Jeff A. Ridley

Recent progress in large dynamic resistor arrays

An addressable mosaic array of resistively heated microbridges offers the potential to project accurate dynamic infrared (IR) imagery. The main purpose of this imagery is to be used in the evaluation of IR instruments from seekers to FLIRs. With the growing development of lower cost uncooled IR imagers, scene projectors also offer the potential for dynamic testing of these new instruments. In past years we have described developments in a variety of IR projectors systems designed for different purposes. In this paper we will describe recent developments in these technologies aimed at improving or understanding temporal and radiative performance.

Large-area infrared microemitter arrays for dynamic scene projection

Resistive emitter arrays are formed via the fabrication of microemitters on Si CMOS electronics. These IR emitter arrays using microstructures have been developed at Honeywell to project scenes for a wide range of applications. A new array which has been fabricated has a size of 544 X 672 pixels. Other arrays producing very high apparent temperatures in excess of 700 K have also been fabricated. Arrays have been fabricated for projecting low background scenes achieved through cryogenic operation. All arrays are designed to project IR radiation over the full MWIR and LWIR spectral bands. Individual arrays and their emission properties will be described. Array properties at different substrate temperatures will be described. Advances in packaging of these different array types will also be discussed.

Innovations in IR projector arrays

In the past year, Honeywell has developed a 512 X 512 snapshot scene projector containing pixels with very high radiance efficiency. The array can operate in both snapshot and raster mode. The array pixels have near black body characteristics, high radiance outputs, broad band performance, and high speed. IR measurements and performance of these pixels will be described. In addition, a vacuum probe station that makes it possible to select the best die for packaging and delivery based on wafer level radiance screening, has been developed and is in operation. This system, as well as other improvements, will be described. Finally, a review of the status of the present projectors and plans for future arrays is included.

512×512 Infrared cryogenic scene projector arrays

Abstract A mosaic array of resistively heated microbridges offers much flexibility for infrared scene simulations. Dynamic scene simulations are important for the testing of the real-time performance capability of IR camera and seeker systems. The excellent thermal properties of the emitter pixels achieved with thin films and unique thermal isolation structures make it possible to achieve high temperatures at power levels ≈ 1 μW per pixel per degree temperature rise. High radiance and high dynamic range are achieved by having pixels with high emissivity and high fill factors, which operate with the substrate and drive electronics at cryogenic temperatures to achieve low background radiance. The thermal time constants of the pixels are defined by material properties and pixel design and are in the millisecond range, making it possible to achieve dynamic frame rates in excess of 100 Hz. Two types of cryogenic resistor arrays have been fabricated and are described, 512×512 arrays with pixels on a 3.5 mil pitch, and 128×128 arrays with pixels on a 2 mil pitch.

512x512 WISP (wideband infrared scene projector) arrays

An addressable mosaic array of resistively heated microbridges offers much flexibility for infrared scene simulations. In the Wide Band Infrared Scene Projector program, Honeywell has demonstrated high yield arrays up to size 512 X 512 capable of room temperature operation for a 2 band infrared projection system being designed and built by Contraves Inc. for the Wright Laboratory Kinetic Kill Vehicle Hardware In-the-Loop Simulator facility at Eglin Air Force Base, FL. The arrays contain two different pixel designs, one pixel designed for kHz frame rates and high radiance achieved at a power level of 2.5 mWatts/pixel and the other pixel designed for more moderate 100 Hz frame rates at lower radiance and at maximum power levels of 0.7 mWatts/pixels. Tests on arrays and pixels have demonstrated dynamic ranges up to 850:1, radiance rise times on the order of 2 mseconds, and broadband pixel emissivities in the range of 70%. Arrays have been fabricated with less than 0.1% pixel outages and no row or column defects. These arrays are mounted in a specialized vacuum assembly containing an IR window, vacuum package, cooling block, and pump out manifold.

Honeywell resistor array development and future directions

In 1991 the Honeywell Technology Center began the development of large area 2D microemitter arrays for IR scene projection. Since then, 5 different types of 512 X 512 or larger arrays have been fabricated, all in current use. This paper will review the status, properties, and applications of these arrays. Pixel and array improvements which will lead to ultralow power consumption, very high performance, very fast 1024 square arrays are under development. A number of these efforts are described.

IR detector system for the GERB instrument

The Geostationary Earth radiation Budget (GERB) instrument will play an important role in Earth Observation Science, when it is launched on ESAs Meteosat Second Generation (MSG) satellite in 2000. The purpose of the instrument is to measure the reflected and emitted radiation of the Earth over at least a five year period, to an accuracy better than 1% within a 15 minute observation period. These scientific requirements have resulted in a detector system comprising several technological advances. The detector chosen for this instrument is a 256 pixel linear array of thermoelectric (TE) elements operating at room temperature. Based on an existing commercial design, the detector has pushed micromachined thermoelectric arrays to its limits to achieve the noise requirements. The spectral requirements of the instrument to give a flat spectral response over the 0.32 - 30 micrometer range has necessitated the blacking of the TE array. Blacking such small area arrays is a novel application and presented several problems during the course of the development. The signal conditioning electronics, consisting of 4 Application Specific Integrated Circuits, performs front end analogue signal processing, A/D conversion and multiplexing. The design of the detector system is presented in this paper, with the packaging, signal processing and blacking described in some detail.

512x512 cryovacuum resistor infrared scene projector

A mosaic array of resistively heated microbridges offers flexibility for infra red scene simulations. The array may operate without flicker and display high-intensity dynamic scenes over a wide bandwidth. Honeywell completed fabrication of a 512 X 512 resistor array with 3.5 mils pitch for AEDCs 7V and 10V test chambers. The emitter has a broad bandwidth covering from 2 micrometers to 26 micrometers . The array operates at 20 K to simulate low radiation backgrounds in space. Up to 16,000 pixels may be turned on to simulate targets and target clusters. Each emitter element may heat up to 550 K with 1 kelvin resolution. The maximum power dissipation per pixel is 830 (mu) W for a pixel heated up to 550 K. The maximum power required is 13.2 watts for 16,000 pixels. This low power capability is derived from Honeywells silicon nitride microbridge structure. Each emitter has approximately 85% fill factor and an average emissivity of 70% over the 2 - 26 micrometers bandwidth. Defect count in the array is less than 1% with one column out. The array may be addressed at 30 frames per second.

High-speed large-area pixels compatible with 200-Hz frame rates

Honeywell has developed a high-speed infrared emitter pixel and implemented the design on two 512 X 512 scene projector array designs. This pixel is a faster version of the original Gen-III Gossamer pixel implemented on previous 512 X 512 arrays. The new pixel has a 10% - 90% rise time under 4 milliseconds, enabling a dramatic increase in scene projection frame rates over currently available arrays. Full array frame rates of 200 Hz are not practical and subarrays can be driven up to 400 Hz. In spite of the increased speed, the array still maintains high brightness using the same CMOS electronics. This design and other array developments will be described.