Amorphous Materials began in 2000 a joint program with Lockheed Martin in Orlando to develop molding
technology required to produce infrared lenses from chalcogenide glasses. Preliminary results were
reported at this SPIE meeting by Amy Graham1 in 2003. The program ended in 2004. Since that time, AMI
has concentrated on improving results from two low softening glasses, Amtir 4&5. Both glasses have been
fully characterized and antireflection coatings have been developed for each. Lenses have been molded
from both glasses, from Amtir 6 and from C1 Core glass. A Zygo unit is used to evaluate the results of each
molded lens as a guide to improving the molding process. Expansion into a larger building has provided
room for five production molding units. Molded lens sizes have ranged from 8 mm to 136 mm in diameter.
Recent results will be presented
Efforts have resumed to improve the image quality of infrared imaging bundles formed at AMI using the ribbon stacking method. The C4 glass has been used to reduce core size, increase packing density and improve flexibility. Ribbons are formed from unclad fiber wound on a drum with pitch, ribbon count and spacing between ribbons computer controlled. A small portion of each ribbon is compressed and fused using thin, dilute Epoxy. Unfortunately, the Epoxy, serving as a clad, absorbs most all the LWIR energy making the bundles unsuited for 8-12 μm cameras. The ribbons are removed from the drum and stacked, one on top of the other observing proper orientation to form the bundle. A typical 1 meter bundle is formed from 50-70 count ribbons for a total of 2500-4900 fibers, made from 2.5-4.9 Km of C4 fiber. Typical core diameters are 60-80 μm. Active surface area ranges from 60-70%. Infrared resolution images formed using a NIR tube camera equipped with a special relay lens demonstrates the resolution limit for the bundle. Currently, the limit is about 10 lp/mm. The bundle end is imaged in the 3-5 μm Agema 210 camera using an Amtir 1 F/1 meniscus, coated 3-5 μm. Video images taken in natural light of an individual, easily recognizable at 50 feet, will be shown. Results of careful evaluation carried out at Lockheed Martin in Orlando using a high performance Raytheon Galileo camera will be presented.
With the advent of the uncooled detectors, the fraction of infrared (IR) imaging system cost due to lens elements has risen to the point where work was needed in the area of cost. Since these IR imaging systems often have tight packaging requirements which drive the optical elements to have complex surfaces, typical IR optical elements are costly to manufacture. The drive of our current optical material research is to lower the cost of the materials as well as the element fabrication for IR imaging systems. A low cost, moldable amorphous material, Amtir-4, has been developed and characterized. Ray Hilton Sr., Amorphous Materials Inc., Richard A. LeBlanc, Amy Graham and Others at Lockheed Martin Missiles and Fire Control Orlando (LMMFC-O) and James Johnson, General Electric Global Research Center (GE-GRC), along with others have been doing research for the past three years characterizing and designing IR imaging systems with this material. These IR imaging systems have been conventionally fabricated via diamond turning and techniques required to mold infrared optical elements have been developed with this new material, greatly reducing manufacturing costs. This paper will outline efforts thus far in incorporating this new material into prototype IR imaging systems.
Most seeker systems are designed for a single mission, making the cost of the seeker of prime importance. Uncooled detector arrays are significantly less expensive than their cooled counterparts but infrared optics remain a significant cost driver. We have designed and developed an optical system with a long focal length and short physical length that can be fabricated inexpensively; yet deliver the performance required of an infrared seeker. The Folded Molded Mangin is the result of several iterations that yielded a unique optical system that meets those requirements. The system can be fabricated using conventional diamond turning techniques or by molding.
A midwave infrared (IR) imager with silicon lenses and a laminated plastic surface has been made. It has a focal length of 50 mm and f/# of 2.6. Typically this type of lens system would be made out of silicon, germanium, or some other materials transparent in the midwave infrared regime. The design of the lens system would include aspheric and/or diffractive surfaces that require the use of a single point diamond turning machine to make it. In this system aspheric/diffractive silicon lenses have been replaced with a flat piece of silicon coated with a thin layer of plastic that has an aspheric/diffractive surface.
This paper gives an overview of Lockheed Martin's effort as part the DARPA Three Dimensional Imaging Sensors Program. The overall system, the detector technology, the ROIC approaches, and the system model are discussed. The system approach has a laser transmitter that illuminates the entire sensor field-of-view (FOV) with a single laser pulse and collects the returned energy on a focal plane array (FPA) where each picture element (pixel) measures range. The detector is a short wavelength infrared HgCdTe APD array based on DRS Infrared Technology's well established architecture of HDVIP.. The ROICs implement 'on-chip' pixel level signal processing to generate 3-D imagery. The model is used to make predictions based on range, power, aperture, weather and FPA characteristics to help forecast expected device/readout/system performance.
A model for staring focal plane arrays is described. The model characterizes two types of detectors, the platinum silicide (PtSi) Schottky-barrier diode and the mercury-cadmiun-tellurium (MCT) detector. The MCT devices provide high performance in both the 3-5-micron and 8-12-micron regions, while the Schottky devices, functioning only in the 3-5-micron band, provide high density and economy.
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