The actuator design and the experimental tests of a new technology large deformable mirror for visible wavelengths adaptive optics

摘要

Recently, Adaptive Secondary Mirrors showed excellent on-sky results in the Near Infrared wavelengths. Theycurrently provide 30mm inter-actuator spacing and about 1 kHz bandwidth. Pushing these devices to be operatedat visible wavelengths is a challenging task. Compared to the current systems, working in the infrared, the moredemanding requirements are the higher spatial resolution and the greater correction bandwidth. In fact, theturbulence scale is shorter and the parameter variation is faster. Typically, the former is not larger than 25 mm(projected on the secondary mirror) and the latter is 2 kHz, therefore the actuator has to be more slender andfaster than the current ones. With a soft magnetic composite core, a dual-stator and a single-mover, VRALA,the actuator discussed in this paper, attains unprecedented performances with a negligible thermal impact.Pre-shaping the current required to deliver a given stroke greatly simplifies the control system, whose outputsupplies the current generator. As the inductance depends on the mover position, the electronics of this generator,provided with an inductance measure circuit, works also as a displacement sensor, supplying the control systemwith an accurate feed-back signal. A preliminary prototype, built according to the several FEA thermo-magneticanalyses, has undergone some preliminary laboratory tests. The results of these checks, matching the designresults in terms of power and force, show that the the magnetic design addresses the severe specifications.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.