A conceptually simple method for producing a hologram of a computer-specified object is to illuminate the photosensitive recording plate with a reference wave and trace out the object distribution with a point of light moved by a computer-controlled scanning system. The principal drawback is the poor signal-to-noise ratio (SNR) of the reconstructed object, because of bias buildup in the recording process. Two methods for improving reconstruction SNR are discussed in this paper: (1) maximizing the contrast of each fringe or zone-plate pattern exposing the hologram, and (2) recording intermediate holograms of portions of the object, which are then reconstructed for use in recording a final hologram of higher signal-to-bias ratio.
William T. Rhodes,
"Hybrid Time- And Space-Integration Method For Computer Holography", Proc. SPIE 0437, Intl Conf on Computer-Generated Holography, (26 October 1983); doi: 10.1117/12.937135; https://doi.org/10.1117/12.937135