Deformable mirror e.g. for focussing laser beam - has fixing collar of shape-memory alloy, attached by radial forces at one temp. and released at other temp.

摘要

The deformable mirror consists of a mirror plate (12) with a boss (24) on its rear surface to attach it to an actuator (28) which applies a force to the mirror, changing the focus of a laser beam impinging on the mirror. The actuator contains a number of piezoelectric elements (28) connected in parallel. Liquid nitrogen coolant enters and leaves the device by channels (46,48). The mirror (24) is fixed to the actuator by a fixing collar (54). This is made from a Nickel Titanium alloy (NiTi) which undergoes a change in crystalline structure from austenitic to martensitic with temperature. With a change in temperature, the dimension of the collar switches from diameter D1 to D2. To release the mirror for exchange, liquid nitrogen coolant is supplied to reduce the temperature of the collar to -150 deg.C. To fix the replacement device, a heating current is applied to heater (58) to raise the collar temperature to 150 deg. C. The collar switches state (constrained recovery) to shrink in place, holding the mirror firmly. ADVANTAGE - Simplified exchange of actuator.