  In ghost imaging schemes information about an object is extracted by
measuring the correlation between a beam that passed the object and a reference
beam. We present a spatial averaging technique that substantially improves the
imaging bandwidth of such schemes, which implies that information about
high-frequency Fourier components can be observed in the reconstructed
diffraction pattern. In the many-photon regime the averaging can be done in
parallel and we show that this leads to a much faster convergence of the
correlations. We also consider the reconstruction of the object image, and
discuss the differences between a pixel-like detector and a bucket detector in
the object arm. Finally, it is shown how to non-locally make spatial filtering
of a reconstructed image. The results are presented using entangled beams
created by parametric down-conversion, but they are general and can be extended
also to the important case of using classically correlated thermal-like beams.
