIP focal plane array (FPA). The dual-band QWIP device was developed by stacking two multi-quantum-well stacks tuned to absorb two different infrared wavelengths. The full width at half maximum (FWHM) of the midwave infrared (MWIR) band extends from 4.4-5.1 ¿m and FWHM of the long-wave infrared (LWIR) band extends from 7.8-8.8 ¿m. Dual-band QWIP detector arrays were hybridized with direct injection 30 ¿m pixel pitch megapixel dual-band simultaneously readable CMOS read out integrated circuits using the indium bump hybridization technique. The initial dual-band megapixel QWIP FPAs were cooled to 68 K operating temperature. The preliminary data taken from the first megapixel QWIP FPA has shown system NE¿T of 27 and 40 mK for MWIR and LWIR bands, respectively.

Improvements in uncooled systems using bias equalization

This paper describes a new approach for the control of microbolometer detector array uniformity as a function of substrate temperature change. This approach, called the bias equalization method, uses an electronic means of controlling the microbolometer array uniformity. For this method a three stage non-uniformity correction algorithm is employed. The first stage corrects for substrate temperature non- uniformity effects on the microbolometer detector elements followed by traditional offset and gain non-uniformity correction stages. To correct for substrate temperature non- uniformity effects, bias equalization coefficients are supplied to the readout integrated circuit (ROIC) to allow the control of a unique operating bias or temperature delta for each microbolometer detector element in the array. The bias equalization method circuitry allows microbolometer array non-uniformity control over a wider range of ROIC substrate temperatures while maintaining better than 80 mK NEdT using f/1.8 optics. This approach is expected to allow removal of the thermoelectric cooler from uncooled systems, thus making it ideally suited for high-volume, low-cost, low-power and low-weight production applications.

Toward dualband megapixel QWIP focal plane arrays

Mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) 1024x1024 pixel InGaAs/GaAs/AlGaAs based quantum well infrared photodetector (QWIP) focal planes have been demonstrated with excellent imaging performance. The MWIR QWIP detector array has demonstrated a noise equivalent differential temperature (NE&Dgr;T) of 17 mK at a 95K operating temperature with f/2.5 optics at 300K background and the LWIR detector array has demonstrated a NE&Dgr;T of 13 mK at a 70K operating temperature with the same optical and background conditions as the MWIR detector array after the subtraction of system noise. Both MWIR and LWIR focal planes have shown background limited performance (BLIP) at 90K and 70K operating temperatures respectively, with similar optical and background conditions. It is well known that III-V compound semiconductor materials such as GaAs, InP, etc. are easy to grow and process into devices. In addition, III-V compound semiconductors are available in large diameter wafers, up to 8-inches. Thus, III-V compound semiconductor based infrared focal plane technologies such as QWIP, InSb, and strain layer superlattices (SLS) are potential candidates for the development of large format focal planes such as 4096x4096 pixels and larger. In this paper, we will discuss the possibility of extending the infrared detector array size up to 16 megapixels.

Low-cost 160 x 128 uncooled infrared sensor array

This paper present a novel low cost, high performance readout integrated circuit (ROIC) for bolometer uncooled detector applications. The array is designed to offer better than 80mK NEdT using f/1.8 optics. The design incorporates advanced on-ROIC signal processing electronics that allows bolometer element non-uniformity control over a wide range of ROIC substrate temperatures. The small format array is ideally suited for high volume low-cost production applications.

Development of megapixel dual-band QWIP focal plane array

Mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) 1024x1024 pixel InGaAs/GaAs/AlGaAs based quantum well infrared photodetector (QWIP) focal planes and a 320x256 pixel dualband pixel co-registered simultaneous QWIP focal plane array have been demonstrated as pathfinders. In this paper, we discuss the development of 1024x1024 MWIR/LWIR dualband pixel co-registered simultaneous QWIP focal plane array.

MIRAGE: large-format emitter arrays 1024 x 1024 and 1024 x 2048

The IR detector array, which is the heart of any imaging system or missile seeker, continues to evolve toward larger size, smaller pixels, and higher sensitivity. Any scene projector that is intended to test one of these advanced devices must keep pace. As IR scene projection evolves to 1024 X 1024 and 1024 X 2048 arrays, both the emitter array and drive electronics must overcome numerous technological challenges. This paper discusses the approach taken to provide the same 200 Hz frame rate, 16-bit accuracy, and high operability already demonstrated with 512 X 512 MIRAGE arrays in a larger format. In addition to current capabilities that are to be preserved in the design of larger devices, scalability of the architecture to allow growth to even larger formats is desired. Other features such as windowing and even higher frame rates are critical for future applications.

Toward 16 megapixel focal plane arrays

Mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) 1024x1024 pixel InGaAs/GaAs/AlGaAs based quantum well infrared photodetector (QWIP) focal planes have been demonstrated with excellent imaging performance. The MWIR QWIP detector array has demonstrated a noise equivalent differential temperature (NEΔT) of 17 mK at a 95K operating temperature with f/2.5 optics at 300K background and the LWIR detector array has demonstrated a NEΔT of 13 mK at a 70K operating temperature with the same optical and background conditions as the MWIR detector array after the subtraction of system noise. Both MWIR and LWIR focal planes have shown background limited performance (BLIP) at 90K and 70K operating temperatures respectively, with similar optical and background conditions. It is well known that III-V compound semiconductor materials such as GaAs, InP, etc. are easy to grow and process into devices. In addition, III-V compound semiconductors are available in large diameter wafers, up to 8-inches. Thus, III-V compound semiconductor based infrared focal plane technologies such as QWIP, InSb, and strain layer superlattices (SLS) are potential candidates for the development of large format focal planes such as 4096x4096 pixels and larger. In this paper, we will discuss the possibility of extending the infrared detector array size up to 16 megapixels.

Two-color quantum well infrared photodetector focal plane arrays

QmagiQ LLC, has recently completed building and testing high operability two-color Quantum Well Infrared Photodetector (QWIP) focal plane arrays (FPAs). The 320 x 256 format dual-band FPAs feature 40-micron pixels of spatially registered QWIP detectors based on III-V materials. The vertically stacked detectors in this specific midwave/longwave (MW/LW) design are tuned to absorb in the respective 4-5 and 8-9 micron spectral ranges. The ISC0006 Readout Integrated Circuit (ROIC) developed by FLIR Systems Inc. and used in these FPAs features direct injection (DI) input circuitry for high charge storage with each unit cell containing dual integration capacitors, allowing simultaneous scene sampling and readout for the two distinct wavelength bands. Initial FPAs feature pixel operabilities better than 99%. Focal plane array test results and sample images will be presented.

MIRAGE dynamic IR scene projector overview and status

The MIRAGE Dynamic IR Scene Projector is a standard product being developed jointly by Santa Barbara Infrared, Inc. and Indigo Systems Corporation. MIRAGE is a complete IR scene projection system, accepting digital or analog scene data as the input and providing all other electronics, optics and mechanics to project high fidelity dynamic IR scenes to the unit under test. At the heart of the MIRAGE system is the 512 X 512 microemitter array that incorporates many state-of-the-art features previously not available. The Read-In-Integrated-Circuit (RIIC) leverages technology from IR Focal Plane electronics to provide a system with advanced capability with low risk. The RIIC incorporates on chip DACs, snap-shot frame updating, constant current mode, voltage drive emitters and substrate ground plane providing high resolution and low noise performance in a very small package. The first 512 X 512 microemitter assembly has been received and was imaged on 2 APR 99. The complete MIRAGE system is currently in integration with the first deliverable unit scheduled for June 1999.

Infrared Technology Trends and Implications to Home and Building Energy Use Efficiency

It has long been realized that infrared technology would have applicability in improving the energy efficiency of homes and buildings. Walls that are missing or are poorly insulated can be quickly evaluated by looking at the thermal images of these surfaces. Similarly, air infiltration leaks under doors and around windows leave a telltale thermal signature easily seen in the infrared. The ability to view, evaluate and quickly respond to these images has immediate benefits in addressing and correcting situations where these types of losses are occurring. The principle issue that has been limiting the use of infrared technology in these applications has been the lack of availability and accessibility of infrared technology at a cost point suited to this market. The emergence of low cost microbolometer based infrared cameras, not needing sensor cooling, will greatly increase the accessibility and use of infrared technology for House Doctor inspections. The technology cost for this use is projected to be less...