William J. Parrish

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.

Very wide dynamic range SWIR sensors for very low background applications

This paper describes a high performance 320 by 256 readout integrated circuit (ROIC) designed for P-on-N short wave IR (SWIR) detectors including InGaAs and HgCdTe, which also has the ability to operate at low input current levels with N- on-P detectors. The ROIC/FPA will support a wide range of system requirements from very low background applications to daytime high illumination conditions. To accommodate the wide scene dynamic range requirements, two selectable integration capacitors are used to control the input circuit transimpedance gain. A 10fF integration capacitor is used for low noise and low flux levels down to 10-5 ft Lambert, corresponding to approximately 2 X 1010 ph/cm2-sec for 0.9 micrometers to 1.7 micrometers spectral band using f/1.5 optics, assuming a 2856 Kelvin blackbody distribution. For higher flux levels, a 0.21pF integration capacitor can be selected, thus providing over a factor of 20 dynamic range. A capacitive feedback transimpendance amplifier provides a low noise detector interface circuit capable of operating at low input currents without frame-to- frame image lag. A sample and hold capacitor is also part of the input unit cell architecture, which allows the FPA to be operated in full frame snapshot mode and provides the maximum integration time available. The integration time is electronically controlled by an external clock pulse, and is adjustable form 0.5microsecond(s) ec to approximately the frame time of 33.3 msec for 30Hz operation. This produces an additional factor of 66,000 to the total nine orders of magnitude in scene dynamic range.

Microbolometer development and production at Indigo Systems

While microbolometers have been in production for several years, the number of companies producing them is quite small. Indigo Systems has entered into the development and production of VOx based microbolometers, at its Goleta facility. Through the investment of significant capital, Indigo has established a high volume production facility based on the silicon industry model. The 6-inch, cassette-to-cassette, highly automated facility is capable of yielding hundreds of thousands of die per year. Discussed in the paper will be the design and layout of the facility, performance of the devices, as well as yield, trend and throughput data.

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.

128 x 128 MWIR InSb focal plane and camera system

The need for increased resolution and sensitivity in IR systems applications has provided the impetus for the development of high-performance second-generation staring focal plane array technology. Previously, the availability of these focal plane array components has been limited and the costs associated with delivery of useful hardware have been high. Utilizing proven InSb detector technology and foundry silicon CMOS processes, a high performance, affordable hybrid focal plane array and support electronics system has been developed. The 128 X 128 array of photovoltac InSb detectors on 50 micrometers centers is interfaced with the silicon readout by aligning and cold welding indium bumps on each detector with the corresponding indium bump on the silicon readout. The detector is then thinned so that it can be illuminated through the backside. The 128 X 128 channel signal processing integrated circuit performs the function of interfacing with the detectors, integrating the detector current, and multiplexing the signals. It is fabricated using a standard double poly, single metal, p-well CMOS process. The detector elements achieve a high quantum efficiency response from less than 1 micrometers to greater than 5 micrometers with an optical fill factor of 90%. The hybrid focal plane array can operate to a maximum frame rate of 1,000 Hz. D* values at 1.7 X 1014 photons/cm2/sec illumination conditions approach the BLIP value of 9.4 X 1011 cm(root)Hz/W with a capacity of 4 X 107 carriers and a dynamic range of greater than 60,000. A NE(Delta) T value of .018 C and a MRT value of .020 C have been measured. The devices operate with only 3 biases and 3 clocks.

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.

Standardized high performance readout integrated circuits enable rapid development of QWIP imaging systems

Abstract This paper describes standardized high performance 320 by 256 (ISC9705 or ‘Standard 320’) and 640 by 512 (ISC9803 or ‘Standard 640’) readout integrated circuits (ROICs) for detectors such as InSb, InGaAs, and QWIP, including presentation of focal plane array (FPA) test results for QWIP FPAs fabricated on the ISC9705 and ISC9803 ROICs. The availability of detector interface layout databases, complete test results for each die, and off-the-shelf imaging electronics enable rapid development of imaging systems using QWIP detector arrays. The ROICs are intended to support a wide range of systems through flexibility and advanced modes of operation, and include features such as high-detector bias, programmable gain and signal ‘skimming’ to improve the performance of QWIP FPAs fabricated with these devices. The ROICs also support such advanced features as dynamic image transposition, dynamic windowing, multiple high-speed output configurations, and flexible snapshot integration. These arrays are part of the Indigo Systems family of standard ROICs that share a common architecture and electrical interface.

Technical overview of the UL3 ALPHA and OMEGA uncooled cameras

This paper describes two camera systems based on the advanced 160 X 128 uncooled micro-bolometer FPAs. The UL3 ALPHA camera is in production and takes advantage of the patented bias equalization FPA performance to produce the worlds smallest IR production camera. UL3 ALPHA weighs less than 195 grams, uses 1.5 W of power (nominal) and has a overall dimensions of 4.3 cm X 4.3 cm X 7.5 cm. ULS ALPHA production cameras have demonstrated 62 mK NEdT operation with over 99% operability.

160 x 128 uncooled FPA performance review

This paper presents background and measured performance data on a novel, low cost, high performance readout integrated circuit (ROIC) for microbolometer uncooled detector applications. The array is designed to offer better than 80mK NEdT performance using f/1.8 optics. The design incorporates advanced on-ROIC signal processing electronics that allow 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.

Technical overview of the UL3 uncooled cameras

This paper describes the UL3 camera system based on the advanced 160 X 128 uncooled micro-bolometer FPA. The UL3 camera takes advantage of the patented bias equalization FPA performance techniques to produce the worlds smallest IR camera. The UL3 camera weights less than 2.3 ounces, uses less than 600 mW of power, and has overall dimensions of 3 cm X 3 cm X 6 cm. The architectures feature an approach that integrates the required system functions on ASICs and FPGAs rather than including discrete components and microprocessors.