Compensation for distortions of telescope's primary mirror by means of a volume dynamic hologram

We describe a number of experiments devoted to compensation for aberrations in the primary mirror of a telescope using a volume dynamic holography technique, where the writing and reading of the hologram are carried out independently. Three sets of experiments demonstrating holographic aberration correction have been performed. In all cases transmitting holograms were, formed in photorefractive crystals such as BSO and SBN. In experiments with a small diameter primary mirror the image is formed by a multicolor point-like object. The system includes an unit wich compensates for the hologram dispersion. The aberration correction of a six-segmented primary mirror of 150 nun in diameter is demonstrated in conditions where there is a pronounced difference in the wavelengths of the recording beams and that of the source observed (Delta lambda=0.12 mu m). The experiments on observation an extended object of continuous spectrum (Delta lambda=0.35 mu m) with a single primary mirror of 150 mm diameter have been also made. All these experiments indicate an efficient compensation for distortions of the primary mirror by the hologram.