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We present the design and implementation of a very compact adaptive optics system that senses the return light from a sodium guide-star and controls a deformable mirror and a pointing mirror to compensate atmospheric perturbations in the wavefront. The deformable mirror has 19 electrostrictive actuators and triangular subapertures. The wavefront sensor is a Hartmann sensor with lenslets on triangular centers. The high-bandwidth steering mirror assembly incorporates an analog controller that samples the tilt with an avalanche photodiode quad cell. An f/25 imaging leg focuses the light into a science camera that can either obtain long-exposure images or speckle data. In laboratory tests overall Strehl ratios were improved by a factor of 3 when a mylar sheet was used as an aberrator. The crossover frequency at unity gain is 30 Hz.

We are developing an adaptive optics system that is based on an array of actuators arranged with subapertures that are equilateral triangles. The wavefront sensor is a video Hartmann sensor that also uses an equilateral array of lenslets. The controller hardware uses a VME bus. The design minimizes the generation of reflected wavefronts higher than first order across each lenslet for large excursions of actuators from positions where the mirror is flat and, thus maximizes the precision of the slopes measured by the Hartmann sensor. The design is also immune to the waffle mode that is present in the reconstructors of adaptive optics systems where actuators are arranged in a square array.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We have developed a zonal deformable mirror that controls the wavefront of a high average power visible laser beam used for isotope separation. The mirror corrects greater than five waves of astigmatism, power, or random second order aberrations to 1/20 wave rms. Sufficient resolution is achieved to correct third order aberrations as well. A monolithic glass substrate with dimensions 77 mm X 121 mm X 10 mm is used in this design. Twenty-five actuator attachment members are incorporated into the shape of the back side of the substrate. Piezoelectric translators (PZTs) attached in a rectangular array deform the continuous substrate to the proper conjugate shape. The PZTs are attached through flexures designed to be compressionally stiff and laterally soft. In this way the intended PZT displacement is transmitted efficiently to the substrate while isolating both the mirror and the PZTs from undesirable lateral loads. Mirror parameters were determined from elastic mechanical beam approximations. Finite element analysis was used to verify performance prior to prototyping. A Hartmann sensor controls the mirror in a closed loop adaptive system. The system description is covered in a companion paper. This paper describes the mirror design and presents performance data.