Description
Objective: The objective of this effort is to obtain low cost infrared optics for attritable unmanned drone vehicles. The scope of this topic is to investigate whether alkali-halide optical materials can be used as cost-effective alternatives to the more traditional materials used in military-grade uncooled infrared sensors. A preferred use-case encompasses an uncooled infrared sensor such as the Odd Systems Kurbas-640, which has a focal plane containing 640 × 512 detector elements with a 12 micron pitch spacing, and which is combined with an imaging lens having an 18 mm focal length operating at F#/1.1 and with a transmission exceeding 70%. Description: Modern warfare has increased the demand for low-cost, attritable unmanned drone vehicles. Examples of such platforms used worldwide are the Shahed 136 and the LUCAS. Thermal cameras give these platforms the ability to operate at night and under adverse weather conditions. Uncooled thermal infrared focal plane detectors, operating in the 7.5 - 12.0 micron spectrum, are often the most cost effective for this purpose. Each camera requires a lens to focus the radiation from the scene onto the detector. Traditional military optical lens materials which are transmissive in this spectral region include Ge, ZnSe, ZnS, as well as various chalcogenide glasses which typically contain elements such as Ge, Ar, Se, S, or Te in various ratios. All of these infrared optical materials are significantly more expensive than the optical glasses used for visible-spectrum optical devices such as binoculars and telescopes. In many cases, the optics cost may exceed the cost of the detector assembly, resulting in the night vision sensor subsystem accounting for ⅓ or more of the total cost of the whole drone system. However, there exists a family of significantly lower cost optical materials known as "alkali-halides" which include compounds such as NaCl, CsBr, and KBr. These "salt" materials provide exceptional spectral transmission over the infrared bands, and are widely used for laboratory spectrometers in the scientific instrument markets. The military has traditionally not made use of the alkali-halide optical materials in the past, however, because they are all very susceptible to damage when exposed to water and moisture. Moisture resistance is important for both field use as well as long-term storage. Keywords: alkali-halide, optics, lenses, protective coatings, moisture resistance, uncooled infrared, unmanned drones, attritable, low cost. CMMC Level: Level 1