For over 50 years, Optical Surfaces Ltd has been working with materials including fused silica, BK-7 and Germanium to produce defence grade windows up to 600mm in diameter. Large diameter optical windows for defence applications are typically used to provide environmental protection for sensitive internal sensing systems. To transmit light with minimal disruption, these large diameter optical windows must exhibit low surface roughness, minimal transmitted wavefront errors, and high transmission at the desired operational wavelength range.
Direct qualification of large diameter optical windows
Benefiting from an ultra-stable production environment and proprietary polishing technique, the large diameter optical windows have typical wavefront error of up to lambda/20 p-v, surface roughness of less than 10 Å rms and surface finish of 40/20 to 10/5 scratch / dig.
Dr Aris Kouris, Sales Director of Optical Surfaces Ltd commented “To enable us to quality test large diameter optical windows – we developed a 600mm Fizeau interferometer. This is a capability that only a few optical testing and manufacturing centres around the world possess. Housed in an ultra-stable testing environment, this interferometric set-up allows direct qualification of large diameter optical windows by testing them directly over their complete aperture without the need to use time-consuming combination methods”.