A successful implementation is reported of a simple and rapid method of constructing computer generated holograms, by overprinting the standard line printer characters. The theoretical and practical limitations of computer generated holograms are discussed with reference to a number of optical and computational experiments reported here.

A new technique, called "speckle holography", is described and its successful simulation in the optical laboratory is reported. This technique is an extension of Labeyrie's speckle interferometry and it permits true images to be obtained through randomly fluctuating media. Comments are also made on Knox and Thompson's extension of speckle interferometry for which it is claimed that it is not necessary to use a holographic approach to obtain a true image. The relevance of this latter extension to future astronomical practice is assessed.