Production of complex chalcogenide glass optics by molding for thermal imaging

Abstract Work at Umicore IR Glass has focussed in the production of chalcogenide glasses and optics by molding. The standard glass compositions are Gasir1 with Ge22As20Se58 and Gasir2 with Ge20Sb15Se65. An industrial process has been developed to produce these two glasses with constant properties. The reproducibility of refractive index is for example better than 1.5 × 10−5 at 10 μm which is inside the precision of the measurements. An original and high precision molding technology has been developed to produce these low cost and high performance chalcogenide glass lenses. Spherical, aspherical and asphero-diffractive lenses have been obtained with very high surface precision. The form defect of the molded surface can be lower than 0.5 μm. Antireflection coatings have been deposited onto the molded lenses to reduce greatly the losses by reflection. 97% of transmission can be obtained with the antireflection coating, compared to about 70% of transmission for uncoated samples. The coated Gasir optics have been used in infrared camera and high-resolution thermal images have been obtained.