Matching of the wavefront corrector to the statistics of aberrations in the optical system can drastically improve the performance of adaptive optical system and reduce its price and complexity. Introduction Since adaptive optics was suggested by Babcock [1], a great number of wavefront correctors has been proposed, realized and used to improve the performance of adaptive optics in science, medicine, and industry. However, many applications of adaptive optics still belong to researchers.

In this article, we show a breadboard setup of a complete closed-loop adaptive optical system that can be used for educational purposes or as a test setup for deformable mirrors, wavefront sensors and control software. The complete AO system is built on a 45x30 cm breadboard and includes point source, aberration simulator (optional), deformable mirror and Shack-Hartmann WF sensor. {gallery count=0}aodemo/setup1{/gallery} Photo and schematic of the setup Laser diode, pinhole and the lens L1 form a collimated laser beam.

Direct control of Zernike modes is beneficial in feedforward control algorithms, and in optimization-based adaptive optics, such as laser intracavity AO, adaptive image sharpness control, smart PSF control in microscopy, optimal imaging through turbulence with stochastic optimization, etc. In all these cases the dynamic control of Zernike modes provides for very quick quasi-optimal convergence to the maximum value of the target function. Here we show a 15 mm 37-channel OKO Micromachined Membrane Deformable Mirror (MMDM) and 30 mm 37-channel Piezoelectric Deformable Mirror (PDM) operated by Zernike polynomials in feedforward control mode.

18-channel PDM has no actuators inside the active aperture. This makes it suitable for an excellent correction of low-order aberrations. The note presents interferometric images of the results of the generation with the 30-mm 18-channel PDM. The actuator layout of 19- and 18-channel PDM has been especially developped for correction of the low-order abberrations (see [1] for the theoretical background). In 18-channel version, the central actuator is absent (see Fig.1), and thus all actuators are outside the 20-mm active aperture.

_What is the maximum defocus correction I can get with your mirror? Is it possible to generate both negative and positive defocus? Which mirror, PDM or MMDM, do you advice me to use for correction of Z2,0? — _Here, at Flexible Optical, we receive quite often these questions. This short article explains the aspects of the generation/correction of the defocus aberration with MMDM and PDM and considers the factors limiting the amplitude of the correction with various types of mirrors.