Developments in Smart Optics
Several research teams were able to show their progress in development of components and systems.
Carl Paterson, of Imperial College London, introduced a PPARC and EPSRC funded programme aiming to provide an adaptive optics tool kit, so that the method could could be usefully deployed more widely. The aim was to provide "plug-and-play" components for a full system for under £10,000, and in a format such that it could be put together quickly without special expertise. The three fundamental components of AO systems, namely the deformable mirror, wave front sensor, and the integrated control system, were all being addressed, and it is planned to make the electrical and mechanical interface designs an open standard. The capability of the control system was key to this work, and also where the majority of the existing cost and complexity lies. A system that could inter-operate with deformable mirrors from a variety of sources is one aim of this programme.
Development work at UCL's Optical Sciences Laboratory, as presented by Peter Doel, showed some of the current capabilities and trade-offs within active mirror technology. Despite the complexities of the control systems, these could offer a route to considerable mass saving for space applications, even those which wouldn't normally benefit from an adaptive optics solution. It is important to bear in mind that the potential for weight saving should be considered at system level, since the use of an active mirror could permit relaxation of other structural and thermal requirements.
Gordon Love, of Durham University, showed single lenses that could be considered as useful active components. A liquid crystal cell with a suitable applied electric field will provide a variable refractive medium, allowing zoom and focus with no moving parts. Although the performance of that presently realised system was modest, work goes on to increase the size and optical power of the liquid-crystal cell, and a specific programme is underway to develop a compound system and characterise it for suitability for use in space.
Surfaces, such as radiators, with active thermal properties are likely to be especially useful for space missions with extreme thermal requirements. John Topping, from Oxford University's Department of Engineering Science, presented theoretical and development work on a novel thermo-chromic structure. This exploited the transition of VO2 between metallic and semiconductor states as a function of temperature. By coupling a layer of this material with an index matched coating, a surface of variable emissivity can be created. With additional doping, the transition temperature itself can be controlled. Once made, the performance of the surface is entirely autonomous (no external power requirement), and is expected to be highly damage-tolerant (in contrast with other variable emissivity systems in development).
