Design and application of omnidirectional mirror for catadioptric optical system dedicated to high-speed video registration of lightning

• Design of omnidirectional mirror dedicated for lightning location purposes. • Mirror with settable reflection angle range and projection characteristics. • Increasing of image quality for mirror projection generated on optical sensor. • Improved optical observation at different distances from catadioptric optical setup. • Universal design process applicable to other branches of science and industry. Omnidirectional optical mirrors are widely used in many scientific, industrial and military applications but there is still a lot to do to improve their projection characteristics. The paper presents design method for a novel class of omnidirectional mirrors characterized by their settable reflection angle and 3D/2D image projection. Such approach can effectively improve the mirrored image distribution on matrix of optical sensor. A complex mirror curvature was manufactured with application of computerized numerical control milling machines and Physical Vapor Deposition technique. Three prototypes with 15°, 30° and 45° vertical top view angles were tested. Mirrors were applied to get a set of wide range cloud-to-ground lightning video registrations. Analysis of the high-speed video confirmed design assumptions, and using lightning location system data, enabled dimensioning and measurement of the lightning channel geometry in 3D. Proposed method can be easily implemented in other applications involving omnidirectional observation and photogrammetry.