Optical Surfaces Ltd (Kenley, Surrey, UK) can typically produce off-axis
parabolic mirrors up to 600 mm in diameter with surface accuracy's to
lambda/20 p-v depending upon off-axis angles. With proprietary polishing
techniques, Optical Surfaces can, depending on the surface accuracy required,
achieve the natural limit to the off-axis angle of around 25-30 degrees and
surface micro-roughness on aspherics of ~1 nm rms. A range of coatings is
available for standard and custom components from metallic – with protective
overcoat – to multilayer dielectrics and ultra-hard coatings. Parabolic
mirrors are the most common type of aspheric used in optical instruments.
They are free from spherical aberrations, and thus focus a parallel beam to a
point or a point source to infinity.
This week's Question: Amazon recently filed a patent for parachute-aided delivery of packages. The proposed idea imagines drones releasing parcels from the sky, deploying parachutes to slow their descent and ensure the valuables inside remain...
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