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High-performance space quality optical glasses are designed to provide outstanding optical clarity, high optical homogeneity and precise control of refractive index. These glasses are widely used for precision optical elements such as lenses, prisms, windows, attitude control (sun senor star sensor), imaging and instrumentation. The demand for such high-quality optical glasses are met by few well-known global manufacturers in Europe, Japan, and the USA. In India, no commercial manufacturer is engaged towards development of optical glasses. At the industrial scale, such high-quality optical glasses are typically produced using continuous tank melting which favours achievement of extremely high optical homogeneity; a process that is not feasible to adopt under laboratory conditions.
CSIR-CGCRI, the only national lab in the area of ceramics and glass in India, is known for contributions in the development of critical glass technologies for strategic, industrial, and societal applications, over last seven decades. In line with the Aatmanirbhar Bharat initiative, CSIR-CGCRI has taken up a challenge to develop five types of flint and crown based optical glasses in collaboration with VSCC ISRO and LEOS ISRO. The roadmap for development started from initial phase of laboratory-scale (50-100 ml) melts to gradually larger batch sizes (500ml to 5l) meeting the stringent optical properties through compositional optimization. State-of-the art facility (5l induction heating glass melting facilities of 1450°C and 1650° C) has been created for development cum production of optical glasses with stringent optical properties in terms of refractive index and Abbe number with optical homogeneity of the order of 10-5 to 10-6. Notably, some of the selected samples tested at LEOS, ISRO exhibited improved homogeneity close to 2×10⁻⁶, which is a significant and challenging achievement. Thus, CSIR-CGCRI has demonstrated the capability creating optical glass melting facility and glasses in the H1–H2 homogeneity category, which is a major step towards promoting national self-reliance. The quality assessment has been performed using LEOS facility. The manufacturing facility and stringent quality assessment have led to the successful maturation of the technology of space-quality optical glasses.