Active lens and mirror technology through tailored thermal expansion

Abstract

Adaptive and active optics grant the ability to correct for aberrations, focus and zoom factors changes, and compensate for environmental conditions. Hugely important in physical optics such as high resolution imaging and ground-based astronomy. Presented here is an adaptable lens and mirror technology capable of a full range of focal lengths and shapes. Using transparent oxides and the joule heating effect, local temperature changes can be induced to cause material expansion in a predefined shape based on the thermal distribution. By creating a constriction in the conductive layer adding resistance to the material and creating a localised heating element on the order of millimetres and below in scale. Actively changing the optical systems can be realised on the millisecond timescale additionally allowing an almost arbitrary lens shape as well as variable focal length. Similar effects can be exploited to create a deformable mirror where the active layer is a metallic reflector, such as aluminium or silver, and this layer is used to deliver heat using the same effects. Using this localised heating, focal lengths from infinity to a few centimetres can be achieved through highly expansive substrates and minimal heating and energy usage.A multitude of such elements can be constructed in such a way to provide a micro-lens array of different focal lengths allowing a field of view with simultaneous focusing on several objects at once for imaging applications. These elements can also be combined over a larger area to create astronomy grade deformable mirrors. The heated areas can be freely designed to any desired shape such as space filling hexagons and create an unconventional adaptive optics systems with advantages over conventional systems.