  Ghost imaging is a developing imaging technique that employs random masks to
image a sample. Ghost projection utilizes ghost-imaging concepts to perform the
complementary procedure of projection of a desired image. The key idea
underpinning ghost projection is that any desired spatial distribution of
radiant exposure may be produced, up to an additive constant, by
spatially-uniformly illuminating a set of random masks in succession. We
explore three means of achieving ghost projection: (i) weighting each random
mask, namely selecting its exposure time, according to its correlation with a
desired image, (ii) selecting a subset of random masks according to their
correlation with a desired image, and (iii) numerically optimizing a projection
for a given set of random masks and desired image. The first two protocols are
analytically tractable and conceptually transparent. The third is more
efficient but less amenable to closed-form analytical expressions. A comparison
with existing image-projection techniques is drawn and possible applications
are discussed. These potential applications include: (i) a data projector for
matter and radiation fields for which no current data projectors exist, (ii) a
universal-mask approach to lithography, (iii) tomographic volumetric additive
manufacturing, and (iv) a ghost-projection photocopier.
