Although the rapid development of 2-D focal plane arrays of thermal infrared (IR) detectors has led to remarkable progress in uncooled IR imaging technology, a major limitation of these sensors is the lack of true on-chip spectral discrimination. Multi-spectral detection capabilities enable rapid, efficient and multi-dimensional scene interpretation that is especially beneficial to advanced IR imaging systems for early threat warning and target recognition applications. We propose a novel design for a monolithic micromachined array of bolometric detectors capable of multi-spectral
imaging in the long-wave IR (7-14 μm) region. The central ingredient of this approach is to employ planar multi-mode antenna structures to efficiently couple incident electromagnetic radiation to a microbolometeric sensing element that is much smaller than the IR wavelength. The wavelength selectivity of such an antenna-coupled detector can be tuned by optimizing its multiple geometric parameters. We present a planar microbolometer design that can accomplish 3-color LWIR imaging with no moving parts analogous to solid-state color videography in the visible region. The proposed effort targets applications of uncooled color IR imaging where the benefits in space, power, weight and complexity will have a significant impact.
Advanced autonomous detection of chemical warfare agents and toxic industrial chemicals has long been a major military concern. At present, our capability to rapidly assess the immediate environment is severely limited and our domestic infrastructure is burdened by the meticulous procedures required to rule out false threats. While significant advances have recently been accomplished in remote spectral sensing using rugged FTIRs and point detectors, efforts towards low cost chemical discrimination have been lacking. Foster-Miller has developed a unique waveguide spectrometer which is a paradigm shift from the conventional FTIR approach. The spectrometer provides spectral discrimination over the 3-14 μm range and will be the spectrometer platform for both active and passive detection.
Foster-Miller has leveraged its innovations in infrared fiber-optic probes and the recent development of a waveguide spectrometer to build a novel infrared sensor platform for both point and stand-off chemical sensing. A monolithic wedge-grating optic provides the spectral dispersion with low cost thermopile point or array detectors picking off the diffracted wavelengths from the optic. The integrated optic provides spectral discrimination between 3-12 μm with resolution at 16 cm<sup>-1</sup> or better and overall optical throughput approaching 35%. The device has a fixed cylindrical grating bonded to the edge of a ZnSe conditioning “wedge”. The conditioning optic overcomes limitations of concave gratings as it accepts high angle (large FOV) light at the narrow end of the wedge and progressively conditions it to be near normal to the grating. On return, the diffracted wavelengths are concentrated on the discrete or array detector (pixel) elements by the wedge, providing throughput comparable to that of an FTIR. The waveguide spectrometer coupled to ATR probes, flow through liquid cells or multipass gas cells provides significant cost advantage over conventional sampling methodologies. We will present the enabling innovations along with present performance, sensitivity expectations and discrimination algorithm strategy.
A small, low-cost sensor capable of autonomous detection of a wide variety of chemical agents in either vapor, particulate or liquid phase is urgently needed. It now appears that this need also extends to homeland defense and the vast network of civilian security forces including police, fire, public health and emergency medical personnel. We are developing a low-cost, compact infrared Chemical Threat Monitor (CTM) that could meet this need. This palm-sized handheld instrument combines Foster-Miller's unique optical "wedge" technology coupled to novel, disposable infrared fiber optic sensors for sample collection. These technologies will be coupled to emerging high sensitivity, low-cost uncooled linear array infrared detectors optimized for this application. This combination will provide the individual user with most of the capability of today’s expensive FTIR units in a miniature robust unit that has no moving parts. In this paper we will describe the CTM device, its operation, and present preliminary results on liquid chemical agent simulants.
Advanced autonomous detection of both chemical warfare agents and toxic industrial chemicals has long been of major military concern and is becoming an increasingly realistic need. Foster-Miller has successfully designed and demonstrated a high spectral throughput monolithic wedge spectrometer capable of providing early, stand-off detection of chemical threats. Recent breakthrough innovations in IR source technologies, high D* multispectral array detectors, and IR waveguide materials has allowed for the development of a robust, miniature, monolithic infrared spectrometer. Foster-Miller recently demonstrated a high resolution spectrometer operating in the 8 to 12 micron region for chemical agent detection. Results will be presented demonstrating the feasibility of adapting the wedge spectrometer to operate as an upward looking ground sensor for stand-off chemical detection. Our miniaturized spectrometer forms the basis for deploying low cost, lightweight sensors which may be used for reconnaissance missions or delivered to remote locations for unattended operation. The ability of perform passive stand-off infrared chemical agent and chemical emissions detection with a low cost, compact device that can operate autonomously in remote environments has broad applications in both the military and commercial marketplace.