Multidither Adaptive Algorithms

Abstract : Reduction of thermal blooming distortions has been studied as a function of the initial transmitter irradiance profile. The data, obtained by computer simulation of focused-beam propagation, indicate that the best way to increase the peak target irradiance is to make the aperture distribution as uniform as possible. This conclusion holds for Gaussian, truncated or apodized Gaussian, annular or circular beams, and for special 'hole-in-the-middle' laser modes. Two computer simulations have been developed. One code calculates thermal blooming correction with a full-servo simulation of a multi-dither COAT system. The second code models a multidither Zernike-polynomial COAT system (ZEP-COAT) with up to 13 polynomials. This code can be used with or without a simulation of a 37-element deformable mirror. Identical performance is obtained for linear propagation with the ZEP-COAT code and with a conventional multidither, outgoing-wave COAT (MOW-COAT) simulation code. A 37-element deformable mirror has been designed for use with the DARPA/RADC 18-channel, visible-wavelength multidither COAT system. The design and performance goals of this uncooled mirror are summarized.